Investigating molecular basis of lambda-cyhalothrin resistance in an Anopheles funestus population from Senegal.

PubMed

Samb, Badara; Konate, Lassana; Irving, Helen; Riveron, Jacob M; Dia, Ibrahima; Faye, Ousmane; Wondji, Charles S

2016-08-12

Anopheles funestus is one of the major malaria vectors in tropical Africa, notably in Senegal. The highly anthropophilic and endophilic behaviours of this mosquito make it a good target for vector control operations through the use of insecticide treated nets, long-lasting insecticide nets and indoor residual spraying. However, little is known about patterns of resistance to insecticides and the underlying resistance mechanisms in field populations of this vector in Senegal. Here, we assessed the susceptibility status of An. funestus populations from Gankette Balla, located in northern Senegal and investigated the potential resistance mechanisms. WHO bioassays indicated that An. funestus is resistant to lambda-cyhalothrin 0.05 % (74.64 % mortality), DDT 4 % (83.36 % mortality) and deltamethrin 0.05 % (88.53 % mortality). Suspected resistance was observed to permethrin 0.75 % (91.19 % mortality), bendiocarb 0.1 % (94.13 % mortality) and dieldrin 4 % (96.41 % mortality). However, this population is fully susceptible to malathion 5 % (100 % mortality) and fenitrothion 1 % (100 % mortality). The microarray and qRT-PCR analysis indicated that the lambda-cyhalothrin resistance in Gankette Balla is conferred by metabolic resistance mechanisms under the probable control of cytochrome P450 genes among which CYP6M7 is the most overexpressed. The absence of overexpression of the P450 gene, CYP6P9a, indicates that the resistance mechanism in Senegal is different to that observed in southern Africa. This study represents the first report of pyrethroid and DDT resistance in An. funestus from Senegal and shows that resistance to insecticides is not only confined to An. gambiae as previously thought. Therefore, urgent action should be taken to manage the resistance in this species to ensure the continued effectiveness of malaria control.

Variations in household microclimate affect outdoor-biting behaviour of malaria vectors

PubMed Central

Ngowo, Halfan S.; Kaindoa, Emmanuel Wilson; Matthiopoulos, Jason; Ferguson, Heather M.; Okumu, Fredros O.

2017-01-01

Background: Mosquito behaviours including the degree to which they bite inside houses or outside is a crucial determinant of human exposure to malaria. Whilst seasonality in mosquito vector abundance is well documented, much less is known about the impact of climate on mosquito behaviour. We investigated how variations in household microclimate affect outdoor-biting by malaria vectors, Anopheles arabiensis and Anopheles funestus. Methods: Mosquitoes were sampled indoors and outdoors weekly using human landing catches at eight households in four villages in south-eastern Tanzania, resulting in 616 trap-nights over 12 months. Daily temperature, relative humidity and rainfall were recorded. Generalized additive mixed models (GAMMs) were used to test associations between mosquito abundance and the microclimatic conditions. Generalized linear mixed models (GLMMs) were used to investigate the influence of microclimatic conditions on the tendency of vectors to bite outdoors (proportion of outdoor biting). Results:  An. arabiensis abundance peaked during high rainfall months (February-May), whilst An. funestus density remained stable into the dry season (May-August) . Across the range of observed household temperatures, a rise of 1 ºC marginally increased nightly An. arabiensis abundance (~11%), but more prominently increased An. funestus abundance (~66%). The abundance of An. arabiensis and An. funestus showed strong positive associations with time-lagged rainfall (2-3 and 3-4 weeks before sampling). The degree of outdoor biting in An. arabiensis was significantly associated with the relative temperature difference between indoor and outdoor environments, with exophily increasing as temperature inside houses became relatively warmer. The exophily of An. funestus did not vary with temperature differences.   Conclusions: This study demonstrates that malaria vector An. arabiensis shifts the location of its biting from indoors to outdoors in association with relative differences in microclimatic conditions. These environmental impacts could give rise to seasonal variation in mosquito biting behaviour and degree of protection provided by indoor-based vector control strategies. PMID:29552642

Widespread Pyrethroid and DDT Resistance in the Major Malaria Vector Anopheles funestus in East Africa Is Driven by Metabolic Resistance Mechanisms

PubMed Central

Mulamba, Charles; Riveron, Jacob M.; Ibrahim, Sulaiman S.; Irving, Helen; Barnes, Kayla G.; Mukwaya, Louis G.; Birungi, Josephine; Wondji, Charles S.

2014-01-01

Background Establishing the extent, geographical distribution and mechanisms of insecticide resistance in malaria vectors is a prerequisite for resistance management. Here, we report a widespread distribution of insecticide resistance in the major malaria vector An. funestus across Uganda and western Kenya under the control of metabolic resistance mechanisms. Methodology/Principal Findings Female An. funestus collected throughout Uganda and western Kenya exhibited a Plasmodium infection rate between 4.2 to 10.4%. Widespread resistance against both type I (permethrin) and II (deltamethrin) pyrethroids and DDT was observed across Uganda and western Kenya. All populations remain highly susceptible to carbamate, organophosphate and dieldrin insecticides. Knockdown resistance plays no role in the pyrethroid and DDT resistance as no kdr mutation associated with resistance was detected despite the presence of a F1021C replacement. Additionally, no signature of selection was observed on the sodium channel gene. Synergist assays and qRT-PCR indicated that metabolic resistance plays a major role notably through elevated expression of cytochrome P450s. DDT resistance mechanisms differ from West Africa as the L119F-GSTe2 mutation only explains a small proportion of the genetic variance to DDT resistance. Conclusion The extensive distribution of pyrethroid and DDT resistance in East African An. funestus populations represents a challenge to the control of this vector. However, the observed carbamate and organophosphate susceptibility offers alternative solutions for resistance management. PMID:25333491

Desiccation tolerance as a function of age, sex, humidity and temperature in adults of the African malaria vectors Anopheles arabiensis and Anopheles funestus.

PubMed

Lyons, Candice L; Coetzee, Maureen; Terblanche, John S; Chown, Steven L

2014-11-01

Adult mosquito survival is strongly temperature and moisture dependent. Few studies have investigated the interacting effects of these variables on adult survival and how this differs among the sexes and with age, despite the importance of such information for population dynamic models. For these reasons, the desiccation tolerance of Anopheles arabiensis Patton and Anopheles funestus Giles males and females of three different ages was assessed under three combinations of temperature and humidity. Females were more desiccation tolerant than males, surviving for longer periods than males under all experimental conditions. In addition, younger adults were more tolerant of desiccation than older groups. Both species showed reduced water loss rate (WLR) as the primary mechanism by which they tolerate desiccation. Although A. arabiensis is often considered to be the more arid-adapted of the two species, it showed lower survival times and higher WLR than A. funestus. The current information could improve population dynamic models of these vectors, given that adult survival information for such models is relatively sparse. © 2014. Published by The Company of Biologists Ltd.

Nigeria Anopheles Vector Database: An Overview of 100 Years' Research

PubMed Central

Okorie, Patricia Nkem; McKenzie, F. Ellis; Ademowo, Olusegun George; Bockarie, Moses; Kelly-Hope, Louise

2011-01-01

Anopheles mosquitoes are important vectors of malaria and lymphatic filariasis (LF), which are major public health diseases in Nigeria. Malaria is caused by infection with a protozoan parasite of the genus Plasmodium and LF by the parasitic worm Wuchereria bancrofti. Updating our knowledge of the Anopheles species is vital in planning and implementing evidence based vector control programs. To present a comprehensive report on the spatial distribution and composition of these vectors, all published data available were collated into a database. Details recorded for each source were the locality, latitude/longitude, time/period of study, species, abundance, sampling/collection methods, morphological and molecular species identification methods, insecticide resistance status, including evidence of the kdr allele, and P. falciparum sporozoite rate and W. bancrofti microfilaria prevalence. This collation resulted in a total of 110 publications, encompassing 484,747 Anopheles mosquitoes in 632 spatially unique descriptions at 142 georeferenced locations being identified across Nigeria from 1900 to 2010. Overall, the highest number of vector species reported included An. gambiae complex (65.2%), An. funestus complex (17.3%), An. gambiae s.s. (6.5%). An. arabiensis (5.0%) and An. funestus s.s. (2.5%), with the molecular forms An. gambiae M and S identified at 120 locations. A variety of sampling/collection and species identification methods were used with an increase in molecular techniques in recent decades. Insecticide resistance to pyrethroids and organochlorines was found in the main Anopheles species across 45 locations. Presence of P. falciparum and W. bancrofti varied between species with the highest sporozoite rates found in An. gambiae s.s, An. funestus s.s. and An. moucheti, and the highest microfilaria prevalence in An. gambiae s.l., An. arabiensis, and An. gambiae s.s. This comprehensive geo-referenced database provides an essential baseline on Anopheles vectors and will be an important resource for malaria and LF vector control programmes in Nigeria. PMID:22162764

The Role of Oxidative Stress in the Longevity and Insecticide Resistance Phenotype of the Major Malaria Vectors Anopheles arabiensis and Anopheles funestus.

PubMed

Oliver, Shüné V; Brooke, Basil D

2016-01-01

Oxidative stress plays numerous biological roles, both functional and pathological. The role of oxidative stress in various epidemiologically relevant biological traits in Anopheles mosquitoes is not well established. In this study, the effects of oxidative stress on the longevity and insecticide resistance phenotype in the major malaria vector species An. arabiensis and An. funestus were examined. Responses to dietary copper sulphate and hydrogen peroxide were used as proxies for the oxidative stress phenotype by determining the effect of copper on longevity and hydrogen peroxide lethal dose. Glutathione peroxidase and catalase activities were determined colorimetrically. Oxidative burden was quantified as protein carbonyl content. Changes in insecticide resistance phenotype were monitored by WHO bioassay. Insecticide resistant individuals showed an increased capacity for coping with oxidative stress, mediated by increased glutathione peroxidase and catalase activity. This effect was observed in both species, as well as in laboratory strains and F1 individuals derived from wild-caught An. funestus mothers. Phenotypic capacity for coping with oxidative stress was greatest in strains with elevated Cytochrome P450 activity. Synergism of oxidative stress defence enzymes by dietary supplementation with haematin, 3-Amino-1, 2, 4-triazole and Sodium diethyldithiocarbamate significantly increased pyrethroid-induced mortality in An. arabiensis and An. funestus. It is therefore concluded that defence against oxidative stress underlies the augmentation of the insecticide resistance phenotype associated with multiple blood-feeding. This is because multiple blood-feeding ultimately leads to a reduction of oxidative stress in insecticide resistant females, and also reduces the oxidative burden induced by DDT and pyrethroids, by inducing increased glutathione peroxidase activity. This study highlights the importance of oxidative stress in the longevity and insecticide resistance phenotype in malaria vectors.

Restriction to gene flow is associated with changes in the molecular basis of pyrethroid resistance in the malaria vector Anopheles funestus

PubMed Central

Barnes, Kayla G.; Irving, Helen; Chiumia, Martin; Mzilahowa, Themba; Coleman, Michael; Hemingway, Janet; Wondji, Charles S.

2017-01-01

Resistance to pyrethroids, the sole insecticide class recommended for treating bed nets, threatens the control of major malaria vectors, including Anopheles funestus. Effective management of resistance requires an understanding of the dynamics and mechanisms driving resistance. Here, using genome-wide transcription and genetic diversity analyses, we show that a shift in the molecular basis of pyrethroid resistance in southern African populations of this species is associated with a restricted gene flow. Across the most highly endemic and densely populated regions in Malawi, An. funestus is resistant to pyrethroids, carbamates, and organochlorides. Genome-wide microarray-based transcription analysis identified overexpression of cytochrome P450 genes as the main mechanism driving this resistance. The most up-regulated genes include cytochrome P450s (CYP) CYP6P9a, CYP6P9b and CYP6M7. However, a significant shift in the overexpression profile of these genes was detected across a south/north transect, with CYP6P9a and CYP6P9b more highly overexpressed in the southern resistance front and CYP6M7 predominant in the northern front. A genome-wide genetic structure analysis of southern African populations of An. funestus from Zambia, Malawi, and Mozambique revealed a restriction of gene flow between populations, in line with the geographical variation observed in the transcriptomic analysis. Genetic polymorphism analysis of the three key resistance genes, CYP6P9a, CYP6P9b, and CYP6M7, support barriers to gene flow that are shaping the underlying molecular basis of pyrethroid resistance across southern Africa. This barrier to gene flow is likely to impact the design and implementation of resistance management strategies in the region. PMID:28003461

Insecticide resistance status of three malaria vectors, Anopheles gambiae (s.l.), An. funestus and An. mascarensis, from the south, central and east coasts of Madagascar.

PubMed

Rakotoson, Jean-Desire; Fornadel, Christen M; Belemvire, Allison; Norris, Laura C; George, Kristen; Caranci, Angela; Lucas, Bradford; Dengela, Dereje

2017-08-23

Insecticide-based vector control, which comprises use of insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS), is the key method to malaria control in Madagascar. However, its effectiveness is threatened as vectors become resistant to insecticides. This study investigated the resistance status of malaria vectors in Madagascar to various insecticides recommended for use in ITNs and/or IRS. WHO tube and CDC bottle bioassays were performed on populations of Anopheles gambiae (s.l.), An. funestus and An. mascarensis. Adult female An. gambiae (s.l.) mosquitoes reared from field-collected larvae and pupae were tested for their resistance to DDT, permethrin, deltamethrin, alpha-cypermethrin, lambda-cyhalothrin, bendiocarb and pirimiphos-methyl. Resting An. funestus and An. mascarensis female mosquitoes collected from unsprayed surfaces were tested against permethrin, deltamethrin and pirimiphos-methyl. The effect on insecticide resistance of pre-exposure to the synergists piperonyl-butoxide (PBO) and S,S,S-tributyl phosphorotrithioate (DEF) also was assessed. Molecular analyses were done to identify species and determine the presence of knock-down resistance (kdr) and acetylcholinesterase resistance (ace-1 R ) gene mutations. Anopheles funestus and An. mascarensis were fully susceptible to permethrin, deltamethrin and pirimiphos-methyl. Anopheles gambiae (s.l.) was fully susceptible to bendiocarb and pirimiphos-methyl. Among the 17 An. gambiae (s.l.) populations tested for deltamethrin, no confirmed resistance was recorded, but suspected resistance was observed in two sites. Anopheles gambiae (s.l.) was resistant to permethrin in four out of 18 sites (mortality 68-89%) and to alpha-cypermethrin (89% mortality) and lambda-cyhalothrin (80% and 85%) in one of 17 sites, using one or both assay methods. Pre-exposure to PBO restored full susceptibility to all pyrethroids tested except in one site where only partial restoration to permethrin was observed. DEF fully suppressed resistance to deltamethrin and alpha-cypermethrin, while it partially restored susceptibility to permethrin in two of the three sites. Molecular analysis data suggest absence of kdr and ace-1 R gene mutations. This study suggests involvement of detoxifying enzymes in the phenotypic resistance of An. gambiae (s.l.) to pyrethroids. The absence of resistance in An. funestus and An. mascarensis to pirimiphos-methyl and pyrethroids and in An. gambiae (s.l.) to carbamates and organophosphates presents greater opportunity for managing resistance in Madagascar.

Impact of pyrethroid resistance on operational malaria control in Malawi

PubMed Central

Wondji, Charles S.; Coleman, Michael; Kleinschmidt, Immo; Mzilahowa, Themba; Irving, Helen; Ndula, Miranda; Rehman, Andrea; Morgan, John; Barnes, Kayla G.; Hemingway, Janet

2012-01-01

The impact of insecticide resistance on insect-borne disease programs is difficult to quantify. The possibility of eliminating malaria in high-transmission settings is heavily dependent on effective vector control reducing disease transmission rates. Pyrethroids are the dominant insecticides used for malaria control, with few options for their replacement. Their failure will adversely affect our ability to control malaria. Pyrethroid resistance has been selected in Malawi over the last 3 y in the two major malaria vectors Anopheles gambiae and Anopheles funestus, with a higher frequency of resistance in the latter. The resistance in An. funestus is metabolically based and involves the up-regulation of two duplicated P450s. The same genes confer resistance in Mozambican An. funestus, although the levels of up-regulation differ. The selection of resistance over 3 y has not increased malaria transmission, as judged by annual point prevalence surveys in 1- to 4-y-old children. This is true in areas with long-lasting insecticide-treated nets (LLINs) alone or LLINs plus pyrethroid-based insecticide residual spraying (IRS). However, in districts where IRS was scaled up, it did not produce the expected decrease in malaria prevalence. As resistance increases in frequency from this low initial level, there is the potential for vector population numbers to increase with a concomitant negative impact on control efficacy. This should be monitored carefully as part of the operational activities in country. PMID:23118337

Epidemic O'Nyong-Nyong fever in southcentral Uganda, 1996-1997: entomologic studies in Bbaale village, Rakai District.

PubMed

Lutwama, J J; Kayondo, J; Savage, H M; Burkot, T R; Miller, B R

1999-07-01

Entomologic studies were conducted between January 27 and February 2, 1997, in Bbaale village in southcentral Uganda during an o'nyong-nyong (ONN) virus epidemic, which began in mid 1996 and continued into 1997. The objectives were to confirm the role of anophelines in ONN virus transmission and to examine other mosquito species as epidemic vectors of ONN virus. Of 10,050 mosquitoes collected using light traps and pyrethrum knockdown sprays, Anopheles (Cellia) funestus Giles was presumed to be the principal vector because it was the most abundant mosquito species from which a strain of ONN virus was isolated. This virus was isolated for the first time from a culicine species, Mansonia (Mansonioides) uniformis Theobald. Bwamba virus and Nyando virus were also isolated from An. funestus.

Activity of Ocimum basilicum, Ocimum canum, and Cymbopogon citratus essential oils against Plasmodium falciparum and mature-stage larvae of Anopheles funestus s.s.

PubMed

Akono Ntonga, Patrick; Baldovini, Nicolas; Mouray, Elisabeth; Mambu, Lengo; Belong, Philippe; Grellier, Philippe

2014-01-01

The biological activities of essential oils from three plants grown in Cameroon: Ocimum basilicum, Ocimum canum, and Cymbopogon citratus were tested against Plasmodium falciparum and mature-stage larvae of Anopheles funestus. Gas chromatography and gas chromatography - mass spectrometry analyses showed that the main compounds are geranial, 1,8-cineole and linalool in C. citratus, O. canum and O. basilicum, respectively. Larvicidal tests carried out according to the protocol recommended by the World Health Organization showed that the essential oil of leaves of C. citratus is the most active against larvae of An. funestus (LC50 values = 35.5 ppm and 34.6 ppm, respectively, for larval stages III and IV after 6 h of exposure). Besides, the in vitro anti-plasmodial activity evaluated by the radioisotopic method showed that the C. citratus oil is the most active against P. falciparum, with an IC50 value of 4.2 ± 0.5 μg/mL compared with O. canum (20.6 ± 3.4 μg/mL) and O. basilicum (21 ± 4.6 μg/mL). These essential oils can be recommended for the development of natural biocides for fighting the larvae of malaria vectors and for the isolation of natural products with anti-malarial activity. © P. Akono Ntonga et al., published by EDP Sciences, 2014.

Activity of Ocimum basilicum, Ocimum canum, and Cymbopogon citratus essential oils against Plasmodium falciparum and mature-stage larvae of Anopheles funestus s.s.

PubMed Central

Akono Ntonga, Patrick; Baldovini, Nicolas; Mouray, Elisabeth; Mambu, Lengo; Belong, Philippe; Grellier, Philippe

2014-01-01

The biological activities of essential oils from three plants grown in Cameroon: Ocimum basilicum, Ocimum canum, and Cymbopogon citratus were tested against Plasmodium falciparum and mature-stage larvae of Anopheles funestus. Gas chromatography and gas chromatography – mass spectrometry analyses showed that the main compounds are geranial, 1,8-cineole and linalool in C. citratus, O. canum and O. basilicum, respectively. Larvicidal tests carried out according to the protocol recommended by the World Health Organization showed that the essential oil of leaves of C. citratus is the most active against larvae of An. funestus (LC50 values = 35.5 ppm and 34.6 ppm, respectively, for larval stages III and IV after 6 h of exposure). Besides, the in vitro anti-plasmodial activity evaluated by the radioisotopic method showed that the C. citratus oil is the most active against P. falciparum, with an IC50 value of 4.2 ± 0.5 μg/mL compared with O. canum (20.6 ± 3.4 μg/mL) and O. basilicum (21 ± 4.6 μg/mL). These essential oils can be recommended for the development of natural biocides for fighting the larvae of malaria vectors and for the isolation of natural products with anti-malarial activity. PMID:24995776

Modeling Malaria Vector Distribution under Climate Change Scenarios in Kenya

NASA Astrophysics Data System (ADS)

Ngaina, J. N.

2017-12-01

Projecting the distribution of malaria vectors under climate change is essential for planning integrated vector control strategies for sustaining elimination and preventing reintroduction of malaria. However, in Kenya, little knowledge exists on the possible effects of climate change on malaria vectors. Here we assess the potential impact of future climate change on locally dominant Anopheles vectors including Anopheles gambiae, Anopheles arabiensis, Anopheles merus, Anopheles funestus, Anopheles pharoensis and Anopheles nili. Environmental data (Climate, Land cover and elevation) and primary empirical geo-located species-presence data were identified. The principle of maximum entropy (Maxent) was used to model the species' potential distribution area under paleoclimate, current and future climates. The Maxent model was highly accurate with a statistically significant AUC value. Simulation-based estimates suggest that the environmentally suitable area (ESA) for Anopheles gambiae, An. arabiensis, An. funestus and An. pharoensis would increase under all two scenarios for mid-century (2016-2045), but decrease for end century (2071-2100). An increase in ESA of An. Funestus was estimated under medium stabilizing (RCP4.5) and very heavy (RCP8.5) emission scenarios for mid-century. Our findings can be applied in various ways such as the identification of additional localities where Anopheles malaria vectors may already exist, but has not yet been detected and the recognition of localities where it is likely to spread to. Moreover, it will help guide future sampling location decisions, help with the planning of vector control suites nationally and encourage broader research inquiry into vector species niche modeling

Development and evaluation of mosquito-electrocuting traps as alternatives to the human landing catch technique for sampling host-seeking malaria vectors.

PubMed

Maliti, Deodatus V; Govella, Nicodem J; Killeen, Gerry F; Mirzai, Nosrat; Johnson, Paul C D; Kreppel, Katharina; Ferguson, Heather M

2015-12-15

The human landing catch (HLC) is the gold standard method for sampling host-seeking malaria vectors. However, the HLC is ethically questionable because it requires exposure of humans to potentially infectious mosquito bites. Two exposure-free methods for sampling host-seeking mosquitoes were evaluated using electrocuting surfaces as potential replacements for HLC: (1) a previously evaluated, commercially available electrocuting grid (CA-EG) designed for killing flies, and (2) a custom-made mosquito electrocuting trap (MET) designed to kill African malaria vectors. The MET and the CA-EG were evaluated relative to the HLC in a Latin Square experiment conducted in the Kilombero Valley, Tanzania. The sampling consistency of the traps across the night and at varying mosquito densities was investigated. Estimates of the proportion of mosquitoes caught indoors (P(i)), proportion of human exposure occurring indoors (π(i)), and proportion of mosquitoes caught when most people are likely to be indoors (P(fl)) were compared for all traps. Whereas the CA-EG performed poorly (<10% of catch of HLC), sampling efficiency of the MET for sampling Anopheles funestus s.l. was indistinguishable from HLC indoors and outdoors. For Anopheles gambiae s.l., sampling sensitivity of MET was 20.9% (95% CI 10.3-42.2) indoors and 58.5% (95% CI 32.2-106.2) outdoors relative to HLC. There was no evidence of density-dependent sampling by the MET or CA-EG. Similar estimates of P(i) were obtained for An. gambiae s.l. and An. funestus s.l. from all trapping methods. The proportion of mosquitoes caught when people are usually indoors (P(fl)) was underestimated by the CA-EG and MET for An. gambiae s.l., but similar to the HLC for An. funestus. Estimates of the proportion of human exposure occurring indoors (π(i)) obtained from the CA-EG and MET were similar to the HLC for An. gambiae s.l., but overestimated for An. funestus. The MET showed promise as an outdoor sampling tool for malaria vectors where it achieved >50% sampling sensitivity relative to the HLC. The CA-EG had poor sampling sensitivity outdoors and inside. With further modification, the MET could provide an efficient and safer alternative to the HLC for the surveillance of mosquito vectors outdoors.

Household-level and surrounding peri-domestic environmental characteristics associated with malaria vectors Anopheles arabiensis and Anopheles funestus along an urban-rural continuum in Blantyre, Malawi.

PubMed

Dear, Nicole F; Kadangwe, Chifundo; Mzilahowa, Themba; Bauleni, Andy; Mathanga, Don P; Duster, Chifundo; Walker, Edward D; Wilson, Mark L

2018-06-08

Malaria is increasing in some recently urbanized areas that historically were considered lower risk. Understanding what drives urban transmission is hampered by inconsistencies in how "urban" contexts are defined. A dichotomized "urban-rural" approach, based on political boundaries may misclassify environments or fail to capture local drivers of risk. Small-scale agriculture in urban or peri-urban settings has been shown to be a major risk determinant. Household-level Anopheles abundance patterns in and around Malawi's commercial capital of Blantyre (~ 1.9 M pop.) were analysed. Clusters (N = 64) of five houses each located at 2.5 km intervals along eight transects radiating out from Blantyre city centre were sampled during rainy and dry seasons of 2015 and 2016. Mosquito densities were measured inside houses using aspirators to sample resting mosquitoes, and un-baited CDC light traps to sample host seeking mosquitoes. Of 38,895 mosquitoes captured, 91% were female and 87% were Culex spp. Anopheles females (N = 5058) were primarily captured in light traps (97%). Anopheles abundance was greater during rainy seasons. Anopheles funestus was more abundant than Anopheles arabiensis, but both were found on all transects, and had similar associations with environmental risk factors. Anopheles funestus and An. arabiensis females significantly increased with distance from the urban centre, but this trend was not consistent across all transects. Presence of small-scale agriculture was predictive of greater Anopheles spp. abundance, even after controlling for urbanicity, number of nets per person, number of under-5-year olds, years of education, and season. This study revealed how small-scale agriculture along a rural-to-urban transition was associated with An. arabiensis and An. funestus indoor abundances, and that indoor Anopheles density can be high within Blantyre city limits, particularly where agriculture is present. Typical rural areas with lower house density and greater distance from urban centres reflected landscapes more suitable for Anopheles reproduction and house invasion. However, similar characteristics and elevated Anopheles abundances were also found around some houses within the city limits. Thus, dichotomous designations of "urban" or "rural" can obscure important heterogeneity in the landscape of Plasmodium transmission, suggesting the need for more nuanced assessment of urban malaria risk and prevention efforts.

Microdam Impoundments Provide Suitable Habitat for Larvae of Malaria Vectors: An Observational Study in Western Kenya.

PubMed

McCann, Robert S; Gimnig, John E; Bayoh, M Nabie; Ombok, Maurice; Walker, Edward D

2018-05-04

Impoundments formed by microdams in rural areas of Africa are important sources of water for people, but they provide potential larval habitats for Anopheles (Diptera: Culicidae) mosquitoes that are vectors of malaria. To study this association, the perimeters of 31 microdam impoundments in western Kenya were sampled for Anopheles larvae in three zones (patches of floating and emergent vegetation, shorelines of open water, and aggregations of cattle hoofprints) across dry and rainy seasons. Of 3,169 larvae collected, most (86.8%) were collected in the rainy season. Of 2,403 larvae successfully reared to fourth instar or adult, nine species were identified; most (80.2%) were Anopheles arabiensis Patton, sampled from hoofprint zones in the rainy season. Other species collected were Anopheles coustani Laveran, Anopheles gambiae s.s. Giles, Anopheles funestus Giles, and Anopheles rivulorum Leeson, Anopheles pharoensis Theobald, Anopheles squamosus Theobald, Anopheles rufipes (Gough), and Anopheles ardensis (Theobald). Larvae of An. funestus were uncommon (1.5%) in both dry and rainy seasons and were confined to vegetated zones, suggesting that microdam impoundments are not primary habitats for this important vector species, although microdams may provide a dry season refuge habitat for malaria vectors, contributing to population persistence through the dry season. In this study, microdam impoundments clearly provided habitat for the malaria vector An. arabiensis in the rainy season, most of which was within the shallow apron side of the impoundments where people brought cattle for watering, resulting in compacted soil with aggregations of water-filled hoofprints. This observation suggests a potential conflict between public health concerns about malaria and people's need for stable and reliable sources of water.

Molasses as a source of carbon dioxide for attracting the malaria mosquitoes Anopheles gambiae and Anopheles funestus

PubMed Central

2014-01-01

Background Most odour baits for haematophagous arthropods contain carbon dioxide (CO2). The CO2 is sourced artificially from the fermentation of refined sugar (sucrose), dry ice, pressurized gas cylinders or propane. These sources of CO2 are neither cost-effective nor sustainable for use in remote areas of sub-Saharan Africa. In this study, molasses was evaluated as a potential substrate for producing CO2 used as bait for malaria mosquitoes. Methods The attraction of laboratory-reared and wild Anopheles gambiae complex mosquitoes to CO2 generated from yeast-fermentation of molasses was assessed under semi-field and field conditions in western Kenya. In the field, responses of wild Anopheles funestus were also assessed. Attraction of the mosquitoes to a synthetic mosquito attractant, Mbita blend (comprising ammonia, L-lactic acid, tetradecanoic acid and 3-methyl-1-butanol) when augmented with CO2 generated from yeast fermentation of either molasses or sucrose was also investigated. Results In semi-field, the release rate of CO2 and proportion of An. gambiae mosquitoes attracted increased in tandem with an increase in the quantity of yeast-fermented molasses up to an optimal ratio of molasses and dry yeast. More An. gambiae mosquitoes were attracted to a combination of the Mbita blend plus CO2 produced from fermenting molasses than the Mbita blend plus CO2 from yeast-fermented sucrose. In the field, significantly more female An. gambiae sensu lato mosquitoes were attracted to the Mbita blend augmented with CO2 produced by fermenting 500 g of molasses compared to 250 g of sucrose or 250 g of molasses. Similarly, significantly more An. funestus, Culex and other anopheline mosquito species were attracted to the Mbita blend augmented with CO2 produced from fermenting molasses than the Mbita blend with CO2 produced from sucrose. Augmenting the Mbita blend with CO2 produced from molasses was associated with high catches of blood-fed An. gambiae s.l. and An. funestus mosquitoes. Conclusion Molasses is a suitable ingredient for the replacement of sucrose as a substrate for the production of CO2 for sampling of African malaria vectors and other mosquito species. The finding of blood-fed malaria vectors in traps baited with the Mbita blend and CO2 derived from molasses provides a unique opportunity for the study of host-vector interactions. PMID:24767543

Genome-Wide Transcription and Functional Analyses Reveal Heterogeneous Molecular Mechanisms Driving Pyrethroids Resistance in the Major Malaria Vector Anopheles funestus Across Africa

PubMed Central

Riveron, Jacob M.; Ibrahim, Sulaiman S.; Mulamba, Charles; Djouaka, Rousseau; Irving, Helen; Wondji, Murielle J.; Ishak, Intan H.; Wondji, Charles S.

2017-01-01

Pyrethroid resistance in malaria vector, An. funestus is increasingly reported across Africa, threatening the sustainability of pyrethroid-based control interventions, including long lasting insecticidal nets (LLINs). Managing this problem requires understanding of the molecular basis of the resistance from different regions of the continent, to establish whether it is being driven by a single or independent selective events. Here, using a genome-wide transcription profiling of pyrethroid resistant populations from southern (Malawi), East (Uganda), and West Africa (Benin), we investigated the molecular basis of resistance, revealing strong differences between the different African regions. The duplicated cytochrome P450 genes (CYP6P9a and CYP6P9b) which were highly overexpressed in southern Africa are not the most upregulated in other regions, where other genes are more overexpressed, including GSTe2 in West (Benin) and CYP9K1 in East (Uganda). The lack of directional selection on both CYP6P9a and CYP6P9b in Uganda in contrast to southern Africa further supports the limited role of these genes outside southern Africa. However, other genes such as the P450 CYP9J11 are commonly overexpressed in all countries across Africa. Here, CYP9J11 is functionally characterized and shown to confer resistance to pyrethroids and moderate cross-resistance to carbamates (bendiocarb). The consistent overexpression of GSTe2 in Benin is coupled with a role of allelic variation at this gene as GAL4-UAS transgenic expression in Drosophila flies showed that the resistant 119F allele is highly efficient in conferring both DDT and permethrin resistance than the L119. The heterogeneity in the molecular basis of resistance and cross-resistance to insecticides in An. funestus populations throughout sub-Saharan African should be taken into account in designing resistance management strategies. PMID:28428243

Review of the evolution of insecticide resistance in main malaria vectors in Cameroon from 1990 to 2017.

PubMed

Antonio-Nkondjio, Christophe; Sonhafouo-Chiana, N; Ngadjeu, C S; Doumbe-Belisse, P; Talipouo, A; Djamouko-Djonkam, L; Kopya, E; Bamou, R; Awono-Ambene, P; Wondji, Charles S

2017-10-10

Malaria remains a major public health threat in Cameroon and disease prevention is facing strong challenges due to the rapid expansion of insecticide resistance in vector populations. The present review presents an overview of published data on insecticide resistance in the main malaria vectors in Cameroon to assist in the elaboration of future and sustainable resistance management strategies. A systematic search on mosquito susceptibility to insecticides and insecticide resistance in malaria vectors in Cameroon was conducted using online bibliographic databases including PubMed, Google and Google Scholar. From each peer-reviewed paper, information on the year of the study, mosquito species, susceptibility levels, location, insecticides, data source and resistance mechanisms were extracted and inserted in a Microsoft Excel datasheet. The data collected were then analysed for assessing insecticide resistance evolution. Thirty-three scientific publications were selected for the analysis. The rapid evolution of insecticide resistance across the country was reported from 2000 onward. Insecticide resistance was highly prevalent in both An. gambiae (s.l.) and An. funestus. DDT, permethrin, deltamethrin and bendiocarb appeared as the most affected compounds by resistance. From 2000 to 2017 a steady increase in the prevalence of kdr allele frequency was noted in almost all sites in An. gambiae (s.l.), with the L1014F kdr allele being the most prevalent. Several detoxification genes (particularly P450 monooxygenase) were associated with DDT, pyrethroids and bendiocarb resistance. In An. funestus, resistance to DDT and pyrethroids was mainly attributed to the 119F-GSTe2 metabolic resistance marker and over-expression of P450 genes whereas the 296S-RDL mutation was detected in dieldrin-resistant An. funestus. The review provides an update of insecticide resistance status in malaria vector populations in Cameroon and stresses the need for further actions to reinforce malaria control strategies in the coming years.

Optimized Pan-species and Speciation Duplex Real-time PCR Assays for Plasmodium Parasites Detection in Malaria Vectors

PubMed Central

Sandeu, Maurice Marcel; Moussiliou, Azizath; Moiroux, Nicolas; Padonou, Gilles G.; Massougbodji, Achille; Corbel, Vincent; Tuikue Ndam, Nicaise

2012-01-01

Background An accurate method for detecting malaria parasites in the mosquito’s vector remains an essential component in the vector control. The Enzyme linked immunosorbent assay specific for circumsporozoite protein (ELISA-CSP) is the gold standard method for the detection of malaria parasites in the vector even if it presents some limitations. Here, we optimized multiplex real-time PCR assays to accurately detect minor populations in mixed infection with multiple Plasmodium species in the African malaria vectors Anopheles gambiae and Anopheles funestus. Methods Complementary TaqMan-based real-time PCR assays that detect Plasmodium species using specific primers and probes were first evaluated on artificial mixtures of different targets inserted in plasmid constructs. The assays were further validated in comparison with the ELISA-CSP on 200 field caught Anopheles gambiae and Anopheles funestus mosquitoes collected in two localities in southern Benin. Results The validation of the duplex real-time PCR assays on the plasmid mixtures demonstrated robust specificity and sensitivity for detecting distinct targets. Using a panel of mosquito specimen, the real-time PCR showed a relatively high sensitivity (88.6%) and specificity (98%), compared to ELISA-CSP as the referent standard. The agreement between both methods was “excellent” (κ = 0.8, P<0.05). The relative quantification of Plasmodium DNA between the two Anopheles species analyzed showed no significant difference (P = 0, 2). All infected mosquito samples contained Plasmodium falciparum DNA and mixed infections with P. malariae and/or P. ovale were observed in 18.6% and 13.6% of An. gambiae and An. funestus respectively. Plasmodium vivax was found in none of the mosquito samples analyzed. Conclusion This study presents an optimized method for detecting the four Plasmodium species in the African malaria vectors. The study highlights substantial discordance with traditional ELISA-CSP pointing out the utility of employing an accurate molecular diagnostic tool for detecting malaria parasites in field mosquito populations. PMID:23285168

Genome-Wide Transcription and Functional Analyses Reveal Heterogeneous Molecular Mechanisms Driving Pyrethroids Resistance in the Major Malaria Vector Anopheles funestus Across Africa.

PubMed

Riveron, Jacob M; Ibrahim, Sulaiman S; Mulamba, Charles; Djouaka, Rousseau; Irving, Helen; Wondji, Murielle J; Ishak, Intan H; Wondji, Charles S

2017-06-07

Pyrethroid resistance in malaria vector, An. funestus is increasingly reported across Africa, threatening the sustainability of pyrethroid-based control interventions, including long lasting insecticidal nets (LLINs). Managing this problem requires understanding of the molecular basis of the resistance from different regions of the continent, to establish whether it is being driven by a single or independent selective events. Here, using a genome-wide transcription profiling of pyrethroid resistant populations from southern (Malawi), East (Uganda), and West Africa (Benin), we investigated the molecular basis of resistance, revealing strong differences between the different African regions. The duplicated cytochrome P450 genes ( CYP6P9a and CYP6P9b ) which were highly overexpressed in southern Africa are not the most upregulated in other regions, where other genes are more overexpressed, including GSTe2 in West (Benin) and CYP9K1 in East (Uganda). The lack of directional selection on both CYP6P9a and CYP6P9b in Uganda in contrast to southern Africa further supports the limited role of these genes outside southern Africa. However, other genes such as the P450 CYP9J11 are commonly overexpressed in all countries across Africa. Here, CYP9J11 is functionally characterized and shown to confer resistance to pyrethroids and moderate cross-resistance to carbamates (bendiocarb). The consistent overexpression of GSTe2 in Benin is coupled with a role of allelic variation at this gene as GAL4-UAS transgenic expression in Drosophila flies showed that the resistant 119F allele is highly efficient in conferring both DDT and permethrin resistance than the L119. The heterogeneity in the molecular basis of resistance and cross-resistance to insecticides in An. funestus populations throughout sub-Saharan African should be taken into account in designing resistance management strategies. Copyright © 2017 Riveron et al.

Spatial and temporal heterogeneity of Anopheles mosquitoes and Plasmodium falciparum transmission along the Kenyan coast.

PubMed

Mbogo, Charles M; Mwangangi, Joseph M; Nzovu, Joseph; Gu, Weidong; Yan, Guiyan; Gunter, James T; Swalm, Chris; Keating, Joseph; Regens, James L; Shililu, Josephat I; Githure, John I; Beier, John C

2003-06-01

The seasonal dynamics and spatial distributions of Anopheles mosquitoes and Plasmodium falciparum parasites were studied for one year at 30 villages in Malindi, Kilifi, and Kwale Districts along the coast of Kenya. Anopheline mosquitoes were sampled inside houses at each site once every two months and malaria parasite prevalence in local school children was determined at the end of the entomologic survey. A total of 5,476 Anopheles gambiae s.l. and 3,461 An. funestus were collected. Species in the An. gambiae complex, identified by a polymerase chain reaction, included 81.9% An. gambiae s.s., 12.8% An. arabiensis, and 5.3% An. merus. Anopheles gambiae s.s. contributed most to the transmission of P. falciparum along the coast as a whole, while An. funestus accounted for more than 50% of all transmission in Kwale District. Large spatial heterogeneity of transmission intensity (< 1 up to 120 infective bites per person per year) resulted in correspondingly large and significantly related variations in parasite prevalence (range = 38-83%). Thirty-two percent of the sites (7 of 22 sites) with malaria prevalences ranging from 38% to 70% had annual entomologic inoculation rates (EIR) less than five infective bites per person per year. Anopheles gambiae s.l. and An. funestus densities in Kwale were not significantly influenced by rainfall. However, both were positively correlated with rainfall one and three months previously in Malindi and Kilifi Districts, respectively. These unexpected variations in the relationship between mosquito populations and rainfall suggest environmental heterogeneity in the predominant aquatic habitats in each district. One important conclusion is that the highly non-linear relationship between EIRs and prevalence indicates that the consistent pattern of high prevalence might be governed by substantial variation in transmission intensity measured by entomologic surveys. The field-based estimate of entomologic parameters on a district level does not provide a sensitive indicator of transmission intensity in this study.

Impact of insecticide-treated bed nets on malaria transmission indices on the south coast of Kenya

PubMed Central

2011-01-01

Background Besides significantly reducing malaria vector densities, prolonged usage of bed nets has been linked to decline of Anopheles gambiae s.s. relative to Anopheles arabiensis, changes in host feeding preference of malaria vectors, and behavioural shifts to exophagy (outdoor biting) for the two important malaria vectors in Africa, An. gambiae s.l. and Anopheles funestus. In southern coastal Kenya, bed net use was negligible in 1997-1998 when Anopheles funestus and An. gambiae s.s. were the primary malaria vectors, with An. arabiensis and Anopheles merus playing a secondary role. Since 2001, bed net use has increased progressively and reached high levels by 2009-2010 with corresponding decline in malaria transmission. Methods To evaluate the impact of the substantial increase in household bed net use within this area on vector density, vector composition, and human-vector contact, indoor and outdoor resting mosquitoes were collected in the same region during 2009-2010 using pyrethrum spray catches and clay pots for indoor and outdoor collections respectively. Information on bed net use per sleeping spaces and factors influencing mosquito density were determined in the same houses using Poisson regression analysis. Species distribution was determined, and number of mosquitoes per house, human-biting rates (HBR), and entomological inoculation rate (EIR) were compared to those reported for the same area during 1997-1998, when bed net coverage had been minimal. Results Compared to 1997-1998, a significant decline in the relative proportion of An. gambiae s.s. among collected mosquitoes was noted, coupled with a proportionate increase of An. arabiensis. Following > 5 years of 60-86% coverage with bed nets, the density, human biting rate and EIR of indoor resting mosquitoes were reduced by more than 92% for An. funestus and by 75% for An. gambiae s.l. In addition, the host feeding choice of both vectors shifted more toward non-human vertebrates. Besides bed net use, malaria vector abundance was also influenced by type of house construction and according to whether one sleeps on a bed or a mat (both of these are associated with household wealth). Mosquito density was positively associated with presence of domestic animals. Conclusions These entomological indices indicate a much reduced human biting rate and a diminishing role of An. gambiae s.s. in malaria transmission following high bed net coverage. While increasing bed net coverage beyond the current levels may not significantly reduce the transmission potential of An. arabiensis, it is anticipated that increasing or at least sustaining high bed net coverage will result in a diminished role for An. funestus in malaria transmission. PMID:22165904

Malaria vector composition and insecticide susceptibility status in Guinea Conakry, West Africa.

PubMed

Vezenegho, S B; Brooke, B D; Hunt, R H; Coetzee, M; Koekemoer, L L

2009-12-01

This study provides data on malaria vector species composition and insecticide susceptibility status from three localities in Guinea Conakry. A total of 497 mosquitoes were collected resting indoors and morphologically identified as belonging to the Anopheles gambiae complex. The majority of these were An. gambiae s.s. (99.6%), but a small percentage (0.4%) were identified as Anopheles arabiensis. Thirty-four Anopheles funestus s.s. were also collected. The molecular S form of An. gambiae s.s. was predominant over the M form in Siguiri (95%) and Boffa (97.4%), whereas at Mt Nimba the M form was more abundant (61.4%) than the S form (38.1%). One hybrid M/S specimen was recorded from Mt Nimba. Siguiri populations showed high levels of resistance to DDT, dieldrin and bendiocarb. Anopheles gambiae from Boffa were largely susceptible to the insecticides tested. At Mt Nimba, resistance to DDT and bendicocarb was detected. Biochemical enzyme analysis showed that an altered acetylcholinesterase is operating in the field at low levels. The frequency of the 1014F kdr allele in the An. gambiae S form was 0.24 at Siguiri and 0.14 at Mt Nimba. A single RR specimen was found in the M form. The heterogeneity in species composition and resistance profiles between sites requires vector control interventions to be tailored to each site based on the data collected from ongoing monitoring and surveillance.

Impact of permethrin-treated bed nets on entomologic indices in an area of intense year-round malaria transmission.

PubMed

Gimnig, John E; Vulule, John M; Lo, Terrence Q; Kamau, Luna; Kolczak, Margarette S; Phillips-Howard, Penelope A; Mathenge, Evan M; ter Kuile, Feiko O; Nahlen, Bernard L; Hightower, Allen W; Hawley, William A

2003-04-01

The effect of permethrin-treated bed nets (ITNs) on malaria vectors was studied as part of a large-scale, randomized, controlled trial in western Kenya. Indoor resting densities of fed Anopheles gambiae s.l. and An. funestus in intervention houses were 58.5% (P = 0.010) and 94.5% (P = 0.001) lower, respectively, compared with control houses. The sporozoite infection rate in An. gambiae s.l. was 0.8% in intervention areas compared with 3.4% (P = 0.026) in control areas, while the sporozoite infection rates in An. funestus were not significantly different between the two areas. We estimated the overall transmission of Plasmodium falciparum in intervention areas to be 90% lower than in control areas. Permethrin resistance was not detected during the study period. As measured by densities of An. gambiae s.l., the efficacy of bed nets decreased if one or more residents did not sleep under a net or if bed nets had not been re-treated within six months. These results indicate that ITNs are optimally effective if used every night and if permethrin is reapplied at least biannually.

Hexavalents in spermatocytes of Robertsonian heterozygotes between Mus m. domesticus 2n 26 from the Vulcano and Lipari Islands (Aeolian Archipelago, Italy)

PubMed Central

Berríos, Soledad; Fernández-Donoso, Raúl; Page, Jesús; Ayarza, Eliana; Capanna, Ernesto; Solano, Emanuela; Castiglia, Riccardo

2018-01-01

The size and shape of the chromosomes, as well as the chromosomal domains that compose them, are determinants in the distribution and interaction between the bivalents within the nucleus of spermatocytes in prophase I of meiosis. Thus the nuclear architecture characteristic of the karyotype of a species can be modified by chromosomal changes such as Robertsonian (RB) chromosomes. In this study we analysed the meiotic prophase nuclear organization of the heterozygous spermatocytes from Mus musculus domesticus 2n=26, and the synaptic configuration of the hexavalent formed by the dependent Rb chromosomes Rbs 6.16, 16.10, 10.15, 15.17 and the telocentric chromosomes 6 and 17. Spreads of 88 pachytene spermatocytes from two males were studied and in all of them five metacentric bivalents, four telocentric bivalents, one hexavalent and the XY bivalent were observed. About 48% of the hexavalents formed a chain or a ring of synapsed chromosomes, the latter closed by synapsis between the short arms of telocentric chromosomes 6 and 17. About 52% of hexavalents formed an open chain of 10 synapsed chromosomal arms belonging to 6 chromosomes. In about half of the unsynapsed hexavalents one of the telocentric chromosome short arms appears associated with the X chromosome single axis, which was otherwise normally paired with the Y chromosome. The cluster of pericentromeric heterochromatin mostly determines the hexavalent’s nuclear configuration, dragging the centromeric regions and all the chromosomes towards the nuclear envelope similar to an association of five telocentric bivalents. These reiterated encounters between these chromosomes restrict the interactions with other chromosomal domains and might favour eventual rearrangements within the metacentric, telocentric or hexavalent chromosome subsets. The unsynapsed short arms of telocentric chromosomes frequently bound to the single axis of the X chromosome could further complicate the already complex segregation of hexavalent chromosomes. PMID:29569877

Hexavalents in spermatocytes of Robertsonian heterozygotes between Mus m. domesticus 2n=26 from the Vulcano and Lipari Islands (Aeolian Archipelago, Italy).

PubMed

Berríos, Soledad; Fernández-Donoso, Raúl; Page, Jesús; Ayarza, Eliana; Capanna, Ernesto; Solano, Emanuela; Castiglia, Riccardo

2018-02-20

The size and shape of the chromosomes, as well as the chromosomal domains that compose them, are determinants in the distribution and interaction between the bivalents within the nucleus of spermatocytes in prophase I of meiosis. Thus the nuclear architecture characteristic of the karyotype of a species can be modified by chromosomal changes such as Rb chromosomes. In this study we analysed the meiotic prophase nuclear organization of the heterozygous spermatocytes from Mus musculus domesticus 2n=26, and the synaptic configuration of the hexavalent formed by the dependent Rb chromosomes Rbs 6.16, 16.10, 10.15, 15.17 and the telocentric chromosomes 6 and 17. Spreads of 88 pachytene spermatocytes from two males were studied and in all of them five metacentric bivalents, four telocentric bivalents, one hexavalent and the XY bivalent were observed. About 48% of the hexavalents formed a chain or a ring of synapsed chromosomes, the latter closed by synapsis between the short arms of telocentric chromosomes 6 and 17.  About 52% of hexavalents formed an open chain of 10 synapsed chromosomal arms belonging to 6 chromosomes.  In about half of the unsynapsed hexavalents one of the telocentric chromosome short arms appears associated with the X chromosome single axis, which was otherwise normally paired with the Y chromosome.  The cluster of pericentromeric heterochromatin mostly determines the hexavalent's nuclear configuration, dragging the centromeric regions and all the chromosomes towards the nuclear envelope similar to an association of five telocentric bivalents. These reiterated encounters between these chromosomes restrict the interactions with other chromosomal domains and might favour eventual rearrangements within the metacentric, telocentric or hexavalent chromosome subsets. The unsynapsed short arms of telocentric chromosomes frequently bound to the single axis of the X chromosome could further complicate the already complex segregation of hexavalent chromosomes.

[Origin and morphological features of small supernumerary marker chromosomes in Turner syndrome].

PubMed

Liu, Nan; Tong, Tong; Chen, Yue; Chen, Yanling; Cai, Chunquan

2018-02-10

OBJECTIVE To explore the origin and morphological features of small supernumerary marker chromosomes (sSMCs) in Turner syndrome. METHODS For 5 cases of Turner syndrome with a sSMC identified by conventional G-banding, dual-color fluorescence in situ hybridization (FISH) was applied to explore their origin and morphological features. RESULTS Among the 5 cases, 3 have derived from the X chromosome, which included 2 ring chromosomes and 1 centric minute. For the 2 sSMCs derived from the Y chromosome, 1 was ring or isodicentric chromosome, while the other was an isodicentric chromosome. CONCLUSION The sSMCs found in Turner syndrome have almost all derived from sex chromosomes. The majority of sSMCs derived from the X chromosome will form ring chromosomes, while a minority will form centric minute. While most sSMC derived from Y chromosome may exist as isodicentric chromosomes, and a small number may exist as rings. For Turner syndrome patients with sSMCs, dual-color FISH may be used to delineate their origins to facilitate genetic counseling and selection of clinical regime.

Biting behaviour of African malaria vectors: 1. where do the main vector species bite on the human body?

PubMed

Braack, Leo; Hunt, Richard; Koekemoer, Lizette L; Gericke, Anton; Munhenga, Givemore; Haddow, Andrew D; Becker, Piet; Okia, Michael; Kimera, Isaac; Coetzee, Maureen

2015-02-04

Malaria control in Africa relies heavily on indoor vector management, primarily indoor residual spraying and insecticide treated bed nets. Little is known about outdoor biting behaviour or even the dynamics of indoor biting and infection risk of sleeping household occupants. In this paper we explore the preferred biting sites on the human body and some of the ramifications regarding infection risk and exposure management. We undertook whole-night human landing catches of Anopheles arabiensis in South Africa and Anopheles gambiae s.s. and Anopheles funestus in Uganda, for seated persons wearing short sleeve shirts, short pants, and bare legs, ankles and feet. Catches were kept separate for different body regions and capture sessions. All An. gambiae s.l. and An. funestus group individuals were identified to species level by PCR. Three of the main vectors of malaria in Africa (An. arabiensis, An. gambiae s.s. and An. funestus) all have a preference for feeding close to ground level, which is manifested as a strong propensity (77.3% - 100%) for biting on lower leg, ankles and feet of people seated either indoors or outdoors, but somewhat randomly along the lower edge of the body in contact with the surface when lying down. If the lower extremities of the legs (below mid-calf level) of seated people are protected and therefore exclude access to this body region, vector mosquitoes do not move higher up the body to feed at alternate body sites, instead resulting in a high (58.5% - 68.8%) reduction in biting intensity by these three species. Protecting the lower limbs of people outdoors at night can achieve a major reduction in biting intensity by malaria vector mosquitoes. Persons sleeping at floor level bear a disproportionate risk of being bitten at night because this is the preferred height for feeding by the primary vector species. Therefore it is critical to protect children sleeping at floor level (bednets; repellent-impregnated blankets or sheets, etc.). Additionally, the opportunity exists for the development of inexpensive repellent-impregnated anklets and/or sandals to discourage vectors feeding on the lower legs under outdoor conditions at night.

Ecological niche partitioning between Anopheles gambiae molecular forms in Cameroon: the ecological side of speciation

PubMed Central

Simard, Frédéric; Ayala, Diego; Kamdem, Guy Colince; Pombi, Marco; Etouna, Joachim; Ose, Kenji; Fotsing, Jean-Marie; Fontenille, Didier; Besansky, Nora J; Costantini, Carlo

2009-01-01

Background Speciation among members of the Anopheles gambiae complex is thought to be promoted by disruptive selection and ecological divergence acting on sets of adaptation genes protected from recombination by polymorphic paracentric chromosomal inversions. However, shared chromosomal polymorphisms between the M and S molecular forms of An. gambiae and insufficient information about their relationship with ecological divergence challenge this view. We used Geographic Information Systems, Ecological Niche Factor Analysis, and Bayesian multilocus genetic clustering to explore the nature and extent of ecological and chromosomal differentiation of M and S across all the biogeographic domains of Cameroon in Central Africa, in order to understand the role of chromosomal arrangements in ecological specialisation within and among molecular forms. Results Species distribution modelling with presence-only data revealed differences in the ecological niche of both molecular forms and the sibling species, An. arabiensis. The fundamental environmental envelope of the two molecular forms, however, overlapped to a large extent in the rainforest, where they occurred in sympatry. The S form had the greatest niche breadth of all three taxa, whereas An. arabiensis and the M form had the smallest niche overlap. Correspondence analysis of M and S karyotypes confirmed that molecular forms shared similar combinations of chromosomal inversion arrangements in response to the eco-climatic gradient defining the main biogeographic domains occurring across Cameroon. Savanna karyotypes of M and S, however, segregated along the smaller-scale environmental gradient defined by the second ordination axis. Population structure analysis identified three chromosomal clusters, each containing a mixture of M and S specimens. In both M and S, alternative karyotypes were segregating in contrasted environments, in agreement with a strong ecological adaptive value of chromosomal inversions. Conclusion Our data suggest that inversions on the second chromosome of An. gambiae are not causal to the evolution of reproductive isolation between the M and S forms. Rather, they are involved in ecological specialization to a similar extent in both genetic backgrounds, and most probably predated lineage splitting between molecular forms. However, because chromosome-2 inversions promote ecological divergence, resulting in spatial and/or temporal isolation between ecotypes, they might favour mutations in other ecologically significant genes to accumulate in unlinked chromosomal regions. When such mutations occur in portions of the genome where recombination is suppressed, such as the pericentromeric regions known as speciation islands in An. gambiae, they would contribute further to the development of reproductive isolation. PMID:19460146

Kinetochore-independent chromosome segregation driven by lateral microtubule bundles

PubMed Central

Muscat, Christina C; Torre-Santiago, Keila M; Tran, Michael V; Powers, James A; Wignall, Sarah M

2015-01-01

During cell division, chromosomes attach to spindle microtubules at sites called kinetochores, and force generated at the kinetochore-microtubule interface is the main driver of chromosome movement. Surprisingly, kinetochores are not required for chromosome segregation on acentrosomal spindles in Caenorhabditis elegans oocytes, but the mechanism driving chromosomes apart in their absence is not understood. In this study, we show that lateral microtubule–chromosome associations established during prometaphase remain intact during anaphase to facilitate separation, defining a novel form of kinetochore-independent segregation. Chromosome dynamics during congression and segregation are controlled by opposing forces; plus-end directed forces are mediated by a protein complex that forms a ring around the chromosome center and dynein on chromosome arms provides a minus-end force. At anaphase onset, ring removal shifts the balance between these forces, triggering poleward movement along lateral microtubule bundles. This represents an elegant strategy for controlling chromosomal movements during cell division distinct from the canonical kinetochore-driven mechanism. DOI: http://dx.doi.org/10.7554/eLife.06462.001 PMID:26026148

Convergent evolution of Y chromosome gene content in flies.

PubMed

Mahajan, Shivani; Bachtrog, Doris

2017-10-04

Sex-chromosomes have formed repeatedly across Diptera from ordinary autosomes, and X-chromosomes mostly conserve their ancestral genes. Y-chromosomes are characterized by abundant gene-loss and an accumulation of repetitive DNA, yet the nature of the gene repertoire of fly Y-chromosomes is largely unknown. Here we trace gene-content evolution of Y-chromosomes across 22 Diptera species, using a subtraction pipeline that infers Y genes from male and female genome, and transcriptome data. Few genes remain on old Y-chromosomes, but the number of inferred Y-genes varies substantially between species. Young Y-chromosomes still show clear evidence of their autosomal origins, but most genes on old Y-chromosomes are not simply remnants of genes originally present on the proto-sex-chromosome that escaped degeneration, but instead were recruited secondarily from autosomes. Despite almost no overlap in Y-linked gene content in different species with independently formed sex-chromosomes, we find that Y-linked genes have evolved convergent gene functions associated with testis expression. Thus, male-specific selection appears as a dominant force shaping gene-content evolution of Y-chromosomes across fly species.While X-chromosome gene content tends to be conserved, Y-chromosome evolution is dynamic and difficult to reconstruct. Here, Mahajan and Bachtrog use a subtraction pipeline to identify Y-linked genes in 22 Diptera species, revealing patterns of Y-chromosome gene-content evolution.

Meiotic events in Oenothera - a non-standard pattern of chromosome behaviour.

PubMed

Golczyk, Hieronim; Musiał, Krystyna; Rauwolf, Uwe; Meurer, Jörg; Herrmann, Reinhold G; Greiner, Stephan

2008-11-01

The genus Oenothera shows an intriguing extent of permanent translocation heterozygosity. Reciprocal translocations of chromosome arms in species or populations result in various kinds of chromosome multivalents in diakinesis. Early meiotic events conditioning such chromosome behaviour are poorly understood. We found a surprising uniformity of the leptotene-diplotene period, regardless of the chromosome configuration at diakinesis (ring of 14, 7 bivalents, mixture of bivalents and multivalents). It appears that the earliest chromosome interactions at Oenothera meiosis are untypical, since they involve pericentromeric regions. During early leptotene, proximal chromosome parts cluster and form a highly polarized Rabl configuration. Telomeres associated in pairs were seen at zygotene. The high degree of polarization of meiotic nuclei continues for an exceptionally long period, i.e., during zygotene-pachytene into the diplotene contraction stage. The Rabl-polarized meiotic architecture and clustering of pericentromeres suggest a high complexity of karyotypes, not only in structural heterozygotes but also in bivalent-forming homozygous species.

Chromosome dynamics in meiotic prophase I in plants.

PubMed

Ronceret, A; Pawlowski, W P

2010-07-01

Early stages of meiotic prophase are characterized by complex and dramatic chromosome dynamics. Chromosome behavior during this period is associated with several critical meiotic processes that take place at the molecular level, such as recombination and homologous chromosome recognition and pairing. Studies to characterize specific patterns of chromosome dynamics and to identify their exact roles in the progression of meiotic prophase are only just beginning in plants. These studies are facilitated by advances in imaging technology in the recent years, including development of ultra-resolution three-dimensional and live microscopy methods. Studies conducted so far indicate that different chromosome regions exhibit different dynamics patterns in early prophase. In many species telomeres cluster at the nuclear envelope at the beginning of zygotene forming the telomere bouquet. The bouquet has been traditionally thought to facilitate chromosome pairing by bringing chromosome ends into close proximity, but recent studies suggest that its main role may rather be facilitating rapid movements of chromosomes during zygotene. In some species, including wheat and Arabidopsis, there is evidence that centromeres form pairs (couple) before the onset of pairing of chromosome arms. While significant advances have been achieved in elucidating the patterns of chromosome behavior in meiotic prophase I, factors controlling chromosome dynamics are still largely unknown and require further studies. Copyright 2010 S. Karger AG, Basel.

Structure of interphase chromosomes in the nuclei of Drosophila cells.

PubMed

Banfalvi, Gaspar

2006-10-01

Fluorescent images of interphase chromatin structures and chromosome structures isolated from reversibly permeable Drosophila cells were analyzed. Decondensed chromatin in early S phase (2.0-2.5 C-value) consisted of a veil-like fibrillary network. Fibrillar chromatin formed rodlets later in the early S phase (2.5-2.75 C). Drosophila chromosomes contain several smaller subunits called rodlets. Fibrillar chromatin turned to chromatin ribbon and the early mid-S-phase globular chromosomes (2.75-3.0 C), then to opened fibrous globular forms later in the mid-S-phase (3.0-3.25 C), to late-S-phase supercoiled ribbons (3.25-3.5 C), end-S-phase elongated prechromosomes (3.5-3.75 C), bent and linear chromosomes (3.75-4.0 C). Early-S phase chromatin fibrils in the nuclei of Drosophila cells are thinner than the veil-like structures in mammalian cells. The connectivity of chromosomes shows linear arrangement (3, 1, 2, 4), with larger chromosomes (1 and 2) inside and smaller chromosomes (3, 4) at the two ends in the chromosomal chain.

New evidence of mating swarms of the malaria vector, Anopheles arabiensis in Tanzania

PubMed Central

Kaindoa, Emmanuel W.; Ngowo, Halfan S.; Limwagu, Alex; Mkandawile, Gustav; Kihonda, Japhet; Masalu, John Paliga; Bwanary, Hamis; Diabate, Abdoulaye; Okumu, Fredros O.

2017-01-01

Background: Malaria mosquitoes form mating swarms around sunset, often at the same locations for months or years. Unfortunately, studies of Anopheles swarms are rare in East Africa, the last recorded field observations in Tanzania having been in 1983. Methods: Mosquito swarms were surveyed by trained volunteers between August-2016 and June-2017 in Ulanga district, Tanzania. Identified Anopheles swarms were sampled using sweep nets, and collected mosquitoes killed by refrigeration then identified by sex and taxa. Sub-samples were further identified by PCR, and spermatheca of females examined for mating status. Mosquito ages were estimated by observing female ovarian tracheoles and rotation of male genitalia. GPS locations, types of swarm markers, start/end times of swarming, heights above ground, mosquito counts/swarm, and copulation events were recorded. Results: A total of 216 Anopheles swarms were identified, characterized and mapped, from which 7,142 Anopheles gambiae s.l and 13 Anopheles funestus were sampled. The An. gambiae s.l were 99.6% males and 0.4% females, while the An. funestus were all males. Of all An. gambiae s.l analyzed by PCR, 86.7% were An. arabiensis, while 13.3% returned non-amplified DNA. Mean height (±SD) of swarms was 2.74±0.64m, and median duration was 20 (IQR; 15-25) minutes. Confirmed swarm markers included rice fields (25.5%), burned grounds (17.2%), banana trees (13%), brick piles (8.8%), garbage heaps (7.9%) and ant-hills (7.4%). Visual estimates of swarm sizes by the volunteers was strongly correlated to actual sizes by sweep nets (R=0.94; P=<0.001). All females examined were nulliparous and 95.6% [N=6787] of males had rotated genitalia, indicating sexual maturity. Conclusions: This is the first report of Anopheles swarms in Tanzania in more than three decades. The study demonstrates that the swarms can be identified and characterized by trained community-based volunteers, and highlights potential new interventions, for example targeted aerosol spraying of the swarms to improve malaria control. PMID:29184918

Chromosome Bridges Maintain Kinetochore-Microtubule Attachment throughout Mitosis and Rarely Break during Anaphase.

PubMed

Pampalona, Judit; Roscioli, Emanuele; Silkworth, William T; Bowden, Brent; Genescà, Anna; Tusell, Laura; Cimini, Daniela

2016-01-01

Accurate chromosome segregation during cell division is essential to maintain genome stability, and chromosome segregation errors are causally linked to genetic disorders and cancer. An anaphase chromosome bridge is a particular chromosome segregation error observed in cells that enter mitosis with fused chromosomes/sister chromatids. The widely accepted Breakage/Fusion/Bridge cycle model proposes that anaphase chromosome bridges break during mitosis to generate chromosome ends that will fuse during the following cell cycle, thus forming new bridges that will break, and so on. However, various studies have also shown a link between chromosome bridges and aneuploidy and/or polyploidy. In this study, we investigated the behavior and properties of chromosome bridges during mitosis, with the idea to gain insight into the potential mechanism underlying chromosome bridge-induced aneuploidy. We find that only a small number of chromosome bridges break during anaphase, whereas the rest persist through mitosis into the subsequent cell cycle. We also find that the microtubule bundles (k-fibers) bound to bridge kinetochores are not prone to breakage/detachment, thus supporting the conclusion that k-fiber detachment is not the cause of chromosome bridge-induced aneuploidy. Instead, our data suggest that while the microtubules bound to the kinetochores of normally segregating chromosomes shorten substantially during anaphase, the k-fibers bound to bridge kinetochores shorten only slightly, and may even lengthen, during anaphase. This causes some of the bridge kinetochores/chromosomes to lag behind in a position that is proximal to the cell/spindle equator and may cause the bridged chromosomes to be segregated into the same daughter nucleus or to form a micronucleus.

Sequential cloning of chromosomes

DOEpatents

Lacks, Sanford A.

1995-07-18

A method for sequential cloning of chromosomal DNA of a target organism is disclosed. A first DNA segment homologous to the chromosomal DNA to be sequentially cloned is isolated. The first segment has a first restriction enzyme site on either side. A first vector product is formed by ligating the homologous segment into a suitably designed vector. The first vector product is circularly integrated into the target organism's chromosomal DNA. The resulting integrated chromosomal DNA segment includes the homologous DNA segment at either end of the integrated vector segment. The integrated chromosomal DNA is cleaved with a second restriction enzyme and ligated to form a vector-containing plasmid, which is replicated in a host organism. The replicated plasmid is then cleaved with the first restriction enzyme. Next, a DNA segment containing the vector and a segment of DNA homologous to a distal portion of the previously isolated DNA segment is isolated. This segment is then ligated to form a plasmid which is replicated within a suitable host. This plasmid is then circularly integrated into the target chromosomal DNA. The chromosomal DNA containing the circularly integrated vector is treated with a third, retrorestriction (class IIS) enzyme. The cleaved DNA is ligated to give a plasmid that is used to transform a host permissive for replication of its vector. The sequential cloning process continues by repeated cycles of circular integration and excision. The excision is carried out alternately with the second and third enzymes.

A cost-effective, community-based, mosquito-trapping scheme that captures spatial and temporal heterogeneities of malaria transmission in rural Zambia

PubMed Central

2014-01-01

Background Monitoring mosquito population dynamics is essential to guide selection and evaluation of malaria vector control interventions but is typically implemented by mobile, centrally-managed teams who can only visit a limited number of locations frequently enough to capture longitudinal trends. Community-based (CB) mosquito trapping schemes for parallel, continuous monitoring of multiple locations are therefore required that are practical, affordable, effective, and reliable. Methods A CB surveillance scheme, with a monthly sampling and reporting cycle for capturing malaria vectors, using Centers for Disease Control and Prevention light traps (LT) and Ifakara Tent Traps (ITT), were conducted by trained community health workers (CHW) in 14 clusters of households immediately surrounding health facilities in rural south-east Zambia. At the end of the study, a controlled quality assurance (QA) survey was conducted by a centrally supervised expert team using human landing catch (HLC), LT and ITT to evaluate accuracy of the CB trapping data. Active surveillance of malaria parasite infection rates amongst humans was conducted by CHWs in the same clusters to determine the epidemiological relevance of these CB entomological surveys. Results CB-LT and CB-ITT exhibited relative sampling efficiencies of 50 and 7%, respectively, compared with QA surveys using the same traps. However, cost per sampling night was lowest for CB-LT ($13.6), followed closely by CB-ITT ($18.0), both of which were far less expensive than any QA survey (HLC: $138, LT: $289, ITT: $269). Cost per specimen of Anopheles funestus captured was lowest for CB-LT ($5.3), followed by potentially hazardous QA-HLC ($10.5) and then CB-ITT ($28.0), all of which were far more cost-effective than QA-LT ($141) and QA-ITT ($168). Time-trends of malaria diagnostic positivity (DP) followed those of An. funestus density with a one-month lag and the wide range of mean DP across clusters was closely associated with mean densities of An. funestus caught by CB-LT (P < 0.001). Conclusions CB trapping schemes appear to be far more affordable, epidemiologically relevant and cost-effective than centrally supervised trapping schemes and may well be applicable to enhance intervention trials and even enable routine programmatic monitoring of vector population dynamics on unprecedented national scales. PMID:24906704

Surveillance of malaria vector population density and biting behaviour in western Kenya.

PubMed

Ototo, Ednah N; Mbugi, Jenard P; Wanjala, Christine L; Zhou, Guofa; Githeko, Andrew K; Yan, Guiyun

2015-06-17

Malaria is a great public health burden and Africa suffers the largest share of malaria-attributed deaths. Despite control efforts targeting indoor malaria transmission, such as insecticide-treated bed nets (ITNs) and deployment of indoor residual spraying, transmission of the parasite in western Kenya is still maintained. This study was carried out to determine the impact of ITNs on indoor vector densities and biting behaviour in western Kenya. Indoor collection of adult mosquitoes was done monthly in six study sites in western Kenya using pyrethrum spray collections from 2012 to 2014. The rotator trap collections were done in July-August in 2013 and May-June in 2014. Mosquitoes were collected every 2 h between 18.00 and 08.00 h. Human behaviour study was conducted via questionnaire surveys. Species within Anopheles gambiae complex was differentiated by PCR and sporozoite infectivity was determined by ELISA. Species distribution was determined and bed net coverage in the study sites was recorded. During the study a total of 5,469 mosquito vectors were collected from both PSC and Rotator traps comprising 3,181 (58.2%) Anopheles gambiae and 2,288 (41.8%) Anopheles funestus. Compared to all the study sites, Rae had the highest density of An. gambiae with a mean of 1.2 (P<0.001) while Kombewa had the highest density of An. funestus with a mean of 1.08 (P<0.001). Marani had the lowest density of vectors with 0.06 An. gambiae and 0.17 An. funestus (P<0.001). Among the 700 PCR confirmed An. gambiae s.l. individuals, An. gambiae s.s. accounted for 49% and An. arabiensis 51%. Over 50% of the study population stayed outdoors between 18.00 and 20.00 and 06.00 and 08.00 which was the time when highest densities of blood fed vectors were collected. Anopheles gambie s.s. was the main malaria parasite vector in the highland sites and An. arabiensis in the lowland sites. Bed net ownership in 2012 averaged 87% across the study sites. This study suggests that mass distribution of ITNs has had a significant impact on vector densities, species distribution and sporozoite rate. However, shift of biting time poses significant threats to the current malaria vector control strategies which heavily rely on indoor controls.

Globular and fibrous structure in barley chromosomes revealed by high-resolution scanning electron microscopy.

PubMed

Iwano, M; Fukui, K; Takaichi, S; Isogai, A

1997-08-01

Barley chromosomes were prepared for high-resolution scanning electron microscopy using a combination of enzyme maceration, treatment in acetic acid and osmium impregnation using thiocarbohydrazide. Using this technique, the three-dimensional ultrastructure of interphase nuclei and mitotic chromosomes was examined. In Interphase, different levels of chromatin condensation were observed, consisting of fibrils 10 nm in diameter, 20- to 40-nm fibres and a higher order complex. In prophase, globular and strand-like structures composed of 20- to 40-nm fibres were dominant. As the cells progressed through the cell cycle and the chromatin condensed, globular and strand-like structures (chromomeres) were coiled and packed to form chromosomes. Chromomeres were observed as globular protuberances on the surface of metaphase chromosomes. These findings indicate that the chromomere is a fundamental substructure of the higher order architecture of the chromosome. In the centromeric region, there were no globular protuberances, but 20- to 40-nm fibres were folded compactly to form a higher level organization surrounding the chromosomal axia.

CHROMOSOMAL DIFFERENTIATIONS OF THE LAMPBRUSH TYPE FORMED BY THE Y CHROMOSOME IN DROSOPHILA HYDEI AND DROSOPHILA NEOHYDEI

PubMed Central

Hess, Oswald; Meyer, Günther F.

1963-01-01

The nuclei of growing spermatocytes in Drosophila hydei and D. neohydei are characterized by the appearance of phase-specific, paired, loop-shaped structures thought to be similar to the loops in lampbrush chromosomes of amphibian oocytes. In X/O-males of D. hydei spermatogenesis is completely blocked before the first maturation division. No spermatozoa are formed in such testes. In the nuclei of X/O-spermatocytes, paired loop formations are absent. This shows the dependence of these chromosomal functional structures upon the Y chromosome. The basis of this dependence could be shown through an investigation of males with two Y chromosomes. All loop pairs are present in duplicate in XYY males. This proves that the intranuclear formations are structural modifications of the Y chromosome itself. These functional structures are species-specific and characteristically different in Drosophila hydei and D. neohydei. Reciprocal species crosses and a backcross showed that the spermatocyte nuclei of all hybrid males possess the functional structures corresponding to the species which donated the Y chromosome. This shows that the morphological character of the functional structures is also determined by the Y chromosome. PMID:13954225

Allocation of the S-genome chromosomes of Aegilops variabilis Eig. carrying powdery mildew resistance in triticale (× Triticosecale Wittmack).

PubMed

Kwiatek, M; Belter, J; Majka, M; Wiśniewska, H

2016-03-01

It has been hypothesized that the powdery mildew adult plant resistance (APR) controlled by the Pm13 gene in Aegilops longissima Schweinf. & Muschl. (S(l)S(l)) has been evolutionary transferred to Aegilops variabilis Eig. (UUSS). The molecular marker analysis and the visual evaluation of powdery mildew symptoms in Ae. variabilis and the Ae. variabilis × Secale cereale amphiploid forms (2n = 6x = 42, UUSSRR) showed the presence of product that corresponded to Pm13 marker and the lower infection level compared to susceptible model, respectively. This study also describes the transfer of Ae. variabilis Eig. (2n = 4x = 28, U(v)U(v)S(v)S(v)) chromosomes, carrying powdery mildew resistance, into triticale (× Triticosecale Wittm., 2n = 6x = 42, AABBRR) using Ae. variabilis × S. cereale amphiploid forms. The individual chromosomes of Ae. variabilis, triticale 'Lamberto' and hybrids were characterized by genomic and fluorescence in situ hybridization (GISH/FISH). The chromosome configurations of obtained hybrid forms were studied at first metaphase of meiosis of pollen mother cells (PMCs) using GISH. The statistical analysis showed that the way of S-genome chromosome pairing and transmission to subsequent hybrid generations was diploid-like and had no influence on chromosome pairing of triticale chromosomes. The cytogenetic study of hybrid forms were supported by the marker-assisted selection using Pm13 marker and visual evaluation of natural infection by Blumeria graminis, that allowed to select the addition or substitution lines of hybrids carrying chromosome 3S(v) which were tolerant to the powdery mildew infection.

Dicentric chromosome formation and epigenetics of centromere formation in plants.

PubMed

Fu, Shulan; Gao, Zhi; Birchler, James; Han, Fangpu

2012-03-20

Plant centromeres are generally composed of tandem arrays of simple repeats that form a complex chromosome locus where the kinetochore forms and microtubules attach during mitosis and meiosis. Each chromosome has one centromere region, which is essential for accurate division of the genetic material. Recently, chromosomes containing two centromere regions (called dicentric chromosomes) have been found in maize and wheat. Interestingly, some dicentric chromosomes are stable because only one centromere is active and the other one is inactivated. Because such arrays maintain their typical structure for both active and inactive centromeres, the specification of centromere activity has an epigenetic component independent of the DNA sequence. Under some circumstances, the inactive centromeres may recover centromere function, which is called centromere reactivation. Recent studies have highlighted the important changes, such as DNA methylation and histone modification, that occur during centromere inactivation and reactivation. Copyright © 2012. Published by Elsevier Ltd.

Anopheles gambiae complex (Diptera:Culicidae) near Bissau City, Guinea Bissau, West Africa.

PubMed

Fonseca, L F; Di Deco, M A; Carrara, G C; Dabo, I; Do Rosario, V; Petrarca, V

1996-11-01

Cytogenetic studies on mosquitoes collected inside bednets near Bissau City confirmed the presence of Anopheles melas Theobald and An. gambiae Giles sensu stricto, the latter species prevailing in rainy season samples (approximately 80% in average) and the former in dry season samples (> 90%). Seasonal and ecogeographical variations in the frequency of species and chromosomal inversions were analyzed. The analysis of An. gambiae sensu stricto confirmed the existence of the Bissau chromosomal form. The deficiency of heterokaryotypes in most samples indicated the possible coexistence of another chromosomal form not completely panmictic (i.e., randomly mating) with the Bissau form.

Ki-67 acts as a biological surfactant to disperse mitotic chromosomes

PubMed Central

Cuylen, Sara; Blaukopf, Claudia; Politi, Antonio Z.; Müller-Reichert, Thomas; Neumann, Beate; Poser, Ina; Ellenberg, Jan; Hyman, Anthony A.; Gerlich, Daniel W.

2016-01-01

Summary Eukaryotic genomes are partitioned into chromosomes, which during mitosis form compact and spatially well-separated mechanical bodies1–3.This enables chromosomes to move independently of each other for segregation of precisely one copy of the genome to each of the nascent daughter cells. Despite insights into the spatial organization of mitotic chromosomes4 and the discovery of proteins at the chromosome surface3,5,6, the molecular and biophysical basis of mitotic chromosome individuality have remained unclear. We report that Ki-67, a component of the mitotic chromosome periphery, prevents chromosomes from collapsing into a single chromatin mass after nuclear envelope disassembly, thus enabling independent chromosome motility and efficient interactions with the mitotic spindle. The chromosome separation function of Ki-67 is not confined within a specific protein domain but correlates with size and net charge of truncation mutants that apparently lack secondary structure. This suggests that Ki-67 forms a steric and electrical barrier, similar to surface-active agents (surfactants) that disperse particles or phase-separated liquid droplets in solvents. Fluorescence correlation spectroscopy showed a high surface density of Ki-67 and dual-color labeling of both protein termini revealed an extended molecular conformation, indicating brush-like arrangements that are characteristic for polymeric surfactants. Our study thus elucidates a biomechanical role of the mitotic chromosome periphery and suggests that natural proteins can function as surfactants in intracellular compartmentalization. PMID:27362226

Chromosome-encoded beta-lactamases of Citrobacter diversus. Interaction with beta-iodopenicillanate and labelling of the active site.

PubMed Central

Amicosante, G; Oratore, A; Joris, B; Galleni, M; Frère, J M; Van Beeumen, J

1988-01-01

Both forms of the chromosome-encoded beta-lactamase of Citrobacter diversus react with beta-iodopenicillanate at a rate characteristic of class A beta-lactamases. The active site of form I was labelled with the same reagent. The sequence of the peptide obtained after trypsin hydrolysis is identical with that of a peptide obtained in a similar manner from the chromosome-encoded beta-lactamase of Klebsiella pneumoniae. PMID:2848500

The X chromosome of monotremes shares a highly conserved region with the eutherian and marsupial X chromosomes despite the absence of X chromosome inactivation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watson, J.M.; Spencer, J.A.; Graves, J.A.M.

1990-09-01

Eight genes, located on the long arm of the human X chromosome and present on the marsupial X chromosome, were mapped by in situ hybridization to the chromosomes of the platypus Ornithorhynchus anatinus, one of the three species of monotreme mammals. All were located on the X chromosome. The authors conclude that the long arm of the human X chromosome represents a highly conserved region that formed part of the X chromosome in a mammalian ancestor at least 150 million years ago. Since three of these genes are located on the long arm of the platypus X chromosome, which ismore » G-band homologous to the Y chromosome and apparently exempt from X chromosome inactivation, the conservation of this region has evidently not depended on isolation by X-Y chromosome differentiation and X chromosome inactivation.« less

Sequential cloning of chromosomes

DOEpatents

Lacks, S.A.

1995-07-18

A method for sequential cloning of chromosomal DNA of a target organism is disclosed. A first DNA segment homologous to the chromosomal DNA to be sequentially cloned is isolated. The first segment has a first restriction enzyme site on either side. A first vector product is formed by ligating the homologous segment into a suitably designed vector. The first vector product is circularly integrated into the target organism`s chromosomal DNA. The resulting integrated chromosomal DNA segment includes the homologous DNA segment at either end of the integrated vector segment. The integrated chromosomal DNA is cleaved with a second restriction enzyme and ligated to form a vector-containing plasmid, which is replicated in a host organism. The replicated plasmid is then cleaved with the first restriction enzyme. Next, a DNA segment containing the vector and a segment of DNA homologous to a distal portion of the previously isolated DNA segment is isolated. This segment is then ligated to form a plasmid which is replicated within a suitable host. This plasmid is then circularly integrated into the target chromosomal DNA. The chromosomal DNA containing the circularly integrated vector is treated with a third, retrorestriction (class IIS) enzyme. The cleaved DNA is ligated to give a plasmid that is used to transform a host permissive for replication of its vector. The sequential cloning process continues by repeated cycles of circular integration and excision. The excision is carried out alternately with the second and third enzymes. 9 figs.

PCR-based karyotyping of Anopheles gambiae inversion 2Rj identifies the BAMAKO chromosomal form.

PubMed

Coulibaly, Mamadou B; Pombi, Marco; Caputo, Beniamino; Nwakanma, Davis; Jawara, Musa; Konate, Lassana; Dia, Ibrahima; Fofana, Abdrahamane; Kern, Marcia; Simard, Frédéric; Conway, David J; Petrarca, Vincenzo; della Torre, Alessandra; Traoré, Sékou; Besansky, Nora J

2007-10-01

The malaria vector Anopheles gambiae is polymorphic for chromosomal inversions on the right arm of chromosome 2 that segregate nonrandomly between assortatively mating populations in West Africa. One such inversion, 2Rj, is associated with the BAMAKO chromosomal form endemic to southern Mali and northern Guinea Conakry near the Niger River. Although it exploits a unique ecology and both molecular and chromosomal data suggest reduced gene flow between BAMAKO and other A. gambiae populations, no molecular markers exist to identify this form. To facilitate study of the BAMAKO form, a PCR assay for molecular karyotyping of 2Rj was developed based on sequences at the breakpoint junctions. The assay was extensively validated using more than 700 field specimens whose karyotypes were determined in parallel by cytogenetic and molecular methods. As inversion 2Rj also occurs in SAVANNA populations outside the geographic range of BAMAKO, samples were tested from Senegal, Cameroon and western Guinea Conakry as well as from Mali. In southern Mali, where 2Rj polymorphism in SAVANNA populations was very low and most of the 2Rj homozygotes were found in BAMAKO karyotypes, the molecular and cytogenetic methods were almost perfectly congruent. Elsewhere agreement between the methods was much poorer, as the molecular assay frequently misclassified 2Rj heterozygotes as 2R+j standard homozygotes. Molecular karyotyping of 2Rj is robust and accurate on 2R+j standard and 2Rj inverted homozygotes. Therefore, the proposed approach overcomes the lack of a rapid tool for identifying the BAMAKO form across developmental stages and sexes, and opens new perspectives for the study of BAMAKO ecology and behaviour. On the other hand, the method should not be applied for molecular karyotyping of j-carriers within the SAVANNA chromosomal form.

Dissection of resistance to Microdochium nivale in Lolium multiflorum/Festuca arundinacea introgression forms.

PubMed

Płażek, Agnieszka; Pociecha, Ewa; Augustyniak, Adam; Masajada, Katarzyna; Dziurka, Michał; Majka, Joanna; Perlikowski, Dawid; Pawłowicz, Izabela; Kosmala, Arkadiusz

2018-02-01

The potential of resistance to Microdochium nivale is still not recognized for numerous plant species. The forage grasses of Lolium-Festuca complex are important for grass-biomass production in the temperate regions. Lolium multiflorum is a grass with a high forage quality and productivity but also a relatively low resistance to M. nivale. On the contrary, F. arundinacea has a higher potential of resistance but simultaneously a significantly lower forage quality. These two species cross with each other and the intergeneric hybrids possess complementary characters of both genera. Herein, for the first time, we perform the research on L. multiflorum/F. arundinacea introgression forms to decipher mechanisms of resistance to M. nivale in that group of plants. Two forms with distinct levels of resistance were used as models in cytogenetic and biochemical studies. The resistant plant was shown to be a tetraploid with 28 L. multiflorum chromosomes, including one with three F. arundinacea introgressions. The susceptible introgression form revealed the unbalanced genomic structure and only 25 chromosomes. Twenty four chromosomes were shown to be L. multiflorum chromosomes, including one chromosome with F. arundinacea segment. One Festuca chromosome with additional two interstitial F. arundinacea segments, was also revealed in the susceptible form. The selected introgression forms differed in the accumulation profiles of total soluble carbohydrates, phytohormones, and phenolics in the leaf and crown tissue under the control and infection conditions. The higher amount of carbohydrates and salicylic acid in the leaves and crowns as well as a lower amount of abscisic acid in both studied organs and jasmonic acid in the crowns, were shown to be crucial for the expression of resistance to M. nivale in the analyzed hybrids. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

[Karyological studies of two populations of Juniperus communis L. in west Siberia].

PubMed

Mikheeva, N A; Muratova, E N

2005-01-01

Results of a karyological study of Juniperus communis L. populations under swamp and dry conditions are presented. The chromosome number of J. communis are 2n = 22. Analysis of morphological chromosome parameters showed a similarity between karyotypes of both populations. It is possible to identify one pair of asymmetric chromosomes (VIII pair); this chromosome pair is close to submetacentric type. Three pairs of chromosomes (I, VII, VIII) have secondary constrictions. Other metacentric chromosomes form groups of five long (II--VI) and three short (IX-XI) pairs. Differences between two populations in absolute chromosomal length are observed.

[Supernumerary chromosomes in the karyotype of the Siberian spruce, P. obovata].

PubMed

Muratova, E N; Vladimirova, O S

2001-01-01

Results of karyological study of ornamental forms of Picea obovata Ledeb. are presented. Typical chromosome number (2n) is 24, but some trees have one or two additional chromosomes (2n = 24 + 1B; 2n = 24 + 2B). Heritability of additional chromosomes, pollen fertility, morphological features of cones, and seed quality in trees with and without additional chromosomes were studied. System of B-chromosomes is of importance for population and species adaptation and possibly plays a role in adaptation of P. obovata under introduction.

Visualizing how cancer chromosome abnormalities form in living cells

Cancer.gov

For the first time, scientists have directly observed events that lead to the formation of a chromosome abnormality that is often found in cancer cells. The abnormality, called a translocation, occurs when part of a chromosome breaks off and becomes attac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hart, Y.M.; Andermann, E.; Mitchison, H.M.

The neuronal ceroid lipofuscinoses (NCL) are a group of related lysosomal storage diseases classified according to the age of onset, clinical syndrome, and pathology. The clinical syndromes include myoclonus, visual failure, progressive dementia, ataxia and generalized tonic clonic seizures in varying combinations depending on the age of onset and pathology. The mode of inheritance is autosomal recessive in most cases, except for several families with the adult form (Kufs` disease) which have autosomal dominant inheritance. Linkage for the infantile (Halatia-Santavuori) form (CLN1), characterized ultrastructurally by lysosomal granular osmiophilic deposits (GROD), has been demonstrated with markers on chromosome lp, while themore » gene for the typical juvenile (Spielmeyer-Vogt) form (CLN3), characterized by fingerprint-profile inclusions, has been linked to chromosome 16p. The gene locations of the late infantile (Jansky-Bielschowsky) and adult (Kufs` disease) forms are unknown, although it has recently been shown that the late infantile form does not link to chromosome 16p. We describe three siblings, including a pair of monozygotic twins, with juvenile onset NCL with GROD in whom linkage to the CLN3 region of chromsome 16p has been excluded. This would suggest that there is genetic heterogeneity not only among the different clinical syndromes, but also among identical clinical syndromes with different ultrastructural characteristics. Preliminary studies of linkage to chromosome 1p employing the microsatellite marker HY-TM1 have been uninformative. Further studies with other chromosome 1 markers are underway.« less

Change of the heterogametic sex from male to female in the frog.

PubMed Central

Ogata, M; Ohtani, H; Igarashi, T; Hasegawa, Y; Ichikawa, Y; Miura, I

2003-01-01

Two different types of sex chromosomes, XX/XY and ZZ/ZW, exist in the Japanese frog Rana rugosa. They are separated in two local forms that share a common origin in hybridization between the other two forms (West Japan and Kanto) with male heterogametic sex determination and homomorphic sex chromosomes. In this study, to find out how the different types of sex chromosomes differentiated, particularly the evolutionary reason for the heterogametic sex change from male to female, we performed artificial crossings between the West Japan and Kanto forms and mitochondrial 12S rRNA gene sequence analysis. The crossing results showed male bias using mother frogs with West Japan cytoplasm and female bias using those with Kanto cytoplasm. The mitochondrial genes of ZZ/ZW and XX/XY forms, respectively, were similar in sequence to those of the West Japan and Kanto forms. These results suggest that in the primary ZZ/ZW form, the West Japan strain was maternal and thus male bias was caused by the introgression of the Kanto strain while in the primary XX/XY form and vice versa. We therefore hypothesize that sex ratio bias according to the maternal origin of the hybrid population was a trigger for the sex chromosome differentiation and the change of heterogametic sex. PMID:12807781

Three-dimensional positioning and structure of chromosomes in a human prophase nucleus

PubMed Central

Chen, Bo; Yusuf, Mohammed; Hashimoto, Teruo; Estandarte, Ana Katrina; Thompson, George; Robinson, Ian

2017-01-01

The human genetic material is packaged into 46 chromosomes. The structure of chromosomes is known at the lowest level, where the DNA chain is wrapped around a core of eight histone proteins to form nucleosomes. Around a million of these nucleosomes, each about 11 nm in diameter and 6 nm in thickness, are wrapped up into the complex organelle of the chromosome, whose structure is mostly known at the level of visible light microscopy to form a characteristic cross shape in metaphase. However, the higher-order structure of human chromosomes, between a few tens and hundreds of nanometers, has not been well understood. We show a three-dimensional (3D) image of a human prophase nucleus obtained by serial block-face scanning electron microscopy, with 36 of the complete set of 46 chromosomes captured within it. The acquired image allows us to extract quantitative 3D structural information about the nucleus and the preserved, intact individual chromosomes within it, including their positioning and full spatial morphology at a resolution of around 50 nm in three dimensions. The chromosome positions were found, at least partially, to follow the pattern of chromosome territories previously observed only in interphase. The 3D conformation shows parallel, planar alignment of the chromatids, whose occupied volumes are almost fully accounted for by the DNA and known chromosomal proteins. We also propose a potential new method of identifying human chromosomes in three dimensions, on the basis of the measurements of their 3D morphology. PMID:28776025

Abnormal meiosis in an intersectional allotriploid of Populus L. and segregation of ploidy levels in 2x × 3x progeny

PubMed Central

Huo, Beibei; Liu, Wanting; Li, Daili; Liao, Ling

2017-01-01

Triploid plants are usually highly aborted owing to unbalanced meiotic chromosome segregation, but limited viable gametes can participate in the transition to different ploidy levels. In this study, numerous meiotic abnormalities were found with high frequency in an intersectional allotriploid poplar (Populus alba × P. berolinensis ‘Yinzhong’), including univalents, precocious chromosome migration, lagging chromosomes, chromosome bridges, micronuclei, and precocious cytokinesis, indicating high genetic imbalance in this allotriploid. Some micronuclei trigger mini-spindle formation in metaphase II and participate in cytokinesis to form polyads with microcytes. Unbalanced chromosome segregation and chromosome elimination resulted in the formation of microspores with aneuploid chromosome sets. Fusion of sister nuclei occurs in microsporocytes with precocious cytokinesis, which could form second meiotic division restitution (SDR)-type gametes. However, SDR-type gametes likely contain incomplete chromosome sets due to unbalanced segregation of homologous chromosomes during the first meiotic division in triploids. Misorientation of spindles during the second meiotic division, such as fused and tripolar spindles with low frequency, could result in the formation of first meiotic division restitution (FDR)-type unreduced gametes, which most likely contain three complete chromosome sets. Although ‘Yinzhong’ yields 88.7% stainable pollen grains with wide diameter variation from 23.9 to 61.3 μm, the pollen viability is poor (2.78% ± 0.38). A cross of ‘Yinzhong’ pollen with a diploid female clone produced progeny with extensive segregation of ploidy levels, including 29 diploids, 18 triploids, 4 tetraploids, and 48 aneuploids, suggesting the formation of viable aneuploidy and unreduced pollen in ‘Yinzhong’. Individuals with different chromosome compositions are potential to analyze chromosomal function and to integrate the chromosomal dosage variation into breeding programs of Populus. PMID:28732039

Thirty years of Batten disease research: present status and future goals.

PubMed

Rider, J A; Rider, D L

1999-04-01

From a meager beginning in 1968, when Batten disease or neuronal ceroid lipofuscinosis was practically unheard of, tremendous advances have been made. It is now recognized worldwide as the most common neurodegenerative disease in children and young adults. It is recognized as a genetic disease. The infantile form has been localized to chromosome 1 p32 and the juvenile form, to 16p12.1; the gene for the late infantile is on chromosome 11p15 and for a variant form of the late infantile, the gene lies on chromosome 15q21-23. Finally, the molecular basis of the late infantile form is probably a pepstatin-insensitive lysomal peptidase. The future is to identify carriers, prevent the disease, and develop treatment by gene and enzyme replacement. Copyright 1999 Academic Press.

[Structural and functional organization of centromeres in plant chromosomes].

PubMed

Silkova, O G; Loginova, D B

2014-12-01

The centromere is a specific chromosomal locus that forms the protein complex and kinetochore, maintains sister chromatid cohesion, controls chromosome attachment to the spindle, and coordinates chromosome movement during mitosis and meiosis. Defective centromere assembly or its dysfunction causes cell cycle arrest, structural abnormalities of the chromosomes, and aneuploidy. This review collects the data on the structure, functions, and epigenetic modification of centromeric chromatin, the structure and functions of the kinetochore, and sister chromatid cohesion. Taken together, these data provide insight into the specific architecture and functioning of the centromere during chromosome division and segregation in plants.

DNA Secondary Structure at Chromosomal Fragile Sites in Human Disease

PubMed Central

Thys, Ryan G; Lehman, Christine E; Pierce, Levi C. T; Wang, Yuh-Hwa

2015-01-01

DNA has the ability to form a variety of secondary structures that can interfere with normal cellular processes, and many of these structures have been associated with neurological diseases and cancer. Secondary structure-forming sequences are often found at chromosomal fragile sites, which are hotspots for sister chromatid exchange, chromosomal translocations, and deletions. Structures formed at fragile sites can lead to instability by disrupting normal cellular processes such as DNA replication and transcription. The instability caused by disruption of replication and transcription can lead to DNA breakage, resulting in gene rearrangements and deletions that cause disease. In this review, we discuss the role of DNA secondary structure at fragile sites in human disease. PMID:25937814

Three-dimensional positioning and structure of chromosomes in a human prophase nucleus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Bo; Yusuf, Mohammed; Hashimoto, Teruo

The human genetic material is packaged into 46 chromosomes. The structure of chromosomes is known at the lowest level, where the DNA chain is wrapped around a core of eight histone proteins to form nucleosomes. Around a million of these nucleosomes, each about 11 nm in diameter and 6 nm in thickness, are wrapped up into the complex organelle of the chromosome, whose structure is mostly known at the level of visible light microscopy to form a characteristic cross shape in metaphase. However, the higher-order structure of human chromosomes, between a few tens and hundreds of nanometers, has not beenmore » well understood. We show a three-dimensional (3D) image of a human prophase nucleus obtained by serial block-face scanning electron microscopy, with 36 of the complete set of 46 chromosomes captured within it. The acquired image allows us to extract quantitative 3D structural information about the nucleus and the preserved, intact individual chromosomes within it, including their positioning and full spatial morphology at a resolution of around 50 nm in three dimensions. The chromosome positions were found, at least partially, to follow the pattern of chromosome territories previously observed only in interphase. The 3D conformation shows parallel, planar alignment of the chromatids, whose occupied volumes are almost fully accounted for by the DNA and known chromosomal proteins. Here, we also propose a potential new method of identifying human chromosomes in three dimensions, on the basis of the measurements of their 3D morphology.« less

Three-dimensional positioning and structure of chromosomes in a human prophase nucleus

DOE PAGES

Chen, Bo; Yusuf, Mohammed; Hashimoto, Teruo; ...

2017-07-21

The human genetic material is packaged into 46 chromosomes. The structure of chromosomes is known at the lowest level, where the DNA chain is wrapped around a core of eight histone proteins to form nucleosomes. Around a million of these nucleosomes, each about 11 nm in diameter and 6 nm in thickness, are wrapped up into the complex organelle of the chromosome, whose structure is mostly known at the level of visible light microscopy to form a characteristic cross shape in metaphase. However, the higher-order structure of human chromosomes, between a few tens and hundreds of nanometers, has not beenmore » well understood. We show a three-dimensional (3D) image of a human prophase nucleus obtained by serial block-face scanning electron microscopy, with 36 of the complete set of 46 chromosomes captured within it. The acquired image allows us to extract quantitative 3D structural information about the nucleus and the preserved, intact individual chromosomes within it, including their positioning and full spatial morphology at a resolution of around 50 nm in three dimensions. The chromosome positions were found, at least partially, to follow the pattern of chromosome territories previously observed only in interphase. The 3D conformation shows parallel, planar alignment of the chromatids, whose occupied volumes are almost fully accounted for by the DNA and known chromosomal proteins. Here, we also propose a potential new method of identifying human chromosomes in three dimensions, on the basis of the measurements of their 3D morphology.« less

Transient and Partial Nuclear Lamina Disruption Promotes Chromosome Movement in Early Meiotic Prophase.

PubMed

Link, Jana; Paouneskou, Dimitra; Velkova, Maria; Daryabeigi, Anahita; Laos, Triin; Labella, Sara; Barroso, Consuelo; Pacheco Piñol, Sarai; Montoya, Alex; Kramer, Holger; Woglar, Alexander; Baudrimont, Antoine; Markert, Sebastian Mathias; Stigloher, Christian; Martinez-Perez, Enrique; Dammermann, Alexander; Alsheimer, Manfred; Zetka, Monique; Jantsch, Verena

2018-04-23

Meiotic chromosome movement is important for the pairwise alignment of homologous chromosomes, which is required for correct chromosome segregation. Movement is driven by cytoplasmic forces, transmitted to chromosome ends by nuclear membrane-spanning proteins. In animal cells, lamins form a prominent scaffold at the nuclear periphery, yet the role lamins play in meiotic chromosome movement is unclear. We show that chromosome movement correlates with reduced lamin association with the nuclear rim, which requires lamin phosphorylation at sites analogous to those that open lamina network crosslinks in mitosis. Failure to remodel the lamina results in delayed meiotic entry, altered chromatin organization, unpaired or interlocked chromosomes, and slowed chromosome movement. The remodeling kinases are delivered to lamins via chromosome ends coupled to the nuclear envelope, potentially enabling crosstalk between the lamina and chromosomal events. Thus, opening the lamina network plays a role in modulating contacts between chromosomes and the nuclear periphery during meiosis. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Correction to: Whole chromosome painting reveals independent origin of sex chromosomes in closely related forms of a fish species.

PubMed

Cioffi, Marcelo de Bello; Sánchez, Antonio; Marchal, Juan Alberto; Kosyakova, Nadezda; Liehr, Thomas; Trifonov, Vladimir; Bertollo, Luiz Antonio Carlos

2018-02-01

ere, we report that a paragraph from the "Discussion" section of Cioffi et al. (2011; p. 1070, 4th paragraph of column 1) was transcribed (with only minor edits) from an introductory paragraph previously published in Chromosome Research by O'Meally et al.

Sexually Antagonistic Zygotic Drive: A New Form of Genetic Conflict between the Sex Chromosomes

PubMed Central

Friberg, Urban; Rice, William R.

2015-01-01

Sisters and brothers are completely unrelated with respect to the sex chromosomes they inherit from their heterogametic parent. This has the potential to result in a previously unappreciated form of genetic conflict between the sex chromosomes, called sexually antagonistic zygotic drive (SA-ZD). SA-ZD can arise whenever brothers and sisters compete over limited resources or there is brother–sister mating coupled with inbreeding depression. Although theory predicts that SA-ZD should be common and influence important evolutionary processes, there is little empirical evidence for its existence. Here we discuss the current understanding of SA-ZD, why it would be expected to elude empirical detection when present, and how it relates to other forms of genetic conflict. PMID:25573714

DNA intermediates and telomere addition during genome reorganization in Euplotes crassus.

PubMed

Roth, M; Prescott, D M

1985-06-01

Three gene-sized molecules cloned intact from macronuclear DNA served as hybridization probes to study excision of these molecules from chromosomes and their processing during macronuclear development in the hypotrich Euplotes crassus. These molecules occur in integrated forms within polytene chromosomal DNA during macronuclear developmental. After transection of the polytene chromosomes, the three molecules occur in intermediate forms. One of the three molecules first appeared in a large intermediate that was subsequently replaced by a second intermediate, approximately 140 bp larger than the final molecule. The other two macronuclear molecules were detected only in intermediates approximately 140 bp larger than the mature form. These penultimate intermediates are larger by virtue of oversized telomeres, which are pared to yield the mature gene-sized molecules.

Ambiguous Genitalia

MedlinePlus

... or disturb the fetus's developing sex organs. How sex organs form in the womb A baby's genetic sex is established at conception, based on the sex chromosomes. The mother's egg contains an X chromosome, ...

Chromosomal characteristics and distribution of rDNA sequences in the brook trout Salvelinus fontinalis (Mitchill, 1814).

PubMed

Śliwińska-Jewsiewicka, A; Kuciński, M; Kirtiklis, L; Dobosz, S; Ocalewicz, K; Jankun, Malgorzata

2015-08-01

Brook trout Salvelinus fontinalis (Mitchill, 1814) chromosomes have been analyzed using conventional and molecular cytogenetic techniques enabling characteristics and chromosomal location of heterochromatin, nucleolus organizer regions (NORs), ribosomal RNA-encoding genes and telomeric DNA sequences. The C-banding and chromosome digestion with the restriction endonucleases demonstrated distribution and heterogeneity of the heterochromatin in the brook trout genome. DNA sequences of the ribosomal RNA genes, namely the nucleolus-forming 28S (major) and non-nucleolus-forming 5S (minor) rDNAs, were physically mapped using fluorescence in situ hybridization (FISH) and primed in situ labelling. The minor rDNA locus was located on the subtelo-acrocentric chromosome pair No. 9, whereas the major rDNA loci were dispersed on 14 chromosome pairs, showing a considerable inter-individual variation in the number and location. The major and minor rDNA loci were located at different chromosomes. Multichromosomal location (3-6 sites) of the NORs was demonstrated by silver nitrate (AgNO3) impregnation. All Ag-positive i.e. active NORs corresponded to the GC-rich blocks of heterochromatin. FISH with telomeric probe showed the presence of the interstitial telomeric site (ITS) adjacent to the NOR/28S rDNA site on the chromosome 11. This ITS was presumably remnant of the chromosome rearrangement(s) leading to the genomic redistribution of the rDNA sequences. Comparative analysis of the cytogenetic data among several related salmonid species confirmed huge variation in the number and the chromosomal location of rRNA gene clusters in the Salvelinus genome.

Spatial arrangement of chromosomes in oocytes and spermatocytes of malaria mosquitoes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stegnii, V.N.; Vasserlauf, I.E.

It is shown that prophase chromosomes of oocytes in Anopheles messeae ovaries do not form local chromocenters, unlike spermatocytes, in which chromosomes fuse in a joint centromeric assembly. This fact reflects the dynamic nature of the system of chromocenter formation in generative tissues. During analysis of interspecific hybrids F{sub 1} A. maculipennis x A. subalpinus, no conjunction of homeologous chromosomes was observed, and the latter remained separated from one another. 6 refs., 1 fig.

Large-scale polymorphism near the ends of several human chromosomes analyzed by using fluorescence in situ hybridization (FISH)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trask, B.J.; Friedman, C.; Giorgi, D.

1994-09-01

We have discovered a large DNA segment that is polymorphically present at the ends of several human chromosomes. The segment, f7501, was originally derived form a human chromosome 19-specific cosmid library. FISH was used to determine the cosmid`s chromosomal distribution on 44 unrelated humans and several closely related primates. The human subjects represent a diversity of reproductively isolated ethnic populations. FISH analysis revealed that sequences highly homologous to the cosmid`s insert are present on both homologs at 3q, 15q,. and 19p in almost all individuals (88, 85, and 87 of 88 homologs, respectively). Other chromosomes sites were labeled much moremore » rarely in the sampled individuals. For example, 56 of the 88 analyzed chromosomes 11 were labeled (18+/+, 6-/-, and 20+/- individuals). In contrast, 2q was labeled on only 1/88 sampled chromosomes. The termini of 2q, 5q, 6p, 6q, 7p, 8p, 9p, 9q, 11p, 12q, 16p, 19q, and 20q and an interstitial site at 2q13-14 were labeled in at least one individual of the set. EcoR1-fragments derived from the cosmid showed the same hybridization pattern as the entire cosmid, indicating that at least 40 kbp is shared by these chromosome ends. Ethnic differences in the allele frequency of these polymorphic variants was observed. For example, signals were observed on 8/10 and 7/10 of the chromosomes 7p and 16q, respectively, derived form Biakan Pygmies, but these sites were infrequently labeled in non-Pygmy human populations (2/68, respectively). This region has undergone significant changes in chromosome location during human evolution. Strong signal was seen on chimpanzee and gorilla chromosome 3, which is homologous to human chromosome 4, a chromosome unlabeled in any of the humans we have analyzed.« less

A New Integrative Conjugative Element Occurs in Mycoplasma agalactiae as Chromosomal and Free Circular Forms

PubMed Central

Marenda, Marc; Barbe, Valérie; Gourgues, Géraldine; Mangenot, Sophie; Sagne, Evelyne; Citti, Christine

2006-01-01

An integrative conjugative element, ICEA, was characterized in Mycoplasma agalactiae strain 5632, in which it occurs as multiple chromosomal copies and as a free circular form. The distribution of ICEA sequences in M. agalactiae strains and their occurrence in Mycoplasma bovis suggest the spreading of the element within or between species. PMID:16707706

Centromere Pairing in Early Meiotic Prophase Requires Active Centromeres and Precedes Installation of the Synaptonemal Complex in Maize[W

PubMed Central

Zhang, Jing; Pawlowski, Wojciech P.; Han, Fangpu

2013-01-01

Pairing of homologous chromosomes in meiosis is critical for their segregation to daughter cells. In most eukaryotes, clustering of telomeres precedes and facilitates chromosome pairing. In several species, centromeres also form pairwise associations, known as coupling, before the onset of pairing. We found that, in maize (Zea mays), centromere association begins at the leptotene stage and occurs earlier than the formation of the telomere bouquet. We established that centromere pairing requires centromere activity and the sole presence of centromeric repeats is not sufficient for pairing. In several species, homologs of the ZIP1 protein, which forms the central element of the synaptonemal complex in budding yeast (Saccharomyces cerevisiae), play essential roles in centromere coupling. However, we found that the maize ZIP1 homolog ZYP1 installs in the centromeric regions of chromosomes after centromeres form associations. Instead, we found that maize STRUCTURAL MAINTENANCE OF CHROMOSOMES6 homolog forms a central element of the synaptonemal complex, which is required for centromere associations. These data shed light on the poorly understood mechanism of centromere interactions and suggest that this mechanism may vary somewhat in different species. PMID:24143803

Centromere pairing in early meiotic prophase requires active centromeres and precedes installation of the synaptonemal complex in maize.

PubMed

Zhang, Jing; Pawlowski, Wojciech P; Han, Fangpu

2013-10-01

Pairing of homologous chromosomes in meiosis is critical for their segregation to daughter cells. In most eukaryotes, clustering of telomeres precedes and facilitates chromosome pairing. In several species, centromeres also form pairwise associations, known as coupling, before the onset of pairing. We found that, in maize (Zea mays), centromere association begins at the leptotene stage and occurs earlier than the formation of the telomere bouquet. We established that centromere pairing requires centromere activity and the sole presence of centromeric repeats is not sufficient for pairing. In several species, homologs of the ZIP1 protein, which forms the central element of the synaptonemal complex in budding yeast (Saccharomyces cerevisiae), play essential roles in centromere coupling. However, we found that the maize ZIP1 homolog ZYP1 installs in the centromeric regions of chromosomes after centromeres form associations. Instead, we found that maize structural maintenance of chromosomes6 homolog forms a central element of the synaptonemal complex, which is required for centromere associations. These data shed light on the poorly understood mechanism of centromere interactions and suggest that this mechanism may vary somewhat in different species.

Phylogenomics of African guenons.

PubMed

Moulin, Sibyle; Gerbault-Seureau, Michèle; Dutrillaux, Bernard; Richard, Florence Anne

2008-01-01

The karyotypes of 28 specimens belonging to 26 species of Cercopithecinae have been compared with each other and with human karyotype by chromosome banding and, for some of them, by Zoo-FISH (human painting probes) techniques. The study includes the first description of the karyotypes of four species and a synonym of Cercopithecus nictitans. The chromosomal homologies obtained provide us with new data on a large number of rearrangements. This allows us to code chromosomal characters to draw Cercopithecini phylogenetic trees, which are compared to phylogenetic data based on DNA sequences. Our findings show that some of the superspecies proposed by Kingdon (1997 The Kingdon Field Guide to African Mammals, Academic Press.) and Groves (2001 Primates Taxonomy, Smithsonian Institution Press) do not form homogeneous groups and that the genus Cercopithecus is paraphyletic, in agreement with previous molecular analyses. The evolution of Cercopithecini karyotypes is mainly due to non-centromeric chromosome fissions and centromeric shifts or inversions. Non-Robertsonian translocations occurred in C. hamlyni and C. neglectus. The position of chromosomal rearrangements in the phylogenetic tree leads us to propose that the Cercopithecini evolution proceeded by either repeated fission events facilitated by peculiar genomic structures or successive reticulate phases, in which heterozygous populations for few rearranged chromosomes were present, allowing the spreading of chromosomal forms in various combinations, before the speciation process.

Micromanipulation studies of chromosome movement. II. Birefringent chromosomal fibers and the mechanical attachment of chromosomes to the spindle

PubMed Central

1979-01-01

The degree of mechanical coupling of chromosomes to the spindles of Nephrotoma and Trimeratropis primary spermatocytes varies with the stage of meiosis and the birefringent retardation of the chromosomal fibers. In early prometaphase, before birefringent chromosomal fibers have formed, a bivalent can be displaced toward a spindle pole by a single, continuous pull with a microneedle. Resistance to poleward displacement increases with increased development of the chromosomal fibers, reaching a maximum at metaphase. At this stage kinetochores cannot be displaced greater than 1 micrometer toward either spindle pole, even by a force which is sufficient to displace the entire spindle within the cell. The abolition of birefringence with either colcemid or vinblastine results in the loss of chromosome-spindle attachment. In the absence of birefringent fibers a chromosome can be displaced anywhere within the cell. The photochemical inactivation of colcemid by irradiation with 366-nm light results in the reformation of birefringent chromosomal fibers and the concomitant re-establishment of chromosome attachment to the spindle. These results support the hypothesis that the birefringent chromosomal fibers anchor the chromosomes to the spindle and transmit the force for anaphase chromosome movement. PMID:479316

Interdependency and phosphorylation of KIF4 and condensin I are essential for organization of chromosome scaffold.

PubMed

Poonperm, Rawin; Takata, Hideaki; Uchiyama, Susumu; Fukui, Kiichi

2017-01-01

Kinesin family member 4 (KIF4) and condensins I and II are essential chromosomal proteins for chromosome organization by locating primarily to the chromosome scaffold. However, the mechanism of how KIF4 and condensins localize to the chromosome scaffold is poorly understood. Here, we demonstrate a close relationship between the chromosome localization of KIF4 and condensin I, but not condensin II, and show that KIF4 and condensin I assist each other for stable scaffold formation by forming a stable complex. Moreover, phosphorylation of KIF4 and condensin I by Aurora B and polo-like kinase 1 (Plk1) is important for KIF4 and condensin I localization to the chromosome. Aurora B activity facilitates the targeting of KIF4 and condensin I to the chromosome, whereas Plk1 activity promotes the dissociation of these proteins from the chromosome. Thus, the interdependency between KIF4 and condensin I, and their phosphorylation states play important roles in chromosome scaffold organization during mitosis.

Interdependency and phosphorylation of KIF4 and condensin I are essential for organization of chromosome scaffold

PubMed Central

Uchiyama, Susumu; Fukui, Kiichi

2017-01-01

Kinesin family member 4 (KIF4) and condensins I and II are essential chromosomal proteins for chromosome organization by locating primarily to the chromosome scaffold. However, the mechanism of how KIF4 and condensins localize to the chromosome scaffold is poorly understood. Here, we demonstrate a close relationship between the chromosome localization of KIF4 and condensin I, but not condensin II, and show that KIF4 and condensin I assist each other for stable scaffold formation by forming a stable complex. Moreover, phosphorylation of KIF4 and condensin I by Aurora B and polo-like kinase 1 (Plk1) is important for KIF4 and condensin I localization to the chromosome. Aurora B activity facilitates the targeting of KIF4 and condensin I to the chromosome, whereas Plk1 activity promotes the dissociation of these proteins from the chromosome. Thus, the interdependency between KIF4 and condensin I, and their phosphorylation states play important roles in chromosome scaffold organization during mitosis. PMID:28817632

Platypus chain reaction: directional and ordered meiotic pairing of the multiple sex chromosome chain in Ornithorhynchus anatinus.

PubMed

Daish, Tasman; Casey, Aaron; Grützner, Frank

2009-01-01

Monotremes are phylogenetically and phenotypically unique animals with an unusually complex sex chromosome system that is composed of ten chromosomes in platypus and nine in echidna. These chromosomes are alternately linked (X1Y1, X2Y2, ...) at meiosis via pseudoautosomal regions and segregate to form spermatozoa containing either X or Y chromosomes. The physical and epigenetic mechanisms involved in pairing and assembly of the complex sex chromosome chain in early meiotic prophase I are completely unknown. We have analysed the pairing dynamics of specific sex chromosome pseudoautosomal regions in platypus spermatocytes during prophase of meiosis I. Our data show a highly coordinated pairing process that begins at the terminal Y5 chromosome and completes with the union of sex chromosomes X1Y1. The consistency of this ordered assembly of the chain is remarkable and raises questions about the mechanisms and factors that regulate the differential pairing of sex chromosomes and how this relates to potential meiotic silencing mechanisms and alternate segregation.

Topology, structures, and energy landscapes of human chromosomes

PubMed Central

Zhang, Bin; Wolynes, Peter G.

2015-01-01

Chromosome conformation capture experiments provide a rich set of data concerning the spatial organization of the genome. We use these data along with a maximum entropy approach to derive a least-biased effective energy landscape for the chromosome. Simulations of the ensemble of chromosome conformations based on the resulting information theoretic landscape not only accurately reproduce experimental contact probabilities, but also provide a picture of chromosome dynamics and topology. The topology of the simulated chromosomes is probed by computing the distribution of their knot invariants. The simulated chromosome structures are largely free of knots. Topologically associating domains are shown to be crucial for establishing these knotless structures. The simulated chromosome conformations exhibit a tendency to form fibril-like structures like those observed via light microscopy. The topologically associating domains of the interphase chromosome exhibit multistability with varying liquid crystalline ordering that may allow discrete unfolding events and the landscape is locally funneled toward “ideal” chromosome structures that represent hierarchical fibrils of fibrils. PMID:25918364

Variant forms of ataxia telangiectasia.

PubMed Central

Taylor, A M; Flude, E; Laher, B; Stacey, M; McKay, E; Watt, J; Green, S H; Harding, A E

1987-01-01

Two ataxia telangiectasia patients with unusual clinical and cellular features are described. Cultured fibroblasts and PHA stimulated lymphocytes from these two patients showed a smaller increase of radiosensitivity than cells from other A-T patients, as measured by colony forming ability or induced chromosome damage respectively, after exposure to ionising radiation. The response of DNA synthesis to irradiation of these cells was, however, the same as for other A-T patients. Cells from a third patient with some clinical features of A-T but with a very protracted course also showed low levels of radiation induced chromosome damage, but colony forming ability and the response of DNA synthesis after irradiation were no different from cells of normal subjects. There was, however, an increased level of translocations and unstable chromosomal rearrangements in this patient's lymphocytes. Images PMID:3430541

Neocentromeres and epigenetically inherited features of centromeres

PubMed Central

Burrack, Laura S.; Berman, Judith

2012-01-01

Neocentromeres are ectopic sites where new functional kinetochores assemble and permit chromosome segregation. Neocentromeres usually form following genomic alterations that remove or disrupt centromere function. The ability to form neocentromeres is conserved in eukaryotes ranging from fungi to mammals. Neocentromeres that rescue chromosome fragments in cells with gross chromosomal rearrangements are found in several types of human cancers, and in patients with developmental disabilities. In this review, we discuss the importance of neocentromeres to human health and evaluate recently developed model systems to study neocentromere formation, maintenance, and function in chromosome segregation. Additionally, studies of neocentromeres provide insight into native centromeres; analysis of neocentromeres found in human clinical samples and induced in model organisms distinguishes features of centromeres that are dependent on centromere DNA from features that are epigenetically inherited together with the formation of a functional kinetochore. PMID:22723125

A test of the chromosomal theory of ecotypic speciation in Anopheles gambiae

PubMed Central

Manoukis, Nicholas C.; Powell, Jeffrey R.; Touré, Mahamoudou B.; Sacko, Adama; Edillo, Frances E.; Coulibaly, Mamadou B.; Traoré, Sekou F.; Taylor, Charles E.; Besansky, Nora J.

2008-01-01

The role of chromosomal inversions in speciation has long been of interest to evolutionists. Recent quantitative modeling has stimulated reconsideration of previous conceptual models for chromosomal speciation. Anopheles gambiae, the most important vector of human malaria, carries abundant chromosomal inversion polymorphism nonrandomly associated with ecotypes that mate assortatively. Here, we consider the potential role of paracentric inversions in promoting speciation in A. gambiae via “ecotypification,” a term that refers to differentiation arising from local adaptation. In particular, we focus on the Bamako form, an ecotype characterized by low inversion polymorphism and fixation of an inversion, 2Rj, that is very rare or absent in all other forms of A. gambiae. The Bamako form has a restricted distribution by the upper Niger River and its tributaries that is associated with a distinctive type of larval habitat, laterite rock pools, hypothesized to be its optimal breeding site. We first present computer simulations to investigate whether the population dynamics of A. gambiae are consistent with chromosomal speciation by ecotypification. The models are parameterized using field observations on the various forms of A. gambiae that exist in Mali, West Africa. We then report on the distribution of larvae of this species collected from rock pools and more characteristic breeding sites nearby. Both the simulations and field observations support the thesis that speciation by ecotypification is occurring, or has occurred, prompting consideration of Bamako as an independent species. PMID:18287019

Human Autoantibodies Reveal Titin as a Chromosomal Protein

PubMed Central

Machado, Cristina; Sunkel, Claudio E.; Andrew, Deborah J.

1998-01-01

Assembly of the higher-order structure of mitotic chromosomes is a prerequisite for proper chromosome condensation, segregation and integrity. Understanding the details of this process has been limited because very few proteins involved in the assembly of chromosome structure have been discovered. Using a human autoimmune scleroderma serum that identifies a chromosomal protein in human cells and Drosophila embryos, we cloned the corresponding Drosophila gene that encodes the homologue of vertebrate titin based on protein size, sequence similarity, developmental expression and subcellular localization. Titin is a giant sarcomeric protein responsible for the elasticity of striated muscle that may also function as a molecular scaffold for myofibrillar assembly. Molecular analysis and immunostaining with antibodies to multiple titin epitopes indicates that the chromosomal and muscle forms of titin may vary in their NH2 termini. The identification of titin as a chromosomal component provides a molecular basis for chromosome structure and elasticity. PMID:9548712

Kid-mediated chromosome compaction ensures proper nuclear envelope formation.

PubMed

Ohsugi, Miho; Adachi, Kenjiro; Horai, Reiko; Kakuta, Shigeru; Sudo, Katsuko; Kotaki, Hayato; Tokai-Nishizumi, Noriko; Sagara, Hiroshi; Iwakura, Yoichiro; Yamamoto, Tadashi

2008-03-07

Toward the end of mitosis, neighboring chromosomes gather closely to form a compact cluster. This is important for reassembling the nuclear envelope around the entire chromosome mass but not individual chromosomes. By analyzing mice and cultured cells lacking the expression of chromokinesin Kid/kinesin-10, we show that Kid localizes to the boundaries of anaphase and telophase chromosomes and contributes to the shortening of the anaphase chromosome mass along the spindle axis. Loss of Kid-mediated anaphase chromosome compaction often causes the formation of multinucleated cells, specifically at oocyte meiosis II and the first couple of mitoses leading to embryonic death. In contrast, neither male meiosis nor somatic mitosis after the morula-stage is affected by Kid deficiency. These data suggest that Kid-mediated anaphase/telophase chromosome compaction prevents formation of multinucleated cells. This protection is especially important during the very early stages of development, when the embryonic cells are rich in ooplasm.

The larvicidal effects of black pepper (Piper nigrum L.) and piperine against insecticide resistant and susceptible strains of Anopheles malaria vector mosquitoes.

PubMed

Samuel, Michael; Oliver, Shüné V; Coetzee, Maureen; Brooke, Basil D

2016-04-26

Insecticide resistance carries the potential to undermine the efficacy of insecticide based malaria vector control strategies. Therefore, there is an urgent need for new insecticidal compounds. Black pepper (dried fruit from the vine, Piper nigrum), used as a food additive and spice, and its principal alkaloid piperine, have previously been shown to have larvicidal properties. The aim of this study was to investigate the larvicidal effects of ground black pepper and piperine against third and fourth instar Anopheles larvae drawn from several laboratory-reared insecticide resistant and susceptible strains of Anopheles arabiensis, An. coluzzii, An. gambiae, An. quadriannulatus and An. funestus. Larvae were fed with mixtures of standard larval food and either ground black pepper or piperine in different proportions. Mortality was recorded 24 h after black pepper and 48 h after piperine were applied to the larval bowls. Black pepper and piperine mixtures caused high mortality in the An. gambiae complex strains, with black pepper proving significantly more toxic than piperine. The An. funestus strains were substantially less sensitive to black pepper and piperine which may reflect a marked difference in the feeding habits of this species compared to that of the Gambiae complex or a difference in food metabolism as a consequence of differences in breeding habitat between species. Insecticide resistant and susceptible strains by species proved equally susceptible to black pepper and piperine. It is concluded that black pepper shows potential as a larvicide for the control of certain malaria vector species.

Lymphatic filariasis in Uganda: baseline investigations in Lira, Soroti and Katakwi districts.

PubMed

Onapa, A W; Simonsen, P E; Pedersen, E M; Okello, D O

2001-01-01

Baseline epidemiological investigations on lymphatic filariasis were conducted for the first time in Uganda in 3 communities in the districts of Lira (Alebtong area), Soroti (Lwala area) and Katakwi (Obalanga area), located to the north of Lake Kyoga at an altitude of 1000-1100 m above sea level. Individuals from the communities were examined, in April-August 1998, for Wuchereria bancrofti specific circulating antigen (by ICT card test), microfilaraemia (by counting chamber and stained blood-smear techniques) and chronic clinical manifestations of lymphatic filariasis. Endophilic mosquitoes were sampled and dissected for filarial larvae. Prevalences of circulating filarial antigen positivity were 29%, 18% and 30% in the Alebtong, Lwala and Obalanga communities, respectively. Microfilaria (mf) prevalences were 18%, 9% and 21%, and geometric mean mf intensities among mf-positive individuals were 306, 171 and 402 mf/mL blood, in the same communities. Examination of stained blood smears revealed mf of both W. bancrofti and Mansonella perstans, but more than 80% of mf-positive individuals harboured the first of these parasites. Prevalences of hydrocoele in adult (> or = 20 years) males were 28%, 7% and 17%, and prevalences of limb elephantiasis in adults were 9%, 4% and 4%, in the Alebtong, Lwala and Obalanga communities, respectively. Anopheles gambiae s.l. (mainly An. gambiae s.s.) and An. funestus were common in all 3 communities, and showed W. bancrofti infectivity rates of 1.1-1.7% and 1.3-2.9%, respectively. It is concluded that lymphatic filariasis is highly endemic in these high-altitude areas of Uganda, with An. gambiae s.l. and An. funestus being the main vectors.

Translocations of chromosome end-segments and facultative heterochromatin promote meiotic ring formation in evening primroses.

PubMed

Golczyk, Hieronim; Massouh, Amid; Greiner, Stephan

2014-03-01

Due to reciprocal chromosomal translocations, many species of Oenothera (evening primrose) form permanent multichromosomal meiotic rings. However, regular bivalent pairing is also observed. Chiasmata are restricted to chromosomal ends, which makes homologous recombination virtually undetectable. Genetic diversity is achieved by changing linkage relations of chromosomes in rings and bivalents via hybridization and reciprocal translocations. Although the structural prerequisite for this system is enigmatic, whole-arm translocations are widely assumed to be the mechanistic driving force. We demonstrate that this prerequisite is genome compartmentation into two epigenetically defined chromatin fractions. The first one facultatively condenses in cycling cells into chromocenters negative both for histone H3 dimethylated at lysine 4 and for C-banding, and forms huge condensed middle chromosome regions on prophase chromosomes. Remarkably, it decondenses in differentiating cells. The second fraction is euchromatin confined to distal chromosome segments, positive for histone H3 lysine 4 dimethylation and for histone H3 lysine 27 trimethylation. The end-segments are deprived of canonical telomeres but capped with constitutive heterochromatin. This genomic organization promotes translocation breakpoints between the two chromatin fractions, thus facilitating exchanges of end-segments. We challenge the whole-arm translocation hypothesis by demonstrating why reciprocal translocations of chromosomal end-segments should strongly promote meiotic rings and evolution toward permanent translocation heterozygosity. Reshuffled end-segments, each possessing a major crossover hot spot, can furthermore explain meiotic compatibility between genomes with different translocation histories.

Translocations of Chromosome End-Segments and Facultative Heterochromatin Promote Meiotic Ring Formation in Evening Primroses[W][OPEN

PubMed Central

Golczyk, Hieronim; Massouh, Amid; Greiner, Stephan

2014-01-01

Due to reciprocal chromosomal translocations, many species of Oenothera (evening primrose) form permanent multichromosomal meiotic rings. However, regular bivalent pairing is also observed. Chiasmata are restricted to chromosomal ends, which makes homologous recombination virtually undetectable. Genetic diversity is achieved by changing linkage relations of chromosomes in rings and bivalents via hybridization and reciprocal translocations. Although the structural prerequisite for this system is enigmatic, whole-arm translocations are widely assumed to be the mechanistic driving force. We demonstrate that this prerequisite is genome compartmentation into two epigenetically defined chromatin fractions. The first one facultatively condenses in cycling cells into chromocenters negative both for histone H3 dimethylated at lysine 4 and for C-banding, and forms huge condensed middle chromosome regions on prophase chromosomes. Remarkably, it decondenses in differentiating cells. The second fraction is euchromatin confined to distal chromosome segments, positive for histone H3 lysine 4 dimethylation and for histone H3 lysine 27 trimethylation. The end-segments are deprived of canonical telomeres but capped with constitutive heterochromatin. This genomic organization promotes translocation breakpoints between the two chromatin fractions, thus facilitating exchanges of end-segments. We challenge the whole-arm translocation hypothesis by demonstrating why reciprocal translocations of chromosomal end-segments should strongly promote meiotic rings and evolution toward permanent translocation heterozygosity. Reshuffled end-segments, each possessing a major crossover hot spot, can furthermore explain meiotic compatibility between genomes with different translocation histories. PMID:24681616

Genetic mapping of a locus for multiple ephiphyseal dysplasia (EDM2) to a region of chromosome 1 containing a type IX collagen gene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Briggs, M.D.; Choi, HiChang; Warman, M.L.

1994-10-01

Multiple epiphyseal dysplasia (MED) is a dominantly inherited chondrodysplasia characterized by mild short stature and early-onset osteoarthrosis. Some forms of MED clinically resemble another chondrodysplasia phenotype, the mild form of pseudoachondroplasia (PSACH). On the basis of their clinical similarities as well as similar ultra-structural and biochemical features in cartilage from some patients, it has been proposed that MED and PSACH belong to a single bone-dysplasia family. Recently, both mild and severe PSACH as well as a form of MED have been linked to the same interval on chromosome 19, suggesting that they may be allelic disorders. Linkage studies with themore » chromosome 19 markers were carried out in a large family with MED and excluded the previously identified interval. Using this family, we have identified a MED locus on the short arm of chromosome 1, in a region containing the gene (COL9A2) that encodes the {alpha}2 chain of type IX collagen, a structural component of the cartilage extracellular matrix. 39 refs., 3 figs., 3 tabs.« less

Exceptional Chromosomal Evolution and Cryptic Speciation of Blind Mole Rats Nannospalax leucodon (Spalacinae, Rodentia) from South-Eastern Europe.

PubMed

Savić, Ivo; Ćirović, Duško; Bugarski-Stanojević, Vanja

2017-10-25

Mole rats are exclusively subterranean and highly specialized rodents. Their long lifespans, remarkable anti-cancer mechanisms, and various distinctive adaptive features make them a useful research model. Moreover, opposing convergence of morphological traits, they have developed extremely high karyotype variability. Thus, 74 chromosomal forms have been described so far and new ones are being revealed continuously. These evolved during the process of rapid radiation and occur in different biogeographical regions. During research into their reproductive biology we have already provided substantial evidence for species-level separation of these taxa. Here, we review diverse chromosomal forms of the lesser blind mole rat, Mediterranean Nannospalax leucodon , distributed in South-eastern Europe, their karyotype records, biogeography, origin, and phylogeny from our extensive research. In the light of new data from molecular genetic studies, we question some former valuations and propose a cryptospecies rank for seven reproductively isolated chromosomal forms with sympatric and parapatric distribution and clear ecogeographical discrepances in their habitats, as well as new experimental and theoretical methods for understanding the courses of speciation of these unique fossorial mammals.

Exceptional Chromosomal Evolution and Cryptic Speciation of Blind Mole Rats Nannospalax leucodon (Spalacinae, Rodentia) from South-Eastern Europe

PubMed Central

Savić, Ivo; Ćirović, Duško

2017-01-01

Mole rats are exclusively subterranean and highly specialized rodents. Their long lifespans, remarkable anti-cancer mechanisms, and various distinctive adaptive features make them a useful research model. Moreover, opposing convergence of morphological traits, they have developed extremely high karyotype variability. Thus, 74 chromosomal forms have been described so far and new ones are being revealed continuously. These evolved during the process of rapid radiation and occur in different biogeographical regions. During research into their reproductive biology we have already provided substantial evidence for species-level separation of these taxa. Here, we review diverse chromosomal forms of the lesser blind mole rat, Mediterranean Nannospalax leucodon, distributed in South-eastern Europe, their karyotype records, biogeography, origin, and phylogeny from our extensive research. In the light of new data from molecular genetic studies, we question some former valuations and propose a cryptospecies rank for seven reproductively isolated chromosomal forms with sympatric and parapatric distribution and clear ecogeographical discrepances in their habitats, as well as new experimental and theoretical methods for understanding the courses of speciation of these unique fossorial mammals. PMID:29068425

Plasmid Characterization and Chromosome Analysis of Two netF+ Clostridium perfringens Isolates Associated with Foal and Canine Necrotizing Enteritis.

PubMed

Mehdizadeh Gohari, Iman; Kropinski, Andrew M; Weese, Scott J; Parreira, Valeria R; Whitehead, Ashley E; Boerlin, Patrick; Prescott, John F

2016-01-01

The recent discovery of a novel beta-pore-forming toxin, NetF, which is strongly associated with canine and foal necrotizing enteritis should improve our understanding of the role of type A Clostridium perfringens associated disease in these animals. The current study presents the complete genome sequence of two netF-positive strains, JFP55 and JFP838, which were recovered from cases of foal necrotizing enteritis and canine hemorrhagic gastroenteritis, respectively. Genome sequencing was done using Single Molecule, Real-Time (SMRT) technology-PacBio and Illumina Hiseq2000. The JFP55 and JFP838 genomes include a single 3.34 Mb and 3.53 Mb chromosome, respectively, and both genomes include five circular plasmids. Plasmid annotation revealed that three plasmids were shared by the two newly sequenced genomes, including a NetF/NetE toxins-encoding tcp-conjugative plasmid, a CPE/CPB2 toxins-encoding tcp-conjugative plasmid and a putative bacteriocin-encoding plasmid. The putative beta-pore-forming toxin genes, netF, netE and netG, were located in unique pathogenicity loci on tcp-conjugative plasmids. The C. perfringens JFP55 chromosome carries 2,825 protein-coding genes whereas the chromosome of JFP838 contains 3,014 protein-encoding genes. Comparison of these two chromosomes with three available reference C. perfringens chromosome sequences identified 48 (~247 kb) and 81 (~430 kb) regions unique to JFP55 and JFP838, respectively. Some of these divergent genomic regions in both chromosomes are phage- and plasmid-related segments. Sixteen of these unique chromosomal regions (~69 kb) were shared between the two isolates. Five of these shared regions formed a mosaic of plasmid-integrated segments, suggesting that these elements were acquired early in a clonal lineage of netF-positive C. perfringens strains. These results provide significant insight into the basis of canine and foal necrotizing enteritis and are the first to demonstrate that netF resides on a large and unique plasmid-encoded locus.

[Inverted meiosis and its place in the evolution of sexual reproduction pathways].

PubMed

Bogdanov, Yu F

2016-05-01

Inverted meiosis is observed in plants (Cyperaceae and Juncaceae) and insects (Coccoidea, Aphididae) with holocentric chromosomes, the centromeres of which occupy from 70 to 90% of the metaphase chromosome length. In the first meiotic division (meiosis I), chiasmata are formed and rodlike bivalents orient equationally, and in anaphase I, sister chromatids segregate to the poles; the diploid chromosome number is maintained. Non-sister chromatids of homologous chromosomes remain in contact during interkinesis and prophase II and segregate in anaphase II, forming haploid chromosome sets. The segregation of sister chromatids in meiosis I was demonstrated by example of three plant species that were heterozygous for chromosomal rearrangements. In these species, sister chromatids, marked with rearrangement, segregated in anaphase I. Using fluorescent antibodies, it was demonstrated that meiotic recombination enzymes Spo11 and Rad5l, typical of canonical meiosis, functioned at the meiotic prophase I of pollen mother cells of Luzula elegance and Rhynchospora pubera. Moreover, antibodies to synaptonemal complexes proteins ASY1 and ZYP1 were visualized as filamentous structures, pointing to probable formation of synaptonemal complexes. In L. elegance, chiasmata are formed by means of chromatin threads containing satellite DNA. According to the hypothesis of the author of this review, equational division of sister chromatids at meiosis I in the organisms with inverted meiosis can be explained by the absence of specific meiotic proteins (shugoshins). These proteins are able to protect cohesins of holocentric centromeres from hydrolysis by separases at meiosis I, as occurs in the organisms with monocentric chromosomes and canonical meiosis. The basic type of inverted meiosis was described in Coccoidea and Aphididae males. In their females, the variants of parthenogenesis were also observed. Until now, the methods of molecular cytogenetics were not applied for the analysis of inverted meiosis in Coccoidea and Aphididae. Evolutionary, inverted meiosis is thought to have appeared secondarily as an adaptation of the molecular mechanisms of canonical meiosis to chromosome holocentrism.

[Genetic polymorphism of flax Linum usitatissimum based on use of molecular cytogenetic markers].

PubMed

Rachinskaia, O A; Lemesh, V A; Muravenko, O V; Iurkevich, O Iu; Guzenko, E V; Bol'sheva, N L; Bogdanova, M V; Samatadze, T E; Popov, K V; Malyshev, S V; Shostak, N G; Heller, K; Khotyleva, L V; Zelenin, A V

2011-01-01

Using a set of approaches based on the use of molecular cytogenetic markers (DAPI/C-banding, estimation of the total area of DAPI-positive regions in prophase nuclei, FISH with 26S and 5S rDNA probes) and the microsatellite (SSR-PCR) assay, we studied genomic polymorphism in 15 flax (Linum usitatissimum L.) varieties from different geographic regions belonging to three directions of selection (oil, fiber, and intermediate flaxes) and in the k-37 x Viking hybrid. All individual chromosomes have been identified in the karyotypes of these varieties on the basis of the patterns of differential DAPI/C-banding and the distribution of 26S and 5S rDNA, and idiograms of the chromosomes have been generated. Unlike the oil flax varieties, the chromosomes in the karyotypes of the fiber flax varieties have, as a rule, pericentromeric and telomeric DAPI-positive bands of smaller size, but contain larger intercalary regions. Two chromosomal rearrangements (chromosome 3 inversions) were discovered in the variety Luna and in the k-37 x Viking hybrid. In both these forms, no colocalization of 26S rDNA and 5S rDNA on the satellite chromosome was detected. The SSR assay with the use of 20 polymorphic pairs of primers revealed 22 polymorphic loci. Based on the SSR data, we analyzed genetic similarity of the flax forms studied and constructed a genetic similarity dendrogram. The genotypes studied here form three clusters. The oil varieties comprise an independent cluster. The genetically related fiber flax varieties Vita and Luna, as well as the landrace Lipinska XIII belonging to the intermediate type, proved to be closer to the oil varieties than the remaining fiber flax varieties. The results of the molecular chromosomal analysis in the fiber and oil flaxes confirm their very close genetic similarity. In spite of this, the combined use of the chromosomal and molecular markers has opened up unique possibilities for describing the genotypes of flax varieties and creating their genetic passports.

Evolutionary interaction between W/Y chromosome and transposable elements.

PubMed

Śliwińska, Ewa B; Martyka, Rafał; Tryjanowski, Piotr

2016-06-01

The W/Y chromosome is unique among chromosomes as it does not recombine in its mature form. The main side effect of cessation of recombination is evolutionary instability and degeneration of the W/Y chromosome, or frequent W/Y chromosome turnovers. Another important feature of W/Y chromosome degeneration is transposable element (TEs) accumulation. Transposon accumulation has been confirmed for all W/Y chromosomes that have been sequenced so far. Models of W/Y chromosome instability include the assemblage of deleterious mutations in protein coding genes, but do not include the influence of transposable elements that are accumulated gradually in the non-recombining genome. The multiple roles of genomic TEs, and the interactions between retrotransposons and genome defense proteins are currently being studied intensively. Small RNAs originating from retrotransposon transcripts appear to be, in some cases, the only mediators of W/Y chromosome function. Based on the review of the most recent publications, we present knowledge on W/Y evolution in relation to retrotransposable element accumulation.

Structural maintenance of chromosome complexes differentially compact mitotic chromosomes according to genomic context

PubMed Central

Schalbetter, S. A.; Goloborodko, A.; Fudenberg, G.; Belton, J.-M.; Miles, C.; Yu, M.; Dekker, J.; Mirny, L.; Baxter, J.

2017-01-01

Structural Maintenance of Chromosomes (SMC) protein complexes are key determinants of chromosome conformation. Using Hi-C and polymer modeling, we study how cohesin and condensin, two deeply conserved SMC complexes, organize chromosomes in the budding yeast Saccharomyces cerevisiae. The canonical role of cohesin is to co-align sister chromatids whilst condensin generally compacts mitotic chromosomes. We find strikingly different roles for the two complexes in budding yeast mitosis. First, cohesin is responsible for compacting mitotic chromosome arms, independently of sister chromatid cohesion. Polymer simulations demonstrate this role can be fully accounted for through cis-looping of chromatin. Second, condensin is generally dispensable for compaction along chromosome arms. Instead it plays a targeted role compacting the rDNA proximal regions and promoting resolution of peri-centromeric regions. Our results argue that the conserved mechanism of SMC complexes is to form chromatin loops and that distinct SMC-dependent looping activities are selectively deployed to appropriately compact chromosomes. PMID:28825700

CENP-A and topoisomerase-II antagonistically affect chromosome length.

PubMed

Ladouceur, A-M; Ranjan, Rajesh; Smith, Lydia; Fadero, Tanner; Heppert, Jennifer; Goldstein, Bob; Maddox, Amy Shaub; Maddox, Paul S

2017-09-04

The size of mitotic chromosomes is coordinated with cell size in a manner dependent on nuclear trafficking. In this study, we conducted an RNA interference screen of the Caenorhabditis elegans nucleome in a strain carrying an exceptionally long chromosome and identified the centromere-specific histone H3 variant CENP-A and the DNA decatenizing enzyme topoisomerase-II (topo-II) as candidate modulators of chromosome size. In the holocentric organism C. elegans , CENP-A is positioned periodically along the entire length of chromosomes, and in mitosis, these genomic regions come together linearly to form the base of kinetochores. We show that CENP-A protein levels decreased through development coinciding with chromosome-size scaling. Partial loss of CENP-A protein resulted in shorter mitotic chromosomes, consistent with a role in setting chromosome length. Conversely, topo-II levels were unchanged through early development, and partial topo-II depletion led to longer chromosomes. Topo-II localized to the perimeter of mitotic chromosomes, excluded from the centromere regions, and depletion of topo-II did not change CENP-A levels. We propose that self-assembly of centromeric chromatin into an extended linear array promotes elongation of the chromosome, whereas topo-II promotes chromosome-length shortening. © 2017 Ladouceur et al.

Highly distinct chromosomal structures in cowpea (Vigna unguiculata), as revealed by molecular cytogenetic analysis.

PubMed

Iwata-Otsubo, Aiko; Lin, Jer-Young; Gill, Navdeep; Jackson, Scott A

2016-05-01

Cowpea (Vigna unguiculata (L.) Walp) is an important legume, particularly in developing countries. However, little is known about its genome or chromosome structure. We used molecular cytogenetics to characterize the structure of pachytene chromosomes to advance our knowledge of chromosome and genome organization of cowpea. Our data showed that cowpea has highly distinct chromosomal structures that are cytologically visible as brightly DAPI-stained heterochromatic regions. Analysis of the repetitive fraction of the cowpea genome present at centromeric and pericentromeric regions confirmed that two retrotransposons are major components of pericentromeric regions and that a 455-bp tandem repeat is found at seven out of 11 centromere pairs in cowpea. These repeats likely evolved after the divergence of cowpea from common bean and form chromosomal structure unique to cowpea. The integration of cowpea genetic and physical chromosome maps reveals potential regions of suppressed recombination due to condensed heterochromatin and a lack of pairing in a few chromosomal termini. This study provides fundamental knowledge on cowpea chromosome structure and molecular cytogenetics tools for further chromosome studies.

Studies on metatherian sex chromosomes. IX. Sex chromosomes of the greater glider (Marsupialia: Petauridae).

PubMed

Murray, J D; McKay, G M; Sharman, G B

1979-06-01

The greater glider, currently but incorrectly known as Schoinobates volans, is widely distributed in forested regions in eastern Australia. All animals studied from six different localities had 20 autosomes but there were four chromosomally distinct populations. At Royal National Park, N.S.W., all female greater gliders studied had 22 chromosomes including two large submetacentric X chromosomes with subterminal secondary constrictions in their longer arms. This form of X chromosome occurred also at Bondo State Forest, Myall Lakes and Coff's Harbour, N.S.W., and at Eidsvold, Qld. At Coomooboolaroo, Qld, the X chromosome was also a large submetacentric but a secondary constriction occurred in the shorter arm. Two chromosomally distinct types apparently occur in Royal National Park, one with XY males as in all other populations, and one with XY1Y2 males. Y or Y1, but not Y2, chromosomes were eliminated from the bone marrow in all populations but were present in spermatogonia, primary spermatocytes and cultured fibroblasts. Animals from Bondo State Forest had three or more acrocentric or metacentric supernumerary chromosomes.

An analysis of polygenes affecting wing shape on chromosome 2 in Drosophila melanogaster.

PubMed Central

Weber, K; Eisman, R; Higgins, S; Morey, L; Patty, A; Tausek, M; Zeng, Z B

2001-01-01

Genetic effects on an index of wing shape on chromosome 2 of Drosophila melanogaster were mapped using isogenic recombinants with transposable element markers. At least 10 genes with small additive effects are dispersed evenly along the chromosome. Many interactions exist, with only small net effects in homozygous recombinants and little effect on phenotypic variance. Heterozygous chromosome segments show almost no dominance. Pleiotropic effects on leg shape are only minor. At first view, wing shape genes form a rather homogeneous class, but certain complexities remain unresolved. PMID:11729152

Telomeres and mechanisms of Robertsonian fusion.

PubMed

Slijepcevic, P

1998-05-01

The Robertsonian (Rb) fusion, a chromosome rearrangement involving centric fusion of two acro-(telo)centric chromosomes to form a single metacentric, is one of the most frequent events in mammalian karyotype evolution. Since one of the functions of telomeres is to preserve chromosome integrity, a prerequisite for the formation of Rb fusions should be either telomere loss or telomere inactivation. Possible mechanisms underlying the formation of various types of Rb fusion are discussed here. For example, Rb fusion in wild mice involves complete loss of p-arm telomeres by chromosome breakage within minor satellite sequences. By contrast, interstitial telomeric sites are found in the pericentromeric regions of chromosomes originating from a number of vertebrate species, suggesting the occurrence of Rb-like fusion without loss of telomeres, a possibility consistent with some form of telomere inactivation. Finally, a recent study suggests that telomere shortening induced by the deletion of the telomerase RNA gene in the mouse germ-line leads to telomere loss and high frequencies of Rb fusion in mouse somatic cells. Thus, at least three mechanisms in mammalian cells lead to the formation of Rb fusions.

Detection of Inter-chromosomal Stable Aberrations by Multiple Fluorescence In Situ Hybridization (mFISH) and Spectral Karyotyping (SKY) in Irradiated Mice

PubMed Central

Pathak, Rupak; Koturbash, Igor; Hauer-Jensen, Martin

2017-01-01

Ionizing radiation (IR) induces numerous stable and unstable chromosomal aberrations. Unstable aberrations, where chromosome morphology is substantially compromised, can easily be identified by conventional chromosome staining techniques. However, detection of stable aberrations, which involve exchange or translocation of genetic materials without considerable modification in the chromosome morphology, requires sophisticated chromosome painting techniques that rely on in situ hybridization of fluorescently labeled DNA probes, a chromosome painting technique popularly known as fluorescence in situ hybridization (FISH). FISH probes can be specific for whole chromosome/s or precise sub-region on chromosome/s. The method not only allows visualization of stable aberrations, but it can also allow detection of the chromosome/s or specific DNA sequence/s involved in a particular aberration formation. A variety of chromosome painting techniques are available in cytogenetics; here two highly sensitive methods, multiple fluorescence in situ hybridization (mFISH) and spectral karyotyping (SKY), are discussed to identify inter-chromosomal stable aberrations that form in the bone marrow cells of mice after exposure to total body irradiation. Although both techniques rely on fluorescent labeled DNA probes, the method of detection and the process of image acquisition of the fluorescent signals are different. These two techniques have been used in various research areas, such as radiation biology, cancer cytogenetics, retrospective radiation biodosimetry, clinical cytogenetics, evolutionary cytogenetics, and comparative cytogenetics. PMID:28117817

Repetitive sequences and epigenetic modification: inseparable partners play important roles in the evolution of plant sex chromosomes.

PubMed

Li, Shu-Fen; Zhang, Guo-Jun; Yuan, Jin-Hong; Deng, Chuan-Liang; Gao, Wu-Jun

2016-05-01

The present review discusses the roles of repetitive sequences played in plant sex chromosome evolution, and highlights epigenetic modification as potential mechanism of repetitive sequences involved in sex chromosome evolution. Sex determination in plants is mostly based on sex chromosomes. Classic theory proposes that sex chromosomes evolve from a specific pair of autosomes with emergence of a sex-determining gene(s). Subsequently, the newly formed sex chromosomes stop recombination in a small region around the sex-determining locus, and over time, the non-recombining region expands to almost all parts of the sex chromosomes. Accumulation of repetitive sequences, mostly transposable elements and tandem repeats, is a conspicuous feature of the non-recombining region of the Y chromosome, even in primitive one. Repetitive sequences may play multiple roles in sex chromosome evolution, such as triggering heterochromatization and causing recombination suppression, leading to structural and morphological differentiation of sex chromosomes, and promoting Y chromosome degeneration and X chromosome dosage compensation. In this article, we review the current status of this field, and based on preliminary evidence, we posit that repetitive sequences are involved in sex chromosome evolution probably via epigenetic modification, such as DNA and histone methylation, with small interfering RNAs as the mediator.

Medical Entomology Studies - XIII. The Myzomyia Series of Anopheles (Cellia) in Thailand, with Emphasis on Intra-Interspecific Variations (Diptera: Culicidae) (Contributions of the American Entomological Institute. Volume 17, Number 4, 1980)

DTIC Science & Technology

1980-01-01

pinpoint the collection site as Fang District, Chiang Mai Province in June 1952. However, no specimens confirming the record have been found in the...members of the Myzomyia Series in Thailand were in Barnes (1923a, b), who recorded aconitus from Bangkok and Chiang Mai , culicifacies from Chiang Mai , fluviatilis...as funestus Giles, = listoni Liston) from Bangkok and Chiang Mai and minimus from Bangkok. Barnes (1923b) also contained a key to the

Chromosomal instability in Streptomyces avermitilis: major deletion in the central region and stable circularized chromosome

PubMed Central

2010-01-01

Background The chromosome of Streptomyces has been shown to be unstable, frequently undergoing gross chromosomal rearrangements. However, the mechanisms underlying this phenomenon remain unclear, with previous studies focused on two chromosomal ends as targets for rearrangements. Here we investigated chromosomal instability of Streptomyces avermitilis, an important producer of avermectins, and characterized four gross chromosomal rearrangement events, including a major deletion in the central region. The present findings provide a valuable contribution to the mechanistic study of genetic instability in Streptomyces. Results Thirty randomly-selected "bald" mutants derived from the wild-type strain all contained gross chromosomal rearrangements of various types. One of the bald mutants, SA1-8, had the same linear chromosomal structure as the high avermectin-producing mutant 76-9. Chromosomes of both strains displayed at least three independent chromosomal rearrangements, including chromosomal arm replacement to form new 88-kb terminal inverted repeats (TIRs), and two major deletions. One of the deletions eliminated the 36-kb central region of the chromosome, but surprisingly did not affect viability of the cells. The other deletion (74-kb) was internal to the right chromosomal arm. The chromosome of another bald mutant, SA1-6, was circularized with deletions at both ends. No obvious homology was found in all fusion sequences. Generational stability analysis showed that the chromosomal structure of SA1-8 and SA1-6 was stable. Conclusions Various chromosomal rearrangements, including chromosomal arm replacement, interstitial deletions and chromosomal circularization, occurred in S. avermitilis by non-homologous recombination. The finding of an inner deletion involving in the central region of S. avermitilis chromosome suggests that the entire Streptomyces chromosome may be the target for rearrangements, which are not limited, as previously reported, to the two chromosomal ends. PMID:20653985

The Role of Xist in X-Chromosome Dosage Compensation.

PubMed

Sahakyan, Anna; Yang, Yihao; Plath, Kathrin

2018-06-14

In each somatic cell of a female mammal one X chromosome is transcriptionally silenced via X-chromosome inactivation (XCI), initiating early in development. Although XCI events are conserved in mouse and human postimplantation development, regulation of X-chromosome dosage in preimplantation development occurs differently. In preimplantation development, mouse embryos undergo imprinted form of XCI, yet humans lack imprinted XCI and instead regulate gene expression of both X chromosomes by dampening transcription. The long non-coding RNA Xist/XIST is expressed in mouse and human preimplantation and postimplantation development to orchestrate XCI, but its role in dampening is unclear. In this review, we discuss recent advances in our understanding of the role of Xist in X chromosome dosage compensation in mouse and human. Copyright © 2018 Elsevier Ltd. All rights reserved.

The alpha-spectrin gene is on chromosome 1 in mouse and man.

PubMed

Huebner, K; Palumbo, A P; Isobe, M; Kozak, C A; Monaco, S; Rovera, G; Croce, C M; Curtis, P J

1985-06-01

By using alpha-spectrin cDNA clones of murine and human origin and somatic cell hybrids segregating either mouse or human chromosomes, the gene for alpha-spectrin has been mapped to chromosome 1 in both species. This assignment of the mouse alpha-spectrin gene to mouse chromosome 1 by DNA hybridization strengthens the previous identification of the alpha-spectrin locus in mouse with the sph locus, which previously was mapped by linkage analysis to mouse chromosome 1, distal to the Pep-3 locus. By in situ hybridization to human metaphase chromosomes, the human alpha-spectrin gene has been localized to 1q22-1q25; interestingly, the locus for a non-Rh-linked form of elliptocytosis has been provisionally mapped to band 1q2 by family linkage studies.

Chromosome banding in amphibia. XXIII. Giant W sex chromosomes and extremely small genomes in Eleutherodactylus euphronides and Eleutherodactylus shrevei (Anura, Leptodactylidae).

PubMed

Schmid, M; Feichtinger, W; Steinlein, C; Rupprecht, A; Haaf, T; Kaiser, H

2002-01-01

Highly differentiated, heteromorphic ZZ female symbol /ZW male symbol sex chromosomes were found in the karyotypes of the neotropical leptodactylid frogs Eleutherodactylus euphronides and E. shrevei. The W chromosomes are the largest heterochromatic, female-specific chromosomes so far discovered in the class Amphibia. The analyses of the banding patterns with AT- and GC base-pair specific fluorochromes show that the constitutive heterochromatin in the giant W chromosomes consists of various categories of repetitive DNA sequences. The W chromosomes of both species are similar in size, morphology and banding patterns, whereas their Z chromosomes exhibit conspicuous differences. In the cell nuclei of female animals, the W chromosomes form very prominent chromatin bodies (W chromatin). DNA flow cytometric measurements demonstrate clear differences in the DNA content of male and female erythrocytes caused by the giant W chromosome, and also shows that these Eleutherodactylus genomes are among the smallest of all amphibian genomes. The importance of the heteromorphic ZW sex chromosomes for the study of Z-linked genes, the similarities and differences of the two karyotypes, and the significance of the exceptionally small genomes are discussed. Copyright 2002 S. Karger AG, Basel

Sex chromosomes in land plants.

PubMed

Ming, Ray; Bendahmane, Abdelhafid; Renner, Susanne S

2011-01-01

Sex chromosomes in land plants can evolve as a consequence of close linkage between the two sex determination genes with complementary dominance required to establish stable dioecious populations, and they are found in at least 48 species across 20 families. The sex chromosomes in hepatics, mosses, and gymnosperms are morphologically heteromorphic. In angiosperms, heteromorphic sex chromosomes are found in at least 19 species from 4 families, while homomorphic sex chromosomes occur in 20 species from 13 families. The prevalence of the XY system found in 44 out of 48 species may reflect the predominance of the evolutionary pathway from gynodioecy towards dioecy. All dioecious species have the potential to evolve sex chromosomes, and reversions back from dioecy to various forms of monoecy, gynodioecy, or androdioecy have also occurred. Such reversals may occur especially during the early stages of sex chromosome evolution before the lethality of the YY (or WW) genotype is established.

A Functional Relationship between NuMA and Kid Is Involved in Both Spindle Organization and Chromosome Alignment in Vertebrate CellsV⃞

PubMed Central

Levesque, Aime A.; Howard, Louisa; Gordon, Michael B.; Compton, Duane A.

2003-01-01

We examined spindle morphology and chromosome alignment in vertebrate cells after simultaneous perturbation of the chromokinesin Kid and either NuMA, CENP-E, or HSET. Spindle morphology and chromosome alignment after simultaneous perturbation of Kid and either HSET or CENP-E were no different from when either HSET or CENP-E was perturbed alone. However, short bipolar spindles with organized poles formed after perturbation of both Kid and NuMA in stark contrast to splayed spindle poles observed after perturbation of NuMA alone. Spindles were disorganized if Kid, NuMA, and HSET were perturbed, indicating that HSET is sufficient for spindle organization in the absence of Kid and NuMA function. In addition, chromosomes failed to align efficiently at the spindle equator after simultaneous perturbation of Kid and NuMA despite appropriate kinetochore-microtubule interactions that generated chromosome movement at normal velocities. These data indicate that a functional relationship between the chromokinesin Kid and the spindle pole organizing protein NuMA influences spindle morphology, and we propose that this occurs because NuMA forms functional linkages between kinetochore and nonkinetochore microtubules at spindle poles. In addition, these data show that both Kid and NuMA contribute to chromosome alignment in mammalian cells. PMID:12972545

Chromosome and cell wall segregation in Streptococcus faecium ATCC 9790

DOE Office of Scientific and Technical Information (OSTI.GOV)

Higgins, M.L.; Glaser, D.; Dicker, D.T.

1989-01-01

Segregation was studied by measuring the positions of autoradiographic grain clusters in chains formed from single cells containing on average less than one radiolabeled chromosome strand. The degree to which chromosomal and cell wall material cosegregated was quantified by using the methods of S. Cooper and M. Weinberger, dividing the number of chains labeled at the middle. This analysis indicated that in contrast to chromosomal segregation in Escherichia coli and, in some studies, to that in gram-positive rods, chromosomal segregation in Streptococcus faecium was slightly nonrandom and did not vary with growth rate. Results were not significantly affected by strandmore » exchange. In contrast, labeled cell wall segregated predominantly nonrandomly.« less

Cytological evidence for chromosome elimination in wheat x Imperata cylindrica hybrids.

PubMed

Komeda, Norio; Chaudhary, Harinder K; Suzuki, Go; Mukai, Yasuhiko

2007-06-01

Haploid induction of wheat by crossing with Imperata cylindrica pollen is an efficient method for doubled haploid breeding. We investigated the process of wheat haploid formation after crossing with I. cylindrica. Our cytological observations of zygotes showed the successful fertilization of parental gametes. Wheat haploids were formed by complete elimination of I. cylindrica chromosomes. Missegregation of I. cylindrica chromosomes was observed in the first cell division of zygote. At metaphase I. cylindrica chromosomes did not congress onto the equatorial plate. The sister chromosomes did not move toward the poles during anaphase, though their cohesion was released normally. I. cylindrica chromosomes were still in the cytoplasm at telophase and eliminated from daughter nuclei. After two-celled stage, we could find no I. cylindrica chromosome in the nuclei but micronuclei containing I. cylindrica chromatin in the cytoplasm. These observations indicate that I. cylindrica chromosomes are completely eliminated from nuclei in the first cell division probably due to lack of functional kinetochores.

Sequencing of individual chromosomes of plant pathogenic Fusarium oxysporum.

PubMed

Kashiwa, Takeshi; Kozaki, Toshinori; Ishii, Kazuo; Turgeon, B Gillian; Teraoka, Tohru; Komatsu, Ken; Arie, Tsutomu

2017-01-01

A small chromosome in reference isolate 4287 of F. oxysporum f. sp. lycopersici (Fol) has been designated as a 'pathogenicity chromosome' because it carries several pathogenicity related genes such as the Secreted In Xylem (SIX) genes. Sequence assembly of small chromosomes in other isolates, based on a reference genome template, is difficult because of karyotype variation among isolates and a high number of sequences associated with transposable elements. These factors often result in misassembly of sequences, making it unclear whether other isolates possess the same pathogenicity chromosome harboring SIX genes as in the reference isolate. To overcome this difficulty, single chromosome sequencing after Contour-clamped Homogeneous Electric Field (CHEF) separation of chromosomes was performed, followed by de novo assembly of sequences. The assembled sequences of individual chromosomes were consistent with results of probing gels of CHEF separated chromosomes with SIX genes. Individual chromosome sequencing revealed that several SIX genes are located on a single small chromosome in two pathogenic forms of F. oxysporum, beyond the reference isolate 4287, and in the cabbage yellows fungus F. oxysporum f. sp. conglutinans. The particular combination of SIX genes on each small chromosome varied. Moreover, not all SIX genes were found on small chromosomes; depending on the isolate, some were on big chromosomes. This suggests that recombination of chromosomes and/or translocation of SIX genes may occur frequently. Our method improves sequence comparison of small chromosomes among isolates. Copyright © 2016 Elsevier Inc. All rights reserved.

Chromosomal duplications in bacteria, fruit flies, and humans

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lupski, J.R.; Weinstock, G.M.; Roth, J.R.

1996-01-01

Tandem duplication of chromosomal segments has been recognized as a frequent mutational mechanism in several genetic model systems. In bacteria, fruit flies, and humans, duplications form by similar molecular mechanisms and appear to be important in genome evolution. 80 refs.

Characterization of a complex chromosomal rearrangement using chromosome, FISH, and microarray assays in a girl with multiple congenital abnormalities and developmental delay.

PubMed

Hemmat, Morteza; Yang, Xiaojing; Chan, Patricia; McGough, Robert A; Ross, Leslie; Mahon, Loretta W; Anguiano, Arturo L; Boris, Wang T; Elnaggar, Mohamed M; Wang, Jia-Chi J; Strom, Charles M; Boyar, Fatih Z

2014-01-01

Complex chromosomal rearrangements (CCRs) are balanced or unbalanced structural rearrangements involving three or more cytogenetic breakpoints on two or more chromosomal pairs. The phenotypic anomalies in such cases are attributed to gene disruption, superimposed cryptic imbalances in the genome, and/or position effects. We report a 14-year-old girl who presented with multiple congenital anomalies and developmental delay. Chromosome and FISH analysis indicated a highly complex chromosomal rearrangement involving three chromosomes (3, 7 and 12), seven breakpoints as a result of one inversion, two insertions, and two translocations forming three derivative chromosomes. Additionally, chromosomal microarray study (CMA) revealed two submicroscopic deletions at 3p12.3 (467 kb) and 12q13.12 (442 kb). We postulate that microdeletion within the ROBO1 gene at 3p12.3 may have played a role in the patient's developmental delay, since it has potential activity-dependent role in neurons. Additionally, factors other than genomic deletions such as loss of function or position effects may also contribute to the abnormal phenotype in our patient.

Mapping of the bcl-2 oncogene on mouse chromosome 1.

PubMed

Mock, B A; Givol, D; D'Hoostelaere, L A; Huppi, K; Seldin, M F; Gurfinkel, N; Unger, T; Potter, M; Mushinski, J F

1988-01-01

Two bcl-2 alleles have been identified in inbred strains of mice by restriction fragment length polymorphism (RFLP). Analysis of a bcl-2 RFLP in a series of bilineal congenic strains (C.D2), developed as a tool for chromosomal mapping studies, revealed linkage of bcl-2 to the Idh-1/Pep-3 region of murine chromosome 1. The co-segregation of bcl-2 alleles with allelic forms of two other chromosome 1 loci, Ren-1,2 and Spna-1, in a set of back-cross progeny, positions bcl-2 7.8 cM centromeric from Ren-1,2.

Chromatin fibers: from classical descriptions to modern interpretation.

PubMed

Kuznetsova, Maria A; Sheval, Eugene V

2016-11-01

The first description of intrachromosomal fibers was made by Baranetzky in 1880. Since that time, a plethora of fibrillar substructures have been described inside the mitotic chromosomes, and published data indicate that chromosomes may be formed as a result of the hierarchical folding of chromatin fibers. In this review, we examine the evolution and the current state of research on the morphological organization of mitotic chromosomes. © 2016 International Federation for Cell Biology.

Ticking Telomeres/Telltale Telomerase.

ERIC Educational Resources Information Center

Biermann, Carol A.

1997-01-01

Discusses telomeres, complexes of DNA and protein that form the chromatin at the ends of chromosomes. Highlights telomeres as controllers of chromosome integrity, expendable telomeres, DNA replication requirements and their consequences, protection of structural genes, telomerase as indicators of immortality, cancer cells and other immortals, and…

Revealing the micromechanics driving cellular division: optical manipulation of force-bearing substructure in mitotic cells

NASA Astrophysics Data System (ADS)

Ono, Matthew; Preece, Daryl; Duquette, Michelle; Forer, Arthur; Berns, Michael

2017-08-01

During the anaphase stage of mitosis, a motility force transports genetic material in the form of chromosomes to the poles of the cell. Chromosome deformations during anaphase transport have largely been attributed to viscous drag force, however LaFountain et. al. found that a physical tether connects separating chromosome ends in crane-fly spermatocytes such that a backwards tethering force elongates the separating chromosomes. In the presented study laser microsurgery was used to deduce the mechanistic basis of chromosome elongation in rat-kangaroo cells. In half of tested chromosome pairs, laser microsurgery between separating chromosome ends reduced elongation by 7+/-3% suggesting a source of chromosome strain independent of viscous drag. When microsurgery was used to sever chromosomes during transport, kinetochore attached fragments continued poleward travel while half of end fragments traveled towards the opposite pole and the remaining fragments either did not move or segregated to the proper pole. Microsurgery directed between chromosome ends always ceased cross-polar fragment travel suggesting the laser severed a physical tether transferring force to the fragment. Optical trapping of fragments moving towards the opposite pole estimates an upper boundary on the tethering force of 1.5 pN.

Exceptional complex chromosomal rearrangements in three generations.

PubMed

Kartapradja, Hannie; Marzuki, Nanis Sacharina; Pertile, Mark D; Francis, David; Suciati, Lita Putri; Anggaratri, Helena Woro; Ambarwati, Debby Dwi; Idris, Firman Prathama; Lesmana, Harry; Trimarsanto, Hidayat; Paramayuda, Chrysantine; Harahap, Alida Roswita

2015-01-01

We report an exceptional complex chromosomal rearrangement (CCR) found in three individuals in a family that involves 4 chromosomes with 5 breakpoints. The CCR was ascertained in a phenotypically abnormal newborn with additional chromosomal material on the short arm of chromosome 4. Maternal karyotyping indicated that the mother carried an apparently balanced CCR involving chromosomes 4, 6, 11, and 18. Maternal transmission of the derivative chromosome 4 resulted in partial trisomy for chromosomes 6q and 18q and a partial monosomy of chromosome 4p in the proband. Further family studies found that the maternal grandmother carried the same apparently balanced CCR as the proband's mother, which was confirmed using the whole chromosome painting (WCP) FISH. High resolution whole genome microarray analysis of DNA from the proband's mother found no evidence for copy number imbalance in the vicinity of the CCR translocation breakpoints, or elsewhere in the genome, providing evidence that the mother's and grandmother's CCRs were balanced at a molecular level. This structural rearrangement can be categorized as an exceptional CCR due to its complexity and is a rare example of an exceptional CCR being transmitted in balanced and/or unbalanced form across three generations.

Genomic Pangea: coordinate gene regulation and cell-specific chromosomal topologies.

PubMed

Laster, Kyle; Kosak, Steven T

2010-06-01

The eukaryotic nucleus is functionally organized. Gene loci, for example, often reveal altered localization patterns according to their developmental regulation. Whole chromosomes also demonstrate non-random nuclear positions, correlated with inherent characteristics such as gene density or size. Given that hundreds to thousands of genes are coordinately regulated in any given cell type, interest has grown in whether chromosomes may be specifically localized according to gene regulation. A synthesis of the evidence for preferential chromosomal organization suggests that, beyond basic characteristics, chromosomes can assume positions functionally related to gene expression. Moreover, analysis of total chromosome organization during cellular differentiation indicates that unique chromosome topologies, albeit probabilistic, in effect define a cell lineage. Future work with new techniques, including the advanced forms of the chromosome conformation capture (3C), and the development of next-generation whole-genome imaging approaches, will help to refine our view of chromosomal organization. We suggest that genomic organization during cellular differentiation should be viewed as a dynamic process, with gene expression patterns leading to chromosome associations that feed back on themselves, leading to the self-organization of the genome according to coordinate gene regulation. Copyright 2010 Elsevier Ltd. All rights reserved.

Chromosome reduction in Eleocharis maculosa (Cyperaceae).

PubMed

da Silva, C R M; González-Elizondo, M S; Laforga Vanzela, A L

2008-01-01

Chromosome numbers in Cyperaceae lower than the typical basic number x = 5 have been described for only three species: Rhynchospora tenuis (n = 2), Fimbristylis umbellaris (n = 3) and Eleocharis subarticulata (n = 3). Eleocharis maculosa is recorded here as the fourth species of Cyperaceae that has a chromosome number lower than 2n = 10, with 2n = 8, 7 and 6. The karyotype differentiation in E. maculosa was studied using conventional staining (mitosis and meiosis), FISH with 45S and 5S rDNA and telomere probes. The results allow us to determine which chromosomes of the chromosome race with 2n = 10 fused to form the remaining reduced numbers, as well as to understand how the symploidy and translocation mechanisms were important in karyotype differentiation and the formation of chromosome races in Eleocharis. Copyright 2008 S. Karger AG, Basel.

The alpha-spectrin gene is on chromosome 1 in mouse and man.

PubMed Central

Huebner, K; Palumbo, A P; Isobe, M; Kozak, C A; Monaco, S; Rovera, G; Croce, C M; Curtis, P J

1985-01-01

By using alpha-spectrin cDNA clones of murine and human origin and somatic cell hybrids segregating either mouse or human chromosomes, the gene for alpha-spectrin has been mapped to chromosome 1 in both species. This assignment of the mouse alpha-spectrin gene to mouse chromosome 1 by DNA hybridization strengthens the previous identification of the alpha-spectrin locus in mouse with the sph locus, which previously was mapped by linkage analysis to mouse chromosome 1, distal to the Pep-3 locus. By in situ hybridization to human metaphase chromosomes, the human alpha-spectrin gene has been localized to 1q22-1q25; interestingly, the locus for a non-Rh-linked form of elliptocytosis has been provisionally mapped to band 1q2 by family linkage studies. Images PMID:2987946

Wrestling with Chromosomes: The Roles of SUMO During Meiosis.

PubMed

Nottke, Amanda C; Kim, Hyun-Min; Colaiácovo, Monica P

2017-01-01

Meiosis is a specialized form of cell division required for the formation of haploid gametes and therefore is essential for successful sexual reproduction. Various steps are exquisitely coordinated to ensure accurate chromosome segregation during meiosis, thereby promoting the formation of haploid gametes from diploid cells. Recent studies are demonstrating that an important form of regulation during meiosis is exerted by the post-translational protein modification known as sumoylation. Here, we review and discuss the various critical steps of meiosis in which SUMO-mediated regulation has been implicated thus far. These include the maintenance of meiotic centromeric heterochromatin , meiotic DNA double-strand break repair and homologous recombination, centromeric coupling, and the assembly of a proteinaceous scaffold between homologous chromosomes known as the synaptonemal complex.

Genome Organization Drives Chromosome Fragility.

PubMed

Canela, Andres; Maman, Yaakov; Jung, Seolkyoung; Wong, Nancy; Callen, Elsa; Day, Amanda; Kieffer-Kwon, Kyong-Rim; Pekowska, Aleksandra; Zhang, Hongliang; Rao, Suhas S P; Huang, Su-Chen; Mckinnon, Peter J; Aplan, Peter D; Pommier, Yves; Aiden, Erez Lieberman; Casellas, Rafael; Nussenzweig, André

2017-07-27

In this study, we show that evolutionarily conserved chromosome loop anchors bound by CCCTC-binding factor (CTCF) and cohesin are vulnerable to DNA double strand breaks (DSBs) mediated by topoisomerase 2B (TOP2B). Polymorphisms in the genome that redistribute CTCF/cohesin occupancy rewire DNA cleavage sites to novel loop anchors. While transcription- and replication-coupled genomic rearrangements have been well documented, we demonstrate that DSBs formed at loop anchors are largely transcription-, replication-, and cell-type-independent. DSBs are continuously formed throughout interphase, are enriched on both sides of strong topological domain borders, and frequently occur at breakpoint clusters commonly translocated in cancer. Thus, loop anchors serve as fragile sites that generate DSBs and chromosomal rearrangements. VIDEO ABSTRACT. Published by Elsevier Inc.

Comparative entomological study on ecology and behaviour of Anopheles mosquitoes in highland and lowland localities of Derashe District, southern Ethiopia.

PubMed

Gone, Terefe; Balkew, Meshesha; Gebre-Michael, Teshome

2014-10-20

Change in climatic and socio-economic situations is paving the way for the spread of malaria in highland areas which were generally known to be malaria free. Despite this, information regarding highland malaria transmission is scarce. Thus, the present study investigated entomological parameters linked to malaria transmission in the highlands of Southern Ethiopia. A longitudinal entomological study was conducted in three localities situated at different altitudes ranging between 1300 and 2650m above sea level in Derashe district, Southern Ethiopia. Larval and adult anopheline mosquitoes were collected between October 2011 and February 2012. An. arabiensis and An. funestus s.l existed at significantly higher densities in the lowland (Wozeka) in contrast to An. christyi and An. Demeilloni, which were more abundant in the highland localities (P < 0.01). Conversely, An. pharoensis and An. cinereus were scarce and only found in the lowland and highlands, respectively. Habitats of larvae of An. arabiensis were characterized as clear, sun-lit, permanent, still water (streams) without vegetation and situated close to human habitations. On the other hand, habitats of An. christyi are shaded, still, turbid and contain natural water (rain pools) with vegetation and mats of algae. The relative abundance of An. Arabiensis, which is the primary malaria vector in Ethiopia is significantly and positively correlated with water temperature, pH and average depth (P < 0.05). An. arabiensis, An. funestus s.l and An. demeilloni showed zoophilic and exophilic tendencies. None of the anophelines tested for P. falciparum and P. vivax sporozoite infections were positive. In conclusion, malaria parasites and vectors existed in the highlands of Derashe District. Therefore, appropriate disease and vector control strategies must be designed and implemented to prevent potential outbreaks.

Land use and land cover changes and spatiotemporal dynamics of anopheline larval habitats during a four-year period in a highland community of Africa.

PubMed

Munga, Stephen; Yakob, Laith; Mushinzimana, Emmanuel; Zhou, Guofa; Ouna, Tom; Minakawa, Noboru; Githeko, Andrew; Yan, Guiyun

2009-12-01

Spatial and temporal variations in the distribution of anopheline larval habitats and land use and land cover (LULC) changes can influence malaria transmission intensity. This information is important for understanding the environmental determinants of malaria transmission heterogeneity, and it is critical to the study of the effects of environmental changes on malaria transmission. In this study, we investigated the spatial and temporal variations in the distribution of anopheline larval habitats and LULC changes in western Kenya highlands over a 4-year period. Anopheles gambiae complex larvae were mainly confined to valley bottoms during both the dry and wet seasons. Although An. gambiae larvae were located in man-made habitats where riparian forests and natural swamps had been cleared, Anopheles funestus larvae were mainly found in permanent habitats in pastures. The association between land cover type and occurrence of anopheline larvae was statistically significant. The distribution of anopheline positive habitats varied significantly between months, during the survey. In 2004, the mean density of An. gambiae was significantly higher during the month of May, whereas the density of An. funestus peaked significantly in February. Over the study period, major LULC changes occurred mostly in the valley bottoms. Overall, farmland increased by 3.9%, whereas both pastures and natural swamps decreased by 8.9% and 20.9%, respectively. The area under forest cover was decreased by 5.8%. Land-use changes in the study area are favorable to An. gambiae larval development, thereby risking a more widespread distribution of malaria vector habitats and potentially increasing malaria transmission in western Kenya highlands.

Plasmid Characterization and Chromosome Analysis of Two netF+ Clostridium perfringens Isolates Associated with Foal and Canine Necrotizing Enteritis

PubMed Central

Mehdizadeh Gohari, Iman; Kropinski, Andrew M.; Weese, Scott J.; Parreira, Valeria R.; Whitehead, Ashley E.; Boerlin, Patrick; Prescott, John F.

2016-01-01

The recent discovery of a novel beta-pore-forming toxin, NetF, which is strongly associated with canine and foal necrotizing enteritis should improve our understanding of the role of type A Clostridium perfringens associated disease in these animals. The current study presents the complete genome sequence of two netF-positive strains, JFP55 and JFP838, which were recovered from cases of foal necrotizing enteritis and canine hemorrhagic gastroenteritis, respectively. Genome sequencing was done using Single Molecule, Real-Time (SMRT) technology-PacBio and Illumina Hiseq2000. The JFP55 and JFP838 genomes include a single 3.34 Mb and 3.53 Mb chromosome, respectively, and both genomes include five circular plasmids. Plasmid annotation revealed that three plasmids were shared by the two newly sequenced genomes, including a NetF/NetE toxins-encoding tcp-conjugative plasmid, a CPE/CPB2 toxins-encoding tcp-conjugative plasmid and a putative bacteriocin-encoding plasmid. The putative beta-pore-forming toxin genes, netF, netE and netG, were located in unique pathogenicity loci on tcp-conjugative plasmids. The C. perfringens JFP55 chromosome carries 2,825 protein-coding genes whereas the chromosome of JFP838 contains 3,014 protein-encoding genes. Comparison of these two chromosomes with three available reference C. perfringens chromosome sequences identified 48 (~247 kb) and 81 (~430 kb) regions unique to JFP55 and JFP838, respectively. Some of these divergent genomic regions in both chromosomes are phage- and plasmid-related segments. Sixteen of these unique chromosomal regions (~69 kb) were shared between the two isolates. Five of these shared regions formed a mosaic of plasmid-integrated segments, suggesting that these elements were acquired early in a clonal lineage of netF-positive C. perfringens strains. These results provide significant insight into the basis of canine and foal necrotizing enteritis and are the first to demonstrate that netF resides on a large and unique plasmid-encoded locus. PMID:26859667

Genetic and physical mapping at the limb-girdle muscular dystrophy locus (LGMD2B) on chromosome 2p

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bashir, R.; Keers, S.; Strachan, T.

1996-04-01

The limb-girdle muscular dystrophies (LGMD) are a genetically heterogeneous group of disorders, different forms of which have been mapped to at least six distinct genetic loci. We have mapped to at least six distinct genetic loci. We have mapped an autosomal recessive form of LGMD (LGMD2B) to chromosome 2p13. Two other conditions have been shown to map to this region or to the homologous region in mouse: a gene for a form of autosomal recessive distal muscular dystrophy, Miyoshi myopathy, shows linkage to the same markers on chromosome 2p as LGMD2B, and an autosomal recessive mouse mutation mnd2, in whichmore » there is rapidly progressive paralysis and muscle atrophy, has been mapped to mouse chromosome 6 to a region showing conserved synteny with human chromosome 2p12-p13. We have assembled a 6-cM YAC contig spanning the LGMD2B locus and have mapped seven genes and 13 anonymous polymorphic microsatellites to it. Using haplotype analysis in the linked families, we have narrowed our region of interest to a 0-cM interval between D2S2113 and D2S145, which does not overlap with the critical region for mnd2 in mouse. Use of these most closely linked markers will help to determine the relationship between LGMD2B and Miyoshi myopathy. YACs selected from our contig will be the starting point for the cloning of the LGMD2B gene and thereby establish the biological basis for this form of muscular dystrophy and its relationship with the other limb-girdle muscular dystrophies. 26 refs., 6 figs.« less

Contact zone between chromosomal races of Mus musculus domesticus. 2. Fertility and segregation in laboratory-reared and wild mice heterozygous for multiple robertsonian rearrangements.

PubMed

Castiglia, R; Capanna, E

2000-08-01

Litter size, anaphase I nondisjunction and X-Y dissociation at metaphase I were studied in homozygous and heterozygous house mice from a central Italian chromosomal hybrid zone between the CD (2n=22) race and the standard race (2n=40). We also observed the segregation of the two chromosomal forms (Robertsonian and non-Robertsonian) in male and female multiple heterozygotes from the karyotype of their offspring and chromosomal arm counts of metaphase II. Litter size was significantly reduced in the F1 hybrids, but there was no difference in litter size between male and female F1s. Fertility in wild mice decreased with increasing numbers of structural heterozygosities (0-5). Some metacentrics appear to be under meiotic drive but there was no rule as to which of the two forms was favoured in backcrosses. An original observation of a negative correlation between the length of metacentrics and transmission rate was described in hybrids. Slight cosegregation of chromosomes with a similar morphology was present in the progeny of males and females. These observations are discussed in relation to the stability of this hybrid zone through time.

CHROMOSOMAL MULTIPLICITY IN BURKHOLDERIA CEPACIA

EPA Science Inventory

We have used CHEF gel electrophoresis to screen preparations of large DNA from different Burkholderia cepacia isolates for the presence of DNA species corresponding to the linearized forms of the three chromosomes of 3.4,2.5, and 0.9 Mb identified in B. cepacia strain 17616. DNA ...

Meiosis and Maternal Aging: Insights from Aneuploid Oocytes and Trisomy Births

PubMed Central

Herbert, Mary; Kalleas, Dimitrios; Cooney, Daniel; Lamb, Mahdi; Lister, Lisa

2015-01-01

In most organisms, genome haploidization requires reciprocal DNA exchanges (crossovers) between replicated parental homologs to form bivalent chromosomes. These are resolved to their four constituent chromatids during two meiotic divisions. In female mammals, bivalents are formed during fetal life and remain intact until shortly before ovulation. Extending this period beyond ∼35 years greatly increases the risk of aneuploidy in human oocytes, resulting in a dramatic increase in infertility, miscarriage, and birth defects, most notably trisomy 21. Bivalent chromosomes are stabilized by cohesion between sister chromatids, which is mediated by the cohesin complex. In mouse oocytes, cohesin becomes depleted from chromosomes during female aging. Consistent with this, premature loss of centromeric cohesion is a major source of aneuploidy in oocytes from older women. Here, we propose a mechanistic framework to reconcile data from genetic studies on human trisomy and oocytes with recent advances in our understanding of the molecular mechanisms of chromosome segregation during meiosis in model organisms. PMID:25833844

Initiation and Reinitiation of DNA Synthesis during Replication of Bacteriophage T7*

PubMed Central

Dressler, David; Wolfson, John; Magazin, Marilyn

1972-01-01

In its first round of replication, the T7 chromosome follows a simple pattern, as viewed in the electron microscope. The iniation of DNA synthesis occurs about 17% from the genetic left end of the viral DNA rod. Bidirectional DNA synthesis from this origin then generates a replicating intermediate that we call an “eye form.” In the eye form, when synthesis in the leftward direction reaches the left end of the viral chromosome, the molecule is converted into a Y-shaped replicating rod. The remaining growing point continues synthesis rightward, until presumably it runs off the right end of the DNA rod, thus terminating replication. Numerous T7 chromosomes were found in which a second round of replication had begun before the first round had finished. Analysis of these reinitiated DNA molecules showed that the second round of replication, like the first, began 17% from the end of the chromosome and involved bidirectional DNA synthesis. Images PMID:4554539

Proechimys (Rodentia, Echimyidae): characterization and taxonomic considerations of a form with a very low diploid number and a multiple sex chromosome system

PubMed Central

2013-01-01

Background Proechimys is the most diverse genus in family Echimyidae, comprising 25 species (two of which are polytypic) and 39 taxa. Despite the numerous forms of this rodent and their abundance in nature, there are many taxonomic problems due to phenotypic similarities within the genus and high intraspecific variation. Extensive karyotypic variation has been noted, however, with diploid numbers (2n) ranging from 14 to 62 chromosomes. Some heteromorphism can be found, and 57 different karyotypes have been described to date. Results In the present work, we describe a cytotype with a very low 2n. Specimens of Proechimys cf. longicaudatus were collected from two different places in northern Mato Grosso state, Brazil (12°54″S, 52°22″W and 9°51′17″S, 58°14′53″W). The females and males had 16 and 17 chromosomes, respectively; all chromosomes were acrocentric, with the exception of the X chromosome, which was bi-armed. The sex chromosome system was found to be XY1Y2, originating from a Robertsonian rearrangement involving the X and a large acrocentric autosome. Females had two Neo-X chromosomes, and males had one Neo-X and two Y chromosomes. NOR staining was found in the interstitial region of one autosomal pair. Conclusions Comparison of this karyotype with those described in the literature revealed that Proechimys with similar karyotypes had previously been collected from nearby localities. We therefore suggest that this Proechimys belongs to a different taxon, and is either a new species or one that requires reassessment. PMID:23496787

Close but Distinct Regions of Human Herpesvirus 8 Latency-Associated Nuclear Antigen 1 Are Responsible for Nuclear Targeting and Binding to Human Mitotic Chromosomes

PubMed Central

Piolot, Tristan; Tramier, Marc; Coppey, Maité; Nicolas, Jean-Claude; Marechal, Vincent

2001-01-01

Human herpesvirus 8 is associated with all forms of Kaposi's sarcoma, AIDS-associated body cavity-based lymphomas, and some forms of multicentric Castleman's disease. Herpesvirus 8, like other gammaherpesviruses, can establish a latent infection in which viral genomes are stably maintained as multiple episomes. The latent nuclear antigen (LANA or LNAI) may play an essential role in the stable maintenance of latent episomes, notably by interacting concomitantly with the viral genomes and the metaphase chromosomes, thus ensuring an efficient transmission of the neoduplicated episomes to the daughter cells. To identify the regions responsible for its nuclear and subnuclear localization in interphase and mitotic cells, LNAI and various truncated forms were fused to a variant of green fluorescent protein. This enabled their localization and chromosome binding activity to be studied by low-light-level fluorescence microscopy in living HeLa cells. The results demonstrate that nuclear localization of LNAI is due to a unique signal, which maps between amino acids 24 and 30. Interestingly, this nuclear localization signal closely resembles those identified in EBNA1 from Epstein-Barr virus and herpesvirus papio. A region encompassing amino acids 5 to 22 was further proved to mediate the specific interaction of LNA1 with chromatin during interphase and the chromosomes during mitosis. The presence of putative phosphorylation sites in the chromosome binding sites of LNA1 and EBNA1 suggests that their activity may be regulated by specific cellular kinases. PMID:11264383

Kinetochore fiber formation in animal somatic cells: dueling mechanisms come to a draw

PubMed Central

2008-01-01

The attachment to and movement of a chromosome on the mitotic spindle are mediated by the formation of a bundle of microtubules (MTs) that tethers the kinetochore on the chromosome to a spindle pole. The origin of these “kinetochore fibers” (K fibers) has been investigated for over 125 years. As noted in 1944 by Schrader [Mitosis, Columbia University Press, New York, 110 pp.], there are three possible ways to form a K fiber: (a) it grows from the pole until it contacts the kinetochore, (b) it grows directly from the kinetochore, or (c) it forms as a result of an interaction between the pole and the chromosome. Since Schrader's time, it has been firmly established that K fibers in centrosome-containing animal somatic cells form as kinetochores capture MTs growing from the spindle pole (route a). It is now similarly clear that in cells lacking centrosomes, including higher plants and many animal oocytes, K fibers “self-assemble” from MTs generated by the chromosomes (route b). Can animal somatic cells form K fibers in the absence of centrosomes by the “self-assembly” pathway? In 2000, the answer to this question was shown to be a resounding “yes.” With this result, the next question became whether the presence of a centrosome normally suppresses K fiber self-assembly or if this route works concurrently with centrosome-mediated K-fiber formation. This question, too, has recently been answered: observations on untreated live animal cells expressing green fluorescent protein-tagged tubulin clearly show that kinetochores can nucleate the formation of their associated MTs in a unique manner in the presence of functional centrosomes. The concurrent operation of these two “dueling” routes for forming K fibers in animal cells helps explain why the attachment of kinetochores and the maturation of K fibers occur as quickly as they do on all chromosomes within a cell. PMID:16270218

Chromosome organizaton in simple and complex unicellular organisms.

PubMed

O'Sullivan, Justin M

2011-01-01

The genomes of unicellular organisms form complex 3-dimensional structures. This spatial organization is hypothesized to have a significant role in genomic function. Spatial organization is not limited solely to the three-dimensional folding of the chromosome(s) in genomes but also includes genome positioning, and the folding and compartmentalization of any additional genetic material (e.g. episomes) present within complex genomes. In this comment, I will highlight similarities in the spatial organization of eukaryotic and prokaryotic unicellular genomes.

Temporal and spatial coordination of chromosome movement, spindle formation, and nuclear envelope breakdown during prometaphase in Drosophila melanogaster embryos.

PubMed

Hiraoka, Y; Agard, D A; Sedat, J W

1990-12-01

The spatial and temporal dynamics of diploid chromosome organization, microtubule arrangement, and the state of the nuclear envelope have been analyzed in syncytial blastoderm embryos of Drosophila melanogaster during the transition from prophase to metaphase, by three-dimensional optical sectioning microscopy. Time-lapse, three-dimensional data recorded in living embryos revealed that congression of chromosomes (the process whereby chromosomes move to form the metaphase plate) at prometaphase occurs as a wave, starting at the top of the nucleus near the embryo surface and proceeding through the nucleus to the bottom. The time-lapse analysis was augmented by a high-resolution analysis of fixed embryos where it was possible to unambiguously trace the three-dimensional paths of individual chromosomes. In prophase, the centromeres were found to be clustered at the top of the nucleus while the telomeres were situated at the bottom of the nucleus or towards the embryo interior. This polarized centromere-telomere orientation, perpendicular to the embryo surface, was preserved during the process of prometaphase chromosome congression. Correspondingly, breakdown of the nuclear envelope started at the top of the nucleus with the mitotic spindle being formed at the positions of the partial breakdown of the nuclear envelope. Our observation provide an example in which nuclear structures are spatially organized and their functions are locally and coordinately controlled in three dimensions.

Cell-autonomous correction of ring chromosomes in human induced pluripotent stem cells

NASA Astrophysics Data System (ADS)

Bershteyn, Marina; Hayashi, Yohei; Desachy, Guillaume; Hsiao, Edward C.; Sami, Salma; Tsang, Kathryn M.; Weiss, Lauren A.; Kriegstein, Arnold R.; Yamanaka, Shinya; Wynshaw-Boris, Anthony

2014-03-01

Ring chromosomes are structural aberrations commonly associated with birth defects, mental disabilities and growth retardation. Rings form after fusion of the long and short arms of a chromosome, and are sometimes associated with large terminal deletions. Owing to the severity of these large aberrations that can affect multiple contiguous genes, no possible therapeutic strategies for ring chromosome disorders have been proposed. During cell division, ring chromosomes can exhibit unstable behaviour leading to continuous production of aneuploid progeny with low viability and high cellular death rate. The overall consequences of this chromosomal instability have been largely unexplored in experimental model systems. Here we generated human induced pluripotent stem cells (iPSCs) from patient fibroblasts containing ring chromosomes with large deletions and found that reprogrammed cells lost the abnormal chromosome and duplicated the wild-type homologue through the compensatory uniparental disomy (UPD) mechanism. The karyotypically normal iPSCs with isodisomy for the corrected chromosome outgrew co-existing aneuploid populations, enabling rapid and efficient isolation of patient-derived iPSCs devoid of the original chromosomal aberration. Our results suggest a fundamentally different function for cellular reprogramming as a means of `chromosome therapy' to reverse combined loss-of-function across many genes in cells with large-scale aberrations involving ring structures. In addition, our work provides an experimentally tractable human cellular system for studying mechanisms of chromosomal number control, which is of critical relevance to human development and disease.

Aneuploidy in spermatids of Robertsonian (Rb) chromosome heterozygous mice.

PubMed

Manieu, Catalina; González, Marisel; López-Fenner, Julio; Page, Jesús; Ayarza, Eliana; Fernández-Donoso, Raúl; Berríos, Soledad

2014-12-01

Rb translocations are chromosomal rearrangements frequently found in natural populations of the house mouse Mus musculus domesticus. The standard diploid karyotype of the house mouse consisting of 40 telocentric chromosomes may be reduced by the emergence of metacentric Rb chromosomes. Multiple simple Rb heterozygotes form trivalents exhibiting higher anaphase nondisjunction frequency and consequently higher number of unbalanced gametes than in normal males. This work will attempt to establish whether frequencies of aneuploidy observed in heterozygote spermatids of the house mouse M. musculus domesticus show differences in chromosomes derived from different trivalents. Towards this goal, the number and distribution frequency of aneuploidy was assessed via FISH staining of specific chromosomes of spermatids derived from 2n = 32 individuals. Our results showed that for a given set of target chromosomes, 90% of the gametes were balanced, resulting from alternate segregation, and that there were no differences (approx. 10%) in aneuploidy frequencies in chromosomes derived from different trivalents. These observations suggest that segregation effectiveness does not depend on the type of chromosomes involved in trivalents. As a consequence of the trivalent's configuration, joint segregation of the telocentric chromosomes occurs thus favoring their appearance together in early spermatids. Our data suggest that Rb chromosomes and their telocentric homologs are subject to architectural constraints placing them close to each other. This proximity may ultimately facilitate fusion between them, hence contributing to a prevalence of Rb metacentric chromosomes.

Proximity within interphase chromosome contributes to the breakpoint distribution in radiation-induced intrachromosomal exchanges

NASA Astrophysics Data System (ADS)

Zhang, Ye; Uhlemeyer, Jimmy; Hada, Megumi; Asaithamby, A.; Chen, David J.; Wu, Honglu

2014-07-01

Previously, we reported that breaks involved in chromosome aberrations were clustered in several regions of chromosome 3 in human mammary epithelial cells after exposures to either low- or high-LET radiation. In particular, breaks in certain regions of the chromosome tended to rejoin with each other to form an intrachromosome exchange event. This study tests the hypothesis that proximity within a single chromosome in interphase cell nuclei contributes to the distribution of radiation-induced chromosome breaks. Chromosome 3 in G1 human mammary epithelial cells was hybridized with the multicolor banding in situ hybridization (mBAND) probes that distinguish the chromosome in six differently colored regions, and the location of these regions was measured with a laser confocal microscope. Results of the study indicated that, on a multi-mega base pair scale of the DNA, the arrangement of chromatin was non-random. Both telomere regions tended to be located towards the exterior of the chromosome domain, whereas the centromere region towards the interior. In addition, the interior of the chromosome domain was preferentially occupied by the p-arm of the chromatin, which is consistent with our previous finding of intrachromosome exchanges involving breaks on the p-arm and in the centromere region of chromosome 3. Other factors, such as the fragile sites in the 3p21 band and gene regulation, may also contribute to the breakpoint distribution in radiation-induced chromosome aberrations.

Chromosome specific repetitive DNA sequences

DOEpatents

Moyzis, Robert K.; Meyne, Julianne

1991-01-01

A method is provided for determining specific nucleotide sequences useful in forming a probe which can identify specific chromosomes, preferably through in situ hybridization within the cell itself. In one embodiment, chromosome preferential nucleotide sequences are first determined from a library of recombinant DNA clones having families of repetitive sequences. Library clones are identified with a low homology with a sequence of repetitive DNA families to which the first clones respectively belong and variant sequences are then identified by selecting clones having a pattern of hybridization with genomic DNA dissimilar to the hybridization pattern shown by the respective families. In another embodiment, variant sequences are selected from a sequence of a known repetitive DNA family. The selected variant sequence is classified as chromosome specific, chromosome preferential, or chromosome nonspecific. Sequences which are classified as chromosome preferential are further sequenced and regions are identified having a low homology with other regions of the chromosome preferential sequence or with known sequences of other family me This invention is the result of a contract with the Department of Energy (Contract No. W-7405-ENG-36).

Computer graphics of SEM images facilitate recognition of chromosome position in isolated human metaphase plates.

PubMed

Hodge, L D; Barrett, J M; Welter, D A

1995-04-01

There is general agreement that at the time of mitosis chromosomes occupy precise positions and that these positions likely affect subsequent nuclear function in interphase. However, before such ideas can be investigated in human cells, it is necessary to determine first the precise position of each chromosome with regard to its neighbors. It has occurred to us that stereo images, produced by scanning electron microscopy, of isolated metaphase plates could form the basis whereby these positions could be ascertained. In this paper we describe a computer graphic technique that permits us to keep track of individual chromosomes in a metaphase plate and to compare chromosome positions in different metaphase plates. Moreover, the computer graphics provide permanent, easily manipulated, rapid recall of stored chromosome profiles. These advantages are demonstrated by a comparison of the relative position of group A-specific and groups D- and G-specific chromosomes to the full complement of chromosomes in metaphase plates isolated from a nearly triploid human-derived cell (HeLa S3) to a hypo-diploid human fetal lung cell.

Alternative meiotic chromatid segregation in the holocentric plant Luzula elegans

PubMed Central

Heckmann, Stefan; Jankowska, Maja; Schubert, Veit; Kumke, Katrin; Ma, Wei; Houben, Andreas

2014-01-01

Holocentric chromosomes occur in a number of independent eukaryotic lineages. They form holokinetic kinetochores along the entire poleward chromatid surfaces, and owing to this alternative chromosome structure, species with holocentric chromosomes cannot use the two-step loss of cohesion during meiosis typical for monocentric chromosomes. Here we show that the plant Luzula elegans maintains a holocentric chromosome architecture and behaviour throughout meiosis, and in contrast to monopolar sister centromere orientation, the unfused holokinetic sister centromeres behave as two distinct functional units during meiosis I, resulting in sister chromatid separation. Homologous non-sister chromatids remain terminally linked after metaphase I, by satellite DNA-enriched chromatin threads, until metaphase II. They then separate at anaphase II. Thus, an inverted sequence of meiotic sister chromatid segregation occurs. This alternative meiotic process is most likely one possible adaptation to handle a holocentric chromosome architecture and behaviour during meiosis. PMID:25296379

Characterization of a complex chromosomal rearrangement using chromosome, FISH, and microarray assays in a girl with multiple congenital abnormalities and developmental delay

PubMed Central

2014-01-01

Complex chromosomal rearrangements (CCRs) are balanced or unbalanced structural rearrangements involving three or more cytogenetic breakpoints on two or more chromosomal pairs. The phenotypic anomalies in such cases are attributed to gene disruption, superimposed cryptic imbalances in the genome, and/or position effects. We report a 14-year-old girl who presented with multiple congenital anomalies and developmental delay. Chromosome and FISH analysis indicated a highly complex chromosomal rearrangement involving three chromosomes (3, 7 and 12), seven breakpoints as a result of one inversion, two insertions, and two translocations forming three derivative chromosomes. Additionally, chromosomal microarray study (CMA) revealed two submicroscopic deletions at 3p12.3 (467 kb) and 12q13.12 (442 kb). We postulate that microdeletion within the ROBO1 gene at 3p12.3 may have played a role in the patient’s developmental delay, since it has potential activity-dependent role in neurons. Additionally, factors other than genomic deletions such as loss of function or position effects may also contribute to the abnormal phenotype in our patient. PMID:25478007

Regulation of X-chromosome dosage compensation in human: mechanisms and model systems.

PubMed

Sahakyan, Anna; Plath, Kathrin; Rougeulle, Claire

2017-11-05

The human blastocyst forms 5 days after one of the smallest human cells (the sperm) fertilizes one of the largest human cells (the egg). Depending on the sex-chromosome contribution from the sperm, the resulting embryo will either be female, with two X chromosomes (XX), or male, with an X and a Y chromosome (XY). In early development, one of the major differences between XX female and XY male embryos is the conserved process of X-chromosome inactivation (XCI), which compensates gene expression of the two female X chromosomes to match the dosage of the single X chromosome of males. Most of our understanding of the pre-XCI state and XCI establishment is based on mouse studies, but recent evidence from human pre-implantation embryo research suggests that many of the molecular steps defined in the mouse are not conserved in human. Here, we will discuss recent advances in understanding the control of X-chromosome dosage compensation in early human embryonic development and compare it to that of the mouse.This article is part of the themed issue 'X-chromosome inactivation: a tribute to Mary Lyon'. © 2017 The Author(s).

Proximity Within Interphase Chromosome Contributes to the Breakpoint Distribution in Radiation-Induced Intrachromosomal Exchanges

NASA Technical Reports Server (NTRS)

Zhang, Ye; Uhlemeyer, Jimmy; Hada, Megumi; Asaithamby, A.; Chen, David J.; Wu, Honglu

2015-01-01

Previously, we reported that breaks involved in chromosome aberrations were clustered in several regions of chromosome3 in human mammary epithelial cells after exposures to either low-or high-LET radiation. In particular, breaks in certain regions of the chromosome tended to rejoin with each other to form an intrachromosome exchange event. This study tests the hypothesis that proximity within a single chromosome in interphase cell nuclei contributes to the distribution of radiation-induced chromosome breaks. Chromosome 3 in G1 human mammary epithelial cells was hybridized with the multicolor banding in situ hybridization (mBAND) probes that distinguish the chromosome in six differently colored regions, and the location of these regions was measured with a laser confocal microscope. Results of the study indicated that, on a multi-mega base pair scale of the DNA, the arrangement of chromatin was non-random. Both telomere regions tended to be located towards the exterior of the chromosome domain, whereas the centromere region towards the interior. In addition, the interior of the chromosome domain was preferentially occupied by the p-arm of the chromatin, which is consistent with our previous finding of intrachromosome exchanges involving breaks on the p-arm and in the centromere region of chromosome3. Other factors, such as the fragile sites in the 3p21 band and gene regulation, may also contribute to the breakpoint distribution in radiation-induced chromosome aberrations. Further investigations suggest that the 3D chromosome folding is cell type and culture condition dependent.

Annealing Vs. Invasion in Phage λ Recombination

PubMed Central

Stahl, M. M.; Thomason, L.; Poteete, A. R.; Tarkowski, T.; Kuzminov, A.; Stahl, F. W.

1997-01-01

Genetic recombination catalyzed by λ's Red pathway was studied in rec(+) and recA mutant bacteria by examining both intracellular λ DNA and mature progeny particles. Recombination of nonreplicating phage chromosomes was induced by double-strand breaks delivered at unique sites in vivo. In rec(+) cells, cutting only one chromosome gave nearly maximal stimulation of recombination; the recombinants formed contained relatively short hybrid regions, suggesting strand invasion. In contrast, in recA mutant cells, cutting the two parental chromosomes at non-allelic sites was required for maximal stimulation; the recombinants formed tended to be hybrid over the entire region between the two cuts, implying strand annealing. We conclude that, in the absence of RecA and the presence of non-allelic DNA ends, the Red pathway of λ catalyzes recombination primarily by annealing. PMID:9383045

Differentiation and Evolution of the W Chromosome in the Fish Species of Megaleporinus (Characiformes, Anostomidae).

PubMed

Caetano de Barros, Lucas; Piscor, Diovani; Parise-Maltempi, Patricia P; Feldberg, Eliana

2018-06-08

The W chromosome of Megaleporinus trifasciatus was isolated in order to analyze its behavior in the karyotype of this and other species of the family, including forms with differentiated and undifferentiated sex chromosomes. The chromosome was microdissected, and the WMt probe was prepared for the chromosome painting procedure. M. trifasciatus was also cross-hybridized (cross-FISH) using existing probes available for M. macrocephalus (WMm) and M. elongatus (WMe). Two Leporinus species and Semaprochilodus taeniurus, representing a clade close to the Anostomidae, were also cross-hybridized with the objective to better understand the evolution of the sex chromosomes. In the metaphase of female M. trifasciatus, the WMt probe highlighted the whole long arm of the W chromosome and a small, distal portion of the long arm of the Z chromosome. In males, the probe highlighted the distal portion of the long arm of the Z chromosomes. The hybridization of female M. trifasciatus with the WMe and WMm probes revealed a pattern similar to that encountered using the WMt probe. The WMt, WMm, and WMe probes revealed broad similarities among the species of the genus Megaleporinus, which has a ZZ/ZW system of sex chromosomes, with only minor alterations becoming apparent when analyzed separately. © 2018 S. Karger AG, Basel.

A new model of sperm nuclear architecture following assessment of the organization of centromeres and telomeres in three-dimensions.

PubMed

Ioannou, Dimitrios; Millan, Nicole M; Jordan, Elizabeth; Tempest, Helen G

2017-01-31

The organization of chromosomes in sperm nuclei has been proposed to possess a unique "hairpin-loop" arrangement, which is hypothesized to aid in the ordered exodus of the paternal genome following fertilization. This study simultaneously assessed the 3D and 2D radial and longitudinal organization of telomeres, centromeres, and investigated whether chromosomes formed the same centromere clusters in sperm cells. Reproducible radial and longitudinal non-random organization was observed for all investigated loci using both 3D and 2D approaches in multiple subjects. We report novel findings, with telomeres and centromeres being localized throughout the nucleus but demonstrating roughly a 1:1 distribution in the nuclear periphery and the intermediate regions with <15% occupying the nuclear interior. Telomeres and centromeres were observed to aggregate in sperm nuclei, forming an average of 20 and 7 clusters, respectively. Reproducible longitudinal organization demonstrated preferential localization of telomeres and centromeres in the mid region of the sperm cell. Preliminary evidence is also provided to support the hypothesis that specific chromosomes preferentially form the same centromere clusters. The more segmental distribution of telomeres and centromeres as described in this study could more readily accommodate and facilitate the sequential exodus of paternal chromosomes following fertilization.

A new model of sperm nuclear architecture following assessment of the organization of centromeres and telomeres in three-dimensions

PubMed Central

Ioannou, Dimitrios; Millan, Nicole M.; Jordan, Elizabeth; Tempest, Helen G.

2017-01-01

The organization of chromosomes in sperm nuclei has been proposed to possess a unique “hairpin-loop” arrangement, which is hypothesized to aid in the ordered exodus of the paternal genome following fertilization. This study simultaneously assessed the 3D and 2D radial and longitudinal organization of telomeres, centromeres, and investigated whether chromosomes formed the same centromere clusters in sperm cells. Reproducible radial and longitudinal non-random organization was observed for all investigated loci using both 3D and 2D approaches in multiple subjects. We report novel findings, with telomeres and centromeres being localized throughout the nucleus but demonstrating roughly a 1:1 distribution in the nuclear periphery and the intermediate regions with <15% occupying the nuclear interior. Telomeres and centromeres were observed to aggregate in sperm nuclei, forming an average of 20 and 7 clusters, respectively. Reproducible longitudinal organization demonstrated preferential localization of telomeres and centromeres in the mid region of the sperm cell. Preliminary evidence is also provided to support the hypothesis that specific chromosomes preferentially form the same centromere clusters. The more segmental distribution of telomeres and centromeres as described in this study could more readily accommodate and facilitate the sequential exodus of paternal chromosomes following fertilization. PMID:28139771

Formation of chromosomal domains in interphase by loop extrusion

NASA Astrophysics Data System (ADS)

Fudenberg, Geoffrey

While genomes are often considered as one-dimensional sequences, interphase chromosomes are organized in three dimensions with an essential role for regulating gene expression. Recent studies have shown that Topologically Associating Domains (TADs) are fundamental structural and functional building blocks of human interphase chromosomes. Despite observations that architectural proteins, including CTCF, demarcate and maintain the borders of TADs, the mechanisms underlying TAD formation remain unknown. Here we propose that loop extrusion underlies the formation TADs. In this process, cis-acting loop-extruding factors, likely cohesins, form progressively larger loops, but stall at TAD boundaries due to interactions with boundary proteins, including CTCF. This process dynamically forms loops of various sizes within but not between TADs. Using polymer simulations, we find that loop extrusion can produce TADs as determined by our analyses of the highest-resolution experimental data. Moreover, we find that loop extrusion can explain many diverse experimental observations, including: the preferential orientation of CTCF motifs and enrichments of architectural proteins at TAD boundaries; TAD boundary deletion experiments; and experiments with knockdown or depletion of CTCF, cohesin, and cohesin-loading factors. Together, the emerging picture from our work is that TADs are formed by rapidly associating, growing, and dissociating loops, presenting a clear framework for understanding interphase chromosomal organization.

Micromechanical study of mitotic chromosome structure

NASA Astrophysics Data System (ADS)

Marko, John

2011-03-01

Our group has developed micromanipulation techniques for study of the highly compacted mitotic form of chromosome found in eukaryote cells during cell division. Each metaphase chromosome contains two duplicate centimeter-long DNA molecules, folded up by proteins into cylindrical structures several microns in length. Native chromosomes display linear and reversible stretching behavior over a wide range of extensions (up to 5x native length for amphibian chromosomes), described by a Young modulus of about 300 Pa. Studies using DNA-cutting and protein-cutting enzymes have revealed that metaphase chromosomes behave as a network of chromatin fibers held together by protein-based isolated crosslinks. Our results are not consistent with the more classical model of loops of chromatin attached to a protein-based structural organizer or ``scaffold". In short, our experiments indicate that metaphase chromosomes can be considered to be ``gels" of chromatin; the stretching modulus of a whole chromosome is consistent with stretching of the chromatin fibers contained within it. Experiments using topoisomerases suggest that topological constraints may play an appreciable role in confining chromatin in the metaphase chromosome. Finally, recent experiments on human chromosomes will be reviewed, including results of experiments where chromosome-folding proteins are specifically depleted using siRNA methods. Supported by NSF-MCB-1022117, DMR-0715099, PHY-0852130, DMR-0520513, NCI 1U54CA143869-01 (NU-PS-OC), and the American Heart Association.

Cytogenetic studies on Metasequoia glyptostroboides, a living fossil species.

PubMed

He, Zican; Li, Jianqiang; Cai, Qing; Li, Xiaodong; Huang, Hongwen

2004-11-01

The chromosome morphology and meiotic pairing behavior in the pollen mother cells (PMCs) of Metasequoia glyptostroboides were investigated. The results showed that: (1) The chromosome number of the PMCs was 2n = 22. (2) The PMCs developed in the successive manner, and the nucleoids in the dynamic development were similar to those of the other gymnosperms. (3) At prophase, most of the chromosomes were unable to be identified distinctively because the chromosomes were long and tangled together. The chromosome segments were paired non-synchronously. At pachytene, the interstitial or terminal regions of some bivalents did not form synapsis and the paired chromosomes showed difference in sizes, indicating that there were structure differences between the homologous chromosomes. (4) At diakinesis, the ring bivalents showed complicated configurations due to the differences in location and number of chiasmata. In addition, there were cross-linked bivalents. (5) At metaphase I, the chromosome configuration of each cell was 8.2II(0) + 1.1II + 1.3II+ + 0.8I. Most of the chromosomes were ring bivalents, but some were cross-linked bivalents, rod bivalents, or univalents. (6) 15% PMCs at anaphase I and 22% PMCs at anaphase II presented chromosome bridges, chromosome fragments, micronuclei, and lagging chromosomes. Twenty seven percent microspores finally moved into one to three micronuclei. Twenty five percent pollens were abortive. The results indicated that the observed individual of M. glyptostroboides was probably a paracentric inversion heterozygote, and there were structural and behavioral differences between the homologous chromosomes. The chromosomal aberration of M. glyptostroboides may play an important role in the evolution of this relict species, which is known as a living fossil. Further evidence is needed to test whether the differences between homologous chromosomes were due to hybridization.

Indoor residual spraying with micro-encapsulated pirimiphos-methyl (Actellic® 300CS) against malaria vectors in the Lake Victoria basin, Tanzania

PubMed Central

Manjurano, Alphaxard; Kinung’hi, Safari; Martine, Jackline; Lyimo, Eric; Kishamawe, Coleman; Ndege, Chacha; Ramsan, Mahdi M.; Chan, Adeline; Mwalimu, Charles D.; Changalucha, John; Magesa, Stephen

2017-01-01

Background The indoor residual spraying programme for malaria vectors control was implemented in four districts of the Lake Victoria basin of Tanzania namely Ukerewe, Sengerema, Rorya andSerengeti. Entomological monitoring activities were implemented in one sentinel village in each district to evaluate the efficacy of pirimiphos-methyl 300 CS sprayed on different wall surfaces and its impact against malaria vectors post-IRS intervention. Methods The residual decay rate of p-methyl 300 CS applied at a target dosage of 1g a.i./m2 on thesprayed wall surfaces was monitored for a period of 43 weeks post-IRSusing the WHO cone wall bioassay method. The bioassays were performed by exposing 2–5 days old unfed susceptible female Anopheles gambiae s.s. (Kisumu strain) to sprayed wall surfaces for a period of 30 minutes. In each sentinel village, mosquito collection was carried out by trained community mosquito collectors. Monthly mosquito collections were carried out from 6.00pm to 6.00am using CDC light traps and clay pot methods for indoors host seekingand outdoors resting mosquitoes respectively. Six traps (2 CDC light traps and 4 clay pots) were set per sentinel village per night for28 consecutive days in a moon. PCR and ELISA were used for mosquito species identification and sporozoite detection, respectively. Results Based on the WHOPES recommendation, insecticides should have a minimum efficacy of ≥ 80% mosquito mortality at 24 hours post exposure on the sprayed wall surfaces to be considered effective. In this study, p-methyl 300 CS was demonstrated to have a long residual efficacy of 21–43 weeks post-IRS on mud, cement, painted and wood wall surfaces. Numberof anopheline mosquitoes decreased post-IRS interventions in all sentinel villages. The highest numbers ofanopheline mosquitoes were collected in November-December, 38–43 weeks post-IRS. A total of 270 female anopheline mosquitoes were analyzed by PCR; out of which 236 (87.4%) were An. gambiae s.l. and 34 (12.6%) were An. funestus group. Of the 236 An. gambiae s.l.identified 12.6% (n = 34) were An. gambiae s.s. and 68.6% (n = 162) were An. arabiensis. Ofthe 34 An. funestus group indentified 91.2% (n = 31) were An. parensis and 8.8% (n = 3) were An. rivulorum. The overall Plasmodium falciparum sporozoite rate was 0.7% (n = 2,098). Conclusions Pirimiphos-methyl 300 CS was found to be effective for IRS in the Lake Victoria basin,Tanzania. P-methyl 300 CShas a long residual efficacy on sprayed wall surfaces and therefore it is effective in controlling principal malaria vectors of An. gambiae s.l and An. funestus which rest on wall surfaces after and before feeding. PMID:28489935

Single molecule analysis of Trypanosoma brucei DNA replication dynamics

PubMed Central

Calderano, Simone Guedes; Drosopoulos, William C.; Quaresma, Marina Mônaco; Marques, Catarina A.; Kosiyatrakul, Settapong; McCulloch, Richard; Schildkraut, Carl L.; Elias, Maria Carolina

2015-01-01

Eukaryotic genome duplication relies on origins of replication, distributed over multiple chromosomes, to initiate DNA replication. A recent genome-wide analysis of Trypanosoma brucei, the etiological agent of sleeping sickness, localized its replication origins to the boundaries of multigenic transcription units. To better understand genomic replication in this organism, we examined replication by single molecule analysis of replicated DNA. We determined the average speed of replication forks of procyclic and bloodstream form cells and we found that T. brucei DNA replication rate is similar to rates seen in other eukaryotes. We also analyzed the replication dynamics of a central region of chromosome 1 in procyclic forms. We present evidence for replication terminating within the central part of the chromosome and thus emanating from both sides, suggesting a previously unmapped origin toward the 5′ extremity of chromosome 1. Also, termination is not at a fixed location in chromosome 1, but is rather variable. Importantly, we found a replication origin located near an ORC1/CDC6 binding site that is detected after replicative stress induced by hydroxyurea treatment, suggesting it may be a dormant origin activated in response to replicative stress. Collectively, our findings support the existence of more replication origins in T. brucei than previously appreciated. PMID:25690894

Single molecule analysis of Trypanosoma brucei DNA replication dynamics.

PubMed

Calderano, Simone Guedes; Drosopoulos, William C; Quaresma, Marina Mônaco; Marques, Catarina A; Kosiyatrakul, Settapong; McCulloch, Richard; Schildkraut, Carl L; Elias, Maria Carolina

2015-03-11

Eukaryotic genome duplication relies on origins of replication, distributed over multiple chromosomes, to initiate DNA replication. A recent genome-wide analysis of Trypanosoma brucei, the etiological agent of sleeping sickness, localized its replication origins to the boundaries of multigenic transcription units. To better understand genomic replication in this organism, we examined replication by single molecule analysis of replicated DNA. We determined the average speed of replication forks of procyclic and bloodstream form cells and we found that T. brucei DNA replication rate is similar to rates seen in other eukaryotes. We also analyzed the replication dynamics of a central region of chromosome 1 in procyclic forms. We present evidence for replication terminating within the central part of the chromosome and thus emanating from both sides, suggesting a previously unmapped origin toward the 5' extremity of chromosome 1. Also, termination is not at a fixed location in chromosome 1, but is rather variable. Importantly, we found a replication origin located near an ORC1/CDC6 binding site that is detected after replicative stress induced by hydroxyurea treatment, suggesting it may be a dormant origin activated in response to replicative stress. Collectively, our findings support the existence of more replication origins in T. brucei than previously appreciated. © The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.

Reactivation of Chromosomally Integrated Human Herpesvirus-6 by Telomeric Circle Formation

PubMed Central

Prusty, Bhupesh K.; Krohne, George; Rudel, Thomas

2013-01-01

More than 95% of the human population is infected with human herpesvirus-6 (HHV-6) during early childhood and maintains latent HHV-6 genomes either in an extra-chromosomal form or as a chromosomally integrated HHV-6 (ciHHV-6). In addition, approximately 1% of humans are born with an inheritable form of ciHHV-6 integrated into the telomeres of chromosomes. Immunosuppression and stress conditions can reactivate latent HHV-6 replication, which is associated with clinical complications and even death. We have previously shown that Chlamydia trachomatis infection reactivates ciHHV-6 and induces the formation of extra-chromosomal viral DNA in ciHHV-6 cells. Here, we propose a model and provide experimental evidence for the mechanism of ciHHV-6 reactivation. Infection with Chlamydia induced a transient shortening of telomeric ends, which subsequently led to increased telomeric circle (t-circle) formation and incomplete reconstitution of circular viral genomes containing single viral direct repeat (DR). Correspondingly, short t-circles containing parts of the HHV-6 DR were detected in cells from individuals with genetically inherited ciHHV-6. Furthermore, telomere shortening induced in the absence of Chlamydia infection also caused circularization of ciHHV-6, supporting a t-circle based mechanism for ciHHV-6 reactivation. PMID:24367281

Neo-sex chromosome inheritance across species in Silene hybrids.

PubMed

Weingartner, L A; Delph, L F

2014-07-01

Neo-sex chromosomes, which form through the major restructuring of ancestral sex chromosome systems, have evolved in various taxa. Such restructuring often consists of the fusion of an autosome to an existing sex chromosome, resulting in novel sex chromosome formations (e.g. X1X2Y or XY1Y2.). Comparative studies are often made between restructured sex chromosome systems of closely related species, and here we evaluate the consequences of variable sex chromosome systems to hybrids. If neo-sex chromosomes are improperly inherited across species, this could lead to aberrant development and reproductive isolation. In this study, we examine the fate of neo-sex chromosomes in hybrids of the flowering plants Silene diclinis and Silene latifolia. Silene diclinis has a neo-sex chromosome system (XY1Y2) that is thought to have evolved from an ancestral XY system that is still present in S. latifolia. These species do not hybridize naturally, and improper sex chromosome inheritance could contribute to reproductive isolation. We investigated whether this major restructuring of sex chromosomes prevents their proper inheritance in a variety of hybrid crosses, including some F2 - and later-generation hybrids, with sex chromosome-linked, species-specific, polymorphic markers and chromosome squashes. We discovered that despite the differences in sex chromosomes that exist between these two species, proper segregation had occurred in hybrids that made it to flowering, including later-generation hybrids, indicating that neo-sex chromosome formation alone does not result in complete reproductive isolation between these two species. Additionally, hybrids with aberrant sex expression (e.g. neuter, hermaphrodite) also inherited the restructured sex chromosomes properly, highlighting that issues with sexual development in hybrids can be caused by intrinsic genetic incompatibility rather than improper sex chromosome inheritance. © 2014 The Authors. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

Centralspindlin and Chromosomal Passenger Complex Behavior During Normal and Rappaport Furrow Specification in Echinoderm Embryos

PubMed Central

Argiros, Haroula; Henson, Lauren; Holguin, Christiana; Foe, Victoria; Shuster, Charles Bradley

2014-01-01

The chromosomal passenger (CPC) and Centralspindlin complexes are essential for organizing the anaphase central spindle and providing cues that position the cytokinetic furrow between daughter nuclei. However, echinoderm zygotes are also capable of forming “Rappaport furrows” between asters positioned back-to-back without intervening chromosomes. To understand how these complexes contribute to normal and Rappaport furrow formation, we studied the localization patterns of Survivin and mitotic-kinesin-like-protein1 (MKLP1), members respectively of the CPC and the Centralspindlin complex, and the effect of CPC inhibition on cleavage in mono- and binucleate echinoderm zygotes. In zygotes, Survivin initially localized to metaphase chromosomes, upon anaphase onset relocalized to the central spindle and then, together with MKLP1 spread towards the equatorial cortex in an Aurora-dependent manner. Inhibition of Aurora kinase activity resulted in disruption of central spindle organization and furrow regression, although astral microtubule elongation and furrow initiation were normal. In binucleate cells containing two parallel spindles MKLP1 and Survivin localized to the plane of the former metaphase plate, but were not observed in the secondary cleavage plane formed between unrelated spindle poles, except when chromosomes were abnormally present there. However, the secondary furrow was sensitive to Aurora inhibition, indicating that Aurora kinase may still contribute to furrow ingression without chromosomes nearby. Our results provide insights that reconcile classic micromanipulation studies with current molecular understanding of furrow specification in animal cells. PMID:22887753

Structure and Barr body formation of an Xp + chromosome with two inactivation centers.

PubMed Central

Daly, R F; Patau, K; Therman, E; Sarto, G E

1977-01-01

A patients with seizures, Von Willebrand disease, and symptoms of Turner syndrome was a chromosomal mosaic. In blood culture (1974), 56% of the cells were 45, X 33% 46, XXp+ and 11% 47,XXp + Xp +; in the skin, no cells with 47 chromosomes were found. Presumably the Xp + chromosome arose through a break in the Q-banded dark region next to the centromere on Xp to which an Xq had been attached. The abnormal X was late-labeling and formed a larger than normal Barr body. Of the chromatin-positive fibroblasts, 18.2% showed bipartite Barr bodies, which agrees with the hypothesis that the X inactivation center lies on the proximal part of the Xq. On the basis of the structure and behavior of the bipartite bodies in the present patient, as compared to those formed by other chromosomes with two presumed inactivation centers, we propose that the dark region next to the centromere of Xp remains active in the inactive X. In cells with 45,X and 46,XY, this region has the same relative size, whereas it is significantly shorter in the active X of three females, including the present patient, with one abnormal X. We propose that this region on the active X reveals different states of activity, as reflected in its length, depending on how many other X chromosomes are in the cell. Images Fig. 1 Fig. 2 Fig. 3 PMID:299980

Origin of the chromosomal radiation of Madeiran house mice: a microsatellite analysis of metacentric chromosomes

PubMed Central

Förster, D W; Mathias, M L; Britton-Davidian, J; Searle, J B

2013-01-01

Chromosome races of Mus musculus domesticus are characterised by particular sets of metacentric chromosomes formed by Robertsonian fusions and whole-arm reciprocal translocations. The Atlantic island of Madeira is inhabited by six chromosome races of house mice with 6–9 pairs of metacentric chromosomes. Three of these races are characterised by the metacentric 3.8 also found elsewhere in the distribution of M. m. domesticus, including Denmark and Spain. We investigated the possibility that metacentric 3.8 was introduced to Madeira during the initial colonisation, as this could have ‘seeded' the cascade of chromosomal mutation that is the basis of the extraordinary chromosomal radiation observed on the island. Variation at 24 microsatellite loci mapping to three different chromosomal regions (proximal, interstitial and distal) of mouse chromosomes 3 and 8 was investigated in 179 mice from Madeira, Denmark, Portugal, Spain, Italy and Scotland. Analyses of microsatellite loci closely linked to the centromeres of these chromosomes (‘proximal loci') do not support a common evolutionary origin of metacentric 3.8 among Madeiran, Danish and Spanish mouse populations. Our results suggest that Madeiran mice are genetically more similar to standard karyotype mice from Portugal than to metacentric mice from elsewhere. There is expected to be an interruption to gene flow between hybridising metacentric races on Madeira, particularly in the chromosomal regions close to the rearrangement breakpoints. Consistent with this, relating to differentiation involving chromosomes 3 and 8 on Madeira, we found greater genetic structure among races for proximal than interstitial or distal loci. PMID:23232832

Structure, organization, and sequence of alpha satellite DNA from human chromosome 17: evidence for evolution by unequal crossing-over and an ancestral pentamer repeat shared with the human X chromosome.

PubMed

Waye, J S; Willard, H F

1986-09-01

The centromeric regions of all human chromosomes are characterized by distinct subsets of a diverse tandemly repeated DNA family, alpha satellite. On human chromosome 17, the predominant form of alpha satellite is a 2.7-kilobase-pair higher-order repeat unit consisting of 16 alphoid monomers. We present the complete nucleotide sequence of the 16-monomer repeat, which is present in 500 to 1,000 copies per chromosome 17, as well as that of a less abundant 15-monomer repeat, also from chromosome 17. These repeat units were approximately 98% identical in sequence, differing by the exclusion of precisely 1 monomer from the 15-monomer repeat. Homologous unequal crossing-over is suggested as a probable mechanism by which the different repeat lengths on chromosome 17 were generated, and the putative site of such a recombination event is identified. The monomer organization of the chromosome 17 higher-order repeat unit is based, in part, on tandemly repeated pentamers. A similar pentameric suborganization has been previously demonstrated for alpha satellite of the human X chromosome. Despite the organizational similarities, substantial sequence divergence distinguishes these subsets. Hybridization experiments indicate that the chromosome 17 and X subsets are more similar to each other than to the subsets found on several other human chromosomes. We suggest that the chromosome 17 and X alpha satellite subsets may be related components of a larger alphoid subfamily which have evolved from a common ancestral repeat into the contemporary chromosome-specific subsets.

Efect of tri-species chromosome shuffling on agronomic and fiber traits in Upland cotton

USDA-ARS?s Scientific Manuscript database

Gossypium barbadense (L.), G. tomentosum (Seem.), G. mustelinum (Watt.) and G. darwinii (Watt.) are in the primary gene pool of Upland cotton (G. hirsutum). They share a common chromosome number (2n=52), similar AD-genome architecture, and form reasonably fertile F1 hybrids. However, reduced transm...

Chromosomal characterization of Arvicanthis species (Rodentia, Murinae) from western and central Africa: implications for taxonomy.

PubMed

Volobouev, V T; Ducroz, J F; Aniskin, V M; Britton-Davidian, J; Castiglia, R; Dobigny, G; Granjon, L; Lombard, M; Corti, M; Sicard, B; Capanna, E

2002-01-01

A chromosome study of unstriped grass rats of the genus Arvicanthis (Rodentia, Murinae) in western and central Africa is presented. The observations extend the data available to 242 specimens from 59 localities. All individuals karyotyped belong to four karyotypic forms, or cytotypes, earlier described as ANI-1, ANI-2, ANI-3, and ANI-4 and are presumed to correspond to four distinct species. In order to provide diagnostic characters for these western and one central African Arvicanthis species, we standardized the chromosomal data available and developed a G- and C-banded chromosome nomenclature that allows easy species identification. Each form is characterized by a distinct geographical distribution, roughly following the biogeographical domains of western Africa, although their precise limits remain to be assessed. The sole area of sympatry detected is the region of the inner delta of the Niger River, where both ANI-1 and ANI-3 can be found. It is proposed that the three western African species ANI-1, ANI-3, and ANI-4 be renamed as A. niloticus, A. ansorgei, and A. rufinus, respectively. Copyright 2002 S. Karger AG, Basel

The resurgence of haploids in higher plants.

PubMed

Forster, Brian P; Heberle-Bors, Erwin; Kasha, Ken J; Touraev, Alisher

2007-08-01

The life cycle of plants proceeds via alternating generations of sporophytes and gametophytes. The dominant and most obvious life form of higher plants is the free-living sporophyte. The sporophyte is the product of fertilization of male and female gametes and contains a set of chromosomes from each parent; its genomic constitution is 2n. Chromosome reduction at meiosis means cells of the gametophytes carry half the sporophytic complement of chromosomes (n). Plant haploid research began with the discovery that sporophytes can be produced in higher plants carrying the gametic chromosome number (n instead of 2n) and that their chromosome number can subsequently be doubled up by colchicine treatment. Recent technological innovations, greater understanding of underlying control mechanisms and an expansion of end-user applications has brought about a resurgence of interest in haploids in higher plants.

X-inactivation and X-reactivation: epigenetic hallmarks of mammalian reproduction and pluripotent stem cells.

PubMed

Payer, Bernhard; Lee, Jeannie T; Namekawa, Satoshi H

2011-08-01

X-chromosome inactivation is an epigenetic hallmark of mammalian development. Chromosome-wide regulation of the X-chromosome is essential in embryonic and germ cell development. In the male germline, the X-chromosome goes through meiotic sex chromosome inactivation, and the chromosome-wide silencing is maintained from meiosis into spermatids before the transmission to female embryos. In early female mouse embryos, X-inactivation is imprinted to occur on the paternal X-chromosome, representing the epigenetic programs acquired in both parental germlines. Recent advances revealed that the inactive X-chromosome in both females and males can be dissected into two elements: repeat elements versus unique coding genes. The inactive paternal X in female preimplantation embryos is reactivated in the inner cell mass of blastocysts in order to subsequently allow the random form of X-inactivation in the female embryo, by which both Xs have an equal chance of being inactivated. X-chromosome reactivation is regulated by pluripotency factors and also occurs in early female germ cells and in pluripotent stem cells, where X-reactivation is a stringent marker of naive ground state pluripotency. Here we summarize recent progress in the study of X-inactivation and X-reactivation during mammalian reproduction and development as well as in pluripotent stem cells.

The morbid anatomy of the human genome: chromosomal location of mutations causing disease.

PubMed Central

McKusick, V A; Amberger, J S

1993-01-01

Information is given in tabular form derived from a synopsis of the human gene map which has been updated continuously since 1973 as part of Mendelian Inheritance in Man (Johns Hopkins University Press, 10th ed, 1992) and of OMIM (Online Mendelian Inheritance in Man, available generally since 1987). The part of the synopsis reproduced here consists of chromosome by chromosome gene lists of loci for which there are associated disorders (table 1), a pictorial representation of this information (fig 1a-d), and an index of disorders for which the causative mutations have been mapped (table 2). In table 1, information on genes that have been located to specific chromosomal positions and are also the site of disease producing mutations is arranged by chromosome, starting with chromosome 1 and with the end of the short arm of the chromosome in each case. In table 2 an alphabetized list of these disorders and the chromosomal location of the mutation in each case are provided. Both in the 'Disorder' field of table 1 and in table 2, the numbers 1, 2, or 3 in parentheses after the name of the disorder indicate that its chromosomal location was determined by mapping of the wildtype gene (1), by mapping of the clinical phenotype (2), or by both strategies (3). PMID:8423603

Sequential de novo centromere formation and inactivation on a chromosomal fragment in maize.

PubMed

Liu, Yalin; Su, Handong; Pang, Junling; Gao, Zhi; Wang, Xiu-Jie; Birchler, James A; Han, Fangpu

2015-03-17

The ability of centromeres to alternate between active and inactive states indicates significant epigenetic aspects controlling centromere assembly and function. In maize (Zea mays), misdivision of the B chromosome centromere on a translocation with the short arm of chromosome 9 (TB-9Sb) can produce many variants with varying centromere sizes and centromeric DNA sequences. In such derivatives of TB-9Sb, we found a de novo centromere on chromosome derivative 3-3, which has no canonical centromeric repeat sequences. This centromere is derived from a 288-kb region on the short arm of chromosome 9, and is 19 megabases (Mb) removed from the translocation breakpoint of chromosome 9 in TB-9Sb. The functional B centromere in progenitor telo2-2 is deleted from derivative 3-3, but some B-repeat sequences remain. The de novo centromere of derivative 3-3 becomes inactive in three further derivatives with new centromeres being formed elsewhere on each chromosome. Our results suggest that de novo centromere initiation is quite common and can persist on chromosomal fragments without a canonical centromere. However, we hypothesize that when de novo centromeres are initiated in opposition to a larger normal centromere, they are cleared from the chromosome by inactivation, thus maintaining karyotype integrity.

Sequential de novo centromere formation and inactivation on a chromosomal fragment in maize

PubMed Central

Liu, Yalin; Su, Handong; Pang, Junling; Gao, Zhi; Wang, Xiu-Jie; Birchler, James A.; Han, Fangpu

2015-01-01

The ability of centromeres to alternate between active and inactive states indicates significant epigenetic aspects controlling centromere assembly and function. In maize (Zea mays), misdivision of the B chromosome centromere on a translocation with the short arm of chromosome 9 (TB-9Sb) can produce many variants with varying centromere sizes and centromeric DNA sequences. In such derivatives of TB-9Sb, we found a de novo centromere on chromosome derivative 3-3, which has no canonical centromeric repeat sequences. This centromere is derived from a 288-kb region on the short arm of chromosome 9, and is 19 megabases (Mb) removed from the translocation breakpoint of chromosome 9 in TB-9Sb. The functional B centromere in progenitor telo2-2 is deleted from derivative 3-3, but some B-repeat sequences remain. The de novo centromere of derivative 3-3 becomes inactive in three further derivatives with new centromeres being formed elsewhere on each chromosome. Our results suggest that de novo centromere initiation is quite common and can persist on chromosomal fragments without a canonical centromere. However, we hypothesize that when de novo centromeres are initiated in opposition to a larger normal centromere, they are cleared from the chromosome by inactivation, thus maintaining karyotype integrity. PMID:25733907

Loops determine the mechanical properties of mitotic chromosomes

NASA Astrophysics Data System (ADS)

Zhang, Yang; Heermann, Dieter W.

2013-03-01

In mitosis, chromosomes undergo a condensation into highly compacted, rod-like objects. Many models have been put forward for the higher-order organization of mitotic chromosomes including radial loop and hierarchical folding models. Additionally, mechanical properties of mitotic chromosomes under different conditions were measured. However, the internal organization of mitotic chromosomes still remains unclear. Here we present a polymer model for mitotic chromosomes and show how chromatin loops play a major role for their mechanical properties. The key assumption of the model is the ability of the chromatin fibre to dynamically form loops with the help of binding proteins. Our results show that looping leads to a tight compaction and significantly increases the bending rigidity of chromosomes. Moreover, our qualitative prediction of the force elongation behaviour is close to experimental findings. This indicates that the internal structure of mitotic chromosomes is based on self-organization of the chromatin fibre. We also demonstrate how number and size of loops have a strong influence on the mechanical properties. We suggest that changes in the mechanical characteristics of chromosomes can be explained by an altered internal loop structure. YZ gratefully appreciates funding by the German National Academic Foundation (Studienstiftung des deutschen Volkes) and support by the Heidelberg Graduate School for Mathematical and Computational Methods in the Sciences (HGS MathComp).

How did the platypus get its sex chromosome chain? A comparison of meiotic multiples and sex chromosomes in plants and animals.

PubMed

Gruetzner, Frank; Ashley, Terry; Rowell, David M; Marshall Graves, Jennifer A

2006-04-01

The duck-billed platypus is an extraordinary mammal. Its chromosome complement is no less extraordinary, for it includes a system in which ten sex chromosomes form an extensive meiotic chain in males. Such meiotic multiples are unprecedented in vertebrates but occur sporadically in plant and invertebrate species. In this paper, we review the evolution and formation of meiotic multiples in plants and invertebrates to try to gain insights into the origin of the platypus meiotic multiple. We describe the meiotic hurdles that translocated mammalian chromosomes face, which make longer chains disadvantageous in mammals, and we discuss how sex chromosomes and dosage compensation might have affected the evolution of sex-linked meiotic multiples. We conclude that the evolutionary conservation of the chain in monotremes, the structural properties of the translocated chromosomes and the highly accurate segregation at meiosis make the platypus system remarkably different from meiotic multiples in other species. We discuss alternative evolutionary models, which fall broadly into two categories: either the chain is the result of a sequence of translocation events from an ancestral pair of sex chromosomes (Model I) or the entire chain came into being at once by hybridization of two populations with different chromosomal rearrangements sharing monobrachial homology (Model II).

Superresolution microscopy reveals the three-dimensional organization of meiotic chromosome axes in intact Caenorhabditis elegans tissue

PubMed Central

Köhler, Simone; Wojcik, Michal; Dernburg, Abby F.

2017-01-01

When cells enter meiosis, their chromosomes reorganize as linear arrays of chromatin loops anchored to a central axis. Meiotic chromosome axes form a platform for the assembly of the synaptonemal complex (SC) and play central roles in other meiotic processes, including homologous pairing, recombination, and chromosome segregation. However, little is known about the 3D organization of components within the axes, which include cohesin complexes and additional meiosis-specific proteins. Here, we investigate the molecular organization of meiotic chromosome axes in Caenorhabditis elegans through STORM (stochastic optical reconstruction microscopy) and PALM (photo-activated localization microscopy) superresolution imaging of intact germ-line tissue. By tagging one axis protein (HIM-3) with a photoconvertible fluorescent protein, we established a spatial reference for other components, which were localized using antibodies against epitope tags inserted by CRISPR/Cas9 genome editing. Using 3D averaging, we determined the position of all known components within synapsed chromosome axes to high spatial precision in three dimensions. We find that meiosis-specific HORMA domain proteins span a gap between cohesin complexes and the central region of the SC, consistent with their essential roles in SC assembly. Our data further suggest that the two different meiotic cohesin complexes are distinctly arranged within the axes: Although cohesin complexes containing the kleisin REC-8 protrude above and below the plane defined by the SC, complexes containing COH-3 or -4 kleisins form a central core, which may physically separate sister chromatids. This organization may help to explain the role of the chromosome axes in promoting interhomolog repair of meiotic double-strand breaks by inhibiting intersister repair. PMID:28559338

Epstein-Barr virus nuclear antigen-1 is highly colocalized with interphase chromatin and its newly replicated regions in particular.

PubMed

Ito, Sayuri; Gotoh, Eisuke; Ozawa, Shigeru; Yanagi, Kazuo

2002-10-01

Epstein-Barr virus (EBV) nuclear antigen-1 (EBNA-1), which binds to both the EBV origin of replication (oriP) and metaphase chromosomes, is essential for the replication/retention and segregation/partition of oriP-containing plasmids. Here the chromosomal localization of EBNA-1 fused to green fluorescent protein (GFP-EBNA-1) is examined by confocal microscopy combined with a 'premature chromosome condensation' (PCC) procedure. Analyses show that GFP-EBNA-1 expressed in living cells that lack oriP plasmids is associated with cellular chromatin that has been condensed rapidly by the PCC procedure into identifiable forms that are unique to each phase of interphase as well as metaphase chromosomes. Studies of cellular chromosomal DNAs labelled with BrdU or Cy3-dUTP indicate that GFP-EBNA-1 colocalizes highly with the labelled, newly replicated regions of interphase chromatin in cells. These results suggest that EBNA-1 is associated not only with cellular metaphase chromosomes but also with condensing chromatin/chromosomes and probably with interphase chromatin, especially with its newly replicated regions.

STS map of genes and anonymous DNA fragments on human chromosome 18 using a panel of somatic cell hybrids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Overhauser, J.; Mewar, R.; Rojas, K.

1993-02-01

Somatic cell hybrids containing different deleted regions of chromosome 18 derived form patients with balanced translocations or terminal deletions were used to create a deletion mapping panel. Twenty-four sequence-tagged sites (STSs) for 17 genes and 7 anonymous polymorphic DNA fragments were identified. These STSs were used to map the 24 loci to 18 defined regions of chromosome 18. Both ERV1, previously mapped to 18q22-q23, and YES1, previously mapped to 18q21.3, were found to map to 18p11.21-pter. Several genes previously mapped to 18q21 were found to be in the order cen-SSAV1-DCC-FECH-GRP-BCL2-PLANH2-tel. The precise mapping of genes to chromosome 18 should helpmore » in determining whether these genes may be involved in the etiology of specific chromosomal syndromes associated with chromosome 18. The mapping of the poloymorphic loci will assist in the integration of the physical map with the recombination map of chromosome 18. 43 refs., 2 figs., 1 tab.« less

[Cytogenetic, molecular cytogenetic, clinical and genealogical study of mothers of children with autism: a search for family genetic markers of autistic disorders].

PubMed

Vorsanova, S G; Voinova, V Iu; Iurov, I Iu; Kurinnaia, O S; Demidova, I A; Iurov, Iu B

2009-01-01

Using modern cytogenetic and molecular cytogenetic techniques towards the study of human chromosomes, an analysis of chromosomal abnormalities/chromosomal variations as well as clinical and genealogical data in mothers of children with autism has been performed. It has been shown that mothers of autistic children exhibit an increased incidence of chromosomal abnormalities (mainly mosaic forms involving chromosome X) and an increased occurrence of chromosomal variations compared to controls. The analysis of genotype-phenotype correlations revealed the increase in the frequency of cognitive disturbances and spontaneous abortions in mothers of children with autism as well as the higher frequency of mental retardation, early death and reproductive problems in the pedigrees. The high frequency of congenital malformations in the pedigrees of mothers with chromosomal variations was observed as well. Taking into account the data obtained, we have concluded that cytogenetic and molecular cytogenetic studies of mothers of children with autism are obligatory for detection of possible genetic causes of autism and genetic counseling of families with children affected with autistic disorders.

Cytogenetic, molecular-cytogenetic, and clinical-genealogical studies of the mothers of children with autism: a search for familial genetic markers for autistic disorders.

PubMed

Vorsanova, S G; Voinova, V Yu; Yurov, I Yu; Kurinnaya, O S; Demidova, I A; Yurov, Yu B

2010-09-01

State-of-the-art cytogenetic and molecular-cytogenetic methods for studying human chromosomes were used to analyze chromosomal anomalies and variants in mothers of children with autistic disorders and the results were compared with clinical-genealogical data. These investigations showed that these mothers, as compared with a control group, showed increases in the frequencies of chromosomal anomalies (mainly mosaic forms involving chromosome X) and chromosomal heteromorphisms. Analysis of correlations of genotypes and phenotypes revealed increases in the frequencies of cognitive impairments and spontaneous abortions in the mothers of children with autism with chromosomal anomalies, as well as increases in the frequencies of mental retardation, death in childhood, and impairments to reproductive function in the pedigrees of these women. There was a high incidence of developmental anomalies in the pedigrees of mothers with chromosomal variants. These results lead to the conclusion that cytogenetic and molecular-cytogenetic studies of mothers and children with autism should be regarded as obligatory in terms of detecting possible genetic causes of autism and for genetic counseling of families with autistic children.

Remote sensing and environment in the study of the malaria vector Anopheles gambiae in Mali

NASA Astrophysics Data System (ADS)

Rian, Sigrid Katrine Eivindsdatter

The malaria mosquito Anopheles gambiae is the most important vector for the most devastating form of human malaria, the parasite Plasmodium falciparum. In-depth knowledge of the vector's history and environmental preferences is essential in the pursuit of new malaria mitigation strategies. Research was conducted in Mali across a range of habitats occupied by the vector, focusing on three identified chromosomal forms in the mosquito complex. The development of a 500-m landcover classification map was carried out using MODIS satellite imagery and extensive ground survey. The resulting product has the highest resolution and is the most up-to-date and most extensively ground-surveyed among land-cover maps for the study region. The new landcover classification product is a useful tool in the mapping of the varying ecological preferences of the different An. gambiae chromosomal forms. Climate and vegetation characteristics and their relationship to chromosomal forms were investigated further along a Southwest-Northeast moisture gradient in Mali. This research demonstrates particular ecological preferences of each chromosomal form, and gives a detailed examination of particular vegetation structural and climatological patterns across the study region. A key issue in current research into the population structure of An. gambiae is speciation and evolution in the complex, as an understanding of the mechanisms of change can help in the development of new mitigation strategies. A historical review of the paleoecology, archaeology, and other historical sources intended to shed light on the evolutionary history of the vector is presented. The generally held assumption that the current breed of An. gambiae emerged in the rainforest is called into question and discussed within the framework of paleoenvironment and human expansions in sub-Saharan West Africa.

A Three-Dimensional Model of the Yeast Genome

NASA Astrophysics Data System (ADS)

Noble, William; Duan, Zhi-Jun; Andronescu, Mirela; Schutz, Kevin; McIlwain, Sean; Kim, Yoo Jung; Lee, Choli; Shendure, Jay; Fields, Stanley; Blau, C. Anthony

Layered on top of information conveyed by DNA sequence and chromatin are higher order structures that encompass portions of chromosomes, entire chromosomes, and even whole genomes. Interphase chromosomes are not positioned randomly within the nucleus, but instead adopt preferred conformations. Disparate DNA elements co-localize into functionally defined aggregates or factories for transcription and DNA replication. In budding yeast, Drosophila and many other eukaryotes, chromosomes adopt a Rabl configuration, with arms extending from centromeres adjacent to the spindle pole body to telomeres that abut the nuclear envelope. Nonetheless, the topologies and spatial relationships of chromosomes remain poorly understood. Here we developed a method to globally capture intra- and inter-chromosomal interactions, and applied it to generate a map at kilobase resolution of the haploid genome of Saccharomyces cerevisiae. The map recapitulates known features of genome organization, thereby validating the method, and identifies new features. Extensive regional and higher order folding of individual chromosomes is observed. Chromosome XII exhibits a striking conformation that implicates the nucleolus as a formidable barrier to interaction between DNA sequences at either end. Inter-chromosomal contacts are anchored by centromeres and include interactions among transfer RNA genes, among origins of early DNA replication and among sites where chromosomal breakpoints occur. Finally, we constructed a three-dimensional model of the yeast genome. Our findings provide a glimpse of the interface between the form and function of a eukaryotic genome.

Detection of Turner syndrome using X-chromosome inactivation specific differentially methylated CpG sites: A pilot study.

PubMed

Zhang, Qiang; Guo, Xiaohong; Tian, Tian; Wang, Teng; Li, Qiaoli; Wang, Lei; Liu, Yun; Xing, Qinghe; He, Lin; Zhao, Xinzhi

2017-05-01

Early diagnosis of Turner syndrome (TS) may improve preventive measures and treatment. X-chromosome inactivation specific differentially methylated CpG sites (XIDMSs) that are high methylated in inactive X chromosomes (Xi) and unmethylated in active X chromosomes (Xa) may be potential makers for TS detection. The candidate XIDMSs were screened from 9 male and 12 female DNA samples with normal karyotypes using the Illumina 450k array and validated by bisulfite sequencing PCR and pyrosequencing assay. X chromosome dosage was calculated according to the methylation level of multiple XIDMSs. Overall, 108 candidate XIDMSs were screened by the 450k array. Validations indicated that XIDMSs gathered and formed the X-chromosome inactivation specific differentially methylated regions (XIDMRs). Using 3 XIDMRs at SAT1, UXT and UTP14A loci, 36 TS, 22 normal female and 6 male samples were analyzed. Methylation levels of the 20 XIDMSs in the XIDMRs could distinguish between TS and normal female DNA samples, the X chromosome dosage was consistent with karyotyping data. Analyzing samples of 2 triple X syndrome and 3 Klinefelter syndrome patients suggested that this method could be used to detect X chromosome aneuploids other than TS. XIDMSs are widely spread along the X chromosome and might be effective markers for detection of TS and other X chromosome aneuploids. Copyright © 2017 Elsevier B.V. All rights reserved.

Mutations in the caveolin-3 gene cause autosomal dominant limb-girdle muscular dystrophy.

PubMed

Minetti, C; Sotgia, F; Bruno, C; Scartezzini, P; Broda, P; Bado, M; Masetti, E; Mazzocco, M; Egeo, A; Donati, M A; Volonte, D; Galbiati, F; Cordone, G; Bricarelli, F D; Lisanti, M P; Zara, F

1998-04-01

Limb-girdle muscular dystrophy (LGMD) is a clinically and genetically heterogeneous group of myopathies, including autosomal dominant and recessive forms. To date, two autosomal dominant forms have been recognized: LGMD1A, linked to chromosome 5q, and LGMD1B, associated with cardiac defects and linked to chromosome 1q11-21. Here we describe eight patients from two different families with a new form of autosomal dominant LGMD, which we propose to call LGMD1C, associated with a severe deficiency of caveolin-3 in muscle fibres. Caveolin-3 (or M-caveolin) is the muscle-specific form of the caveolin protein family, which also includes caveolin-1 and -2. Caveolins are the principal protein components of caveolae (50-100 nm invaginations found in most cell types) which represent appendages or sub-compartments of plasma membranes. We localized the human caveolin-3 gene (CAV3) to chromosome 3p25 and identified two mutations in the gene: a missense mutation in the membrane-spanning region and a micro-deletion in the scaffolding domain. These mutations may interfere with caveolin-3 oligomerization and disrupt caveolae formation at the muscle cell plasma membrane.

The fate of W chromosomes in hybrids between wild silkmoths, Samia cynthia ssp.: no role in sex determination and reproduction

PubMed Central

Yoshido, A; Marec, F; Sahara, K

2016-01-01

Moths and butterflies (Lepidoptera) have sex chromosome systems with female heterogamety (WZ/ZZ or derived variants). The maternally inherited W chromosome is known to determine female sex in the silkworm, Bombyx mori. However, little is known about the role of W chromosome in other lepidopteran species. Here we describe two forms of the W chromosome, W and neo-W, that are transmitted to both sexes in offspring of hybrids from reciprocal crosses between subspecies of wild silkmoths, Samia cynthia. We performed crosses between S. c. pryeri (2n=28, WZ/ZZ) and S. c. walkeri (2n=26, neo-Wneo-Z/neo-Zneo-Z) and examined fitness and sex chromosome constitution in their hybrids. The F1 hybrids of both reciprocal crosses had reduced fertility. Fluorescence in situ hybridization revealed not only the expected sex chromosome constitutions in the backcross and F2 hybrids of both sexes but also females without the W (or neo-W) chromosome and males carrying the W (or neo-W) chromosome. Furthermore, crosses between the F2 hybrids revealed no association between the presence or absence of W (or neo-W) chromosome and variations in the hatchability of their eggs. Our results clearly suggest that the W (or neo-W) chromosome of S. cynthia ssp. plays no role in sex determination and reproduction, and thus does not contribute to the formation of reproductive barriers between different subspecies. PMID:26758188

The fate of W chromosomes in hybrids between wild silkmoths, Samia cynthia ssp.: no role in sex determination and reproduction.

PubMed

Yoshido, A; Marec, F; Sahara, K

2016-05-01

Moths and butterflies (Lepidoptera) have sex chromosome systems with female heterogamety (WZ/ZZ or derived variants). The maternally inherited W chromosome is known to determine female sex in the silkworm, Bombyx mori. However, little is known about the role of W chromosome in other lepidopteran species. Here we describe two forms of the W chromosome, W and neo-W, that are transmitted to both sexes in offspring of hybrids from reciprocal crosses between subspecies of wild silkmoths, Samia cynthia. We performed crosses between S. c. pryeri (2n=28, WZ/ZZ) and S. c. walkeri (2n=26, neo-Wneo-Z/neo-Zneo-Z) and examined fitness and sex chromosome constitution in their hybrids. The F1 hybrids of both reciprocal crosses had reduced fertility. Fluorescence in situ hybridization revealed not only the expected sex chromosome constitutions in the backcross and F2 hybrids of both sexes but also females without the W (or neo-W) chromosome and males carrying the W (or neo-W) chromosome. Furthermore, crosses between the F2 hybrids revealed no association between the presence or absence of W (or neo-W) chromosome and variations in the hatchability of their eggs. Our results clearly suggest that the W (or neo-W) chromosome of S. cynthia ssp. plays no role in sex determination and reproduction, and thus does not contribute to the formation of reproductive barriers between different subspecies.

Chromosome banding in Amphibia. XXVI. Coexistence of homomorphic XY sex chromosomes and a derived Y-autosome translocation in Eleutherodactylus maussi (Anura, Leptodactylidae).

PubMed

Schmid, M; Feichtinger, W; Steinlein, C; Haaf, T; Schartl, M; Visbal García, R; Manzanilla Pupo, J; Fernández Badillo, A

2002-01-01

A 15-year cytogenetic survey on one population of the leaf litter frog Eleutherodactylus maussi in northern Venezuela confirmed the existence of multiple XXAA male symbol /XAA(Y) female symbol sex chromosomes which originated by a centric (Robertsonian) fusion between the original Y chromosome and an autosome. 95% of the male individuals in this population are carriers of this Y-autosome fusion. In male meiosis the XAA(Y) sex chromosomes pair in the expected trivalent configuration. In the same population, 5% of the male animals still possess the original, free XY sex chromosomes. In a second population of E. maussi analyzed, all male specimens are characterized by these ancestral XY chromosomes which form normal bivalents in meiosis. E. maussi apparently represents the first vertebrate species discovered in which a derived Y-autosome fusion still coexists with the ancestral free XY sex chromosomes. The free XY sex chromosomes, as well as the multiple XA(Y) sex chromosomes are still in a very primitive (homomorphic) stage of differentiation. With no banding technique applied it is possible to distinguish the Y from the X. DNA flow cytometric measurements show that the genome of E. maussi is among the largest in the anuran family Leptodactylidae. The present study also supplies further data on differential chromosome banding and fluorescence in situ hybridization experiments in this amphibian species. Copyright 2003 S. Karger AG, Basel

Uneven distribution of expressed sequence tag loci on maize pachytene chromosomes

PubMed Central

Anderson, Lorinda K.; Lai, Ann; Stack, Stephen M.; Rizzon, Carene; Gaut, Brandon S.

2006-01-01

Examining the relationships among DNA sequence, meiotic recombination, and chromosome structure at a genome-wide scale has been difficult because only a few markers connect genetic linkage maps with physical maps. Here, we have positioned 1195 genetically mapped expressed sequence tag (EST) markers onto the 10 pachytene chromosomes of maize by using a newly developed resource, the RN-cM map. The RN-cM map charts the distribution of crossing over in the form of recombination nodules (RNs) along synaptonemal complexes (SCs, pachytene chromosomes) and allows genetic cM distances to be converted into physical micrometer distances on chromosomes. When this conversion is made, most of the EST markers used in the study are located distally on the chromosomes in euchromatin. ESTs are significantly clustered on chromosomes, even when only euchromatic chromosomal segments are considered. Gene density and recombination rate (as measured by EST and RN frequencies, respectively) are strongly correlated. However, crossover frequencies for telomeric intervals are much higher than was expected from their EST frequencies. For pachytene chromosomes, EST density is about fourfold higher in euchromatin compared with heterochromatin, while DNA density is 1.4 times higher in heterochromatin than in euchromatin. Based on DNA density values and the fraction of pachytene chromosome length that is euchromatic, we estimate that ∼1500 Mbp of the maize genome is in euchromatin. This overview of the organization of the maize genome will be useful in examining genome and chromosome evolution in plants. PMID:16339046

Refinement of the cone-rod retinal dystrophy locus on chromosome 19q

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gregory, C.Y.; Evans, K.; Bhattacharya, S.S.

1994-11-01

Cone-rod dystrophy (CRD) is a severe example of an inherited retinal dystrophy: ophthalmic diseases that as a group constitute the commonest causes of blindness in children in the developed world and account for a significant proportion of visual handicap in adults. Two case reports suggested loci for CRD-causing genes on chromosomes 18q and chromosome 17q. Recently, we reported the results of a total genome search that localized an autosomal dominant form of CRD to chromosome 19q in the region 19q13.1-q13.2. Since then, using data from a short tandem repeat-polymorphism linkage map of chromosome 19 and recently developed microsatellite markers inmore » this region, we have been able to further refine the localization of the chromosome 19q CRD-causing gene. Seven new microsatellite markers were used to genotype 34 affected subjects, 22 unaffected subjects, and 15 spouses. Two-point, multipoint, and FASTMAP analyses were performed. 11 refs., 1 tab.« less

Multi-scale structural community organisation of the human genome.

PubMed

Boulos, Rasha E; Tremblay, Nicolas; Arneodo, Alain; Borgnat, Pierre; Audit, Benjamin

2017-04-11

Structural interaction frequency matrices between all genome loci are now experimentally achievable thanks to high-throughput chromosome conformation capture technologies. This ensues a new methodological challenge for computational biology which consists in objectively extracting from these data the structural motifs characteristic of genome organisation. We deployed the fast multi-scale community mining algorithm based on spectral graph wavelets to characterise the networks of intra-chromosomal interactions in human cell lines. We observed that there exist structural domains of all sizes up to chromosome length and demonstrated that the set of structural communities forms a hierarchy of chromosome segments. Hence, at all scales, chromosome folding predominantly involves interactions between neighbouring sites rather than the formation of links between distant loci. Multi-scale structural decomposition of human chromosomes provides an original framework to question structural organisation and its relationship to functional regulation across the scales. By construction the proposed methodology is independent of the precise assembly of the reference genome and is thus directly applicable to genomes whose assembly is not fully determined.

Combing Chromosomal DNA Mediated by the SMC Complex: Structure and Mechanisms.

PubMed

Kamada, Katsuhiko; Barillà, Daniela

2018-02-01

Genome maintenance requires various nucleoid-associated factors in prokaryotes. Among them, the SMC (Structural Maintenance of Chromosomes) protein has been thought to play a static role in the organization and segregation of the chromosome during cell division. However, recent studies have shown that the bacterial SMC is required to align left and right arms of the emerging chromosome and that the protein dynamically travels from origin to Ter region. A rod form of the SMC complex mediates DNA bridging and has been recognized as a machinery responsible for DNA loop extrusion, like eukaryotic condensin or cohesin complexes, which act as chromosome organizers. Attention is now turning to how the prototype of the complex is loaded on the entry site and translocated on chromosomal DNA, explaining its overall conformational changes at atomic levels. Here, we review and highlight recent findings concerning the prokaryotic SMC complex and discuss possible mechanisms from the viewpoint of protein architecture. © 2017 The Authors. BioEssays Published by WILEY Periodicals, Inc.

Both Chromosome Decondensation and Condensation Are Dependent on DNA Replication in C. elegans Embryos

PubMed Central

Sonneville, Remi; Craig, Gillian; Labib, Karim; Gartner, Anton; Blow, J. Julian

2015-01-01

Summary During cell division, chromatin alternates between a condensed state to facilitate chromosome segregation and a decondensed form when DNA replicates. In most tissues, S phase and mitosis are separated by defined G1 and G2 gap phases, but early embryogenesis involves rapid oscillations between replication and mitosis. Using Caenorhabditis elegans embryos as a model system, we show that chromosome condensation and condensin II concentration on chromosomal axes require replicated DNA. In addition, we found that, during late telophase, replication initiates on condensed chromosomes and promotes the rapid decondensation of the chromatin. Upon replication initiation, the CDC-45-MCM-GINS (CMG) DNA helicase drives the release of condensin I complexes from chromatin and the activation or displacement of inactive MCM-2–7 complexes, which together with the nucleoporin MEL-28/ELYS tethers condensed chromatin to the nuclear envelope, thereby promoting chromatin decondensation. Our results show how, in an early embryo, the chromosome-condensation cycle is functionally linked with DNA replication. PMID:26166571

The Sex Chromosomes in Evolution and in Medicine

PubMed Central

Barr, Murray L.

1966-01-01

The recent emergence of human cytogenetics has a firm foundation in studies on other forms of life. Historical highlights are Mendel's studies on the garden pea (published in 1865 but lost in an obscure journal until 1900); formulation of cytogenic postulates by Sutton and Boveri (1902-1903); Bridges' discovery of chromosome abnormalities in Drosophila (1916), followed by numerous similar studies in plants; and demonstration of the chromosomal basis of the syndromes of Down, Klinefelter and Turner in man (1959). The sex chromosomes (XX and XY) evolved from a pair of undifferentiated autosomes of a premammalian ancestor, the X chromosome changing less than the Y as they evolved. Eleven numerical abnormalities of the sex chromosomes are known in man, and knowledge of their effects on development is accumulating. The abnormal complexes range in size from the XO error of Turner's syndrome to the XXXXY error of a variant of Klinefelter's syndrome. ImagesFig. 1Fig. 2Fig. 3Fig. 4Fig. 5Fig. 6Fig. 7Fig. 8 PMID:4224254

Neoplastic transformation of SV40-immortalized human urinary tract epithelial cells by in vitro exposure to 3-methylcholanthrene.

PubMed

Reznikoff, C A; Loretz, L J; Christian, B J; Wu, S Q; Meisner, L F

1988-08-01

Normal human urinary tract epithelial cells (HUC) were neoplastically transformed in vitro using a step-wise strategy. First, a partially transformed non-virus-producing cell line was obtained after infection of HUC with simian virus 40 (SV40). This cell line (SV-HUC-1) was demonstrated to be clonal in origin, as 100% of cells contained at least five of seven marker chromosomes. Marker chromosomes were formed by balanced translocations resulting in a 'pseudodiploid' cell line. SV-HUC-1 showed altered growth properties in vitro (e.g. anchorage independent growth) but failed to form tumors in athymic nude mice, even after 3 years in culture (80 passages). In the studies reported here, SV-HUC-1 at early passages (P15-P19) were exposed to 3-methylcholanthrene (MCA) in three separate experiments. After a six-week post-treatment period of cell culture, cells were inoculated s.c. into athymic nude mice. In all experiments, MCA-treated SV-HUC-1 formed carcinomas in mice usually with a latent period of 5-8 weeks. These carcinomas showed heterogeneity with respect to histopathologies and growth properties in the mice and karyotypes. All the tumors retained SV-HUC-1 chromosome markers, but each independent transformant was aneuploid and contained unique new marker chromosomes. Chromosomes usually altered in tumor cells included numbers 3, 5, 6, 9, 11 and 13. Mutations in the ras family of cellular proto-oncogenes resulting in altered mobility of the p21 protein product were not detected in six cell lines established from independently derived tumors. It is not yet known whether other cellular proto-oncogenes are activated in these tumorigenic transformants. Neither control SV-HUC-1 (which were not exposed to MCA), nor early passage HUC exposed to MCA formed tumors when inoculated into mice. Thus, the tumorigenic transformation of HUC resulted from the combined actions of SV40 and MCA.

The molecular karyotype of the megabase chromosomes of Trypanosoma brucei stock 427.

PubMed

Melville, S E; Leech, V; Navarro, M; Cross, G A

2000-12-01

We present the molecular karyotype of the megabase chromosomes of Trypanosoma brucei stock 427, clone 221a. This cloned stock is most commonly used in research laboratories in genetic manipulation experiments and in studies of antigenic variation. Using 116 previously characterised chromosome-specific markers, we identify 11 diploid pairs of megabase chromosomes and detect no loss of synteny in EST and gene marker distribution between this stock and the genome project reference stock TREU 927/4. Nevertheless, the chromosomes of 427 are all larger than their homologues in 927, except chromosomes IIa and IXa. The greatest size variation is seen in chromosome I, the smallest of which is 1.1 Mb (927-Ia) and the largest 3.6 Mb (427-Ib). The total nuclear DNA content of both stocks has been estimated by comparison of the mobility of T. brucei and yeast chromosomes. Trypanosomes of stock 427 contain approximately 16.5 Mb more megabase chromosomal DNA than those of stock 927. We have detected the presence of bloodstream-form expression-site-associated sequences on eight or more megabase chromosomes. These sequences are not found on the same chromosomes in each stock. We have determined the chromosomal band location of nine characterised variant surface glycoprotein genes, including the currently expressed VSG 221. Our results demonstrate both the stability of the T. brucei genome, as illustrated by the conservation of syntenic groups of genes in the two stocks, and the polymorphic nature of the genomic regions involved in antigenic variation. We propose that the chromosomes of stock 427 be numbered to correspond to their homologues in the genome project reference stock TREU 927/4.

Role of DNA secondary structures in fragile site breakage along human chromosome 10

PubMed Central

Dillon, Laura W.; Pierce, Levi C. T.; Ng, Maggie C. Y.; Wang, Yuh-Hwa

2013-01-01

The formation of alternative DNA secondary structures can result in DNA breakage leading to cancer and other diseases. Chromosomal fragile sites, which are regions of the genome that exhibit chromosomal breakage under conditions of mild replication stress, are predicted to form stable DNA secondary structures. DNA breakage at fragile sites is associated with regions that are deleted, amplified or rearranged in cancer. Despite the correlation, unbiased examination of the ability to form secondary structures has not been evaluated in fragile sites. Here, using the Mfold program, we predict potential DNA secondary structure formation on the human chromosome 10 sequence, and utilize this analysis to compare fragile and non-fragile DNA. We found that aphidicolin (APH)-induced common fragile sites contain more sequence segments with potential high secondary structure-forming ability, and these segments clustered more densely than those in non-fragile DNA. Additionally, using a threshold of secondary structure-forming ability, we refined legitimate fragile sites within the cytogenetically defined boundaries, and identified potential fragile regions within non-fragile DNA. In vitro detection of alternative DNA structure formation and a DNA breakage cell assay were used to validate the computational predictions. Many of the regions identified by our analysis coincide with genes mutated in various diseases and regions of copy number alteration in cancer. This study supports the role of DNA secondary structures in common fragile site instability, provides a systematic method for their identification and suggests a mechanism by which DNA secondary structures can lead to human disease. PMID:23297364

Regulators of spindle microtubules and their mechanisms: Living together matters.

PubMed

Lakshmi, R Bhagya; Nair, Vishnu M; Manna, Tapas K

2018-02-01

Development and survival of all eukaryotic organisms depend on equal partitioning of their chromosomes between the two newly formed daughter cells during mitosis. The mitotic spindle performs the task of physically segregating the chromosomes through multiple stages of mitosis. During this process, kinetochore-microtubule attachment requires to be selectively stabilized to hold the chromosomes, but at the same time, it has to be flexible enough to allow kinetochore microtubule dynamicity and chromosome movements. Research during the last decade or so has identified a number of proteins associated with the spindle microtubule plus ends that regulate these processes and orchestrate forces to spatially organize and separate the chromosomes. In this review, we describe the molecular details of those regulators and their mechanisms of action at the kinetochore-microtubule interface. © 2018 IUBMB Life, 70(2):101-111, 2018. © 2018 International Union of Biochemistry and Molecular Biology.

Construction of BAC Libraries from Flow-Sorted Chromosomes.

PubMed

Šafář, Jan; Šimková, Hana; Doležel, Jaroslav

2016-01-01

Cloned DNA libraries in bacterial artificial chromosome (BAC) are the most widely used form of large-insert DNA libraries. BAC libraries are typically represented by ordered clones derived from genomic DNA of a particular organism. In the case of large eukaryotic genomes, whole-genome libraries consist of a hundred thousand to a million clones, which make their handling and screening a daunting task. The labor and cost of working with whole-genome libraries can be greatly reduced by constructing a library derived from a smaller part of the genome. Here we describe construction of BAC libraries from mitotic chromosomes purified by flow cytometric sorting. Chromosome-specific BAC libraries facilitate positional gene cloning, physical mapping, and sequencing in complex plant genomes.

[Research progress in lampbrush chromosomes and some suggestions for their use in genetics teaching].

PubMed

Chen, Fan-guo; Li, Qing-qing

2016-02-01

Lampbrush chromosomes (LBCs) are transient giant transcripts that exist at the diplotene stage of the first meiotic division in female gametocytes of almost all animals except mammals. LBCs are named for their lampbrush-like structure, however, they received the lowest research attention in studies of three classical cytogenetic chromosomes. They have been excellent models for studying the structure, organization, transcription, and transcriptional processing of chromosomes during meiosis. Here we briefly summarized these studies and LBCs forming mechanism and also discussed their possible functions, such as providing enough transcriptional products for embryonic development by oocytes LBCs or polyploidy demonstrated by previous reports. Finally, we discussed the possibility of introducing this typical case into our genetics teaching to inspire students' interest in genetics.

A locus for the nystagmus-associated form of episodic ataxia maps to an 11-cM region on chromosome 19p

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kramer, P.L.; Gancher, S.T.; Nutt, J.G.

1995-07-01

Episodic ataxia (EA) is a rare neurological disorder characterized by attacks of generalized ataxia and near-normal neurological function between attacks. Most inherited cases are the result of an autosomal dominant condition with unknown neuropathology. It is heterogeneous and includes at least two distinct forms. In EA-1, attacks last minutes and interictal myokymia may be present. In EA-2, attacks may last hours and interictal nystagmus may occur. We reported linkage in four EA-1 families to chromosome 12p13 and identified mutations in these families in a potassium channel gene, KCNA1. Recently, we reported linkage in two EA-2 families to a 30-cM regionmore » on chromosome 19p. This report is based on members of the same two families and one additional kindred. 18 refs., 1 fig., 1 tab.« less

A novel locus for dilated cardiomyopathy maps to canine chromosome 8.

PubMed

Werner, Petra; Raducha, Michael G; Prociuk, Ulana; Sleeper, Meg M; Van Winkle, Thomas J; Henthorn, Paula S

2008-06-01

Dilated cardiomyopathy (DCM), the most common form of cardiomyopathy, often leads to heart failure and sudden death. While a substantial proportion of DCMs are inherited, mutations responsible for the majority of DCMs remain unidentified. A genome-wide linkage study was performed to identify the locus responsible for an autosomal recessive inherited form of juvenile DCM (JDCM) in Portuguese water dogs using 16 families segregating the disease. Results link the JDCM locus to canine chromosome 8 with two-point and multipoint lod scores of 10.8 and 14, respectively. The locus maps to a 3.9-Mb region, with complete syntenic homology to human chromosome 14, that contains no genes or loci known to be involved in the development of any type of cardiomyopathy. This discovery of a DCM locus with a previously unknown etiology will provide a new gene to examine in human DCM patients and a model for testing therapeutic approaches for heart failure.

Karyological features of wild and cultivated forms of myrtle (Myrtus communis, Myrtaceae).

PubMed

Serçe, S; Ekbiç, E; Suda, J; Gündüz, K; Kiyga, Y

2010-03-09

Myrtle is an evergreen shrub or small tree widespread throughout the Mediterranean region. In Turkey, both cultivated and wild forms, differing in plant and fruit size and fruit composition, can be found. These differences may have resulted from the domestication of the cultivated form over a long period of time. We investigated whether wild and cultivated forms of myrtle differ in karyological features (i.e., number of somatic chromosomes and relative genome size). We sampled two wild forms and six cultivated types of myrtle. All the samples had the same chromosome number (2n = 2x = 22). The results were confirmed by 4',6-diamidino-2-phenylindole (DAPI) flow cytometry. Only negligible variation (approximately 3%) in relative fluorescence intensity was observed among the different myrtle accessions, with wild genotypes having the smallest values. We concluded that despite considerable morphological differentiation, cultivated and wild myrtle genotypes in Turkey have similar karyological features.

A family of long intergenic non-coding RNA genes in human chromosomal region 22q11.2 carry a DNA translocation breakpoint/AT-rich sequence

PubMed Central

2018-01-01

FAM230C, a long intergenic non-coding RNA (lincRNA) gene in human chromosome 13 (chr13) is a member of lincRNA genes termed family with sequence similarity 230. An analysis using bioinformatics search tools and alignment programs was undertaken to determine properties of FAM230C and its related genes. Results reveal that the DNA translocation element, the Translocation Breakpoint Type A (TBTA) sequence, which consists of satellite DNA, Alu elements, and AT-rich sequences is embedded in the FAM230C gene. Eight lincRNA genes related to FAM230C also carry the TBTA sequences. These genes were formed from a large segment of the 3’ half of the FAM230C sequence duplicated in chr22, and are specifically in regions of low copy repeats (LCR22)s, in or close to the 22q.11.2 region. 22q11.2 is a chromosomal segment that undergoes a high rate of DNA translocation and is prone to genetic deletions. FAM230C-related genes present in other chromosomes do not carry the TBTA motif and were formed from the 5’ half region of the FAM230C sequence. These findings identify a high specificity in lincRNA gene formation by gene sequence duplication in different chromosomes. PMID:29668722

Condensin-driven remodelling of X chromosome topology during dosage compensation

NASA Astrophysics Data System (ADS)

Crane, Emily; Bian, Qian; McCord, Rachel Patton; Lajoie, Bryan R.; Wheeler, Bayly S.; Ralston, Edward J.; Uzawa, Satoru; Dekker, Job; Meyer, Barbara J.

2015-07-01

The three-dimensional organization of a genome plays a critical role in regulating gene expression, yet little is known about the machinery and mechanisms that determine higher-order chromosome structure. Here we perform genome-wide chromosome conformation capture analysis, fluorescent in situ hybridization (FISH), and RNA-seq to obtain comprehensive three-dimensional (3D) maps of the Caenorhabditis elegans genome and to dissect X chromosome dosage compensation, which balances gene expression between XX hermaphrodites and XO males. The dosage compensation complex (DCC), a condensin complex, binds to both hermaphrodite X chromosomes via sequence-specific recruitment elements on X (rex sites) to reduce chromosome-wide gene expression by half. Most DCC condensin subunits also act in other condensin complexes to control the compaction and resolution of all mitotic and meiotic chromosomes. By comparing chromosome structure in wild-type and DCC-defective embryos, we show that the DCC remodels hermaphrodite X chromosomes into a sex-specific spatial conformation distinct from autosomes. Dosage-compensated X chromosomes consist of self-interacting domains (~1 Mb) resembling mammalian topologically associating domains (TADs). TADs on X chromosomes have stronger boundaries and more regular spacing than on autosomes. Many TAD boundaries on X chromosomes coincide with the highest-affinity rex sites and become diminished or lost in DCC-defective mutants, thereby converting the topology of X to a conformation resembling autosomes. rex sites engage in DCC-dependent long-range interactions, with the most frequent interactions occurring between rex sites at DCC-dependent TAD boundaries. These results imply that the DCC reshapes the topology of X chromosomes by forming new TAD boundaries and reinforcing weak boundaries through interactions between its highest-affinity binding sites. As this model predicts, deletion of an endogenous rex site at a DCC-dependent TAD boundary using CRISPR/Cas9 greatly diminished the boundary. Thus, the DCC imposes a distinct higher-order structure onto X chromosomes while regulating gene expression chromosome-wide.

Molecular cytogenetic analysis of monoecious hemp (Cannabis sativa L.) cultivars reveals its karyotype variations and sex chromosomes constitution.

PubMed

Razumova, Olga V; Alexandrov, Oleg S; Divashuk, Mikhail G; Sukhorada, Tatiana I; Karlov, Gennady I

2016-05-01

Hemp (Cannabis sativa L., 2n = 20) is a dioecious plant. Sex expression is controlled by an X-to-autosome balance system consisting of the heteromorphic sex chromosomes XY for males and XX for females. Genetically monoecious hemp offers several agronomic advantages compared to the dioecious cultivars that are widely used in hemp cultivation. The male or female origin of monoecious maternal plants is unknown. Additionally, the sex chromosome composition of monoecious hemp forms remains unknown. In this study, we examine the sex chromosome makeup in monoecious hemp using a cytogenetic approach. Eight monoecious and two dioecious cultivars were used. The DNA of 210 monoecious plants was used for PCR analysis with the male-associated markers MADC2 and SCAR323. All monoecious plants showed female amplification patterns. Fluorescence in situ hybridization (FISH) with the subtelomeric CS-1 probe to chromosomes plates and karyotyping revealed a lack of Y chromosome and presence of XX sex chromosomes in monoecious cultivars with the chromosome number 2n = 20. There was a high level of intra- and intercultivar karyotype variation detected. The results of this study can be used for further analysis of the genetic basis of sex expression in plants.

Satellite DNA and Transposable Elements in Seabuckthorn (Hippophae rhamnoides), a Dioecious Plant with Small Y and Large X Chromosomes

PubMed Central

Puterova, Janka; Razumova, Olga; Martinek, Tomas; Alexandrov, Oleg; Divashuk, Mikhail; Kubat, Zdenek; Hobza, Roman; Karlov, Gennady

2017-01-01

Seabuckthorn (Hippophae rhamnoides) is a dioecious shrub commonly used in the pharmaceutical, cosmetic, and environmental industry as a source of oil, minerals and vitamins. In this study, we analyzed the transposable elements and satellites in its genome. We carried out Illumina DNA sequencing and reconstructed the main repetitive DNA sequences. For data analysis, we developed a new bioinformatics approach for advanced satellite DNA analysis and showed that about 25% of the genome consists of satellite DNA and about 24% is formed of transposable elements, dominated by Ty3/Gypsy and Ty1/Copia LTR retrotransposons. FISH mapping revealed X chromosome-accumulated, Y chromosome-specific or both sex chromosomes-accumulated satellites but most satellites were found on autosomes. Transposable elements were located mostly in the subtelomeres of all chromosomes. The 5S rDNA and 45S rDNA were localized on one autosomal locus each. Although we demonstrated the small size of the Y chromosome of the seabuckthorn and accumulated satellite DNA there, we were unable to estimate the age and extent of the Y chromosome degeneration. Analysis of dioecious relatives such as Shepherdia would shed more light on the evolution of these sex chromosomes. PMID:28057732

Chromosomal phylogeny of Robertsonian races of the house mouse on the island of Madeira: testing between alternative mutational processes.

PubMed

Britton-Davidian, Janice; Catalan, Josette; da Graça Ramalhinho, Maria; Auffray, Jean-Christophe; Claudia Nunes, Ana; Gazave, Elodie; Searle, Jeremy B; da Luz Mathias, Maria

2005-12-01

The ancestral karyotype of the house mouse (Mus musculus) consists of 40 acrocentric chromosomes, but numerous races exist within the domesticus subspecies characterized by different metacentric chromosomes formed by the joining at the centromere of two acrocentrics. An exemplary case is present on the island of Madeira where six highly divergent chromosomal races have accumulated different combinations of 20 metacentrics in 500-1000 years. Chromosomal cladistic phylogenies were performed to test the relative performance of Robertsonian (Rb) fusions, Rb fissions and whole-arm reciprocal translocations (WARTs) in resolving relationships between the chromosomal races. The different trees yielded roughly similar topologies, but varied in the number of steps and branch support. The analyses using Rb fusions/fissions as characters resulted in poorly supported trees requiring six to eight homoplasious events. Allowance for WARTs considerably increased nodal support and yielded the most parsimonious trees since homoplasy was reduced to a single event. The WART-based trees required five to nine WARTs and 12 to 16 Rb fusions. These analyses provide support for the role of WARTs in generating the extensive chromosomal diversification observed in house mice. The repeated occurrence of Rb fusions and WARTs highlights the contribution of centromere-related rearrangements to accelerated rates of chromosomal change in the house mouse.

De novo formed satellite DNA-based mammalian artificial chromosomes and their possible applications.

PubMed

Katona, Robert L

2015-02-01

Mammalian artificial chromosomes (MACs) are non-integrating, autonomously replicating natural chromosome-based vectors that may carry a vast amount of genetic material, which in turn enable potentially prolonged, safe, and regulated therapeutic transgene expression and render MACs as attractive genetic vectors for "gene replacement" or for controlling differentiation pathways in target cells. Satellite-DNA-based artificial chromosomes (SATACs) can be made by induced de novo chromosome formation in cells of different mammalian and plant species. These artificially generated accessory chromosomes are composed of predictable DNA sequences, and they contain defined genetic information. SATACs have already passed a number of obstacles crucial to their further development as gene therapy vectors, including large-scale purification, transfer of purified artificial chromosomes into different cells and embryos, generation of transgenic animals and germline transmission with purified SATACs, and the tissue-specific expression of a therapeutic gene from an artificial chromosome in the milk of transgenic animals. SATACs could be used in cell therapy protocols. For these methods, the most versatile target cell would be one that was pluripotent and self-renewing to address multiple disease target cell types, thus making multilineage stem cells, such as adult derived early progenitor cells and embryonic stem cells, as attractive universal host cells.

ParABS Systems of the Four Replicons of Burkholderia cenocepacia: New Chromosome Centromeres Confer Partition Specificity†

PubMed Central

Dubarry, Nelly; Pasta, Franck; Lane, David

2006-01-01

Most bacterial chromosomes carry an analogue of the parABS systems that govern plasmid partition, but their role in chromosome partition is ambiguous. parABS systems might be particularly important for orderly segregation of multipartite genomes, where their role may thus be easier to evaluate. We have characterized parABS systems in Burkholderia cenocepacia, whose genome comprises three chromosomes and one low-copy-number plasmid. A single parAB locus and a set of ParB-binding (parS) centromere sites are located near the origin of each replicon. ParA and ParB of the longest chromosome are phylogenetically similar to analogues in other multichromosome and monochromosome bacteria but are distinct from those of smaller chromosomes. The latter form subgroups that correspond to the taxa of their hosts, indicating evolution from plasmids. The parS sites on the smaller chromosomes and the plasmid are similar to the “universal” parS of the main chromosome but with a sequence specific to their replicon. In an Escherichia coli plasmid stabilization test, each parAB exhibits partition activity only with the parS of its own replicon. Hence, parABS function is based on the independent partition of individual chromosomes rather than on a single communal system or network of interacting systems. Stabilization by the smaller chromosome and plasmid systems was enhanced by mutation of parS sites and a promoter internal to their parAB operons, suggesting autoregulatory mechanisms. The small chromosome ParBs were found to silence transcription, a property relevant to autoregulation. PMID:16452432

Meiosis-Specific Cohesin Component, Stag3 Is Essential for Maintaining Centromere Chromatid Cohesion, and Required for DNA Repair and Synapsis between Homologous Chromosomes

PubMed Central

Hopkins, Jessica; Bedigian, Rick; Oka, Kazuhiro; Overbeek, Paul; Murray, Steve; Jordan, Philip W.

2014-01-01

Cohesins are important for chromosome structure and chromosome segregation during mitosis and meiosis. Cohesins are composed of two structural maintenance of chromosomes (SMC1-SMC3) proteins that form a V-shaped heterodimer structure, which is bridged by a α-kleisin protein and a stromal antigen (STAG) protein. Previous studies in mouse have shown that there is one SMC1 protein (SMC1β), two α-kleisins (RAD21L and REC8) and one STAG protein (STAG3) that are meiosis-specific. During meiosis, homologous chromosomes must recombine with one another in the context of a tripartite structure known as the synaptonemal complex (SC). From interaction studies, it has been shown that there are at least four meiosis-specific forms of cohesin, which together with the mitotic cohesin complex, are lateral components of the SC. STAG3 is the only meiosis-specific subunit that is represented within all four meiosis-specific cohesin complexes. In Stag3 mutant germ cells, the protein level of other meiosis-specific cohesin subunits (SMC1β, RAD21L and REC8) is reduced, and their localization to chromosome axes is disrupted. In contrast, the mitotic cohesin complex remains intact and localizes robustly to the meiotic chromosome axes. The instability of meiosis-specific cohesins observed in Stag3 mutants results in aberrant DNA repair processes, and disruption of synapsis between homologous chromosomes. Furthermore, mutation of Stag3 results in perturbation of pericentromeric heterochromatin clustering, and disruption of centromere cohesion between sister chromatids during meiotic prophase. These defects result in early prophase I arrest and apoptosis in both male and female germ cells. The meiotic defects observed in Stag3 mutants are more severe when compared to single mutants for Smc1β, Rec8 and Rad21l, however they are not as severe as the Rec8, Rad21l double mutants. Taken together, our study demonstrates that STAG3 is required for the stability of all meiosis-specific cohesin complexes. Furthermore, our data suggests that STAG3 is required for structural changes of chromosomes that mediate chromosome pairing and synapsis, DNA repair and progression of meiosis. PMID:24992337

Meiosis-specific cohesin component, Stag3 is essential for maintaining centromere chromatid cohesion, and required for DNA repair and synapsis between homologous chromosomes.

PubMed

Hopkins, Jessica; Hwang, Grace; Jacob, Justin; Sapp, Nicklas; Bedigian, Rick; Oka, Kazuhiro; Overbeek, Paul; Murray, Steve; Jordan, Philip W

2014-07-01

Cohesins are important for chromosome structure and chromosome segregation during mitosis and meiosis. Cohesins are composed of two structural maintenance of chromosomes (SMC1-SMC3) proteins that form a V-shaped heterodimer structure, which is bridged by a α-kleisin protein and a stromal antigen (STAG) protein. Previous studies in mouse have shown that there is one SMC1 protein (SMC1β), two α-kleisins (RAD21L and REC8) and one STAG protein (STAG3) that are meiosis-specific. During meiosis, homologous chromosomes must recombine with one another in the context of a tripartite structure known as the synaptonemal complex (SC). From interaction studies, it has been shown that there are at least four meiosis-specific forms of cohesin, which together with the mitotic cohesin complex, are lateral components of the SC. STAG3 is the only meiosis-specific subunit that is represented within all four meiosis-specific cohesin complexes. In Stag3 mutant germ cells, the protein level of other meiosis-specific cohesin subunits (SMC1β, RAD21L and REC8) is reduced, and their localization to chromosome axes is disrupted. In contrast, the mitotic cohesin complex remains intact and localizes robustly to the meiotic chromosome axes. The instability of meiosis-specific cohesins observed in Stag3 mutants results in aberrant DNA repair processes, and disruption of synapsis between homologous chromosomes. Furthermore, mutation of Stag3 results in perturbation of pericentromeric heterochromatin clustering, and disruption of centromere cohesion between sister chromatids during meiotic prophase. These defects result in early prophase I arrest and apoptosis in both male and female germ cells. The meiotic defects observed in Stag3 mutants are more severe when compared to single mutants for Smc1β, Rec8 and Rad21l, however they are not as severe as the Rec8, Rad21l double mutants. Taken together, our study demonstrates that STAG3 is required for the stability of all meiosis-specific cohesin complexes. Furthermore, our data suggests that STAG3 is required for structural changes of chromosomes that mediate chromosome pairing and synapsis, DNA repair and progression of meiosis.

The genomics of plant sex chromosomes.

PubMed

Vyskot, Boris; Hobza, Roman

2015-07-01

Around six percent of flowering species are dioecious, with separate female and male individuals. Sex determination is mostly based on genetics, but morphologically distinct sex chromosomes have only evolved in a few species. Of these, heteromorphic sex chromosomes have been most clearly described in the two model species - Silene latifolia and Rumex acetosa. In both species, the sex chromosomes are the largest chromosomes in the genome. They are hence easily distinguished, can be physically separated and analyzed. This review discusses some recent experimental data on selected model dioecious species, with a focus on S. latifolia. Phylogenetic analyses show that dioecy in plants originated independently and repeatedly even within individual genera. A cogent question is whether there is genetic degeneration of the non-recombining part of the plant Y chromosome, as in mammals, and, if so, whether reduced levels of gene expression in the heterogametic sex are equalized by dosage compensation. Current data provide no clear conclusion. We speculate that although some transcriptome analyses indicate the first signs of degeneration, especially in S. latifolia, the evolutionary processes forming plant sex chromosomes in plants may, to some extent, differ from those in animals. Copyright © 2015. Published by Elsevier Ireland Ltd.

Computational model of chromosome aberration yield induced by high- and low-LET radiation exposures.

PubMed

Ponomarev, Artem L; George, Kerry; Cucinotta, Francis A

2012-06-01

We present a computational model for calculating the yield of radiation-induced chromosomal aberrations in human cells based on a stochastic Monte Carlo approach and calibrated using the relative frequencies and distributions of chromosomal aberrations reported in the literature. A previously developed DNA-fragmentation model for high- and low-LET radiation called the NASARadiationTrackImage model was enhanced to simulate a stochastic process of the formation of chromosomal aberrations from DNA fragments. The current version of the model gives predictions of the yields and sizes of translocations, dicentrics, rings, and more complex-type aberrations formed in the G(0)/G(1) cell cycle phase during the first cell division after irradiation. As the model can predict smaller-sized deletions and rings (<3 Mbp) that are below the resolution limits of current cytogenetic analysis techniques, we present predictions of hypothesized small deletions that may be produced as a byproduct of properly repaired DNA double-strand breaks (DSB) by nonhomologous end-joining. Additionally, the model was used to scale chromosomal exchanges in two or three chromosomes that were obtained from whole-chromosome FISH painting analysis techniques to whole-genome equivalent values.

Rickettsia Species in African Anopheles Mosquitoes

PubMed Central

Socolovschi, Cristina; Pages, Frédéric; Ndiath, Mamadou O.; Ratmanov, Pavel; Raoult, Didier

2012-01-01

Background There is higher rate of R. felis infection among febrile patients than in healthy people in Sub-Saharan Africa, predominantly in the rainy season. Mosquitoes possess a high vectorial capacity and, because of their abundance and aggressiveness, likely play a role in rickettsial epidemiology. Methodology/Principal Findings Quantitative and traditional PCR assays specific for Rickettsia genes detected rickettsial DNA in 13 of 848 (1.5%) Anopheles mosquitoes collected from Côte d’Ivoire, Gabon, and Senegal. R. felis was detected in one An. gambiae molecular form S mosquito collected from Kahin, Côte d’Ivoire (1/77, 1.3%). Additionally, a new Rickettsia genotype was detected in five An. gambiae molecular form S mosquitoes collected from Côte d’Ivoire (5/77, 6.5%) and one mosquito from Libreville, Gabon (1/88, 1.1%), as well as six An. melas (6/67, 9%) mosquitoes collected from Port Gentil, Gabon. A sequence analysis of the gltA, ompB, ompA and sca4 genes indicated that this new Rickettsia sp. is closely related to R. felis. No rickettsial DNA was detected from An. funestus, An. arabiensis, or An. gambiae molecular form M mosquitoes. Additionally, a BLAST analysis of the gltA sequence from the new Rickettsia sp. resulted in a 99.71% sequence similarity to a species (JQ674485) previously detected in a blood sample of a Senegalese patient with a fever from the Bandafassi village, Kedougou region. Conclusion R. felis was detected for the first time in An. gambiae molecular form S, which represents the major African malaria vector. The discovery of R. felis, as well as a new Rickettsia species, in mosquitoes raises new issues with respect to African rickettsial epidemiology that need to be investigated, such as bacterial isolation, the degree of the vectorial capacity of mosquitoes, the animal reservoirs, and human pathogenicity. PMID:23118963

Probabilities of radiation-induced inter- and intrachromosomal exchanges and their dependence on the DNA content of the chromosome

NASA Technical Reports Server (NTRS)

Wu, H.; Yang, T. C. (Principal Investigator)

2001-01-01

A biophysical model has been developed that is based on the assumptions that an interphase chromosome occupies a spherical territory and that chromosome exchanges are formed by the misrejoining of two DNA double-strand breaks induced within a defined interaction distance. The model is used to explain the relative frequencies of inter- and intrachromosomal exchanges and the relationship between radiation-induced aberrations in individual chromosomes and the DNA content of the chromosome. Although this simple model predicts a higher ratio of inter- to intrachromosomal exchanges for low-LET radiation than for high-LET radiation, as has been suggested by others, we argue that the comparison of the prediction of the model with experimental results is not straightforward. With the model, we also show that the probability of the formation of interchromosomal exchanges is proportional to the "surface area" of the chromosome domain plus a correction term. The correction term is small if the interaction distance is less than 1 microm for both low- and high-LET radiations.

Karyotype and sex chromosome differentiation in two Nalassus species (Coleoptera, Tenebrionidae)

PubMed Central

Şendoğan, Dirim; Alpagut-Keskin, Nurşen

2016-01-01

Abstract Cytogenetic features of Nalassus bozdagus Nabozhenko & Keskin, 2010 and Nalassus plebejus Küster, 1850 were analysed using conventional and differential staining. Mitotic and meiotic chromosomal analysis revealed the diploid number as 2n = 20 (9+Xyp) in both species. Besides the general resemblance of two Nalassus Mulsant, 1854 karyotypes, important differences related to variations in the number of metacentric/submetacentric chromosomes, localization of highly impregnated regions which are considered as NOR and heterochromatin distribution are clearly observed. The most prominent difference between two species is found related to the X chromosome which is clearly larger in Nalassus bozdagus and has a conspicuous secondary constriction on the long arm. As a result of silver staining, the existence of highly impregnated areas associated with Xyp of Nalassus bozdagus in both prophase I and metaphase I, suggests that NORs are seemingly located on sex chromosomes. On the other hand, the potential NORs of Nalassus plebejus were observed only in prophase I nuclei. With the application of fluorescence dye DAPI, the AT rich chromosome regions and Xyp which forms the parachute configuration were shown in both species. PMID:27830047

Formaldehyde-induced acentric chromosome fragments and chromosome stickiness in Chortophaga neuroblasts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dowd, M.A.; Gaulden, M.E.; Proctor, B.L.

1986-01-01

Embryos of the grasshopper Chortophaga viridifasciata were exposed in vitro to formaldehyde (FA), as formalin, at concentrations ranging from 10/sup -8/ M (0.0003 ppm) to 10/sup -3/ M (30 ppm) at 38/sup 0/C. A low frequency of distinct acentric chromosome fragments was observed in the neuroblasts after 1 hr exposure to 7.5 x 10/sup -4/ or 10/sup -3/ M FA plus 3 hr recovery, but not at lower concentrations, even with 4 hr exposure. Neuroblasts with sticky chromosomes were observed at 10/sup -4/, 7.5 x 10/sup -4/, and 10/sup -3/ M FA, the percent of cells with slight, moderate, ormore » severe stickiness varying with FA concentrations. Fragments were associated with the sticky chromosomes. It is concluded that the distinct acentric fragments induced by FA result from breakage at a single sticky point (slight stickiness) between separating sister chromatids. The chromosome effects observed probably result from the action of daughter products that are formed by the interaction of FA with culture medium components, especially the fetal calf serum.« less

The P450 CYP6Z1 confers carbamate/pyrethroid cross-resistance in a major African malaria vector beside a novel carbamate-insensitive N485I acetylcholinesterase-1 mutation.

PubMed

Ibrahim, Sulaiman S; Ndula, Miranda; Riveron, Jacob M; Irving, Helen; Wondji, Charles S

2016-07-01

Carbamates are increasingly used for vector control notably in areas with pyrethroid resistance. However, a cross-resistance between these insecticides in major malaria vectors such as Anopheles funestus could severely limit available resistance management options. Unfortunately, the molecular basis of such cross-resistance remains uncharacterized in An. funestus, preventing effective resistance management. Here, using a genomewide transcription profiling, we revealed that metabolic resistance through upregulation of cytochrome P450 genes is driving carbamate resistance. The P450s CYP6P9a, CYP6P9b and CYP6Z1 were the most upregulated detoxification genes in the multiple resistant mosquitoes. However, in silico docking simulations predicted CYP6Z1 to metabolize both pyrethroids and carbamates, whereas CYP6P9a and CYP6P9b were predicted to metabolize only the pyrethroids. Using recombinant enzyme metabolism and inhibition assays, we demonstrated that CYP6Z1 metabolizes bendiocarb and pyrethroids, whereas CYP6P9a and CYP6P9b metabolize only the pyrethroids. Other upregulated gene families in resistant mosquitoes included several cuticular protein genes suggesting a possible reduced penetration resistance mechanism. Investigation of the target-site resistance in acetylcholinesterase 1 (ace-1) gene detected and established the association between the new N485I mutation and bendiocarb resistance (odds ratio 7.3; P < 0.0001). The detection of multiple haplotypes in single mosquitoes after cloning suggested the duplication of ace-1. A TaqMan genotyping of the N485I in nine countries revealed that the mutation is located only in southern Africa with frequency of 10-15% suggesting its recent occurrence. These findings will help in monitoring the spread and evolution of carbamate resistance and improve the design of effective resistance management strategies to control this malaria vector. © 2016 The Authors. Molecular Ecology Published by John Wiley & Sons Ltd.

Is housing quality associated with malaria incidence among young children and mosquito vector numbers? Evidence from Korogwe, Tanzania.

PubMed

Liu, Jenny X; Bousema, Teun; Zelman, Brittany; Gesase, Samwel; Hashim, Ramadhan; Maxwell, Caroline; Chandramohan, Daniel; Gosling, Roly

2014-01-01

Several studies conducted in Northeast Tanzania have documented declines in malaria transmission even before interventions were scaled up. One explanation for these reductions may be the changes in socio-environmental conditions associated with economic development, and in particular improvements in housing construction. This analysis seeks to identify (1) risk factors for malaria incidence among young children and (2) household and environmental factors associated with mosquito vector numbers collected in the child's sleeping area. Both analyses focus on housing construction quality as a key determinant. For 435 children enrolled in a larger trial of intermittent preventive treatment for malaria in infants in the Korogwe District in Tanga, Northeastern Tanzania, detailed information on their dwelling characteristics were collected in the last year of the trial. Principal components analysis was used to construct an index of housing structure quality and converted to quintile units for regression analysis. Univariate and multivariate random effects negative binomial regressions were used to predict risk factors for child malaria incidence and the mean total number of indoor female Anopheles gambiae and funestus mosquitoes collected per household across three occasions. Building materials have substantially improved in Korogwe over time. Multivariate regressions showed that residing in rural areas (versus urban) increased malaria incidence rates by over three-fold and mean indoor female A. gambiae and funestus numbers by nearly two-fold. Compared to those residing in the lowest quality houses, children residing in the highest quality houses had one-third lower malaria incidence rates, even when wealth and rural residence were controlled for. Living in the highest quality houses reduced vector numbers while having cattle near the house significantly increased them. Results corroborate findings from other studies that show associations between malaria incidence and housing quality; associations were concentrated amongst the highest quality houses.

Evaluation of textile substrates for dispensing synthetic attractants for malaria mosquitoes.

PubMed

Mweresa, Collins K; Mukabana, Wolfgang R; Omusula, Philemon; Otieno, Bruno; Gheysens, Tom; Takken, Willem; van Loon, Joop J A

2014-08-16

The full-scale impact of odour-baited technology on the surveillance, sampling and control of vectors of infectious diseases is partly limited by the lack of methods for the efficient and sustainable dispensing of attractants. In this study we investigated whether locally-available and commonly used textiles are efficient substrates for the release of synthetic odorant blends attracting malaria mosquitoes. The relative efficacy of (a) polyester, (b) cotton, (c) cellulose + polyacrylate, and (d) nylon textiles as substrates for dispensing a synthetic odour blend (Ifakara blend 1(IB1)) that attracts malaria mosquitoes was evaluated in western Kenya. The study was conducted through completely randomized Latin square experimental designs under semi-field and field conditions. Traps charged with IB1-impregnated polyester, cotton and cellulose + polyacrylate materials caught significantly more female Anopheles gambiae sensu stricto (semi-field conditions) and An. gambiae sensu lato (field conditions) mosquitoes than IB1-treated nylon (P = 0.001). The IB1-impregnated cellulose + polyacrylate material was the most attractive to female An. funestus mosquitoes compared to all other dispensing textile substrates (P < 0.001). The responses of female An. funestus mosquitoes to IB1-treated cotton and polyester were equal (P = 0.45). Significantly more female Culex mosquitoes were attracted to IB1-treated cotton than to the other treatments (P < 0.001). Whereas IB1-impregnated cotton and cellulose + polyacrylate material attracted equal numbers of female Mansonia mosquitoes (P = 0.44), the catches due to these two substrates were significantly higher than those associated with the other substrates (P < 0.001). The number and species of mosquitoes attracted to a synthetic odour blend is influenced by the type of odour-dispensing material used. Thus, surveillance and intervention programmes for malaria and other mosquito vectors using attractive odour baits should select an odour-release material that optimizes the odour blend.

Predictive Computational Modeling of Chromatin Folding

NASA Astrophysics Data System (ADS)

di Pierro, Miichele; Zhang, Bin; Wolynes, Peter J.; Onuchic, Jose N.

In vivo, the human genome folds into well-determined and conserved three-dimensional structures. The mechanism driving the folding process remains unknown. We report a theoretical model (MiChroM) for chromatin derived by using the maximum entropy principle. The proposed model allows Molecular Dynamics simulations of the genome using as input the classification of loci into chromatin types and the presence of binding sites of loop forming protein CTCF. The model was trained to reproduce the Hi-C map of chromosome 10 of human lymphoblastoid cells. With no additional tuning the model was able to predict accurately the Hi-C maps of chromosomes 1-22 for the same cell line. Simulations show unknotted chromosomes, phase separation of chromatin types and a preference of chromatin of type A to sit at the periphery of the chromosomes.

Cytogenetic evidence of mixed disomic and polysomic inheritance in an allotetraploid (AABB) Musa genotype

PubMed Central

Jeridi, Mouna; Perrier, Xavier; Rodier-Goud, Marguerite; Ferchichi, Ali; D'Hont, Angélique; Bakry, Frédéric

2012-01-01

Background and Aims Edible bananas originated mainly from two wild species, Musa acuminata Colla (AA) and Musa balbisiana Colla (BB), and triploid cultivars with an AAA, AAB or ABB genome are the most widely used. In the present study, chromosome pairing affinities are investigated in a sterile AB Indian variety and in its fertile colchicine-induced allotetraploid (AABB) derivative to determine the inheritance pattern of the tetraploid genotype. The potential implications of interspecific recombination and chromosomal composition of diploid gametes for Musa improvement are presented. Methods The pairing of different chromosome sets at diploid and tetraploid levels was investigated through a combination of conventional cytogenetic and genomic in-situ hybridization (GISH) analyses of meiotic chromosomes, leading to a likelihood model of the pairing behaviour. GISH analysis of mitotic chromosomes was also conducted to reveal the chromosome constitution of hybrids derived from crosses involving the allotetraploid genotype. Key Results Analysis of chromosome associations at both ploidy levels suggested that the newly formed allotetraploid behaves as a ‘segmental allotetraploid’ with three chromosome sets in a tetrasomic pattern, three sets in a likely disomic pattern and the five remaining sets in an intermediate pattern. Balanced and unbalanced diploid gametes were detected in progenies, with the chromosome constitution appearing to be more homogenous in pollen than in ovules. Conclusions Colchicine-induced allotetraploids in Musa provide access to the genetic background of natural AB varieties. The segmental inheritance pattern exhibited by the AABB allotetraploid genotype implies chromosome exchanges between M. acuminata and M. balbisiana species and opens new horizons for reciprocal transfer of valuable alleles. PMID:23087127

Cytogenetic evidence of mixed disomic and polysomic inheritance in an allotetraploid (AABB) Musa genotype.

PubMed

Jeridi, Mouna; Perrier, Xavier; Rodier-Goud, Marguerite; Ferchichi, Ali; D'Hont, Angélique; Bakry, Frédéric

2012-12-01

Edible bananas originated mainly from two wild species, Musa acuminata Colla (AA) and Musa balbisiana Colla (BB), and triploid cultivars with an AAA, AAB or ABB genome are the most widely used. In the present study, chromosome pairing affinities are investigated in a sterile AB Indian variety and in its fertile colchicine-induced allotetraploid (AABB) derivative to determine the inheritance pattern of the tetraploid genotype. The potential implications of interspecific recombination and chromosomal composition of diploid gametes for Musa improvement are presented. The pairing of different chromosome sets at diploid and tetraploid levels was investigated through a combination of conventional cytogenetic and genomic in-situ hybridization (GISH) analyses of meiotic chromosomes, leading to a likelihood model of the pairing behaviour. GISH analysis of mitotic chromosomes was also conducted to reveal the chromosome constitution of hybrids derived from crosses involving the allotetraploid genotype. Analysis of chromosome associations at both ploidy levels suggested that the newly formed allotetraploid behaves as a 'segmental allotetraploid' with three chromosome sets in a tetrasomic pattern, three sets in a likely disomic pattern and the five remaining sets in an intermediate pattern. Balanced and unbalanced diploid gametes were detected in progenies, with the chromosome constitution appearing to be more homogenous in pollen than in ovules. Colchicine-induced allotetraploids in Musa provide access to the genetic background of natural AB varieties. The segmental inheritance pattern exhibited by the AABB allotetraploid genotype implies chromosome exchanges between M. acuminata and M. balbisiana species and opens new horizons for reciprocal transfer of valuable alleles.

TP53-dependent chromosome instability is associated with transient reductions in telomere length in immortal telomerase-positive cell lines

NASA Technical Reports Server (NTRS)

Schwartz, J. L.; Jordan, R.; Liber, H.; Murnane, J. P.; Evans, H. H.

2001-01-01

Telomere shortening in telomerase-negative somatic cells leads to the activation of the TP53 protein and the elimination of potentially unstable cells. We examined the effect of TP53 gene expression on both telomere metabolism and chromosome stability in immortal, telomerase-positive cell lines. Telomere length, telomerase activity, and chromosome instability were measured in multiple clones isolated from three related human B-lymphoblast cell lines that vary in TP53 expression; TK6 cells express wild-type TP53, WTK1 cells overexpress a mutant form of TP53, and NH32 cells express no TP53 protein. Clonal variations in both telomere length and chromosome stability were observed, and shorter telomeres were associated with higher levels of chromosome instability. The shortest telomeres were found in WTK1- and NH32-derived cells, and these cells had 5- to 10-fold higher levels of chromosome instability. The primary marker of instability was the presence of dicentric chromosomes. Aneuploidy and other stable chromosome alterations were also found in clones showing high levels of dicentrics. Polyploidy was found only in WTK1-derived cells. Both telomere length and chromosome instability fluctuated in the different cell populations with time in culture, presumably as unstable cells and cells with short telomeres were eliminated from the growing population. Our results suggest that transient reductions in telomere lengths may be common in immortal cell lines and that these alterations in telomere metabolism can have a profound effect on chromosome stability. Copyright 2000 Wiley-Liss, Inc.

"Holostei versus Halecostomi" Problem: Insight from Cytogenetics of Ancient Nonteleost Actinopterygian Fish, Bowfin Amia calva.

PubMed

Majtánová, Zuzana; Symonová, Radka; Arias-Rodriguez, Lenin; Sallan, Lauren; Ráb, Petr

2017-11-01

Bowfin belongs to an ancient lineage of nonteleost ray-finned fishes (actinopterygians) and is the only extant survivor of a once diverged group, the Halecomorphi or Amiiformes. Owing to the scarcity of extant nonteleost ray-finned lineages, also referred as "living fossils," their phylogenetic interrelationships have been the target of multiple hypotheses concerning their sister group relationships. Molecular and morphological data sets have produced controversial results; bowfin is considered as either the sister group to genome-duplicated teleosts (together forming the group of Halecostomi) or to gars (Lepisosteiformes; together forming the group of Holostei). However, any detailed cytogenetic analysis of bowfin chromosomes has never been performed to address this issue. Here we examined bowfin chromosomes by conventional (Giemsa-staining, C-banding, base-specific fluorescence and silver staining) and molecular (FISH with rDNA probes) cytogenetic protocols. We identified diploid chromosome number 2n = 46 with a middle-sized submetacentric chromosome pair as the major ribosomal DNA-bearing (45S rDNA), GC-positive and silver-positive element. The minor rDNA (5S rDNA) sites were localized in the pericentromeric region of one middle-sized acrocentric chromosome pair. Comparison with available cytogenetic data of other nonteleost actinopterygians (bichirs, sturgeons, gars) and teleost species including representative of basally branching lineages showed bowfin chromosomal characteristics more similar to the teleost type than to any other nonteleosts. Particularly striking differences were identified between bowfin and gars, the latter of which were found to mimic mammalian AT/GC genomic organisation. Such conclusion however contradicts the most recent phylogenomic results and raises the question what states are ancestral and what are derived. © 2017 Wiley Periodicals, Inc.

Genomics of Natural Populations: How Differentially Expressed Genes Shape the Evolution of Chromosomal Inversions in Drosophila pseudoobscura

PubMed Central

Fuller, Zachary L.; Haynes, Gwilym D.; Richards, Stephen; Schaeffer, Stephen W.

2016-01-01

Chromosomal rearrangements can shape the structure of genetic variation in the genome directly through alteration of genes at breakpoints or indirectly by holding combinations of genetic variants together due to reduced recombination. The third chromosome of Drosophila pseudoobscura is a model system to test hypotheses about how rearrangements are established in populations because its third chromosome is polymorphic for >30 gene arrangements that were generated by a series of overlapping inversion mutations. Circumstantial evidence has suggested that these gene arrangements are selected. Despite the expected homogenizing effects of extensive gene flow, the frequencies of arrangements form gradients or clines in nature, which have been stable since the system was first described >80 years ago. Furthermore, multiple arrangements exist at appreciable frequencies across several ecological niches providing the opportunity for heterokaryotypes to form. In this study, we tested whether genes are differentially expressed among chromosome arrangements in first instar larvae, adult females and males. In addition, we asked whether transcriptional patterns in heterokaryotypes are dominant, semidominant, overdominant, or underdominant. We find evidence for a significant abundance of differentially expressed genes across the inverted regions of the third chromosome, including an enrichment of genes involved in sensory perception for males. We find the majority of loci show additivity in heterokaryotypes. Our results suggest that multiple genes have expression differences among arrangements that were either captured by the original inversion mutation or accumulated after it reached polymorphic frequencies, providing a potential source of genetic variation for selection to act upon. These data suggest that the inversions are favored because of their indirect effect of recombination suppression that has held different combinations of differentially expressed genes together in the various gene arrangement backgrounds. PMID:27401754

Relationship between radiation-induced aberrations in individual chromosomes and their DNA content: effects of interaction distance

NASA Technical Reports Server (NTRS)

Wu, H.; Durante, M.; Lucas, J. N.

2001-01-01

PURPOSE: To study the effect of the interaction distance on the frequency of inter- and intrachromosome exchanges in individual chromosomes with respect to their DNA content. Assumptions: Chromosome exchanges are formed by misrejoining of two DNA double-strand breaks (DSB) induced within an interaction distance, d. It is assumed that chromosomes in G(0)/G(1) phase of the cell cycle occupy a spherical domain in a cell nucleus, with no spatial overlap between individual chromosome domains. RESULTS: Formulae are derived for the probability of formation of inter-, as well as intra-, chromosome exchanges relating to the DNA content of the chromosome for a given interaction distance. For interaction distances <1 microm, the relative frequency of interchromosome exchanges predicted by the present model is similar to that by Cigarran et al. (1998) based on the assumption that the probability of interchromosome exchanges is proportional to the "surface area" of the chromosome territory. The "surface area" assumption is shown to be a limiting case of d-->0 in the present model. The present model also predicts that the probability of intrachromosome exchanges occurring in individual chromosomes is proportional to their DNA content with correction terms. CONCLUSION: When the interaction distance is small, the "surface area" distribution for chromosome participation in interchromosome exchanges has been expected. However, the present model shows that for the interaction distance as large as 1 microm, the predicted probability of interchromosome exchange formation is still close to the surface area distribution. Therefore, this distribution does not necessarily rule out the formation of complex chromosomal aberrations by long-range misrejoining of DSB.

Fish Karyome version 2.1: a chromosome database of fishes and other aquatic organisms

PubMed Central

Nagpure, Naresh Sahebrao; Pathak, Ajey Kumar; Pati, Rameshwar; Rashid, Iliyas; Sharma, Jyoti; Singh, Shri Prakash; Singh, Mahender; Sarkar, Uttam Kumar; Kushwaha, Basdeo; Kumar, Ravindra; Murali, S.

2016-01-01

A voluminous information is available on karyological studies of fishes; however, limited efforts were made for compilation and curation of the available karyological data in a digital form. ‘Fish Karyome’ database was the preliminary attempt to compile and digitize the available karyological information on finfishes belonging to the Indian subcontinent. But the database had limitations since it covered data only on Indian finfishes with limited search options. Perceiving the feedbacks from the users and its utility in fish cytogenetic studies, the Fish Karyome database was upgraded by applying Linux, Apache, MySQL and PHP (pre hypertext processor) (LAMP) technologies. In the present version, the scope of the system was increased by compiling and curating the available chromosomal information over the globe on fishes and other aquatic organisms, such as echinoderms, molluscs and arthropods, especially of aquaculture importance. Thus, Fish Karyome version 2.1 presently covers 866 chromosomal records for 726 species supported with 253 published articles and the information is being updated regularly. The database provides information on chromosome number and morphology, sex chromosomes, chromosome banding, molecular cytogenetic markers, etc. supported by fish and karyotype images through interactive tools. It also enables the users to browse and view chromosomal information based on habitat, family, conservation status and chromosome number. The system also displays chromosome number in model organisms, protocol for chromosome preparation and allied techniques and glossary of cytogenetic terms. A data submission facility has also been provided through data submission panel. The database can serve as a unique and useful resource for cytogenetic characterization, sex determination, chromosomal mapping, cytotaxonomy, karyo-evolution and systematics of fishes. Database URL: http://mail.nbfgr.res.in/Fish_Karyome PMID:26980518

Fish Karyome version 2.1: a chromosome database of fishes and other aquatic organisms.

PubMed

Nagpure, Naresh Sahebrao; Pathak, Ajey Kumar; Pati, Rameshwar; Rashid, Iliyas; Sharma, Jyoti; Singh, Shri Prakash; Singh, Mahender; Sarkar, Uttam Kumar; Kushwaha, Basdeo; Kumar, Ravindra; Murali, S

2016-01-01

A voluminous information is available on karyological studies of fishes; however, limited efforts were made for compilation and curation of the available karyological data in a digital form. 'Fish Karyome' database was the preliminary attempt to compile and digitize the available karyological information on finfishes belonging to the Indian subcontinent. But the database had limitations since it covered data only on Indian finfishes with limited search options. Perceiving the feedbacks from the users and its utility in fish cytogenetic studies, the Fish Karyome database was upgraded by applying Linux, Apache, MySQL and PHP (pre hypertext processor) (LAMP) technologies. In the present version, the scope of the system was increased by compiling and curating the available chromosomal information over the globe on fishes and other aquatic organisms, such as echinoderms, molluscs and arthropods, especially of aquaculture importance. Thus, Fish Karyome version 2.1 presently covers 866 chromosomal records for 726 species supported with 253 published articles and the information is being updated regularly. The database provides information on chromosome number and morphology, sex chromosomes, chromosome banding, molecular cytogenetic markers, etc. supported by fish and karyotype images through interactive tools. It also enables the users to browse and view chromosomal information based on habitat, family, conservation status and chromosome number. The system also displays chromosome number in model organisms, protocol for chromosome preparation and allied techniques and glossary of cytogenetic terms. A data submission facility has also been provided through data submission panel. The database can serve as a unique and useful resource for cytogenetic characterization, sex determination, chromosomal mapping, cytotaxonomy, karyo-evolution and systematics of fishes. Database URL: http://mail.nbfgr.res.in/Fish_Karyome. © The Author(s) 2016. Published by Oxford University Press.

Chromatin remodeling in somatic cells injected into mature pig oocytes.

PubMed

Bui, Hong-Thuy; Van Thuan, Nguyen; Wakayama, Teruhiko; Miyano, Takashi

2006-06-01

We examined the involvement of histone H3 modifications in the chromosome condensation and decondensation of somatic cell nuclei injected into mature pig oocytes. Nuclei of pig granulosa cells were transferred into in vitro matured intact pig oocytes, and histone H3 phosphorylation, acetylation, and methylation were examined by immunostaining with specific antibodies in relation to changes in chromosome morphology. In the condensed chromosomes of pig oocytes at metaphase II, histone H3 was phosphorylated at serine 10 (H3-S10) and serine 28 (H3-S28), and methylated at lysine 9 (H3-K9), but was not acetylated at lysine 9, 14 and 18 (H3-K9, H3-K14 and H3-K18). During the first 2 h after nuclear transfer, a series of events were observed in the somatic nuclei: nuclear membrane disassembly; chromosome condensation to form a metaphase-like configuration; an increase in histone H3 phosphorylation levels (H3-S10 and H3-S28). Next, pig oocytes injected with nuclei of somatic cells were electroactivated and the chromosome morphology of oocytes and somatic cells was examined along with histone modifications. Generally, chromosomes of the somatic cells showed a similar progression of cell cycle stage to that of oocytes, through anaphase II- and telophase II-like stages then formed pronucleus-like structures, although the morphology of the spindles differed from that of oocyte spindles. The chromosomes of somatic cells also showed changes in histone H3 dephosphorylation and reacetylation, similar to oocytes. In contrast, histone H3 methylation (H3-K9) of somatic cell nuclei did not show any significant change after injection and electroactivation of the oocytes. These results suggest that nuclear remodeling including histone H3 phosphorylation and acetylation of injected somatic nuclei took place in the oocytes under regulation by the oocyte cytoplasm.

Linkage of hereditary haemorrhagic telangiectasia to chromosome 9q34 and evidence for locus heterogeneity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Breedveld, G.J.; Heutink, P.; Haitjema, T.

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disorder with unknown pathophysiology that is characterized by arteriovenous lesions and recurrent hemorrhage in virtually every organ. The prevalence of HHT ranges between 1-2 per 100,000 and 1 per 10,000 with almost complete penetrance by the age of 40 years. The mode of inheritance is autosomal dominant. Linkage of HHT to markers on chromosome 9q has recently been reported. In this study we present confirmation of this localization in three unrelated families of Dutch origin. A fourth family yielded evidence for non-linkage to this region. Heterogeneity analysis was performed and clearly demonstratedmore » that HHT is a genetically heterogeneous disorder. We have rigorously investigated all patients in our four families by chest radiography, measurement of arterial oxygenation iv-DSA of the pulmonary circulation and iv-DSA of the cerebral circulation. In the family that is not linked to chromosome 9, considerably less pulmonary arteriovenous malformations (PAVM) were present. We conclude that HHT is a genetically heterogeneous disorder and our results indicate that the presence of PAVM may be more common in patients with a chromosome 9-linked form of HHT than in patients with the non-linked form. Linkage of HHT with a locus on chromosome 9q34 locus has now been reported in three independent studies. However, two studies report genetic heterogeneity. This will limit the applicability of linked DNA markers in small families for presymptomatic testing. Only extended pedigrees will be informative enough to determine whether or not the chromosome 9 locus is responsible for disease onset in the patient. The eventual isolation of the gene responsible for HHT on chromosome 9 will help to gain insight into the processes that take place in the development and remodelling of the vascular system.« less

Is early-onset microsatellite and chromosomally stable colorectal cancer a hallmark of a genetic susceptibility syndrome?

PubMed

Kets, C M; van Krieken, J H J M; van Erp, P E J; Feuth, T; Jacobs, Y H A; Brunner, H G; Ligtenberg, M J L; Hoogerbrugge, N

2008-02-15

Most colorectal cancers show either microsatellite or chromosomal instability. A subset of colorectal cancers, especially those diagnosed at young age, is known to show neither of these forms of genetic instability and thus might have a distinct pathogenesis. Colorectal cancers diagnosed at young age are suggestive for hereditary predisposition. We investigate whether such early-onset microsatellite and chromosomally stable colorectal cancers are a hallmark of a genetic susceptibility syndrome. The ploidy status of microsatellite stable (familial) colorectal cancers of patients diagnosed before age 50 (n = 127) was analyzed in relation to the histopathological characteristics and family history. As a control the ploidy status of sporadic colorectal cancer, with normal staining of mismatch repair proteins, diagnosed at the age of 69 years or above (n = 70) was determined. A diploid DNA content was used as a marker for chromosomal stability. Within the group of patients with (familial) early onset microsatellite stable colorectal cancer the chromosomally stable tumors did not differ from chromosomally unstable tumors with respect to mean age at diagnosis, fulfillment of Amsterdam criteria or pathological characteristics. Segregation analysis did not reveal any family with microsatellite and chromosomally stable colorectal cancer in 2 relatives. The prevalence of microsatellite and chromosomally stable colorectal cancer was not significantly different for the early and late onset group (28 and 21%, respectively). We find no evidence that early-onset microsatellite and chromosomally stable colorectal cancer is a hallmark of a hereditary colorectal cancer syndrome. (c) 2007 Wiley-Liss, Inc.

Sperm-FISH analysis in a pericentric chromosome 1 inversion, 46,XY,inv(1)(p22q42), associated with infertility.

PubMed

Chantot-Bastaraud, S; Ravel, C; Berthaut, I; McElreavey, K; Bouchard, P; Mandelbaum, J; Siffroi, J P

2007-01-01

No phenotypic effect is observed in most inversion heterozygotes. However, reproductive risks may occur in the form of infertility, spontaneous abortions or chromosomally unbalanced children as a consequence of meiotic recombination between inverted and non-inverted chromosomes. An odd number of crossovers within the inverted segment results in gametes bearing recombinant chromosomes with a duplication of the region outside of the inversion segment of one arm and a deletion of the terminal segment of the other arm [dup(p)/del(q) and del(p)/dup(q)]. Using fluorescence in-situ hybridization (FISH), the chromosome segregation of a pericentric inversion of chromosome 1 was studied in spermatozoa of a inv(1)(p22q42) heterozygous carrier. Three-colour FISH was performed on sperm samples using a probe mixture consisting of chromosome 1p telomere-specific probe, chromosome 1q telomere-specific probe and chromosome 18 centromere-specific alpha satellite DNA probe. The frequency of the non-recombinant product was 80.1%. The frequencies of the two types of recombinants carrying a duplication of the short arm and a deletion of the long arm, and vice versa, were respectively 7.6 and 7.2%, and these frequencies were not statistically significant from the expected ratio of 1:1. Sperm-FISH allows the further understanding of segregation patterns and their effect on reproductive failure and allows an accurate genetic counselling.

Elucidating the triplicated ancestral genome structure of radish based on chromosome-level comparison with the Brassica genomes.

PubMed

Jeong, Young-Min; Kim, Namshin; Ahn, Byung Ohg; Oh, Mijin; Chung, Won-Hyong; Chung, Hee; Jeong, Seongmun; Lim, Ki-Byung; Hwang, Yoon-Jung; Kim, Goon-Bo; Baek, Seunghoon; Choi, Sang-Bong; Hyung, Dae-Jin; Lee, Seung-Won; Sohn, Seong-Han; Kwon, Soo-Jin; Jin, Mina; Seol, Young-Joo; Chae, Won Byoung; Choi, Keun Jin; Park, Beom-Seok; Yu, Hee-Ju; Mun, Jeong-Hwan

2016-07-01

This study presents a chromosome-scale draft genome sequence of radish that is assembled into nine chromosomal pseudomolecules. A comprehensive comparative genome analysis with the Brassica genomes provides genomic evidences on the evolution of the mesohexaploid radish genome. Radish (Raphanus sativus L.) is an agronomically important root vegetable crop and its origin and phylogenetic position in the tribe Brassiceae is controversial. Here we present a comprehensive analysis of the radish genome based on the chromosome sequences of R. sativus cv. WK10039. The radish genome was sequenced and assembled into 426.2 Mb spanning >98 % of the gene space, of which 344.0 Mb were integrated into nine chromosome pseudomolecules. Approximately 36 % of the genome was repetitive sequences and 46,514 protein-coding genes were predicted and annotated. Comparative mapping of the tPCK-like ancestral genome revealed that the radish genome has intermediate characteristics between the Brassica A/C and B genomes in the triplicated segments, suggesting an internal origin from the genus Brassica. The evolutionary characteristics shared between radish and other Brassica species provided genomic evidences that the current form of nine chromosomes in radish was rearranged from the chromosomes of hexaploid progenitor. Overall, this study provides a chromosome-scale draft genome sequence of radish as well as novel insight into evolution of the mesohexaploid genomes in the tribe Brassiceae.

The microtubule-binding and coiled-coil domains of Kid are required to turn off the polar ejection force at anaphase.

PubMed

Soeda, Shou; Yamada-Nomoto, Kaori; Ohsugi, Miho

2016-10-01

Mitotic chromosomes move dynamically along the spindle microtubules using the forces generated by motor proteins such as chromokinesin Kid (also known as KIF22). Kid generates a polar ejection force and contributes to alignment of the chromosome arms during prometaphase and metaphase, whereas during anaphase, Kid contributes to chromosome compaction. How Kid is regulated and how this regulation is important for chromosome dynamics remains unclear. Here, we address these questions by expressing mutant forms of Kid in Kid-deficient cells. We demonstrate that Cdk1-mediated phosphorylation of Thr463 is required to generate the polar ejection force on Kid-binding chromosomes, whereas dephosphorylation of Thr463 prevents generation of the ejection force on such chromosomes. In addition to activation of the second microtubule-binding domain through dephosphorylation of Thr463, the coiled-coil domain is essential in suspending generation of the polar ejection force, preventing separated chromosomes from becoming recongressed during anaphase. We propose that phosphorylation of Thr463 switches the mitotic chromosome movement from an anti-poleward direction to a poleward direction by converting the Kid functional mode from polar-ejection-force-ON to -OFF during the metaphase-anaphase transition, and that both the second microtubule-binding domain and the coiled-coil domain are involved in this switching process. © 2016. Published by The Company of Biologists Ltd.

Satellite DNA and Transposable Elements in Seabuckthorn (Hippophae rhamnoides), a Dioecious Plant with Small Y and Large X Chromosomes.

PubMed

Puterova, Janka; Razumova, Olga; Martinek, Tomas; Alexandrov, Oleg; Divashuk, Mikhail; Kubat, Zdenek; Hobza, Roman; Karlov, Gennady; Kejnovsky, Eduard

2017-01-01

Seabuckthorn (Hippophae rhamnoides) is a dioecious shrub commonly used in the pharmaceutical, cosmetic, and environmental industry as a source of oil, minerals and vitamins. In this study, we analyzed the transposable elements and satellites in its genome. We carried out Illumina DNA sequencing and reconstructed the main repetitive DNA sequences. For data analysis, we developed a new bioinformatics approach for advanced satellite DNA analysis and showed that about 25% of the genome consists of satellite DNA and about 24% is formed of transposable elements, dominated by Ty3/Gypsy and Ty1/Copia LTR retrotransposons. FISH mapping revealed X chromosome-accumulated, Y chromosome-specific or both sex chromosomes-accumulated satellites but most satellites were found on autosomes. Transposable elements were located mostly in the subtelomeres of all chromosomes. The 5S rDNA and 45S rDNA were localized on one autosomal locus each. Although we demonstrated the small size of the Y chromosome of the seabuckthorn and accumulated satellite DNA there, we were unable to estimate the age and extent of the Y chromosome degeneration. Analysis of dioecious relatives such as Shepherdia would shed more light on the evolution of these sex chromosomes. © The Author(s) 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Three-dimensional microscopy of the Rad51 recombination protein during meiotic prophase.

PubMed Central

Franklin, A E; McElver, J; Sunjevaric, I; Rothstein, R; Bowen, B; Cande, W Z

1999-01-01

An open question in meiosis is whether the Rad51 recombination protein functions solely in meiotic recombination or whether it is also involved in the chromosome homology search. To address this question, we have performed three-dimensional high-resolution immunofluorescence microscopy to visualize native Rad51 structures in maize male meiocytes. Maize has two closely related RAD51 genes that are expressed at low levels in differentiated tissues and at higher levels in mitotic and meiotic tissues. Cells and nuclei were specially fixed and embedded in polyacrylamide to maintain both native chromosome structure and the three dimensionality of the specimens. Analysis of Rad51 in maize meiocytes revealed that when chromosomes condense during leptotene, Rad51 is diffuse within the nucleus. Rad51 foci form on the chromosomes at the beginning of zygotene and rise to approximately 500 per nucleus by mid-zygotene when chromosomes are pairing and synapsing. During chromosome pairing, we consistently found two contiguous Rad51 foci on paired chromosomes. These paired foci may identify the sites where DNA sequence homology is being compared. During pachytene, the number of Rad51 foci drops to seven to 22 per nucleus. This higher number corresponds approximately to the number of chiasmata in maize meiosis. These observations are consistent with a role for Rad51 in the homology search phase of chromosome pairing in addition to its known role in meiotic recombination. PMID:10330467

Centromeric and non-centromeric satellite DNA organisation differs in holocentric Rhynchospora species.

PubMed

Ribeiro, Tiago; Marques, André; Novák, Petr; Schubert, Veit; Vanzela, André L L; Macas, Jiri; Houben, Andreas; Pedrosa-Harand, Andrea

2017-03-01

Satellite DNA repeats (or satDNA) are fast-evolving sequences usually associated with condensed heterochromatin. To test whether the chromosomal organisation of centromeric and non-centromeric satDNA differs in species with holocentric chromosomes, we identified and characterised the major satDNA families in the holocentric Cyperaceae species Rhynchospora ciliata (2n = 10), R. globosa (2n = 50) and R. tenuis (2n = 2x = 4 and 2n = 4x = 8). While conserved centromeric repeats (present in R. ciliata and R. tenuis) revealed linear signals at both chromatids, non-centromeric, species-specific satDNAs formed distinct clusters along the chromosomes. Colocalisation of both repeat types resulted in a ladder-like hybridisation pattern at mitotic chromosomes. In interphase, the centromeric satDNA was dispersed while non-centromeric satDNA clustered and partly colocalised to chromocentres. Despite the banding-like hybridisation patterns of the clustered satDNA, the identification of chromosome pairs was impaired due to the irregular hybridisation patterns of the homologues in R. tenuis and R. ciliata. These differences are probably caused by restricted or impaired meiotic recombination as reported for R. tenuis, or alternatively by complex chromosome rearrangements or unequal condensation of homologous metaphase chromosomes. Thus, holocentricity influences the chromosomal organisation leading to differences in the distribution patterns and condensation dynamics of centromeric and non-centromeric satDNA.

CedA is a novel Escherichia coli protein that activates the cell division inhibited by chromosomal DNA over-replication.

PubMed

Katayama, T; Takata, M; Sekimizu, K

1997-11-01

We isolated and characterized a new gene related to the control of cell division regulation in Escherichia coli. At 30 degrees C, the dnaAcos mutant causes over-replication of the chromosome, and colony formation is inhibited. We found that, at this temperature, the dnaAcos cells form filaments; therefore, septum formation is inhibited. This inhibition was independent of SfiA, an inhibitor of the septum-forming protein, FtsZ. To identify factors involved in this pathway of inhibition, we isolated seven multicopy suppressors for the cold-sensitive phenotype of the dnaAcos mutant. One of these proved to be a previously unknown gene, which we named cedA. This gene encoded a 12 kDa protein and resided at 38.9min on the E. coli genome map. A multicopy supply of the cedA gene to the dnaAcos cells did not repress over-replication of the chromosome but did stimulate cell division of the host, the result being growth of cells with an abnormally elevated chromosomal copy number. Therefore, the expression level of the cedA gene seems to be important for inhibiting cell division of the dnaAcos mutant at 30 degrees C. We propose that over-replication of the chromosome activates a pathway for inhibiting cell division and that the cedA gene modulates this division control. In the dnaA+ background, cedA also seems to affect cell division.

Uncoupling of sexual reproduction from homologous recombination in homozygous Oenothera species.

PubMed

Rauwolf, U; Greiner, S; Mráček, J; Rauwolf, M; Golczyk, H; Mohler, V; Herrmann, R G; Meurer, J

2011-07-01

Salient features of the first meiotic division are independent segregation of chromosomes and homologous recombination (HR). In non-sexually reproducing, homozygous species studied to date HR is absent. In this study, we constructed the first linkage maps of homozygous, bivalent-forming Oenothera species and provide evidence that HR was exclusively confined to the chromosome ends of all linkage groups in our population. Co-segregation of complementary DNA-based markers with the major group of AFLP markers indicates that HR has only a minor role in generating genetic diversity of this taxon despite its efficient adaptation capability. Uneven chromosome condensation during meiosis in Oenothera may account for restriction of HR. The use of plants with ancient chromosomal arm arrangement demonstrates that limitation of HR occurred before and independent from species hybridizations and reciprocal translocations of chromosome arms-a phenomenon, which is widespread in the genus. We propose that consecutive loss of HR favored the evolution of reciprocal translocations, beneficial superlinkage groups and ultimately permanent translocation heterozygosity.

Separable Roles for a Caenorhabditis elegans RMI1 Homolog in Promoting and Antagonizing Meiotic Crossovers Ensure Faithful Chromosome Inheritance

PubMed Central

Jagut, Marlène; Hamminger, Patricia; Woglar, Alexander; Millonigg, Sophia; Paulin, Luis; Mikl, Martin; Dello Stritto, Maria Rosaria; Tang, Lois; Habacher, Cornelia; Tam, Angela; Gallach, Miguel; von Haeseler, Arndt; Villeneuve, Anne M.; Jantsch, Verena

2016-01-01

During the first meiotic division, crossovers (COs) between homologous chromosomes ensure their correct segregation. COs are produced by homologous recombination (HR)-mediated repair of programmed DNA double strand breaks (DSBs). As more DSBs are induced than COs, mechanisms are required to establish a regulated number of COs and to repair remaining intermediates as non-crossovers (NCOs). We show that the Caenorhabditis elegans RMI1 homolog-1 (RMH-1) functions during meiosis to promote both CO and NCO HR at appropriate chromosomal sites. RMH-1 accumulates at CO sites, dependent on known pro-CO factors, and acts to promote CO designation and enforce the CO outcome of HR-intermediate resolution. RMH-1 also localizes at NCO sites and functions in parallel with SMC-5 to antagonize excess HR-based connections between chromosomes. Moreover, RMH-1 also has a major role in channeling DSBs into an NCO HR outcome near the centers of chromosomes, thereby ensuring that COs form predominantly at off-center positions. PMID:27011106

Small Molecule Disrupts Abnormal Gene Fusion Associated with Leukemia | Center for Cancer Research

Cancer.gov

Rare chromosomal abnormalities, called chromosomal translocations, in which part of a chromosome breaks off and becomes attached to another chromosome, can result in the generation of chimeric proteins. These aberrant proteins have unpredictable, and sometimes harmful, functions, including uncontrolled cell growth that can lead to cancer. One type of translocation, in which a portion of the gene encoding nucleoporin 98 (NUP98)—one of about 50 proteins comprising the nuclear pore complex through which proteins are shuttled into and out of the nucleus—fuses with another gene, has been shown to result in improper histone modifications. These abnormalities alter the gene expression patterns of certain types of hematopoietic, or blood-forming, stem cells, resulting primarily in overexpression of the Hoxa7, Hoxa9,and Hoxa10 genes. NUP98 chromosomal translocations have been associated with many types of leukemia, including acute myeloid leukemia (AML), acute lymphoid leukemia (ALL), chronic myeloid leukemia in blast crisis (CML-bc), and myelodysplastic syndrome (MDS).

Translating Dosage Compensation to Trisomy 21

PubMed Central

Jiang, Jun; Jing, Yuanchun; Cost, Gregory J.; Chiang, Jen-Chieh; Kolpa, Heather J.; Cotton, Allison M.; Carone, Dawn M.; Carone, Benjamin R.; Shivak, David A.; Guschin, Dmitry Y.; Pearl, Jocelynn R.; Rebar, Edward J.; Byron, Meg; Gregory, Philip D.; Brown, Carolyn J.; Urnov, Fyodor D.; Hall, Lisa L.; Lawrence, Jeanne B.

2013-01-01

Down syndrome (DS) is a common disorder with enormous medical and social costs, caused by trisomy for chromosome 21 (Chr21). We tested the concept that gene imbalance across an extra chromosome can be de facto corrected by manipulating a single gene, XIST. Using genome editing with zinc finger nucleases, we targeted a large, inducible XIST transgene into the Chr21 DYRK1A locus, in DS pluripotent stem cells. XIST RNA coats Chr21 and triggers stable heterochromatin modifications, chromosome-wide transcriptional silencing and DNA methylation to form a “Chr21 Barr Body.” This provides a model to study human chromosome inactivation and creates a system to investigate genomic expression changes and cellular pathologies of trisomy 21, free from genetic and epigenetic noise. Remarkably, deficits in proliferation and neural rosette formation are rapidly reversed upon silencing one Chr21. Successful trisomy silencing in vitro also surmounts the major first step towards potential development of “chromosome therapy”. PMID:23863942

Uncoupling of sexual reproduction from homologous recombination in homozygous Oenothera species

PubMed Central

Rauwolf, U; Greiner, S; Mráček, J; Rauwolf, M; Golczyk, H; Mohler, V; Herrmann, R G; Meurer, J

2011-01-01

Salient features of the first meiotic division are independent segregation of chromosomes and homologous recombination (HR). In non-sexually reproducing, homozygous species studied to date HR is absent. In this study, we constructed the first linkage maps of homozygous, bivalent-forming Oenothera species and provide evidence that HR was exclusively confined to the chromosome ends of all linkage groups in our population. Co-segregation of complementary DNA-based markers with the major group of AFLP markers indicates that HR has only a minor role in generating genetic diversity of this taxon despite its efficient adaptation capability. Uneven chromosome condensation during meiosis in Oenothera may account for restriction of HR. The use of plants with ancient chromosomal arm arrangement demonstrates that limitation of HR occurred before and independent from species hybridizations and reciprocal translocations of chromosome arms—a phenomenon, which is widespread in the genus. We propose that consecutive loss of HR favored the evolution of reciprocal translocations, beneficial superlinkage groups and ultimately permanent translocation heterozygosity. PMID:21448231

The constitutional t(11;22): implications for a novel mechanism responsible for gross chromosomal rearrangements

PubMed Central

Kurahashi, H; Inagaki, H; Ohye, T; Kogo, H; Tsutsumi, M; Kato, T; Tong, M; Emanuel, BS

2012-01-01

The constitutional t(11;22)(q23;q11) is the most common recurrent non-Robertsonian translocation in humans. The breakpoint sequences of both chromosomes are characterized by several hundred base pairs of palindromic AT-rich repeats (PATRRs). Similar PATRRs have also been identified at the breakpoints of other nonrecurrent translocations, suggesting that PATRR-mediated chromosomal translocation represents one of the universal pathways for gross chromosomal rearrangement in the human genome. We propose that PATRRs have the potential to form cruciform structures through intrastrand-base pairing in single-stranded DNA, creating a source of genomic instability and leading to translocations. Indeed, de novo examples of the t(11;22) are detected at a high frequency in sperm from normal healthy males. This review synthesizes recent data illustrating a novel paradigm for an apparent spermatogenesis-specific translocation mechanism. This observation has important implications pertaining to the predominantly paternal origin of de novo gross chromosomal rearrangements in humans. PMID:20507342

The X linked recessive form of XY gonadal dysgenesis with a high incidence of gonadal germ cell tumours: clinical and genetic studies.

PubMed

Mann, J R; Corkery, J J; Fisher, H J; Cameron, A H; Mayerová, A; Wolf, U; Kennaugh, A A; Woolley, V

1983-08-01

Five phenotypic females in one family had the genotype 46,XY and all had gonadal germ cell tumours. Studies of the family pedigree suggest that this form of XY gonadal dysgenesis is inherited in an X linked recessive manner. G banding of elongated metaphase chromosomes from two subjects with XY gonadal dysgenesis and a female carrier showed no aberrations of the X chromosome. The titres of H-Y antigen in three girls with XY gonadal dysgenesis were in the male control range. Thus it appears that, in the X linked form, XY gonadal dysgenesis may be caused by a point deletion or mutation of a gene on the X chromosome, which controls the gonad specific receptor for the H-Y antigen. Studies of Xg blood groups were uninformative about linkage of Xg with the X borne gene causing the XY gonadal dysgenesis. Dermatoglyphic studies in the girls with XY gonadal dysgenesis and female carriers revealed high a-b palmar ridge counts and a tendency for the A mainline to terminate in the thenar area. Both of these features have been described in patients with Turner's syndrome.

Effect of Initiation Time of Hydrostatic Pressure Shock on Chromosome Set Doubling of Tetraploidization in Turbot Scophthalmus maximus.

PubMed

Zhu, Xiangping; Lin, Zhengmei; Wu, Zhihao; Li, Jiandong; You, Feng

2017-10-01

The objective of the study was to clarify the effects of initiation time on chromosome set doubling induced by hydrostatic pressure shock through nuclear phase fluorescent microscopy in turbot Scophthalmus maximus. The ratio of developmentally delayed embryo and chromosome counting was used to assess induction efficiency. For the embryos subjected to a pressure of 67.5 MPa for 6 min at prometaphase (A group), chromosomes recovered to the pre-treatment condition after 11-min recovering. The first nuclear division and cytokinesis proceeded normally. During the second cell cycle, chromosomes did not enter into metaphase after prometaphase, but spread around for about 13 min, then assembled together and formed a large nucleus without anaphase separation; the second nuclear division and cytokinesis was inhibited. The ratio of developmentally delayed embryo showed that the second mitosis of 78% A group embryo was inhibited. The result of chromosome counting showed that the tetraploidization rate of A group was 72%. For the embryos subjected to a pressure of 67.5 MPa for 6 min at anaphase (B group), chromosomes recovered to the pre-treatment condition after about 31-min recovering. Afterwards, one telophase nucleus formed without anaphase separation; the first nuclear division was inhibited. The time of the first cleavage furrow occurrence of B group embryos delayed 27 min compared with that of A group embryos. With the first cytokinesis proceeding normally, 81.3% B group embryos were at two-cell stage around the middle of the second cell cycle after treatment. Those embryos were one of the two blastomeres containing DNA and the other without DNA. The first nuclear division of those embryos was inhibited. During the third cell cycle after treatment, 65.2% of those abovementioned embryos were at four-cell stage, cytokinesis occurred in both blastomeres, and nuclear division only occurred in the blastomere containing DNA. Of those abovementioned embryos, 14.0% were at three-cell stage and cytokinesis only occurred in the blastomere containing DNA. The result of chromosome counting showed that the tetraploidization rate of B group was only 7%. To summarize what had been mentioned above, mechanisms on chromosome set doubling of tetraploid induction would be different with different initiation time of hydrostatic pressure treatment. Chromosome set doubling was mainly due to inhibition of the second mitosis when hydrostatic pressure treatment was performed at prometaphase. Otherwise, chromosome set doubling was mainly due to inhibition of the first nuclear division when hydrostatic pressure treatment was performed at anaphase. Induction efficiency of tetraploidization resulted from inhibition of the second cleavage was higher than which resulted from inhibition of the first nuclear division. This study was the first to reveal biological mechanisms on the two viewpoints of chromosome set doubling through effect of initiation time of hydrostatic pressure treatment on chromosome set doubling in tetraploid induction.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, R.; Gardiner, R.M.; Jaervela, I.

The neuronal ceroid lipofuscinoses (NCLs) are a group of inherited neurodegenerative disorders characterized by the accumulation of autofluorescent lipopigment in neurons and other cell types. The biochemical basis of these diseases is unknown. Three main childhood forms are recognized: infantile (Santavuori-Haltia disease, CLN1), late infantile (Jansky-Bielschowsky disease, CLN2), and juvenile (Spielmeyer-Vogt-Sjoegren, Batten disease, CLN3). The CLN1 gene has been mapped to chromosome 1p and CLN3 to chromosome 16p by linkage analysis. The gene locus causing the classical late infantile form (CLN2) has not yet been mapped but has been excluded from both CLN1 and CLN3 loci. About 10% of NCLmore » cases have a typical clinical features with most of these resembling the late infantile form. 8 refs., 1 fig., 1 tab.« less

Micromechanical study of protein-DNA interactions and chromosomes

NASA Astrophysics Data System (ADS)

Marko, John

I will discuss micromechanics experiments that our group has used to analyze protein-DNA interactions and chromosome organization. In single-DNA experiments we have found that a feature of protein-DNA complexes is that their dissociation rates can depend strikingly on bulk solution concentrations of other proteins and DNA segments; I will describe experiments which demonstrate this effect, which can involve tens-fold changes in off-rates with submicromolar changes in solution concentrations. Second, I will discuss experiments aimed at analyzing large-scale human chromosome structure; we isolate metaphase chromosomes, which in their native form behave as remarkably elastic networks of chromatin. Exposure to DNA-cutting restriction enzymes completely eliminates this elasticity, indicating that there is not a mechanically contiguous protein ''scaffold'' from which the chromosome gains its stability. I will show results of siRNA experiments indicating that depletion of condensin proteins leads to destabilization of chromosome mechanics, indicating condensin's role as the major chromatin ''cross-linker'' in metaphase chromosomes. Finally I will discuss similar experiments on human G1 nuclei, where we use genetic and chemical modifications to separate the contributions of the nuclear lamina and chromatin to the mechanical stiffness of the nucleus as a whole. Supported by the NSF (DMR-1206868, MCB-1022117) and the NIH (GM105847, CA193419).

Classical and molecular cytogenetic characterization of Agonostomus monticola, a primitive species of Mugilidae (Mugiliformes).

PubMed

Nirchio, Mauro; Oliveira, Claudio; Ferreira, Irani A; Martins, Cesar; Rossi, Anna Rita; Sola, Luciana

2009-01-01

This study reports the first description of the karyotype of Agonostomus monticola, a species belonging to a genus which is considered to be the most primitive among living mugilid fish. Specimens from Panama and Venezuela were cytogenetically analysed by conventional chromosome banding (Ag and base-specific-fluorochrome staining, C-banding) and by fluorescent in situ hybridization (FISH). Agonostomus monticola showed a chromosome complement of 2n = 48, composed of 23 acrocentric and one subtelocentric chromosome pairs and a pericentromeric distribution of the C-positive heterochromatin in all chromosomes. Major ribosomal genes were found to be located on the short arms of the subtelocentric chromosome pair number 24 and minor ribosomal genes in a paracentromeric position of a single medium-sized chromosome pair. All these observed cytogenetic features are similar to those previously described in four representatives of two genera, Liza and Chelon, which are considered to be among the most advanced in the family. Thus, this karyotypic form might represent the plesiomorphic condition for the mullets. This hypothesis regarding the plesiomorphic condition, if confirmed, would shed new light on the previously inferred cytotaxonomic relationships for the studied species of Mugilidae, because the karyotype with 48 acrocentric chromosomes, which has been so far regarded as primitive for the family, would have to be considered as derived.

Complete nucleotide sequence of the Oenothera elata plastid chromosome, representing plastome I of the five distinguishable euoenothera plastomes.

PubMed

Hupfer, H; Swiatek, M; Hornung, S; Herrmann, R G; Maier, R M; Chiu, W L; Sears, B

2000-05-01

We describe the 159,443-bp [corrected] sequence of the plastid chromosome of Oenothera elata (evening primrose). The Oe. elata plastid chromosome represents type I of the five genetically distinguishable basic plastomes found in the subsection Euoenothera. The genus Oenothera provides an ideal system in which to address fundamental questions regarding the functional integration of the compartmentalised genetic system characteristic of the eukaryotic cell. Its highly developed taxonomy and genetics, together with a favourable combination of features in its genetic structure (interspecific fertility, stable heterozygous progeny, biparental transmission of organelles, and the phenomenon of complex heterozygosity), allow facile exchanges of nuclei, plastids and mitochondria, as well as individual chromosome pairs, between species. The resulting hybrids or cybrids are usually viable and fertile, but can display various forms of developmental disturbance.

Self-Organization and Forces in the Mitotic Spindle.

PubMed

Pavin, Nenad; Tolić, Iva M

2016-07-05

At the onset of division, the cell forms a spindle, a precise self-constructed micromachine composed of microtubules and the associated proteins, which divides the chromosomes between the two nascent daughter cells. The spindle arises from self-organization of microtubules and chromosomes, whose different types of motion help them explore the space and eventually approach and interact with each other. Once the interactions between the chromosomes and the microtubules have been established, the chromosomes are moved to the equatorial plane of the spindle and ultimately toward the opposite spindle poles. These transport processes rely on directed forces that are precisely regulated in space and time. In this review, we discuss how microtubule dynamics and their rotational movement drive spindle self-organization, as well as how the forces acting in the spindle are generated, balanced, and regulated.

Centromere-Like Regions in the Budding Yeast Genome

PubMed Central

Lefrançois, Philippe; Auerbach, Raymond K.; Yellman, Christopher M.; Roeder, G. Shirleen; Snyder, Michael

2013-01-01

Accurate chromosome segregation requires centromeres (CENs), the DNA sequences where kinetochores form, to attach chromosomes to microtubules. In contrast to most eukaryotes, which have broad centromeres, Saccharomyces cerevisiae possesses sequence-defined point CENs. Chromatin immunoprecipitation followed by sequencing (ChIP–Seq) reveals colocalization of four kinetochore proteins at novel, discrete, non-centromeric regions, especially when levels of the centromeric histone H3 variant, Cse4 (a.k.a. CENP-A or CenH3), are elevated. These regions of overlapping protein binding enhance the segregation of plasmids and chromosomes and have thus been termed Centromere-Like Regions (CLRs). CLRs form in close proximity to S. cerevisiae CENs and share characteristics typical of both point and regional CENs. CLR sequences are conserved among related budding yeasts. Many genomic features characteristic of CLRs are also associated with these conserved homologous sequences from closely related budding yeasts. These studies provide general and important insights into the origin and evolution of centromeres. PMID:23349633

A Novel Locus For Dilated Cardiomyopathy Maps to Canine Chromosome 8

PubMed Central

Werner, Petra; Raducha, Michael G.; Prociuk, Ulana; Sleeper, Meg M.; Henthorn, Paula S.

2008-01-01

Dilated cardiomyopathy (DCM), the most common form of cardiomyopathy, often leads to heart failure and sudden death. While a substantial proportion of DCMs are inherited, mutations responsible for the majority of DCMs remain unidentified. A genome-wide linkage study was performed to identify the locus responsible for an autosomal recessive inherited form of juvenile DCM (JDCM) in Portuguese water dogs using 16 families segregating the disease. Results link the JDCM locus to canine chromosome 8 with two-point and multipoint LOD scores of 10.8 and 14, respectively. The locus maps to a 3.9 Mb region, with complete syntenic homology to human chromosome 14, that contains no genes or loci known to be involved in the development of any type of cardiomyopathy. This discovery of a DCM locus with a previously unknown etiology will provide a new gene to examine in human DCM patients and a model for testing therapeutic approaches for heart failure. PMID:18442891

Enrichment of dynamic chromosomal crosslinks drive phase separation of the nucleolus

PubMed Central

Hult, Caitlin; Adalsteinsson, David; Vasquez, Paula A.; Lawrimore, Josh; Bennett, Maggie; York, Alyssa; Cook, Diana; Yeh, Elaine; Forest, Mark Gregory

2017-01-01

Abstract Regions of highly repetitive DNA, such as those found in the nucleolus, show a self-organization that is marked by spatial segregation and frequent self-interaction. The mechanisms that underlie the sequestration of these sub-domains are largely unknown. Using a stochastic, bead-spring representation of chromatin in budding yeast, we find enrichment of protein-mediated, dynamic chromosomal cross-links recapitulates the segregation, morphology and self-interaction of the nucleolus. Rates and enrichment of dynamic crosslinking have profound consequences on domain morphology. Our model demonstrates the nucleolus is phase separated from other chromatin in the nucleus and predicts that multiple rDNA loci will form a single nucleolus independent of their location within the genome. Fluorescent labeling of budding yeast nucleoli with CDC14-GFP revealed that a split rDNA locus indeed forms a single nucleolus. We propose that nuclear sub-domains, such as the nucleolus, result from phase separations within the nucleus, which are driven by the enrichment of protein-mediated, dynamic chromosomal crosslinks. PMID:28977453

Size and Content of the Sex-Determining Region of the Y Chromosome in Dioecious Mercurialis annua, a Plant with Homomorphic Sex Chromosomes.

PubMed

Veltsos, Paris; Cossard, Guillaume; Beaudoing, Emmanuel; Beydon, Genséric; Savova Bianchi, Dessislava; Roux, Camille; C González-Martínez, Santiago; R Pannell, John

2018-05-29

Dioecious plants vary in whether their sex chromosomes are heteromorphic or homomorphic, but even homomorphic sex chromosomes may show divergence between homologues in the non-recombining, sex-determining region (SDR). Very little is known about the SDR of these species, which might represent particularly early stages of sex-chromosome evolution. Here, we assess the size and content of the SDR of the diploid dioecious herb Mercurialis annua , a species with homomorphic sex chromosomes and mild Y-chromosome degeneration. We used RNA sequencing (RNAseq) to identify new Y-linked markers for M. annua. Twelve of 24 transcripts showing male-specific expression in a previous experiment could be amplified by polymerase chain reaction (PCR) only from males, and are thus likely to be Y-linked. Analysis of genome-capture data from multiple populations of M. annua pointed to an additional six male-limited (and thus Y-linked) sequences. We used these markers to identify and sequence 17 sex-linked bacterial artificial chromosomes (BACs), which form 11 groups of non-overlapping sequences, covering a total sequence length of about 1.5 Mb. Content analysis of this region suggests that it is enriched for repeats, has low gene density, and contains few candidate sex-determining genes. The BACs map to a subset of the sex-linked region of the genetic map, which we estimate to be at least 14.5 Mb. This is substantially larger than estimates for other dioecious plants with homomorphic sex chromosomes, both in absolute terms and relative to their genome sizes. Our data provide a rare, high-resolution view of the homomorphic Y chromosome of a dioecious plant.

Resolution and evolution of the duck-billed platypus karyotype with an X1Y1X2Y2X3Y3X4Y4X5Y5 male sex chromosome constitution

PubMed Central

Rens, Willem; Grützner, Frank; O'Brien, Patricia C. M.; Fairclough, Helen; Graves, Jennifer A. M.; Ferguson-Smith, Malcolm A.

2004-01-01

The platypus (2n = 52) has a complex karyotype that has been controversial over the last three decades. The presence of unpaired chromosomes and an unknown sex-determining system especially has defied attempts at conventional analysis. This article reports on the preparation of chromosome-specific probes from flow-sorted chromosomes and their application in the identification and classification of all platypus chromosomes. This work reveals that the male karyotype has 21 pairs of chromosomes and 10 unpaired chromosomes (E1-E10), which are linked by short regions of homology to form a multivalent chain in meiosis. The female karyotype differs in that five of these unpaired elements (E1, E3, E5, E7, and E9) are each present in duplicate, whereas the remaining five unpaired elements (E2, E4, E6, E8, and E10) are absent. This finding indicates that sex is determined by the alternate segregation of the chain of 10 during spermatogenesis so that equal numbers of sperm bear either one of the two groups of five elements, i.e., five X and five Y chromosomes. Chromosome painting reveals that these X and Y chromosomes contain pairing (XY shared) and differential (X- or Y-specific) segments. Y differential regions must contain male-determining genes, and X differential regions should be dosage-compensated in the female. Two models for the evolution of the sex-determining system are presented. The resolution of the longstanding debate over the platypus karyotype is an important step toward the understanding of mechanisms of sex determination, dosage compensation, and karyotype evolution. PMID:15534209

Resolution and evolution of the duck-billed platypus karyotype with an X1Y1X2Y2X3Y3X4Y4X5Y5 male sex chromosome constitution.

PubMed

Rens, Willem; Grützner, Frank; O'brien, Patricia C M; Fairclough, Helen; Graves, Jennifer A M; Ferguson-Smith, Malcolm A

2004-11-16

The platypus (2n = 52) has a complex karyotype that has been controversial over the last three decades. The presence of unpaired chromosomes and an unknown sex-determining system especially has defied attempts at conventional analysis. This article reports on the preparation of chromosome-specific probes from flow-sorted chromosomes and their application in the identification and classification of all platypus chromosomes. This work reveals that the male karyotype has 21 pairs of chromosomes and 10 unpaired chromosomes (E1-E10), which are linked by short regions of homology to form a multivalent chain in meiosis. The female karyotype differs in that five of these unpaired elements (E1, E3, E5, E7, and E9) are each present in duplicate, whereas the remaining five unpaired elements (E2, E4, E6, E8, and E10) are absent. This finding indicates that sex is determined by the alternate segregation of the chain of 10 during spermatogenesis so that equal numbers of sperm bear either one of the two groups of five elements, i.e., five X and five Y chromosomes. Chromosome painting reveals that these X and Y chromosomes contain pairing (XY shared) and differential (X- or Y-specific) segments. Y differential regions must contain male-determining genes, and X differential regions should be dosage-compensated in the female. Two models for the evolution of the sex-determining system are presented. The resolution of the longstanding debate over the platypus karyotype is an important step toward the understanding of mechanisms of sex determination, dosage compensation, and karyotype evolution.

Exclusion of chromosome 1q21-q31 from linkage to three pedigrees affected by the pigment-dispersion syndrome

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paglinauan, C.; Haines, J.L.; Del Bono, E.A.

1995-05-01

The pigment-dispersion syndrome is a form of open-angle glaucoma that usually affects individuals in the first 3 decades of life. In addition to the typical optic-nerve degeneration seen in all types of glaucoma, the pigment-dispersion syndrome is characterized by distinctive clinical features including the deposition of pigment granules from the iris epithelium on a variety of ocular structures including the trabecular meshwork. Frequently this disorder affects young myopic individuals. In the early stages of the disease, affected individuals may have clinical evidence of dispersed pigment without an associated elevation of intraocular pressure and optic-nerve degeneration. However, as the disease processmore » progresses, many affected individuals ({approximately}50%) will develop elevated intraocular pressure and degeneration of the optic nerve, causing a permanent loss of sight. The pigment-dispersion syndrome shares several clinical features with the form of autosomal dominant juvenile open-angle glaucoma that recently has been mapped to the 1q21-q31 region of chromosome 1. Our results indicate that the pigment-dispersion syndrome, a form of glaucoma that may also affect the juvenile population, is genetically unrelated to the autosomal dominant form of juvenile glaucoma caused by a defect in a gene located in the 1q21-q31 region of chromosome 1. 15 refs., 2 figs., 1 tab.« less

Condensin II mutation causes T-cell lymphoma through tissue-specific genome instability

PubMed Central

Woodward, Jessica; Taylor, Gillian C.; Soares, Dinesh C.; Boyle, Shelagh; Sie, Daoud; Read, David; Chathoth, Keerthi; Vukovic, Milica; Tarrats, Nuria; Jamieson, David; Campbell, Kirsteen J.; Blyth, Karen; Acosta, Juan Carlos; Ylstra, Bauke; Arends, Mark J.; Kranc, Kamil R.; Jackson, Andrew P.; Bickmore, Wendy A.

2016-01-01

Chromosomal instability is a hallmark of cancer, but mitotic regulators are rarely mutated in tumors. Mutations in the condensin complexes, which restructure chromosomes to facilitate segregation during mitosis, are significantly enriched in cancer genomes, but experimental evidence implicating condensin dysfunction in tumorigenesis is lacking. We report that mice inheriting missense mutations in a condensin II subunit (Caph2nes) develop T-cell lymphoma. Before tumors develop, we found that the same Caph2 mutation impairs ploidy maintenance to a different extent in different hematopoietic cell types, with ploidy most severely perturbed at the CD4+CD8+ T-cell stage from which tumors initiate. Premalignant CD4+CD8+ T cells show persistent catenations during chromosome segregation, triggering DNA damage in diploid daughter cells and elevated ploidy. Genome sequencing revealed that Caph2 single-mutant tumors are near diploid but carry deletions spanning tumor suppressor genes, whereas P53 inactivation allowed Caph2 mutant cells with whole-chromosome gains and structural rearrangements to form highly aggressive disease. Together, our data challenge the view that mitotic chromosome formation is an invariant process during development and provide evidence that defective mitotic chromosome structure can promote tumorigenesis. PMID:27737961

Low rate of interchromosomal rearrangements during old radiation of gekkotan lizards (Squamata: Gekkota).

PubMed

Johnson Pokorná, Martina; Trifonov, Vladimir A; Rens, Willem; Ferguson-Smith, Malcolm A; Kratochvíl, Lukáš

2015-06-01

Gekkotan lizards are a highly specious (∼1600 described species) clade of squamate lizards with nearly cosmopolitan distribution in warmer areas. The clade is primarily nocturnal and forms an ecologically dominant part of the world nocturnal herpetofauna. However, molecular cytogenetic methods to study the evolution of karyotypes have not been widely applied in geckos. Our aim here was to uncover the extent of chromosomal rearrangements across the whole group Gekkota and to search for putative synapomorphies supporting the newly proposed phylogenetic relationships within this clade. We applied cross-species chromosome painting with the recently derived whole-chromosomal probes from the gekkonid species Gekko japonicus to members of the major gekkotan lineages. We included members of the families Diplodactylidae, Carphodactylidae, Pygopodidae, Eublepharidae, Phyllodactylidae and Gekkonidae. Our study demonstrates relatively high chromosome conservatism across the ancient group of gekkotan lizards. We documented that many changes in chromosomal shape across geckos can be attributed to intrachromosomal rearrangements. The documented rearrangements are not totally in agreement with the recently newly erected family Phyllodactylidae. The results also pointed to homoplasy, particularly in the reuse of chromosome breakpoints, in the evolution of gecko karyotypes.

Transcription of highly repetitive tandemly organized DNA in amphibians and birds: A historical overview and modern concepts.

PubMed

Trofimova, Irina; Krasikova, Alla

2016-12-01

Tandemly organized highly repetitive DNA sequences are crucial structural and functional elements of eukaryotic genomes. Despite extensive evidence, satellite DNA remains an enigmatic part of the eukaryotic genome, with biological role and significance of tandem repeat transcripts remaining rather obscure. Data on tandem repeats transcription in amphibian and avian model organisms is fragmentary despite their genomes being thoroughly characterized. Review systematically covers historical and modern data on transcription of amphibian and avian satellite DNA in somatic cells and during meiosis when chromosomes acquire special lampbrush form. We highlight how transcription of tandemly repetitive DNA sequences is organized in interphase nucleus and on lampbrush chromosomes. We offer LTR-activation hypotheses of widespread satellite DNA transcription initiation during oogenesis. Recent explanations are provided for the significance of high-yield production of non-coding RNA derived from tandemly organized highly repetitive DNA. In many cases the data on the transcription of satellite DNA can be extrapolated from lampbrush chromosomes to interphase chromosomes. Lampbrush chromosomes with applied novel technical approaches such as superresolution imaging, chromosome microdissection followed by high-throughput sequencing, dynamic observation in life-like conditions provide amazing opportunities for investigation mechanisms of the satellite DNA transcription.

Transcription of highly repetitive tandemly organized DNA in amphibians and birds: A historical overview and modern concepts

PubMed Central

Krasikova, Alla

2016-01-01

ABSTRACT Tandemly organized highly repetitive DNA sequences are crucial structural and functional elements of eukaryotic genomes. Despite extensive evidence, satellite DNA remains an enigmatic part of the eukaryotic genome, with biological role and significance of tandem repeat transcripts remaining rather obscure. Data on tandem repeats transcription in amphibian and avian model organisms is fragmentary despite their genomes being thoroughly characterized. Review systematically covers historical and modern data on transcription of amphibian and avian satellite DNA in somatic cells and during meiosis when chromosomes acquire special lampbrush form. We highlight how transcription of tandemly repetitive DNA sequences is organized in interphase nucleus and on lampbrush chromosomes. We offer LTR-activation hypotheses of widespread satellite DNA transcription initiation during oogenesis. Recent explanations are provided for the significance of high-yield production of non-coding RNA derived from tandemly organized highly repetitive DNA. In many cases the data on the transcription of satellite DNA can be extrapolated from lampbrush chromosomes to interphase chromosomes. Lampbrush chromosomes with applied novel technical approaches such as superresolution imaging, chromosome microdissection followed by high-throughput sequencing, dynamic observation in life-like conditions provide amazing opportunities for investigation mechanisms of the satellite DNA transcription. PMID:27763817

cDNA cloning, tissue distribution, and chromosomal localization of myelodysplasia/myeloid leukemia factor 2 (MLF2).

PubMed

Kuefer, M U; Look, A T; Williams, D C; Valentine, V; Naeve, C W; Behm, F G; Mullersman, J E; Yoneda-Kato, N; Montgomery, K; Kucherlapati, R; Morris, S W

1996-07-15

A fusion gene between nucleophosmin (NPM) and myelodysplasia/myeloid leukemia factor 1 (MLF1) is formed by a recurrent t(3;5)(q25.1;q34) in myelodysplastic syndrome and acute myeloid leukemia. Here we report the identification of a novel gene, MLF2, which contains an open reading frame of 744 bp encoding a 248-amino-acid protein highly related to the previously identified MLF1 protein (63% similarity, 40% identity). In contrast to the tissue-restricted expression pattern of MLF1, the MLF2 messenger RNA is expressed ubiquitously. The MLF2 gene locus was mapped by fluorescence in situ hybridization to human chromosome 12p13, a chromosomal region frequently involved in translocations and deletions in acute leukemias of lymphoid or myeloid lineage. In a physical map of chromosome 12, MLF2 was found to reside on the yeast artificial chromosome clone 765b9. Southern blotting analysis of malignant cell DNAs prepared from a series of acute lymphoblastic leukemia cases with translocations involving chromosome arm 12p, as well as a group of acute myeloid leukemias with various cytogenetic abnormalities, failed to reveal MLF2 gene rearrangements.

Nuclear Architecture of Mouse Spermatocytes: Chromosome Topology, Heterochromatin, and Nucleolus.

PubMed

Berrios, Soledad

2017-01-01

The nuclear organization of spermatocytes in meiotic prophase I is primarily determined by the synaptic organization of the bivalents that are bound by their telomeres to the nuclear envelope and described as arc-shaped trajectories through the 3D nuclear space. However, over this basic meiotic organization, a spermatocyte nuclear architecture arises that is based on higher-ordered patterns of spatial associations among chromosomal domains from different bivalents that are conditioned by the individual characteristics of chromosomes and the opportunity for interactions between their domains. Consequently, the nuclear architecture is species-specific and prone to modification by chromosomal rearrangements. This model is valid for the localization of any chromosomal domain in the meiotic prophase nucleus. However, constitutive heterochromatin plays a leading role in shaping nuclear territories. Thus, the nuclear localization of nucleoli depends on the position of NORs in nucleolar bivalents, but the association among nucleolar chromosomes mainly depends on the presence of constitutive heterochromatin that does not affect the expression of the ribosomal genes. Constitutive heterochromatin and nucleoli form complex nuclear territories whose distribution in the nuclear space is nonrandom, supporting the hypothesis regarding the existence of a species-specific nuclear architecture in first meiotic prophase spermatocytes. © 2017 S. Karger AG, Basel.

De novo balanced complex chromosome rearrangements involving chromosomes 1B and 3B of wheat and 1R of rye.

PubMed

Ren, Tianheng; Li, Zhi; Yan, Benju; Tan, Feiquan; Tang, Zongxiang; Fu, Shulan; Yang, Manyu; Ren, Zhenglong

2016-12-01

Complex chromosome rearrangements (CCRs) are defined as structural abnormalities involving more than two chromosome breaks, coupled with exchanges of chromosomal segments. Information on CCRs in plants is limited. In the present study, a plant (26-4) harboring translocation chromosomes 1RS.1BL and 4RS.4DL was selected from a double monosomic (1R and 4R) addition line, which was derived from the hybrid between wheat cultivar MY11 and a Chinese local rye variety. The genome of the plant with double alien translocation chromosomes in the monosomic form showed more instability than that harboring a single translocation. The CCRs involving chromosomes 1RS.1BL and 3B, which were generated de novo in this plant, showed double monosomic translocation chromosomes. A new CCR line with balanced reciprocal translocations 1RS.3BL and 3BS.1BL was developed, which presented normal morphological traits of wheat and underwent rapid growth in the field. A new 1RS.1BL translocation line was also selected from the progeny of plant 26-4. The CCRs and simple 1RS.1BL translocation lines showed significant improvement in grain yield, number of spikes per square meter, kernel number per spike, and resistance to stripe rust and powdery mildew. The CCR line exhibited better agronomic traits and adult plant resistance in the field than its sister line, which harbored a simple 1RS.1BL translocation. The CCRs are remarkable genetic resources for crop improvement.

Location of RAD51-like protein during meiotic prophase in Eimeria tenella.

PubMed

Del Cacho, Emilio; Gallego, Margarita; Pagés, Marc; Barbero, José Luís; Monteagudo, Luís; Sánchez-Acedo, Caridad

2011-05-31

This study focuses on reporting events in Eimeria tenella oocysts from early to late prophase I in terms of RAD51 protein in association with the synaptonemal complex formed between homologous chromosomes. The aim of the study was the sequential localization of RAD51 protein, which is involved in the repair of double-strand breaks (DSBs) on the eimerian chromosomes as they synapse and desynapse. Structural Maintenance of Chromosome protein SMC3, which plays a role in synaptonemal complex formation, was labeled to identify initiation and progress of chromosome synapsis and desynapsis in parallel with the appearance and disappearance of RAD51 foci. Antibodies directed against RAD51 and cohesin subunit SMC3 proteins were labeled with either fluorescence or colloidal gold to visualize RAD51 protein foci and synaptonemal complexes. RAD51 protein localization during prophase I was studied on meiotic chromosomes spreads obtained from oocysts at different points in time after the start of sporulation. The present findings showed that foci detected with the antibody directed against RAD51 protein first appeared at the pre-leptotene stage before homologous chromosomes began pairing. Subsequently, the foci were detected in association with the lateral elements at the precise sites where synapsis were in progress. These findings lead us to suggest that in E. tenella, homologous chromosome pairing was a DSB-dependent mechanism and reinforced the participation of RAD51 protein in meiotic homology search, alignment and pairing of chromosomes. Copyright © 2010 Elsevier B.V. All rights reserved.

The TP53 dependence of radiation-induced chromosome instability in human lymphoblastoid cells

NASA Technical Reports Server (NTRS)

Schwartz, Jeffrey L.; Jordan, Robert; Evans, Helen H.; Lenarczyk, Marek; Liber, Howard

2003-01-01

The dose and TP53 dependence for the induction of chromosome instability were examined in cells of three human lymphoblastoid cell lines derived from WIL2 cells: TK6, a TP53-normal cell line, NH32, a TP53-knockout created from TK6, and WTK1, a WIL2-derived cell line that spontaneously developed a TP53 mutation. Cells of each cell line were exposed to (137)Cs gamma rays, and then surviving clones were isolated and expanded in culture for approximately 35 generations before the frequency and characteristics of the instability were analyzed. The presence of dicentric chromosomes, formed by end-to-end fusions, served as a marker of chromosomal instability. Unexposed TK6 cells had low levels of chromosomal instability (0.002 +/- 0.001 dicentrics/cell). Exposure of TK6 cells to doses as low as 5 cGy gamma rays increased chromosome instability levels nearly 10-fold to 0.019 +/- 0.008 dicentrics/cell. There was no further increase in instability levels beyond 5 cGy. In contrast to TK6 cells, unexposed cultures of WTK1 and NH32 cells had much higher levels of chromosome instability of 0.034 +/- 0.007 and 0.041 +/- 0.009, respectively, but showed little if any effect of radiation on levels of chromosome instability. The results suggest that radiation exposure alters the normal TP53-dependent cell cycle checkpoint controls that recognize alterations in telomere structure and activate apoptosis.

Polyploidy is genetic hence may cause non-adaptive radiations, whereas pseudopolyploidy is genomic hence may cause adaptive non-radiations.

PubMed

Gorelick, Root; Olson, Krystle

2013-07-01

There are two ways eukaryotes double number of chromosomes: (1) whole genome duplication (polyploidy), in which all nuclear DNA is replicated, and (2) karyotypic fission (pseudopolyploidy), in which all chromosomes are physically bifurcated. We contrast polyploidy with pseudopolyploidy, highlighting when it is crucial to look at genetic vs. genomic levels. We review history of pseudopolyploidy, including recent mechanisms by which chromosomal bifurcation may occur and outline methods for detecting such genomic changes. We then delve into the evolutionary implications, with particular focus on adaptive potential, of these two forms of doubling chromosome numbers. We address the common assertion that polyploidy induces adaptive radiations, which contains three fallacies. First, while polyploidy causes quantum speciation, evolutionary theory implies that these radiations should be non-adaptive. Polyploidy causes reproductive isolation, minute effective population sizes, and increased mutation rates, which all imply a diminished role for selection. Second, due to lack of karyotyping in recent decades and lack of distinction between genomic and genetic effects, it is usually impossible to detect pseudopolyploids. Third, pseudopolyploids lack minority cytotype exclusion because they readily backcross with their progenitors, which thereby means no reproductive isolation for newly formed pseudopolyploids. Pseudopolyploidy will thereby not result in radiations until pseudopolyploid descendants undergo subsequent chromosome rearrangements or grow new centromeres. Pseudopolyploids may have a modest selective advantage over their progenitors due to diminished linkage disequilibrium. Thus, pseudopolyploidy may induce adaptive non-radiations. We encourage a renaissance of karyotyping to distinguish between these two mechanisms and a renaissance in genomic perspectives in evolution. Copyright © 2013 Wiley Periodicals, Inc.

Defective pairing and synaptonemal complex formation in a Sordaria mutant (spo44) with a translocated segment of the nucleolar organizer.

PubMed

Zickler, D; de Lares, L; Moreau, P J; Leblon, G

1985-01-01

The recessive meiotic mutant spo44 of Sordaria macrospora, with 90% ascospore abortion, exhibits striking effects on recombination (67% decrease), irregular segregation of the almost unpaired homologues, and a decrease in chiasma frequency in the few cases where bivalents are formed. Three-dimensional reconstructions of ten prophase nuclei indicate that pairing, as judged by the absence of fully formed synaptonemal complexes (SC), is not achieved although lateral elements (LE) assemble. The pairing failure is attributable to defects in the alignment of homologous chromosomes. The leptotene alignment seen in the wild type before SC formation was not observed in the spo44 nuclei. Dense material, considered to be precursor of SC central elements, was found scattered among the LE in two nuclei. The behaviour of spo44 substantiates the hypothesis that chromosome matching and SC formation are separable events. - The total length of the LE in the mutant is the same as in the wild type, but due to variable numbers and length of the individual LE, homologues cannot be lined up. Light microscopic observations indicate that the irregular length and number of LE is due to extensive chromosome breakage. The wild-type function corresponding to spo44 is required for both LE integrity and chromosome matching. Reconstructions of heterozygous nuclei reveal the presence of a supernumerary nucleolar organizer in one arm of chromosome 7. It is suggested that rDNA has been inserted into a gene whose function is involved in pairing or into a controlling sequence that interacts with the pairing process.

Dynamic epigenetic states of maize centromeres

PubMed Central

Liu, Yalin; Su, Handong; Zhang, Jing; Liu, Yang; Han, Fangpu; Birchler, James A.

2015-01-01

The centromere is a specialized chromosomal region identified as the major constriction, upon which the kinetochore complex is formed, ensuring accurate chromosome orientation and segregation during cell division. The rapid evolution of centromere DNA sequence and the conserved centromere function are two contradictory aspects of centromere biology. Indeed, the sole presence of genetic sequence is not sufficient for centromere formation. Various dicentric chromosomes with one inactive centromere have been recognized. It has also been found that de novo centromere formation is common on fragments in which centromeric DNA sequences are lost. Epigenetic factors play important roles in centromeric chromatin assembly and maintenance. Non-disjunction of the supernumerary B chromosome centromere is independent of centromere function, but centromere pairing during early prophase of meiosis I requires an active centromere. This review discusses recent studies in maize about genetic and epigenetic elements regulating formation and maintenance of centromere chromatin, as well as centromere behavior in meiosis. PMID:26579154

Simulated binding of transcription factors to active and inactive regions folds human chromosomes into loops, rosettes and topological domains

PubMed Central

Brackley, Chris A.; Johnson, James; Kelly, Steven; Cook, Peter R.; Marenduzzo, Davide

2016-01-01

Biophysicists are modeling conformations of interphase chromosomes, often basing the strengths of interactions between segments distant on the genetic map on contact frequencies determined experimentally. Here, instead, we develop a fitting-free, minimal model: bivalent or multivalent red and green ‘transcription factors’ bind to cognate sites in strings of beads (‘chromatin’) to form molecular bridges stabilizing loops. In the absence of additional explicit forces, molecular dynamic simulations reveal that bound factors spontaneously cluster—red with red, green with green, but rarely red with green—to give structures reminiscent of transcription factories. Binding of just two transcription factors (or proteins) to active and inactive regions of human chromosomes yields rosettes, topological domains and contact maps much like those seen experimentally. This emergent ‘bridging-induced attraction’ proves to be a robust, simple and generic force able to organize interphase chromosomes at all scales. PMID:27060145

Dynamic epigenetic states of maize centromeres.

PubMed

Liu, Yalin; Su, Handong; Zhang, Jing; Liu, Yang; Han, Fangpu; Birchler, James A

2015-01-01

The centromere is a specialized chromosomal region identified as the major constriction, upon which the kinetochore complex is formed, ensuring accurate chromosome orientation and segregation during cell division. The rapid evolution of centromere DNA sequence and the conserved centromere function are two contradictory aspects of centromere biology. Indeed, the sole presence of genetic sequence is not sufficient for centromere formation. Various dicentric chromosomes with one inactive centromere have been recognized. It has also been found that de novo centromere formation is common on fragments in which centromeric DNA sequences are lost. Epigenetic factors play important roles in centromeric chromatin assembly and maintenance. Non-disjunction of the supernumerary B chromosome centromere is independent of centromere function, but centromere pairing during early prophase of meiosis I requires an active centromere. This review discusses recent studies in maize about genetic and epigenetic elements regulating formation and maintenance of centromere chromatin, as well as centromere behavior in meiosis.

Chromothripsis and kataegis induced by telomere crisis

PubMed Central

Maciejowski, John; Li, Yilong; Bosco, Nazario; Campbell, Peter J.; de Lange, Titia

2015-01-01

Telomere crisis occurs during tumorigenesis when depletion of the telomere reserve leads to frequent telomere fusions. The resulting dicentric chromosomes have been proposed to drive genome instability. Here we examine the fate of dicentric human chromosomes in telomere crisis. We observed that dicentric chromosomes invariably persisted through mitosis and developed into 50-200 μm chromatin bridges connecting the daughter cells. Before their resolution at 3-20 h after anaphase, the chromatin bridges induced nuclear envelope rupture in interphase, accumulated the cytoplasmic 3' nuclease TREX1, and developed RPA-coated single stranded (ss) DNA. CRISPR knockouts showed that TREX1 contributed to the generation of the ssDNA and the resolution of the chromatin bridges. Post-crisis clones showed chromothripsis and kataegis, presumably resulting from DNA repair and APOBEC editing of the fragmented chromatin bridge DNA. We propose that chromothripsis in human cancer may arise through TREX1-mediated fragmentation of dicentric chromosomes formed in telomere crisis. PMID:26687355

A boy with partial dup(18q)/del(18p) due to a maternal pericentric inversion: Genotype-phenotype correlation and risk of recombinant chromosomes based on systematic review of the literature.

PubMed

Lustosa-Mendes, Elaine; Dos Santos, Ana Paula; Viguetti-Campos, Nilma Lúcia; Vieira, Társis Paiva; Gil-da-Silva-Lopes, Vera Lúcia

2017-01-01

We report a boy carrying a recombinant chromosome 18, with terminal deletion of 10.8 Mb from 18p11.32 to 18p11.21 and a terminal duplication of 22.8 Mb from 18q21.31 to 18q23, resulting from a maternal pericentric inversion of the chromosome 18. He presented with poor growth, developmental delay, facial dysmorphisms, surgically repaired left cleft lip and palate, a mild form of holoprosencephaly characterized by single central incisor and agenesis of the septum pellucidum, and body asymmetry. Based on the systematic review of the literature, we discuss genotype-phenotype correlation and the risk for the recombinants of pericentric inversions of chromosome 18. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Chromosome and mitotic spindle dynamics in fission yeast kinesin-8 mutants

NASA Astrophysics Data System (ADS)

Crapo, Ammon M.; Gergley, Zachary R.; McIntosh, J. Richard; Betterton, M. D.

2014-03-01

Fission yeast proteins Klp5p and Klp6p are plus-end directed motors of the kinesin-8 family which promote microtubule (MT) depolymerization and also affect chromosome segregation, but the mechanism of these activities is not well understood. Using live-cell time-lapse fluorescence microscopy of fission yeast wild-type (WT) and klp5/6 mutant strains, we quantify and compare the dynamics of kinetochore motion and mitotic spindle length in 3D. In WT cells, the spindle, once formed, remains a consistent size and chromosomes are correctly organized and segregated. In kinesin-8 mutants, spindles undergo large length fluctuations of several microns. Kinetochore motions are also highly fluctuating, with kinetochores frequently moving away from the spindle rather than toward it. We observe transient pushing of chromosomes away from the spindle by as much as 10 microns in distance.

Chromosomal localization and sequence analysis of a human episomal sequence with in vitro differentiating activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boccaccio, C.; Deshatrette, J.; Meunier-Rotival, M.

1994-05-01

The genomic fragment carrying the human activator of liver function, previously described as an episome capable of inducing differentiation upon transfection into a dedifferentiated rat hepatoma cell line, was mapped on human chromosome 12q24.2-12q24.3. This chromosomal location was indistinguishable by in situ hybridization from that of the gene coding for the hepatic transcription factor HNF1. The sequence of the integrated form of the episome as well as its flanking sequences show that it is rich in retroposons. It contains a human ribosomal protein L21 processed pseudogene, one truncated L1Hs sequence, and 10 Alu repeats, which belong to different subfamilies.

Chromosome Evolution in the Free-Living Flatworms: First Evidence of Intrachromosomal Rearrangements in Karyotype Evolution of Macrostomum lignano (Platyhelminthes, Macrostomida)

PubMed Central

Zadesenets, Kira S.; Ershov, Nikita I.; Berezikov, Eugene; Rubtsov, Nikolay B.

2017-01-01

The free-living flatworm Macrostomum lignano is a hidden tetraploid. Its genome was formed by a recent whole genome duplication followed by chromosome fusions. Its karyotype (2n = 8) consists of a pair of large chromosomes (MLI1), which contain regions of all other chromosomes, and three pairs of small metacentric chromosomes. Comparison of MLI1 with metacentrics was performed by painting with microdissected DNA probes and fluorescent in situ hybridization of unique DNA fragments. Regions of MLI1 homologous to small metacentrics appeared to be contiguous. Besides the loss of DNA repeat clusters (pericentromeric and telomeric repeats and the 5S rDNA cluster) from MLI1, the difference between small metacentrics MLI2 and MLI4 and regions homologous to them in MLI1 were revealed. Abnormal karyotypes found in the inbred DV1/10 subline were analyzed, and structurally rearranged chromosomes were described with the painting technique, suggesting the mechanism of their origin. The revealed chromosomal rearrangements generate additional diversity, opening the way toward massive loss of duplicated genes from a duplicated genome. Our findings suggest that the karyotype of M. lignano is in the early stage of genome diploidization after whole genome duplication, and further studies on M. lignano and closely related species can address many questions about karyotype evolution in animals. PMID:29084138

Telomeres and NextGen CO-FISH: Directional Genomic Hybridization (Telo-dGH™).

PubMed

McKenna, Miles J; Robinson, Erin; Goodwin, Edwin H; Cornforth, Michael N; Bailey, Susan M

2017-01-01

The cytogenomics-based methodology of Directional Genomic Hybridization (dGH™) emerged from the concept of strand-specific hybridization, first made possible by Chromosome Orientation FISH (CO-FISH), the utility of which was demonstrated in a variety of early applications, often involving telomeres. Similar to standard whole chromosome painting (FISH), dGH™ is capable of identifying inter-chromosomal rearrangements (translocations between chromosomes), but its distinctive strength stems from its ability to detect intra-chromosomal rearrangements (inversions within chromosomes), and to do so at higher resolution than previously possible. dGH™ brings together the strand specificity and directionality of CO-FISH with sophisticated bioinformatics-based oligonucleotide probe design to unique sequences. dGH™ serves not only as a powerful discovery tool-capable of interrogating the entire genome at the megabase level-it can also be used for high-resolution targeted detection of known inversions, a valuable attribute in both research and clinical settings. Detection of chromosomal inversions, particularly small ones, poses a formidable challenge for more traditional cytogenetic approaches, especially when they occur near the ends or telomeric regions. Here, we describe Telo-dGH™, a strand-specific scheme that utilizes dGH™ in combination with telomere CO-FISH to differentiate between terminal exchange events, specifically terminal inversions, and an altogether different form of genetic recombination that often occurs near the telomere, namely sister chromatid exchange (SCE).

Nonhomologous Pairing in Mice Heterozygous for a t Haplotype Can Produce Recombinant Chromosomes with Duplications and Deletions

PubMed Central

Sarvetnick, Nora; Fox, Howard S.; Mann, Elizabeth; Mains, Paul E.; Elliott, Rosemary W.; Silver, Lee M.

1986-01-01

We have investigated the structure and properties of a chromosomal product recovered from a rare recombination event between a t haplotype and a wild-type form of mouse chromosome 17. Our embryological and molecular studies indicate that this chromosome (twLub2 ) is characterized by both a deletion and duplication of adjacent genetic material. The deletion appears to be responsible for a dominant lethal maternal effect and a recessive embryonic lethality. The duplication provides an explanation for the twLub2 suppression of the dominant T locus phenotype. A reanalysis of previously described results with another chromosome 17 variant called TtOrl indicates a structure for this chromosome that is reciprocal to that observed for twLub2. We have postulated the existence of an inversion over the proximal portion of all complete t haplotypes in order to explain the generation of the partial t haplotypes t wLub2 and TtOrl. This proximal inversion and the previously described distal inversion are sufficient to account for all of the recombination properties that are characteristic of complete t haplotypes. The structures determined for twLub2 and TtOrl indicate that rare recombination can occur between nonequivalent genomic sequences within the inverted proximal t region when wild-type and t chromosomes are paired in a linear, nonhomologous configuration. PMID:3732789

Rescue of Targeted Regions of Mammalian Chromosomes by in Vivo Recombination in Yeast

PubMed Central

Kouprina, Natalya; Kawamoto, Kensaku; Barrett, J. Carl; Larionov, Vladimir; Koi, Minoru

1998-01-01

In contrast to other animal cell lines, the chicken pre-B cell lymphoma line, DT40, exhibits a high level of homologous recombination, which can be exploited to generate site-specific alterations in defined target genes or regions. In addition, the ability to generate human/chicken monochromosomal hybrids in the DT40 cell line opens a way for specific targeting of human genes. Here we describe a new strategy for direct isolation of a human chromosomal region that is based on targeting of the chromosome with a vector containing a yeast selectable marker, centromere, and an ARS element. This procedure allows rescue of the targeted region by transfection of total genomic DNA into yeast spheroplasts. Selection for the yeast marker results in isolation of chromosome sequences in the form of large circular yeast artificial chromosomes (YACs) up to 170 kb in size containing the targeted region. These YACs are generated by homologous recombination in yeast between common repeated sequences in the targeted chromosomal fragment. Alternatively, the targeted region can be rescued as a linear YACs when a YAC fragmentation vector is included in the yeast transformation mixture. Because the entire isolation procedure of the chromosomal region, once a target insertion is obtained, can be accomplished in ∼1 week, the new method greatly expands the utility of the homologous recombinationproficient DT40 chicken cell system. PMID:9647640

Distinct classical and molecular cytogenetics of Astyanax marionae and A. fasciatus (Characiformes: Characidae): a comparative study of the organization of heterochromatin and repetitive genes.

PubMed

Piscor, Diovani; Centofante, Liano; Parise-Maltempi, Patricia Pasquali

2017-09-01

Genus Astyanax is well distributed in Neotropical freshwater environments and its taxonomic position is uncertain, as is the case with other Characidae genera allocated in the group incertae sedis. This study aimed to analyse the karyotype of different populations of Astyanax fasciatus (Corumbataí River basin) using Giemsa staining, C-band technique, and fluorescence in situ hybridization for the H3 histone and 5S rRNA genes, in addition we describe for the first time the chromosomal organization of H3 histone and 5S rRNAgenes in A. marionae (ParaguayRiver basin). Chromosomes of three A. fasciatus populations were analysed (two with 2n = 50 and one with 2n = 48) and the heterochromatin was organized in two forms (blocks with blurred boundaries and distinct blocks). H3 histone and 5S rRNA genes were observed in all the three populations of A. fasciatus on two chromosome pairs (one metacentric chromosome showing H3 histone and 5S rRNA gene clusters). In A. marionae (2n = 48), H3 histone and 5S rRNA genes were observed in one acrocentric chromosome pair (different pairs). Further, differences between karyotypes and heterochromatin, as well as the chromosomal organization of H3 histone and 5S rRNA genes in Astyanax species, focussing on chromosome evolution in the group are discussed.

Physical constraints in the condensation of eukaryotic chromosomes. Local concentration of DNA versus linear packing ratio in higher order chromatin structures.

PubMed

Daban, J R

2000-04-11

The local concentration of DNA in metaphase chromosomes of different organisms has been determined in several laboratories. The average of these measurements is 0.17 g/mL. In the first level of chromosome condensation, DNA is wrapped around histones forming nucleosomes. This organization limits the DNA concentration in nucleosomes to 0. 3-0.4 g/mL. Furthermore, in the structural models suggested in different laboratories for the 30-40 nm chromatin fiber, the estimated DNA concentration is significantly reduced; it ranges from 0.04 to 0.27 g/mL. The DNA concentration is further reduced when the fiber is folded into the successive higher order structures suggested in different models for metaphase chromosomes; the estimated minimum decrease of DNA concentration represents an additional 40%. These observations suggest that most of the models proposed for the 30-40 nm chromatin fiber are not dense enough for the construction of metaphase chromosomes. In contrast, it is well-known that the linear packing ratio increases dramatically in each level of DNA folding in chromosomes. Thus, the consideration of the linear packing ratio is not enough for the study of chromatin condensation; the constraint resulting from the actual DNA concentration in metaphase chromosomes must be considered for the construction of models for condensed chromatin.

Phenotypic interpretation of complex chromosomal rearrangements informed by nucleotide-level resolution and structural organization of chromatin.

PubMed

Zepeda-Mendoza, Cinthya J; Bardon, Alexandra; Kammin, Tammy; Harris, David J; Cox, Helen; Redin, Claire; Ordulu, Zehra; Talkowski, Michael E; Morton, Cynthia C

2018-03-01

Molecular characterization of balanced chromosomal abnormalities constitutes a powerful tool in understanding the pathogenic mechanisms of complex genetic disorders. Here we report a male with severe global developmental delay in the presence of a complex karyotype and normal microarray and exome studies. The subject, referred to as DGAP294, has two de novo apparently balanced translocations involving chromosomes 1 and 14, and chromosomes 4 and 10, disrupting several different transcripts of adhesion G protein-coupled receptor L2 (ADGRL2) and protocadherin 15 (PCDH15). In addition, a maternally inherited inversion disrupts peptidyl arginine deiminase types 3 and 4 (PADI3 and PADI4) on chromosome 1. None of these gene disruptions explain the patient's phenotype. Using genome regulatory annotations and chromosome conformation data, we predict a position effect ~370 kb upstream of a translocation breakpoint located at 14q12. The position effect involves forkhead box G1 (FOXG1), mutations in which are associated with the congenital form of Rett syndrome and FOXG1 syndrome. We believe the FOXG1 position effect largely accounts for the clinical phenotype in DGAP294, which can be classified as FOXG1 syndrome like. Our findings emphasize the significance of not only analyzing disrupted genes by chromosomal rearrangements, but also evaluating potential long-range position effects in clinical diagnoses.

One pedigree we all may have come from - did Adam and Eve have the chromosome 2 fusion?

PubMed

Stankiewicz, Paweł

2016-01-01

In contrast to Great Apes, who have 48 chromosomes, modern humans and likely Neandertals and Denisovans have and had, respectively, 46 chromosomes. The reduction in chromosome number was caused by the head-to-head fusion of two ancestral chromosomes to form human chromosome 2 (HSA2) and may have contributed to the reproductive barrier with Great Apes. Next generation sequencing and molecular clock analyses estimated that this fusion arose prior to our last common ancestor with Neandertal and Denisovan hominins ~ 0.74 - 4.5 million years ago. I propose that, unlike recurrent Robertsonian translocations in humans, the HSA2 fusion was a single nonrecurrent event that spread through a small polygamous clan population bottleneck. Its heterozygous to homozygous conversion, fixation, and accumulation in the succeeding populations was likely facilitated by an evolutionary advantage through the genomic loss rather than deregulation of expression of the gene(s) flanking the HSA2 fusion site at 2q13. The origin of HSA2 might have been a critical evolutionary event influencing higher cognitive functions in various early subspecies of hominins. Next generation sequencing of Homo heidelbergensis and Homo erectus genomes and complete reconstruction of DNA sequence of the orthologous subtelomeric chromosomes in Great Apes should enable more precise timing of HSA2 formation and better understanding of its evolutionary consequences.

RNAi drives nonreciprocal translocations at eroding chromosome ends to establish telomere-free linear chromosomes.

PubMed

Begnis, Martina; Apte, Manasi S; Masuda, Hirohisa; Jain, Devanshi; Wheeler, David Lee; Cooper, Julia Promisel

2018-04-01

The identification of telomerase-negative HAATI (heterochromatin amplification-mediated and telomerase-independent) cells, in which telomeres are superseded by nontelomeric heterochromatin tracts, challenged the idea that canonical telomeres are essential for chromosome linearity and raised crucial questions as to how such tracts translocate to eroding chromosome ends and confer end protection. Here we show that HAATI arises when telomere loss triggers a newly recognized illegitimate translocation pathway that requires RNAi factors. While RNAi is necessary for the translocation events that mobilize ribosomal DNA (rDNA) tracts to all chromosome ends (forming "HAATI rDNA " chromosomes), it is dispensable for HAATI rDNA maintenance. Surprisingly, Dicer (Dcr1) plays a separate, RNAi-independent role in preventing formation of the rare HAATI subtype in which a different repetitive element (the subtelomeric element) replaces telomeres. Using genetics and fusions between shelterin components and rDNA-binding proteins, we mapped the mechanism by which rDNA loci engage crucial end protection factors-despite the absence of telomere repeats-and secure end protection. Sequence analysis of HAATI rDNA genomes allowed us to propose RNA and DNA polymerase template-switching models for the mechanism of RNAi-triggered rDNA translocations. Collectively, our results reveal unforeseen roles for noncoding RNAs (ncRNAs) in assembling a telomere-free chromosome end protection device. © 2018 Begnis et al.; Published by Cold Spring Harbor Laboratory Press.

Living at the edge: biogeographic patterns of habitat segregation conform to speciation by niche expansion in Anopheles gambiae

PubMed Central

Costantini, Carlo; Ayala, Diego; Guelbeogo, Wamdaogo M; Pombi, Marco; Some, Corentin Y; Bassole, Imael HN; Ose, Kenji; Fotsing, Jean-Marie; Sagnon, N'Falé; Fontenille, Didier; Besansky, Nora J; Simard, Frédéric

2009-01-01

Background Ongoing lineage splitting within the African malaria mosquito Anopheles gambiae is compatible with ecological speciation, the evolution of reproductive isolation by divergent natural selection acting on two populations exploiting alternative resources. Divergence between two molecular forms (M and S) identified by fixed differences in rDNA, and characterized by marked, although incomplete, reproductive isolation is occurring in West and Central Africa. To elucidate the role that ecology and geography play in speciation, we carried out a countrywide analysis of An. gambiae M and S habitat requirements, and that of their chromosomal variants, across Burkina Faso. Results Maps of relative abundance by geostatistical interpolators produced a distinct pattern of distribution: the M-form dominated in the northernmost arid zones, the S-form in the more humid southern regions. Maps of habitat suitability, quantified by Ecological Niche Factor Analysis based on 15 eco-geographical variables revealed less contrast among forms. M was peculiar as it occurred proportionally more in habitat of marginal quality. Measures of ecological niche breadth and overlap confirmed the mismatch between the fundamental and realized patterns of habitat occupation: forms segregated more than expected from the extent of divergence of their environmental envelope – a signature of niche expansion. Classification of chromosomal arm 2R karyotypes by multilocus genetic clustering identified two clusters loosely corresponding to molecular forms, with 'mismatches' representing admixed individuals due to shared ancestral polymorphism and/or residual hybridization. In multivariate ordination space, these karyotypes plotted in habitat of more marginal quality compared to non-admixed, 'typical', karyotypes. The distribution of 'typical' karyotypes along the main eco-climatic gradient followed a consistent pattern within and between forms, indicating an adaptive role of inversions at this geographical scale. Conclusion Ecological segregation between M and S is consistent with niche expansion into marginal habitats by chromosomal inversion variants during early lineage divergence; presumably, this process is promoted by inter-karyotype competition in the higher-quality core habitat. We propose that the appearance of favourable allelic combinations in other regions of suppressed recombination (e.g. pericentromeric portions defining speciation islands in An. gambiae) fosters development of reproductive isolation to protect linkage between separate chromosomal regions. PMID:19460144

Condensin-Driven Remodeling of X-Chromosome Topology during Dosage Compensation

PubMed Central

Crane, Emily; Bian, Qian; McCord, Rachel Patton; Lajoie, Bryan R.; Wheeler, Bayly S.; Ralston, Edward J.; Uzawa, Satoru; Dekker, Job; Meyer, Barbara J.

2015-01-01

The three-dimensional organization of a genome plays a critical role in regulating gene expression, yet little is known about the machinery and mechanisms that determine higher-order chromosome structure1,2. Here we perform genome-wide chromosome conformation capture analysis, FISH, and RNA-seq to obtain comprehensive 3D maps of the Caenorhabditis elegans genome and to dissect X-chromosome dosage compensation, which balances gene expression between XX hermaphrodites and XO males. The dosage compensation complex (DCC), a condensin complex, binds to both hermaphrodite X chromosomes via sequence-specific recruitment elements on X (rex sites) to reduce chromosome-wide gene expression by half3–7. Most DCC condensin subunits also act in other condensin complexes to control the compaction and resolution of all mitotic and meiotic chromosomes5,6. By comparing chromosome structure in wild-type and DCC-defective embryos, we show that the DCC remodels hermaphrodite X chromosomes into a sex-specific spatial conformation distinct from autosomes. Dosage-compensated X chromosomes consist of self-interacting domains (~1 Mb) resembling mammalian Topologically Associating Domains (TADs)8,9. TADs on X have stronger boundaries and more regular spacing than on autosomes. Many TAD boundaries on X coincide with the highest-affinity rex sites and become diminished or lost in DCC-defective mutants, thereby converting the topology of X to a conformation resembling autosomes. rex sites engage in DCC-dependent long-range interactions, with the most frequent interactions occurring between rex sites at DCC-dependent TAD boundaries. These results imply that the DCC reshapes the topology of X by forming new TAD boundaries and reinforcing weak boundaries through interactions between its highest-affinity binding sites. As this model predicts, deletion of an endogenous rex site at a DCC-dependent TAD boundary using CRISPR/Cas9 greatly diminished the boundary. Thus, the DCC imposes a distinct higher-order structure onto X while regulating gene expression chromosome wide. PMID:26030525

Somatically Acquired Isodicentric Y and Mosaic Loss of Chromosome Y in a Boy with Hypospadias.

PubMed

Miyado, Mami; Muroya, Koji; Katsumi, Momori; Saito, Kazuki; Kon, Masafumi; Fukami, Maki

2018-04-07

Isodicentric Y chromosome [idic(Y)] represents a relatively common subtype of Y chromosomal rearrangements in the germline; however, limited evidence supports the postzygotic occurrence of idic(Y). Here, we report a boy with hypospadias and somatically acquired idic(Y). The 3.5-year-old boy has been identified in our previous study for patients with hypospadias. In the present study, cytogenetic analysis including FISH revealed a 45,X[5]/46,X,idic(Y)[7]/46,XY[8] karyotype. MLPA showed a mosaic deletion involving PPP1R12BP1 and RBMY2DP. The idic(Y) was likely to have been formed through aberrant recombination between P1 palindromes and subsequently underwent mosaic loss. The patient's phenotype was attributable to deletion of some Y chromosomal genes and/or mosaic loss of chromosome Y (mLOY). The results suggest that idic(Y) can originate in postzygotic cells via palindrome-mediated crossovers. Moreover, our data indicate that somatically acquired idic(Y) can trigger mLOY, which usually appears as an aging-related phenomenon in elderly men. © 2018 S. Karger AG, Basel.

Distinct DNA methylation patterns associated with active and inactive centromeres of the maize B chromosome.

PubMed

Koo, Dal-Hoe; Han, Fangpu; Birchler, James A; Jiang, Jiming

2011-06-01

Centromeres are determined by poorly understood epigenetic mechanisms. Centromeres can be activated or inactivated without changing the underlying DNA sequences. However, virtually nothing is known about the epigenetic transition of a centromere from an active to an inactive state because of the lack of examples of the same centromere exhibiting alternative forms and being distinguishable from other centromeres. The centromere of the supernumerary B chromosome of maize provides such an opportunity because its functional core can be cytologically tracked, and an inactive version of the centromere is available. We developed a DNA fiber-based technique that can be used to assess the levels of cytosine methylation associated with repetitive DNA sequences. We report that DNA sequences in the normal B centromere exhibit hypomethylation. This methylation pattern is not affected by the genetic background or structural rearrangement of the B chromosome, but is slightly changed when the B chromosome is transferred to oat as an addition chromosome. In contrast, an inactive version of this same centromere exhibits hypermethylation, indicating that the inactive centromere was modified into a different epigenetic state at the DNA level.

Evolving Centromeres and Kinetochores.

PubMed

Friedman, Steven; Freitag, Michael

2017-01-01

The genetic material, contained on chromosomes, is often described as the "blueprint for life." During nuclear division, the chromosomes are pulled into each of the two daughter nuclei by the coordination of spindle microtubules, kinetochores, centromeres, and chromatin. These four functional units must link the chromosomes to the microtubules, signal to the cell when the attachment is made so that division can proceed, and withstand the force generated by pulling the chromosomes to either daughter cell. To perform each of these functions, kinetochores are large protein complexes, approximately 5MDa in size, and they contain at least 45 unique proteins. Many of the central components in the kinetochore are well conserved, yielding a common core of proteins forming consistent structures. However, many of the peripheral subcomplexes vary between different taxonomic groups, including changes in primary sequence and gain or loss of whole proteins. It is still unclear how significant these changes are, and answers to this question may provide insights into adaptation to specific lifestyles or progression of disease that involve chromosome instability. Copyright © 2017 Elsevier Inc. All rights reserved.

The spindle protein CHICA mediates localization of the chromokinesin Kid to the mitotic spindle.

PubMed

Santamaria, Anna; Nagel, Susanna; Sillje, Herman H W; Nigg, Erich A

2008-05-20

Microtubule-based motor proteins provide essential forces for bipolar organization of spindle microtubules and chromosome movement, prerequisites of chromosome segregation during the cell cycle. Here, we describe the functional characterization of a novel spindle protein, termed "CHICA," that was originally identified in a proteomic survey of the human spindle apparatus [1]. We show that CHICA localizes to the mitotic spindle and is both upregulated and phosphorylated during mitosis. CHICA-depleted cells form shorter spindles and fail to organize a proper metaphase plate, highly reminiscent of the phenotype observed upon depletion of the chromokinesin Kid, a key mediator of polar ejection forces [2-6]. We further show that CHICA coimmunoprecipitates with Kid and is required for the spindle localization of Kid without affecting its chromosome association. Moreover, upon depletion of either CHICA or Kid (or both proteins simultaneously), chromosomes collapse onto the poles of monastrol-induced monopolar spindles. We conclude that CHICA represents a novel interaction partner of the chromokinesin Kid that is required for the generation of polar ejection forces and chromosome congression.

TRAMM/TrappC12 plays a role in chromosome congression, kinetochore stability, and CENP-E recruitment

PubMed Central

Milev, Miroslav P.; Hasaj, Benedeta; Saint-Dic, Djenann; Snounou, Sary; Zhao, Qingchuan

2015-01-01

Chromosome congression requires the stable attachment of microtubules to chromosomes mediated by the kinetochore, a large proteinaceous structure whose mechanism of assembly is unknown. In this paper, we present the finding that a protein called TRAMM (formerly known as TrappC12) plays a role in mitosis. Depletion of TRAMM resulted in noncongressed chromosomes and arrested cells in mitosis. Small amounts of TRAMM associated with chromosomes, and its depletion affected the localization of some kinetochore proteins, the strongest effect being seen for CENP-E. TRAMM interacts with CENP-E, and depletion of TRAMM prevented the recruitment of CENP-E to the kinetochore. TRAMM is phosphorylated early in mitosis and dephosphorylated at the onset of anaphase. Interestingly, this phosphorylation/dephosphorylation cycle correlates with its association/disassociation with CENP-E. Finally, we demonstrate that a phosphomimetic form of TRAMM recruited CENP-E to kinetochores more efficiently than did the nonphosphorylatable mutant. Our study identifies a moonlighting function for TRAMM during mitosis and adds a new component that regulates kinetochore stability and CENP-E recruitment. PMID:25918224

Simulation of DNA Damage in Human Cells from Space Radiation Using a Physical Model of Stochastic Particle Tracks and Chromosomes

NASA Technical Reports Server (NTRS)

Ponomarev, Artem; Plante, Ianik; Hada, Megumi; George, Kerry; Wu, Honglu

2015-01-01

The formation of double-strand breaks (DSBs) and chromosomal aberrations (CAs) is of great importance in radiation research and, specifically, in space applications. We are presenting a recently developed model, in which chromosomes simulated by NASARTI (NASA Radiation Tracks Image) is combined with nanoscopic dose calculations performed with the Monte-Carlo simulation by RITRACKS (Relativistic Ion Tracks) in a voxelized space. The model produces the number of DSBs, as a function of dose for high-energy iron, oxygen, and carbon ions, and He ions. The combined model calculates yields of radiation-induced CAs and unrejoined chromosome breaks in normal and repair deficient cells. The merged computational model is calibrated using the relative frequencies and distributions of chromosomal aberrations reported in the literature. The model considers fractionated deposition of energy to approximate dose rates of the space flight environment. The merged model also predicts of the yields and sizes of translocations, dicentrics, rings, and more complex-type aberrations formed in the G0/G1 cell cycle phase during the first cell division after irradiation.

Fragility Extraordinaire: Unsolved Mysteries of Chromosome Fragile Sites.

PubMed

Feng, Wenyi; Chakraborty, Arijita

2017-01-01

Chromosome fragile sites are a fascinating cytogenetic phenomenon now widely implicated in a slew of human diseases ranging from neurological disorders to cancer. Yet, the paths leading to these revelations were far from direct, and the number of fragile sites that have been molecularly cloned with known disease-associated genes remains modest. Moreover, as more fragile sites were being discovered, research interests in some of the earliest discovered fragile sites ebbed away, leaving a number of unsolved mysteries in chromosome biology. In this review we attempt to recount some of the early discoveries of fragile sites and highlight those phenomena that have eluded intense scrutiny but remain extremely relevant in our understanding of the mechanisms of chromosome fragility. We then survey the literature for disease association for a comprehensive list of fragile sites. We also review recent studies addressing the underlying cause of chromosome fragility while highlighting some ongoing debates. We report an observed enrichment for R-loop forming sequences in fragile site-associated genes than genomic average. Finally, we will leave the reader with some lingering questions to provoke discussion and inspire further scientific inquiries.

Cytotoxicity of aluminum oxide nanoparticles on Allium cepa root tip--effects of oxidative stress generation and biouptake.

PubMed

Rajeshwari, A; Kavitha, S; Alex, Sruthi Ann; Kumar, Deepak; Mukherjee, Anita; Chandrasekaran, Natarajan; Mukherjee, Amitava

2015-07-01

The commercial usage of Al2O3 nanoparticles (Al2O3 NPs) has gone up significantly in the recent times, enhancing the risk of environmental contamination with these agents and their consequent adverse effects on living systems. The current study has been designed to evaluate the cytogenetic potential of Al2O3 NPs in Allium cepa (root tip cells) at a range of exposure concentrations (0.01, 0.1, 1, 10, and 100 μg/mL), their uptake/internalization profile, and the oxidative stress generated. We noted a dose-dependent decrease in the mitotic index (42 to 28 %) and an increase in the number of chromosomal aberrations. Various chromosomal aberrations, e.g. sticky, multipolar and laggard chromosomes, chromosomal breaks, and the formation of binucleate cells, were observed by optical, fluorescence, and confocal laser scanning microscopy. FT-IR analysis demonstrated the surface chemical interaction between the nanoparticles and root tip cells. The biouptake of Al2O3 in particulate form led to reactive oxygen species generation, which in turn probably contributed to the induction of chromosomal aberrations.

Force-balance model of suppression of multipolar division in cancer cells with extra centrosomes

NASA Astrophysics Data System (ADS)

Zhu, Jie

2013-03-01

Cancer cells often possess extra centrosomes which have the potential to cause cell death due to catastrophic multipolar division. Many cancer cells, however, are able to escape multipolar mitosis by clustering the extra centrosomes to form bipolar spindles. The mechanism of centrosome clustering is therefore of great interest to the development of anti-cancer drugs because the de-clustering of extra centrosomes provides an appealing way to eliminate cancer cells while keeping healthy cells intact. We present a physical model assuming 1) dynamic centrosomal microtubules interact with chromosomes by both pushing on chromosome arms and pulling along kinetochores; 2) these microtubules interact with force generators associated with actin/adhesion structures at the cell boundary; and 3) motors act on anti-parallel microtubules from different centrosomes. We find via computer simulations that chromosomes tend to aggregate near the cell center while centrosomes can be either clustered to form bipolar spindles or scattered to form multipolar spindles, depending on the strengths of relative forces, cell shape and adhesion geometry. The model predictions agree with data from cells plated on adhesive micropatterns and from biochemically or genetically perturbed cells. Furthermore, our model is able to explain various microtubule distributions in interphase cells on patterned substrates. This work was supported by NSF

Ahp2 (Hop2) function in Arabidopsis thaliana (Ler) is required for stabilization of close alignment and synaptonemal complex formation except for the two short arms that contain nucleolus organizer regions.

PubMed

Stronghill, P; Pathan, N; Ha, H; Supijono, E; Hasenkampf, C

2010-08-01

A cytological comparative analysis of male meiocytes was performed for Arabidopsis wild type and the ahp2 (hop2) mutant with emphasis on ahp2's largely uncharacterized prophase I. Leptotene progression appeared normal in ahp2 meiocytes; chromosomes exhibited regular axis formation and assumed a typical polarized nuclear organization. In contrast, 4',6'-diamidino-2-phenylindole-stained ahp2 pachytene chromosome spreads demonstrated a severe reduction in stabilized pairing. However, transmission electron microscopy (TEM) analysis of sections from meiocytes revealed that ahp2 chromosome axes underwent significant amounts of close alignment (44% of total axis). This apparent paradox strongly suggests that the Ahp2 protein is involved in the stabilization of homologous chromosome close alignment. Fluorescent in situ hybridization in combination with Zyp1 immunostaining revealed that ahp2 mutants undergo homologous synapsis of the nucleolus-organizer-region-bearing short arms of chromosomes 2 and 4, despite the otherwise "nucleus-wide" lack of stabilized pairing. The duration of ahp2 zygotene was significantly prolonged and is most likely due to difficulties in chromosome alignment stabilization and subsequent synaptonemal complex formation. Ahp2 and Mnd1 proteins have previously been shown, "in vitro," to form a heterodimer. Here we show, "in situ," that the Ahp2 and Mnd1 proteins are synchronous in their appearance and disappearance from meiotic chromosomes. Both the Ahp2 and Mnd1 proteins localize along the chromosomal axis. However, localization of the Ahp2 protein was entirely foci-based whereas Mnd1 protein exhibited an immunostaining pattern with some foci along the axis and a diffuse staining for the rest of the chromosome.

Early and Late Chromosome Damages in Human Lymphocytes Induced by Gamma Rays and Fe Ions

NASA Technical Reports Server (NTRS)

Sunagawa, Mayumi; Zhang, Ye; Yeshitla, Samrawit; Kadhim, Munira; Wilson, Bobby; Wu, Honglu

2014-01-01

Chromosomal translocations and inversions are considered stable, and cells containing these types of chromosome aberrations can survive multiple cell divisions. An efficient method to detect an inversion is multi-color banding fluorescent in situ hybridization (mBAND) which allows identification of both inter- and intrachromosome aberrations simultaneously. Post irradiation, chromosome aberrations may also arise after multiple cell divisions as a result of genomic instability. To investigate the stable or late-arising chromosome aberrations induced after radiation exposure, we exposed human lymphocytes to gamma rays and Fe ions ex vivo, and cultured the cells for multiple generations. Chromosome aberrations were analyzed in cells collected at first mitosis and at several time intervals during the culture period post irradiation. With gamma irradiation, about half of the damages observed at first mitosis remained after 7 day- and 14 day- culture, suggesting the transmissibility of damages to the surviving progeny. Detailed analysis of chromosome break ends participating in exchanges revealed a greater fraction of break ends involved in intrachromosome aberrations in the 7- and 14-day samples in comparison to the fraction at first mitosis. In particular, simple inversions were found at 7 and 14 days, but not at the first mitosis, suggesting that some of the aberrations might be formed days post irradiation. In contrast, at the doses that produced similar frequencies of gamma-induced chromosome aberrations as observed at first mitosis, a significantly lower yield of aberrations remained at the same population doublings after Fe ion exposure. At these equitoxic doses, more complex type aberrations were observed for Fe ions, indicating that Fe ion-induced initial chromosome damages are more severe and may lead to cell death. Comparison between low and high doses of Fe ion irradiation in the induction of late damages will also be discussed.

A palindrome-mediated mechanism distinguishes translocations involving LCR-B of chromosome 22q11.2.

PubMed

Gotter, Anthony L; Shaikh, Tamim H; Budarf, Marcia L; Rhodes, C Harker; Emanuel, Beverly S

2004-01-01

Two known recurrent constitutional translocations, t(11;22) and t(17;22), as well as a non-recurrent t(4;22), display derivative chromosomes that have joined to a common site within the low copy repeat B (LCR-B) region of 22q11.2. This breakpoint is located between two AT-rich inverted repeats that form a nearly perfect palindrome. Breakpoints within the 11q23, 17q11 and 4q35 partner chromosomes also fall near the center of palindromic sequences. In the present work the breakpoints of a fourth translocation involving LCR-B, a balanced ependymoma-associated t(1;22), were characterized not only to localize this junction relative to known genes, but also to further understand the mechanism underlying these rearrangements. FISH mapping was used to localize the 22q11.2 breakpoint to LCR-B and the 1p21 breakpoint to single BAC clones. STS mapping narrowed the 1p21.2 breakpoint to a 1990 bp AT-rich region, and junction fragments were amplified by nested PCR. Junction fragment-derived sequence indicates that the 1p21.2 breakpoint splits a 278 nt palindrome capable of forming stem-loop secondary structure. In contrast, the 1p21.2 reference genomic sequence from clones in the database does not exhibit this configuration, suggesting a predisposition for regional genomic instability perhaps etiologic for this rearrangement. Given its similarity to known chromosomal fragile site (FRA) sequences, this polymorphic 1p21.2 sequence may represent one of the FRA1 loci. Comparative analysis of the secondary structure of sequences surrounding translocation breakpoints that involve LCR-B with those not involving this region indicate a unique ability of the former to form stem-loop structures. The relative likelihood of forming these configurations appears to be related to the rate of translocation occurrence. Further analysis suggests that constitutional translocations in general occur between sequences of similar melting temperature and propensity for secondary structure.

A palindrome-mediated mechanism distinguishes translocations involving LCR-B of chromosome 22q11.2

PubMed Central

Gotter, Anthony L.; Shaikh, Tamim H.; Budarf, Marcia L.; Rhodes, C. Harker; Emanuel, Beverly S.

2010-01-01

Two known recurrent constitutional translocations, t(11;22) and t(17;22), as well as a non-recurrent t(4;22), display derivative chromosomes that have joined to a common site within the low copy repeat B (LCR-B) region of 22q11.2. This breakpoint is located between two AT-rich inverted repeats that form a nearly perfect palindrome. Breakpoints within the 11q23, 17q11 and 4q35 partner chromosomes also fall near the center of palindromic sequences. In the present work the breakpoints of a fourth translocation involving LCR-B, a balanced ependymoma-associated t(1;22), were characterized not only to localize this junction relative to known genes, but also to further understand the mechanism underlying these rearrangements. FISH mapping was used to localize the 22q11.2 breakpoint to LCR-B and the 1p21 breakpoint to single BAC clones. STS mapping narrowed the 1p21.2 breakpoint to a 1990 bp AT-rich region, and junction fragments were amplified by nested PCR. Junction fragment-derived sequence indicates that the 1p21.2 breakpoint splits a 278 nt palindrome capable of forming stem–loop secondary structure. In contrast, the 1p21.2 reference genomic sequence from clones in the database does not exhibit this configuration, suggesting a predisposition for regional genomic instability perhaps etiologic for this rearrangement. Given its similarity to known chromosomal fragile site (FRA) sequences, this polymorphic 1p21.2 sequence may represent one of the FRA1 loci. Comparative analysis of the secondary structure of sequences surrounding translocation breakpoints that involve LCR-B with those not involving this region indicate a unique ability of the former to form stem–loop structures. The relative likelihood of forming these configurations appears to be related to the rate of translocation occurrence. Further analysis suggests that constitutional translocations in general occur between sequences of similar melting temperature and propensity for secondary structure. PMID:14613967

High-Resolution Whole-Genome Sequencing Reveals That Specific Chromatin Domains from Most Human Chromosomes Associate with Nucleoli

PubMed Central

van Koningsbruggen, Silvana; Gierliński, Marek; Schofield, Pietá; Martin, David; Barton, Geoffey J.; Ariyurek, Yavuz; den Dunnen, Johan T.

2010-01-01

The nuclear space is mostly occupied by chromosome territories and nuclear bodies. Although this organization of chromosomes affects gene function, relatively little is known about the role of nuclear bodies in the organization of chromosomal regions. The nucleolus is the best-studied subnuclear structure and forms around the rRNA repeat gene clusters on the acrocentric chromosomes. In addition to rDNA, other chromatin sequences also surround the nucleolar surface and may even loop into the nucleolus. These additional nucleolar-associated domains (NADs) have not been well characterized. We present here a whole-genome, high-resolution analysis of chromatin endogenously associated with nucleoli. We have used a combination of three complementary approaches, namely fluorescence comparative genome hybridization, high-throughput deep DNA sequencing and photoactivation combined with time-lapse fluorescence microscopy. The data show that specific sequences from most human chromosomes, in addition to the rDNA repeat units, associate with nucleoli in a reproducible and heritable manner. NADs have in common a high density of AT-rich sequence elements, low gene density and a statistically significant enrichment in transcriptionally repressed genes. Unexpectedly, both the direct DNA sequencing and fluorescence photoactivation data show that certain chromatin loci can specifically associate with either the nucleolus, or the nuclear envelope. PMID:20826608

High-resolution whole-genome sequencing reveals that specific chromatin domains from most human chromosomes associate with nucleoli.

PubMed

van Koningsbruggen, Silvana; Gierlinski, Marek; Schofield, Pietá; Martin, David; Barton, Geoffey J; Ariyurek, Yavuz; den Dunnen, Johan T; Lamond, Angus I

2010-11-01

The nuclear space is mostly occupied by chromosome territories and nuclear bodies. Although this organization of chromosomes affects gene function, relatively little is known about the role of nuclear bodies in the organization of chromosomal regions. The nucleolus is the best-studied subnuclear structure and forms around the rRNA repeat gene clusters on the acrocentric chromosomes. In addition to rDNA, other chromatin sequences also surround the nucleolar surface and may even loop into the nucleolus. These additional nucleolar-associated domains (NADs) have not been well characterized. We present here a whole-genome, high-resolution analysis of chromatin endogenously associated with nucleoli. We have used a combination of three complementary approaches, namely fluorescence comparative genome hybridization, high-throughput deep DNA sequencing and photoactivation combined with time-lapse fluorescence microscopy. The data show that specific sequences from most human chromosomes, in addition to the rDNA repeat units, associate with nucleoli in a reproducible and heritable manner. NADs have in common a high density of AT-rich sequence elements, low gene density and a statistically significant enrichment in transcriptionally repressed genes. Unexpectedly, both the direct DNA sequencing and fluorescence photoactivation data show that certain chromatin loci can specifically associate with either the nucleolus, or the nuclear envelope.

Basic mechanism for biorientation of mitotic chromosomes is provided by the kinetochore geometry and indiscriminate turnover of kinetochore microtubules

PubMed Central

Zaytsev, Anatoly V.; Grishchuk, Ekaterina L.

2015-01-01

Accuracy of chromosome segregation relies on the ill-understood ability of mitotic kinetochores to biorient, whereupon each sister kinetochore forms microtubule (MT) attachments to only one spindle pole. Because initial MT attachments result from chance encounters with the kinetochores, biorientation must rely on specific mechanisms to avoid and resolve improper attachments. Here we use mathematical modeling to critically analyze the error-correction potential of a simplified biorientation mechanism, which involves the back-to-back arrangement of sister kinetochores and the marked instability of kinetochore–MT attachments. We show that a typical mammalian kinetochore operates in a near-optimal regime, in which the back-to-back kinetochore geometry and the indiscriminate kinetochore–MT turnover provide strong error-correction activity. In human cells, this mechanism alone can potentially enable normal segregation of 45 out of 46 chromosomes during one mitotic division, corresponding to a mis-segregation rate in the range of 10−1–10−2 per chromosome. This theoretical upper limit for chromosome segregation accuracy predicted with the basic mechanism is close to the mis-segregation rate in some cancer cells; however, it cannot explain the relatively low chromosome loss in diploid human cells, consistent with their reliance on additional mechanisms. PMID:26424798

cDNA cloning, tissue distribution, and chromosomal localization of myelodysplasia/Myeloid Leukemia Factor 2 (MLF2)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuefer, M.U.; Valentine, V.; Behm, F.G.

A fusion gene between nucleophosmin (NPM) and myelodysplasia/myeloid leukemia factor 1 (MLF1) and myelodysplasia/myeloid leukemia factor 1 (MLF1) is formed by a recurrent t(3;5)(q25.1;q34) in myelodysplastic syndrome and acute myeloid leukemia. Here we report the identification of a novel gene, MLF2, which contains an open reading frame of 744 bp encoding a 248-amino-acid protein highly related to the previously identified MLF1 protein (63% similarity, 40% identity). In contrast to the tissue-restricted expression pattern of MLF1, and MLF2 messenger RNA is expressed ubiquitously. The MLF2 gene locus was mapped by fluorescence in situ hybridization to human chromosome 12p13, a chromosomal regionmore » frequently involved in translocations and deletions in acute leukemias of lymphoid or myeloid lineage. In a physical map of chromosome 12, MLF2 was found to reside on the yeast artificial chromosome clone 765b9. Southern blotting analysis of malignant cell DNAs prepared from a series of acute lymphoblastic leukemia cases with translocations involving chromosome arm 12p, as well as a group of acute myeloid leukemias with various cytogenetic abnormalities, failed to reveal MLF2 gene rearrangements. 19 refs., 2 figs.« less

Coincidence of synteny breakpoints with malignancy-related deletions on human chromosome 3

PubMed Central

Kost-Alimova, Maria; Kiss, Hajnalka; Fedorova, Ludmila; Yang, Ying; Dumanski, Jan P.; Klein, George; Imreh, Stefan

2003-01-01

We have found previously that during tumor growth intact human chromosome 3 transferred into tumor cells regularly looses certain 3p regions, among them the ≈1.4-Mb common eliminated region 1 (CER1) at 3p21.3. Fluorescence in situ hybridization analysis of 12 mouse orthologous loci revealed that CER1 splits into two segments in mouse and therefore contains a murine/human conservation breakpoint region (CBR). Several breaks occurred in tumors within the region surrounding the CBR, and this sequence has features that characterize unstable chromosomal regions: deletions in yeast artificial chromosome clones, late replication, gene and segment duplications, and pseudogene insertions. Sequence analysis of the entire 3p12-22 revealed that other cancer-associated deletions (regions eliminated from monochromosomal hybrids carrying an intact chromosome 3 during tumor growth and homozygous deletions found in human tumors) colocalized nonrandomly with murine/human CBRs and were characterized by an increased number of local gene duplications and murine/human conservation mismatches (single genes that do not match into the conserved chromosomal segment). The CBR within CER1 contains a simple tandem TATAGA repeat capable of forming a 40-bp-long secondary hairpin-like structure. This repeat is nonrandomly localized within the other tumor-associated deletions and in the vicinity of 3p12-22 CBRs. PMID:12738884

Extreme selective sweeps independently targeted the X chromosomes of the great apes

PubMed Central

Nam, Kiwoong; Munch, Kasper; Hobolth, Asger; Dutheil, Julien Yann; Veeramah, Krishna R.; Woerner, August E.; Hammer, Michael F.; Mailund, Thomas; Schierup, Mikkel Heide

2015-01-01

The unique inheritance pattern of the X chromosome exposes it to natural selection in a way that is different from that of the autosomes, potentially resulting in accelerated evolution. We perform a comparative analysis of X chromosome polymorphism in 10 great ape species, including humans. In most species, we identify striking megabase-wide regions, where nucleotide diversity is less than 20% of the chromosomal average. Such regions are found exclusively on the X chromosome. The regions overlap partially among species, suggesting that the underlying targets are partly shared among species. The regions have higher proportions of singleton SNPs, higher levels of population differentiation, and a higher nonsynonymous-to-synonymous substitution ratio than the rest of the X chromosome. We show that the extent to which diversity is reduced is incompatible with direct selection or the action of background selection and soft selective sweeps alone, and therefore, we suggest that very strong selective sweeps have independently targeted these specific regions in several species. The only genomic feature that we can identify as strongly associated with loss of diversity is the location of testis-expressed ampliconic genes, which also have reduced diversity around them. We hypothesize that these genes may be responsible for selective sweeps in the form of meiotic drive caused by an intragenomic conflict in male meiosis. PMID:25941379

Wild sex in the grasses.

PubMed

Able, Jason A; Langridge, Peter

2006-06-01

To date, alien introgression of agronomically important traits into bread wheat (Triticum aestivum) from wild relatives has not been readily achievable through traditional breeding practices. However, this door might now be unlocked. The insightful research published recently by Graham Moore and his team delivers a likely candidate in the form of a cdc2-kinase-related gene family for the Ph1 locus--a chromatin region located on chromosome 5B that is responsible for homologous chromosome pairing integrity in bread wheat.

Currently recognized clinically relevant and known genes for human reproduction and related infertility with representation on high-resolution chromosome ideograms.

PubMed

Butler, Merlin G; Rafi, Syed K; McGuire, Austen; Manzardo, Ann M

2016-01-01

To provide an update of currently recognized clinically relevant candidate and known genes for human reproduction and related infertility plotted on high resolution chromosome ideograms (850 band level) and represented alphabetically in tabular form. Descriptive authoritative computer-based website and peer-reviewed medical literature searches used pertinent keywords representing human reproduction and related infertility along with genetics and gene mutations. A master list of genes associated with human reproduction and related infertility was generated with a visual representation of gene locations on high resolution chromosome ideograms. GeneAnalytics pathway analysis was carried out on the resulting list of genes to assess underlying genetic architecture for infertility. Advances in genetic technology have led to the discovery of genes responsible for reproduction and related infertility. Genes identified (N=371) in our search primarily impact ovarian steroidogenesis through sex hormone biology, germ cell production, genito-urinary or gonadal development and function, and related peptide production, receptors and regulatory factors. The location of gene symbols plotted on high resolution chromosome ideograms forms a conceptualized image of the distribution of human reproduction genes. The updated master list can be used to promote better awareness of genetics of reproduction and related infertility and advance discoveries on genetic causes and disease mechanisms. Copyright © 2015 Elsevier B.V. All rights reserved.

Stable chromosomal aberrations in haemopoietic stem cells in the blood of radiation accident victims.

PubMed

Kreja, L; Greulich, K M; Fliedner, T M; Heinze, B

1999-10-01

The detection of long-term persistent chromosome aberrations in circulating haemopoietic stem cells after accidental radiation exposure. Peripheral blood samples from highly exposed persons were collected 7-25 years after the radiation accidents in Moscow (1971), Kazan (1975) and Chernobyl (1996). Haemopoietic blood stem cells were analysed when investigating individual colonies derived from haemopoietic progenitor cells: burst-forming units-erythroid (BFU-E), granulocyte-macrophage-colony-forming cells (GM-CFC) and multipotent granulocyte-erythrocyte-macrophage- megakaryocyte-colony-forming cells (GEMM-CFC). Colony formation was obtained in methylcellulose cultures. Chromosome preparations in single colonies were performed using a microtechnique. Nine patients were investigated at 1 to 4 follow-up time points after radiation exposure. Three hundred and thirty-four single colonies were analyzed resulting in 1375 mitoses. It was found that colonies showed chromosome aberrations (ChA) up to 25 years after radiation exposure by classical cytogenetics and by fluorescence in situ hybridization (FISH). Stable aberrations were detected in 21% of colonies. They were clonal in 19% of colonies, i.e. the same abnormality was found in all cells derived from a single colony. In 2% of colonies ChA were stable but non-clonal; unstable ChA were not observed. The results indicate that blood-derived haemopoietic stem cells may serve as a biological indicator to detect radiation-induced ChA. Since they are considered to be in dynamic and functional exchange with stem cells in the medullary sites of blood cell formation such as bone marrow, the use of blood stem cells as a marker of radiation effects should be explored to assess the repair status of the stem cell pool as such.

A cytological approach to study meiotic recombination and chromosome dynamics of Arabidopsis thaliana male meiocytes in three dimensions.

PubMed

Hurel, Aurélie; Phillips, Dylan; Vrielynck, Nathalie; Mézard, Christine; Grelon, Mathilde; Christophorou, Nicolas

2018-04-22

During meiotic prophase I chromosomes undergo dramatic conformational changes that accompany chromosome condensation, pairing and recombination between homologs. These changes include the anchoring of telomeres to the nuclear envelope and their clustering to form a bouquet. In plants, these events have been studied and illustrated in intact meiocytes of large genome species. Arabidopsis thaliana is an excellent genetic model where major molecular pathways that control synapsis and recombination between homologs have been uncovered. Yet the study of chromosome dynamics is hampered by current cytological methods that disrupt the 3D architecture of the nucleus. Here we set up a protocol to preserve the 3D configuration of A. thaliana meiocytes. We showed that this technique is compatible with the use of a variety of antibodies that label structural and recombination proteins and were able to highlight the presence of clustered synapsis initiation centers at the nuclear periphery. By using fluorescence in situ hybridization (FISH) we also studied chromosome behavior during premeiotic G2 and prophase I, revealing the existence of a telomere bouquet during A. thaliana male meiosis. In addition we showed that the number of telomeres in a bouquet and its volume vary greatly thus revealing the complexity of telomere behavior during meiotic prophase I. Finally, by using probes that label subtelomeric regions of individual chromosomes we revealed differential localization behaviors of chromosome ends. Our protocol opens new areas of research to investigate chromosome dynamics in A. thaliana meiocytes. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Distributions of Low- and High-LET Radiation-Induced Breaks in Chromosomes are Associated with Inter- and Intrachromosome Exchanges

NASA Technical Reports Server (NTRS)

Hada, Megumi; Zhang, Ye; Feiveson, Alan; Cucinotta, Francis A.; Wu, Honglu

2010-01-01

To study the breakpoint along the length of the chromosome induced by low- and high-LET radiations, we exposed human epithelial cells in vitro to Cs-137 rays at both low and high dose rates, secondary neutrons at a low dose rate, and 600 MeV/u Fe ions at a high dose rate. The location of the breaks was identified using the multicolor banding in situ hybridization (mBAND) that paints Chromosome 3 in 23 different colored bands. The breakpoint distributions were found to be similar between rays of low and high dose rates and between the two high-LET radiation types. Detailed analysis of the chromosome break ends involved in inter- and intrachromosome exchanges revealed that only the break ends participating in interchromosome exchanges contributed to the hot spots found for low-LET. For break ends participating in intrachromosome exchanges, the distributions for all four radiation scenarios were similar with clusters of breaks found in three regions. Analysis of the locations of the two break ends in Chromosome 3 that joined to form an intrachromosome exchange demonstrated that two breaks with a greater genomic separation may be more likely to rejoin than two closer breaks, indicating that chromatin folding can play an important role in the rejoining of chromosome breaks. Our study demonstrated that the gene-rich regions do not necessarily contain more breaks. The breakpoint distribution depends more on the likelihood that a break will join with another break in the same chromosome or in a different chromosome.

Clinically relevant known and candidate genes for obesity and their overlap with human infertility and reproduction.

PubMed

Butler, Merlin G; McGuire, Austen; Manzardo, Ann M

2015-04-01

Obesity is a growing public health concern now reaching epidemic status worldwide for children and adults due to multiple problems impacting on energy intake and expenditure with influences on human reproduction and infertility. A positive family history and genetic factors are known to play a role in obesity by influencing eating behavior, weight and level of physical activity and also contributing to human reproduction and infertility. Recent advances in genetic technology have led to discoveries of new susceptibility genes for obesity and causation of infertility. The goal of our study was to provide an update of clinically relevant candidate and known genes for obesity and infertility using high resolution chromosome ideograms with gene symbols and tabular form. We used computer-based internet websites including PubMed to search for combinations of key words such as obesity, body mass index, infertility, reproduction, azoospermia, endometriosis, diminished ovarian reserve, estrogen along with genetics, gene mutations or variants to identify evidence for development of a master list of recognized obesity genes in humans and those involved with infertility and reproduction. Gene symbols for known and candidate genes for obesity were plotted on high resolution chromosome ideograms at the 850 band level. Both infertility and obesity genes were listed separately in alphabetical order in tabular form and those highlighted when involved with both conditions. By searching the medical literature and computer generated websites for key words, we found documented evidence for 370 genes playing a role in obesity and 153 genes for human reproduction or infertility. The obesity genes primarily affected common pathways in lipid metabolism, deposition or transport, eating behavior and food selection, physical activity or energy expenditure. Twenty-one of the obesity genes were also associated with human infertility and reproduction. Gene symbols were plotted on high resolution ideograms and their name, precise chromosome band location and description were summarized in tabular form. Meaningful correlations in the obesity phenotype and associated human infertility and reproduction are represented with the location of genes on chromosome ideograms along with description of the gene and position in tabular form. These high resolution chromosome ideograms and tables will be useful in genetic awareness and counseling, diagnosis and treatment to improve clinical outcomes.

Structural organization of chromatin during the cell cycle of Entamoeba histolytica trophozoites.

PubMed

Argüello, C; Valenzuela, B; Rangel, E

1992-01-01

The nuclear division of E. histolytica trophozoites was analyzed by using specific stains for DNA, with the aim to define the sequential changes of chromatin during its life cycle. Furthermore, we characterized the internal structural arrangements of microtubules in the microtubular organizing center (MTOC) and determined the number of chromosomes and its association with the spindle. The MTOC is formed by multiple microtubule-nucleating centers, that are involved in the displacement of DNA during nuclear division. We found the existence of a single MTOC in one pole of the nucleus at early anaphase. Our results lead us to propose a new hypothesis in which it is suggested that metaphase corresponds to the arrangement of condensed DNA bodies, or "chromosomes" around the MTOC and, through the assembly of microtubules, one set of uncondensed chromatin is displaced to the opposite pole of the nucleus, while the other remains condensed and associated to the original MTOC. We observed six chromosomes in our preparations, corroborating previous observations (2,3). Whether or not a new MTOC is formed during nuclear division remains to be clarified.

Enrichment of dynamic chromosomal crosslinks drive phase separation of the nucleolus.

PubMed

Hult, Caitlin; Adalsteinsson, David; Vasquez, Paula A; Lawrimore, Josh; Bennett, Maggie; York, Alyssa; Cook, Diana; Yeh, Elaine; Forest, Mark Gregory; Bloom, Kerry

2017-11-02

Regions of highly repetitive DNA, such as those found in the nucleolus, show a self-organization that is marked by spatial segregation and frequent self-interaction. The mechanisms that underlie the sequestration of these sub-domains are largely unknown. Using a stochastic, bead-spring representation of chromatin in budding yeast, we find enrichment of protein-mediated, dynamic chromosomal cross-links recapitulates the segregation, morphology and self-interaction of the nucleolus. Rates and enrichment of dynamic crosslinking have profound consequences on domain morphology. Our model demonstrates the nucleolus is phase separated from other chromatin in the nucleus and predicts that multiple rDNA loci will form a single nucleolus independent of their location within the genome. Fluorescent labeling of budding yeast nucleoli with CDC14-GFP revealed that a split rDNA locus indeed forms a single nucleolus. We propose that nuclear sub-domains, such as the nucleolus, result from phase separations within the nucleus, which are driven by the enrichment of protein-mediated, dynamic chromosomal crosslinks. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

v-Src-driven transformation is due to chromosome abnormalities but not Src-mediated growth signaling.

PubMed

Honda, Takuya; Morii, Mariko; Nakayama, Yuji; Suzuki, Ko; Yamaguchi, Noritaka; Yamaguchi, Naoto

2018-01-18

v-Src is the first identified oncogene product and has a strong tyrosine kinase activity. Much of the literature indicates that v-Src expression induces anchorage-independent and infinite cell proliferation through continuous stimulation of growth signaling by v-Src activity. Although all of v-Src-expressing cells are supposed to form transformed colonies, low frequencies of v-Src-induced colony formation have been observed so far. Using cells that exhibit high expression efficiencies of inducible v-Src, we show that v-Src expression causes cell-cycle arrest through p21 up-regulation despite ERK activation. v-Src expression also induces chromosome abnormalities and unexpected suppression of v-Src expression, leading to p21 down-regulation and ERK inactivation. Importantly, among v-Src-suppressed cells, only a limited number of cells gain the ability to re-proliferate and form transformed colonies. Our findings provide the first evidence that v-Src-driven transformation is attributed to chromosome abnormalities, but not continuous stimulation of growth signaling, possibly through stochastic genetic alterations.

M-BAND analysis of chromosome aberration induced by Fe-ions in human epithelial cells cultured in 3-dimensional matrices

NASA Astrophysics Data System (ADS)

Hada, Megumi; Cucinotta, Francis A.; Wu, Honglu

Energetic heavy ions pose a great health risk to astronauts in extended ISS and future lunar and Mars missions. High-LET heavy ions are particularly effective in causing various biological effects, including cell inactivation, genetic mutations, cataracts and cancer induction. Most of these biological endpoints are closely related to chromosomal damage, which can be utilized as a biomarker for radiation insults. Previously, we had studied lowand high-LET radiationinduced chromosome aberrations in human epithelial cells cultured in 2-dimension (2D) using the multicolor banding fluorescence in situ hybridization (mBAND) technique. However, it has been realized that the biological response to radiation insult in a 2D cellular environment in vitro can differ significantly from the response in 3-dimension (3D) or at the actual tissue level. In this study, we cultured human epithelial cells in 3D to provide a more suitable model for human tissue. Human mammary epithelial cells (CH184B5F5/M10) were grown in Matrigel to form 3D structures, and exposed to Fe-ions at NASA Space Radiation Laboratory (NSRL) at the Brookhaven National Laboratory or 137 Cs-gamma radiation source at the University of Texas MD Anderson Cancer Center. After exposure, cells were allowed to repair for 16hr before dissociation and subcultured at low density in 2D. G2 and metaphase chromosomes in the first cell cycle were collected using a chemical-induced premature chromosome condensation (PCC) technique, and chromosome aberrations were analyzed using mBAND technique. With this technique, individually painted chromosomal bands on one chromosome allowed the identification of interchromosomal aberrations (translocation to unpainted chromosomes) and intrachromosomal aberrations (inversions and deletions within a single painted chromosome). Our data indicate a significant difference of the chromosome aberration yield between 2D and 3D cell cultures for gamma exposures, but not for Fe ion exposures. Therefore, the RBE for chromosome aberrations obtained in a 2D model may not represent accurately the RBE for tissues.

High- and low-LET Radiation-induced Chromosome Aberrations in Human Epithelial Cells Cultured in 3-dimensional Matrices

NASA Technical Reports Server (NTRS)

Hada, M.; George K.; Cucinotta, F. A.; Wu, H.

2008-01-01

Energetic heavy ions pose a great health risk to astronauts who participate in extended ISS missions and will be an even greater concern for future manned lunar and Mars missions. High-LET heavy ions are particularly effective in causing various biological effects, including cell inactivation, genetic mutations, cataracts and cancer induction. Most of these biological endpoints are closely related to chromosomal damage, which can be utilized as a biomarker for radiation insults. Previously, we had studied low- and high-LET radiation-induced chromosome aberrations in human epithelial cells cultured in 2-dimension (2D) using the multicolor banding fluorescence in situ hybridization (mBAND) technique. However, it has been realized that the biological response to radiation insult in a 2D in vitro cellular environment can differ significantly from the response in 3-dimension (3D) or at the actual tissue level. In this study, we cultured human epithelial cells in 3D to provide a more suitable model for human tissue. Human mammary epithelial cells (CH184B5F5/M10) were grown in Matrigel to form 3D structures, and exposed to Fe-ions at NASA Space Radiation Laboratory (NSRL) at the Brookhaven National Laboratory or 137Cs-gamma radiation source at the University of Texas MD Anderson Cancer Center. After exposure, cells were allowed to repair for 16hr before dissociation and subcultured at low density in 2D. G2 and metaphase chromosomes in the first cell cycle were collected in the first cell cycle after irradiation using a chemical-induced premature chromosome condensation (PCC) technique, and chromosome aberrations were analyzed using mBAND technique. With this technique, individually painted chromosomal bands on one chromosome allowed the identification of interchromosomal aberrations (translocation to unpainted chromosomes) and intrachromosomal aberrations (inversions and deletions within a single painted chromosome). Our data indicate a significant difference in the chromosome aberration yield between 2D and 3D cell cultures after gamma exposures, but not after Fe ion exposures. Therefore, the Relative Biological Effect (RBE) for induction of chromosome aberrations obtained in a 2D model may not accurately represent RBE values obtained for tissue exposure.

M-BAND Analysis of Chromosome Aberration Induced by Fe-Ions in Human Epithelial Cells Cultured in 3-Dimensional Matrices

NASA Technical Reports Server (NTRS)

Hada, M.; Cucinotta, F. A.; Wu, H.

2008-01-01

Energetic heavy ions pose a great health risk to astronauts in extended ISS and future lunar and Mars missions. High-LET heavy ions are particularly effective in causing various biological effects, including cell inactivation, genetic mutations, cataracts and cancer induction. Most of these biological endpoints are closely related to chromosomal damage, which can be utilized as a biomarker for radiation insults. Previously, we had studied low- and high-LET radiation-induced chromosome aberrations in human epithelial cells cultured in 2-dimension (2D) using the multicolor banding fluorescence in situ hybridization (mBAND) technique. However, it has been realized that the biological response to radiation insult in a 2D cellular environment in vitro can differ significantly from the response in 3-dimension (3D) or at the actual tissue level. In this study, we cultured human epithelial cells in 3D to provide a more suitable model for human tissue. Human mammary epithelia cells (CH184B5F5/M10) were grown in Matrigel to form 3D structures, and exposed to Fe-ions at NASA Space Radiation Laboratory (NSRL) at the Brookhaven National Laboratory or 137Cs-gamma radiation source at the University of Texas MD Anderson Cancer Center. After exposure, cells were allowed to repair for 16hr before dissociation and subcultued at low density in 2D. G2 and metaphase chromosomes in the first cell cycle were collected using a chemical-induced premature chromosome condensation (PCC) technique, and chromosome aberrations were analyzed using mBAND technique. With this technique, individually painted chromosomal bands on one chromosome allowed the identification of interchromosomal aberrations (translocation to unpainted chromosomes) and intrachromosomal aberrations (inversions and deletions within a single painted chromosome). Our data indicate a significant difference of the chromosome aberration yield between 2D and 3D cell cultures for gamma exposures, but not for Fe ion exposures. Therefore, the RBE for chromosome aberrations obtained in a 2D model may not represent accurately the RBE for tissues.

STUDIES OF MEIOSIS IN LUZULA PURPUREA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nordenskiold, H.

1962-01-01

In Luzula purpurea, which has diffuse centromeres and only six chromosomes, a study was made of the separation of chromatids during the first meiotic division, the pairing of the free chromitids at interkinesis, and the chromosomes of first mitosis of the pollen tetrads. Two strains were used, the normal type of L. purpurea with 2n = 6, and certain plants selected among the x- irradiated survivors. The normal plants had six somatic chromosomes of equal size that could not be distinguished from each other. The x-irradiated plants originated from material treated with 2500 or 1000 r as seedlings. Mitotic chromosomemore » patterns were examined in progenies of the treated plants. Several of the irradiated plants were found to have 2n = 7 with five normal-sized chromosomes and one chromosome fragmented into two pieces of about equal size. Pairing of chromosomes during meiosis in these irradiated plants was compared with that in the normal L. purpurea with 2n = 6, and the distribution of large and small chromosomes between the four cells of the pollen tetrads was examined. Five of the original six chromosomes were unaffected by the x-ray treatment. A study of meiosis verified the postulated type of fragmentation of the 6th one. One heteromorphic association is formed in each cell of meiosis, originating from the pairing between the two fragments and their homologous unbroken partner. The association is open at metaphase and separates equationally during first anaphase. In the tetrad the two fragments regularly substitute the broken chromosome. The plants behave cytologically in the same way as the hybrids between diploid strains and naturally occurring endonuclear polyploids with half-sized chromosomes. In the next generation plants homozygote for the fragmented chromosome were found, showing a regular meiosis with two large and two small bivalents. The origin of the single fragmented chromosome in the irradiated material is difficult to explain; however, it was found earlier that chromosomes broken by x rays may persist as fragments in L. purpurea. It is noteworthy that the result of the fragmentation corresponds to the naturally occurring changes of chromosome pattern found in the genus Luzula. The pairing behavior of the chromosomes during meiosis in the heterozygote is the same as the one described for corresponding hybrids of L. campestris as well as the distribution of the large and the small chromosomes between the tetrad cells, where two half-sized chromosomes always substitute one large one. In such a case the progeny plants, homozygous for the fragmented chromosome, can give rise to a population which may be considered as an artificially produced endonuclear aneuploid strain, similar to the ones naturally found in the genus Luzula. (BBB)« less

Structure and Function of Centromeric and Pericentromeric Heterochromatin in Arabidopsis thaliana.

PubMed

Simon, Lauriane; Voisin, Maxime; Tatout, Christophe; Probst, Aline V

2015-01-01

The centromere is a specific chromosomal region where the kinetochore assembles to ensure the faithful segregation of sister chromatids during mitosis and meiosis. Centromeres are defined by a local enrichment of the specific histone variant CenH3 mostly at repetitive satellite sequences. A larger pericentromeric region containing repetitive sequences and transposable elements surrounds the centromere that adopts a particular chromatin state characterized by specific histone variants and post-translational modifications and forms a transcriptionally repressive chromosomal environment. In the model organism Arabidopsis thaliana centromeric and pericentromeric domains form conspicuous heterochromatin clusters called chromocenters in interphase. Here we discuss, using Arabidopsis as example, recent insight into mechanisms involved in maintenance and establishment of centromeric and pericentromeric chromatin signatures as well as in chromocenter formation.

Modeling of chromosome intermingling by partially overlapping uniform random polygons.

PubMed

Blackstone, T; Scharein, R; Borgo, B; Varela, R; Diao, Y; Arsuaga, J

2011-03-01

During the early phase of the cell cycle the eukaryotic genome is organized into chromosome territories. The geometry of the interface between any two chromosomes remains a matter of debate and may have important functional consequences. The Interchromosomal Network model (introduced by Branco and Pombo) proposes that territories intermingle along their periphery. In order to partially quantify this concept we here investigate the probability that two chromosomes form an unsplittable link. We use the uniform random polygon as a crude model for chromosome territories and we model the interchromosomal network as the common spatial region of two overlapping uniform random polygons. This simple model allows us to derive some rigorous mathematical results as well as to perform computer simulations easily. We find that the probability that one uniform random polygon of length n that partially overlaps a fixed polygon is bounded below by 1 − O(1/√n). We use numerical simulations to estimate the dependence of the linking probability of two uniform random polygons (of lengths n and m, respectively) on the amount of overlapping. The degree of overlapping is parametrized by a parameter [Formula: see text] such that [Formula: see text] indicates no overlapping and [Formula: see text] indicates total overlapping. We propose that this dependence relation may be modeled as f (ε, m, n) = [Formula: see text]. Numerical evidence shows that this model works well when [Formula: see text] is relatively large (ε ≥ 0.5). We then use these results to model the data published by Branco and Pombo and observe that for the amount of overlapping observed experimentally the URPs have a non-zero probability of forming an unsplittable link.

Isolation of the human chromosomal band Xq28 within somatic cell hybrids by fragile X site breakage.

PubMed Central

Warren, S T; Knight, S J; Peters, J F; Stayton, C L; Consalez, G G; Zhang, F P

1990-01-01

The chromosomal fragile-site mapping to Xq27.3 is associated with a frequent form of mental retardation and is prone to breakage after induced deoxyribonucleotide pool perturbation. The human hypoxanthine phosphoribosyltransferase (HPRT) and glucose-6-phosphate dehydrogenase (G6PD) genes flank the fragile X chromosome site and can be used to monitor integrity of the site in human-hamster somatic cell hybrids deficient in the rodent forms of these activities. After induction of the fragile X site, negative selection for HPRT and positive enrichment for G6PD resulted in 31 independent colonies of HPRT-,G6PD+ phenotype. Southern blot analysis demonstrated the loss of all tested markers proximal to the fragile X site with retention of all tested human Xq28 loci in a majority of the hybrids. In situ hybridization with a human-specific probe demonstrated the translocation of a small amount of human DNA to rodent chromosomes in these hybrids, suggesting chromosome breakage at the fragile X site and the subsequent translocation of Xq28. Southern blot hybridization of hybrid-cell DNA, resolved by pulsed-field gel electrophoresis, for human-specific repetitive sequences revealed abundant CpG-islands within Xq28, consistent with its known gene density. The electrophoretic banding patterns of human DNA among the hybrids were remarkably consistent, suggesting that fragile X site breakage is limited to a relatively small region in Xq27-28. These somatic cell hybrids, containing Xq27.3-qter as the sole human DNA, will aid the search for DNA associated with the fragile X site and will augment the high resolution genomic analysis of Xq28, including the identification of candidate genes for genetic-disease loci mapping to this region. Images PMID:2339126

Contrasting Levels of Molecular Evolution on the Mouse X Chromosome

PubMed Central

Larson, Erica L.; Vanderpool, Dan; Keeble, Sara; Zhou, Meng; Sarver, Brice A. J.; Smith, Andrew D.; Dean, Matthew D.; Good, Jeffrey M.

2016-01-01

The mammalian X chromosome has unusual evolutionary dynamics compared to autosomes. Faster-X evolution of spermatogenic protein-coding genes is known to be most pronounced for genes expressed late in spermatogenesis, but it is unclear if these patterns extend to other forms of molecular divergence. We tested for faster-X evolution in mice spanning three different forms of molecular evolution—divergence in protein sequence, gene expression, and DNA methylation—across different developmental stages of spermatogenesis. We used FACS to isolate individual cell populations and then generated cell-specific transcriptome profiles across different stages of spermatogenesis in two subspecies of house mice (Mus musculus), thereby overcoming a fundamental limitation of previous studies on whole tissues. We found faster-X protein evolution at all stages of spermatogenesis and faster-late protein evolution for both X-linked and autosomal genes. In contrast, there was less expression divergence late in spermatogenesis (slower late) on the X chromosome and for autosomal genes expressed primarily in testis (testis-biased). We argue that slower-late expression divergence reflects strong regulatory constraints imposed during this critical stage of sperm development and that these constraints are particularly acute on the tightly regulated sex chromosomes. We also found slower-X DNA methylation divergence based on genome-wide bisulfite sequencing of sperm from two species of mice (M. musculus and M. spretus), although it is unclear whether slower-X DNA methylation reflects development constraints in sperm or other X-linked phenomena. Our study clarifies key differences in patterns of regulatory and protein evolution across spermatogenesis that are likely to have important consequences for mammalian sex chromosome evolution, male fertility, and speciation. PMID:27317678

Disrupting Cyclin Dependent Kinase 1 in Spermatocytes Causes Late Meiotic Arrest and Infertility in Mice1

PubMed Central

Clement, Tracy M.; Inselman, Amy L.; Goulding, Eugenia H.; Willis, William D.; Eddy, Edward M.

2015-01-01

While cyclin dependent kinase 1 (CDK1) has a critical role in controlling resumption of meiosis in oocytes, its role has not been investigated directly in spermatocytes. Unique aspects of male meiosis led us to hypothesize that its role is different in male meiosis than in female meiosis. We generated a conditional knockout (cKO) of the Cdk1 gene in mouse spermatocytes to test this hypothesis. We found that CDK1-null spermatocytes undergo synapsis, chiasmata formation, and desynapsis as is seen in oocytes. Additionally, CDK1-null spermatocytes relocalize SYCP3 to centromeric foci, express H3pSer10, and initiate chromosome condensation. However, CDK1-null spermatocytes fail to form condensed bivalent chromosomes in prophase of meiosis I and instead are arrested at prometaphase. Thus, CDK1 has an essential role in male meiosis that is consistent with what is known about the role of CDK1 in female meiosis, where it is required for formation of condensed bivalent metaphase chromosomes and progression to the first meiotic division. We found that cKO spermatocytes formed fully condensed bivalent chromosomes in the presence of okadaic acid, suggesting that cKO chromosomes are competent to condense, although they do not do so in vivo. Additionally, arrested cKO spermatocytes exhibited irregular cell shape, irregular large nuclei, and large distinctive nucleoli. These cells persist in the seminiferous epithelium through the next seminiferous epithelial cycle with a lack of stage XII checkpoint-associated cell death. This indicates that CDK1 is required upstream of a checkpoint-associated cell death as well as meiotic metaphase progression in mouse spermatocytes. PMID:26490841

Dicentric breakage at telomere fusions

PubMed Central

Pobiega, Sabrina; Marcand, Stéphane

2010-01-01

Nonhomologous end-joining (NHEJ) inhibition at telomeres ensures that native chromosome ends do not fuse together. But the occurrence and consequences of rare telomere fusions are not well understood. It is notably unclear whether a telomere fusion could be processed to restore telomere ends. Here we address the behavior of individual dicentrics formed by telomere fusion in the yeast Saccharomyces cerevisiae. Our approach was to first stabilize and amplify fusions between two chromosomes by temporarily inactivating one centromere. Next we analyzed dicentric breakage following centromere reactivation. Unexpectedly, dicentrics often break at the telomere fusions during progression through mitosis, a process that restores the parental chromosomes. This unforeseen result suggests a rescue pathway able to process telomere fusions and to back up NHEJ inhibition at telomeres. PMID:20360388

Structure, evolution, and comparative genomics of tetraploid cotton based on a high-density genetic linkage map

PubMed Central

Li, Ximei; Jin, Xin; Wang, Hantao; Zhang, Xianlong; Lin, Zhongxu

2016-01-01

A high-density linkage map was constructed using 1,885 newly obtained loci and 3,747 previously published loci, which included 5,152 loci with 4696.03 cM in total length and 0.91 cM in mean distance. Homology analysis in the cotton genome further confirmed the 13 expected homologous chromosome pairs and revealed an obvious inversion on Chr10 or Chr20 and repeated inversions on Chr07 or Chr16. In addition, two reciprocal translocations between Chr02 and Chr03 and between Chr04 and Chr05 were confirmed. Comparative genomics between the tetraploid cotton and the diploid cottons showed that no major structural changes exist between DT and D chromosomes but rather between AT and A chromosomes. Blast analysis between the tetraploid cotton genome and the mixed genome of two diploid cottons showed that most AD chromosomes, regardless of whether it is from the AT or DT genome, preferentially matched with the corresponding homologous chromosome in the diploid A genome, and then the corresponding homologous chromosome in the diploid D genome, indicating that the diploid D genome underwent converted evolution by the diploid A genome to form the DT genome during polyploidization. In addition, the results reflected that a series of chromosomal translocations occurred among Chr01/Chr15, Chr02/Chr14, Chr03/Chr17, Chr04/Chr22, and Chr05/Chr19. PMID:27084896

Cytogenetic Features of Human Head and Body Lice (Phthiraptera: Pediculidae).

PubMed

Bressa, María José; Papeschi, Alba Graciela; Toloza, Ariel Ceferino

2015-09-01

The genus Pediculus L. that parasitize humans comprise two subspecies: the head lice Pediculus humanus capitis De Geer and the body lice Pediculus humanus humanus De Geer. Despite the 200 yr of the first description of these two species, there is still a long debate about their taxonomic status. Some authors proposed that these organisms are separate species, conspecifics, or grouped in clades. The sequencing of both forms indicated that the difference between them is one gene absent in the head louse. However, their chromosomal number remains to be determined. In this study, we described the male and female karyotypes, and male meiosis of head and body lice, and examined the chromatin structure by means of C-banding. In P. h. humanus and P. h. capitis, the diploid chromosome complement was 2 n = 12 in both sexes. In oogonial prometaphase and metaphase and spermatogonial metaphase, it is evident that chromosomes lack of a primary constriction. No identifiable sex chromosomes or B chromosomes were observed in head and body lice. Neither chiasmata nor chromatin connections between homologous chromosomes were detected in male meiosis. The meiotic behaviour of the chromosomes showed that they are holokinetic. C-banding revealed the absence of constitutive heterochromatin. Our results provide relevant information to be used in mapping studies of genes associated with sex determination and environmental sensing and response. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Preimplantation diagnosis of repeated miscarriage due to chromosomal translocations using metaphase chromosomes of a blastomere biopsied from 4- to 6-cell-stage embryos.

PubMed

Tanaka, Atsushi; Nagayoshi, Motoi; Awata, Shoichiro; Mawatari, Yoshifumi; Tanaka, Izumi; Kusunoki, Hiroshi

2004-01-01

To evaluate the safety and accuracy of karyotyping the blastomere chromosomes at metaphase in the natural cell cycle for preimplantation diagnosis. A pilot study. A private infertility clinic and a university laboratory. Eleven patients undergoing IVF and preimplantation diagnosis. Intact human embryos at the 4- to 6-cell stage and human-mouse heterokaryons were cultured and checked hourly for disappearance of the nuclear envelope. After it disappeared, the metaphase chromosomes were analyzed by fluorescence in situ hybridization. Percentage of analyzable metaphase plates and safety and accuracy of the method. The success rate of electrofusion to form human-mouse heterokaryons was 87.1% (27/31), and analyzable chromosomes were obtained from 77.4% (24/31) of the heterokaryons. On the other hand, disappearance of the nuclear envelope occurred in 89.5% (17/19) of the human embryos and it began earlier than that in the heterokaryons. Analyzable chromosomes were obtained and their translocation sites were identified in all blastomeres biopsied from the 17 embryos. After the biopsy, 67.0% of the embryos could develop to the blastocyst stage. The natural cell cycle method reported herein requires frequent observation, but it is safe, with no artificial effects on the chromosomes and without loss of or damage to blastomeres, which occurred with the electrofusion method. Using the natural cell cycle method, we could perform preimplantation diagnosis with nearly 100% accuracy.

Acquisition of Aneuploidy Provides Increased Fitness during the Evolution of Antifungal Drug Resistance

PubMed Central

Selmecki, Anna M.; Dulmage, Keely; Cowen, Leah E.; Anderson, James B.; Berman, Judith

2009-01-01

The evolution of drug resistance is an important process that affects clinical outcomes. Resistance to fluconazole, the most widely used antifungal, is often associated with acquired aneuploidy. Here we provide a longitudinal study of the prevalence and dynamics of gross chromosomal rearrangements, including aneuploidy, in the presence and absence of fluconazole during a well-controlled in vitro evolution experiment using Candida albicans, the most prevalent human fungal pathogen. While no aneuploidy was detected in any of the no-drug control populations, in all fluconazole-treated populations analyzed an isochromosome 5L [i(5L)] appeared soon after drug exposure. This isochromosome was associated with increased fitness in the presence of drug and, over time, became fixed in independent populations. In two separate cases, larger supernumerary chromosomes composed of i(5L) attached to an intact chromosome or chromosome fragment formed during exposure to the drug. Other aneuploidies, particularly trisomies of the smaller chromosomes (Chr3–7), appeared throughout the evolution experiment, and the accumulation of multiple aneuploid chromosomes per cell coincided with the highest resistance to fluconazole. Unlike the case in many other organisms, some isolates carrying i(5L) exhibited improved fitness in the presence, as well as in the absence, of fluconazole. The early appearance of aneuploidy is consistent with a model in which C. albicans becomes more permissive of chromosome rearrangements and segregation defects in the presence of fluconazole. PMID:19876375

Visually Tracking Translocations in Living Cells | Center for Cancer Research

Cancer.gov

Chromosomal translocations, the fusion of pieces of DNA from different chromosomes, are often observed in cancer cells and can even cause cancer. However, little is known about the dynamics and regulation of translocation formation. To investigate this critical process, Tom Misteli, Ph.D., in CCR’s Laboratory of Receptor Biology and Gene Expression, and his colleague Vassilis Roukos, Ph.D., developed a novel experimental system that allowed the researchers to see, for the first time, translocations form in individual, live cells.

The dominant Anopheles vectors of human malaria in Africa, Europe and the Middle East: occurrence data, distribution maps and bionomic précis

PubMed Central

2010-01-01

Background This is the second in a series of three articles documenting the geographical distribution of 41 dominant vector species (DVS) of human malaria. The first paper addressed the DVS of the Americas and the third will consider those of the Asian Pacific Region. Here, the DVS of Africa, Europe and the Middle East are discussed. The continent of Africa experiences the bulk of the global malaria burden due in part to the presence of the An. gambiae complex. Anopheles gambiae is one of four DVS within the An. gambiae complex, the others being An. arabiensis and the coastal An. merus and An. melas. There are a further three, highly anthropophilic DVS in Africa, An. funestus, An. moucheti and An. nili. Conversely, across Europe and the Middle East, malaria transmission is low and frequently absent, despite the presence of six DVS. To help control malaria in Africa and the Middle East, or to identify the risk of its re-emergence in Europe, the contemporary distribution and bionomics of the relevant DVS are needed. Results A contemporary database of occurrence data, compiled from the formal literature and other relevant resources, resulted in the collation of information for seven DVS from 44 countries in Africa containing 4234 geo-referenced, independent sites. In Europe and the Middle East, six DVS were identified from 2784 geo-referenced sites across 49 countries. These occurrence data were combined with expert opinion ranges and a suite of environmental and climatic variables of relevance to anopheline ecology to produce predictive distribution maps using the Boosted Regression Tree (BRT) method. Conclusions The predicted geographic extent for the following DVS (or species/suspected species complex*) is provided for Africa: Anopheles (Cellia) arabiensis, An. (Cel.) funestus*, An. (Cel.) gambiae, An. (Cel.) melas, An. (Cel.) merus, An. (Cel.) moucheti and An. (Cel.) nili*, and in the European and Middle Eastern Region: An. (Anopheles) atroparvus, An. (Ano.) labranchiae, An. (Ano.) messeae, An. (Ano.) sacharovi, An. (Cel.) sergentii and An. (Cel.) superpictus*. These maps are presented alongside a bionomics summary for each species relevant to its control. PMID:21129198

Small-scale field evaluation of push-pull system against early- and outdoor-biting malaria mosquitoes in an area of high pyrethroid resistance in Tanzania

PubMed Central

Mmbando, Arnold S.; Ngowo, Halfan S.; Kilalangongono, Masoud; Abbas, Said; Matowo, Nancy S.; Moore, Sarah J.; Okumu, Fredros O.

2017-01-01

Background: Despite high coverage of indoor interventions like insecticide-treated nets, mosquito-borne infections persist, partly because of outdoor-biting, early-biting and insecticide-resistant vectors. Push-pull systems, where mosquitoes are repelled from humans and attracted to nearby lethal targets, may constitute effective complementary interventions. Methods: A partially randomized cross-over design was used to test efficacy of push-pull in four experimental huts and four local houses, in an area with high pyrethroid resistance in Tanzania. The push-pull system consisted of 1.1% or 2.2% w/v transfluthrin repellent dispensers and an outdoor lure-and-kill device (odour-baited mosquito landing box). Matching controls were set up without push-pull. Adult male volunteers collected mosquitoes attempting to bite them outdoors, but collections were also done indoors using exit traps in experimental huts and by volunteers in the local houses. The collections were done hourly (1830hrs-0730hrs) and mosquito catches compared between push-pull and controls. An. gambiae s.l. and An. funestus s.l. were assessed by PCR to identify sibling species, and ELISA to detect Plasmodium falciparum and blood meal sources. Results: Push-pull in experimental huts reduced outdoor-biting for An. arabiensis and Mansonia species by 30% and 41.5% respectively. However, the reductions were marginal and insignificant for An. funestus (12.2%; p>0.05) and Culex (5%; p>0.05). Highest protection against all species occurred before 2200hrs. There was no significant difference in number of mosquitoes inside exit traps in huts with or without push-pull. In local households, push-pull significantly reduced indoor and outdoor-biting of An. arabiensis by 48% and 25% respectively, but had no effect on other species. Conclusion: This push-pull system offered modest protection against outdoor-biting An. arabiensis, without increasing indoor mosquito densities. Additional experimentation is required to assess how transfluthrin-based products affect mosquito blood-feeding and mortality in push-pull contexts. This approach, if optimised, could potentially complement existing malaria interventions even in areas with high pyrethroid resistance. PMID:29568808

Habitat suitability and ecological niche profile of major malaria vectors in Cameroon

PubMed Central

2009-01-01

Background Suitability of environmental conditions determines a species distribution in space and time. Understanding and modelling the ecological niche of mosquito disease vectors can, therefore, be a powerful predictor of the risk of exposure to the pathogens they transmit. In Africa, five anophelines are responsible for over 95% of total malaria transmission. However, detailed knowledge of the geographic distribution and ecological requirements of these species is to date still inadequate. Methods Indoor-resting mosquitoes were sampled from 386 villages covering the full range of ecological settings available in Cameroon, Central Africa. Using a predictive species distribution modeling approach based only on presence records, habitat suitability maps were constructed for the five major malaria vectors Anopheles gambiae, Anopheles funestus, Anopheles arabiensis, Anopheles nili and Anopheles moucheti. The influence of 17 climatic, topographic, and land use variables on mosquito geographic distribution was assessed by multivariate regression and ordination techniques. Results Twenty-four anopheline species were collected, of which 17 are known to transmit malaria in Africa. Ecological Niche Factor Analysis, Habitat Suitability modeling and Canonical Correspondence Analysis revealed marked differences among the five major malaria vector species, both in terms of ecological requirements and niche breadth. Eco-geographical variables (EGVs) related to human activity had the highest impact on habitat suitability for the five major malaria vectors, with areas of low population density being of marginal or unsuitable habitat quality. Sunlight exposure, rainfall, evapo-transpiration, relative humidity, and wind speed were among the most discriminative EGVs separating "forest" from "savanna" species. Conclusions The distribution of major malaria vectors in Cameroon is strongly affected by the impact of humans on the environment, with variables related to proximity to human settings being among the best predictors of habitat suitability. The ecologically more tolerant species An. gambiae and An. funestus were recorded in a wide range of eco-climatic settings. The other three major vectors, An. arabiensis, An. moucheti, and An. nili, were more specialized. Ecological niche and species distribution modelling should help improve malaria vector control interventions by targeting places and times where the impact on vector populations and disease transmission can be optimized. PMID:20028559

Habitat suitability and ecological niche profile of major malaria vectors in Cameroon.

PubMed

Ayala, Diego; Costantini, Carlo; Ose, Kenji; Kamdem, Guy C; Antonio-Nkondjio, Christophe; Agbor, Jean-Pierre; Awono-Ambene, Parfait; Fontenille, Didier; Simard, Frédéric

2009-12-23

Suitability of environmental conditions determines a species distribution in space and time. Understanding and modelling the ecological niche of mosquito disease vectors can, therefore, be a powerful predictor of the risk of exposure to the pathogens they transmit. In Africa, five anophelines are responsible for over 95% of total malaria transmission. However, detailed knowledge of the geographic distribution and ecological requirements of these species is to date still inadequate. Indoor-resting mosquitoes were sampled from 386 villages covering the full range of ecological settings available in Cameroon, Central Africa. Using a predictive species distribution modeling approach based only on presence records, habitat suitability maps were constructed for the five major malaria vectors Anopheles gambiae, Anopheles funestus, Anopheles arabiensis, Anopheles nili and Anopheles moucheti. The influence of 17 climatic, topographic, and land use variables on mosquito geographic distribution was assessed by multivariate regression and ordination techniques. Twenty-four anopheline species were collected, of which 17 are known to transmit malaria in Africa. Ecological Niche Factor Analysis, Habitat Suitability modeling and Canonical Correspondence Analysis revealed marked differences among the five major malaria vector species, both in terms of ecological requirements and niche breadth. Eco-geographical variables (EGVs) related to human activity had the highest impact on habitat suitability for the five major malaria vectors, with areas of low population density being of marginal or unsuitable habitat quality. Sunlight exposure, rainfall, evapo-transpiration, relative humidity, and wind speed were among the most discriminative EGVs separating "forest" from "savanna" species. The distribution of major malaria vectors in Cameroon is strongly affected by the impact of humans on the environment, with variables related to proximity to human settings being among the best predictors of habitat suitability. The ecologically more tolerant species An. gambiae and An. funestus were recorded in a wide range of eco-climatic settings. The other three major vectors, An. arabiensis, An. moucheti, and An. nili, were more specialized. Ecological niche and species distribution modelling should help improve malaria vector control interventions by targeting places and times where the impact on vector populations and disease transmission can be optimized.

Modulation of Prdm9-controlled meiotic chromosome asynapsis overrides hybrid sterility in mice.

PubMed

Gregorova, Sona; Gergelits, Vaclav; Chvatalova, Irena; Bhattacharyya, Tanmoy; Valiskova, Barbora; Fotopulosova, Vladana; Jansa, Petr; Wiatrowska, Diana; Forejt, Jiri

2018-03-14

Hybrid sterility is one of the reproductive isolation mechanisms leading to speciation. Prdm9 , the only known vertebrate hybrid-sterility gene, causes failure of meiotic chromosome synapsis and infertility in male hybrids that are the offspring of two mouse subspecies. Within species, Prdm9 determines the sites of programmed DNA double-strand breaks (DSBs) and meiotic recombination hotspots. To investigate the relation between Prdm9 -controlled meiotic arrest and asynapsis, we inserted random stretches of consubspecific homology on several autosomal pairs in sterile hybrids, and analyzed their ability to form synaptonemal complexes and to rescue male fertility. Twenty-seven or more megabases of consubspecific (belonging to the same subspecies) homology fully restored synapsis in a given autosomal pair, and we predicted that two or more DSBs within symmetric hotspots per chromosome are necessary for successful meiosis. We hypothesize that impaired recombination between evolutionarily diverged chromosomes could function as one of the mechanisms of hybrid sterility occurring in various sexually reproducing species. © 2018, Gregorova et al.

Modulation of Prdm9-controlled meiotic chromosome asynapsis overrides hybrid sterility in mice

PubMed Central

Chvatalova, Irena; Bhattacharyya, Tanmoy; Valiskova, Barbora; Fotopulosova, Vladana; Jansa, Petr; Wiatrowska, Diana

2018-01-01

Hybrid sterility is one of the reproductive isolation mechanisms leading to speciation. Prdm9, the only known vertebrate hybrid-sterility gene, causes failure of meiotic chromosome synapsis and infertility in male hybrids that are the offspring of two mouse subspecies. Within species, Prdm9 determines the sites of programmed DNA double-strand breaks (DSBs) and meiotic recombination hotspots. To investigate the relation between Prdm9-controlled meiotic arrest and asynapsis, we inserted random stretches of consubspecific homology on several autosomal pairs in sterile hybrids, and analyzed their ability to form synaptonemal complexes and to rescue male fertility. Twenty-seven or more megabases of consubspecific (belonging to the same subspecies) homology fully restored synapsis in a given autosomal pair, and we predicted that two or more DSBs within symmetric hotspots per chromosome are necessary for successful meiosis. We hypothesize that impaired recombination between evolutionarily diverged chromosomes could function as one of the mechanisms of hybrid sterility occurring in various sexually reproducing species. PMID:29537370

The murine ufo receptor: molecular cloning, chromosomal localization and in situ expression analysis.

PubMed

Faust, M; Ebensperger, C; Schulz, A S; Schleithoff, L; Hameister, H; Bartram, C R; Janssen, J W

1992-07-01

We have cloned the mouse homologue of the ufo oncogene. It encodes a novel tyrosine kinase receptor characterized by a unique extracellular domain containing two immunoglobulin-like and two fibronectin type III repeats. Comparison of the predicted ufo amino acid sequences of mouse and man revealed an overall identity of 87.6%. The ufo locus maps to mouse chromosome 7A3-B1 and thereby extends the known conserved linkage group between mouse chromosome 7 and human chromosome 19. RNA in situ hybridization analysis established the onset of specific ufo expression in the late embryogenesis at day 12.5 post coitum (p.c.) and localized ufo transcription to distinct substructures of a broad spectrum of developing tissues (e.g. subepidermal cells of the skin, mesenchymal cells of the periosteum). In adult animals ufo is expressed in cells forming organ capsules as well as in connective tissue structures. ufo may function as a signal transducer between specific cell types of mesodermal origin.

Inactivation of a centromere during the formation of a translocation in maize.

PubMed

Gao, Zhi; Fu, Shulan; Dong, Qianhua; Han, Fangpu; Birchler, James A

2011-08-01

Fluorescence in situ hybridization analysis of a reciprocal translocation in maize between chromosomes 1 and 5 that has been used extensively in maize genetics revealed the presence of an inactive centromere at or near the breakpoints of the two chromosomes. This centromere contains both the satellite repeat, CentC, and the centromeric retrotransposon family, CRM, that are typical of centromere regions in maize. This site does not exhibit any of the tested biochemical features of active centromeres such as association with CENP-C and phosphorylation of serine-10 on histone H3. The most likely scenario for this chromosome arrangement is that a centromere was included in the repair process that formed the translocation but became inactive and has been inherited in this state for several decades. The documentation of an inactive A chromosome centromere in maize extends the evidence for an epigenetic component to centromere function in plants. This case provides an experimental example of how karyotype evolution might proceed via changes in centromere inactivation.

A disassembly-driven mechanism explains F-actin-mediated chromosome transport in starfish oocytes

PubMed Central

Bun, Philippe; Dmitrieff, Serge; Belmonte, Julio M

2018-01-01

While contraction of sarcomeric actomyosin assemblies is well understood, this is not the case for disordered networks of actin filaments (F-actin) driving diverse essential processes in animal cells. For example, at the onset of meiosis in starfish oocytes a contractile F-actin network forms in the nuclear region transporting embedded chromosomes to the assembling microtubule spindle. Here, we addressed the mechanism driving contraction of this 3D disordered F-actin network by comparing quantitative observations to computational models. We analyzed 3D chromosome trajectories and imaged filament dynamics to monitor network behavior under various physical and chemical perturbations. We found no evidence of myosin activity driving network contractility. Instead, our observations are well explained by models based on a disassembly-driven contractile mechanism. We reconstitute this disassembly-based contractile system in silico revealing a simple architecture that robustly drives chromosome transport to prevent aneuploidy in the large oocyte, a prerequisite for normal embryonic development. PMID:29350616

Clonality in myeloproliferative disorders: Analysis by means of polymerase chain reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gilliland, D.G.; Blanchard, K.L.; Levy, J.

1991-08-01

The myeloproliferative syndromes are acquired disorders of hematopoiesis that provide insights into the transition from somatic cell mutation to neoplasia. The clonal origin of specific blood cells can be assessed in patients with X chromosome-linked polymorphisms, taking advantage of random inactivation of the X chromosome. The authors have adapted the PCR for determination of clonality on as few as 100 cells, including individual colonies grown in culture. Amplifying a polymorphic portion of the X chromosome-linked phosphoglycerate kinase (PGK) gene after selective digestion of the active X chromosome with a methylation-sensitive restriction enzyme gave results fully concordant with standard Southern blottingmore » of DNA samples form normal (polyclonal) polymorphonuclear cells (PMN) as well as clonal PMN from patients with myelodysplastic syndrome and polycythemia vera (PCV). They have used this technique to demonstrate heterogeneity of lineage involvement in patients with PCV. The same clinical phenotype may arise from clonal proliferation of different hematopoietic progenitors.« less

Karyotypic Characteristics of the Ornithophilic Simulium aureum Species Group (Diptera: Simuliidae) Along the Northern Black Sea Coast and the Origin of Chromosomal Reduction.

PubMed

Vlasov, Sergey; Adler, Peter H; Topolenko, Varvara; Aibulatov, Sergey; Gorlov, Ivan; Harutyunova, Maria; Harutyunova, Karine

2018-05-03

The Simulium aureum group (Diptera: Simuliidae), also known as subgenus Eusimulium Roubaud, is a monophyletic, Holarctic taxon of bird-feeding black flies with a reduced chromosome number of two and remarkably similar external structure in all life stages. We analyzed the banding patterns of the polytene chromosomes to understand the composition of this species group along the northern coast of the Black Sea where two little-known nominal species have their type localities. Our analyses link the names Simulium krymense (Rubtsov) and Simulium maritimum (Rubtsov) with unique chromosomal characters, indicate that both are male chiasmate, and reveal the presence of Simulium angustipes Edwards along the northern coast of the Black Sea for the first time. We show that S. krymense has a banding sequence most similar to the hypothesized ancestral form of the S. aureum group, and that the entire group is derived from within the Simulium vernum group, rendering the latter group and its encompassing subgenus, Nevermannia Enderlein, paraphyletic.

Unusual chromosomal organization of telomeric sequences and expeditious karyotypic differentiation in the recently evolved Mus terricolor complex.

PubMed

Sharma, G G; Sharma, T

1998-01-01

The Mus terricolor complex displays a stable homozygous arrangement of autosomal heterochromatin variations in the form of accretion of definitive autosomal short arms among three nonoverlapping populations, in concert with an expeditious evolutionary differentiation into three chromosomal species: M. terricolor I, II, and III. In contrast to the highly conservative M. musculus-like chromosomes in the coexisting sibling species, M. booduga, reshuffling and differentiation of centric heterochromatin has occurred in harmony with a revision of centric configurations, resulting in acrocentric and submetacentric autosomes. The chromosomal distribution of the prevalent vertebrate telomeric sequence (TTAGGG)n was examined by fluorescence in situ hybridization to metaphase cells of M. terricolor I, II, and III. An unusual centric organization of internal telomeric sequences was detected in all the submetacentric and acrocentric autosomes. An auxiliary role of these presumably fragile, recombinogenic telomeric sequences in the evolutionary revision of centric configurations in the terricolor complex is hypothesized.

The chromosome axis controls meiotic events through a hierarchical assembly of HORMA domain proteins

PubMed Central

Kim, Yumi; Rosenberg, Scott C.; Kugel, Christine L.; Kostow, Nora; Rog, Ofer; Davydov, Vitaliy; Su, Tiffany Y.; Dernburg, Abby F.; Corbett, Kevin D.

2014-01-01

Summary Proteins of the HORMA domain family play central but poorly understood roles in chromosome organization and dynamics during meiosis. In C. elegans, four such proteins (HIM-3, HTP-1, HTP-2, and HTP-3) have distinct but overlapping functions. Through combined biochemical, structural, and in vivo analysis, we find that these proteins form hierarchical complexes through binding of their HORMA domains to cognate peptides within their partners’ C-terminal tails, analogous to the “safety belt” binding mechanism of Mad2. These interactions are critical for recruitment of HIM-3, HTP-1, and HTP-2 to chromosome axes. HTP-3, in addition to recruiting the other HORMA domain proteins to the axis, plays an independent role in sister chromatid cohesion and double-strand break formation. Finally, we find that mammalian HORMAD1 binds a peptide motif found both at its own C-terminus and that of HORMAD2, indicating that this mode of intermolecular association is a conserved feature of meiotic chromosome structure in eukaryotes. PMID:25446517

Cannabis extract treatment for terminal acute lymphoblastic leukemia with a Philadelphia chromosome mutation.

PubMed

Singh, Yadvinder; Bali, Chamandeep

2013-09-01

Acute lymphoblastic leukemia (ALL) is a cancer of the white blood cells and is typically well treated with combination chemotherapy, with a remission state after 5 years of 94% in children and 30-40% in adults. To establish how aggressive the disease is, further chromosome testing is required to determine whether the cancer is myeloblastic and involves neutrophils, eosinophils or basophils, or lymphoblastic involving B or T lymphocytes. This case study is on a 14-year-old patient diagnosed with a very aggressive form of ALL (positive for the Philadelphia chromosome mutation). A standard bone marrow transplant, aggressive chemotherapy and radiation therapy were revoked, with treatment being deemed a failure after 34 months. Without any other solutions provided by conventional approaches aside from palliation, the family administered cannabinoid extracts orally to the patient. Cannabinoid resin extract is used as an effective treatment for ALL with a positive Philadelphia chromosome mutation and indications of dose-dependent disease control. The clinical observation in this study revealed a rapid dose-dependent correlation.

Chromosome stickiness impairs meiosis and influences reproductive success in Panicum maximum (Poaceae) hybrid plants.

PubMed

Pessim, C; Pagliarini, M S; Silva, N; Jank, L

2015-04-28

Chromosome stickiness has been studied in several species of higher plants and is characterized by sticky clumps of chromatin resulting in sterility. Chromosome stickiness was recorded in Panicum maximum hybrid plants that were cultivated in the field. In the meiocytes affected, chromosomes clumped into amorphous masses that did not orient themselves on the equatorial plate, and anaphase I disjunction failed to occur. After a normal cytokinesis, the masses of chromatin were divided between both daughter cells. Metaphase and anaphase of the second division also did not occur, and after the second cytokinesis, polyads were formed. This abnormality arose spontaneously. Abnormalities that cause male sterility are an important tool for obtaining hybrid seeds in plant breeding. This is the first report of an abnormality affecting pollen viability in P. maximum. This finding can open a new opportunity in the breeding program of this species that is devoted to hybridization where manual cross-pollination is difficult and time consuming.

Human Matrix Attachment Regions Are Necessary for the Establishment but Not the Maintenance of Transgene Insulation in Drosophila melanogaster

PubMed Central

Namciu, Stephanie J.; Fournier, R. E. K.

2004-01-01

Human matrix attachment regions (MARs) can insulate transgene expression from chromosomal position effects in Drosophila melanogaster. To gain insight into the mechanism(s) by which chromosomal insulation occurs, we studied the expression phenotypes of Drosophila transformants expressing mini-white transgenes in which MAR sequences from the human apoB gene were arranged in a variety of ways. In agreement with previous reports, we found that a single copy of the insulating element was not sufficient for position-independent transgene expression; rather, two copies were required. However, the arrangement of the two elements within the transgene was unimportant, since chromosomal insulation was equally apparent when both copies of the insulator were upstream of the mini-white reporter as when the transcription unit was flanked by insulator elements. Moreover, experiments in which apoB 3′ MAR sequences were removed from integrated transgenes in vivo by site-specific recombination demonstrated that MAR sequences were required for the establishment but not for the maintenance of chromosomal insulation. These observations are not compatible with the chromosomal loop model in its simplest form. Alternate mechanisms for MAR function in this system are proposed. PMID:15542833

Cohesin-interacting protein WAPL-1 regulates meiotic chromosome structure and cohesion by antagonizing specific cohesin complexes

PubMed Central

Crawley, Oliver; Barroso, Consuelo; Testori, Sarah; Ferrandiz, Nuria; Silva, Nicola; Castellano-Pozo, Maikel; Jaso-Tamame, Angel Luis; Martinez-Perez, Enrique

2016-01-01

Wapl induces cohesin dissociation from DNA throughout the mitotic cell cycle, modulating sister chromatid cohesion and higher-order chromatin structure. Cohesin complexes containing meiosis-specific kleisin subunits govern most aspects of meiotic chromosome function, but whether Wapl regulates these complexes remains unknown. We show that during C. elegans oogenesis WAPL-1 antagonizes binding of cohesin containing COH-3/4 kleisins, but not REC-8, demonstrating that sensitivity to WAPL-1 is dictated by kleisin identity. By restricting the amount of chromosome-associated COH-3/4 cohesin, WAPL-1 controls chromosome structure throughout meiotic prophase. In the absence of REC-8, WAPL-1 inhibits COH-3/4-mediated cohesion, which requires crossover-fated events formed during meiotic recombination. Thus, WAPL-1 promotes functional specialization of meiotic cohesin: WAPL-1-sensitive COH-3/4 complexes modulate higher-order chromosome structure, while WAPL-1-refractory REC-8 complexes provide stable cohesion. Surprisingly, a WAPL-1-independent mechanism removes cohesin before metaphase I. Our studies provide insight into how meiosis-specific cohesin complexes are regulated to ensure formation of euploid gametes. DOI: http://dx.doi.org/10.7554/eLife.10851.001 PMID:26841696

Cell cycle stage-specific differential expression of topoisomerase I in tobacco BY-2 cells and its ectopic overexpression and knockdown unravels its crucial role in plant morphogenesis and development.

PubMed

Singh, Badri Nath; Mudgil, Yashwanti; John, Riffat; Achary, V Mohan Murali; Tripathy, Manas Kumar; Sopory, Sudhir K; Reddy, Malireddy K; Kaul, Tanushri

2015-11-01

DNA topoisomerases catalyze the inter-conversion of different topological forms of DNA. Cell cycle coupled differential accumulation of topoisomerase I (Topo I) revealed biphasic expression maximum at S-phase and M/G1-phase of cultured synchronized tobacco BY-2 cells. This suggested its active role in resolving topological constrains during DNA replication (S-phase) and chromosome decondensation (M/G1 phase). Immuno-localization revealed high concentrations of Topo I in nucleolus. Propidium iodide staining and Br-UTP incorporation patterns revealed direct correlation between immunofluorescence intensity and rRNA transcription activity within nucleolus. Immuno-stained chromosomes during metaphase and anaphase suggested possible role of Topo I in resolving topological constrains during mitotic chromosome condensation. Inhibitor studies showed that in comparison to Topo I, Topo II was essential in resolving topological constrains during chromosome condensation. Probably, Topo II substituted Topo I functioning to certain extent during chromosome condensation, but not vice-versa. Transgenic Topo I tobacco lines revealed morphological abnormalities and highlighted its crucial role in plant morphogenesis and development. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Differential expression of non-coding RNAs and continuous evolution of the X chromosome in testicular transcriptome of two mouse species.

PubMed

Homolka, David; Ivanek, Robert; Forejt, Jiri; Jansa, Petr

2011-02-14

Tight regulation of testicular gene expression is a prerequisite for male reproductive success, while differentiation of gene activity in spermatogenesis is important during speciation. Thus, comparison of testicular transcriptomes between closely related species can reveal unique regulatory patterns and shed light on evolutionary constraints separating the species. Here, we compared testicular transcriptomes of two closely related mouse species, Mus musculus and Mus spretus, which diverged more than one million years ago. We analyzed testicular expression using tiling arrays overlapping Chromosomes 2, X, Y and mitochondrial genome. An excess of differentially regulated non-coding RNAs was found on Chromosome 2 including the intronic antisense RNAs, intergenic RNAs and premature forms of Piwi-interacting RNAs (piRNAs). Moreover, striking difference was found in the expression of X-linked G6pdx gene, the parental gene of the autosomal retrogene G6pd2. The prevalence of non-coding RNAs among differentially expressed transcripts indicates their role in species-specific regulation of spermatogenesis. The postmeiotic expression of G6pdx in Mus spretus points towards the continuous evolution of X-chromosome silencing and provides an example of expression change accompanying the out-of-the X-chromosomal retroposition.

ScII: an abundant chromosome scaffold protein is a member of a family of putative ATPases with an unusual predicted tertiary structure

PubMed Central

1994-01-01

Here, we describe the cloning and characterization of ScII, the second most abundant protein after topoisomerase II, of the chromosome scaffold fraction to be identified. ScII is structurally related to a protein, Smc1p, previously found to be required for accurate chromosome segregation in Saccharomyces cerevisiae. ScII and the other members of the emerging family of SMC1-like proteins are likely to be novel ATPases, with NTP-binding A and B sites separated by two lengthy regions predicted to form an alpha-helical coiled-coil. Analysis of the ScII B site predicted that ScII might use ATP by a mechanism similar to the bacterial recN DNA repair and recombination enzyme. ScII is a mitosis-specific scaffold protein that colocalizes with topoisomerase II in mitotic chromosomes. However, ScII appears not to be associated with the interphase nuclear matrix. ScII might thus play a role in mitotic processes such as chromosome condensation or sister chromatid disjunction, both of which have been previously shown to involve topoisomerase II. PMID:7929577

Microorganisms associated with chromosome destruction and reproductive isolation between two insect species.

PubMed

Breeuwer, J A; Werren, J H

1990-08-09

Microorganisms have been implicated in causing cytoplasmic incompatibility in a variety of insect species, including mosquitoes, fruitflies, beetles and wasps. The effect is typically unidirectional: incompatible crosses produce no progeny or sterile males, whereas the reciprocal crosses produce normal progeny. The parasitic wasp Nasonia vitripennis is one of the few species in which the cytogenetic mechanism of incompatibility is known. In this species the paternal chromosome set forms a tangled mass in a fertilized egg and is eventually lost. Here we report that cytoplasmic microorganisms are associated with complete bidirectional incompatibility between N. vitripennis and a closely related sympatric species, N. giraulti. Microorganisms can be seen in the eggs of both species. Hybrid offspring are normally not produced in crosses between the two species, but do occur after elimination of the microorganisms by antibiotic treatment. A cytogenetic and genetic study shows that bidirectional interspecific incompatibility is due to improper condensation of the paternal chromosomes. Microorganism-mediated reproductive isolation is of interest because it could provide a rapid mode of speciation. The mechanism of incompatibility in Nasonia is also of interest as a potential tool for studying chromosome imprinting and chromosome condensation.

Lack of response to unaligned chromosomes in mammalian female gametes

PubMed Central

Sebestova, Jaroslava; Danylevska, Anna; Novakova, Lucia; Kubelka, Michal; Anger, Martin

2012-01-01

Chromosome segregation errors are highly frequent in mammalian female meiosis, and their incidence gradually increases with maternal age. The fate of aneuploid eggs is obviously dependent on the stringency of mechanisms for detecting unattached or repairing incorrectly attached kinetochores. In case of their failure, the newly formed embryo will inherit the impaired set of chromosomes, which will have severe consequences for its further development. Whether spindle assembly checkpoint (SAC) in oocytes is capable of arresting cell cycle progression in response to unaligned kinetochores was discussed for a long time. It is known that abolishing SAC increases frequency of chromosome segregation errors and causes precocious entry into anaphase; SAC, therefore, seems to be essential for normal chromosome segregation in meiosis I. However, it was also reported that for anaphase-promoting complex (APC) activation, which is a prerequisite for entering anaphase; alignment of only a critical mass of kinetochores on equatorial plane is sufficient. This indicates that the function of SAC and of cooperating chromosome attachment correction mechanisms in oocytes is different from somatic cells. To analyze this phenomenon, we used live cell confocal microscopy to monitor chromosome movements, spindle formation, APC activation and polar body extrusion (PBE) simultaneously in individual oocytes at various time points during first meiotic division. Our results, using oocytes from aged animals and interspecific crosses, demonstrate that multiple unaligned kinetochores and severe congression defects are tolerated at the metaphase to anaphase transition, although such cells retain sensitivity to nocodazole. This indicates that checkpoint mechanisms, operating in oocytes at this point, are essential for accurate timing of APC activation in meiosis I, but they are insufficient in detection or correction of unaligned chromosomes, preparing thus conditions for propagation of the aneuploidy to the embryo. PMID:22871737

Mouse HFM1/Mer3 Is Required for Crossover Formation and Complete Synapsis of Homologous Chromosomes during Meiosis

PubMed Central

Guiraldelli, Michel F.; Eyster, Craig; Wilkerson, Joseph L.; Dresser, Michael E.; Pezza, Roberto J.

2013-01-01

Faithful chromosome segregation during meiosis requires that homologous chromosomes associate and recombine. Chiasmata, the cytological manifestation of recombination, provide the physical link that holds the homologs together as a pair, facilitating their orientation on the spindle at meiosis I. Formation of most crossover (CO) events requires the assistance of a group of proteins collectively known as ZMM. HFM1/Mer3 is in this group of proteins and is required for normal progression of homologous recombination and proper synapsis between homologous chromosomes in a number of model organisms. Our work is the first study in mammals showing the in vivo function of mouse HFM1. Cytological observations suggest that initial steps of recombination are largely normal in a majority of Hfm1−/− spermatocytes. Intermediate and late stages of recombination appear aberrant, as chromosomal localization of MSH4 is altered and formation of MLH1foci is drastically reduced. In agreement, chiasma formation is reduced, and cells arrest with subsequent apoptosis at diakinesis. Our results indicate that deletion of Hfm1 leads to the elimination of a major fraction but not all COs. Formation of chromosome axial elements and homologous pairing is apparently normal, and Hfm1−/− spermatocytes progress to the end of prophase I without apparent developmental delay or apoptosis. However, synapsis is altered with components of the central region of the synaptonemal complex frequently failing to extend the full length of the chromosome axes. We propose that initial steps of recombination are sufficient to support homology recognition, pairing, and initial chromosome synapsis and that HFM1 is required to form normal numbers of COs and to complete synapsis. PMID:23555294

The Status of Dosage Compensation in the Multiple X Chromosomes of the Platypus

PubMed Central

Deakin, Janine E.; Hore, Timothy A.; Koina, Edda; Marshall Graves, Jennifer A.

2008-01-01

Dosage compensation has been thought to be a ubiquitous property of sex chromosomes that are represented differently in males and females. The expression of most X-borne genes is equalized between XX females and XY males in therian mammals (marsupials and “placentals”) by inactivating one X chromosome in female somatic cells. However, compensation seems not to be strictly required to equalize the expression of most Z-borne genes between ZZ male and ZW female birds. Whether dosage compensation operates in the third mammal lineage, the egg-laying monotremes, is of considerable interest, since the platypus has a complex sex chromosome system in which five X and five Y chromosomes share considerable genetic homology with the chicken ZW sex chromosome pair, but not with therian XY chromosomes. The assignment of genes to four platypus X chromosomes allowed us to examine X dosage compensation in this unique species. Quantitative PCR showed a range of compensation, but SNP analysis of several X-borne genes showed that both alleles are transcribed in a heterozygous female. Transcription of 14 BACs representing 19 X-borne genes was examined by RNA-FISH in female and male fibroblasts. An autosomal control gene was expressed from both alleles in nearly all nuclei, and four pseudoautosomal BACs were usually expressed from both alleles in male as well as female nuclei, showing that their Y loci are active. However, nine X-specific BACs were usually transcribed from only one allele. This suggests that while some genes on the platypus X are not dosage compensated, other genes do show some form of compensation via stochastic transcriptional inhibition, perhaps representing an ancestral system that evolved to be more tightly controlled in placental mammals such as human and mouse. PMID:18654631

The status of dosage compensation in the multiple X chromosomes of the platypus.

PubMed

Deakin, Janine E; Hore, Timothy A; Koina, Edda; Marshall Graves, Jennifer A

2008-07-25

Dosage compensation has been thought to be a ubiquitous property of sex chromosomes that are represented differently in males and females. The expression of most X-borne genes is equalized between XX females and XY males in therian mammals (marsupials and "placentals") by inactivating one X chromosome in female somatic cells. However, compensation seems not to be strictly required to equalize the expression of most Z-borne genes between ZZ male and ZW female birds. Whether dosage compensation operates in the third mammal lineage, the egg-laying monotremes, is of considerable interest, since the platypus has a complex sex chromosome system in which five X and five Y chromosomes share considerable genetic homology with the chicken ZW sex chromosome pair, but not with therian XY chromosomes. The assignment of genes to four platypus X chromosomes allowed us to examine X dosage compensation in this unique species. Quantitative PCR showed a range of compensation, but SNP analysis of several X-borne genes showed that both alleles are transcribed in a heterozygous female. Transcription of 14 BACs representing 19 X-borne genes was examined by RNA-FISH in female and male fibroblasts. An autosomal control gene was expressed from both alleles in nearly all nuclei, and four pseudoautosomal BACs were usually expressed from both alleles in male as well as female nuclei, showing that their Y loci are active. However, nine X-specific BACs were usually transcribed from only one allele. This suggests that while some genes on the platypus X are not dosage compensated, other genes do show some form of compensation via stochastic transcriptional inhibition, perhaps representing an ancestral system that evolved to be more tightly controlled in placental mammals such as human and mouse.

Developing de novo human artificial chromosomes in embryonic stem cells using HSV-1 amplicon technology.

PubMed

Moralli, Daniela; Monaco, Zoia L

2015-02-01

De novo artificial chromosomes expressing genes have been generated in human embryonic stem cells (hESc) and are maintained following differentiation into other cell types. Human artificial chromosomes (HAC) are small, functional, extrachromosomal elements, which behave as normal chromosomes in human cells. De novo HAC are generated following delivery of alpha satellite DNA into target cells. HAC are characterized by high levels of mitotic stability and are used as models to study centromere formation and chromosome organisation. They are successful and effective as gene expression vectors since they remain autonomous and can accommodate larger genes and regulatory regions for long-term expression studies in cells unlike other viral gene delivery vectors currently used. Transferring the essential DNA sequences for HAC formation intact across the cell membrane has been challenging for a number of years. A highly efficient delivery system based on HSV-1 amplicons has been used to target DNA directly to the ES cell nucleus and HAC stably generated in human embryonic stem cells (hESc) at high frequency. HAC were detected using an improved protocol for hESc chromosome harvesting, which consistently produced high-quality metaphase spreads that could routinely detect HAC in hESc. In tumour cells, the input DNA often integrated in the host chromosomes, but in the host ES genome, it remained intact. The hESc containing the HAC formed embryoid bodies, generated teratoma in mice, and differentiated into neuronal cells where the HAC were maintained. The HAC structure and chromatin composition was similar to the endogenous hESc chromosomes. This review will discuss the technological advances in HAC vector delivery using HSV-1 amplicons and the improvements in the identification of de novo HAC in hESc.

The evolution of vertebrate somatostatin receptors and their gene regions involves extensive chromosomal rearrangements

PubMed Central

2012-01-01

Background Somatostatin and its related neuroendocrine peptides have a wide variety of physiological functions that are mediated by five somatostatin receptors with gene names SSTR1-5 in mammals. To resolve their evolution in vertebrates we have investigated the SSTR genes and a large number of adjacent gene families by phylogeny and conserved synteny analyses in a broad range of vertebrate species. Results We find that the SSTRs form two families that belong to distinct paralogons. We observe not only chromosomal similarities reflecting the paralogy relationships between the SSTR-bearing chromosome regions, but also extensive rearrangements between these regions in teleost fish genomes, including fusions and translocations followed by reshuffling through intrachromosomal rearrangements. These events obscure the paralogy relationships but are still tractable thanks to the many genomes now available. We have identified a previously unrecognized SSTR subtype, SSTR6, previously misidentified as either SSTR1 or SSTR4. Conclusions Two ancestral SSTR-bearing chromosome regions were duplicated in the two basal vertebrate tetraploidizations (2R). One of these ancestral SSTR genes generated SSTR2, -3 and -5, the other gave rise to SSTR1, -4 and -6. Subsequently SSTR6 was lost in tetrapods and SSTR4 in teleosts. Our study shows that extensive chromosomal rearrangements have taken place between related chromosome regions in teleosts, but that these events can be resolved by investigating several distantly related species. PMID:23194088

Deletion of DXZ4 on the human inactive X chromosome alters higher-order genome architecture.

PubMed

Darrow, Emily M; Huntley, Miriam H; Dudchenko, Olga; Stamenova, Elena K; Durand, Neva C; Sun, Zhuo; Huang, Su-Chen; Sanborn, Adrian L; Machol, Ido; Shamim, Muhammad; Seberg, Andrew P; Lander, Eric S; Chadwick, Brian P; Aiden, Erez Lieberman

2016-08-02

During interphase, the inactive X chromosome (Xi) is largely transcriptionally silent and adopts an unusual 3D configuration known as the "Barr body." Despite the importance of X chromosome inactivation, little is known about this 3D conformation. We recently showed that in humans the Xi chromosome exhibits three structural features, two of which are not shared by other chromosomes. First, like the chromosomes of many species, Xi forms compartments. Second, Xi is partitioned into two huge intervals, called "superdomains," such that pairs of loci in the same superdomain tend to colocalize. The boundary between the superdomains lies near DXZ4, a macrosatellite repeat whose Xi allele extensively binds the protein CCCTC-binding factor. Third, Xi exhibits extremely large loops, up to 77 megabases long, called "superloops." DXZ4 lies at the anchor of several superloops. Here, we combine 3D mapping, microscopy, and genome editing to study the structure of Xi, focusing on the role of DXZ4 We show that superloops and superdomains are conserved across eutherian mammals. By analyzing ligation events involving three or more loci, we demonstrate that DXZ4 and other superloop anchors tend to colocate simultaneously. Finally, we show that deleting DXZ4 on Xi leads to the disappearance of superdomains and superloops, changes in compartmentalization patterns, and changes in the distribution of chromatin marks. Thus, DXZ4 is essential for proper Xi packaging.

Autophagy is required for efficient meiosis progression and proper meiotic chromosome segregation in fission yeast.

PubMed

Matsuhara, Hirotada; Yamamoto, Ayumu

2016-01-01

Autophagy is a conserved intracellular degradation system, which contributes to development and differentiation of various organisms. Yeast cells undergo meiosis under nitrogen-starved conditions and require autophagy for meiosis initiation. However, the precise roles of autophagy in meiosis remain unclear. Here, we show that autophagy is required for efficient meiosis progression and proper meiotic chromosome segregation in fission yeast. Autophagy-defective strains bearing a mutation in the autophagy core factor gene atg1, atg7, or atg14 exhibit deformed nuclear structures during meiosis. These mutant cells require an extracellular nitrogen supply for meiosis progression following their entry into meiosis and show delayed meiosis progression even with a nitrogen supply. In addition, they show frequent chromosome dissociation from the spindle together with spindle overextension, forming extra nuclei. Furthermore, Aurora kinase, which regulates chromosome segregation and spindle elongation, is significantly increased at the centromere and spindle in the mutant cells. Aurora kinase down-regulation eliminated delayed initiation of meiosis I and II, chromosome dissociation, and spindle overextension, indicating that increased Aurora kinase activity may cause these aberrances in the mutant cells. Our findings show a hitherto unrecognized relationship of autophagy with the nuclear structure, regulation of cell cycle progression, and chromosome segregation in meiosis. © 2015 The Molecular Biology Society of Japan and Wiley Publishing Asia Pty Ltd.

Epigenetic Characteristics of the Mitotic Chromosome in 1D and 3D

PubMed Central

Oomen, Marlies E.; Dekker, Job

2017-01-01

While chromatin characteristics in interphase are widely studied, characteristics of mitotic chromatin and their inheritance through mitosis are still poorly understood. During mitosis chromatin undergoes dramatic changes: Transcription stalls, chromatin binding factors leave the chromatin, histone modifications change and chromatin becomes highly condensed. Many key insights into mitotic chromosome state and conformation have come from extensive microscopy studies over the last century. Over the last decade the development of 3C-based techniques has enabled the study of higher order chromosome organization during mitosis in a genome-wide manner. During mitosis chromosomes lose their cell type specific and locus-dependent chromatin organization that characterizes interphase chromatin and fold into randomly positioned loop arrays. Upon exit of mitosis cells are capable of quickly rearranging the chromosome conformation to form the cell type specific interphase organization again. The information that enables this rearrangement after mitotic exit is thought to be encoded at least in part in mitotic bookmarks, e.g. histone modifications and variants, histone remodelers, chromatin factors and non-coding RNA. Here we give an overview of the chromosomal organization and epigenetic characteristics of the interphase and mitotic chromatin in vertebrates. Second, we describe different ways in which mitotic bookmarking enables epigenetic memory of the features of the interphase chromatin through mitosis. And third, we explore the role of epigenetic modifications and mitotic bookmarking in cell differentiation. PMID:28228067

Social chromosome variants differentially affect queen determination and the survival of workers in the fire ant Solenopsis invicta.

PubMed

Buechel, Séverine D; Wurm, Yanick; Keller, Laurent

2014-10-01

Intraspecific variation in social organization is common, yet the underlying causes are rarely known. An exception is the fire ant Solenopsis invicta in which the existence of two distinct forms of social colony organization is under the control of the two variants of a pair of social chromosomes, SB and Sb. Colonies containing exclusively SB/SB workers accept only one single queen and she must be SB/SB. By contrast, when colonies contain more than 10% of SB/Sb workers, they accept several queens but only SB/Sb queens. The variants of the social chromosome are associated with several additional important phenotypic differences, including the size, fecundity and dispersal strategies of queens, aggressiveness of workers, and sperm count in males. However, little is known about whether social chromosome variants affect fitness in other life stages. Here, we perform experiments to determine whether differential selection occurs during development and in adult workers. We find evidence that the Sb variant of the social chromosome increases the likelihood of female brood to develop into queens and that adult SB/Sb workers, the workers that cull SB/SB queens, are overrepresented in comparison to SB/SB workers. This demonstrates that supergenes such as the social chromosome can have complex effects on phenotypes at various stages of development. © 2014 John Wiley & Sons Ltd.

The cnm locus, a canine homologue of human autosomal forms of centronuclear myopathy, maps to chromosome 2.

PubMed

Tiret, Laurent; Blot, Stéphane; Kessler, Jean-Louis; Gaillot, Hugues; Breen, Matthew; Panthier, Jean-Jacques

2003-09-01

Myotubular/centronuclear myopathies are a nosological group of hereditary disorders characterised by severe architectural and metabolic remodelling of skeletal muscle fibres. In most myofibres, nuclei are found at an abnormal central position within a halo devoid of myofibrillar proteins. The X-linked form (myotubular myopathy) is the most prevalent and severe form in human, leading to death during early postnatal life. Maturation of fibres is not completed and fibres resemble myotubes. Linkage analysis in human has helped to identify MTM1 as the morbid gene. MTM1 encodes myotubularin, a dual protein phosphatase. In families in which myotubular myopathy segregates, detected mutations in MTM1 abolish the specific phosphatase activity targeting the second messenger phosphatidylinositol 3-phosphate. Autosomal forms (centronuclear) have a later onset and are often compatible with life. At birth, fibres are normally constituted but progressively follow remodelling with a secondary centralisation of nuclei. Their prevalence is low; hence, no linkage data can be performed and no molecular aetiology is known. In the Labrador Retriever, a spontaneous disorder strikingly mimics the clinical evolution of the human centronuclear myopathy. We have established a canine pedigree and show that the disorder segregates as an autosomal recessive trait in that pedigree. We have further mapped the dog locus to a region on chromosome 2 that is orthologous to human chromosome 10p. To date, no human MTM1 gene member has been mapped to this genetic region. This report thus describes the first spontaneous mammalian model of centronuclear myopathy and defines a new locus for this group of diseases.

Stable DNA replication: interplay between DNA replication, homologous recombination, and transcription.

PubMed

Kogoma, T

1997-06-01

Chromosome replication in Escherichia coli is normally initiated at oriC, the origin of chromosome replication. E. coli cells possess at least three additional initiation systems for chromosome replication that are normally repressed but can be activated under certain specific conditions. These are termed the stable DNA replication systems. Inducible stable DNA replication (iSDR), which is activated by SOS induction, is proposed to be initiated from a D-loop, an early intermediate in homologous recombination. Thus, iSDR is a form of recombination-dependent DNA replication (RDR). Analysis of iSDR and RDR has led to the proposal that homologous recombination and double-strand break repair involve extensive semiconservative DNA replication. RDR is proposed to play crucial roles in homologous recombination, double-strand break repair, restoration of collapsed replication forks, and adaptive mutation. Constitutive stable DNA replication (cSDR) is activated in mhA mutants deficient in RNase HI or in recG mutants deficient in RecG helicase. cSDR is proposed to be initiated from an R-loop that can be formed by the invasion of duplex DNA by an RNA transcript, which most probably is catalyzed by RecA protein. The third form of SDR is nSDR, which can be transiently activated in wild-type cells when rapidly growing cells enter the stationary phase. This article describes the characteristics of these alternative DNA replication forms and reviews evidence that has led to the formulation of the proposed models for SDR initiation mechanisms. The possible interplay between DNA replication, homologous recombination, DNA repair, and transcription is explored.

UBF-binding site arrays form pseudo-NORs and sequester the RNA polymerase I transcription machinery

PubMed Central

Mais, Christine; Wright, Jane E.; Prieto, José-Luis; Raggett, Samantha L.; McStay, Brian

2005-01-01

Human ribosomal genes (rDNA) are located in nucleolar organizer regions (NORs) on the short arms of acrocentric chromosomes. Metaphase NORs that were transcriptionally active in the previous cell cycle appear as prominent chromosomal features termed secondary constrictions that are achromatic in chromosome banding and positive in silver staining. The architectural RNA polymerase I (pol I) transcription factor UBF binds extensively across rDNA throughout the cell cycle. To determine if UBF binding underpins NOR structure, we integrated large arrays of heterologous UBF-binding sequences at ectopic sites on human chromosomes. These arrays efficiently recruit UBF even to sites outside the nucleolus and, during metaphase, form novel silver stainable secondary constrictions, termed pseudo-NORs, morphologically similar to NORs. We demonstrate for the first time that in addition to UBF the other components of the pol I machinery are found associated with sequences across the entire human rDNA repeat. Remarkably, a significant fraction of these same pol I factors are sequestered by pseudo-NORs independent of both transcription and nucleoli. Because of the heterologous nature of the sequence employed, we infer that sequestration is mediated primarily by protein–protein interactions with UBF. These results suggest that extensive binding of UBF is responsible for formation and maintenance of the secondary constriction at active NORs. Furthermore, we propose that UBF mediates recruitment of the pol I machinery to nucleoli independently of promoter elements. PMID:15598984

Fragile DNA Motifs Trigger Mutagenesis at Distant Chromosomal Loci in Saccharomyces cerevisiae

PubMed Central

Saini, Natalie; Zhang, Yu; Nishida, Yuri; Sheng, Ziwei; Choudhury, Shilpa; Mieczkowski, Piotr; Lobachev, Kirill S.

2013-01-01

DNA sequences capable of adopting non-canonical secondary structures have been associated with gross-chromosomal rearrangements in humans and model organisms. Previously, we have shown that long inverted repeats that form hairpin and cruciform structures and triplex-forming GAA/TTC repeats induce the formation of double-strand breaks which trigger genome instability in yeast. In this study, we demonstrate that breakage at both inverted repeats and GAA/TTC repeats is augmented by defects in DNA replication. Increased fragility is associated with increased mutation levels in the reporter genes located as far as 8 kb from both sides of the repeats. The increase in mutations was dependent on the presence of inverted or GAA/TTC repeats and activity of the translesion polymerase Polζ. Mutagenesis induced by inverted repeats also required Sae2 which opens hairpin-capped breaks and initiates end resection. The amount of breakage at the repeats is an important determinant of mutations as a perfect palindromic sequence with inherently increased fragility was also found to elevate mutation rates even in replication-proficient strains. We hypothesize that the underlying mechanism for mutagenesis induced by fragile motifs involves the formation of long single-stranded regions in the broken chromosome, invasion of the undamaged sister chromatid for repair, and faulty DNA synthesis employing Polζ. These data demonstrate that repeat-mediated breaks pose a dual threat to eukaryotic genome integrity by inducing chromosomal aberrations as well as mutations in flanking genes. PMID:23785298

Fine genetic mapping of a gene for autosomal recessive retinitis pigmentosa on chromosome 6p21

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shugart, Yin Y.; Banerjee, P.; Knowles, J.A.

1995-08-01

The inherited retinal degenerations known as retinitis pigmentosa (RP) can be caused by mutations at many different loci and can be inherited as an autosomal recessive, autosomal dominant, or X-linked recessive trait. Two forms of autosomal recessive (arRP) have been reported to cosegregate with mutations in the rhodopsin gene and the beta-subunit of rod phosphodiesterase on chromosome 4p. Genetic linkage has been reported on chromosomes 6p and 1q. In a large Dominican family, we reported an arRp gene near the region of the peripherin/RDS gene. Four recombinations were detected between the disease locus and an intragenic marker derived from peripherin/RDS.more » 26 refs., 2 figs., 1 tab.« less

Molecular cytogenetic identification of a novel wheat-Agropyron elongatum chromosome translocation line with powdery mildew resistance.

PubMed

Li, Xiaojun; Jiang, Xiaoling; Chen, Xiangdong; Song, Jie; Ren, Cuicui; Xiao, Yajuan; Gao, Xiaohui; Ru, Zhengang

2017-01-01

Agropyron elongatum (Host.) Neviski (synonym, Thinopyrum ponticum Podp., 2n = 70) has been used extensively as a valuable source for wheat breeding. Numerous chromosome fragments containing valuable genes have been successfully translocated into wheat from A. elongatum. However, reports on the transfer of powdery mildew resistance from A. elongatum to wheat are rare. In this study, a novel wheat-A. elongatum translocation line, 11-20-1, developed and selected from the progenies of a sequential cross between wheat varieties (Lankaoaizaoba, Keyu 818 and BainongAK 58) and A. elongatum, was evaluated for disease resistance and characterized using molecular cytogenetic methods. Cytological observations indicated that 11-20-1 had 42 chromosomes and formed 21 bivalents at meiotic metaphase I. Genomic in situ hybridization analysis using whole genomic DNA from A. elongatum as a probe showed that the short arms of a pair of wheat chromosomes were replaced by a pair of A. elongatum chromosome arms. Fluorescence in situ hybridization, using wheat D chromosome specific sequence pAs1 as a probe, suggested that the replaced chromosome arms of 11-20-1 were 5DS. This was further confirmed by wheat SSR markers specific for 5DS. EST-SSR and EST-STS multiple loci markers confirmed that the introduced A. elongatum chromosome arms belonged to homoeologous group 5. Therefore, it was deduced that 11-20-1 was a wheat-A. elongatum T5DL∙5AgS translocation line. Both resistance observation and molecular marker analyses using two specific markers (BE443538 and CD452608) of A. elongatum in a F2 population from a cross between line 11-20-1 and a susceptible cultivar Yannong 19 verified that the A. elongatum chromosomes were responsible for the powdery mildew resistance. This work suggests that 11-20-1 likely contains a novel resistance gene against powdery mildew. We expect this line to be useful for the genetic improvement of wheat.

Cytological maps of lampbrush chromosomes of European water frogs (Pelophylax esculentus complex) from the Eastern Ukraine

PubMed Central

2013-01-01

Background Hybridogenesis (hemiclonal inheritance) is a kind of clonal reproduction in which hybrids between parental species are reproduced by crossing with one of the parental species. European water frogs (Pelophylax esculentus complex) represent an appropriate model for studying interspecies hybridization, processes of hemiclonal inheritance and polyploidization. P. esculentus complex consists of two parental species, P. ridibundus (the lake frog) and P. lessonae (the pool frog), and their hybridogenetic hybrid – P. esculentus (the edible frog). Parental and hybrid frogs can reproduce syntopically and form hemiclonal population systems. For studying mechanisms underlying the maintenance of water frog population systems it is required to characterize the karyotypes transmitted in gametes of parental and different hybrid animals of both sexes. Results In order to obtain an instrument for characterization of oocyte karyotypes in hybrid female frogs, we constructed cytological maps of lampbrush chromosomes from oocytes of both parental species originating in Eastern Ukraine. We further identified certain molecular components of chromosomal marker structures and mapped coilin-rich spheres and granules, chromosome associated nucleoli and special loops accumulating splicing factors. We recorded the dissimilarities between P. ridibundus and P. lessonae lampbrush chromosomes in the length of orthologous chromosomes, number and location of marker structures and interstitial (TTAGGG)n-repeat sites as well as activity of nucleolus organizer. Satellite repeat RrS1 was mapped in centromere regions of lampbrush chromosomes of the both species. Additionally, we discovered transcripts of RrS1 repeat in oocytes of P. ridibundus and P. lessonae. Moreover, G-rich transcripts of telomere repeat were revealed in association with terminal regions of P. ridibundus and P. lessonae lampbrush chromosomes. Conclusions The constructed cytological maps of lampbrush chromosomes of P. ridibundus and P. lessonae provide basis to define the type of genome transmitted within individual oocytes of P. esculentus females with different ploidy and from various population systems. PMID:23590698

Molecular cytogenetic identification of a novel wheat-Agropyron elongatum chromosome translocation line with powdery mildew resistance

PubMed Central

Jiang, Xiaoling; Chen, Xiangdong; Song, Jie; Ren, Cuicui; Xiao, Yajuan; Gao, Xiaohui; Ru, Zhengang

2017-01-01

Agropyron elongatum (Host.) Neviski (synonym, Thinopyrum ponticum Podp., 2n = 70) has been used extensively as a valuable source for wheat breeding. Numerous chromosome fragments containing valuable genes have been successfully translocated into wheat from A. elongatum. However, reports on the transfer of powdery mildew resistance from A. elongatum to wheat are rare. In this study, a novel wheat-A. elongatum translocation line, 11-20-1, developed and selected from the progenies of a sequential cross between wheat varieties (Lankaoaizaoba, Keyu 818 and BainongAK 58) and A. elongatum, was evaluated for disease resistance and characterized using molecular cytogenetic methods. Cytological observations indicated that 11-20-1 had 42 chromosomes and formed 21 bivalents at meiotic metaphase I. Genomic in situ hybridization analysis using whole genomic DNA from A. elongatum as a probe showed that the short arms of a pair of wheat chromosomes were replaced by a pair of A. elongatum chromosome arms. Fluorescence in situ hybridization, using wheat D chromosome specific sequence pAs1 as a probe, suggested that the replaced chromosome arms of 11-20-1 were 5DS. This was further confirmed by wheat SSR markers specific for 5DS. EST-SSR and EST-STS multiple loci markers confirmed that the introduced A. elongatum chromosome arms belonged to homoeologous group 5. Therefore, it was deduced that 11-20-1 was a wheat-A. elongatum T5DL∙5AgS translocation line. Both resistance observation and molecular marker analyses using two specific markers (BE443538 and CD452608) of A. elongatum in a F2 population from a cross between line 11-20-1 and a susceptible cultivar Yannong 19 verified that the A. elongatum chromosomes were responsible for the powdery mildew resistance. This work suggests that 11-20-1 likely contains a novel resistance gene against powdery mildew. We expect this line to be useful for the genetic improvement of wheat. PMID:28886152

mBAND Analysis of Late Chromosome Aberrations in Human Lymphocytes Induced by Gamma Rays and Fe Ions

NASA Technical Reports Server (NTRS)

Sunagawa, Mayumi; Zhang, Ye; Yeshitla, Samrawit; Kadhim, Munira; Wilson, Bobby; Wu, Honglu

2014-01-01

Chromosomal translocations and inversions are considered stable, and cells containing these types of chromosome aberrations can survive multiple cell divisions. An efficient method to detect an inversion is multi-color banding fluorescent in situ hybridization (mBAND) which allows identification of both inter- and intrachromosome aberrations simultaneously. Post irradiation, chromosome aberrations may also arise after multiple cell divisions as a result of genomic instability. To investigate the stable or late-arising chromosome aberrations induced after radiation exposure, we exposed human lymphocytes to gamma rays and Fe ions ex vivo, and cultured the cells for multiple generations. Chromosome aberrations were analyzed in cells collected at first mitosis and at several time intervals during the culture period post irradiation. With gamma irradiation, about half of the damages observed at first mitosis remained after 7 day- and 14 day- culture, suggesting the transmissibility of damages to the surviving progeny. Detailed analysis of chromosome break ends participating in exchanges revealed a greater fraction of break ends involved in intrachromosome aberrations in the 7- and 14-day samples in comparison to the fraction at first mitosis. In particular, simple inversions were found at 7 and 14 days, but not at the first mitosis, suggesting that some of the aberrations might be formed days post irradiation. In contrast, at the doses that produced similar frequencies of gamma-induced chromosome aberrations as observed at first mitosis, a significantly lower yield of aberrations remained at the same population doublings after Fe ion exposure. At these equitoxic doses, more complex type aberrations were observed for Fe ions, indicating that Fe ion-induced initial chromosome damages are more severe and may lead to cell death. Comparison between low and high doses of Fe ion irradiation in the induction of late damages will also be discussed.

Evolutionary history of the third chromosome gene arrangements of Drosophila pseudoobscura inferred from inversion breakpoints.

PubMed

Wallace, Andre G; Detweiler, Don; Schaeffer, Stephen W

2011-08-01

The third chromosome of Drosophila pseudoobscura is polymorphic for numerous gene arrangements that form classical clines in North America. The polytene salivary chromosomes isolated from natural populations revealed changes in gene order that allowed the different gene arrangements to be linked together by paracentric inversions representing one of the first cases where genetic data were used to construct a phylogeny. Although the inversion phylogeny can be used to determine the relationships among the gene arrangements, the cytogenetic data are unable to infer the ancestral arrangement or the age of the different chromosome types. These are both important properties if one is to infer the evolutionary forces responsible for the spread and maintenance of the chromosomes. Here, we employ the nucleotide sequences of 18 regions distributed across the third chromosome in 80-100 D. pseudoobscura strains to test whether five gene arrangements are of unique or multiple origin, what the ancestral arrangement was, and what are the ages of the different arrangements. Each strain carried one of six commonly found gene arrangements and the sequences were used to infer their evolutionary relationships. Breakpoint regions in the center of the chromosome supported monophyly of the gene arrangements, whereas regions at the ends of the chromosome gave phylogenies that provided less support for monophyly of the chromosomes either because the individual markers did not have enough phylogenetically informative sites or genetic exchange scrambled information among the gene arrangements. A data set where the genetic markers were concatenated strongly supported a unique origin of the different gene arrangements. The inversion polymorphism of D. pseudoobscura is estimated to be about a million years old. We have also shown that the generated phylogeny is consistent with the cytological phylogeny of this species. In addition, the data presented here support hypothetical as the ancestral arrangement. One of the youngest arrangements, Arrowhead, has one of the highest population frequencies suggesting that selection has been responsible for its rapid increase.

METHYLATED TRIVALENT ARSENICALS AS CANDIDATE ULTIMATE GENOTOXIC FORMS OF ARSENIC: INDUCTION OF CHROMOSOMAL MUTATIONS BUT NOT GENE MUTATIONS

EPA Science Inventory

ABSTRACT
Arsenic is a prevalent human carcinogen whose mutagenicity has not been characterized fully. Exposure to either form of inorganic arsenic, AsIII or AsV, can result in the formation of at least four organic metabolites: monomethylarsonic acid, monomethylarsonous aci...

Localization of phosphorylated forms of Bcl-2 in mitosis: co-localization with Ki-67 and nucleolin in nuclear structures and on mitotic chromosomes.

PubMed

Barboule, Nadia; Truchet, Isabelle; Valette, Annie

2005-04-01

Bcl-2 phosphorylation is a normal physiological process occurring at mitosis or during mitotic arrest induced by microtubule damaging agents. The consequences of Bcl-2 phosphorylation on its function are still controversial. To better understand the role of Bcl-2 phosphorylation in mitosis, we studied the subcellular localization of phosphorylated forms of Bcl-2. Immunofluorescence experiments performed in synchronized HeLa cells indicate for the first time that mitotic phosphorylated forms of Bcl-2 can be detected in nuclear structures in prophase cells together with nucleolin and Ki-67. In later mitotic stages, as previously described, phosphorylated forms of Bcl-2 are localized on mitotic chromosomes. In addition, we demonstrate that Bcl-2 in these structures is at least in part phosphorylated on the T56 residue. Then, coimmunoprecipitation experiments reveal that, in cells synchronized at the onset of mitosis, Bcl-2 is present in a complex with nucleolin, cdc2 kinase and PP1 phosphatase. Taken together, these data further support the idea that Bcl-2 could have a new function at mitosis.

Structure, evolution, and comparative genomics of tetraploid cotton based on a high-density genetic linkage map.

PubMed

Li, Ximei; Jin, Xin; Wang, Hantao; Zhang, Xianlong; Lin, Zhongxu

2016-06-01

A high-density linkage map was constructed using 1,885 newly obtained loci and 3,747 previously published loci, which included 5,152 loci with 4696.03 cM in total length and 0.91 cM in mean distance. Homology analysis in the cotton genome further confirmed the 13 expected homologous chromosome pairs and revealed an obvious inversion on Chr10 or Chr20 and repeated inversions on Chr07 or Chr16. In addition, two reciprocal translocations between Chr02 and Chr03 and between Chr04 and Chr05 were confirmed. Comparative genomics between the tetraploid cotton and the diploid cottons showed that no major structural changes exist between DT and D chromosomes but rather between AT and A chromosomes. Blast analysis between the tetraploid cotton genome and the mixed genome of two diploid cottons showed that most AD chromosomes, regardless of whether it is from the AT or DT genome, preferentially matched with the corresponding homologous chromosome in the diploid A genome, and then the corresponding homologous chromosome in the diploid D genome, indicating that the diploid D genome underwent converted evolution by the diploid A genome to form the DT genome during polyploidization. In addition, the results reflected that a series of chromosomal translocations occurred among Chr01/Chr15, Chr02/Chr14, Chr03/Chr17, Chr04/Chr22, and Chr05/Chr19. © The Author 2016. Published by Oxford University Press on behalf of Kazusa DNA Research Institute.

Karyotype evolution of giraffes (Giraffa camelopardalis) revealed by cross-species chromosome painting with Chinese muntjac (Muntiacus reevesi) and human (Homo sapiens) paints.

PubMed

Huang, L; Nesterenko, A; Nie, W; Wang, J; Su, W; Graphodatsky, A S; Yang, F

2008-01-01

Considering the giraffe (Giraffa camelopardalis, GCA, 2n = 30) as a primitive species, its comparative genomic data are critical for our understanding of the karyotype evolution of pecorans. Here, we have established genome-wide chromosomal homologies between giraffe, Chinese muntjac (Muntiacus reevesi, MRE, 2n = 46) and human (Homo sapiens, HSA, 2n = 46) with whole sets of chromosome-specific paints from Chinese muntjac and human, in addition to providing a high-resolution G-banding karyotype of giraffe. Chinese muntjac and human chromosome paints detected 32 and 45 autosomal homologs in the genome of giraffe, respectively. Our results suggest that it would require at least thirteen fissions, six fusions and three intrachromosomal rearrangements to 'transform' the 2n = 44 eutherian ancestral karyotype to the 2n = 58 pecoran ancestral karyotype. During giraffe evolution, some ancestral eutherian syntenies (i.e. association of HSA3/21, 4/8, 7/16, 14/15, 16/19 and two forms of 12/22) have been retained, while several derived syntenies (i.e. associations of human homologous segments 2/1, 2/9, 5/19, 4/12/22, 8/9, and 10/20) have been produced. The reduction of chromosome number in giraffe from the 2n = 58 pecoran ancestral karyotype could be primarily attributed to extensive Robertsonian translocations of ancestral chromosomal segments. More complex chromosomal rearrangements (including tandem fusion, centromere repositioning and pericentric inversion) have happened during the evolution of GCA2 and GCA8. Copyright 2008 S. Karger AG, Basel.

Changes in nucleoid morphology and origin localization upon inhibition or alteration of the actin homolog, MreB, of Vibrio cholerae.

PubMed

Srivastava, Preeti; Demarre, Gäelle; Karpova, Tatiana S; McNally, James; Chattoraj, Dhruba K

2007-10-01

MreB is an actin homolog required for the morphogenesis of most rod-shaped bacteria and for other functions, including chromosome segregation. In Caulobacter crescentus and Escherichia coli, the protein seems to play a role in the segregation of sister origins, but its role in Bacillus subtilis chromosome segregation is less clear. To help clarify its role in segregation, we have here studied the protein in Vibrio cholerae, whose chromosome I segregates like the one in C. crescentus and whose chromosome II like the one in E. coli or B. subtilis. The properties of Vibrio MreB were similar to those of its homologs in other bacteria in that it formed dynamic helical filaments, was essential for viability, and was inhibited by the drug A22. Wild-type (WT) cells exposed to A22 became spherical and larger. The nucleoids enlarged correspondingly, and the origin positions for both the chromosomes no longer followed any fixed pattern. However, the sister origins separated, unlike the situation in other bacteria. In mutants isolated as A22 resistant, the nucleoids in some cases appeared compacted even when the cell shape was nearly normal. In these cells, the origins of chromosome I were at the distal edges of the nucleoid but not all the way to the poles where they normally reside. The sister origins of chromosome II also separated less. Thus, it appears that the inhibition or alteration of Vibrio MreB can affect both the nucleoid morphology and origin localization.

[Comparative organization and the origin of noncoding regulatory RNA genes from X-chromosome inactivation center of human and mouse].

PubMed

Kolesnikov, N N; Elisafenko, E A

2010-10-01

After the radiation of primates and rodents, the evolution of X-chromosome inactivation centers in human and mouse (XIC/Xic) followed two different directions. Human XIC followed the pathway towards transposon accumulation (the repeat proportion in the center constitutes 72%), especially LINEs, which prevail in the center. On the contrary, mouse Xic eliminated long repeats and accumulated species-specific SIN Es (the repeat proportion in the center constitutes 35%). The mechanism underlying inactivation of one of the X chromosomes in female mammals appeared on the basis of trasnsposons. The key gene of the inactivation process, XIST/Xist, similarly to other long noncoding RNA genes, like TSIX/Tsix, JPX/Jpx, and FTX/Ftx, was formed with the involvement of different transposon sequences. Furthermore, two clusters ofmicroRNA genes from inactivation center originated from L2 [1]. In mouse, one of such clusters has been preserved in the form of microRNA pseudogenes. Thus, long ncRNA genes and microRNAs appeared during the period of transposable elements expansion in this locus, 140 to 105 Myr ago, after the radiation of marsupials and placental mammal lineages.

Mechanisms and consequences of aneuploidy and chromosome instability in the aging brain

PubMed Central

Andriani, Grasiella A.; Vijg, Jan; Montagna, Cristina

2017-01-01

Aneuploidy and polyploidy are a form of Genomic Instability (GIN) known as Chromosomal Instability (CIN) characterized by sporadic abnormalities in chromosome copy numbers. Aneuploidy is commonly linked to pathological states. It is a hallmark of spontaneous abortions and birth defects and it is observed virtually in every human tumor, therefore being generally regarded as detrimental for the development or the maturation of tissues under physiological conditions. Polyploidy however, occurs as part of normal physiological processes during maturation and differentiation of some mammalian cell types. Surprisingly, high levels of aneuploidy are present in the brain, and their frequency increases with age suggesting that the brain is able to maintain its functionality in the presence of high levels of mosaic aneuploidy. Because somatic aneuploidy with age can reach exceptionally high levels, it is likely to have long-term adverse effects in this organ. We describe the mechanisms accountable for an abnormal DNA content with a particular emphasis on the CNS where cell division is limited. Next, we briefly summarize the types of GIN known to date and discuss how they interconnect with CIN. Lastly we highlight how several forms of CIN may contribute to genetic variation, tissue degeneration and disease in the CNS. PMID:27013377

The activities of eukaryotic replication origins in chromatin.

PubMed

Weinreich, Michael; Palacios DeBeer, Madeleine A; Fox, Catherine A

2004-03-15

DNA replication initiates at chromosomal positions called replication origins. This review will focus on the activity, regulation and roles of replication origins in Saccharomyces cerevisiae. All eukaryotic cells, including S. cerevisiae, depend on the initiation (activity) of hundreds of replication origins during a single cell cycle for the duplication of their genomes. However, not all origins are identical. For example, there is a temporal order to origin activation with some origins firing early during the S-phase and some origins firing later. Recent studies provide evidence that posttranslational chromatin modifications, heterochromatin-binding proteins and nucleosome positioning can control the efficiency and/or timing of chromosomal origin activity in yeast. Many more origins exist than are necessary for efficient replication. The availability of excess replication origins leaves individual origins free to evolve distinct forms of regulation and/or roles in chromosomes beyond their fundamental role in DNA synthesis. We propose that some origins have acquired roles in controlling chromatin structure and/or gene expression. These roles are not linked obligatorily to replication origin activity per se, but instead exploit multi-subunit replication proteins with the potential to form context-dependent protein-protein interactions.

Localization of a Susceptibility Gene for Familial Nonmedullary Thyroid Carcinoma to Chromosome 2q21

PubMed Central

McKay, James D.; Lesueur, Fabienne; Jonard, Laurence; Pastore, Alessandro; Williamson, Jan; Hoffman, Linda; Burgess, John; Duffield, Anne; Papotti, Mauro; Stark, Markus; Sobol, Hagay; Maes, Béatrice; Murat, Arnaud; Kääriäinen, Helena; Bertholon-Grégoire, Mireille; Zini, Michele; Rossing, Mary Anne; Toubert, Marie-Elisabeth; Bonichon, Françoise; Cavarec, Marie; Bernard, Anne-Marie; Boneu, Andrée; Leprat, Frédéric; Haas, Oskar; Lasset, Christine; Schlumberger, Martin; Canzian, Federico; Goldgar, David E.; Romeo, Giovanni

2001-01-01

The familial form of nonmedullary thyroid carcinoma (NMTC) is a complex genetic disorder characterized by multifocal neoplasia and a higher degree of aggressiveness than its sporadic counterpart. In a large Tasmanian pedigree (Tas1) with recurrence of papillary thyroid carcinoma (PTC), the most common form of NMTC, an extensive genomewide scan revealed a common haplotype on chromosome 2q21 in seven of the eight patients with PTC. To verify the significance of the 2q21 locus, we performed linkage analysis in an independent sample set of 80 pedigrees, yielding a multipoint heterogeneity LOD score (HLOD) of 3.07 (α=0.42), nonparametric linkage (NPL) 3.19, (P=.001) at marker D2S2271. Stratification based on the presence of at least one case of the follicular variant of PTC, the phenotype observed in the Tas1 family, identified 17 such pedigrees, yielding a maximal HLOD score of 4.17 (α=0.80) and NPL=4.99 (P=.00002) at markers AFMa272zg9 and D2S2271, respectively. These results indicate the existence of a susceptibility locus for familial NMTC on chromosome 2q21. PMID:11438887

Effects of hydrostatic pressure on microtubule organization and nucleus changes in gynogenetically activated eggs of olive flounder (Paralichthys olivaceus).

PubMed

Lin, Zhengmei; Zhu, Xiangping; Zhang, Tingrong; You, Feng; Wu, Zhihao; Cao, Yuanshui

2016-06-01

Fluorescent double-labeled technique was used to investigate the effects of hydrostatic pressure on microtubule organization and nucleus in gynogenetically activated eggs of olive flounder (Paralichthys olivaceus). The parameter of hydrostatic pressure treatment was 600 kg/cm(2) for 6 minutes at prometaphase of the first mitosis. The data showed that nucleus and microtubule changes of the diploid control were basically similar to those of the haploid one (5 minutes behind those of the diploid control). Nuclear diameter of the haploid embryo was significantly smaller than that of the diploid one (P < 0.01). The ploidy of chromosome set could be determined basing on nuclear diameter. The results of nuclear diameter measurement and the ratio of developmentally delayed embryo showed that the chromosome set was not doubled during the second cell cycle, the first cleavage proceeded normally; but that of about 80% treated embryo was doubled during the third cell cycle, the second cleavage was inhibited. Microtubules were disassembled, and nucleation capacity of centrosome was just temporarily inhibited by pressure treatment. Centrosome renucleated microtubule, and a bipolar spindle reassembled 15 minutes after treatment, leading to occurrence of the first cleavage. During the second cell cycle, about 80% treated embryo had a single centrosome and formed a unipolar spindle in both blastomeres. After prometaphase, chromosomes spread around for about 20 minutes instead of aligning on the equatorial plane, then assembled and formed one large nucleus without anaphase separation. The second cleavage was inhibited, and the chromosome set was doubled. The data indicated that the chromosome set doubling of mitogynogenetic diploid induced by hydrostatic pressure treatment, which performed at prometaphase of the first mitosis, mainly resulted from the inhibition of the second cleavage rather than the first one. This study is the first to adapt fluorescent double-labeled technique to investigate the mechanism on chromosome set doubling of mitotic gynogenesis induction. This study will offer theoretical support for mitogynogenetic diploid induction in marine fish. Copyright © 2016 Elsevier Inc. All rights reserved.

Genetic heterogeneity in familial exudative vitreoretinopathy; exclusion of the EVR1 locus on chromosome 11q in a large autosomal dominant pedigree.

PubMed

Bamashmus, M A; Downey, L M; Inglehearn, C F; Gupta, S R; Mansfield, D C

2000-04-01

Familial exudative vitreoretinopathy (FEVR) is associated with mutations in the Norrie disease gene in X linked pedigrees and with linkage to the EVR1 locus at 11q13 in autosomal dominant cases. A large autosomal dominant FEVR family was studied, both clinically and by linkage analysis, to determine whether it differed from the known forms of FEVR. Affected members and obligate gene carriers from this family were examined by slit lamp biomicroscopy, indirect ophthalmoscopy, and in some cases fluorescein angiography. Patient DNAs were genotyped for markers at the EVR1 locus on chromosome 11q13. The clinical evaluation in this family is consistent with previous descriptions of FEVR pedigrees, but linkage analysis proves that it has a form of FEVR genetically distinct from the EVR1 locus on 11q. This proves that there are at least three different loci associated with comparable FEVR phenotypes, a situation similar to that existing for many forms of retinal degeneration.

Mosaic tetrasomy 15q25{yields}qter in a newborn infant with multiple anomalies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van den Enden, A.; Roy, N.V.; Speleman, F.

1996-06-14

We describe a premature boy with metopic craniosynostosis, facial anomalies, atrial-septal defect, hydronephrosis and flexion contractures of lower limbs, and mosaic tetrasomy 15q25{r_arrow}qter. The extra chromosome material was present in the form of an acentric marker. A number of clinical manifestations observed in this child were also found in 3 previously reported patients who were trisomic for the same part of chromosome 15 and in 2 patients who were tetrasomic for a larger segment of 15q. 17 refs., 4 figs., 1 tab.

NUT Midline Carcinoma of the Nasal Cavity.

PubMed

Edgar, Mia; Caruso, Andria M; Kim, Esther; Foss, Robert D

2017-09-01

Nuclear protein in testis (NUT) midline carcinoma (NMC) is a rare, aggressive, poorly differentiated form of squamous cell carcinoma caused by a chromosomal rearrangement of the NUT gene on chromosome 15. These tumors have a predilection for midline and paramidline structures of the upper aerodigestive tract and mediastinum and can affect patients across a broad age range, including children. In the current example, a 53 year old male presented with a mass originating in the left nasal cavity. The clinical, radiographic, and morphologic features of NMC are discussed.

A chromosomal analysis of Nepa cinerea Linnaeus, 1758 and Ranatra linearis (Linnaeus, 1758) (Heteroptera, Nepidae)

PubMed Central

Angus, Robert B.; Jeangirard, Constance; Stoianova, Desislava; Grozeva, Snejana; Kuznetsova, Valentina G.

2017-01-01

Abstract An account is given of the karyotypes and male meiosis of the Water Scorpion Nepa cinerea Linnaeus, 1758 and the Water Stick Insect Ranatra linearis (Linnaeus, 1758) (Heteroptera, Nepomorpha, Nepidae). A number of different approaches and techniques were tried: the employment of both male and female gonads and mid-guts as the sources of chromosomes, squash and air-drying methods for chromosome preparations, C-banding and fluorescence in situ hybridization (FISH) for chromosome study. We found that N. cinerea had a karyotype comprising 14 pairs of autosomes and a multiple sex chromosome system, which is X1X2X3X4Y (♂) / X1X1X2X2X3X3X4X4 (♀), whereas R. linearis had a karyotype comprising 19 pairs of autosomes and a multiple sex chromosome system X1X2X3X4Y (♂) / X1X1X2X2X3X3X4X4 (♀). In both N. cinerea and R. linearis, the autosomes formed chiasmate bivalents in spermatogenesis, and the sex chromosome univalents divided during the first meiotic division and segregated during the second one suggesting thus a post-reductional type of behaviour. These results confirm and amplify those of Steopoe (1925, 1927, 1931, 1932) but are inconsistent with those of other researchers. C-banding appeared helpful in pairing up the autosomes for karyotype assembly; however in R. linearis the chromosomes were much more uniform in size and general appearance than in N. cinerea. FISH for 18S ribosomal DNA (major rDNA) revealed hybridization signals on two of the five sex chromosomes in N. cinerea. In R. linearis, rDNA location was less obvious than in N. cinerea; however it is suggested to be similar. We have detected the presence of the canonical “insect” (TTAGG)n telomeric repeat in chromosomes of these species. This is the first application of C-banding and FISH in the family Nepidae. PMID:29114353

Sex determination in flowering plants: papaya as a model system.

PubMed

Aryal, Rishi; Ming, Ray

2014-03-01

Unisexuality in flowering plants evolved from a hermaphrodite ancestor. Transition from hermaphrodite to unisexual flowers has occurred multiple times across the different lineages of the angiosperms. Sexuality in plants is regulated by genetic, epigenetic and physiological mechanisms. The most specialized mechanism of sex determination is sex chromosomes. The sex chromosomes ensure the stable segregation of sexual phenotypes by preventing the recombination of sex determining genes. Despite continuous efforts, sex determining genes of dioecious plants have not yet been cloned. Concerted efforts with various model systems are necessary to understand the complex mechanism of sex determination in plants. Papaya (Carica papaya L.) is a tropical fruit tree with three sex forms, male, hermaphrodite, and female. Sexuality in papaya is determined by an XY chromosome system that is in an early evolutionary stage. The male and hermaphrodite of papaya are controlled by two different types of Y chromosomes: Y and Y(h). Large amounts of information in the area of genetics, genomics, and epigenetics of papaya have been accumulated over the last few decades. Relatively short lifecycle, small genome size, and readily available genetic and genomic resources render papaya an excellent model system to study sex determination and sex chromosomes in flowering plants. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Cytogenetics studies in Brazilian species of Pseudophyllinae (Orthoptera: Tettigoniidae): 2n(♂)=35 and fn=35 the probable basic and ancestral karyotype of the family Tettigoniidae.

PubMed

Ferreira, Amilton; Mesa, Alejo

2010-01-01

The karyotypes of five species of Brazilian Pseudophyllinae belonging to four tribes were here studied. The data available in the literature altogether with those obtained with species in here studied allowed us to infer that 2n(♂)=35 is the highest chromosome number found in the family Tettigoniidae and that it is present in species belonging to Pseudophyllinae, Zaprochilinae and in one species of Tettigoniinae. In spite of that all five species exhibit secondary karyotypes arisen surely by a mechanism of chromosomal rearrangement of centric fusion, tandem fusion and centric inversion types from those with 2n(♂)=35 and FN=35, they share some common traits. The X chromosome is submetacentric (FN=36), heteropicnotic during the first prophase, the largest of the set but its size is rather variable among the species and the sex chromosomal mechanism is of the XO( ♂ ), XX( ♀ ) type. The chromosomal rearrangements involved in the karyotype evolution of the Pseudophyllinae and its relationship with those of the family Tettigoniidae are discussed and we propose that the basic and the ancestral karyotype of the Tettigoniidae is formed by 2n(♂)=35, FN=35 and not by 2n(♂)=31, FN= 31, as usually accepted.

Kinetochore Dynein Is Required for Chromosome Motion and Congression Independent of the Spindle Checkpoint

PubMed Central

Yang, Zhenye; Tulu, U. Serdar; Wadsworth, Patricia; Rieder, Conly L.

2008-01-01

Summary During mitosis, the motor molecule cytoplasmic dynein plays key direct and indirect roles in organizing microtubules (MTs) into a functional spindle. At this time, dynein is also recruited to kinetochores, but its role or roles at these organelles remain vague, partly because inhibiting dynein globally disrupts spindle assembly [1-4]. However, dynein can be selectively depleted from kinetochores by disruption of ZW10 [5], and recent studies with this approach conclude that kinetochore-associated dynein (KD) functions to silence the spindle-assembly checkpoint (SAC) [6]. Here we use dynein-antibody microinjection and the RNAi of ZW10 to explore the role of KD in chromosome behavior during mitosis in mammals. We find that depleting or inhibiting KD prevents the rapid poleward motion of attaching kinetochores but not kinetochore fiber (K fiber) formation. However, after kinetochores attach to the spindle, KD is required for stabilizing kinetochore MTs, which it probably does by generating tension on the kinetochore, and in its absence, chromosome congression is defective. Finally, depleting KD reduces the velocity of anaphase chromosome motion by ∼40%, without affecting the rate of poleward MT flux. Thus, in addition to its role in silencing the SAC, KD is important for forming and stabilizing K fibers and in powering chromosome motion. PMID:17509882

Molecular and clinical characterization of a patient with a chromosome 4p deletion, Wolf-Hirschhorn syndrome, and congenital glaucoma.

PubMed

Finzi, S; Pinto, C F; Wiggs, J L

2001-03-01

Wolf-Hirschhorn syndrome is a developmental disorder associated with hemizygous deletion of the distal short arm of chromosome 4. We have identified a patient affected with Wolf-Hirschhorn syndrome and early onset glaucoma. Five other patients with Wolf-Hirschhorn syndrome and early onset glaucoma or ocular anomalies associated with early onset glaucoma have been previously described, suggesting that the association with Wolf-Hirschhorn syndrome is not coincidental. The infrequent association of early onset glaucoma suggests that the chromosomal region commonly deleted in Wolf-Hirschhorn patients does not contain genes responsible for early onset glaucoma. In this study, we performed a molecular characterization of the deleted chromosome 4 to determine the extent of the deletion in an attempt to begin to identify the chromosomal region responsible for the associated glaucoma. Using microsatellite repeat markers located on 4p, we determined that the deletion spanned a 60-cM region including the minimal Wolf-Hirschhorn region. The proximal breakpoint occurred between markers D4S3045 and D4S2974. These results support the hypothesis that patients with Wolf-Hirschhorn syndrome and early onset glaucoma may have large deletions of 4p that include a gene(s) that may be responsible for a dominant form of congenital glaucoma.

Differential Expression of Non-Coding RNAs and Continuous Evolution of the X Chromosome in Testicular Transcriptome of Two Mouse Species

PubMed Central

Homolka, David; Ivanek, Robert; Forejt, Jiri; Jansa, Petr

2011-01-01

Background Tight regulation of testicular gene expression is a prerequisite for male reproductive success, while differentiation of gene activity in spermatogenesis is important during speciation. Thus, comparison of testicular transcriptomes between closely related species can reveal unique regulatory patterns and shed light on evolutionary constraints separating the species. Methodology/Principal Findings Here, we compared testicular transcriptomes of two closely related mouse species, Mus musculus and Mus spretus, which diverged more than one million years ago. We analyzed testicular expression using tiling arrays overlapping Chromosomes 2, X, Y and mitochondrial genome. An excess of differentially regulated non-coding RNAs was found on Chromosome 2 including the intronic antisense RNAs, intergenic RNAs and premature forms of Piwi-interacting RNAs (piRNAs). Moreover, striking difference was found in the expression of X-linked G6pdx gene, the parental gene of the autosomal retrogene G6pd2. Conclusions/Significance The prevalence of non-coding RNAs among differentially expressed transcripts indicates their role in species-specific regulation of spermatogenesis. The postmeiotic expression of G6pdx in Mus spretus points towards the continuous evolution of X-chromosome silencing and provides an example of expression change accompanying the out-of-the X-chromosomal retroposition. PMID:21347268

Structural differences in reciprocal translocations. Potential for a model of risk in Rcp.

PubMed

Daniel, A

1979-10-01

Interchange segment sizes and the sizes of chromosome imbalance arising from the different modes of meiotic segregation were measured in a selected sample of 20 reciprocal translocations (Rep). The Rep were selected by two modes of ascertainment: (I) neonates with an unbalanced form of the translocation, and (II) couples with recurrent spontaneous abortions without evidence of full-term translocation aneuploid offspring. The measurements (% of haploid autosomal length: %HAL) were plotted as the observed or potential chromosomal imbalance with monosomy (abscissa) and trisomy (ordinate). It was found that (a) the interchange segments were larger in the spontaneous abortion Rcp, (b) that all of the imbalances observed in full-term neonates plotted close to the origin and to the left of the line joining 4% trisomy to 2% monosomy, and (c) the imbalances observed in the neonates in each individual Rcp were of the smallest size possible arising by any segregation mode. It was concluded that a major factor in the survival to term of aneuploid conceptuses is the size (proportion of genome) of the chromosome abnormality, irrespective of the origin of the chromosome regions. These results are discussed in relation to their use as a model to evaluate the risk of abnormal offspring in the progeny of translocation heterozygotes (the Chromosome Imbalance Size-Viability Model).

Chromosomal Mapping of Repetitive DNA Sequences in the Genus Bryconamericus (Characidae) and DNA Barcoding to Differentiate Populations.

PubMed

Santos, Angélica Rossotti Dos; Usso, Mariana Campaner; Gouveia, Juceli Gonzalez; Araya-Jaime, Cristian; Frantine-Silva, Wilson; Giuliano-Caetano, Lucia; Foresti, Fausto; Dias, Ana Lúcia

2017-06-01

The mapping of repetitive DNA sites by fluorescence in situ hybridization has been widely used for karyotype studies in different species of fish, especially when dealing with related species or even genera presenting high chromosome variability. This study analyzed three populations of Bryconamericus, with diploid number preserved, but with different karyotype formulae. Bryconamericus ecai, from the Forquetinha river/RS, presented three new cytotypes, increasing the number of karyotype forms to seven in this population. Other two populations of Bryconamericus sp. from the Vermelho stream/PR and Cambuta river/PR exhibited interpopulation variation. The chromosome mapping of rDNA sites revealed unique markings among the three populations, showing inter- and intrapopulation variability located in the terminal region. The molecular analysis using DNA barcoding complementing the cytogenetic analysis also showed differentiation among the three populations. The U2 small nuclear DNA repetitive sequence exhibited conserved features, being located in the interstitial region of a single chromosome pair. This is the first report on its occurrence in the genus Bryconamericus. Data obtained revealed a karyotype variability already assigned to the genus, along with polymorphism of ribosomal sites, demonstrating that this group of fish can be undergoing a divergent evolutionary process, constituting a substantive model for studies of chromosomal evolution.

Generation of amphidiploids from hybrids of wheat and related species from the genera Aegilops, Secale, Thinopyrum, and Triticum as a source of genetic variation for wheat improvement.

PubMed

Nemeth, Csilla; Yang, Cai-yun; Kasprzak, Paul; Hubbart, Stella; Scholefield, Duncan; Mehra, Surbhi; Skipper, Emma; King, Ian; King, Julie

2015-02-01

We aim to improve diversity of domesticated wheat by transferring genetic variation for important target traits from related wild and cultivated grass species. The present study describes the development of F1 hybrids between wheat and related species from the genera Aegilops, Secale, Thinopyrum, and Triticum and production of new amphidiploids. Amphidiploid lines were produced from 20 different distant relatives. Both colchicine and caffeine were successfully used to double the chromosome numbers. The genomic constitution of the newly formed amphidiploids derived from seven distant relatives was determined using genomic in situ hybridization (GISH). Altogether, 42 different plants were analysed, 19 using multicolour GISH separating the chromosomes from the A, B, and D genomes of wheat, as well as the distant relative, and 23 using single colour GISH. Restructuring of the allopolyploid genome, both chromosome losses and aneuploidy, was detected in all the genomes contained by the amphidiploids. From the observed chromosome numbers there is an indication that in amphidiploids the B genome of wheat suffers chromosome losses less frequently than the other wheat genomes. Phenotyping to realize the full potential of the wheat-related grass germplasm is underway, linking the analyzed genotypes to agronomically important target traits.

Inversion duplication deletions involving the long arm of chromosome 13: phenotypic description of additional three fetuses and genotype-phenotype correlation.

PubMed

Quelin, Chloe; Spaggiari, Emmanuel; Khung-Savatovsky, Suonavy; Dupont, Celine; Pasquier, Laurent; Loeuillet, Laurence; Jaillard, Sylvie; Lucas, Josette; Marcorelles, Pascale; Journel, Hubert; Pluquailec-Bilavarn, Khantaby; Bazin, Anne; Verloes, Alain; Delezoide, Anne-Lise; Aboura, Azzedine; Guimiot, Fabien

2014-10-01

Inversion duplication and terminal deletion of the long arm of chromosome 13 (inv dup del 13q) is a rare chromosomal rearrangement: only five patients have been reported, mostly involving a ring chromosome 13. We report on additional three fetuses with pure inv dup del 13q: Patient 1 had macrosomia, enlarged kidneys, hypersegmented lungs, unilateral moderate ventriculomegaly, and a mild form of hand and feet preaxial polydactyly; Patient 2 had intrauterine growth retardation, widely spaced eyes, left microphthalmia, right anophthalmia, short nose, bilateral absent thumbs, cutaneous syndactyly of toes 4 and 5, bifid third metacarpal, a small left kidney, hyposegmented lungs, and partial agenesis of the corpus callosum; Patient 3 had widely spaced eyes, long and smooth philtrum, low-set ears, median notch in the upper alveolar ridge, bifid tongue, cutaneous syndactyly of toes 2 and 3, enlarged kidneys and pancreas, arhinencephaly, and partial agenesis of the corpus callosum. We compared the phenotypes of these patients to those previously reported for ring chromosome 13, pure 13q deletions and duplications. We narrowed some critical regions previously reported for lung, kidney and fetal growth, and for thumb, cerebral, and eye anomalies. © 2014 Wiley Periodicals, Inc.

mazF, a novel counter-selectable marker for unmarked chromosomal manipulation in Bacillus subtilis.

PubMed

Zhang, Xiao-Zhou; Yan, Xin; Cui, Zhong-Li; Hong, Qing; Li, Shun-Peng

2006-05-19

Here, we present a novel method for the directed genetic manipulation of the Bacillus subtilis chromosome free of any selection marker. Our new approach employed the Escherichia coli toxin gene mazF as a counter-selectable marker. The mazF gene was placed under the control of an isopropyl-beta-D-thiogalactopyranoside (IPTG)-inducible expression system and associated with a spectomycin-resistance gene to form the MazF cassette, which was flanked by two directly-repeated (DR) sequences. A double-crossover event between the linearized delivery vector and the chromosome integrated the MazF cassette into a target locus and yielded an IPTG-sensitive strain with spectomycin-resistance, in which the wild-type chromosome copy had been replaced by the modified copy at the targeted locus. Another single-crossover event between the two DR sequences led to the excision of the MazF cassette and generated a strain with IPTG resistance, thereby realizing the desired alteration to the chromosome without introducing any unwanted selection markers. We used this method repeatedly and successfully to inactivate a specific gene, to introduce a gene of interest and to realize the in-frame deletion of a target gene in the same strain. As there is no prerequisite strain for this method, it will be a powerful and universal tool.

Mapping a gene for adult-onset primary open-angle glaucoma to chromosome 3q

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wirtz, M.K.; Samples, J.R.; Kramer, P.L.

1997-02-01

Glaucoma is the third-leading cause of blindness in the world, affecting >13.5 million people. Adult-on-set primary open-angle glaucoma (POAG) is the most common form of glaucoma in the United States. We present a family in which adult-onset POAG is inherited as an autosomal dominant trait. Twelve affected family members were identified from 44 at-risk individuals. The disease-causing gene was mapped to chromosome 3q21-24, with analysis of recombinant haplotypes suggesting a total inclusion region of 11.1 cM between markers D3S3637 and D3S1744. This is the first report of mapping of an adult-onset POAG gene to chromosome 3q, gene symbol GLC1C. 57more » refs., 3 figs., 3 tabs.« less

Usher Syndrome Type III: Revised Genomic Structure of the USH3 Gene and Identification of Novel Mutations

PubMed Central

Fields, Randall R.; Zhou, Guimei; Huang, Dali; Davis, Jack R.; Möller, Claes; Jacobson, Samuel G.; Kimberling, William J.; Sumegi, Janos

2002-01-01

Usher syndrome type III is an autosomal recessive disorder characterized by progressive sensorineural hearing loss, vestibular dysfunction, and retinitis pigmentosa. The disease gene was localized to 3q25 and recently was identified by positional cloning. In the present study, we have revised the structure of the USH3 gene, including a new translation start site, 5′ untranslated region, and a transcript encoding a 232–amino acid protein. The mature form of the protein is predicted to contain three transmembrane domains and 204 residues. We have found four new disease-causing mutations, including one that appears to be relatively common in the Ashkenazi Jewish population. We have also identified mouse (chromosome 3) and rat (chromosome 2) orthologues, as well as two human paralogues on chromosomes 4 and 10. PMID:12145752

Integrative analysis of the Caenorhabditis elegans genome by the modENCODE project.

PubMed

Gerstein, Mark B; Lu, Zhi John; Van Nostrand, Eric L; Cheng, Chao; Arshinoff, Bradley I; Liu, Tao; Yip, Kevin Y; Robilotto, Rebecca; Rechtsteiner, Andreas; Ikegami, Kohta; Alves, Pedro; Chateigner, Aurelien; Perry, Marc; Morris, Mitzi; Auerbach, Raymond K; Feng, Xin; Leng, Jing; Vielle, Anne; Niu, Wei; Rhrissorrakrai, Kahn; Agarwal, Ashish; Alexander, Roger P; Barber, Galt; Brdlik, Cathleen M; Brennan, Jennifer; Brouillet, Jeremy Jean; Carr, Adrian; Cheung, Ming-Sin; Clawson, Hiram; Contrino, Sergio; Dannenberg, Luke O; Dernburg, Abby F; Desai, Arshad; Dick, Lindsay; Dosé, Andréa C; Du, Jiang; Egelhofer, Thea; Ercan, Sevinc; Euskirchen, Ghia; Ewing, Brent; Feingold, Elise A; Gassmann, Reto; Good, Peter J; Green, Phil; Gullier, Francois; Gutwein, Michelle; Guyer, Mark S; Habegger, Lukas; Han, Ting; Henikoff, Jorja G; Henz, Stefan R; Hinrichs, Angie; Holster, Heather; Hyman, Tony; Iniguez, A Leo; Janette, Judith; Jensen, Morten; Kato, Masaomi; Kent, W James; Kephart, Ellen; Khivansara, Vishal; Khurana, Ekta; Kim, John K; Kolasinska-Zwierz, Paulina; Lai, Eric C; Latorre, Isabel; Leahey, Amber; Lewis, Suzanna; Lloyd, Paul; Lochovsky, Lucas; Lowdon, Rebecca F; Lubling, Yaniv; Lyne, Rachel; MacCoss, Michael; Mackowiak, Sebastian D; Mangone, Marco; McKay, Sheldon; Mecenas, Desirea; Merrihew, Gennifer; Miller, David M; Muroyama, Andrew; Murray, John I; Ooi, Siew-Loon; Pham, Hoang; Phippen, Taryn; Preston, Elicia A; Rajewsky, Nikolaus; Rätsch, Gunnar; Rosenbaum, Heidi; Rozowsky, Joel; Rutherford, Kim; Ruzanov, Peter; Sarov, Mihail; Sasidharan, Rajkumar; Sboner, Andrea; Scheid, Paul; Segal, Eran; Shin, Hyunjin; Shou, Chong; Slack, Frank J; Slightam, Cindie; Smith, Richard; Spencer, William C; Stinson, E O; Taing, Scott; Takasaki, Teruaki; Vafeados, Dionne; Voronina, Ksenia; Wang, Guilin; Washington, Nicole L; Whittle, Christina M; Wu, Beijing; Yan, Koon-Kiu; Zeller, Georg; Zha, Zheng; Zhong, Mei; Zhou, Xingliang; Ahringer, Julie; Strome, Susan; Gunsalus, Kristin C; Micklem, Gos; Liu, X Shirley; Reinke, Valerie; Kim, Stuart K; Hillier, LaDeana W; Henikoff, Steven; Piano, Fabio; Snyder, Michael; Stein, Lincoln; Lieb, Jason D; Waterston, Robert H

2010-12-24

We systematically generated large-scale data sets to improve genome annotation for the nematode Caenorhabditis elegans, a key model organism. These data sets include transcriptome profiling across a developmental time course, genome-wide identification of transcription factor-binding sites, and maps of chromatin organization. From this, we created more complete and accurate gene models, including alternative splice forms and candidate noncoding RNAs. We constructed hierarchical networks of transcription factor-binding and microRNA interactions and discovered chromosomal locations bound by an unusually large number of transcription factors. Different patterns of chromatin composition and histone modification were revealed between chromosome arms and centers, with similarly prominent differences between autosomes and the X chromosome. Integrating data types, we built statistical models relating chromatin, transcription factor binding, and gene expression. Overall, our analyses ascribed putative functions to most of the conserved genome.

Model of chromosomal loci dynamics in bacteria as fractional diffusion with intermittent transport

NASA Astrophysics Data System (ADS)

Gherardi, Marco; Calabrese, Ludovico; Tamm, Mikhail; Cosentino Lagomarsino, Marco

2017-10-01

The short-time dynamics of bacterial chromosomal loci is a mixture of subdiffusive and active motion, in the form of rapid relocations with near-ballistic dynamics. While previous work has shown that such rapid motions are ubiquitous, we still have little grasp on their physical nature, and no positive model is available that describes them. Here, we propose a minimal theoretical model for loci movements as a fractional Brownian motion subject to a constant but intermittent driving force, and compare simulations and analytical calculations to data from high-resolution dynamic tracking in E. coli. This analysis yields the characteristic time scales for intermittency. Finally, we discuss the possible shortcomings of this model, and show that an increase in the effective local noise felt by the chromosome associates to the active relocations.

Telomere Biology—Insights into an Intriguing Phenomenon

PubMed Central

Venkatesan, Shriram; Khaw, Aik Kia; Hande, Manoor Prakash

2017-01-01

Bacteria and viruses possess circular DNA, whereas eukaryotes with typically very large DNA molecules have had to evolve into linear chromosomes to circumvent the problem of supercoiling circular DNA of that size. Consequently, such organisms possess telomeres to cap chromosome ends. Telomeres are essentially tandem repeats of any DNA sequence that are present at the ends of chromosomes. Their biology has been an enigmatic one, involving various molecules interacting dynamically in an evolutionarily well-trimmed fashion. Telomeres range from canonical hexameric repeats in most eukaryotes to unimaginably random retrotransposons, which attach to chromosome ends and reverse-transcribe to DNA in some plants and insects. Telomeres invariably associate with specialised protein complexes that envelop it, also regulating access of the ends to legitimate enzymes involved in telomere metabolism. They also transcribe into repetitive RNA which also seems to be playing significant roles in telomere maintenance. Telomeres thus form the intersection of DNA, protein, and RNA molecules acting in concert to maintain chromosome integrity. Telomere biology is emerging to appear ever more complex than previously envisaged, with the continual discovery of more molecules and interplays at the telomeres. This review also includes a section dedicated to the history of telomere biology, and intends to target the scientific audience new to the field by rendering an understanding of the phenomenon of chromosome end protection at large, with more emphasis on the biology of human telomeres. The review provides an update on the field and mentions the questions that need to be addressed. PMID:28629193

Segregation for Sexual Seed Production in Paspalum as Directed by Male Gametes of Apomictic Triploid Plants

PubMed Central

Martínez, Eric J.; Acuña, Carlos A.; Hojsgaard, Diego H.; Tcach, Mauricio A.; Quarin, Camilo L.

2007-01-01

Background and Aims Gametophytic apomixis is regularly associated with polyploidy. It has been hypothesized that apomixis is not present in diploid plants because of a pleiotropic lethal effect associated with monoploid gametes. Rare apomictic triploid plants for Paspalum notatum and P. simplex, which usually have sexual diploid and apomictic tetraploid races, were acquired. These triploids normally produce male gametes through meiosis with a range of chromosome numbers from monoploid (n = 10) to diploid (n = 20). The patterns of apomixis transmission in Paspalum were investigated in relation to the ploidy levels of gametes. Methods Intraspecific crosses were made between sexual diploid, triploid and tetraploid plants as female parents and apomictic triploid plants as male parents. Apomictic progeny were identified by using molecular markers completely linked to apomixis and the analysis of mature embryo sacs. The chromosome number of the male gamete was inferred from chromosome counts of each progeny. Key Results The chromosome numbers of the progeny indicated that the chromosome input of male gametes depended on the chromosome number of the female gamete. The apomictic trait was not transmitted through monoploid gametes, at least when the progeny was diploid. Diploid or near-diploid gametes transmitted apomixis at very low rates. Conclusions Since male monoploid gametes usually failed to form polyploid progenies, for example triploids after 4x × 3x crosses, it was not possible to determine whether apomixis could segregate in polyploid progenies by means of monoploid gametes. PMID:17766843

Deletion of DXZ4 on the human inactive X chromosome alters higher-order genome architecture

PubMed Central

Darrow, Emily M.; Huntley, Miriam H.; Dudchenko, Olga; Stamenova, Elena K.; Durand, Neva C.; Sun, Zhuo; Huang, Su-Chen; Sanborn, Adrian L.; Machol, Ido; Shamim, Muhammad; Seberg, Andrew P.; Lander, Eric S.; Chadwick, Brian P.; Aiden, Erez Lieberman

2016-01-01

During interphase, the inactive X chromosome (Xi) is largely transcriptionally silent and adopts an unusual 3D configuration known as the “Barr body.” Despite the importance of X chromosome inactivation, little is known about this 3D conformation. We recently showed that in humans the Xi chromosome exhibits three structural features, two of which are not shared by other chromosomes. First, like the chromosomes of many species, Xi forms compartments. Second, Xi is partitioned into two huge intervals, called “superdomains,” such that pairs of loci in the same superdomain tend to colocalize. The boundary between the superdomains lies near DXZ4, a macrosatellite repeat whose Xi allele extensively binds the protein CCCTC-binding factor. Third, Xi exhibits extremely large loops, up to 77 megabases long, called “superloops.” DXZ4 lies at the anchor of several superloops. Here, we combine 3D mapping, microscopy, and genome editing to study the structure of Xi, focusing on the role of DXZ4. We show that superloops and superdomains are conserved across eutherian mammals. By analyzing ligation events involving three or more loci, we demonstrate that DXZ4 and other superloop anchors tend to colocate simultaneously. Finally, we show that deleting DXZ4 on Xi leads to the disappearance of superdomains and superloops, changes in compartmentalization patterns, and changes in the distribution of chromatin marks. Thus, DXZ4 is essential for proper Xi packaging. PMID:27432957

Nonhomologous Synapsis and Reduced Crossing over in a Heterozygous Paracentric Inversion in Saccharomyces Cerevisiae

PubMed Central

Dresser, M. E.; Ewing, D. J.; Harwell, S. N.; Coody, D.; Conrad, M. N.

1994-01-01

Homologous chromosome synapsis (``homosynapsis'') and crossing over are well-conserved aspects of meiotic chromosome behavior. The long-standing assumption that these two processes are causally related has been challenged recently by observations in Saccharomyces cerevisiae of significant levels of crossing over (1) between small sequences at nonhomologous locations and (2) in mutants where synapsis is abnormal or absent. In order to avoid problems of local sequence effects and of mutation pleiotropy, we have perturbed synapsis by making a set of isogenic strains that are heterozygous and homozygous for a large chromosomal paracentric inversion covering a well marked genetic interval and then measured recombination. We find that reciprocal recombination in the marked interval in heterozygotes is reduced variably across the interval, on average to ~55% of that in the homozygotes, and that positive interference still modulates crossing over. Cytologically, stable synapsis across the interval is apparently heterologous rather than homologous, consistent with the interpretation that stable homosynapsis is required to initiate or consummate a large fraction of the crossing over observed in wild-type strains. When crossing over does occur in heterozygotes, dicentric and acentric chromosomes are formed and can be visualized and quantitated on blots though not demonstrated in viable spores. We find that there is no loss of dicentric chromosomes during the two meiotic divisions and that the acentric chromosome is recovered at only 1/3 to 1/2 of the expected level. PMID:7851761

The histone acetyltransferase component TRRAP is targeted for destruction during the cell cycle.

PubMed

Ichim, G; Mola, M; Finkbeiner, M G; Cros, M-P; Herceg, Z; Hernandez-Vargas, H

2014-01-09

Chromosomes are dynamic structures that must be reversibly condensed and unfolded to accommodate mitotic division and chromosome segregation. Histone modifications are involved in the striking chromatin reconfiguration taking place during mitosis. However, the mechanisms that regulate activity and function of histone-modifying factors as cells enter and exit mitosis are poorly understood. Here, we show that the anaphase-promoting complex or cyclosome (APC/C) is involved in the mitotic turnover of TRRAP (TRansformation/tRanscription domain-Associated Protein), a common component of histone acetyltransferase (HAT) complexes, and that the pre-mitotic degradation of TRRAP is mediated by the APC/C ubiquitin ligase activators Cdc20 and Cdh1. Ectopic expression of both Cdh1 and Cdc20 reduced the levels of coexpressed TRRAP protein and induced its ubiquitination. TRRAP overexpression or stabilization induces multiple mitotic defects, including lagging chromosomes, chromosome bridges and multipolar spindles. In addition, lack of sister chromatid cohesion and impaired chromosome condensation were found after TRRAP overexpression or stabilization. By using a truncated form of TRRAP, we show that mitotic delay is associated with a global histone H4 hyperacetylation induced by TRRAP overexpression. These results demonstrate that the chromatin modifier TRRAP is targeted for destruction in a cell cycle-dependent fashion. They also suggest that degradation of TRRAP by the APC/C is necessary for a proper condensation of chromatin and proper chromosome segregation. Chromatin compaction mediated by histone modifiers may represent a fundamental arm for APC/C orchestration of the mitotic machinery.

Genetics Home Reference: cyclic vomiting syndrome

MedlinePlus

... childhood, may be related to changes in mitochondrial DNA . Mitochondria are structures within cells that convert the ... a form that cells can use. Although most DNA is packaged in chromosomes within the nucleus, mitochondria ...

Science& Technology Review June 2003

DOE Office of Scientific and Technical Information (OSTI.GOV)

McMahon, D

This month's issue has the following articles: (1) Livermore's Three-Pronged Strategy for High-Performance Computing, Commentary by Dona Crawford; (2) Riding the Waves of Supercomputing Technology--Livermore's Computation Directorate is exploiting multiple technologies to ensure high-performance, cost-effective computing; (3) Chromosome 19 and Lawrence Livermore Form a Long-Lasting Bond--Lawrence Livermore biomedical scientists have played an important role in the Human Genome Project through their long-term research on chromosome 19; (4) A New Way to Measure the Mass of Stars--For the first time, scientists have determined the mass of a star in isolation from other celestial bodies; and (5) Flexibly Fueled Storage Tank Bringsmore » Hydrogen-Powered Cars Closer to Reality--Livermore's cryogenic hydrogen fuel storage tank for passenger cars of the future can accommodate three forms of hydrogen fuel separately or in combination.« less

The Yeast Polo Kinase Cdc5 Regulates the Shape of the Mitotic Nucleus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walters, Alison D.; May, Christopher K.; Dauster, Emma S.

Abnormal nuclear size and shape are hallmarks of aging and cancer. However, the mechanisms regulating nuclear morphology and nuclear envelope (NE) expansion are poorly understood. In metazoans, the NE disassembles prior to chromosome segregation and reassembles at the end of mitosis. In budding yeast, the NE remains intact. The nucleus elongates as chromosomes segregate and then divides at the end of mitosis to form two daughter nuclei without NE disassembly. The budding yeast nucleus also undergoes remodeling during a mitotic arrest; the NE continues to expand despite the pause in chromosome segregation, forming a nuclear extension, or "flare," that encompassesmore » the nucleolus. The distinct nucleolar localization of the mitotic flare indicates that the NE is compartmentalized and that there is a mechanism by which NE expansion is confined to the region adjacent to the nucleolus. Here we show that mitotic flare formation is dependent on the yeast polo kinase Cdc5. This function of Cdc5 is independent of its known mitotic roles, including rDNA condensation. High-resolution imaging revealed that following Cdc5 inactivation, nuclei expand isometrically rather than forming a flare, indicating that Cdc5 is needed for NE compartmentalization. Lastly, even in an uninterrupted cell cycle, a small NE expansion occurs adjacent to the nucleolus prior to anaphase in a Cdc5-dependent manner. Our data provide the first evidence that polo kinase, a key regulator of mitosis, plays a role in regulating nuclear morphology and NE expansion.« less

The Yeast Polo Kinase Cdc5 Regulates the Shape of the Mitotic Nucleus

DOE PAGES

Walters, Alison D.; May, Christopher K.; Dauster, Emma S.; ...

2014-11-20

Abnormal nuclear size and shape are hallmarks of aging and cancer. However, the mechanisms regulating nuclear morphology and nuclear envelope (NE) expansion are poorly understood. In metazoans, the NE disassembles prior to chromosome segregation and reassembles at the end of mitosis. In budding yeast, the NE remains intact. The nucleus elongates as chromosomes segregate and then divides at the end of mitosis to form two daughter nuclei without NE disassembly. The budding yeast nucleus also undergoes remodeling during a mitotic arrest; the NE continues to expand despite the pause in chromosome segregation, forming a nuclear extension, or "flare," that encompassesmore » the nucleolus. The distinct nucleolar localization of the mitotic flare indicates that the NE is compartmentalized and that there is a mechanism by which NE expansion is confined to the region adjacent to the nucleolus. Here we show that mitotic flare formation is dependent on the yeast polo kinase Cdc5. This function of Cdc5 is independent of its known mitotic roles, including rDNA condensation. High-resolution imaging revealed that following Cdc5 inactivation, nuclei expand isometrically rather than forming a flare, indicating that Cdc5 is needed for NE compartmentalization. Lastly, even in an uninterrupted cell cycle, a small NE expansion occurs adjacent to the nucleolus prior to anaphase in a Cdc5-dependent manner. Our data provide the first evidence that polo kinase, a key regulator of mitosis, plays a role in regulating nuclear morphology and NE expansion.« less

A quantitative study of the second meiotic metaphase in male mice (Mus musculus).

PubMed

Beatty, R A; Lim, M C; Coulter, V J

1975-01-01

Over 11,000 second meiotic metaphase spreads stained for the pericentromeric region have been studied quantitatively in male mice of 14 strains. The sex-chromosome constitution of a cell could be judged objectively if X and Y chromosomes and ploidy were all scored. A bias arose if only Y chromosomes and ploidy were scored but could be corrected statistically. There was no sign of other forms of bias. The original contiguity of X and Y second metaphases in vivo was very occasionally evident in the preparations. Most of the subhaploid aneuploid counts were assumed to be artifactual. The incidence of truly aneuploid second metaphases in 13 strains was estimated as 0.38+/-0.12%. The estimated average rate per chromosome was 0.019+/-0.006%, with a comparable order of magnitude for the sex chromosomes alone. Simultaneous aneuploidy of two or more chromosomes of the haploid set was estimated to be very rare. Of the spreads from 13 strains, 9.6% were polyploid (2N, 3N, 4N) and showed most of the possible combinations of sex chromosomes. Nearly all the polyploid spreads were considered to arise by artifactual cell fusion at the time of second metaphase during the preparative technique, especially of the X and Y daughter-cell products of the first meiotic division. Other modes of origin (true polyploidy, accidental superposition of cells during preparation) were unlikely. The data could be accommodated by a statistical model with only four parameters. It allowed for artifactual fusion mainly between daughter cells but also between non-daughter cells, bias in one scoring method, and bias in the numbers of cells with given ploidy successfully mounted. Current techniques of chromosome preparation were thought to be wholly unsuitable for the recognition of true polyploidy. The artifactual origin of polyploid spreads was borne out by an absence of polyploid spermatozoa in 14 strains. There appeared to be a virtually constant transmission rate of paternal X and Y chromosomes from early meiosis to late blastocyst. The estimated rate of 49.05+/-0.67% with a Y chromosome also estimated the primary sex ratio. There was evidence of polymorphism in autosomal pericentromeric staining in 3 strains. No measure of the numbers of autosomes or sex chromosomes varied significantly between duplicate preparations or between duplicate males of a strain.

Non-canonical ribosomal DNA segments in the human genome, and nucleoli functioning.

PubMed

Kupriyanova, Natalia S; Netchvolodov, Kirill K; Sadova, Anastasia A; Cherepanova, Marina D; Ryskov, Alexei P

2015-11-10

Ribosomal DNA (rDNA) in the human genome is represented by tandem repeats of 43 kb nucleotide sequences that form nucleoli organizers (NORs) on each of five pairs of acrocentric chromosomes. RDNA-similar segments of different lengths are also present on (NOR)(-) chromosomes. Many of these segments contain nucleotide substitutions, supplementary microsatellite clusters, and extended deletions. Recently, it was shown that, in addition to ribosome biogenesis, nucleoli exhibit additional functions, such as cell-cycle regulation and response to stresses. In particular, several stress-inducible loci located in the ribosomal intergenic spacer (rIGS) produce stimuli-specific noncoding nucleolus RNAs. By mapping the 5'/3' ends of the rIGS segments scattered throughout (NOR)(-) chromosomes, we discovered that the bonds in the rIGS that were most often susceptible to disruption in the rIGS were adjacent to, or overlapped with stimuli-specific inducible loci. This suggests the interconnection of the two phenomena - nucleoli functioning and the scattering of rDNA-like sequences on (NOR)(-) chromosomes. Copyright © 2015 Elsevier B.V. All rights reserved.

Eccentric localization of catalase to protect chromosomes from oxidative damages during meiotic maturation in mouse oocytes.

PubMed

Park, Yong Seok; You, Seung Yeop; Cho, Sungrae; Jeon, Hyuk-Joon; Lee, Sukchan; Cho, Dong-Hyung; Kim, Jae-Sung; Oh, Jeong Su

2016-09-01

The maintenance of genomic integrity and stability is essential for the survival of every organism. Unfortunately, DNA is vulnerable to attack by a variety of damaging agents. Oxidative stress is a major cause of DNA damage because reactive oxygen species (ROS) are produced as by-products of normal cellular metabolism. Cells have developed eloquent antioxidant defense systems to protect themselves from oxidative damage along with aerobic metabolism. Here, we show that catalase (CAT) is present in mouse oocytes to protect the genome from oxidative damage during meiotic maturation. CAT was expressed in the nucleus to form unique vesicular structures. However, after nuclear envelope breakdown, CAT was redistributed in the cytoplasm with particular focus at the chromosomes. Inhibition of CAT activity increased endogenous ROS levels, but did not perturb meiotic maturation. In addition, CAT inhibition produced chromosomal defects, including chromosome misalignment and DNA damage. Therefore, our data suggest that CAT is required not only to scavenge ROS, but also to protect DNA from oxidative damage during meiotic maturation in mouse oocytes.

Impact of pericentric inversion of Chromosome 9 [inv (9) (p11q12)] on infertility.

PubMed

Mozdarani, Hossein; Meybodi, Anahita Mohseni; Karimi, Hamideh

2007-01-01

One of the frequent occurrences in chromosome rearrangements is pericentric inversion of the Chromosome 9; inv (9) (p11q12), which is consider to be the variant of normal karyotype. Although it seems not to correlate with abnormal phenotypes, there have been many controversial reports indicating that it may lead to abnormal clinical conditions such as infertility. The incidence is found to be about 1.98% in the general population. We investigated the karyotypes of 300 infertile couples (600 individuals) being referred to our infertility clinic using standard GTG banding for karyotype preparation. The chromosomal analysis revealed a total of 15 (2.5%) inversions, among these, 14 male patients were inversion 9 carriers (4.69%) while one female patient was affected (0.33%). The incidence of inversion 9 in male patients is significantly higher than that of normal population and even than that of female patients (P< 0.05). This result suggests that inversion 9 may often cause infertility in men due to spermatogenic disturbances, which are arisen by the loops or acentric fragments formed in meiosis.

The fidelity of synaptonemal complex assembly is regulated by a signaling mechanism that controls early meiotic progression.

PubMed

Silva, Nicola; Ferrandiz, Nuria; Barroso, Consuelo; Tognetti, Silvia; Lightfoot, James; Telecan, Oana; Encheva, Vesela; Faull, Peter; Hanni, Simon; Furger, Andre; Snijders, Ambrosius P; Speck, Christian; Martinez-Perez, Enrique

2014-11-24

Proper chromosome segregation during meiosis requires the assembly of the synaptonemal complex (SC) between homologous chromosomes. However, the SC structure itself is indifferent to homology, and poorly understood mechanisms that depend on conserved HORMA-domain proteins prevent ectopic SC assembly. Although HORMA-domain proteins are thought to regulate SC assembly as intrinsic components of meiotic chromosomes, here we uncover a key role for nuclear soluble HORMA-domain protein HTP-1 in the quality control of SC assembly. We show that a mutant form of HTP-1 impaired in chromosome loading provides functionality of an HTP-1-dependent checkpoint that delays exit from homology search-competent stages until all homolog pairs are linked by the SC. Bypassing of this regulatory mechanism results in premature meiotic progression and licensing of homology-independent SC assembly. These findings identify nuclear soluble HTP-1 as a regulator of early meiotic progression, suggesting parallels with the mode of action of Mad2 in the spindle assembly checkpoint. Copyright © 2014 Elsevier Inc. All rights reserved.

Understanding familial and non-familial renal cell cancer.

PubMed

Bodmer, Daniëlle; van den Hurk, Wilhelmina; van Groningen, Jan J M; Eleveld, Marc J; Martens, Gerard J M; Weterman, Marian A J; van Kessel, Ad Geurts

2002-10-01

Molecular genetic analysis of familial and non-familial cases of conventional renal cell carcinoma (RCC) revealed a critical role(s) for multiple genes on human chromosome 3. For some of these genes, e.g. VHL, such a role has been firmly established, whereas for others, definite confirmation is still pending. Additionally, a novel role for constitutional chromosome 3 translocations as risk factors for conventional RCC development is rapidly emerging. Also, several candidate loci have been mapped to other chromosomes in both familial and non-familial RCCs of distinct histologic subtypes. The MET gene on chromosome 7, for example, was found to be involved in both forms of papillary RCC. A PRCC-TFE3 fusion gene is typically encountered in t(X;1)-positive non-familial papillary RCCs and results in abrogation of the cell cycle mitotic spindle checkpoint in a dominant-negative fashion, thus leading to RCC. Together, these data turn human RCC into a model system in which different aspects of both familial and non-familial syndromes may act as novel paradigms for cancer development.

Stable Inheritance of Host Species-Derived Microchromosomes in the Gynogenetic Fish Poecilia formosa

PubMed Central

Nanda, Indrajit; Schlupp, Ingo; Lamatsch, Dunja K.; Lampert, Kathrin P.; Schmid, Michael; Schartl, Manfred

2007-01-01

B chromosomes are additional, usually unstable constituents of the genome of many organisms. Their origin, however, is often unclear and their evolutionary relevance is not well understood. They may range from being deleterious to neutral or even beneficial. We have followed the genetic fate of B chromosomes in the asexual, all-female fish Poecilia formosa over eight generations. In this species, B chromosomes come in the form of one to three tiny microchromosomes derived from males of the host species that serve as sperm donors for this gynogenetic species. All microchromosomes have centromeric heterochromatin but usually only one has a telomere. Such microchromosomes are stably inherited, while the telomereless are prone to be lost in both the soma and germline. In some cases the stable microchromosome carries a functional gene lending support to the hypothesis that the B chromosomes in P. formosa could increase the genetic diversity of the clonal lineage in this ameiotic organism and to some degree counteract the genomic decay that is supposed to be connected with the lack of recombination. PMID:17720916

Prophase pathway-dependent removal of cohesin from human chromosomes requires opening of the Smc3–Scc1 gate

PubMed Central

Buheitel, Johannes; Stemmann, Olaf

2013-01-01

Faithful transmission of chromosomes during eukaryotic cell division requires sister chromatids to be paired from their generation in S phase until their separation in M phase. Cohesion is mediated by the cohesin complex, whose Smc1, Smc3 and Scc1 subunits form a tripartite ring that entraps both DNA double strands. Whereas centromeric cohesin is removed in late metaphase by Scc1 cleavage, metazoan cohesin at chromosome arms is displaced already in prophase by proteolysis-independent signalling. Which of the three gates is triggered by the prophase pathway to open has remained enigmatic. Here, we show that displacement of human cohesin from early mitotic chromosomes requires dissociation of Smc3 from Scc1 but no opening of the other two gates. In contrast, loading of human cohesin onto chromatin in telophase occurs through the Smc1–Smc3 hinge. We propose that the use of differently regulated gates for loading and release facilitates unidirectionality of DNA's entry into and exit from the cohesin ring. PMID:23361318

Local chromosome context is a major determinant of crossover pathway biochemistry during budding yeast meiosis.

PubMed

Medhi, Darpan; Goldman, Alastair Sh; Lichten, Michael

2016-11-18

The budding yeast genome contains regions where meiotic recombination initiates more frequently than in others. This pattern parallels enrichment for the meiotic chromosome axis proteins Hop1 and Red1. These proteins are important for Spo11-catalyzed double strand break formation; their contribution to crossover recombination remains undefined. Using the sequence-specific VMA1 -derived endonuclease (VDE) to initiate recombination in meiosis, we show that chromosome structure influences the choice of proteins that resolve recombination intermediates to form crossovers. At a Hop1-enriched locus, most VDE-initiated crossovers, like most Spo11-initiated crossovers, required the meiosis-specific MutLγ resolvase. In contrast, at a locus with lower Hop1 occupancy, most VDE-initiated crossovers were MutLγ-independent. In pch2 mutants, the two loci displayed similar Hop1 occupancy levels, and VDE-induced crossovers were similarly MutLγ-dependent. We suggest that meiotic and mitotic recombination pathways coexist within meiotic cells, and that features of meiotic chromosome structure determine whether one or the other predominates in different regions.

Mre11-Sae2 and RPA Collaborate to Prevent Palindromic Gene Amplification.

PubMed

Deng, Sarah K; Yin, Yi; Petes, Thomas D; Symington, Lorraine S

2015-11-05

Foldback priming at DNA double-stranded breaks is one mechanism proposed to initiate palindromic gene amplification, a common feature of cancer cells. Here, we show that small (5-9 bp) inverted repeats drive the formation of large palindromic duplications, the major class of chromosomal rearrangements recovered from yeast cells lacking Sae2 or the Mre11 nuclease. RPA dysfunction increased the frequency of palindromic duplications in Sae2 or Mre11 nuclease-deficient cells by ∼ 1,000-fold, consistent with intra-strand annealing to create a hairpin-capped chromosome that is subsequently replicated to form a dicentric isochromosome. The palindromic duplications were frequently associated with duplication of a second chromosome region bounded by a repeated sequence and a telomere, suggesting the dicentric chromosome breaks and repairs by recombination between dispersed repeats to acquire a telomere. We propose secondary structures within single-stranded DNA are potent instigators of genome instability, and RPA and Mre11-Sae2 play important roles in preventing their formation and propagation, respectively. Copyright © 2015 Elsevier Inc. All rights reserved.

Getting in (and out of) the loop: regulating higher order telomere structures.

PubMed

Luke-Glaser, Sarah; Poschke, Heiko; Luke, Brian

2012-01-01

The DNA at the ends of linear chromosomes (the telomere) folds back onto itself and forms an intramolecular lariat-like structure. Although the telomere loop has been implicated in the protection of chromosome ends from nuclease-mediated resection and unscheduled DNA repair activities, it potentially poses an obstacle to the DNA replication machinery during S-phase. Therefore, the coordinated regulation of telomere loop formation, maintenance, and resolution is required in order to establish a balance between protecting the chromosome ends and promoting their duplication prior to cell division. Until recently, the only factor known to influence telomere looping in human cells was TRF2, a component of the shelterin complex. Recent work in yeast and mouse cells has uncovered additional regulatory factors that affect the loop structure at telomeres. In the following "perspective" we outline what is known about telomere looping and highlight the latest results regarding the regulation of this chromosome end structure. We speculate about how the manipulation of the telomere loop may have therapeutic implications in terms of diseases associated with telomere dysfunction and uncontrolled proliferation.

A pre-intervention study of malaria vector abundance in Rio Muni, Equatorial Guinea: Their role in malaria transmission and the incidence of insecticide resistance alleles

PubMed Central

Ridl, Frances C; Bass, Chris; Torrez, Miguel; Govender, Dayanandan; Ramdeen, Varsha; Yellot, Lee; Edu, Amado Edjang; Schwabe, Christopher; Mohloai, Peter; Maharaj, Rajendra; Kleinschmidt, Immo

2008-01-01

Background Following the success of the malaria control intervention on the island of Bioko, malaria control by the use of indoor residual spraying (IRS) and long-lasting insecticide-treated nets (LLITN) was extended to Rio Muni, on the mainland part of Equatorial Guinea. This manuscript reports on the malaria vectors present and the incidence of insecticide resistant alleles prior to the onset of the programme. Methods Anopheles mosquitoes were captured daily using window traps at 30 sentinel sites in Rio Muni, from December 2006 to July 2007. The mosquitoes were identified to species and their sporozoite rates, knockdown resistance (kdr) and acetylcholinesterase (AChE) sensitivity measured, to define the role of vector species in malaria transmission and their potential susceptibility to insecticides. Results A total of 6,162 Anopheles mosquitoes were collected of which 4,808 were morphologically identified as Anopheles gambiae s.l., 120 Anopheles funestus, 1,069 Anopheles moucheti, and 165 Anopheles nili s.l.. Both M and S molecular forms of Anopheles gambiae s.s. and Anopheles melas were identified. Anopheles ovengensis and Anopheles carnevalei were the only two members of the An. nili group to be identified. Using the species-specific sporozoite rates and the average number of mosquitoes per night, the number of infective mosquitoes per trap per 100 nights for each species complex was calculated as a measure of transmission risk. Both kdr-w and kdr-e alleles were present in the S-form of An. gambiae s.s. (59% and 19% respectively) and at much lower frequencies in the M-form (9.7% and 1.8% respectively). The kdr-w and kdr-e alleles co-occurred in 103 S-form and 1 M-form specimens. No insensitive AChE was detected. Conclusion Anopheles gambiae s.s, a member of the Anopheles gambiae complex was shown to be the major vector in Rio Muni with the other three groups playing a relatively minor role in transmission. The demonstration of a high frequency of kdr alleles in mosquito populations before the onset of a malaria control programme shows that continuous entomological surveillance including resistance monitoring will be of critical importance to ensure the chosen insecticide remains effective. PMID:18823554

Niche evolution and thermal adaptation in the temperate species Drosophila americana.

PubMed

Sillero, N; Reis, M; Vieira, C P; Vieira, J; Morales-Hojas, R

2014-08-01

The study of ecological niche evolution is fundamental for understanding how the environment influences species' geographical distributions and their adaptation to divergent environments. Here, we present a study of the ecological niche, demographic history and thermal performance (locomotor activity, developmental time and fertility/viability) of the temperate species Drosophila americana and its two chromosomal forms. Temperature is the environmental factor that contributes most to the species' and chromosomal forms' ecological niches, although precipitation is also important in the model of the southern populations. The past distribution model of the species predicts a drastic reduction in the suitable area for the distribution of the species during the last glacial maximum (LGM), suggesting a strong bottleneck. However, DNA analyses did not detect a bottleneck signature during the LGM. These contrasting results could indicate that D. americana niche preference evolves with environmental change, and thus, there is no evidence to support niche conservatism in this species. Thermal performance experiments show no difference in the locomotor activity across a temperature range of 15 to 38 °C between flies from the north and the south of its distribution. However, we found significant differences in developmental time and fertility/viability between the two chromosomal forms at the model's optimal temperatures for the two forms. However, results do not indicate that they perform better for the traits studied here in their respective optimal niche temperatures. This suggests that behaviour plays an important role in thermoregulation, supporting the capacity of this species to adapt to different climatic conditions across its latitudinal distribution. © 2014 The Authors. Journal of Evolutionary Biology published by John Wiley & Sons Ltd on behalf of European Society for Evolutionary Biology.

Diversity in Requirement of Genetic and Epigenetic Factors for Centromere Function in Fungi ▿

PubMed Central

Roy, Babhrubahan; Sanyal, Kaustuv

2011-01-01

A centromere is a chromosomal region on which several proteins assemble to form the kinetochore. The centromere-kinetochore complex helps in the attachment of chromosomes to spindle microtubules to mediate segregation of chromosomes to daughter cells during mitosis and meiosis. In several budding yeast species, the centromere forms in a DNA sequence-dependent manner, whereas in most other fungi, factors other than the DNA sequence also determine the centromere location, as centromeres were able to form on nonnative sequences (neocentromeres) when native centromeres were deleted in engineered strains. Thus, in the absence of a common DNA sequence, the cues that have facilitated centromere formation on a specific DNA sequence for millions of years remain a mystery. Kinetochore formation is facilitated by binding of a centromere-specific histone protein member of the centromeric protein A (CENP-A) family that replaces a canonical histone H3 to form a specialized centromeric chromatin structure. However, the process of kinetochore formation on the rapidly evolving and seemingly diverse centromere DNAs in different fungal species is largely unknown. More interestingly, studies in various yeasts suggest that the factors required for de novo centromere formation (establishment) may be different from those required for maintenance (propagation) of an already established centromere. Apart from the DNA sequence and CENP-A, many other factors, such as posttranslational modification (PTM) of histones at centric and pericentric chromatin, RNA interference, and DNA methylation, are also involved in centromere formation, albeit in a species-specific manner. In this review, we discuss how several genetic and epigenetic factors influence the evolution of structure and function of centromeres in fungal species. PMID:21908596

The energy components of stacked chromatin layers explain the morphology, dimensions and mechanical properties of metaphase chromosomes

PubMed Central

Daban, Joan-Ramon

2014-01-01

The measurement of the dimensions of metaphase chromosomes in different animal and plant karyotypes prepared in different laboratories indicates that chromatids have a great variety of sizes which are dependent on the amount of DNA that they contain. However, all chromatids are elongated cylinders that have relatively similar shape proportions (length to diameter ratio approx. 13). To explain this geometry, it is considered that chromosomes are self-organizing structures formed by stacked layers of planar chromatin and that the energy of nucleosome–nucleosome interactions between chromatin layers inside the chromatid is approximately 3.6 × 10−20 J per nucleosome, which is the value reported by other authors for internucleosome interactions in chromatin fibres. Nucleosomes in the periphery of the chromatid are in contact with the medium; they cannot fully interact with bulk chromatin within layers and this generates a surface potential that destabilizes the structure. Chromatids are smooth cylinders because this morphology has a lower surface energy than structures having irregular surfaces. The elongated shape of chromatids can be explained if the destabilizing surface potential is higher in the telomeres (approx. 0.16 mJ m−2) than in the lateral surface (approx. 0.012 mJ m−2). The results obtained by other authors in experimental studies of chromosome mechanics have been used to test the proposed supramolecular structure. It is demonstrated quantitatively that internucleosome interactions between chromatin layers can justify the work required for elastic chromosome stretching (approx. 0.1 pJ for large chromosomes). The high amount of work (up to approx. 10 pJ) required for large chromosome extensions is probably absorbed by chromatin layers through a mechanism involving nucleosome unwrapping. PMID:24402918

Centromeres Off the Hook: Massive Changes in Centromere Size and Structure Following Duplication of CenH3 Gene in Fabeae Species

PubMed Central

Neumann, Pavel; Pavlíková, Zuzana; Koblížková, Andrea; Fuková, Iva; Jedličková, Veronika; Novák, Petr; Macas, Jiří

2015-01-01

In most eukaryotes, centromere is determined by the presence of the centromere-specific histone variant CenH3. Two types of chromosome morphology are generally recognized with respect to centromere organization. Monocentric chromosomes possess a single CenH3-containing domain in primary constriction, whereas holocentric chromosomes lack the primary constriction and display dispersed distribution of CenH3. Recently, metapolycentric chromosomes have been reported in Pisum sativum, representing an intermediate type of centromere organization characterized by multiple CenH3-containing domains distributed across large parts of chromosomes that still form a single constriction. In this work, we show that this type of centromere is also found in other Pisum and closely related Lathyrus species, whereas Vicia and Lens genera, which belong to the same legume tribe Fabeae, possess only monocentric chromosomes. We observed extensive variability in the size of primary constriction and the arrangement of CenH3 domains both between and within individual Pisum and Lathyrus species, with no obvious correlation to genome or chromosome size. Search for CenH3 gene sequences revealed two paralogous variants, CenH3-1 and CenH3-2, which originated from a duplication event in the common ancestor of Fabeae species. The CenH3-1 gene was subsequently lost or silenced in the lineage leading to Vicia and Lens, whereas both genes are retained in Pisum and Lathyrus. Both of these genes appear to have evolved under purifying selection and produce functional CenH3 proteins which are fully colocalized. The findings described here provide the first evidence for a highly dynamic centromere structure within a group of closely related species, challenging previous concepts of centromere evolution. PMID:25771197

Three-Dimensional Maps of All Chromosomes in Human Male Fibroblast Nuclei and Prometaphase Rosettes

PubMed Central

Bolzer, Andreas; Kreth, Gregor; Solovei, Irina; Koehler, Daniela; Saracoglu, Kaan; Fauth, Christine; Müller, Stefan; Eils, Roland; Cremer, Christoph; Speicher, Michael R

2005-01-01

Studies of higher-order chromatin arrangements are an essential part of ongoing attempts to explore changes in epigenome structure and their functional implications during development and cell differentiation. However, the extent and cell-type-specificity of three-dimensional (3D) chromosome arrangements has remained controversial. In order to overcome technical limitations of previous studies, we have developed tools that allow the quantitative 3D positional mapping of all chromosomes simultaneously. We present unequivocal evidence for a probabilistic 3D order of prometaphase chromosomes, as well as of chromosome territories (CTs) in nuclei of quiescent (G0) and cycling (early S-phase) human diploid fibroblasts (46, XY). Radial distance measurements showed a probabilistic, highly nonrandom correlation with chromosome size: small chromosomes—independently of their gene density—were distributed significantly closer to the center of the nucleus or prometaphase rosette, while large chromosomes were located closer to the nuclear or rosette rim. This arrangement was independently confirmed in both human fibroblast and amniotic fluid cell nuclei. Notably, these cell types exhibit flat-ellipsoidal cell nuclei, in contrast to the spherical nuclei of lymphocytes and several other human cell types, for which we and others previously demonstrated gene-density-correlated radial 3D CT arrangements. Modeling of 3D CT arrangements suggests that cell-type-specific differences in radial CT arrangements are not solely due to geometrical constraints that result from nuclear shape differences. We also found gene-density-correlated arrangements of higher-order chromatin shared by all human cell types studied so far. Chromatin domains, which are gene-poor, form a layer beneath the nuclear envelope, while gene-dense chromatin is enriched in the nuclear interior. We discuss the possible functional implications of this finding. PMID:15839726

Chironomus group classification according to the mapping of polytene chromosomes

NASA Astrophysics Data System (ADS)

Salleh, Syafinaz; Kutty, Ahmad Abas

2013-11-01

Chironomus is one of the important genera in Chironomidae family since they are widely diverse and abundance in aquatic ecosystem. Since Chironomus is very diverse, taxonomic work on this genus is very difficult and incomplete. Objective of this study is to form group classification of Chironomus according to the polytene chromosome mapping. The specific characteristics of polytene chromosomes in the salivary gland appeared to be particularly promising for taxonomic diagnosis of chironomid species. Chironomid larvae were collected from pristine sites at Sg. Langat and cultured in laboratory to reach fourth instar stage. The salivary glands were removed from larvae and chromosomes were stained with aceto orcein. Results showed that polytene chromosomes of Chironomus comprise of three long metacentric or submetacentric arms (BF, CD and AE arms) and one short acrocentric (G arm). In regards to nucleolar organizing region (NOR), Balbiani ring (BR), puffings and chromosome rearrangement, a number of four groups of different banding patterns were found. Two groups called as G group A and B have common NOR on arm BF and BR on arm G. However, group A has rearrangement pattern on arm CD and not in group B. This makes group B separated from group A. Another two groups called as groups C and D do not have common NOR on arm BF and also BR on arm G. Groups C and D were separated using arms G and arm AE. At arm G, only group C rearrangement pattern at unit 23c whereas group D was found to have large NOR at arm G and as well as arm AE, only group D has rearrangement pattern at unit 12c. This study indicates that chromosome arrangement could aid in revealing Chironomus diversity.

A New Fractal Model of Chromosome and DNA Processes

NASA Astrophysics Data System (ADS)

Bouallegue, K.

Dynamic chromosome structure remains unknown. Can fractals and chaos be used as new tools to model, identify and generate a structure of chromosomes?Fractals and chaos offer a rich environment for exploring and modeling the complexity of nature. In a sense, fractal geometry is used to describe, model, and analyze the complex forms found in nature. Fractals have also been widely not only in biology but also in medicine. To this effect, a fractal is considered an object that displays self-similarity under magnification and can be constructed using a simple motif (an image repeated on ever-reduced scales).It is worth noting that the problem of identifying a chromosome has become a challenge to find out which one of the models it belongs to. Nevertheless, the several different models (a hierarchical coiling, a folded fiber, and radial loop) have been proposed for mitotic chromosome but have not reached a dynamic model yet.This paper is an attempt to solve topological problems involved in the model of chromosome and DNA processes. By combining the fractal Julia process and the numerical dynamical system, we have finally found out four main points. First, we have developed not only a model of chromosome but also a model of mitosis and one of meiosis. Equally important, we have identified the centromere position through the numerical model captured below. More importantly, in this paper, we have discovered the processes of the cell divisions of both mitosis and meiosis. All in all, the results show that this work could have a strong impact on the welfare of humanity and can lead to a cure of genetic diseases.

Guardian small RNAs and sex determination.

PubMed

Katsuma, Susumu; Kawamoto, Munetaka; Kiuchi, Takashi

2014-01-01

The W chromosome of the silkworm Bombyx mori has been known to determine femaleness for more than 80 years. However, the feminizing gene has not been molecularly identified, because the B. mori W chromosome is almost fully occupied by a large number of transposable elements. The W chromosome-derived feminizing factor of B. mori was recently shown to be a female-specific PIWI-interacting RNA (piRNA). piRNAs are small RNAs that potentially repress invading "non-self" elements (e.g., transposons and virus-like elements) by associating with PIWI proteins. Our results revealed that female-specific piRNA precursors, which we named Fem, are transcribed from the sex-determining region of the W chromosome at the early embryonic stage and are processed into a single mature piRNA (Fem piRNA). Fem piRNA forms a complex with Siwi (silkworm Piwi), which cleaves a protein-coding mRNA transcribed from the Z chromosome. RNA interference of this Z-linked gene, which we named Masc, revealed that this gene encodes a protein required for masculinization and dosage compensation. Fem and Masc both participate in the ping-pong cycle of the piRNA amplification loop by associating with the 2 B. mori PIWI proteins Siwi and BmAgo3 (silkworm Ago3), respectively, indicating that the piRNA-mediated interaction between the 2 sex chromosomes is the primary signal for the B. mori sex determination cascade. Fem is a non-transposable repetitive sequence on the W chromosome, whereas Masc is a single-copy protein-coding gene. It is of great interest how the piRNA system recognizes "self "Masc mRNA as "non-self" RNA.

Defective replication initiation results in locus specific chromosome breakage and a ribosomal RNA deficiency in yeast

PubMed Central

Sanchez, Joseph C.; Kwan, Elizabeth X.; Raghuraman, M. K.; Brewer, Bonita J.

2017-01-01

A form of dwarfism known as Meier-Gorlin syndrome (MGS) is caused by recessive mutations in one of six different genes (ORC1, ORC4, ORC6, CDC6, CDT1, and MCM5). These genes encode components of the pre-replication complex, which assembles at origins of replication prior to S phase. Also, variants in two additional replication initiation genes have joined the list of causative mutations for MGS (Geminin and CDC45). The identity of the causative MGS genetic variants strongly suggests that some aspect of replication is amiss in MGS patients; however, little evidence has been obtained regarding what aspect of chromosome replication is faulty. Since the site of one of the missense mutations in the human ORC4 alleles is conserved between humans and yeast, we sought to determine in what way this single amino acid change affects the process of chromosome replication, by introducing the comparable mutation into yeast (orc4Y232C). We find that yeast cells with the orc4Y232C allele have a prolonged S-phase, due to compromised replication initiation at the ribosomal DNA (rDNA) locus located on chromosome XII. The inability to initiate replication at the rDNA locus results in chromosome breakage and a severely reduced rDNA copy number in the survivors, presumably helping to ensure complete replication of chromosome XII. Although reducing rDNA copy number may help ensure complete chromosome replication, orc4Y232C cells struggle to meet the high demand for ribosomal RNA synthesis. This finding provides additional evidence linking two essential cellular pathways—DNA replication and ribosome biogenesis. PMID:29036220

Defective replication initiation results in locus specific chromosome breakage and a ribosomal RNA deficiency in yeast.

PubMed

Sanchez, Joseph C; Kwan, Elizabeth X; Pohl, Thomas J; Amemiya, Haley M; Raghuraman, M K; Brewer, Bonita J

2017-10-01

A form of dwarfism known as Meier-Gorlin syndrome (MGS) is caused by recessive mutations in one of six different genes (ORC1, ORC4, ORC6, CDC6, CDT1, and MCM5). These genes encode components of the pre-replication complex, which assembles at origins of replication prior to S phase. Also, variants in two additional replication initiation genes have joined the list of causative mutations for MGS (Geminin and CDC45). The identity of the causative MGS genetic variants strongly suggests that some aspect of replication is amiss in MGS patients; however, little evidence has been obtained regarding what aspect of chromosome replication is faulty. Since the site of one of the missense mutations in the human ORC4 alleles is conserved between humans and yeast, we sought to determine in what way this single amino acid change affects the process of chromosome replication, by introducing the comparable mutation into yeast (orc4Y232C). We find that yeast cells with the orc4Y232C allele have a prolonged S-phase, due to compromised replication initiation at the ribosomal DNA (rDNA) locus located on chromosome XII. The inability to initiate replication at the rDNA locus results in chromosome breakage and a severely reduced rDNA copy number in the survivors, presumably helping to ensure complete replication of chromosome XII. Although reducing rDNA copy number may help ensure complete chromosome replication, orc4Y232C cells struggle to meet the high demand for ribosomal RNA synthesis. This finding provides additional evidence linking two essential cellular pathways-DNA replication and ribosome biogenesis.

Cytological diploidization of paleopolyploid genus Zea: Divergence between homoeologous chromosomes or activity of pairing regulator genes?

PubMed Central

2018-01-01

Cytological diploidization process is different in autopolyploid and allopolyploid species. Colchicine applied at the onset of meiosis suppresses the effect of pairing regulator genes resulting multivalents formation in bivalent-forming species. Colchicine treated maizes (4x = 2n = 20, AmAmBmBm) showed up to 5IV, suggesting pairing between chromosomes from genomes homoeologous Am and Bm. In untreated individuals of the alloautooctoploid Zea perennis (8x = 2n = 40, ApApAp´Ap´Bp1Bp1Bp2Bp2) the most frequent configuration was 5IV+10II (formed by A and B genomes, respectively). The colchicine treated Z. perennis show up to 10IV revealing higher affinity within genomes A and B, but any homology among them. These results suggest the presence of a paring regulator locus (PrZ) in maize and Z. perennis, whose expression is suppressed by colchicine. It could be postulated that in Z. perennis, PrZ would affect independently the genomes A and B, being relevant the threshold of homology, the fidelity of pairing in each genomes and the ploidy level. Cytological analysis of the treated hexaploid hybrids (6x = 2n = 30), with Z. perennis as a parental, strongly suggests that PrZ is less effective in only one doses. This conclusion was reinforced by the homoeologous pairing observed in untreated dihaploid maizes, which showed up to 5II. Meiotic behaviour of individuals treated with different doses of colchicine allowed to postulate that PrZ affect the homoeologous association by controlling entire genomes (Am or Bm) rather than individual chromosomes. Based on cytological and statistical results it is possible to propose that the cytological diploidization in Zea species occurs by restriction of pairing between homoeologous chromosomes or by genetical divergence of the homoeologous chromosomes, as was observed in untreated Z. mays ssp. parviglumis. These are independent but complementary systems and could be acting jointly in the same nucleus. PMID:29293518

A novel mechanism of EML4-ALK rearrangement mediated by chromothripsis in a patient-derived cell line.

PubMed

Kodama, Tatsushi; Motoi, Noriko; Ninomiya, Hironori; Sakamoto, Hiroshi; Kitada, Kunio; Tsukaguchi, Toshiyuki; Satoh, Yasuko; Nomura, Kimie; Nagano, Hiroko; Ishii, Nobuya; Terui, Yasuhito; Hatake, Kiyohiko; Ishikawa, Yuichi

2014-11-01

EML4-ALK is a driver oncogene in non-small-cell lung cancer (NSCLC) and has been developed into a promising molecular target for antitumor agents. Although EML4-ALK is reported to be formed by inversion of chromosome 2, other mechanisms of this gene fusion remain unknown. This study aimed to examine the mechanism of EML4-ALK rearrangement using a novel cell line with the EML4-ALK fusion gene. An EML4-ALK-positive cell line, termed JFCR-LC649, was established from pleomorphic carcinoma, a rare subtype of NSCLC. We investigated the chromosomal aberrations using fluorescence in situ hybridization and comparative genomic hybridization (CGH). Alectinib/CH5424802, a selective ALK inhibitor, was evaluated in the antitumor activity against JFCR-LC649 in vitro and in vivo xenograft model. We established an EML4-ALK-positive cell line, termed JFCR-LC649, derived from a patient with NSCLC and revealed that the JFCR-LC649 cells harbor variant 3 of the EML4-ALK fusion with twofold copy number gain. Interestingly, comparative genomic hybridization and metaphase-fluorescence in situ hybridization analysis showed that in addition to two normal chromosome 2, JFCR-LC649 cells contained two aberrant chromosome 2 that were fragmented and scattered. These observations provided the first evidence that EML4-ALK fusion in JFCR-LC649 cells was formed in chromosome 2 by a distinct mechanism of genomic rearrangement, termed chromothripsis. Furthermore, a selective ALK inhibitor alectinib/CH5424802 suppressed tumor growth of the JFCR-LC649 cells through inhibition of phospho-ALK in vitro and in vivo in a xenograft model. Our results suggested that chromothripsis may be a mechanism of oncogenic rearrangement of EML4-ALK. In addition, alectinib was effective against EML4-ALK-positive tumors with ALK copy number gain mediated by chromothripsis.

Cytological diploidization of paleopolyploid genus Zea: Divergence between homoeologous chromosomes or activity of pairing regulator genes?

PubMed

Poggio, Lidia; González, Graciela Esther

2018-01-01

Cytological diploidization process is different in autopolyploid and allopolyploid species. Colchicine applied at the onset of meiosis suppresses the effect of pairing regulator genes resulting multivalents formation in bivalent-forming species. Colchicine treated maizes (4x = 2n = 20, AmAmBmBm) showed up to 5IV, suggesting pairing between chromosomes from genomes homoeologous Am and Bm. In untreated individuals of the alloautooctoploid Zea perennis (8x = 2n = 40, ApApAp´Ap´Bp1Bp1Bp2Bp2) the most frequent configuration was 5IV+10II (formed by A and B genomes, respectively). The colchicine treated Z. perennis show up to 10IV revealing higher affinity within genomes A and B, but any homology among them. These results suggest the presence of a paring regulator locus (PrZ) in maize and Z. perennis, whose expression is suppressed by colchicine. It could be postulated that in Z. perennis, PrZ would affect independently the genomes A and B, being relevant the threshold of homology, the fidelity of pairing in each genomes and the ploidy level. Cytological analysis of the treated hexaploid hybrids (6x = 2n = 30), with Z. perennis as a parental, strongly suggests that PrZ is less effective in only one doses. This conclusion was reinforced by the homoeologous pairing observed in untreated dihaploid maizes, which showed up to 5II. Meiotic behaviour of individuals treated with different doses of colchicine allowed to postulate that PrZ affect the homoeologous association by controlling entire genomes (Am or Bm) rather than individual chromosomes. Based on cytological and statistical results it is possible to propose that the cytological diploidization in Zea species occurs by restriction of pairing between homoeologous chromosomes or by genetical divergence of the homoeologous chromosomes, as was observed in untreated Z. mays ssp. parviglumis. These are independent but complementary systems and could be acting jointly in the same nucleus.

Clinically relevant genetic biomarkers from the brain in alcoholism with representation on high resolution chromosome ideograms.

PubMed

Manzardo, Ann M; McGuire, Austen; Butler, Merlin G

2015-04-15

Alcoholism arises from combined effects of multiple biological factors including genetic and non-genetic causes with gene/environmental interaction. Intensive research and advanced genetic technology has generated a long list of genes and biomarkers involved in alcoholism neuropathology. These markers reflect complex overlapping and competing effects of possibly hundreds of genes which impact brain structure, function, biochemical alcohol processing, sensitivity and risk for dependence. We compiled a tabular list of clinically relevant genetic biomarkers for alcoholism targeting expression disturbances in the human brain through an extensive search of keywords related to alcoholism, alcohol abuse, and genetics from peer reviewed medical research articles and related nationally sponsored websites. Gene symbols were then placed on high resolution human chromosome ideograms with gene descriptions in tabular form. We identified 337 clinically relevant genetic biomarkers and candidate genes for alcoholism and alcohol-responsiveness from human brain research. Genetic biomarkers included neurotransmitter pathways associated with brain reward processes for dopaminergic (e.g., DRD2, MAOA, and COMT), serotoninergic (e.g., HTR3A, HTR1B, HTR3B, and SLC6A4), GABAergic (e.g., GABRA1, GABRA2, and GABRG1), glutaminergic (GAD1, GRIK3, and GRIN2C) and opioid (e.g., OPRM1, OPRD1, and OPRK1) pathways which presumably impact reinforcing properties of alcohol. Gene level disturbances in cellular and molecular networks impacted by alcohol and alcoholism pathology include transketolase (TKT), transferrin (TF), and myelin (e.g., MBP, MOBP, and MOG). High resolution chromosome ideograms provide investigators, physicians, geneticists and counselors a convenient visual image of the distribution of alcoholism genetic biomarkers from brain research with alphabetical listing of genes in tabular form allowing comparison between alcoholism-related phenotypes, and clinically-relevant alcoholism gene(s) at the chromosome band level to guide research, diagnosis, and treatment. Chromosome ideograms may facilitate gene-based personalized counseling of alcohol dependent individuals and their families. Copyright © 2015 Elsevier B.V. All rights reserved.

Characterization of a complex context containing mecA but lacking genes encoding cassette chromosome recombinases in Staphylococcus haemolyticus

PubMed Central

2013-01-01

Background Methicillin resistance determinant mecA is generally transferred by SCCmec elements. However, the mecA gene might not be carried by a SCCmec in a Staphylococcus haemolyticus clinical isolate, WCH1, as no cassette chromosome recombinase genes were detected. Therefore, the genetic context of mecA in WCH1 was investigated. Results A 40-kb region containing mecA was obtained from WCH1, bounded by orfX at one end and several orfs of S. haemolyticus core chromosome at the other. This 40-kb region was very complex in structure with multiple genetic components that appeared to have different origins. For instance, the 3.7-kb structure adjacent to orfX was almost identical to that on the chromosome of Staphylococcus epidermidis RP62a but was absent from S. haemolyticus JCSC1435. Terminal inverted repeats of SCC were found but no ccr genes could be detected. mecA was bracketed by two copies of IS431, which was flanked by 8-bp direct target repeat sequence (DR). Conclusions The presence of 8-bp DR suggests that the two copies of IS431 might have formed a composite transposon for mobilizing mecA. This finding is of significance as multiple copies of IS431 are commonly present in the contexts of mecA, which might have the potential to form various composite transposons that could mediate the mobilization of mecA. This study also provides an explanation for the absence of ccr in some staphylococci isolates carrying mecA. PMID:23521926

Characterization of a complex context containing mecA but lacking genes encoding cassette chromosome recombinases in Staphylococcus haemolyticus.

PubMed

Zong, Zhiyong

2013-03-22

Methicillin resistance determinant mecA is generally transferred by SCCmec elements. However, the mecA gene might not be carried by a SCCmec in a Staphylococcus haemolyticus clinical isolate, WCH1, as no cassette chromosome recombinase genes were detected. Therefore, the genetic context of mecA in WCH1 was investigated. A 40-kb region containing mecA was obtained from WCH1, bounded by orfX at one end and several orfs of S. haemolyticus core chromosome at the other. This 40-kb region was very complex in structure with multiple genetic components that appeared to have different origins. For instance, the 3.7-kb structure adjacent to orfX was almost identical to that on the chromosome of Staphylococcus epidermidis RP62a but was absent from S. haemolyticus JCSC1435. Terminal inverted repeats of SCC were found but no ccr genes could be detected. mecA was bracketed by two copies of IS431, which was flanked by 8-bp direct target repeat sequence (DR). The presence of 8-bp DR suggests that the two copies of IS431 might have formed a composite transposon for mobilizing mecA. This finding is of significance as multiple copies of IS431 are commonly present in the contexts of mecA, which might have the potential to form various composite transposons that could mediate the mobilization of mecA. This study also provides an explanation for the absence of ccr in some staphylococci isolates carrying mecA.

Characterization of hypersensitive resistance to bacterial spot race T3 (Xanthomonas perforans) from tomato accession PI 128216.

PubMed

Robbins, Matthew D; Darrigues, Audrey; Sim, Sung-Chur; Masud, Mohammed Abu Taher; Francis, David M

2009-09-01

Bacterial spot of tomato is caused by four species of Xanthomonas. The accession PI 128216 (Solanum pimpinellifolium) displays a hypersensitive reaction (HR) to race T3 strains (predominantely Xanthomonas perforans). We developed an inbred backcross (IBC) population (BC(2)S(5), 178 families) derived from PI 128216 and OH88119 (S. lycopersicum) as the susceptible recurrent parent for simultaneous introgression and genetic analysis of the HR response. These IBC families were evaluated in the greenhouse for HR to race T3 strain Xcv761. The IBC population was genotyped with molecular markers distributed throughout the genome in order to identify candidate loci conferring resistance. We treated the IBC population as a hypothesis forming generation to guide validation in subsequent crosses. Nonparametric analysis identified an association between HR and markers clustered on chromosome 11 (P < 0.05 to 0.0001) and chromosome 6 (0.04 > P > 0.002). Further analysis of the IBC population suggested that markers on chromosome 6 and 11 failed to assort independently, a phenomenon known as gametic phase disequilibrium. Therefore, to validate marker-trait linkages, resistant IBC plants were crossed with OH88119 and BC(3)F(2) progeny were evaluated for HR in the greenhouse. In these subsequent populations, the HR response was associated with the chromosome 11 markers (P < 0.0002) but not with the markers on chromosome 6 (P > 0.25). Independent F(2) families were developed by crossing resistant IBC lines to OH8245, OH88119, and OH7530. These populations were genotyped, organized into classes based on chromosome 11 markers, and evaluated for resistance in the field. The PI 128216 locus on chromosome 11 provided resistance that was dependent on gene dosage and genetic background. These results define a single locus, Rx-4, from PI 128216, which provides resistance to bacterial spot race T3, has additive gene action, and is located on chromosome 11.

Phylogenetic reconstruction by cross-species chromosome painting and G-banding in four species of Phyllostomini tribe (Chiroptera, Phyllostomidae) in the Brazilian Amazon: an independent evidence for monophyly.

PubMed

Ribas, Talita Fernanda Augusto; Rodrigues, Luis Reginaldo Ribeiro; Nagamachi, Cleusa Yoshiko; Gomes, Anderson José Baia; Rissino, Jorge das Dores; O'Brien, Patricia Caroline Mary; Yang, Fengtang; Ferguson-Smith, Malcolm Andrew; Pieczarka, Julio Cesar

2015-01-01

The subfamily Phyllostominae comprises taxa with a variety of feeding strategies. From the cytogenetic point of view, Phyllostominae shows different rates of chromosomal evolution between genera, with Phyllostomus hastatus probably retaining the ancestral karyotype for the subfamily. Since chromosomal rearrangements occur rarely in the genome and have great value as phylogenetic markers and in taxonomic characterization, we analyzed three species: Lophostoma silvicola (LSI), Phyllostomus discolor (PDI) and Tonatia saurophila (TSA), representing the tribe Phyllostomini, collected in the Amazon region, by classic and molecular cytogenetic techniques in order to reconstruct the phylogenetic relationships within this tribe. LSA has a karyotype of 2n=34 and FN=60, PDI has 2n=32 and FN=60 and TSA has 2n=16 and FN=20. Comparative analysis using G-banding and chromosome painting show that the karyotypic complement of TSA is highly rearranged relative to LSI and PHA, while LSI, PHA and PDI have similar karyotypes, differing by only three chromosome pairs. Nearly all chromosomes of PDI and PHA were conserved in toto, except for chromosome 15 that was changed by a pericentric inversion. A strongly supported phylogeny (bootstrap=100 and Bremer=10 steps), confirms the monophyly of Phyllostomini. In agreement with molecular topologies, TSA was in the basal position, while PHA and LSI formed sister taxa. A few ancestral syntenies are conserved without rearrangements and most associations are autapomorphic traits for Tonatia or plesiomorphic for the three genera analyzed here. The karyotype of TSA is highly derived in relation to that of other phyllostomid bats, differing from the supposed ancestral karyotype of Phyllostomidae by multiple rearrangements. Phylogenies based on chromosomal data are independent evidence for the monophyly of tribe Phyllostomini as determined by molecular topologies and provide additional support for the paraphyly of the genus Tonatia by the exclusion of the genus Lophostoma.

Multiple Pairwise Analysis of Non-homologous Centromere Coupling Reveals Preferential Chromosome Size-Dependent Interactions and a Role for Bouquet Formation in Establishing the Interaction Pattern

PubMed Central

Lefrançois, Philippe; Rockmill, Beth; Xie, Pingxing; Roeder, G. Shirleen; Snyder, Michael

2016-01-01

During meiosis, chromosomes undergo a homology search in order to locate their homolog to form stable pairs and exchange genetic material. Early in prophase, chromosomes associate in mostly non-homologous pairs, tethered only at their centromeres. This phenomenon, conserved through higher eukaryotes, is termed centromere coupling in budding yeast. Both initiation of recombination and the presence of homologs are dispensable for centromere coupling (occurring in spo11 mutants and haploids induced to undergo meiosis) but the presence of the synaptonemal complex (SC) protein Zip1 is required. The nature and mechanism of coupling have yet to be elucidated. Here we present the first pairwise analysis of centromere coupling in an effort to uncover underlying rules that may exist within these non-homologous interactions. We designed a novel chromosome conformation capture (3C)-based assay to detect all possible interactions between non-homologous yeast centromeres during early meiosis. Using this variant of 3C-qPCR, we found a size-dependent interaction pattern, in which chromosomes assort preferentially with chromosomes of similar sizes, in haploid and diploid spo11 cells, but not in a coupling-defective mutant (spo11 zip1 haploid and diploid yeast). This pattern is also observed in wild-type diploids early in meiosis but disappears as meiosis progresses and homologous chromosomes pair. We found no evidence to support the notion that ancestral centromere homology plays a role in pattern establishment in S. cerevisiae post-genome duplication. Moreover, we found a role for the meiotic bouquet in establishing the size dependence of centromere coupling, as abolishing bouquet (using the bouquet-defective spo11 ndj1 mutant) reduces it. Coupling in spo11 ndj1 rather follows telomere clustering preferences. We propose that a chromosome size preference for centromere coupling helps establish efficient homolog recognition. PMID:27768699

Phylogenetic Reconstruction by Cross-Species Chromosome Painting and G-Banding in Four Species of Phyllostomini Tribe (Chiroptera, Phyllostomidae) in the Brazilian Amazon: An Independent Evidence for Monophyly

PubMed Central

Ribas, Talita Fernanda Augusto; Rodrigues, Luis Reginaldo Ribeiro; Nagamachi, Cleusa Yoshiko; Gomes, Anderson José Baia; Rissino, Jorge das Dores; O'Brien, Patricia Caroline Mary; Yang, Fengtang; Ferguson-Smith, Malcolm Andrew; Pieczarka, Julio Cesar

2015-01-01

The subfamily Phyllostominae comprises taxa with a variety of feeding strategies. From the cytogenetic point of view, Phyllostominae shows different rates of chromosomal evolution between genera, with Phyllostomus hastatus probably retaining the ancestral karyotype for the subfamily. Since chromosomal rearrangements occur rarely in the genome and have great value as phylogenetic markers and in taxonomic characterization, we analyzed three species: Lophostoma silvicola (LSI), Phyllostomus discolor (PDI) and Tonatia saurophila (TSA), representing the tribe Phyllostomini, collected in the Amazon region, by classic and molecular cytogenetic techniques in order to reconstruct the phylogenetic relationships within this tribe. LSA has a karyotype of 2n=34 and FN=60, PDI has 2n=32 and FN=60 and TSA has 2n=16 and FN=20. Comparative analysis using G-banding and chromosome painting show that the karyotypic complement of TSA is highly rearranged relative to LSI and PHA, while LSI, PHA and PDI have similar karyotypes, differing by only three chromosome pairs. Nearly all chromosomes of PDI and PHA were conserved in toto, except for chromosome 15 that was changed by a pericentric inversion. A strongly supported phylogeny (bootstrap=100 and Bremer=10 steps), confirms the monophyly of Phyllostomini. In agreement with molecular topologies, TSA was in the basal position, while PHA and LSI formed sister taxa. A few ancestral syntenies are conserved without rearrangements and most associations are autapomorphic traits for Tonatia or plesiomorphic for the three genera analyzed here. The karyotype of TSA is highly derived in relation to that of other phyllostomid bats, differing from the supposed ancestral karyotype of Phyllostomidae by multiple rearrangements. Phylogenies based on chromosomal data are independent evidence for the monophyly of tribe Phyllostomini as determined by molecular topologies and provide additional support for the paraphyly of the genus Tonatia by the exclusion of the genus Lophostoma. PMID:25806812

Evidence That Masking of Synapsis Imperfections Counterbalances Quality Control to Promote Efficient Meiosis

PubMed Central

Mlynarczyk-Evans, Susanna; Roelens, Baptiste; Villeneuve, Anne M.

2013-01-01

Reduction in ploidy to generate haploid gametes during sexual reproduction is accomplished by the specialized cell division program of meiosis. Pairing between homologous chromosomes and assembly of the synaptonemal complex at their interface (synapsis) represent intermediate steps in the meiotic program that are essential to form crossover recombination-based linkages between homologs, which in turn enable segregation of the homologs to opposite poles at the meiosis I division. Here, we challenge the mechanisms of pairing and synapsis during C. elegans meiosis by disrupting the normal 1∶1 correspondence between homologs through karyotype manipulation. Using a combination of cytological tools, including S-phase labeling to specifically identify X chromosome territories in highly synchronous cohorts of nuclei and 3D rendering to visualize meiotic chromosome structures and organization, our analysis of trisomic (triplo-X) and polyploid meiosis provides insight into the principles governing pairing and synapsis and how the meiotic program is “wired” to maximize successful sexual reproduction. We show that chromosomes sort into homologous groups regardless of chromosome number, then preferentially achieve pairwise synapsis during a period of active chromosome mobilization. Further, comparisons of synapsis configurations in triplo-X germ cells that are proficient or defective for initiating recombination suggest a role for recombination in restricting chromosomal interactions to a pairwise state. Increased numbers of homologs prolong markers of the chromosome mobilization phase and/or boost germline apoptosis, consistent with triggering quality control mechanisms that promote resolution of synapsis problems and/or cull meiocytes containing synapsis defects. However, we also uncover evidence for the existence of mechanisms that “mask” defects, thus allowing resumption of prophase progression and survival of germ cells despite some asynapsis. We propose that coupling of saturable masking mechanisms with stringent quality controls maximizes meiotic success by making progression and survival dependent on achieving a level of synapsis sufficient for crossover formation without requiring perfect synapsis. PMID:24339786

[A longitudinal entomologic survey on the transmission of malaria in Ouagadougou (Burkina Faso)].

PubMed

Rossi, P; Belli, A; Mancini, L; Sabatinelli, G

1986-04-01

A longitudinal entomological malaria survey was carried out in five zones of the town of Ouagadougou, Burkina Faso, and in three neighbouring villages. The main vector is Anopheles gambiae s.l. with An. funestus having a role in some localities during the dry season. Pyrethrum spray catches were carried out once or twice per month to determine variations in vector density. Inoculation rates were estimated from the number of blood-fed vectors per man and from the sporozoite rates. Larval sampling was routinely carried out all over the urban area in order to map the larval breeding sites. Widely different degrees of malaria transmission were documented in the urban area mainly related to the spatial and temporal distribution of An. gambiae larval breeding sites. Higher inoculation rates, depending both on higher vector densities and sporozoite rates, were documented in the villages.

Seasonality, Blood Feeding Behavior, and Transmission of Plasmodium Falciparum by Anopheles Arabiensis after an Extended Drought In Southern Zambia

PubMed Central

Thuma, Philip E.; Mharakurwa, Sungano; Norris, Douglas E.

2014-01-01

Transmission of Plasmodium falciparum is hyperendemic in southern Zambia. However, no data on the entomologic aspects of malaria transmission have been published from Zambia in more than 25 years. We evaluated seasonal malaria transmission by Anopheles arabiensis and An. funestus s.s. and characterized the blood feeding behavior of An. arabiensis in two village areas. Transmission during the 2004–2005 rainy season was nearly zero because of widespread drought. During 2005–2006, the estimated entomologic inoculation rate values were 1.6 and 18.3 infective bites per person per transmission season in each of the two village areas, respectively. Finally, with a human blood index of 0.923, An. arabiensis was substantially more anthropophilic in our study area than comparable samples of indoor-resting An. arabiensis throughout Africa and was the primary vector responsible for transmission of P. falciparum. PMID:17297034

SAP-like domain in nucleolar spindle associated protein mediates mitotic chromosome loading as well as interphase chromatin interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verbakel, Werner, E-mail: werner.verbakel@chem.kuleuven.be; Carmeliet, Geert, E-mail: geert.carmeliet@med.kuleuven.be; Engelborghs, Yves, E-mail: yves.engelborghs@fys.kuleuven.be

2011-08-12

Highlights: {yields} The SAP-like domain in NuSAP is a functional DNA-binding domain with preference for dsDNA. {yields} This SAP-like domain is essential for chromosome loading during early mitosis. {yields} NuSAP is highly dynamic on mitotic chromatin, as evident from photobleaching experiments. {yields} The SAP-like domain also mediates NuSAP-chromatin interaction in interphase nucleoplasm. -- Abstract: Nucleolar spindle associated protein (NuSAP) is a microtubule-stabilizing protein that localizes to chromosome arms and chromosome-proximal microtubules during mitosis and to the nucleus, with enrichment in the nucleoli, during interphase. The critical function of NuSAP is underscored by the finding that its depletion in HeLa cellsmore » results in various mitotic defects. Moreover, NuSAP is found overexpressed in multiple cancers and its expression levels often correlate with the aggressiveness of cancer. Due to its localization on chromosome arms and combination of microtubule-stabilizing and DNA-binding properties, NuSAP takes a special place within the extensive group of spindle assembly factors. In this study, we identify a SAP-like domain that shows DNA binding in vitro with a preference for dsDNA. Deletion of the SAP-like domain abolishes chromosome arm binding of NuSAP during mitosis, but is not sufficient to abrogate its chromosome-proximal localization after anaphase onset. Fluorescence recovery after photobleaching experiments revealed the highly dynamic nature of this NuSAP-chromatin interaction during mitosis. In interphase cells, NuSAP also interacts with chromatin through its SAP-like domain, as evident from its enrichment on dense chromatin regions and intranuclear mobility, measured by fluorescence correlation spectroscopy. The obtained results are in agreement with a model where NuSAP dynamically stabilizes newly formed microtubules on mitotic chromosomes to enhance chromosome positioning without immobilizing these microtubules. Interphase NuSAP-chromatin interaction suggests additional functions for NuSAP, as recently identified for other nuclear spindle assembly factors with a role in gene expression or DNA damage response.« less

Principles of the highly ordered arrangement of metaphase I bivalents in spermatocytes of Agrodiaetus (Insecta, Lepidoptera).

PubMed

Lukhtanov, Vladimir A; Dantchenko, Alexander V

2002-01-01

We have investigated the nature of highly ordered bivalent arrangement in lepidopteran spermatocytes by analysing and comparing the patterns of bivalent distribution in intact metaphase I plates of 24 closely related species of the genus Agrodiaetus (Lycaenidae). The studied species greatly differed in haploid chromosome numbers (from n = 13 to n = 90) and in the structure of their karyotypes. We found that the larger the bivalent, the closer to the centre of the metaphase plate it was situated. In species with a high chromosome number and asymmetrical karyotype structure, the largest bivalent was located in the centre of the circular metaphase plate. Bivalents of equal size were approximately equidistant from the centre of the metaphase plate and formed concentric circles around the largest bivalent. These principles are diametrically different from those known in the majority of other animals and plants, in which the smallest elements of the chromosome set are situated in the centre of metaphase plate. The only exception from the above principles was observed in spermatocytes of A. surakovi which were heterozygous for reciprocal translocation involving two or three chromosome pairs. In addition to one large bivalent, the heterozygous cells had a multivalent, the size of which was comparable to or even exceeded that of the largest bivalentin the karyotype. In spite of thelarge size, the multivalent was always situated at the periphery of metaphase plate. This indicated that the chromosome size itself is not the only factor determining the bivalent position. We also found that the structure of the metaphase plate is fundamentally different in mitotic and meiotic cells of Agrodiaetus. In spermatogonial metaphase, chromosomes were tightly brought together, forming a dense compact disk, whereas during metaphase I of spermatocytes, all bivalents were clearly separated from each other, and the distance between adjacent bivalents varied from 0.4 to 1.5 microm. Based on the above findings, we proposed a model of bivalent distribution in the Lepidoptera. According to the model, during congregation in the prometaphase stage there is a centripetal movement of bivalents made by a force directed to the centre of the metaphase plate transverse to the spindle. This force is proportional to the kinetochore size of a particular bivalent. The Lepidoptera have a special near-holokinetic type of chromosome organisation. Therefore, large bivalents having large kinetochores are situated in the central part of metaphase plate. Another possible factor affecting the bivalent position is the interaction of bivalents with the cisternae of the membrane system compartmentalising the intraspindle space.

Revealing Long-Range Interconnected Hubs in Human Chromatin Interaction Data Using Graph Theory

NASA Astrophysics Data System (ADS)

Boulos, R. E.; Arneodo, A.; Jensen, P.; Audit, B.

2013-09-01

We use graph theory to analyze chromatin interaction (Hi-C) data in the human genome. We show that a key functional feature of the genome—“master” replication origins—corresponds to DNA loci of maximal network centrality. These loci form a set of interconnected hubs both within chromosomes and between different chromosomes. Our results open the way to a fruitful use of graph theory concepts to decipher DNA structural organization in relation to genome functions such as replication and transcription. This quantitative information should prove useful to discriminate between possible polymer models of nuclear organization.

Mechanisms and consequences of aneuploidy and chromosome instability in the aging brain.

PubMed

Andriani, Grasiella A; Vijg, Jan; Montagna, Cristina

2017-01-01

Aneuploidy and polyploidy are a form of Genomic Instability (GIN) known as Chromosomal Instability (CIN) characterized by sporadic abnormalities in chromosome copy numbers. Aneuploidy is commonly linked to pathological states. It is a hallmark of spontaneous abortions and birth defects and it is observed virtually in every human tumor, therefore being generally regarded as detrimental for the development or the maturation of tissues under physiological conditions. Polyploidy however, occurs as part of normal physiological processes during maturation and differentiation of some mammalian cell types. Surprisingly, high levels of aneuploidy are present in the brain, and their frequency increases with age suggesting that the brain is able to maintain its functionality in the presence of high levels of mosaic aneuploidy. Because somatic aneuploidy with age can reach exceptionally high levels, it is likely to have long-term adverse effects in this organ. We describe the mechanisms accountable for an abnormal DNA content with a particular emphasis on the CNS where cell division is limited. Next, we briefly summarize the types of GIN known to date and discuss how they interconnect with CIN. Lastly we highlight how several forms of CIN may contribute to genetic variation, tissue degeneration and disease in the CNS. Copyright © 2016. Published by Elsevier B.V.

The iSelect 9 K SNP analysis revealed polyploidization induced revolutionary changes and intense human selection causing strong haplotype blocks in wheat.

PubMed

Hao, Chenyang; Wang, Yuquan; Chao, Shiaoman; Li, Tian; Liu, Hongxia; Wang, Lanfen; Zhang, Xueyong

2017-01-30

A Chinese wheat mini core collection was genotyped using the wheat 9 K iSelect SNP array. Total 2420 and 2396 polymorphic SNPs were detected on the A and the B genome chromosomes, which formed 878 haplotype blocks. There were more blocks in the B genome, but the average block size was significantly (P < 0.05) smaller than those in the A genome. Intense selection (domestication and breeding) had a stronger effect on the A than on the B genome chromosomes. Based on the genetic pedigrees, many blocks can be traced back to a well-known Strampelli cross, which was made one century ago. Furthermore, polyploidization of wheat (both tetraploidization and hexaploidization) induced revolutionary changes in both the A and the B genomes, with a greater increase of gene diversity compared to their diploid ancestors. Modern breeding has dramatically increased diversity in the gene coding regions, though obvious blocks were formed on most of the chromosomes in both tetraploid and hexaploid wheats. Tag-SNP markers identified in this study can be used for marker assisted selection using haplotype blocks as a wheat breeding strategy. This strategy can also be employed to facilitate genome selection in other self-pollinating crop species.

A heterochromatin domain forms gradually at a new telomere and is dynamic at stable telomeres.

PubMed

Wang, Jinyu; Eisenstatt, Jessica R; Audry, Julien; Cornelius, Kristen; Shaughnessy, Matthew; Berkner, Kathleen L; Runge, Kurt W

2018-05-21

Heterochromatin domains play important roles in chromosome biology, organismal development and aging, including centromere function, mammalian female X-chromosome inactivation and senescence-associated heterochromatin foci. In the fission yeast Schizosaccharomyces pombe and metazoans, heterochromatin contains histone H3 that is dimethylated at lysine 9. While factors required for heterochromatin have been identified, the dynamics of heterochromatin formation are poorly understood. Telomeres convert adjacent chromatin into heterochromatin. To form a new heterochromatic region in S. pombe , an inducible DNA double-strand break (DSB) was engineered next to 48 bp of telomere repeats in euchromatin, which caused formation of a new telomere and the establishment and gradual spreading of a new heterochromatin domain. However, spreading was dynamic even after the telomere had reached its stable length, with reporter genes within the heterochromatin domain showing variegated expression. The system also revealed the presence of repeats located near the boundaries of euchromatin and heterochromatin that are oriented to allow the efficient healing of a euchromatic DSB to cap the chromosome end with a new telomere. Telomere formation in S. pombe therefore reveals novel aspects of heterochromatin dynamics and failsafe mechanisms to repair subtelomeric breaks, with implications for similar processes in metazoan genomes. Copyright © 2018 Wang et al.

The fate of deleted DNA produced during programmed genomic deletion events in Tetrahymena thermophila.

PubMed Central

Saveliev, S V; Cox, M M

1994-01-01

Thousands of DNA deletion events occur during macronuclear development in the ciliate Tetrahymena thermophila. In two deleted genomic regions, designated M and R, the eliminated sequences form circles that can be detected by PCR. However, the circles are not normal products of the reaction pathway. The circular forms occur at very low levels in conjugating cells, but are stable. Sequencing analysis showed that many of the circles (as many as 50% of those examined) reflected a precise deletion in the M and R regions. The remaining circles were either smaller or larger and contained varying lengths of sequences derived from the chromosomal DNA surrounding the eliminated region. The chromosomal junctions left behind after deletion were more precise, although deletions in either the M or R regions can generate any of several alternative junctions (1). Some new chromosomal junctions were detected in the present study. The results suggest that the deleted segment is released as a linear DNA species that is degraded rapidly. The species is only rarely converted to the stable circles we detect. The deletion mechanism is different from those proposed for deletion events in hypotrichous ciliates (2-4), and does not reflect a conservative site-specific recombination process such as that promoted by the bacteriophage lambda integrase (5). Images PMID:7838724

A Conserved Mode of Protein Recognition and Binding in a ParD−ParE Toxin−Antitoxin Complex

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dalton, Kevin M.; Crosson, Sean

2010-05-06

Toxin-antitoxin (TA) systems form a ubiquitous class of prokaryotic proteins with functional roles in plasmid inheritance, environmental stress response, and cell development. ParDE family TA systems are broadly conserved on plasmids and bacterial chromosomes and have been well characterized as genetic elements that promote stable plasmid inheritance. We present a crystal structure of a chromosomally encoded ParD-ParE complex from Caulobacter crescentus at 2.6 {angstrom} resolution. This TA system forms an {alpha}{sub 2}{beta}{sub 2} heterotetramer in the crystal and in solution. The toxin-antitoxin binding interface reveals extensive polar and hydrophobic contacts of ParD antitoxin helices with a conserved recognition and bindingmore » groove on the ParE toxin. A cross-species comparison of this complex structure with related toxin structures identified an antitoxin recognition and binding subdomain that is conserved between distantly related members of the RelE/ParE toxin superfamily despite a low level of overall primary sequence identity. We further demonstrate that ParD antitoxin is dimeric, stably folded, and largely helical when not bound to ParE toxin. Thus, the paradigmatic model in which antitoxin undergoes a disorder-to-order transition upon toxin binding does not apply to this chromosomal ParD-ParE TA system.« less

A novel locus for Usher syndrome type I, USH1G, maps to chromosome 17q24-25.

PubMed

Mustapha, Mirna; Chouery, Eliane; Torchard-Pagnez, Delphine; Nouaille, Sylvie; Khrais, Awni; Sayegh, Fouad N; Mégarbané, André; Loiselet, Jacques; Lathrop, Mark; Petit, Christine; Weil, Dominique

2002-04-01

Usher syndrome (USH) is an autosomal recessive disorder associated with sensorineural hearing impairment and progressive visual loss attributable to retinitis pigmentosa. This syndrome is both clinically and genetically heterogeneous. Three clinical types have been described of which type I (USH1) is the most severe. Six USH1 loci have been identified. We report a Palestinian consanguineous family from Jordan with three affected children. In view of the combination of profound hearing loss, vestibular dysfunction, and retinitis pigmentosa in the patients, we classified the disease as USH1. Linkage analysis excluded the involvement of any of the known USH1 loci. A genome-wide screening allowed us to map this novel locus, USH1G, in a 23-cM interval on chromosome 17q24-25. The USH1G interval overlaps the intervals for two dominant forms of isolated hearing loss, namely DFNA20 and DFNA26. Since several examples have been reported of syndromic and isolated forms of deafness being allelic, USH1G, DFNA20, and DFNA26 might result from alterations of the same gene. Finally, a mouse mutant, jackson shaker ( js), with deafness and circling behavior has been mapped to the murine homologous region on chromosome 11.

Chromosomally Integrated Human Herpesvirus 6: Models of Viral Genome Release from the Telomere and Impacts on Human Health.

PubMed

Wood, Michael L; Royle, Nicola J

2017-07-12

Human herpesvirus 6A and 6B, alongside some other herpesviruses, have the striking capacity to integrate into telomeres, the terminal repeated regions of chromosomes. The chromosomally integrated forms, ciHHV-6A and ciHHV-6B, are proposed to be a state of latency and it has been shown that they can both be inherited if integration occurs in the germ line. The first step in full viral reactivation must be the release of the integrated viral genome from the telomere and here we propose various models of this release involving transcription of the viral genome, replication fork collapse, and t-circle mediated release. In this review, we also discuss the relationship between ciHHV-6 and the telomere carrying the insertion, particularly how the presence and subsequent partial or complete release of the ciHHV-6 genome may affect telomere dynamics and the risk of disease.

Trisomy 13 as a primary chromosome aberration in acute leukemia.

PubMed

Mertens, F; Sallerfors, B; Heim, S; Johansson, B; Kristoffersson, U; Malm, C; Mitelman, F

1991-10-01

Four patients with acute leukemia displayed trisomy 13 as the primary chromosome abnormality. The two patients with acute nonlymphocytic leukemia FAB-type M1 (ANLL-M1) had the karyotypes 47,XY,+13/48,XY,+13,+13 and 47,XX,+13, a patient with the hypogranular form of ANLL M3 had 47,XX,+13, and the fourth patient, who had acute undifferentiated leukemia (AUL), had the karyotype 47,XY,+13/48,XY,+8,+13. Including these four cases, a total of 24 hematologic neoplasms with an extra chromosome 13 as the sole aberration have now been reported. Except for the AUL, all have been of myeloid origin--20 ANLL, one myelodysplastic syndrome, and two chronic myeloproliferative disorders. Trisomy 13 as the sole acquired karyotypic abnormality therefore seems to be strongly associated with myeloid differentiation of the neoplastic cells and with a differentiation block leading to acute leukemia.

A Human Tissue Culture Cell Line from a Transitional Cell Tumour of the Urinary Bladder: Growth, Chromosome Pattern and Ultrastructure

PubMed Central

Rigby, Carolyn C.; Franks, L. M.

1970-01-01

Cell cultures were made from 18 human bladder tumours. Three cell lines were maintained for seven transfer generations, but all had a “fibroblastic” morphology and a normal diploid karyotype. A fourth line has been maintained for over 80 transfer generations. This was derived from a well differentiated papillary tumour of bladder. Morphologically the light and electron microscopic structure of the cells resembled that of bladder tumours. The cells formed tumour nodules, with a similar structure, when transplanted into hamster cheek pouches. There is a stem line chromosome number of 48. Karyotypes of 60% of the stem line cells had one extra chromosome in Group C and one in Group D. ImagesFig. 11Figs. 12-15Fig. 16Fig. 17Figs. 1-4Fig. 18Figs. 5-8Figs. 9-10 PMID:5503601

A chromosomal investigation of some European Leiodidae (Coleoptera), with particular focus on Spanish subterranean Leptodirini

PubMed Central

Angus, Robert B.; Edwards, David B.; Luque, Carlos G.; Labrada, Lucia

2012-01-01

Abstract Karyotypes are shown for Leiodes calcarata (Erichson, 1845), Catops coracinus Kellner, 1846, Cantabrogeus luquei (Salgado, 1993), Espanoliella luquei Salgado & Fresneda, 2005, Fresnedaella lucius Salgado, Labrada & Luque, 2011, Notidocharis uhagoni (Sharp 1872), Quaestus (Quaesticulus) pasensis Salgado, Labrada & Luque, 2010, all of which are shown to have a diploid number of 20 autosomes plus Xy (♂) or XX (♀) sex chromosomes, as well as an as yet undescribed triploid species of the genus Cantabrogeus Salgado, 2000. These results are contrasted with published information, all on Leptodirini, which lists 10 species as having diploid numbers of 22 + Xy or XX. It is shown that the higher chromosome number (n = 11 + X or y) previously reported refers exclusively to the more derived Leptodirini (“infraflagellates”) whereas the lower number (n = 10 + X or y) refers to the less derived surface-dwelling forms and the less derived Leptodirini (“supraflagellates”). PMID:24260657

In search of intelligence: evolving a developmental neuron capable of learning

NASA Astrophysics Data System (ADS)

Khan, Gul Muhammad; Miller, Julian Francis

2014-10-01

A neuro-inspired multi-chromosomal genotype for a single developmental neuron capable of learning and developing memory is proposed. This genotype is evolved so that the phenotype which changes and develops during an agent's lifetime (while problem-solving) gives the agent the capacity for learning by experience. Seven important processes of signal processing and neural structure development are identified from biology and encoded using Cartesian Genetic Programming. These chromosomes represent the electrical and developmental aspects of dendrites, axonal branches, synapses and the neuron soma. The neural morphology that occurs by running these chromosomes is highly dynamic. The dendritic/axonal branches and synaptic connections form and change in response to situations encountered in the learning task. The approach has been evaluated in the context of maze-solving and the board game of checkers (draughts) demonstrating interesting learning capabilities. The motivation underlying this research is to, ab initio, evolve genotypes that build phenotypes with an ability to learn.

Shelterin Protects Chromosome Ends by Compacting Telomeric Chromatin

PubMed Central

Bandaria, Jigar N.; Qin, Peiwu; Berk, Veysel; Chu, Steven; Yildiz, Ahmet

2016-01-01

SUMMARY Telomeres, repetitive DNA sequences at chromosome ends, are shielded against the DNA damage response (DDR) by the shelterin complex. To understand how shelterin protects telomere ends, we investigated the structural organization of telomeric chromatin in human cells using super-resolution microscopy. We found that telomeres form compact globular structures through a complex network of interactions between shelterin subunits and telomeric DNA, and not by DNA methylation, histone deacetylation or histone trimethylation at telomeres and subtelomeric regions. Mutations that abrogate shelterin assembly or removal of individual subunits from telomeres cause up to a 10-fold increase in telomere volume. Decompacted telomeres become more accessible to telomere-associated proteins and accumulate DDR signals. Recompaction of telomeric chromatin using an orthogonal method displaces DDR signals from telomeres. These results reveal the chromatin remodeling activity of shelterin and demonstrate that shelterin-mediated compaction of telomeric chromatin provides robust protection of chromosome ends against the DDR machinery. PMID:26871633

Human structural variation: mechanisms of chromosome rearrangements

PubMed Central

Weckselblatt, Brooke; Rudd, M. Katharine

2015-01-01

Chromosome structural variation (SV) is a normal part of variation in the human genome, but some classes of SV can cause neurodevelopmental disorders. Analysis of the DNA sequence at SV breakpoints can reveal mutational mechanisms and risk factors for chromosome rearrangement. Large-scale SV breakpoint studies have become possible recently owing to advances in next-generation sequencing (NGS) including whole-genome sequencing (WGS). These findings have shed light on complex forms of SV such as triplications, inverted duplications, insertional translocations, and chromothripsis. Sequence-level breakpoint data resolve SV structure and determine how genes are disrupted, fused, and/or misregulated by breakpoints. Recent improvements in breakpoint sequencing have also revealed non-allelic homologous recombination (NAHR) between paralogous long interspersed nuclear element (LINE) or human endogenous retrovirus (HERV) repeats as a cause of deletions, duplications, and translocations. This review covers the genomic organization of simple and complex constitutional SVs, as well as the molecular mechanisms of their formation. PMID:26209074

Neurological abnormalities in the `cri-du-chat' syndrome 1

PubMed Central

Colover, Jack; Lucas, Mary; Comley, J. A.; Roe, A. M.

1972-01-01

An unusual case of the cri-du-chat syndrome is described in a 6½ year old boy, who, as well as attacks of stridor and choking, showed disorders of spatial perception and cerebellar signs in the form of nystagmus, clumsiness of the hands, and ataxia. Pyramidal signs were also present. He was only mildly retarded mentally. Psychological testing showed that he had a severe deficit for number processing, and also constructional apraxia. Surprisingly, his vocabulary was quite good, as was his reading capacity. Chromosome analysis showed a very small deletion of the short arm of the group B chromosome. In infancy this diagnosis may be suspected because of the high-pitched cry and attacks of stridor and choking. In late childhood, when the signs may be only of a neurological disorder, its recognition may be difficult without confirmation from chromosome studies. The neurological features of this disease are reviewed. Images PMID:5084140

Characteristics of a cell line established from a patient with multiple osteosarcoma, appearing 13 years after treatment for bilateral retinoblastoma.

PubMed

Fodstad, O; Brøgger, A; Bruland, O; Solheim, O P; Nesland, J M; Pihl, A

1986-07-15

An osteosarcoma cell line, OHS, was established from a patient with multiple skeletal manifestations of osteosarcoma, developing after bilateral retinoblastoma. The tumor cells expressed sarcoma-associated antigens and showed rapid growth in monolayers and as multicellular spheroids. They formed distinct colonies in soft agar, and subcutaneous tumors in nude mice. Morphological studies indicated that OHS cells had retained important characteristics of the cells of origin. No deletion of the retinoblastoma genes on chromosome 13q14 could be demonstrated with the banding techniques used. However, cytogenetic studies revealed double minute chromosomes, as evidence of gene amplification, as well as translocations involving chromosomes 1,6,11 and 13. The OHS line can be used to study the genetic basis of tumor initiation and growth, and to elucidate factors predisposing for second primary cancers in retinoblastoma patients.

Identifying sites of replication initiation in yeast chromosomes: looking for origins in all the right places.

PubMed

van Brabant, A J; Hunt, S Y; Fangman, W L; Brewer, B J

1998-06-01

DNA fragments that contain an active origin of replication generate bubble-shaped replication intermediates with diverging forks. We describe two methods that use two-dimensional (2-D) agarose gel electrophoresis along with DNA sequence information to identify replication origins in natural and artificial Saccharomyces cerevisiae chromosomes. The first method uses 2-D gels of overlapping DNA fragments to locate an active chromosomal replication origin within a region known to confer autonomous replication on a plasmid. A variant form of 2-D gels can be used to determine the direction of fork movement, and the second method uses this technique to find restriction fragments that are replicated by diverging forks, indicating that a bidirectional replication origin is located between the two fragments. Either of these two methods can be applied to the analysis of any genomic region for which there is DNA sequence information or an adequate restriction map.

The genetics of Alzheimer disease: current status and future prospects.

PubMed

Blacker, D; Tanzi, R E

1998-03-01

Four genes involved in the development of Alzheimer disease have been identified. Three fully penetrant (deterministic) genes lead to the development of Alzheimer disease in patients younger than 60 years: the amyloid beta-protein precursor on chromosome 21, presenilin 1 on chromosome 14, and presenilin 2 on chromosome 1. Together, they account for about half of this early-onset form of the disease. One genetic risk factor--apolipoprotein E-4--is associated with late-onset Alzheimer disease. It accounts for a substantial fraction of disease burden but seems to act primarily to lower the age of disease onset. In general, none of these genes can be easily adapted for use as a diagnostic or predictive test for Alzheimer disease. Research activity includes searching for additional genes, especially for late-onset disease, and elucidating the mechanism of action of all identified genes as part of a long-term effort to develop more effective therapeutic and preventive strategies.

Multi Groups Cooperation based Symbiotic Evolution for TSK-type Neuro-Fuzzy Systems Design

PubMed Central

Cheng, Yi-Chang; Hsu, Yung-Chi

2010-01-01

In this paper, a TSK-type neuro-fuzzy system with multi groups cooperation based symbiotic evolution method (TNFS-MGCSE) is proposed. The TNFS-MGCSE is developed from symbiotic evolution. The symbiotic evolution is different from traditional GAs (genetic algorithms) that each chromosome in symbiotic evolution represents a rule of fuzzy model. The MGCSE is different from the traditional symbiotic evolution; with a population in MGCSE is divided to several groups. Each group formed by a set of chromosomes represents a fuzzy rule and cooperate with other groups to generate the better chromosomes by using the proposed cooperation based crossover strategy (CCS). In this paper, the proposed TNFS-MGCSE is used to evaluate by numerical examples (Mackey-Glass chaotic time series and sunspot number forecasting). The performance of the TNFS-MGCSE achieves excellently with other existing models in the simulations. PMID:21709856

Bacterial cytoskeleton and implications for new antibiotic targets.

PubMed

Wang, Huan; Xie, Longxiang; Luo, Hongping; Xie, Jianping

2016-01-01

Traditionally eukaryotes exclusive cytoskeleton has been found in bacteria and other prokaryotes. FtsZ, MreB and CreS are bacterial counterpart of eukaryotic tubulin, actin filaments and intermediate filaments, respectively. FtsZ can assemble to a Z-ring at the cell division site, regulate bacterial cell division; MreB can form helical structure, and involve in maintaining cell shape, regulating chromosome segregation; CreS, found in Caulobacter crescentus (C. crescentus), can form curve or helical filaments in intracellular membrane. CreS is crucial for cell morphology maintenance. There are also some prokaryotic unique cytoskeleton components playing crucial roles in cell division, chromosome segregation and cell morphology. The cytoskeleton components of Mycobacterium tuberculosis (M. tuberculosis), together with their dynamics during exposure to antibiotics are summarized in this article to provide insights into the unique organization of this formidable pathogen and druggable targets for new antibiotics.

Massive introgression drives species radiation at the range limit of Anopheles gambiae.

PubMed

Vicente, José L; Clarkson, Christopher S; Caputo, Beniamino; Gomes, Bruno; Pombi, Marco; Sousa, Carla A; Antao, Tiago; Dinis, João; Bottà, Giordano; Mancini, Emiliano; Petrarca, Vincenzo; Mead, Daniel; Drury, Eleanor; Stalker, James; Miles, Alistair; Kwiatkowski, Dominic P; Donnelly, Martin J; Rodrigues, Amabélia; Torre, Alessandra Della; Weetman, David; Pinto, João

2017-04-18

Impacts of introgressive hybridisation may range from genomic erosion and species collapse to rapid adaptation and speciation but opportunities to study these dynamics are rare. We investigated the extent, causes and consequences of a hybrid zone between Anopheles coluzzii and Anopheles gambiae in Guinea-Bissau, where high hybridisation rates appear to be stable at least since the 1990s. Anopheles gambiae was genetically partitioned into inland and coastal subpopulations, separated by a central region dominated by A. coluzzii. Surprisingly, whole genome sequencing revealed that the coastal region harbours a hybrid form characterised by an A. gambiae-like sex chromosome and massive introgression of A. coluzzii autosomal alleles. Local selection on chromosomal inversions may play a role in this process, suggesting potential for spatiotemporal stability of the coastal hybrid form and providing resilience against introgression of medically-important loci and traits, found to be more prevalent in inland A. gambiae.

Massive introgression drives species radiation at the range limit of Anopheles gambiae

PubMed Central

Vicente, José L.; Clarkson, Christopher S.; Caputo, Beniamino; Gomes, Bruno; Pombi, Marco; Sousa, Carla A.; Antao, Tiago; Dinis, João; Bottà, Giordano; Mancini, Emiliano; Petrarca, Vincenzo; Mead, Daniel; Drury, Eleanor; Stalker, James; Miles, Alistair; Kwiatkowski, Dominic P.; Donnelly, Martin J.; Rodrigues, Amabélia; Torre, Alessandra della; Weetman, David; Pinto, João

2017-01-01

Impacts of introgressive hybridisation may range from genomic erosion and species collapse to rapid adaptation and speciation but opportunities to study these dynamics are rare. We investigated the extent, causes and consequences of a hybrid zone between Anopheles coluzzii and Anopheles gambiae in Guinea-Bissau, where high hybridisation rates appear to be stable at least since the 1990s. Anopheles gambiae was genetically partitioned into inland and coastal subpopulations, separated by a central region dominated by A. coluzzii. Surprisingly, whole genome sequencing revealed that the coastal region harbours a hybrid form characterised by an A. gambiae-like sex chromosome and massive introgression of A. coluzzii autosomal alleles. Local selection on chromosomal inversions may play a role in this process, suggesting potential for spatiotemporal stability of the coastal hybrid form and providing resilience against introgression of medically-important loci and traits, found to be more prevalent in inland A. gambiae. PMID:28417969

[No X-chromosome linked juvenile foveal retinoschisis].

PubMed

Pérez Alvarez, M J; Clement Fernández, F

2002-08-01

To describe the clinical characteristics of two cases of juvenile foveal retinoschisis in women with an atypical hereditary pattern, no X-chromosome linked. An autosomal recessive inheritance is proposed. Two generations of a family (5 members) in which only two sisters were evaluated. The complete examination of these two cases includes retinography, fluorescein angiography, automated perimetry, color vision testing, electroretinogram, electrooculogram and visually evoked potentials. Comparing our cases with the classic form of X-linked juvenile retinoschisis, they are less severely affected. The best visual acuity and the less disturbed or even normal electroretinogram confirm this fact. We emphasise the existence of isolated plaques of retinal pigment epithelium atrophy with perivascular pigment clumps without foveal schisis in one patient, which could represent an evolved form of this entity. The hereditary foveal juvenile retinoschisis in women suggests an autosomal inheritance (autosomal recessive in our cases) and presents less severe involvement (Arch Soc Esp Oftalmol 2002; 77: 443-448).

Changes of ploidy during the Azotobacter vinelandii growth cycle.

PubMed Central

Maldonado, R; Jiménez, J; Casadesús, J

1994-01-01

The size of the Azotobacter vinelandii chromosome is approximately 4,700 kb, as calculated by pulsed-field electrophoretic separation of fragments digested with the rarely cutting endonucleases SpeI and SwaI. Surveys of DNA content per cell by flow cytometry indicated the existence of ploidy changes during the A. vinelandii growth cycle in rich medium. Early-exponential-phase cells have a ploidy level similar to that of Escherichia coli or Salmonella typhimurium (probably ca. four chromosomes per cell), but a continuous increase of DNA content per cell is observed during growth. Late-exponential-phase cells may contain > 40 chromosomes per cell, while cells in the early stationary stage may contain > 80 chromosomes per cell. In late-stationary-phase cultures, the DNA content per cell is even higher, probably over 100 chromosome equivalents per cell. A dramatic change is observed in old stationary-phase cultures, when the population of highly polyploid bacteria segregates cells with low ploidy. The DNA content of the latter cells resembles that of cysts, suggesting that the process may reflect the onset of cyst differentiation. Cells with low ploidy are also formed when old stationary-phase cultures are diluted into fresh medium. Addition of rifampin to exponential-phase cultures causes a rapid increase in DNA content, indicating that A. vinelandii initiates multiple rounds of chromosome replication per cell division. Growth in minimal medium does not result in the spectacular changes of ploidy observed during rapid growth; this observation suggests that the polyploidy of A. vinelandii may not exist outside the laboratory. Images PMID:8021173

Caenorhabditis elegans polo-like kinase PLK-1 is required for merging parental genomes into a single nucleus.

PubMed

Rahman, Mohammad M; Munzig, Mandy; Kaneshiro, Kiyomi; Lee, Brandon; Strome, Susan; Müller-Reichert, Thomas; Cohen-Fix, Orna

2015-12-15

Before the first zygotic division, the nuclear envelopes of the maternal and paternal pronuclei disassemble, allowing both sets of chromosomes to be incorporated into a single nucleus in daughter cells after mitosis. We found that in Caenorhabditis elegans, partial inactivation of the polo-like kinase PLK-1 causes the formation of two nuclei, containing either the maternal or paternal chromosomes, in each daughter cell. These two nuclei gave rise to paired nuclei in all subsequent cell divisions. The paired-nuclei phenotype was caused by a defect in forming a gap in the nuclear envelopes at the interface between the two pronuclei during the first mitotic division. This was accompanied by defects in chromosome congression and alignment of the maternal and paternal metaphase plates relative to each other. Perturbing chromosome congression by other means also resulted in failure to disassemble the nuclear envelope between the two pronuclei. Our data further show that PLK-1 is needed for nuclear envelope breakdown during early embryogenesis. We propose that during the first zygotic division, PLK-1-dependent chromosome congression and metaphase plate alignment are necessary for the disassembly of the nuclear envelope between the two pronuclei, ultimately allowing intermingling of the maternal and paternal chromosomes. © 2015 Rahman et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

Genetic mapping of sex determination in a wild strawberry, Fragaria virginiana, reveals earliest form of sex chromosome.

PubMed

Spigler, R B; Lewers, K S; Main, D S; Ashman, T-L

2008-12-01

The evolution of separate sexes (dioecy) from hermaphroditism is one of the major evolutionary transitions in plants, and this transition can be accompanied by the development of sex chromosomes. Studies in species with intermediate sexual systems are providing unprecedented insight into the initial stages of sex chromosome evolution. Here, we describe the genetic mechanism of sex determination in the octoploid, subdioecious wild strawberry, Fragaria virginiana Mill., based on a whole-genome simple sequence repeat (SSR)-based genetic map and on mapping sex determination as two qualitative traits, male and female function. The resultant total map length is 2373 cM and includes 212 markers on 42 linkage groups (mean marker spacing: 14 cM). We estimated that approximately 70 and 90% of the total F. virginiana genetic map resides within 10 and 20 cM of a marker on this map, respectively. Both sex expression traits mapped to the same linkage group, separated by approximately 6 cM, along with two SSR markers. Together, our phenotypic and genetic mapping results support a model of gender determination in subdioecious F. virginiana with at least two linked loci (or gene regions) with major effects. Reconstruction of parental genotypes at these loci reveals that both female and hermaphrodite heterogamety exist in this species. Evidence of recombination between the sex-determining loci, an important hallmark of incipient sex chromosomes, suggest that F. virginiana is an example of the youngest sex chromosome in plants and thus a novel model system for the study of sex chromosome evolution.

The ultrastructure of mono- and holocentric plant centromeres: an immunological investigation by structured illumination microscopy and scanning electron microscopy.

PubMed

Wanner, Gerhard; Schroeder-Reiter, Elizabeth; Ma, Wei; Houben, Andreas; Schubert, Veit

2015-12-01

The spatial distribution of the three centromere-associated proteins α-tubulin, CENH3, and phosphorylated histone H2A (at threonine 120, H2AThr120ph) was analysed by indirect immunodetection at monocentric cereal chromosomes and at the holocentric chromosomes of Luzula elegans by super-resolution light microscopy and scanning electron microscopy (SEM). Using structured illumination microscopy (SIM) as the super-resolution technique on squashed specimens and SEM on uncoated isolated specimens, the three-dimensional (3D) distribution of the proteins was visualized at the centromeres. Technical aspects of 3D SEM are explained in detail. We show that CENH3 forms curved "pads" mainly around the lateral centromeric region in the primary constriction of metacentric chromosomes. H2AThr120ph is present in both the primary constriction and in the pericentromere. α-tubulin-labeled microtubule bundles attach to CENH3-containing chromatin structures, either in single bundles with a V-shaped attachment to the centromere or in split bundles to bordering pericentromeric flanks. In holocentric L. elegans chromosomes, H2AThr120ph is located predominantly in the centromeric groove of each chromatid as proven by subsequent FIB/FESEM ablation and 3D reconstruction. α-tubulin localizes to the edges of the groove. In both holocentric and monocentric chromosomes, no additional intermediate structures between microtubules and the centromere were observed. We established models of the distribution of CENH3, H2AThr120ph and the attachment sites of microtubules for metacentric and holocentric plant chromosomes.

Nasal Bone Shape Is under Complex Epistatic Genetic Control in Mouse Interspecific Recombinant Congenic Strains

PubMed Central

Burgio, Gaétan; Baylac, Michel; Heyer, Evelyne; Montagutelli, Xavier

2012-01-01

Background Genetic determinism of cranial morphology in the mouse is still largely unknown, despite the localization of putative QTLs and the identification of genes associated with Mendelian skull malformations. To approach the dissection of this multigenic control, we have used a set of interspecific recombinant congenic strains (IRCS) produced between C57BL/6 and mice of the distant species Mus spretus (SEG/Pas). Each strain has inherited 1.3% of its genome from SEG/Pas under the form of few, small-sized, chromosomal segments. Results The shape of the nasal bone was studied using outline analysis combined with Fourier descriptors, and differential features were identified between IRCS BcG-66H and C57BL/6. An F2 cross between BcG-66H and C57BL/6 revealed that, out of the three SEG/Pas-derived chromosomal regions present in BcG-66H, two were involved. Segments on chromosomes 1 (∼32 Mb) and 18 (∼13 Mb) showed additive effect on nasal bone shape. The three chromosomal regions present in BcG-66H were isolated in congenic strains to study their individual effect. Epistatic interactions were assessed in bicongenic strains. Conclusions Our results show that, besides a strong individual effect, the QTL on chromosome 1 interacts with genes on chromosomes 13 and 18. This study demonstrates that nasal bone shape is under complex genetic control but can be efficiently dissected in the mouse using appropriate genetic tools and shape descriptors. PMID:22662199

Identification of DSB-1, a Protein Required for Initiation of Meiotic Recombination in Caenorhabditis elegans, Illuminates a Crossover Assurance Checkpoint

PubMed Central

Stamper, Ericca L.; Rodenbusch, Stacia E.; Rosu, Simona; Ahringer, Julie; Villeneuve, Anne M.; Dernburg, Abby F.

2013-01-01

Meiotic recombination, an essential aspect of sexual reproduction, is initiated by programmed DNA double-strand breaks (DSBs). DSBs are catalyzed by the widely-conserved Spo11 enzyme; however, the activity of Spo11 is regulated by additional factors that are poorly conserved through evolution. To expand our understanding of meiotic regulation, we have characterized a novel gene, dsb-1, that is specifically required for meiotic DSB formation in the nematode Caenorhabditis elegans. DSB-1 localizes to chromosomes during early meiotic prophase, coincident with the timing of DSB formation. DSB-1 also promotes normal protein levels and chromosome localization of DSB-2, a paralogous protein that plays a related role in initiating recombination. Mutations that disrupt crossover formation result in prolonged DSB-1 association with chromosomes, suggesting that nuclei may remain in a DSB-permissive state. Extended DSB-1 localization is seen even in mutants with defects in early recombination steps, including spo-11, suggesting that the absence of crossover precursors triggers the extension. Strikingly, failure to form a crossover precursor on a single chromosome pair is sufficient to extend the localization of DSB-1 on all chromosomes in the same nucleus. Based on these observations we propose a model for crossover assurance that acts through DSB-1 to maintain a DSB-permissive state until all chromosome pairs acquire crossover precursors. This work identifies a novel component of the DSB machinery in C. elegans, and sheds light on an important pathway that regulates DSB formation for crossover assurance. PMID:23990794

Genomic evidence for role of inversion 3RP of Drosophila melanogaster in facilitating climate change adaptation.

PubMed

Rane, Rahul V; Rako, Lea; Kapun, Martin; Lee, Siu F; Hoffmann, Ary A

2015-05-01

Chromosomal inversion polymorphisms are common in animals and plants, and recent models suggest that alternative arrangements spread by capturing different combinations of alleles acting additively or epistatically to favour local adaptation. It is also thought that inversions typically maintain favoured combinations for a long time by suppressing recombination between alternative chromosomal arrangements. Here, we consider patterns of linkage disequilibrium and genetic divergence in an old inversion polymorphism in Drosophila melanogaster (In(3R)Payne) known to be associated with climate change adaptation and a recent invasion event into Australia. We extracted, karyotyped and sequenced whole chromosomes from two Australian populations, so that changes in the arrangement of the alleles between geographically separated tropical and temperate areas could be compared. Chromosome-wide linkage disequilibrium (LD) analysis revealed strong LD within the region spanned by In(3R)Payne. This genomic region also showed strong differentiation between the tropical and the temperate populations, but no differentiation between different karyotypes from the same population, after controlling for chromosomal arrangement. Patterns of differentiation across the chromosome arm and in gene ontologies were enhanced by the presence of the inversion. These data support the notion that inversions are strongly selected by bringing together combinations of genes, but it is still not clear if such combinations act additively or epistatically. Our data suggest that climatic adaptation through inversions can be dynamic, reflecting changes in the relative abundance of different forms of an inversion and ongoing evolution of allelic content within an inversion. © 2015 John Wiley & Sons Ltd.

Cytogenetic mapping of the Muller F element genes in Drosophila willistoni group.

PubMed

Pita, Sebastián; Panzera, Yanina; Lúcia da Silva Valente, Vera; de Melo, Zilpa das Graças Silva; Garcia, Carolina; Garcia, Ana Cristina Lauer; Montes, Martín Alejandro; Rohde, Claudia

2014-10-01

Comparative genomics in Drosophila began in 1940, when Muller stated that the ancestral haploid karyotype of this genus is constituted by five acrocentric chromosomes and one dot chromosome, named A to F elements. In some species of the willistoni group such as Drosophila willistoni and D. insularis, the F element, instead of a dot chromosome, has been incorporated into the E element, forming chromosome III (E + F fusion). The aim of this study was to investigate the scope of the E + F fusion in the willistoni group, evaluating six other species. Fluorescent in situ hybridization was used to locate two genes of the F element previously studied-cubitus interruptus (ci) and eyeless (ey)-in species of the willistoni and bocainensis subgroups. Moreover, polytene chromosome photomaps corresponding to the F element (basal portion of chromosome III) were constructed for each species studied. In D. willistoni, D. paulistorum and D. equinoxialis, the ci gene was located in subSectction 78B and the ey gene in 78C. In D. tropicalis, ci was located in subSection 76B and ey in 76C. In species of the bocainensis subgroup, ci and ey were localized, respectively, at subsections 76B and 76C in D. nebulosa and D. capricorni, and 76A and 76C in D. fumipennis. Despite the differences in the subsection numbers, all species showed the same position for ci and ey. The results confirm the synteny of E + F fusion in willistoni and bocainensis subgroups, and allow estimating the occurrence of this event at 15 Mya, at least.

Circularity and self-cleavage as a strategy for the emergence of a chromosome in the RNA-based protocell

PubMed Central

2013-01-01

Background It is now popularly accepted that an “RNA world” existed in early evolution. During division of RNA-based protocells, random distribution of individual genes (simultaneously as ribozymes) between offspring might have resulted in gene loss, especially when the number of gene types increased. Therefore, the emergence of a chromosome carrying linked genes was critical for the prosperity of the RNA world. However, there were quite a few immediate difficulties for this event to occur. For example, a chromosome would be much longer than individual genes, and thus more likely to degrade and less likely to replicate completely; the copying of the chromosome might start at middle sites and be only partial; and, without a complex transcription mechanism, the synthesis of distinct ribozymes would become problematic. Results Inspired by features of viroids, which have been suggested as “living fossils” of the RNA world, we supposed that these difficulties could have been overcome if the chromosome adopted a circular form and small, self-cleaving ribozymes (e.g. the hammer head ribozymes) resided at the sites between genes. Computer simulation using a Monte-Carlo method was conducted to investigate this hypothesis. The simulation shows that an RNA chromosome can spread (increase in quantity and be sustained) in the system if it is a circular one and its linear “transcripts” are readily broken at the sites between genes; the chromosome works as genetic material and ribozymes “coded” by it serve as functional molecules; and both circularity and self-cleavage are important for the spread of the chromosome. Conclusions In the RNA world, circularity and self-cleavage may have been adopted as a strategy to overcome the immediate difficulties for the emergence of a chromosome (with linked genes). The strategy suggested here is very simple and likely to have been used in this early stage of evolution. By demonstrating the possibility of the emergence of an RNA chromosome, this study opens on the prospect of a prosperous RNA world, populated by RNA-based protocells with a number of genes, showing complicated functions. Reviewers This article was reviewed by Sergei Kazakov (nominated by Laura Landweber), Nobuto Takeuchi (nominated by Anthony Poole), and Eugene Koonin. PMID:23971788

Construction of physical maps for the sex-specific regions of papaya sex chromosomes.

PubMed

Na, Jong-Kuk; Wang, Jianping; Murray, Jan E; Gschwend, Andrea R; Zhang, Wenli; Yu, Qingyi; Navajas-Pérez, Rafael; Feltus, F Alex; Chen, Cuixia; Kubat, Zdenek; Moore, Paul H; Jiang, Jiming; Paterson, Andrew H; Ming, Ray

2012-05-08

Papaya is a major fruit crop in tropical and subtropical regions worldwide. It is trioecious with three sex forms: male, female, and hermaphrodite. Sex determination is controlled by a pair of nascent sex chromosomes with two slightly different Y chromosomes, Y for male and Yh for hermaphrodite. The sex chromosome genotypes are XY (male), XYh (hermaphrodite), and XX (female). The papaya hermaphrodite-specific Yh chromosome region (HSY) is pericentromeric and heterochromatic. Physical mapping of HSY and its X counterpart is essential for sequencing these regions and uncovering the early events of sex chromosome evolution and to identify the sex determination genes for crop improvement. A reiterate chromosome walking strategy was applied to construct the two physical maps with three bacterial artificial chromosome (BAC) libraries. The HSY physical map consists of 68 overlapped BACs on the minimum tiling path, and covers all four HSY-specific Knobs. One gap remained in the region of Knob 1, the only knob structure shared between HSY and X, due to the lack of HSY-specific sequences. This gap was filled on the physical map of the HSY corresponding region in the X chromosome. The X physical map consists of 44 BACs on the minimum tiling path with one gap remaining in the middle, due to the nature of highly repetitive sequences. This gap was filled on the HSY physical map. The borders of the non-recombining HSY were defined genetically by fine mapping using 1460 F2 individuals. The genetically defined HSY spanned approximately 8.5 Mb, whereas its X counterpart extended about 5.4 Mb including a 900 Kb region containing the Knob 1 shared by the HSY and X. The 8.5 Mb HSY corresponds to 4.5 Mb of its X counterpart, showing 4 Mb (89%) DNA sequence expansion. The 89% increase of DNA sequence in HSY indicates rapid expansion of the Yh chromosome after genetic recombination was suppressed 2-3 million years ago. The genetically defined borders coincide with the common BACs on the minimum tiling paths of HSY and X. The minimum tiling paths of HSY and its X counterpart are being used for sequencing these X and Yh-specific regions.

Rare congenital chromosomal aberration dic(X;Y)(p22.33;p11.32) in a patient with primary myelofibrosis.

PubMed

Pavlistova, Lenka; Izakova, Silvia; Zemanova, Zuzana; Bartuskova, Lucie; Langova, Martina; Malikova, Pavlina; Michalova, Kyra

2016-01-01

Constitutional translocations between sex chromosomes are rather rare in humans with breakpoints at Xp11 and Yq11 as the most frequent. Breakpoints on the short arm of the Y chromosome form one subgroup of t(X;Y), giving rise to a derived chromosome with the centromeres of both the X and Y chromosomes, dic(X;Y). Here, we report a rare congenital chromosomal aberration, 46,X,dic(X;Y)(p22.33;p11.32)[20]/45,X[10], in an adult male. Primary myelofibrosis, a malignant haematological disease, was diagnosed in a 63-year-old man following liver transplantation after hepatocellular carcinoma. By the analysis of the bone marrow sample, the karyotype 46,X,dic(X;Y)(p22.33;p11.32) was detected in all the mitoses analysed and verified with multicolour fluorescence in situ hybridization (mFISH). A cytogenetic examination of stimulated peripheral blood cells revealed the constitutional karyotype 46,X,dic(X;Y)(p22.33;p11.32)[20]/45,X[10]. The cell line 45,X was confirmed with FISH in 35 % of interphase nuclei. The SRY locus was present on the dicentric chromosome. A CGH/SNP array (Illumina) revealed a gain of 153,7 Mbp of the X chromosome and a 803-kbp microdeletion (including the SHOX gene), which were also confirmed with FISH. SHOX encodes a transcriptional factor that regulates the growth of the long bones. The deletion of the SHOX gene together with the Madelung deformity of the forearm and the short stature of the proband led to a diagnosis of Léri-Weill dyschondrosteosis (LWD). The gain of almost the whole X chromosome (153,7 Mbp) was considered a variant of Klinefelter syndrome (KS). The levels of gonadotropins and testosterone were consistent with gonadal dysfunction. A malformation of the right external ear was detected. We have reported a structural aberration of the sex chromosomes, dic(X;Y)(p22.33;p11.32). The related genomic imbalance is associated with two known hereditary syndromes, LWD and a KS variant, identified in our proband at an advanced age. Because the breakpoints did not involve cancer genes, we inferred that the two malignancies in the proband were not caused by this abnormality. The possible influence of SHOX haploinsufficiency on the growth regulation of auricular chondrocytes is discussed.

Mechanisms of ring chromosome formation, ring instability and clinical consequences.

PubMed

Guilherme, Roberta S; Meloni, Vera F Ayres; Kim, Chong A; Pellegrino, Renata; Takeno, Sylvia S; Spinner, Nancy B; Conlin, Laura K; Christofolini, Denise M; Kulikowski, Leslie D; Melaragno, Maria I

2011-12-21

The breakpoints and mechanisms of ring chromosome formation were studied and mapped in 14 patients. Several techniques were performed such as genome-wide array, MLPA (Multiplex Ligation-Dependent Probe Amplification) and FISH (Fluorescent in situ Hybridization). The ring chromosomes of patients I to XIV were determined to be, respectively: r(3)(p26.1q29), r(4)(p16.3q35.2), r(10)(p15.3q26.2), r(10)(p15.3q26.13), r(13)(p13q31.1), r(13)(p13q34), r(14)(p13q32.33), r(15)(p13q26.2), r(18)(p11.32q22.2), r(18)(p11.32q21.33), r(18)(p11.21q23), r(22)(p13q13.33), r(22)(p13q13.2), and r(22)(p13q13.2). These rings were found to have been formed by different mechanisms, such as: breaks in both chromosome arms followed by end-to-end reunion (patients IV, VIII, IX, XI, XIII and XIV); a break in one chromosome arm followed by fusion with the subtelomeric region of the other (patients I and II); a break in one chromosome arm followed by fusion with the opposite telomeric region (patients III and X); fusion of two subtelomeric regions (patient VII); and telomere-telomere fusion (patient XII). Thus, the r(14) and one r(22) can be considered complete rings, since there was no loss of relevant genetic material. Two patients (V and VI) with r(13) showed duplication along with terminal deletion of 13q, one of them proved to be inverted, a mechanism known as inv-dup-del. Ring instability was detected by ring loss and secondary aberrations in all but three patients, who presented stable ring chromosomes (II, XIII and XIV). We concluded that the clinical phenotype of patients with ring chromosomes may be related with different factors, including gene haploinsufficiency, gene duplications and ring instability. Epigenetic factors due to the circular architecture of ring chromosomes must also be considered, since even complete ring chromosomes can result in phenotypic alterations, as observed in our patients with complete r(14) and r(22).

Genetic, chromosomal, and syndromic causes of neural tube defects.

PubMed

Seidahmed, Mohammed Z; Abdelbasit, Omer B; Shaheed, Meeralebbae M; Alhussein, Khalid A; Miqdad, Abeer M; Samadi, Abdulmohsen S; Khalil, Mohammed I; Al-Mardawi, Elham; Salih, Mustafa A

2014-12-01

To ascertain the incidence, and describe the various forms of neural tube defects (NTDs) due to genetic, chromosomal, and syndromic causes. We carried out a retrospective analysis of data retrieved from the medical records of newborn infants admitted to the Neonatal Intensive Care Unit with NTDs and their mothers spanning 14 years (1996-2009) at the Security Forces Hospital, Riyadh, Saudi Arabia. The cases were ascertained by a perinatologist, neonatologist, geneticist, radiologist, and neurologist. The literature was reviewed via a MEDLINE search. Only liveborn babies were included. Permission from the Educational Committee at the Security Forces Hospital was obtained prior to the collection of data. Out of 103 infants with NTDs admitted during this period, 20 (19.4%) were found to have an underlying genetic syndromic, chromosomal and/or other anomalies. There were 5 cases of Meckel-Gruber syndrome, 2 Joubert syndrome, one Waardenburg syndrome, one Walker-Warburg syndrome, 2 chromosomal disorders, 2 caudal regression, one amniotic band disruption sequence, one associated with omphalocele, one with diaphragmatic hernia, and 4 with multiple congenital anomalies. There is a high rate of underlying genetic syndromic and/or chromosomal causes of NTDs in the Saudi Arabian population due to the high consanguinity rate. Identification of such association can lead to more accurate provisions of genetic counseling to the family including preimplantation genetic diagnosis or early termination of pregnancies associated with lethal conditions.