Induction of chromosome aberrations in human cells by charged particles

NASA Technical Reports Server (NTRS)

Wu, H.; Durante, M.; George, K.; Yang, T. C.

1997-01-01

Chromosome aberrations induced by high-energy charged particles in normal human lymphocytes and human fibroblasts have been investigated. The charged particles included 250 MeV/nucleon protons, 290 MeV/nucleon carbon ions and 1 GeV/nucleon iron ions. The energies of the charged particles were higher than in most of the studies reported in the literature. Lymphocytes were stimulated to grow immediately after irradiation, while fibroblasts were incubated at 37 degrees C for 24 h for repair. Chromosomes were collected at the first mitosis after irradiation and chromosome aberrations were scored using the fluorescence in situ hybridization (FISH) technique with a whole-chromosome 4 probe. Chromosome aberrations were classified as reciprocal exchanges, incomplete exchanges, deletions and complex exchanges. The relative biological effectiveness (RBE) for each type of aberration was calculated by dividing a dose of 4 Gy by the dose of the charged particles producing the same effect as 4 Gy of gamma rays. Results of this study showed that complex aberrations have the highest RBE for radiation of high linear energy transfer (LET) for human lymphocytes, but for fibroblasts, the greatest effect was for incomplete exchanges. For both lymphocytes and fibroblasts, iron ions induced a similar fraction of aberrant cells.

Painting Analysis of Chromosome Aberrations Induced by Energetic Heavy Ions in Human Cells

NASA Technical Reports Server (NTRS)

Wu, Honglu

2006-01-01

FISH, mFISH, mBAND, telomere and centromere probes have been used to study chromosome aberrations induced in human cells exposed to low-and high-LET radiation in vitro. High-LET induced damages are mostly a single track effect. Unrejoined chromosome breaks (incomplete exchanges) and complex type aberrations were higher for high-LET. Biosignatures may depend on the method the samples are collected. Recent mBAND analysis has revealed more information about the nature of intra-chromosome exchanges. Whether space flight/microgravity affects radiation-induced chromosome aberration frequencies is still an open question.

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.

Estimate of the frequency of true incomplete exchanges in human lymphocytes exposed to 1 GeV/u Fe ions in vitro

NASA Technical Reports Server (NTRS)

Wu, H.; George, K.; Yang, T. C.

1999-01-01

PURPOSE: To study the frequency of true incomplete exchanges induced by high-LET radiation. MATERIALS AND METHODS: Human lymphocytes were exposed to 1 GeV/u Fe ions (LET = 140 keV/microm). Chromosome aberrations were analysed by a fluorescence in situ hybridization using a combination of whole-chromosome-specific probes and human telomere probes. Chromosomes 1, 3 and 4 were investigated. RESULTS: The percentage of incomplete exchanges was between 23 and 29% if telomere signals were not considered. The percentage decreased to approximately 10% after ruling out false incomplete exchanges containing telomere signals. The final estimation of true incomplete exchanges was <10%. CONCLUSION: Within a degree of uncertainty, the percentage of true incomplete exchanges in 1 GeV/u Fe ion-irradiated human lymphocytes was similar to that induced by gamma rays.

DNA Repair Defects and Chromosomal Aberrations

NASA Technical Reports Server (NTRS)

Hada, Megumi; George, K. A.; Huff, J. L.; Pluth, J. M.; Cucinotta, F. A.

2009-01-01

Yields of chromosome aberrations were assessed in cells deficient in DNA doublestrand break (DSB) repair, after exposure to acute or to low-dose-rate (0.018 Gy/hr) gamma rays or acute high LET iron nuclei. We studied several cell lines including fibroblasts deficient in ATM (ataxia telangiectasia mutated; product of the gene that is mutated in ataxia telangiectasia patients) or NBS (nibrin; product of the gene mutated in the Nijmegen breakage syndrome), and gliomablastoma cells that are proficient or lacking in DNA-dependent protein kinase (DNA-PK) activity. Chromosomes were analyzed using the fluorescence in situ hybridization (FISH) chromosome painting method in cells at the first division post irradiation, and chromosome aberrations were identified as either simple exchanges (translocations and dicentrics) or complex exchanges (involving >2 breaks in 2 or more chromosomes). Gamma irradiation induced greater yields of both simple and complex exchanges in the DSB repair-defective cells than in the normal cells. The quadratic dose-response terms for both simple and complex chromosome exchanges were significantly higher for the ATM- and NBS-deficient lines than for normal fibroblasts. However, in the NBS cells the linear dose-response term was significantly higher only for simple exchanges. The large increases in the quadratic dose-response terms in these repair-defective cell lines points the importance of the functions of ATM and NBS in chromatin modifications to facilitate correct DSB repair and minimize the formation of aberrations. The differences found between ATM- and NBS-deficient cells at low doses suggest that important questions should with regard to applying observations of radiation sensitivity at high dose to low-dose exposures. For aberrations induced by iron nuclei, regression models preferred purely linear dose responses for simple exchanges and quadratic dose responses for complex exchanges. Relative biological effectiveness (RBE) factors of all of the DNA repair-defective cell lines were smaller than those of normal cells, with the DNA-PK-deficient cells having RBEs near unity. To further investigate the sensitivity differences that were observed in ATM and NBS deficient cells, chromosomal aberrations were analyzed in normal lung fibroblast cells treated with KU-55933 (a specific ATM kinase inhibitor) or Mirin (an Mre11- Rad50-Nbs1 complex inhibitor involved in activation of ATM). We also performed siRNA knockdown of these proteins. Preliminary data indicate that chromosome exchanges increase in cells treated with the specific ATM inhibitor. Possible cytogenetic signatures of acute and low dose-rate gamma irradiation in ATM or nibrin deficient and suppressed cells will be discussed.

Effect of borax on immune cell proliferation and sister chromatid exchange in human chromosomes

PubMed Central

Pongsavee, Malinee

2009-01-01

Background Borax is used as a food additive. It becomes toxic when accumulated in the body. It causes vomiting, fatigue and renal failure. Methods The heparinized blood samples from 40 healthy men were studied for the impact of borax toxicity on immune cell proliferation (lymphocyte proliferation) and sister chromatid exchange in human chromosomes. The MTT assay and Sister Chromatid Exchange (SCE) technic were used in this experiment with the borax concentrations of 0.1, 0.15, 0.2, 0.3 and 0.6 mg/ml. Results It showed that the immune cell proliferation (lymphocyte proliferation) was decreased when the concentrations of borax increased. The borax concentration of 0.6 mg/ml had the most effectiveness to the lymphocyte proliferation and had the highest cytotoxicity index (CI). The borax concentrations of 0.15, 0.2, 0.3 and 0.6 mg/ml significantly induced sister chromatid exchange in human chromosomes (P < 0.05). Conclusion Borax had effects on immune cell proliferation (lymphocyte proliferation) and induced sister chromatid exchange in human chromosomes. Toxicity of borax may lead to cellular toxicity and genetic defect in human. PMID:19878537

Complex chromosomal rearrangements induced in vivo by heavy ions.

PubMed

Durante, M; Ando, K; Furusawa, Y; Obe, G; George, K; Cucinotta, F A

2004-01-01

It has been suggested that the ratio complex/simple exchanges can be used as a biomarker of exposure to high-LET radiation. We tested this hypothesis in vivo, by considering data from several studies that measured complex exchanges in peripheral blood from humans exposed to mixed fields of low- and high-LET radiation. In particular, we studied data from astronauts involved in long-term missions in low-Earth-orbit, and uterus cancer patients treated with accelerated carbon ions. Data from two studies of chromosomal aberrations in astronauts used blood samples obtained before and after space flight, and a third study used blood samples from patients before and after radiotherapy course. Similar methods were used in each study, where lymphocytes were stimulated to grow in vitro, and collected after incubation in either colcemid or calyculin A. Slides were painted with whole-chromosome DNA fluorescent probes (FISH), and complex and simple chromosome exchanges in the painted genome were classified separately. Complex-type exchanges were observed at low frequencies in control subjects, and in our test subjects before the treatment. No statistically significant increase in the yield of complex-type exchanges was induced by the space flight. Radiation therapy induced a high fraction of complex exchanges, but no significant differences could be detected between patients treated with accelerated carbon ions or X-rays. Complex chromosomal rearrangements do not represent a practical biomarker of radiation quality in our test subjects. Copyright 2003 S. Karger AG, Basel

Complex Chromosomal Rearrangements Induced in Vivo by Heavy Ions

NASA Technical Reports Server (NTRS)

Durante, M.; Ando, K.; Furusawa, G.; Obe, G.; George, K.; Cucinotta, F. A.

2004-01-01

It has been suggested that the ratio complex/simple exchanges can be used as a biomarker of exposure to high-LET radiation. We tested this hypothesis in vivo, by considering data from several studies that measured complex exchanges in peripheral blood from humans exposed to mixed fields of low- and high-LET radiation. In particular, we studied data from astronauts involved in long-term missions in low-Earth-orbit, and uterus cancer patients treated with accelerated carbon ions. Data from two studies of chromosomal aberrations in astronauts used blood samples obtained before and after space flight, and a third study used blood samples from patients before and after radiotherapy course. Similar methods were used in each study, where lymphocytes were stimulated to grow in vitro, and collected after incubation in either colcemid or calyculin A. Slides were painted with whole-chromosome DNA fluorescent probes (FISH), and complex and simple chromosome exchanges in the painted genome were classified separately. Complex-type exchanges were observed at low frequencies in control subjects, and in our test subjects before the treatment. No statistically significant increase in the yield of complex-type exchanges was induced by the space flight. Radiation therapy induced a high fraction of complex exchanges, but no significant differences could be detected between patients treated with accelerated carbon ions or X-rays. Complex chromosomal rearrangements do not represent a practical biomarker of radiation quality in our test subjects. Copyright 2003 S. Karger AG, Basel.

The effect of track structure on the induction of chromosomal aberrations in murine cells

NASA Technical Reports Server (NTRS)

Durante, M.; Cella, L.; Furusawa, Y.; George, K.; Gialanella, G.; Grossi, G.; Pugliese, M.; Saito, M.; Yang, T. C.

1998-01-01

PURPOSE: To measure chromosome aberrations in C3H 10T1/2 mouse fibroblasts using FISH painting at the first mitosis following exposure to 30 keV/microm hydrogen or neon ions. MATERIALS AND METHODS: Cells in plateau-phase were irradiated with 0.86 MeV protons at the TTT-3 Tandem accelerator in Naples (Italy), or with 400 MeV/n Ne ions at the HIMAC accelerator in Chiba (Japan). Colcemid-blocked cells were harvested at the first mitosis following exposure, and chromosome spreads were hybridized in situ with a fluorescein-labelled composite mouse DNA probe specific for chromosomes 2 and 8. RESULTS: Protons were more efficient than neon ions at the same LET in the induction of chromosome interchanges and breaks. Yields of complex exchanges were similar for both particles at the same dose, but protons produced mostly insertions, while with Ne exposure non-reciprocal exchanges were the most frequent complex-type exchange. CONCLUSIONS: Charged particles with the same LET produce different yields of chromosome aberrations, and some observed differences can be explained based on the available track-structure models.

The effect of track structure on the induction of chromosomal aberrations in murine cells.

PubMed

Durante, M; Cella, L; Furusawa, Y; George, K; Gialanella, G; Grossi, G; Pugliese, M; Saito, M; Yang, T C

1998-03-01

To measure chromosome aberrations in C3H 10T1/2 mouse fibroblasts using FISH painting at the first mitosis following exposure to 30 keV/microm hydrogen or neon ions. Cells in plateau-phase were irradiated with 0.86 MeV protons at the TTT-3 Tandem accelerator in Naples (Italy), or with 400 MeV/n Ne ions at the HIMAC accelerator in Chiba (Japan). Colcemid-blocked cells were harvested at the first mitosis following exposure, and chromosome spreads were hybridized in situ with a fluorescein-labelled composite mouse DNA probe specific for chromosomes 2 and 8. Protons were more efficient than neon ions at the same LET in the induction of chromosome interchanges and breaks. Yields of complex exchanges were similar for both particles at the same dose, but protons produced mostly insertions, while with Ne exposure non-reciprocal exchanges were the most frequent complex-type exchange. Charged particles with the same LET produce different yields of chromosome aberrations, and some observed differences can be explained based on the available track-structure models.

Relationships between chromosome structure and chromosomal aberrations

NASA Astrophysics Data System (ADS)

Eidelman, Yuri; Andreev, Sergey

An interphase nucleus of human lymphocyte was simulated by the novel Monte Carlo tech-nique. The main features of interphase chromosome structure and packaging were taken into account: different levels of chromatin organisation; nonrandom localisation of chromosomes within a nucleus; chromosome loci dynamics. All chromosomes in a nucleus were modelled as polymer globules. A dynamic pattern of intra/interchromosomal contacts was simulated. The detailed information about chromosomal contacts, such as distribution of intrachromoso-mal contacts over the length of each chromosome and dependence of contact probability on genomic separation between chromosome loci, were calculated and compared to the new exper-imental data obtained by the Hi-C technique. Types and frequencies of simple and complex radiation-induced chromosomal exchange aberrations (CA) induced by X-rays were predicted with taking formation and decay of chromosomal contacts into account. Distance dependence of exchange formation probability was calculated directly. mFISH data for human lymphocytes were analysed. The calculated frequencies of simple CA agreed with the experimental data. Complex CA were underestimated despite the dense packaging of chromosome territories within a nucleus. Possible influence of chromosome-nucleus structural organisation on the frequency and spectrum of radiation-induced chromosome aberrations is discussed.

Persistence of space radiation induced cytogenetic damage in the blood lymphocytes of astronauts.

PubMed

George, K; Chappell, L J; Cucinotta, F A

2010-08-14

Cytogenetic damage was assessed in blood lymphocytes from 16 astronauts before and after they participated in long-duration space missions of 3 months or more. The frequency of chromosome damage was measured by fluorescence in situ hybridization (FISH) chromosome painting before flight and at various intervals from a few days to many months after return from the mission. For all individuals, the frequency of chromosome exchanges measured within a month of return from space was higher than their preflight yield. However, some individuals showed a temporal decline in chromosome damage with time after flight. Statistical analysis using combined data for all astronauts indicated a significant overall decreasing trend in total chromosome exchanges with time after flight, although this trend was not seen for all astronauts and the yield of chromosome damage in some individuals actually increased with time after flight. The decreasing trend in total exchanges was slightly more significant when statistical analysis was restricted to data collected more than 220 days after return from flight. When analysis was restricted to data collected within 220 days of return from the mission there was no relationship between total exchanges and time. Translocation yields varied more between astronauts and there was only a slight non-significant decrease with time after flight that was similar for both later and earlier sampling times. Copyright (c) 2010. Published by Elsevier B.V.

[Comparative analysis of cytogenetic examination of control groups of subjects carried out in different Russian laboratories].

PubMed

Sevan'kaev, A V; Khvostunov, I K; Snigireva, G P; Novitskaia, N N; Antoshchina, M M; Fesenko, E V; Vorobtsova, I E; Neronova, E G; Domracheva, E V; Nugis, V Iu; Govorun, R D; Handogina, E K

2013-01-01

The incidence of unstable chromosome aberrations in peripheral blood lymphocytes from unirradiated control subjects was analyzed using cytogenetic data obtained from 9 cytogenetic laboratories located in Moscow, St.-Petersburg, Obninsk, and Dubna (Russia). The objective of this study was to estimate the level and spectrum of spontaneous chromosome aberrations in human lymphocytes. 1140 blood samples were taken from 1112 subjects (594 men and 546 women) aged 1 to 72. The total metaphase number was 466795. The uniform Giemsa method for peripheral blood lymphocyte cultures was used. After counting 466795 metaphases, 4288 chromosomal aberrations of various types were classified. The most frequent types of aberrations were acentrics and chromatid deletions. They made up 90% of the total number of aberrations. The remaining 10% were exchange aberrations. The number of chromosome exchanges (dicentrics and centric rings) was twice the number of chromatid exchanges. Overall, the portion ofcells with chromosomal or (and) chromatid aberrations was 0.89 +/- 0.01%; the frequency of acentrics was 0.29 +/- 0.01; the frequency of dicentrics was 0.046 +/- 0.003; the frequency of unstable chromosome aberrations was 0.35 +/- 0.01; and the frequency of chromatid aberrations was 0.57 +/- 0.01 per 100 cells.

Chromosomal Aberrations in DNA Repair Defective Cell Lines: Comparisons of Dose Rate and Radiation Quality

NASA Technical Reports Server (NTRS)

George, K. A.; Hada, M.; Patel, Z.; Huff, J.; Pluth, J. M.; Cucinotta, F. A.

2009-01-01

Chromosome aberration yields were assessed in DNA double-strand break repair (DSB) deficient cells after acute doses of gamma-rays or high-LET iron nuclei, or low dose-rate (0.018 Gy/hr) gamma-rays. We studied several cell lines including fibroblasts deficient in ATM (product of the gene that is mutated in ataxia telangiectasia patients) or NBS (product of the gene mutated in the Nijmegen breakage syndrome), and gliomablastoma cells that are proficient or lacking in DNA-dependent protein kinase, DNA-PK activity. Chromosomes were analyzed using the fluorescence in-situ hybridization (FISH) chromosome painting method in cells at the first division post-irradiation and chromosome aberrations were identified as either simple exchanges (translocations and dicentrics) or complex exchanges (involving >2 breaks in 2 or more chromosomes). Gamma radiation induced higher yields of both simple and complex exchanges in the DSB repair defective cells than in the normal cells. The quadratic dose-response terms for both chromosome exchange types were significantly higher for the ATM and NBS defective lines than for normal fibroblasts. However, the linear dose-response term was significantly higher only for simple exchanges in the NBS cells. Large increases in the quadratic dose response terms indicate the important roles of ATM and NBS in chromatin modifications that facilitate correct DSB repair and minimize aberration formation. Differences in the response of AT and NBS deficient cells at lower doses suggests important questions about the applicability of observations of radiation sensitivity at high dose to low dose exposures. For all iron nuclei irradiated cells, regression models preferred purely linear and quadratic dose responses for simple and complex exchanges, respectively. All the DNA repair defective cell lines had lower Relative biological effectiveness (RBE) values than normal cells, the lowest being for the DNA-PK-deficient cells, which was near unity. To further investigate the sensitivity differences for low and low high doses, we performed chronic low dose-rate irradiation, and have begun studies with ATM and Nibrin inhibitors and siRNA knockout of these proteins. Results support the conclusion that for the endpoint of simple chromosomal aberrations (translocation or dicentrics), the increased radiation sensitivity of AT cells found at high doses (>1 Gy) does not carry over to low doses or doserates, while NBS cells show increased sensitivity for both high and low dose exposures.

Frequency of sister chromatid exchange and chromosomal aberrations in asbestos cement workers.

PubMed

Fatma, N; Jain, A K; Rahman, Q

1991-02-01

Exposure to asbestos minerals has been associated with a wide variety of adverse health effects including lung cancer, pleural mesothelioma, and cancer of other organs. It was shown previously that asbestos samples collected from a local asbestos factory enhanced sister chromatid exchanges (SCEs) and chromosomal aberrations in vitro using human lymphocytes. In the present study, 22 workers from the same factory and 12 controls were further investigated. Controls were matched for age, sex, and socioeconomic state. The peripheral blood lymphocytes were cultured and harvested at 48 hours for studies of chromosomal aberrations and at 72 hours for SCE frequency determinations. Asbestos workers had a raised mean SCE rate and increased numbers of chromosomal aberrations compared with a control population. Most of the chromosomal aberrations were chromatid gap and break types.

[Mechanistic modelling allows to assess pathways of DNA lesion interactions underlying chromosome aberration formation].

PubMed

Eĭdel'man, Iu A; Slanina, S V; Sal'nikov, I V; Andreev, S G

2012-12-01

The knowledge of radiation-induced chromosomal aberration (CA) mechanisms is required in many fields of radiation genetics, radiation biology, biodosimetry, etc. However, these mechanisms are yet to be quantitatively characterised. One of the reasons is that the relationships between primary lesions of DNA/chromatin/chromosomes and dose-response curves for CA are unknown because the pathways of lesion interactions in an interphase nucleus are currently inaccessible for direct experimental observation. This article aims for the comparative analysis of two principally different scenarios of formation of simple and complex interchromosomal exchange aberrations: by lesion interactions at chromosome territories' surface vs. in the whole space of the nucleus. The analysis was based on quantitative mechanistic modelling of different levels of structures and processes involved in CA formation: chromosome structure in an interphase nucleus, induction, repair and interactions of DNA lesions. It was shown that the restricted diffusion of chromosomal loci, predicted by computational modelling of chromosome organization, results in lesion interactions in the whole space of the nucleus being impossible. At the same time, predicted features of subchromosomal dynamics agrees well with in vivo observations and does not contradict the mechanism of CA formation at the surface of chromosome territories. On the other hand, the "surface mechanism" of CA formation, despite having certain qualities, proved to be insufficient to explain high frequency of complex exchange aberrations observed by mFISH technique. The alternative mechanism, CA formation on nuclear centres is expected to be sufficient to explain frequent complex exchanges.

Chromosomal Translocations: Chicken or Egg? | Center for Cancer Research

Cancer.gov

Many tumor cells have abnormal chromosomes. Some of these abnormalities are caused by chromosomal translocations, which occur when two chromosomes break and incorrectly rejoin, resulting in an exchange of genetic material. Translocations can activate oncogenes, silence tumor suppressor genes, or result in the creation of completely new fusion gene products. While there is

Influence of dose rate on the induction of simple and complex chromosome exchanges by gamma rays.

PubMed

Loucas, Bradford D; Eberle, Richard; Bailey, Susan M; Cornforth, Michael N

2004-10-01

Single-color painting of whole chromosomes, or protocols in which only a few chromosomes are distinctively painted, will always fail to detect a proportion of complex exchanges because they frequently produce pseudosimple painting patterns that are indistinguishable from those produced by bona fide simple exchanges. When 24-color multi-fluor FISH (mFISH) was employed for the purpose of distinguishing (truly) simple from pseudosimple exchanges, it was confirmed that the acute low-LET radiation dose-response relationship for simple exchanges lacked significant upward curvature. This result has been interpreted to indicate that the formation of simple exchanges requires only one chromosome locus be damaged (e.g. broken) by radiation to initiate an exchange-not two, as classical cytogenetic theory maintains. Because a one-lesion mechanism implies single-track action, it follows that the production of simple exchanges should not be influenced by changes in dose rate. To examine this prediction, we irradiated noncycling primary human fibroblasts with graded doses of (137)Cs gamma rays at an acute dose rate of 1.10 Gy/min and compared, using mFISH, the yield of simple exchanges to that observed after exposure to the same radiation delivered at a chronic dose rate of 0.08 cGy/min. The shape of the dose response was found to be quasi-linear for both dose rates, but, counter to providing support for a one-lesion mechanism, the yield of simple aberrations was greatly reduced by protracted exposure. Although chronic doses were delivered at rates low enough to produce damage exclusively by single-track action, this did not altogether eliminate the formation of complex aberrations, an analysis of which leads to the conclusion that a single track of low-LET radiation is capable of inducing complex exchanges requiring up to four proximate breaks for their formation. For acute exposures, the ratio of simple reciprocal translocations to simple dicentrics was near unity.

Chromatin Structure and Radiation-Induced Intrachromosome Exchange

NASA Technical Reports Server (NTRS)

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

2011-01-01

We have recently investigated the location of breaks involved in intrachromosomal type exchange events, using the multicolor banding in situ hybridization (mBAND) technique for human chromosome 3. In human epithelial cells exposed to both low- and high-LET radiations in vitro, intrachromosome exchanges were found to occur preferentially between a break in the 3p21 and one in the 3q11. Exchanges were also observed between a break in 3p21 and one in 3q26, but few exchanges were observed between breaks in 3q11 and 3q26, even though the two regions were on the same arm of the chromosome. To explore the relationships between intrachromosome exchanges and chromatin structure, we used probes that hybridize the three regions of 3p21, 3q11 and 3q26, and measured the distance between two of the three regions in interphase cells. We further analyzed fragile sites on the chromosome that have been identified in various types of cancers. Our results demonstrated that the distribution of breaks involved in radiation-induced intrachromosome aberrations depends upon both the location of fragile sites and the folding of chromatins

mBAND analysis of chromosome aberrations in lymphocytes exposed in vitro to alpha-particles and gamma-rays.

PubMed

Tawn, E Janet; Janet, E; Whitehouse, Caroline A; Holdsworth, Duncan; De Ruyck, Kim; Vandenbulcke, Katia; Thierens, Hubert

2008-06-01

To investigate the profiles of chromosome damage induced in vitro by exposure to alpha-particles and gamma-rays. Human peripheral blood lymphocytes were exposed to three dose regimes: alpha-particle doses of 0.2 and 0.5 Gy and a gamma-ray dose of 1.5 Gy. After culturing for 47 hours, chromosome aberrations involving the number 5 chromosomes were identified using a multi-coloured banding (mBAND) technique. Analysis of the frequencies of chromosome 5 breaks within aberrant cells and within aberrant number 5 chromosomes demonstrated that alpha-particle irradiation is more likely to result in multiple breaks in a chromosome than gamma-irradiation. Additionally, overdispersion was observed for all doses for the distribution of breaks amongst all cells analysed and breaks amongst total number 5 chromosomes, with this being greatest for the 0.2 Gy alpha-particle dose. The ratio of interchanges to intrachanges (F ratio) was 1.4 and 2.4 for 0.2 and 0.5 Gy alpha-particles respectively and 5.5 for 1.5 Gy gamma-rays. Evaluation of simple versus complex exchanges indicated ratios of 1.9 and 2.7 for 0.2 and 0.5 Gy alpha-particles respectively and 10.6 for 1.5 Gy gamma-rays. The majority of the intrachanges involving chromosomes 5 induced by alpha-particle radiation were associated with more complex exchanges. This study has confirmed that exchanges induced by exposure to high linear energy transfer (LET) alpha-particle radiation comprise a greater proportion of intrachanges than those induced by exposure to low LET gamma-rays. However, since the majority of these are associated with complex rearrangements and likely to be non-transmissible, this limits their applicability as a marker of past in vivo exposure.

Rejoining and misrejoining of radiation-induced chromatin breaks. III. Hypertonic treatment

NASA Technical Reports Server (NTRS)

Durante, M.; George, K.; Wu, H. L.; Yang, T. C.

1998-01-01

It has been shown that treatment in anisotonic medium modifies rejoining of radiation-induced breaks in interphase chromosomes. In previous work, we have demonstrated that formation of exchanges in human lymphocytes has a slow component (half-time of 1-2 h), but a fraction of exchanges are also observed in samples assayed soon after exposure. In this paper we studied the effect of hypertonic treatment on rejoining and misrejoining of radiation-induced breaks using fluorescence in situ hybridization of prematurely condensed chromosomes in human lymphocytes. Isolated lymphocytes were irradiated with 7 Gy gamma rays, fused to mitotic hamster cells and incubated in hypertonic solution (0.5 M NaCl) for the period normally allowed for interphase chromosome condensation to occur. The data from hypertonic treatment experiments indicate the presence of a class of interphase chromosome breaks that rejoin and misrejoin very quickly (half-time of 5-6 min). The fast misrejoining of these lesions is considered to be responsible for the initial level of exchanges which we reported previously. No significant effect of hypertonic treatment on the yield of chromosome aberrations scored at the first postirradiation mitosis was detected.

The Biological Effectiveness of Accelerated Particles for the Induction of Chromosome Damage: Track Structure Effects and Cytogenetic Signatures of High-LET Exposure

NASA Technical Reports Server (NTRS)

George, K.; Hada, M.; Chappell, L.; Cucinotta, F. A.

2012-01-01

Track structure models predict that at a fixed value of LET, particles with lower charge number, Z will have a higher biological effectiveness compared to particles with a higher Z. In this report we investigated how track structure effects induction of chromosomal aberration in human cells. Human lymphocytes were irradiated in vitro with various energies of accelerated iron, silicon, neon, or titanium ions and chromosome damage was assessed in using three color FISH chromosome painting in chemically induced PCC samples collected a first cell division post irradiation. The LET values for these ions ranged from 30 to 195 keV/micrometers. Of the particles studied, Neon ions have the highest biological effectiveness for induction of total chromosome damage, which is consistent with track structure model predictions. For complex-type exchanges 64 MeV/ u Neon and 450 MeV/u Iron were equally effective and induced the most complex damage. In addition we present data on chromosomes exchanges induced by six different energies of protons (5 MeV/u to 2.5 GeV/u). The linear dose response term was similar for all energies of protons suggesting that the effect of the higher LET at low proton energies is balanced by the production of nuclear secondaries from the high energy protons. All energies of protons have a much higher percentage of complex-type chromosome exchanges than gamma rays, signifying a cytogenetic signature for proton exposures.

Kinetics of DSB rejoining and formation of simple chromosome exchange aberrations

NASA Technical Reports Server (NTRS)

Cucinotta, F. A.; Nikjoo, H.; O'Neill, P.; Goodhead, D. T.

2000-01-01

PURPOSE: To investigate the role of kinetics in the processing of DNA double strand breaks (DSB), and the formation of simple chromosome exchange aberrations following X-ray exposures to mammalian cells based on an enzymatic approach. METHODS: Using computer simulations based on a biochemical approach, rate-equations that describe the processing of DSB through the formation of a DNA-enzyme complex were formulated. A second model that allows for competition between two processing pathways was also formulated. The formation of simple exchange aberrations was modelled as misrepair during the recombination of single DSB with undamaged DNA. Non-linear coupled differential equations corresponding to biochemical pathways were solved numerically by fitting to experimental data. RESULTS: When mediated by a DSB repair enzyme complex, the processing of single DSB showed a complex behaviour that gives the appearance of fast and slow components of rejoining. This is due to the time-delay caused by the action time of enzymes in biomolecular reactions. It is shown that the kinetic- and dose-responses of simple chromosome exchange aberrations are well described by a recombination model of DSB interacting with undamaged DNA when aberration formation increases with linear dose-dependence. Competition between two or more recombination processes is shown to lead to the formation of simple exchange aberrations with a dose-dependence similar to that of a linear quadratic model. CONCLUSIONS: Using a minimal number of assumptions, the kinetics and dose response observed experimentally for DSB rejoining and the formation of simple chromosome exchange aberrations are shown to be consistent with kinetic models based on enzymatic reaction approaches. A non-linear dose response for simple exchange aberrations is possible in a model of recombination of DNA containing a DSB with undamaged DNA when two or more pathways compete for DSB repair.

Space Radiation Induced Cytogenetic Damage in the Blood Lymphocytes of Astronauts: Persistence of Damage After Flight and the Effects of Repeat Long Duration Missions

NASA Technical Reports Server (NTRS)

George, Kerry; Rhone, Jordan; Chappell, L. J.; Cucinotta, F. A.

2010-01-01

Cytogenetic damage was assessed in blood lymphocytes from astronauts before and after they participated in long-duration space missions of three months or more. The frequency of chromosome damage was measured by fluorescence in situ hybridization (FISH) chromosome painting before flight and at various intervals from a few days to many months after return from the mission. For all individuals, the frequency of chromosome exchanges measured within a month of return from space was higher than their prefight yield. However, some individuals showed a temporal decline in chromosome damage with time after flight. Statistical analysis using combined data for all astronauts indicated a significant overall decreasing trend in total chromosome exchanges with time after flight, although this trend was not seen for all astronauts and the yield of chromosome damage in some individuals actually increased with time after flight. The decreasing trend in total exchanges was slightly more significant when statistical analysis was restricted to data collected more than 220 days after return from flight. In addition, limited data on multiple flights show a lack of correlation between time in space and translocation yields. Data from three crewmembers who has participated in two separate long-duration space missions provide limited information on the effect of repeat flights and show a possible adaptive response to space radiation exposure.

Chromosome aberrations in the blood lymphocytes of astronauts after space flight

NASA Technical Reports Server (NTRS)

George, K.; Durante, M.; Wu, H.; Willingham, V.; Badhwar, G.; Cucinotta, F. A.

2001-01-01

Cytogenetic analysis of the lymphocytes of astronauts provides a direct measurement of space radiation damage in vivo, which takes into account individual radiosensitivity and considers the influence of microgravity and other stress conditions. Chromosome exchanges were measured in the blood lymphocytes of eight crew members after their respective space missions, using fluorescence in situ hybridization (FISH) with chromosome painting probes. Significant increases in aberrations were observed after the long-duration missions. The in vivo dose was derived from the frequencies of translocations and total exchanges using calibration curves determined before flight, and the RBE was estimated by comparison with individually measured physical absorbed doses. The values for average RBE were compared to the average quality factor (Q) from direct measurements of the lineal energy spectra using a tissue-equivalent proportional counter (TEPC) and radiation transport codes. The ratio of aberrations identified as complex was slightly higher after flight, which is thought to be an indication of exposure to high-LET radiation. To determine whether the frequency of complex aberrations measured in metaphase spreads after exposure to high-LET radiation was influenced by a cell cycle delay, chromosome damage was analyzed in prematurely condensed chromosome samples collected from two crew members before and after a short-duration mission. The frequency of complex exchanges after flight was higher in prematurely condensed chromosomes than in metaphase cells for one crew member.

Chromosome aberrations in the blood lymphocytes of astronauts after space flight.

PubMed

George, K; Durante, M; Wu, H; Willingham, V; Badhwar, G; Cucinotta, F A

2001-12-01

Cytogenetic analysis of the lymphocytes of astronauts provides a direct measurement of space radiation damage in vivo, which takes into account individual radiosensitivity and considers the influence of microgravity and other stress conditions. Chromosome exchanges were measured in the blood lymphocytes of eight crew members after their respective space missions, using fluorescence in situ hybridization (FISH) with chromosome painting probes. Significant increases in aberrations were observed after the long-duration missions. The in vivo dose was derived from the frequencies of translocations and total exchanges using calibration curves determined before flight, and the RBE was estimated by comparison with individually measured physical absorbed doses. The values for average RBE were compared to the average quality factor (Q) from direct measurements of the lineal energy spectra using a tissue-equivalent proportional counter (TEPC) and radiation transport codes. The ratio of aberrations identified as complex was slightly higher after flight, which is thought to be an indication of exposure to high-LET radiation. To determine whether the frequency of complex aberrations measured in metaphase spreads after exposure to high-LET radiation was influenced by a cell cycle delay, chromosome damage was analyzed in prematurely condensed chromosome samples collected from two crew members before and after a short-duration mission. The frequency of complex exchanges after flight was higher in prematurely condensed chromosomes than in metaphase cells for one crew member.

High-LET Radiation Induced Chromosome Aberrations in Normal and Ataxia Telangiectasia Fibroblast Cells

NASA Astrophysics Data System (ADS)

Kawata, Tetsuya; George, Ms Kerry; Cucinotta, Francis A.; Shigematsu, Naoyuki; Ito, Hisao; Furusawa, Yoshiya; Uno, Takashi

We investigated the effects of heavy ions beams on chromosomal aberrations in normal and AT cells. Normal and AT fibroblast cells arrested at G0/G1 phase were irradiated with 2 Gy of X-rays, 490 MeV/u Silicon (LET 55 keV/micron), 500 MeV/u Iron (LET 185 keV/micron) and 200 MeV/u Iron (LET 440 keV/micron) particles, and then cells were allowed to repair for 24 hours at 37 degrees before subculture. Calyculin-A induced PCC method was employed to collect G2/M chromosomes and whole DNA probes 1 and 3 were used to analyze chromosomal aberrations such as color-junctions, deletions, simple exchanges (incomplete and reciprocal exchanges) and complex-type exchanges. The percentages of aberrant cells were higher when normal and AT cells were exposed to heavy ions compared to X-rays, and had a tendency to increase with increasing LET up to 185 keV/micron and then decreased at 440 keV/micron. When the frequency of color-junctions per cell was compared after X-ray exposure, AT cells had around three times higher frequency of color-junctions (mis-rejoining) than normal cells. However, at 185 keV/micron there was no difference in the frequency of color-junctions between two cell lines. It was also found that the frequency of simple exchanges per cell was almost constant in AT cells regardless LET levels, but it was LET dependent for normal cells. Interestingly, the frequency of simple exchanges was higher for normal fibroblast cells when it was compared at 185 keV/micron, but AT cells had more complex-type exchanges at the same LET levels. Heavy ions are more efficient in inducing chromosome aberrations in normal and AT cells compared to X-rays, and the aberration types between normal and AT fibroblast appeared different probably due to difference in the ATM gene function.

Recurrent sequence exchange between homeologous grass chromosomes.

PubMed

Wicker, Thomas; Wing, Rod A; Schubert, Ingo

2015-11-01

All grass species evolved from an ancestor that underwent a whole-genome duplication (WGD) approximately 70 million years ago. Interestingly, the short arms of rice chromosomes 11 and 12 (and independently their homologs in sorghum) were found to be much more similar to each other than other homeologous regions within the duplicated genome. Based on detailed analysis of rice chromosomes 11 and 12 and their homologs in seven grass species, we propose a mechanism that explains the apparently 'younger' age of the duplication in this region of the genome, assuming a small number of reciprocal translocations at the chromosome termini. In each case the translocations were followed by unbalanced transmission and subsequent lineage sorting of the involved chromosomes to offspring. Molecular dating of these translocation events also allowed us to date major chromosome 'fusions' in the evolutionary lineages that led to Brachypodium and Triticeae. Furthermore, we provide evidence that rice is exceptional regarding the evolution of chromosomes 11 and 12, inasmuch as in other species the process of sequence exchange between homeologous chromosomes ceased much earlier than in rice. We presume that random events rather than selective forces are responsible for the observed high similarity between the short arm ends of rice chromosomes 11 and 12. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

Increased incidence of chromosomal aberrations in peripheral lymphocytes of retired nickel workers.

PubMed

Waksvik, H; Boysen, M; Høgetveit, A C

1984-11-01

Chromosomal aberrations and sister chromatid exchanges were analysed in the peripheral lymphocytes of nine retired nickel refinery workers 4-15 years after the retirement and compared with 11 matched non-nickel exposed controls. None of the controls had previous occupations with known relation to induction of chromosomal aberrations nor sister chromatid exchanges. The groups were equal as to socioeconomic status and environmental factors other than the occupational ones, which could influence the chromosome parameters, were to the largest possible extent excluded. The nickel workers' previous occupational employment involved exposure to inhalation of furnace dust of Ni3S2 and NiO or aerosols of NiCl2 and NiSO4. The concentration of nickel in the working atmospheres has been higher than 1.0 mg/m3 air and the exposure time more than 25 years. The retired nickel workers showed an increased incidence of breaks (p less than 0.001) and gaps (p less than 0.05) but no difference in the incidence of sister chromatid exchanges when compared with the controls.

How-to-Do-It: Demonstrating Sister Chromatid Exchanges.

ERIC Educational Resources Information Center

Dye, Frank J.

1988-01-01

Outlines procedures for demonstrating and preparing a permanent slide of sister chromatid exchanges and recombination events between the two chromatids of a single chromosome. Provides the name of an additional resource for making preparations of exchanges. (RT)

Three-Color Chromosome Painting as Seen through the Eyes of mFISH: Another Look at Radiation-Induced Exchanges and Their Conversion to Whole-Genome Equivalency

PubMed Central

Loucas, Bradford D.; Shuryak, Igor; Cornforth, Michael N.

2016-01-01

Whole-chromosome painting (WCP) typically involves the fluorescent staining of a small number of chromosomes. Consequently, it is capable of detecting only a fraction of exchanges that occur among the full complement of chromosomes in a genome. Mathematical corrections are commonly applied to WCP data in order to extrapolate the frequency of exchanges occurring in the entire genome [whole-genome equivalency (WGE)]. However, the reliability of WCP to WGE extrapolations depends on underlying assumptions whose conditions are seldom met in actual experimental situations, in particular the presumed absence of complex exchanges. Using multi-fluor fluorescence in situ hybridization (mFISH), we analyzed the induction of simple exchanges produced by graded doses of 137Cs gamma rays (0–4 Gy), and also 1.1 GeV 56Fe ions (0–1.5 Gy). In order to represent cytogenetic damage as it would have appeared to the observer following standard three-color WCP, all mFISH information pertaining to exchanges that did not specifically involve chromosomes 1, 2, or 4 was ignored. This allowed us to reconstruct dose–responses for three-color apparently simple (AS) exchanges. Using extrapolation methods similar to those derived elsewhere, these were expressed in terms of WGE for comparison to mFISH data. Based on AS events, the extrapolated frequencies systematically overestimated those actually observed by mFISH. For gamma rays, these errors were practically independent of dose. When constrained to a relatively narrow range of doses, the WGE corrections applied to both 56Fe and gamma rays predicted genome-equivalent damage with a level of accuracy likely sufficient for most applications. However, the apparent accuracy associated with WCP to WGE corrections is both fortuitous and misleading. This is because (in normal practice) such corrections can only be applied to AS exchanges, which are known to include complex aberrations in the form of pseudosimple exchanges. When WCP to WGE corrections are applied to true simple exchanges, the results are less than satisfactory, leading to extrapolated values that underestimate the true WGE response by unacceptably large margins. Likely explanations for these results are discussed, as well as their implications for radiation protection. Thus, in seeming contradiction to notion that complex aberrations be avoided altogether in WGE corrections – and in violation of assumptions upon which these corrections are based – their inadvertent inclusion in three-color WCP data is actually required in order for them to yield even marginally acceptable results. PMID:27014627

A highly efficient targeted recombination system for engineering linear chromosomes of industrial bacteria Streptomyces.

PubMed

Pan, Hung-Yin; Chen, Carton W; Huang, Chih-Hung

2018-04-17

Soil bacteria Streptomyces are the most important producers of secondary metabolites, including most known antibiotics. These bacteria and their close relatives are unique in possessing linear chromosomes, which typically harbor 20 to 30 biosynthetic gene clusters of tens to hundreds of kb in length. Many Streptomyces chromosomes are accompanied by linear plasmids with sizes ranging from several to several hundred kb. The large linear plasmids also often contain biosynthetic gene clusters. We have developed a targeted recombination procedure for arm exchanges between a linear plasmid and a linear chromosome. A chromosomal segment inserted in an artificially constructed plasmid allows homologous recombination between the two replicons at the homology. Depending on the design, the recombination may result in two recombinant replicons or a single recombinant chromosome with the loss of the recombinant plasmid that lacks a replication origin. The efficiency of such targeted recombination ranges from 9 to 83% depending on the locations of the homology (and thus the size of the chromosomal arm exchanged), essentially eliminating the necessity of selection. The targeted recombination is useful for the efficient engineering of the Streptomyces genome for large-scale deletion, addition, and shuffling.

Biodosimetry of heavy ions by interphase chromosome painting

NASA Astrophysics Data System (ADS)

Durante, M.; Kawata, T.; Nakano, T.; Yamada, S.; Tsujii, H.

1998-11-01

We report measurements of chromosomal aberrations in peripheral blood lymphocytes from cancer patients undergoing radiotherapy treatment. Patients with cervix or esophageal cancer were treated with 10 MV X-rays produced at a LINAC accelerator, or high-energy carbon ions produced at the HIMAC accelerator at the National Institute for Radiological Sciences (NIRS) in Chiba. Blood samples were obtained before, during, and after the radiation treatment. Chromosomes were prematurely condensed by incubation in calyculin A. Aberrations in chromosomes 2 and 4 were scored after fluorescence in situ hybridization with whole-chromosome probes. Pre-treatment samples were exposed in vitro to X-rays, individual dose-response curves for the induction of chromosomal aberrations were determined, and used as calibration curves to calculate the effective whole-body dose absorbed during the treatment. This calculated dose, based on the calibration curve relative to the induction of reciprocal exchanges, has a sharp increase after the first few fractions of the treatment, then saturates at high doses. Although carbon ions are 2-3 times more effective than X-rays in tumor sterilization, the effective dose was similar to that of X-ray treatment. However, the frequency of complex-type chromosomal exchanges was much higher for patients treated with carbon ions than X-ray.

Molecular Marker Systems for Oenothera Genetics

PubMed Central

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

2008-01-01

The genus Oenothera has an outstanding scientific tradition. It has been a model for studying aspects of chromosome evolution and speciation, including the impact of plastid nuclear co-evolution. A large collection of strains analyzed during a century of experimental work and unique genetic possibilities allow the exchange of genetically definable plastids, individual or multiple chromosomes, and/or entire haploid genomes (Renner complexes) between species. However, molecular genetic approaches for the genus are largely lacking. In this study, we describe the development of efficient PCR-based marker systems for both the nuclear genome and the plastome. They allow distinguishing individual chromosomes, Renner complexes, plastomes, and subplastomes. We demonstrate their application by monitoring interspecific exchanges of genomes, chromosome pairs, and/or plastids during crossing programs, e.g., to produce plastome–genome incompatible hybrids. Using an appropriate partial permanent translocation heterozygous hybrid, linkage group 7 of the molecular map could be assigned to chromosome 9·8 of the classical Oenothera map. Finally, we provide the first direct molecular evidence that homologous recombination and free segregation of chromosomes in permanent translocation heterozygous strains is suppressed. PMID:18791241

Molecular marker systems for Oenothera genetics.

PubMed

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

2008-11-01

The genus Oenothera has an outstanding scientific tradition. It has been a model for studying aspects of chromosome evolution and speciation, including the impact of plastid nuclear co-evolution. A large collection of strains analyzed during a century of experimental work and unique genetic possibilities allow the exchange of genetically definable plastids, individual or multiple chromosomes, and/or entire haploid genomes (Renner complexes) between species. However, molecular genetic approaches for the genus are largely lacking. In this study, we describe the development of efficient PCR-based marker systems for both the nuclear genome and the plastome. They allow distinguishing individual chromosomes, Renner complexes, plastomes, and subplastomes. We demonstrate their application by monitoring interspecific exchanges of genomes, chromosome pairs, and/or plastids during crossing programs, e.g., to produce plastome-genome incompatible hybrids. Using an appropriate partial permanent translocation heterozygous hybrid, linkage group 7 of the molecular map could be assigned to chromosome 9.8 of the classical Oenothera map. Finally, we provide the first direct molecular evidence that homologous recombination and free segregation of chromosomes in permanent translocation heterozygous strains is suppressed.

Dose Response for Chromosome Aberrations in Human Lymphocytes and Fibroblasts after Exposure to Very Low Doses of High LET Radiation

NASA Technical Reports Server (NTRS)

Hada, M.; George, Kerry; Cucinotta, Francis A.

2011-01-01

The relationship between biological effects and low doses of absorbed radiation is still uncertain, especially for high LET radiation exposure. Estimates of risks from low-dose and low-dose-rates are often extrapolated using data from Japanese atomic bomb survivors with either linear or linear quadratic models of fit. In this study, chromosome aberrations were measured in human peripheral blood lymphocytes and normal skin fibroblasts cells after exposure to very low dose (1-20 cGy) of 170 MeV/u Si-28- ions or 600 MeV/u Fe-56-ions. Chromosomes were analyzed using the whole chromosome fluorescence in situ hybridization (FISH) technique during the first cell division after irradiation, and chromosome aberrations were identified as either simple exchanges (translocations and dicentrics) or complex exchanges (involving greater than 2 breaks in 2 or more chromosomes). The curves for doses above 10 cGy were fitted with linear or linear-quadratic functions. For Si-28- ions no dose response was observed in the 2-10 cGy dose range, suggesting a non-target effect in this range.

Chromosome mutations and chromosome stability in children treated with different regimes of immunosuppressive drugs.

PubMed

Schuler, D; Dobos, M; Fekete, G; Miltényi, M; Kalmár, L

1979-01-01

The chromosome mutations and the number of sister chromatid exchanges induced by different kinds of immunosuppressive treatment were investigated in children and adults with certain types of renal diseases. The aim of the study was to find among the treatment schedules those promising good therapeutic results with the least mutagenic effects. A slightly decreased chromosome stability was found in the patients treated by cyclophosphamide therapy.

A compartmentalized signaling network mediates crossover control in meiosis

PubMed Central

Zhang, Liangyu; Köhler, Simone; Rillo-Bohn, Regina

2018-01-01

During meiosis, each pair of homologous chromosomes typically undergoes at least one crossover (crossover assurance), but these exchanges are strictly limited in number and widely spaced along chromosomes (crossover interference). The molecular basis for this chromosome-wide regulation remains mysterious. A family of meiotic RING finger proteins has been implicated in crossover regulation across eukaryotes. Caenorhabditis elegans expresses four such proteins, of which one (ZHP-3) is known to be required for crossovers. Here we investigate the functions of ZHP-1, ZHP-2, and ZHP-4. We find that all four ZHP proteins, like their homologs in other species, localize to the synaptonemal complex, an unusual, liquid crystalline compartment that assembles between paired homologs. Together they promote accumulation of pro-crossover factors, including ZHP-3 and ZHP-4, at a single recombination intermediate, thereby patterning exchanges along paired chromosomes. These proteins also act at the top of a hierarchical, symmetry-breaking process that enables crossovers to direct accurate chromosome segregation. PMID:29521627

Precision-engineering the Pseudomonas aeruginosa genome with two-step allelic exchange

PubMed Central

Hmelo, Laura R.; Borlee, Bradley R.; Almblad, Henrik; Love, Michelle E.; Randall, Trevor E.; Tseng, Boo Shan; Lin, Chuyang; Irie, Yasuhiko; Storek, Kelly M.; Yang, Jaeun Jane; Siehnel, Richard J.; Howell, P. Lynne; Singh, Pradeep K.; Tolker-Nielsen, Tim; Parsek, Matthew R.; Schweizer, Herbert P.; Harrison, Joe J.

2016-01-01

Allelic exchange is an efficient method of bacterial genome engineering. This protocol describes the use of this technique to make gene knockouts and knockins, as well as single nucleotide insertions, deletions and substitutions in Pseudomonas aeruginosa. Unlike other approaches to allelic exchange, this protocol does not require heterologous recombinases to insert or excise selective markers from the target chromosome. Rather, positive and negative selection are enabled solely by suicide vector-encoded functions and host cell proteins. Here, mutant alleles, which are flanked by regions of homology to the recipient chromosome, are synthesized in vitro and then cloned into allelic exchange vectors using standard procedures. These suicide vectors are then introduced into recipient cells by conjugation. Homologous recombination then results in antibiotic resistant single-crossover mutants in which the plasmid has integrated site-specifically into the chromosome. Subsequently, unmarked double-crossover mutants are isolated directly using sucrose-mediated counter-selection. This two-step process yields seamless mutations that are precise to a single base pair of DNA. The entire procedure requires ~2 weeks. PMID:26492139

Induction by alkylating agents of sister chromatid exchanges and chromatid breaks in Fanconi's anemia.

PubMed

Latt, S A; Stetten, G; Juergens, L A; Buchanan, G R; Gerald, P S

1975-10-01

Sister chromatid exchanges, which may reflect chromosome repair in response to certain types of DNA damage, provide a means of investigating the increased chromosome fragility characteristic of Fanconi's anemia. By a recently developed technique using 33258 Hoechst and 5-bromodeoxyuridine, it was observed that the baseline frequency of sister chromatid exchanges in phytohemagglutinin-stimulated lymphocytes from four males with Fanconi's anemia differed little from that of normal lymphocytes. However, addition of the bifunctional alkylating agent mitomycin C (0.01 or 0.03 mug/ml) to the Fanconi's anemia cells during culture induces less than half of the increase in exchanges found in identically treated normal lymphocytes. This reduced increment in exchanges in accompanied by a partial suppression of mitosis and a marked increase in chromatid breaks and rearrangements. Many of these events occur at sites of incomplete chromatid interchange. The increase in sister chromatid exchanges induced in Fanconi's anemia lymphocytes by the monofunctional alkylating agent ethylmethane sulfonate (0.25 mg/ml) was slightly less than that in normal cells. Lymphocytes from two sets of parents of the patients with Fanconi's anemia exhibited a normal response to alkylating agents, while dermal fibroblasts from two different patients with Fanconi's anemia reacted to mitomycin C with an increase in chromatid breaks, but a nearly normal increment of sister chromatid exchanges. The results suggest that chromosomal breaks and rearrangements in Fanconi's anemia lymphocytes may result from a defect in a form of repair of DNA damage.

Chromosomal Translocations: Chicken or Egg? | Center for Cancer Research

Cancer.gov

Many tumor cells have abnormal chromosomes. Some of these abnormalities are caused by chromosomal translocations, which occur when two chromosomes break and incorrectly rejoin, resulting in an exchange of genetic material. Translocations can activate oncogenes, silence tumor suppressor genes, or result in the creation of completely new fusion gene products. While there is little doubt that chromosomal translocations can contribute to cancer, there is an active "chicken and the egg" discussion about the role translocations and other chromosomal abnormalities play—do they actually cause cancer or merely occur because of other changes within the cancer cell.  

Tolerance of DNA Mismatches in Dmc1 Recombinase-mediated DNA Strand Exchange.

PubMed

Borgogno, María V; Monti, Mariela R; Zhao, Weixing; Sung, Patrick; Argaraña, Carlos E; Pezza, Roberto J

2016-03-04

Recombination between homologous chromosomes is required for the faithful meiotic segregation of chromosomes and leads to the generation of genetic diversity. The conserved meiosis-specific Dmc1 recombinase catalyzes homologous recombination triggered by DNA double strand breaks through the exchange of parental DNA sequences. Although providing an efficient rate of DNA strand exchange between polymorphic alleles, Dmc1 must also guard against recombination between divergent sequences. How DNA mismatches affect Dmc1-mediated DNA strand exchange is not understood. We have used fluorescence resonance energy transfer to study the mechanism of Dmc1-mediated strand exchange between DNA oligonucleotides with different degrees of heterology. The efficiency of strand exchange is highly sensitive to the location, type, and distribution of mismatches. Mismatches near the 3' end of the initiating DNA strand have a small effect, whereas most mismatches near the 5' end impede strand exchange dramatically. The Hop2-Mnd1 protein complex stimulates Dmc1-catalyzed strand exchange on homologous DNA or containing a single mismatch. We observed that Dmc1 can reject divergent DNA sequences while bypassing a few mismatches in the DNA sequence. Our findings have important implications in understanding meiotic recombination. First, Dmc1 acts as an initial barrier for heterologous recombination, with the mismatch repair system providing a second level of proofreading, to ensure that ectopic sequences are not recombined. Second, Dmc1 stepping over infrequent mismatches is likely critical for allowing recombination between the polymorphic sequences of homologous chromosomes, thus contributing to gene conversion and genetic diversity. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Tolerance of DNA Mismatches in Dmc1 Recombinase-mediated DNA Strand Exchange*

PubMed Central

Borgogno, María V.; Monti, Mariela R.; Zhao, Weixing; Sung, Patrick; Argaraña, Carlos E.; Pezza, Roberto J.

2016-01-01

Recombination between homologous chromosomes is required for the faithful meiotic segregation of chromosomes and leads to the generation of genetic diversity. The conserved meiosis-specific Dmc1 recombinase catalyzes homologous recombination triggered by DNA double strand breaks through the exchange of parental DNA sequences. Although providing an efficient rate of DNA strand exchange between polymorphic alleles, Dmc1 must also guard against recombination between divergent sequences. How DNA mismatches affect Dmc1-mediated DNA strand exchange is not understood. We have used fluorescence resonance energy transfer to study the mechanism of Dmc1-mediated strand exchange between DNA oligonucleotides with different degrees of heterology. The efficiency of strand exchange is highly sensitive to the location, type, and distribution of mismatches. Mismatches near the 3′ end of the initiating DNA strand have a small effect, whereas most mismatches near the 5′ end impede strand exchange dramatically. The Hop2-Mnd1 protein complex stimulates Dmc1-catalyzed strand exchange on homologous DNA or containing a single mismatch. We observed that Dmc1 can reject divergent DNA sequences while bypassing a few mismatches in the DNA sequence. Our findings have important implications in understanding meiotic recombination. First, Dmc1 acts as an initial barrier for heterologous recombination, with the mismatch repair system providing a second level of proofreading, to ensure that ectopic sequences are not recombined. Second, Dmc1 stepping over infrequent mismatches is likely critical for allowing recombination between the polymorphic sequences of homologous chromosomes, thus contributing to gene conversion and genetic diversity. PMID:26709229

Characterization of susceptible chiasma configurations that increase the risk for maternal nondisjunction of chromosome 21.

PubMed

Lamb, N E; Feingold, E; Savage, A; Avramopoulos, D; Freeman, S; Gu, Y; Hallberg, A; Hersey, J; Karadima, G; Pettay, D; Saker, D; Shen, J; Taft, L; Mikkelsen, M; Petersen, M B; Hassold, T; Sherman, S L

1997-09-01

Recent studies of trisomy 21 have shown that altered levels of recombination are associated with maternal non-disjunction occurring at both meiosis I (MI) and meiosis II (MII). To comprehend better the association of recombination with nondisjunction, an understanding of the pattern of meiotic exchange, i.e. the exchange of genetic material at the four-strand stage during prophase, is required. We examined this underlying exchange pattern to determine if specific meiotic configurations are associated with a higher risk of non-disjunction than others. We examined the crossover frequencies of chromosome 21 for three populations: (i) normal female meiotic events; (ii) meiotic events leading to MI non-disjunction; and (iii) those leading to MII non-disjunction. From these crossover frequencies, we estimated the array of meiotic tetrads that produced the observed crossovers. Using this approach, we found that nearly one-half of MI errors were estimated to be achiasmate. The majority of the remaining MI bivalents had exchanges that clustered at the telomere. In contrast, exchanges occurring among MII cases clustered at the pericentromeric region of the chromosome. Unlike the single exchange distributions, double exchanges from the non-disjoined populations seemed to approximate the distribution in the normal population. These data suggest that the location of certain exchanges makes a tetrad susceptible to non-disjunction. Specifically, this susceptibility is associated with the distance between the centromere and closest exchange. This result challenges the widely held concept that events occurring at MII are largely independent of events occurring at MI, and suggests that all non-disjunction events may be initiated during MI and simply resolved at either of the two meiotic stages.

M-BAND Study of Radiation-Induced Chromosome Aberrations in Human Epithelial Cells: Radiation Quality and Dose Rate Effects

NASA Technical Reports Server (NTRS)

Hada, Megumi; Cucinotta, Francis; Wu, Honglu

2009-01-01

The advantage of the multicolor banding in situ hybridization (mBAND) technique is its ability to identify both inter- (translocation to unpainted chromosomes) and intra- (inversions and deletions within a single painted chromosome) chromosome aberrations simultaneously. To study the detailed rearrangement of low- and high-LET radiation induced chromosome aberrations in human epithelial cells (CH184B5F5/M10) in vitro, we performed a series of experiments with Cs-137 gamma rays of both low and high dose rates, neutrons of low dose rate and 600 MeV/u Fe ions of high dose rate, with chromosome 3 painted with multi-binding colors. We also compared the chromosome aberrations in both 2- and 3-dimensional cell cultures. Results of these experiments revealed the highest chromosome aberration frequencies after low dose rate neutron exposures. However, detailed analysis of the radiation induced inversions revealed that all three radiation types induced a low incidence of simple inversions. Most of the inversions in gamma-ray irradiated samples were accompanied by other types of intra-chromosomal aberrations but few inversions were accompanied by inter-chromosomal aberrations. In contrast, neutrons and Fe ions induced a significant fraction of inversions that involved complex rearrangements of both inter- and intrachromosomal exchanges. The location of the breaks involved in chromosome exchanges was analyzed along the painted chromosome. The breakpoint distribution was found to be randomly localized on chromosome 3 after neutron or Fe ion exposure, whereas non-random distribution with clustering breakpoints was observed after -ray exposure. Our comparison of chromosome aberration yields between 2- and 3-dimensional cell cultures indicated a significant difference for gamma exposures, but not for Fe ion exposures. These experimental results indicated that the track structure of the radiation and the cellular/chromosome structure can both affect radiation-induced chromosome aberrations.

Biological Effectiveness of Accelerated Particles for the Induction of Chromosome Damage Measured in Metaphase and Interphase Human Lymphocytes

NASA Technical Reports Server (NTRS)

George, Kerry; Durante, Marco; Willingham, Veronica; Wu, Honglu; Yang, Tracy C.; Cucinotta, Francis A.

2003-01-01

Chromosome aberrations were investigated in human lymphocytes after in vitro exposure to 1H-, 3He-, 12C-, 40Ar-, 28Si-, 56Fe-, or 197Au-ion beams, with LET ranging from approximately 0.4-1393 keV/microm in the dose range of 0.075-3 Gy. Dose-response curves for chromosome exchanges, measured at the first mitosis postirradiation using fluorescence in situ hybridization (FISH) with whole-chromosome probes, were fitted with linear or linear-quadratic functions. The relative biological effectiveness (RBE) was estimated from the initial slope of the dose-response curve for chromosomal damage with respect to low- or high-dose-rate gamma rays. Estimates of RBEmax values for mitotic spreads, which ranged from near 0.7 to 11.1 for total exchanges, increased with LET, reaching a maximum at about 150 keV/microm, and decreased with further increase in LET. RBEs for complex aberrations are undefined due to the lack of an initial slope for gamma rays. Additionally, the effect of mitotic delay on RBE values was investigated by measuring chromosome aberrations in interphase after chemically induced premature chromosome condensation (PCC), and values were up to threefold higher than for metaphase analysis.

Alpha-Particle-Induced Complex Chromosome Exchanges Transmitted through Extra-Thymic Lymphopoiesis In Vitro Show Evidence of Emerging Genomic Instability

PubMed Central

Sumption, Natalia; Goodhead, Dudley T.; Anderson, Rhona M.

2015-01-01

Human exposure to high-linear energy transfer α-particles includes environmental (e.g. radon gas and its decay progeny), medical (e.g. radiopharmaceuticals) and occupational (nuclear industry) sources. The associated health risks of α-particle exposure for lung cancer are well documented however the risk estimates for leukaemia remain uncertain. To further our understanding of α-particle effects in target cells for leukaemogenesis and also to seek general markers of individual exposure to α-particles, this study assessed the transmission of chromosomal damage initially-induced in human haemopoietic stem and progenitor cells after exposure to high-LET α-particles. Cells surviving exposure were differentiated into mature T-cells by extra-thymic T-cell differentiation in vitro. Multiplex fluorescence in situ hybridisation (M-FISH) analysis of naïve T-cell populations showed the occurrence of stable (clonal) complex chromosome aberrations consistent with those that are characteristically induced in spherical cells by the traversal of a single α-particle track. Additionally, complex chromosome exchanges were observed in the progeny of irradiated mature T-cell populations. In addition to this, newly arising de novo chromosome aberrations were detected in cells which possessed clonal markers of α-particle exposure and also in cells which did not show any evidence of previous exposure, suggesting ongoing genomic instability in these populations. Our findings support the usefulness and reliability of employing complex chromosome exchanges as indicators of past or ongoing exposure to high-LET radiation and demonstrate the potential applicability to evaluate health risks associated with α-particle exposure. PMID:26252014

Non-Target Effect for Chromosome Aberrations in Human Lymphocytes and Fibroblasts After Exposure to Very Low Doses of High LET Radiation

NASA Technical Reports Server (NTRS)

Hada, Megumi; George, Kerry A.; Cucinotta, F. A.

2011-01-01

The relationship between biological effects and low doses of absorbed radiation is still uncertain, especially for high LET radiation exposure. Estimates of risks from low-dose and low-dose-rates are often extrapolated using data from Japanese atomic bomb survivor with either linear or linear quadratic models of fit. In this study, chromosome aberrations were measured in human peripheral blood lymphocytes and normal skin fibroblasts cells after exposure to very low dose (.01 - 0.2 Gy) of 170 MeV/u Si-28-ions or 600 MeV/u Fe-56-ions. Chromosomes were analyzed using the whole chromosome fluorescence in situ hybridization (FISH) technique during the first cell division after irradiation, and chromosome aberrations were identified as either simple exchanges (translocations and dicentrics) or complex exchanges (involving >2 breaks in 2 or more chromosomes). The curves for doses above 0.1 Gy were more than one ion traverses a cell showed linear dose responses. However, for doses less than 0.1 Gy, Si-28-ions showed no dose response, suggesting a non-targeted effect when less than one ion traversal occurs. Additional findings for Fe-56 will be discussed.

Sister chromatid exchange rate and alkaline comet assay scores in patients with ovarian cancer.

PubMed

Baltaci, Volkan; Kayikçioğlu, Fulya; Alpas, Idil; Zeyneloğlu, Hulusi; Haberal, Ali

2002-01-01

Sister chromatid exchange (SCE) frequencies were studied in patients with different types of ovarian malignancies and in healthy volunteers. The level of DNA damage in patients with ovarian malignancy and control subjects has also been studied by alkaline single cell gel electrophoresis (SCGE), also known as the comet assay. Peripheral blood was collected from 30 patients after histological confirmation of malignancy and 20 healthy female volunteers. The cells were evaluated according to their grade of damage. We found that the sister chromatid exchange frequencies of cancer cases were significantly greater than that of controls (P < 0.001). The frequency of exchange in chromosomal groups A, B, and C, which include chromosomes 1-12, was higher than that of the other chromosomal groups in both groups. Comparison of the results of the alkaline comet assay in patient and control subjects showed a significant difference in the number of damaged cells. The frequency of limited migrated and extensive migrated cells in the women with ovarian malignancies was higher than that of control women (P < 0.001). SCE and SCGE can be used successfully to monitor DNA damage in women with ovarian cancer.

Interpreting Chromosome Aberration Spectra

NASA Technical Reports Server (NTRS)

Levy, Dan; Reeder, Christopher; Loucas, Bradford; Hlatky, Lynn; Chen, Allen; Cornforth, Michael; Sachs, Rainer

2007-01-01

Ionizing radiation can damage cells by breaking both strands of DNA in multiple locations, essentially cutting chromosomes into pieces. The cell has enzymatic mechanisms to repair such breaks; however, these mechanisms are imperfect and, in an exchange process, may produce a large-scale rearrangement of the genome, called a chromosome aberration. Chromosome aberrations are important in killing cells, during carcinogenesis, in characterizing repair/misrepair pathways, in retrospective radiation biodosimetry, and in a number of other ways. DNA staining techniques such as mFISH ( multicolor fluorescent in situ hybridization) provide a means for analyzing aberration spectra by examining observed final patterns. Unfortunately, an mFISH observed final pattern often does not uniquely determine the underlying exchange process. Further, resolution limitations in the painting protocol sometimes lead to apparently incomplete final patterns. We here describe an algorithm for systematically finding exchange processes consistent with any observed final pattern. This algorithm uses aberration multigraphs, a mathematical formalism that links the various aspects of aberration formation. By applying a measure to the space of consistent multigraphs, we will show how to generate model-specific distributions of aberration processes from mFISH experimental data. The approach is implemented by software freely available over the internet. As a sample application, we apply these algorithms to an aberration data set, obtaining a distribution of exchange cycle sizes, which serves to measure aberration complexity. Estimating complexity, in turn, helps indicate how damaging the aberrations are and may facilitate identification of radiation type in retrospective biodosimetry.

Graph Model of Coalescence with Recombinations

NASA Astrophysics Data System (ADS)

Parida, Laxmi

One of the primary genetic events shaping an autosomal chromosome is recombination. This is a process that occurs during meiosis, in eukaryotes, that results in the offsprings having different combinations of (homologous) genes, or chromosomal segments, of the two parents. The presence of these recombination events in the evolutionary history of each chromosome complicates the genetic landscape of a population, and understanding the manifestations of these genetic exchanges in the chromosome sequences has been a subject of intense curiosity (see [Hud83, Gri99, HSW05] and citations therein).

Rejoining and misrejoining of radiation-induced chromatin breaks. IV. Charged particles

NASA Technical Reports Server (NTRS)

Durante, M.; Furusawa, Y.; George, K.; Gialanella, G.; Greco, O.; Grossi, G.; Matsufuji, N.; Pugliese, M.; Yang, T. C.

1998-01-01

We have recently reported the kinetics of chromosome rejoining and exchange formation in human lymphocytes exposed to gamma rays using the techniques of fluorescence in situ hybridization (FISH) and premature chromosome condensation (PCC). In this paper, we have extended previous measurements to cells exposed to charged particles. Our goal was to determine differences in chromatin break rejoining and misrejoining after exposure to low- and high-linear energy transfer (LET) radiation. Cells were irradiated with hydrogen, neon, carbon or iron ions in the LET range 0.3-140 keV/microm and were incubated at 37 degrees C for various times after exposure. Little difference was observed in the yield of early prematurely condensed chromosome breaks for the different ions. The kinetics of break rejoining was exponential for all ions and had similar time constants, but the residual level of unrejoined breaks after prolonged incubation was higher for high-LET radiation. The kinetics of exchange formation was also similar for the different ions, but the yield of chromosome interchanges measured soon after exposure was higher for high-LET particles, suggesting that a higher fraction of DNA breaks are misrejoined quickly. On the other hand, the rate of formation of complete exchanges was slightly lower for densely ionizing radiation. The ratios between the yields of different types of aberrations observed at 10 h postirradiation in prematurely condensed chromosome preparations were dependent on LET. We found significant differences between the yields of aberrations measured in interphase (after repair) and metaphase for densely ionizing radiation. This difference might be caused by prolonged mitotic delay and/or interphase death. Overall, the results point out significant differences between low- and high-LET radiation for the formation of chromosome aberrations.

Analysis of Chromosomal Aberrations in the Blood Lymphocytes of Astronauts after Space Flight

NASA Technical Reports Server (NTRS)

George, K.; Kim, M. Y.; Elliott, T.; Cucinotta, F. A.

2007-01-01

It is a NASA requirement that biodosimetry analysis be performed on all US astronauts who participate in long duration missions of 3 months or more onboard the International Space Station. Cytogenetic analysis of blood lymphocytes is the most sensitive and reliable biodosimetry method available at present, especially if chromosome damage is assessed before as well as after space flight. Results provide a direct measurement of space radiation damage in vivo that takes into account individual radiosensitivity and considers the influence of microgravity and other stress conditions. We present data obtained from all twenty-five of the crewmembers who have participated in the biodosimetry program so far. The yield of chromosome exchanges, measured using fluorescence in situ hybridization (FISH) technique with chromosome painting probes, increased after space flight for all these individuals. In vivo dose was derived from frequencies of chromosome exchanges using preflight calibration curves of in vitro exposed cells from the same individual, and RBE was compared with individually measured physically absorbed dose and projected organ dose equivalents. Biodosimetry estimates using samples collected within a few weeks of return from space lie within the range expected from physical dosimetry. For some of these individuals chromosome aberrations were assessed again several months after their respective missions and a temporal decline in stable exchanges was observed in some cases, suggesting that translocations are unstable with time after whole body exposure to space radiation. This may indicate complications with the use of translocations for retrospective dose reconstruction. Data from one crewmember who has participated in two separate long duration space missions and has been followed up for over 10 years provides limited data on the effect of repeat flights and shows a possible adaptive response to space radiation exposure.

The Influence of Shielding on the Biological Effectiveness of Accelerated Particles for the Induction of Chromosome Damages

NASA Technical Reports Server (NTRS)

George, K.; Cucinotta, F. A.

2006-01-01

Chromosome damage was assessed in human peripheral blood lymphocytes after in vitro exposure to the either Si-28 (490 or 600 MeV/n), Ti-48 (1000 MeV/n), or Fe-56 (600, 1000, or 5000 MeV/n). LET values for these ions ranged from approximately 50 to 174 keV/micrometers and doses ranged from 10 to 200 cGy. The effect of either aluminum or polyethylene shielding on the induction of chromosome aberrations was investigated for each ion. Chromosome exchanges were measured using fluorescence in situ hybridization (FISH) with whole chromosome probes in cells collected 48-56 hours after irradiation using a chemical-induced premature chromosome condensation (PCC) technique. The yield of chromosomal aberrations increased linearly with dose and the relative biological effectiveness (RBE) for the primary beams, estimated from the initial slope of the dose response curve for total chromosomal exchanges with respect to gamma-rays, ranged from 14 to 35. The RBE values increased with LET, reaching a maximum for the 1 GeV/n Fe ions with LET of 150 keV/micrometers, and decreased with further increases in LET. When LET of the primary beam was in the region of increasing RBE (i.e. below approximately 100 keV/micrometers), the addition of shielding material increased the effectiveness per unit dose. Whereas shielding decreased the effectiveness per unit dose when the LET of the primary particle beam was higher than 150 keV/micrometers.

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).

Relationship of Chromosome Changes to Neoplastic Cell Transformation

PubMed Central

DiPaolo, Joseph A.; Popescu, Nicolae C.

1976-01-01

Chromosomal abnormalities are a frequent concomitant of neoplasia, and although it is tempting to relate these mutations and alterations in chromatin (DNA) function to cancer, their relationship to the initiation or progression of carcinogenesis is unknown. Mammalian cells in culture, after interacting with chemical carcinogens, often exhibit chromosome damage consisting of breaks and exchanges of chromatid material. The pattern of damage of banded metaphases indicates that negative bands are especially vulnerable to the action of chemical carcinogens, probably because of differential chromatin condensation. Damage to individual chromosomes may be random or nonrandom, depending on the species. Cell death can be correlated with chromatid alterations that occur shortly after treatment with chemical carcinogens. There is also a correlation between mutagenic and carcinogenic activity of some chemical carcinogens and the frequency of sister chromatid exchanges. The question of whether specific chromosome changes are absolutely required for neoplastic transformation cannot be answered because of conflicting data and diverse results from studies even with known carcinogens. Cell transformation may occur without any visible chromosome changes. A universal specific numerical or visible structural chromosomal alteration is not necessarily associated with chemical or viral transformation. Chromosome changes are independent of the etiologic agents: different carcinogens may produce transformation associated with the same abnormal chromosomes, but not all transformed lines invariably exhibit the same abnormality, even with the same chemical. In some species, chromosome having nucleolar organizer regions may be more frequently involved in numerical or structural deviations. Progressively growing tumors also may occur as a result of the proliferation of transformed cells without detectable chromosome changes, indicating that tumorigenicity need not be related to an imbalance of chromosome number or structure. Our studies indicate that chromosome changes are not essential for establishment of neoplasms but that karyotypic instability may result in response to selective growth pressures. ImagesFigure 2Figure 11Figure 3Figure 12Figure 4Figure 5Figure 6Figure 7Figure 8Figure 9Figure 1Figure 10 PMID:826168

CYTOGENETIC ANALYSES OF MICE EXPOSED TO DICHLOROMETHANE

EPA Science Inventory

Chromosome damage was studied in female B6C3F1 mice exposed to dichloromethane (DCM) by subcutaneous or inhalation treatments. o increase in either the frequencies of sister chromatid exchanges (SCEs) or chromosome aberrations (CAs) in bone marrow cells was observed after a singl...

Track Structure and the Biological Effectiveness of Accelerated Particles for the Induction of Chromosome Damage

NASA Technical Reports Server (NTRS)

George, K.; Hada, M.; Chappell, L.; Cucinotta, F. A.

2011-01-01

Track structure models predict that at a fixed value of LET, particles with lower charge number, Z will have a higher biological effectiveness compared to particles with a higher Z. In this report we investigated how track structure effects induction of chromosomal aberration in human cells. Human lymphocytes were irradiated in vitro with various energies of accelerated iron, silicon, neon, or titanium ions and chromosome damage was assessed in using three color FISH chromosome painting in chemically induced PCC samples collected a first cell division post irradiation. The LET values for these ions ranged from 30 to195 keV/micron. Of the particles studied, Neon ions have the highest biological effectiveness for induction of total chromosome damage, which is consistent with track structure model predictions. For complex-type exchanges 64 MeV/ u Neon and 450 MeV/u Iron were equally effective and induced the most complex damage. In addition we present data on chromosomes exchanges induced by six different energies of protons (5 MeV/u to 2.5 GeV/u). The linear dose response term was similar for all energies of protons suggesting that the effect of the higher LET at low proton energies is balanced by the production of nuclear secondaries from the high energy protons.

In vivo and in vitro measurements of complex-type chromosomal exchanges induced by heavy ions.

PubMed

George, K; Durante, M; Wu, H; Willingham, V; Cucinotta, F A

2003-01-01

Heavy ions are more efficient in producing complex-type chromosome exchanges than sparsely ionizing radiation, and this can potentially be used as a biomarker of radiation quality. We measured the induction of complex-type chromosomal aberrations in human peripheral blood lymphocytes exposed in vitro to accelerated H-, He-, C-, Ar-, Fe- and Au-ions in the LET range of approximately 0.4-1400 keV/micrometers. Chromosomes were analyzed either at the first post-irradiation mitosis, or in interphase, following premature condensation by phosphatase inhibitors. Selected chromosomes were then visualized after FISH-painting. The dose-response curve for the induction of complex-type exchanges by heavy ions was linear in the dose-range 0.2-1.5 Gy, while gamma-rays did not produce a significant increase in the yield of complex rearrangements in this dose range. The yield of complex aberrations after 1 Gy of heavy ions increased up to an LET around 100 keV/micrometers, and then declined at higher LET values. When mitotic cells were analyzed, the frequency of complex rearrangements after 1 Gy was about 10 times higher for Ar- or Fe- ions (the most effective ions, with LET around 100 keV/micrometers) than for 250 MeV protons, and values were about 35 times higher in prematurely condensed chromosomes. These results suggest that complex rearrangements may be detected in astronauts' blood lymphocytes after long-term space flight, because crews are exposed to HZE particles from galactic cosmic radiation. However, in a cytogenetic study of ten astronauts after long-term missions on the Mir or International Space Station, we found a very low frequency of complex rearrangements, and a significant post-flight increase was detected in only one out of the ten crewmembers. It appears that the use of complex-type exchanges as biomarker of radiation quality in vivo after low-dose chronic exposure in mixed radiation fields is hampered by statistical uncertainties. c2003 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

Dose Response for Chromosome Aberrations in Human Lymphocytes and Fibroblasts After Exposure to Very Low Dose of High Let Radiation

NASA Technical Reports Server (NTRS)

Hada, M.; George, K.; Chappell, L.; Cucinotta, F. A.

2011-01-01

The relationship between biological effects and low doses of absorbed radiation is still uncertain, especially for high LET radiation exposure. Estimates of risks from low-dose and low-dose-rates are often extrapolated using data from Japanese atomic bomb survivor with either linear or linear quadratic models of fit. In this study, chromosome aberrations were measured in human peripheral blood lymphocytes and normal skin fibroblasts cells after exposure to very low dose (0.01 - 0.20 Gy) of 170 MeV/u Si-28 ions or 600 MeV/u Fe-56 ions, including doses where on average less than one direct ion traversal per cell nucleus occurs. Chromosomes were analyzed using the whole-chromosome fluorescence in situ hybridization (FISH) technique during the first cell division after irradiation, and chromosome aberrations were identified as either simple exchanges (translocations and dicentrics) or complex exchanges (involving >2 breaks in 2 or more chromosomes). The responses for doses above 0.1 Gy (more than one ion traverses a cell) showed linear dose responses. However, for doses less than 0.1 Gy, both Si-28 ions and Fe-56 ions showed a dose independent response above background chromosome aberrations frequencies. Possible explanations for our results are non-targeted effects due to aberrant cell signaling [1], or delta-ray dose fluctuations [2] where a fraction of cells receive significant delta-ray doses due to the contributions of multiple ion tracks that do not directly traverse cell nuclei where chromosome aberrations are scored.

The Influence of Shielding on the Biological Effectiveness of Accelerated Particles for the Induction of Chromosome Damage

NASA Technical Reports Server (NTRS)

Goeorge, Kerry; Cucinotta, Francis A.

2007-01-01

Chromosome damage was assessed in human peripheral blood lymphocytes after in vitro exposure to the either Si-28 (490 or 600 MeV/n), Ti-48 (1000 MeV/n), or Fe-56 (600, 1000, or 5000 MeV/n). LET values for these ions ranged from 51 to 184 keV/micron and doses ranged from 10 to 200 cGy. The effect of either aluminum or polyethylene shielding on the induction of chromosome aberrations was investigated for each ion. Chromosome exchanges were measured using fluorescence in situ hybridization (FISH) with whole chromosome probes in cells collected at G2 and mitosis in first division post irradiation after chromosomes were prematurely condensed using calyculin-A. The yield of chromosomal aberrations increased linearly with dose and the relative biological effectiveness (RBE) for the primary beams, estimated from the initial slope of the dose response curve for total chromosomal exchanges with respect to gamma-rays, ranged from 9 to 35. The RBE values increased with LET, reaching a maximum for the 600 MeV/n Fe ions with LET of 184 keV/micron. When the LET of the primary beam was below approximately 100 keV/micron, the addition of shielding material increased the effectiveness per unit dose. Whereas shielding decreased the effectiveness per unit dose when the LET of primary beams was higher than 100 keV/micron. The yield of aberrations correlated with the dose-average LET of the beam after traversal through the shielding.

Isolation and molecular analysis of inv dup(15) and construction of a physical map of a common breakpoint in order to elucidate their mechanism of formation.

PubMed

Wandstrat, A E; Schwartz, S

2000-11-01

An inverted duplication of chromosome 15 [inv dup(15)] is the most common supernumerary marker chromosome, comprising approximately 50% of all chromosomes in this class. Structurally, the inv dup(15) is a mirror image with the central axis defining a distal break within either the heterochromatic alpha-satellite array or along the euchromatin in the long (q) arm of the chromosome. There are several types of inv dup(15), classified by the amount of euchromatic material present. Generally, they are bisatellited, pseudodicentric and have a breakpoint in 15q11-q14. A suggested mechanism of formation of inv dup(15) involves illegitimate recombination between homologous chromosomes followed by nondisjunction and centromere inactivation. The proximal portion of chromosome 15 contains several low-copy repeat sequence families and it has been hypothesized that errors in pairing among these repeats may result in structural rearrangements of this chromosome including the inv dup(15). To test this hypothesis and to determine the mechanism of formation, the inv dup(15) from four cases was isolated in somatic cell hybrids and polymerase chain reaction microsatellite markers were used to determine the origin of exchange. Two appeared to result from interchromosomal and two from intrachromosomal exchange, one of which occurred post-recombination. In addition, a detailed physical map of the breakpoint region in the largest inv dup(15) was constructed placing eight new sequence-tagged sites and ten new bacterial artificial chromosome markers in the region.

Direct evidence of a role for heterochromatin in meiotic chromosome segregation.

PubMed

Dernburg, A F; Sedat, J W; Hawley, R S

1996-07-12

We have investigated the mechanism that enables achiasmate chromosomes to segregate from each other at meiosis I in D. melanogaster oocytes. Using novel cytological methods, we asked whether nonexchange chromosomes are paired prior to disjunction. Our results show that the heterochromatin of homologous chromosomes remains associated throughout prophase until metaphase I regardless of whether they undergo exchange, suggesting that homologous recognition can lead to segregation even in the absence of chiasmata. However, partner chromosomes lacking homology do not pair prior to disjunction. Furthermore, euchromatic synapsis is not maintained throughout prophase. These observations provide a physical demonstration that homologous and heterologous achiasmate segregations occur by different mechanisms and establish a role for heterochromatin in maintaining the alignment of chromosomes during meiosis.

Biological effectiveness of accelerated particles for the induction of chromosome damage: track structure effects.

PubMed

George, Kerry A; Hada, Megumi; Chappell, Lori; Cucinotta, Francis A

2013-07-01

We have investigated how radiation quality affects the induction of chromosomal aberrations in human cells. Human lymphocytes were irradiated in vitro with various energies of accelerated high charge and energy (HZE) particles including oxygen, neon, silicon, titanium and iron. Chromosome damage was assessed using three-color FISH chromosome painting in chemically induced premature chromosome condensation samples collected at first cell division after irradiation. The LET values for these particles ranged from 30 to 195 keV/μm, and their energies ranged from about 55 MeV/u to more than 1,000 MeV/u. The 89 and 142 MeV/u neon particles produced the most simple-type reciprocal exchanges per unit dose. For complex-type exchanges, 64 MeV/u neon and 450 MeV/u iron were equally effective and induced the greatest amount of complex damage. Track structure models predict that at a fixed value of LET, particles with lower charge number (Z) will have a higher biological effectiveness compared to particles with a higher Z, and that a saturation cross section will be observed for different radiation qualities. Our results are consistent with model expectations within the limitation of experimental error, and provide the most extensive data that have been reported on the radiation quality dependences of chromosomal aberrations. © 2013 by Radiation Research Society

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

Patterns of genetic variation across inversions: geographic variation in the In(2L)t inversion in populations of Drosophila melanogaster from eastern Australia.

PubMed

Kennington, W Jason; Hoffmann, Ary A

2013-05-20

Chromosomal inversions are increasingly being recognized as important in adaptive shifts and are expected to influence patterns of genetic variation, but few studies have examined genetic patterns in inversion polymorphisms across and within populations. Here, we examine genetic variation at 20 microsatellite loci and the alcohol dehydrogenase gene (Adh) located within and near the In(2L)t inversion of Drosophila melanogaster at three different sites along a latitudinal cline on the east coast of Australia. We found significant genetic differentiation between the standard and inverted chromosomal arrangements at each site as well as significant, but smaller differences among sites in the same arrangement. Genetic differentiation between pairs of sites was higher for inverted chromosomes than standard chromosomes, while inverted chromosomes had lower levels of genetic variation even well away from inversion breakpoints. Bayesian clustering analysis provided evidence of genetic exchange between chromosomal arrangements at each site. The strong differentiation between arrangements and reduced variation in the inverted chromosomes are likely to reflect ongoing selection at multiple loci within the inverted region. They may also reflect lower effective population sizes of In(2L)t chromosomes and colonization of Australia, although there was no consistent evidence of a recent bottleneck and simulations suggest that differences between arrangements would not persist unless rates of gene exchange between them were low. Genetic patterns therefore support the notion of selection and linkage disequilibrium contributing to inversion polymorphisms, although more work is needed to determine whether there are spatially varying targets of selection within this inversion. They also support the idea that the allelic content within an inversion can vary between geographic locations.

Chromosome Aberrations in Normal and Ataxia-Telangiectasia Cells Exposed to Heavy Ions

NASA Technical Reports Server (NTRS)

Kawata, T.; Ito, H.; Liu, C.; Shigematsu, N.; George, K.; Cucinotta, F. A.

2007-01-01

Although cells derived from Ataxia Telangiectasia (AT) patients are known to exhibit abnormal responses to ionizing radiations, its underlying mechanism still remains unclear. Previously, the authors reported that at the same gamma-irradiation dose AT cells show higher frequencies of misrepair and deletions compared to normal human fibroblast cells. In this study, we investigated the effects of heavy ions beams on chromosomal aberrations in normal and AT cells. Normal and AT fibroblast cells arrested at G0/G1 phase were irradiated with 2 Gy of X-rays, 490 MeV/u Silicon (LET 55 keV/m), 500 MeV/u Iron (LET 185 keV/m) and 200 MeV/u Iron (LET 440 keV/m) particles, and then cells were allowed to repair for 24 hours at 37 degrees before subculture. Calyculin-A induced PCC method was employed to collect G2/M chromosomes and whole DNA probes 1 and 3 were used to analyze chromosomal aberrations such as color-junctions, deletions, simple exchanges (incomplete and reciprocal exanges) and complex-type exchanges. The percentages of aberrant cells were higher when normal and AT cells were exposed to heavy ions compared to X-rays, and had a tendency to increase with increasing LET up to 185 keV/m and then decreased at 440 keV/m. When the frequency of color-junctions per cell was compared after X-ray exposure, AT cells had around three times higher frequency of color-junctions (mis-rejoining) than normal cells. However, at 185 keV/m there was no difference in the frequency of color-junctions between two cell lines. It was also found that the frequency of simple exchanges per cell was almost constant in AT cells regardless LET levels, but it was LET dependent for normal cells. Interestingly, the frequency of simple exchanges was higher for AT cells when it was compared at 185 keV/m but AT cells had more complex-type exchanges at the same LET levels. Heavy ions are more efficient in inducing chromosome aberrations in normal and AT cells compared to X-rays, and the aberration types between normal and AT fibroblast appeared different probably due to difference in the ATM gene function.

Molecular population genetics of inversion breakpoint regions in Drosophila pseudoobscura.

PubMed

Wallace, Andre G; Detweiler, Don; Schaeffer, Stephen W

2013-07-08

Paracentric inversions in populations can have a profound effect on the pattern and organization of nucleotide variability along a chromosome. Regions near inversion breakpoints are expected to have greater levels of differentiation because of reduced genetic exchange between different gene arrangements whereas central regions in the inverted segments are predicted to have lower levels of nucleotide differentiation due to greater levels of genetic flux among different karyotypes. We used the inversion polymorphism on the third chromosome of Drosophila pseudoobscura to test these predictions with an analysis of nucleotide diversity of 18 genetic markers near and away from inversion breakpoints. We tested hypotheses about how the presence of different chromosomal arrangements affects the pattern and organization of nucleotide variation. Overall, markers in the distal segment of the chromosome had greater levels of nucleotide heterozygosity than markers within the proximal segment of the chromosome. In addition, our results rejected the hypothesis that the breakpoints of derived inversions will have lower levels of nucleotide variability than breakpoints of ancestral inversions, even when strains with gene conversion events were removed. High levels of linkage disequilibrium were observed within all 11 breakpoint regions as well as between the ends of most proximal and distal breakpoints. The central region of the chromosome had the greatest levels of linkage disequilibrium compared with the proximal and distal regions because this is the region that experiences the highest level of recombination suppression. These data do not fully support the idea that genetic exchange is the sole force that influences genetic variation on inverted chromosomes.

Cloning, characterization, and chromosomal mapping of a human electroneutral Na(+)-driven Cl-HCO3 exchanger.

PubMed

Grichtchenko, I I; Choi, I; Zhong, X; Bray-Ward, P; Russell, J M; Boron, W F

2001-03-16

The electroneutral Na(+)-driven Cl-HCO3 exchanger is a key mechanism for regulating intracellular pH (pH(i)) in neurons, glia, and other cells. Here we report the cloning, tissue distribution, chromosomal location, and functional characterization of the cDNA of such a transporter (NDCBE1) from human brain (GenBank accession number AF069512). NDCBE1, which encodes 1044 amino acids, is 34% identical to the mammalian anion exchanger (AE2); approximately 50% to the electrogenic Na/HCO3 cotransporter (NBCe1) from salamander, rat, and humans; approximately 73% to mammalian electroneutral Na/HCO3 cotransporters (NBCn1); 71% to mouse NCBE; and 47% to a Na(+)-driven anion exchanger (NDAE1) from Drosophila. Northern blot analysis of NDCBE1 shows a robust approximately 12-kilobase signal in all major regions of human brain and in testis, and weaker signals in kidney and ovary. This human gene (SLC4A8) maps to chromosome 12q13. When expressed in Xenopus oocytes and running in the forward direction, NDCBE1 is electroneutral and mediates increases in both pH(i) and [Na(+)](i) (monitored with microelectrodes) that require HCO3(-) and are blocked by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). The pH(i) increase also requires extracellular Na(+). The Na(+):HCO3(-) stoichiometry is 1:2. Forward-running NDCBE1 mediates a 36Cl efflux that requires extracellular Na(+) and HCO3(-) and is blocked by DIDS. Running in reverse, NDCBE1 requires extracellular Cl(-). Thus, NDCBE1 encodes a human, electroneutral Na(+)-driven Cl-HCO3 exchanger.

East of the Andes: The genetic profile of the Peruvian Amazon populations.

PubMed

Di Corcia, T; Sanchez Mellado, C; Davila Francia, T J; Ferri, G; Sarno, S; Luiselli, D; Rickards, O

2017-06-01

Assuming that the differences between the Andes and the Amazon rainforest at environmental and historical levels have influenced the distribution patterns of genes, languages, and cultures, the maternal and paternal genetic reconstruction of the Peruvian Amazon populations was used to test the relationships within and between these two extreme environments. We analyzed four Peruvian Amazon communities (Ashaninka, Huambisa, Cashibo, and Shipibo) for both Y chromosome (17 STRs and 8 SNPs) and mtDNA data (control region sequences, two diagnostic sites of the coding region, and one INDEL), and we studied their variability against the rest of South America. We detected a high degree of genetic diversity in the Peruvian Amazon people, both for mtDNA than for Y chromosome, excepting for Cashibo people, who seem to have had no exchanges with their neighbors, in contrast with the others communities. The genetic structure follows the divide between the Andes and the Amazon, but we found a certain degree of gene flow between these two environments, as particularly emerged with the Y chromosome descent cluster's (DCs) analysis. The Peruvian Amazon is home to an array of populations with differential rates of genetic exchanges with their neighbors and with the Andean people, depending on their peculiar demographic histories. We highlighted some successful Y chromosome lineages expansions originated in Peru during the pre-Columbian history which involved both Andeans and Amazon Arawak people, showing that at least a part of the Amazon rainforest did not remain isolated from those exchanges. © 2017 Wiley Periodicals, Inc.

EVIDENCE FOR THE CHROMOSOMAL REPLICONS AS UNITS OF SISTER CHROMATID EXCHANGES

EPA Science Inventory

Current hypotheses of sister chromatid exchange (SCE) formation postulate that sites of SCE induction are associated with active replicons or replicon clusters. We have applied the FCC-SCD technique to in vivo studies of mouse bone marrow cells that have been treated with cycloph...

Butterfly genome reveals promiscuous exchange of mimicry adaptations among species

PubMed Central

Dasmahapatra, Kanchon K; Walters, James R.; Briscoe, Adriana D.; Davey, John W.; Whibley, Annabel; Nadeau, Nicola J.; Zimin, Aleksey V.; Hughes, Daniel S. T.; Ferguson, Laura C.; Martin, Simon H.; Salazar, Camilo; Lewis, James J.; Adler, Sebastian; Ahn, Seung-Joon; Baker, Dean A.; Baxter, Simon W.; Chamberlain, Nicola L.; Chauhan, Ritika; Counterman, Brian A.; Dalmay, Tamas; Gilbert, Lawrence E.; Gordon, Karl; Heckel, David G.; Hines, Heather M.; Hoff, Katharina J.; Holland, Peter W.H.; Jacquin-Joly, Emmanuelle; Jiggins, Francis M.; Jones, Robert T.; Kapan, Durrell D.; Kersey, Paul; Lamas, Gerardo; Lawson, Daniel; Mapleson, Daniel; Maroja, Luana S.; Martin, Arnaud; Moxon, Simon; Palmer, William J.; Papa, Riccardo; Papanicolaou, Alexie; Pauchet, Yannick; Ray, David A.; Rosser, Neil; Salzberg, Steven L.; Supple, Megan A.; Surridge, Alison; Tenger-Trolander, Ayse; Vogel, Heiko; Wilkinson, Paul A.; Wilson, Derek; Yorke, James A.; Yuan, Furong; Balmuth, Alexi L.; Eland, Cathlene; Gharbi, Karim; Thomson, Marian; Gibbs, Richard A.; Han, Yi; Jayaseelan, Joy C.; Kovar, Christie; Mathew, Tittu; Muzny, Donna M.; Ongeri, Fiona; Pu, Ling-Ling; Qu, Jiaxin; Thornton, Rebecca L.; Worley, Kim C.; Wu, Yuan-Qing; Linares, Mauricio; Blaxter, Mark L.; Constant, Richard H. ffrench; Joron, Mathieu; Kronforst, Marcus R.; Mullen, Sean P.; Reed, Robert D.; Scherer, Steven E.; Richards, Stephen; Mallet, James; McMillan, W. Owen; Jiggins, Chris D.

2012-01-01

The evolutionary importance of hybridization and introgression has long been debated1. We used genomic tools to investigate introgression in Heliconius, a rapidly radiating genus of neotropical butterflies widely used in studies of ecology, behaviour, mimicry and speciation2-5 . We sequenced the genome of Heliconius melpomene and compared it with other taxa to investigate chromosomal evolution in Lepidoptera and gene flow among multiple Heliconius species and races. Among 12,657 predicted genes for Heliconius, biologically important expansions of families of chemosensory and Hox genes are particularly noteworthy. Chromosomal organisation has remained broadly conserved since the Cretaceous, when butterflies split from the silkmoth lineage. Using genomic resequencing, we show hybrid exchange of genes between three co-mimics, H. melpomene, H. timareta, and H. elevatus, especially at two genomic regions that control mimicry pattern. Closely related Heliconius species clearly exchange protective colour pattern genes promiscuously, implying a major role for hybridization in adaptive radiation. PMID:22722851

mBAND analysis for high- and low-LET radiation-induced chromosome aberrations: a review.

PubMed

Hada, Megumi; Wu, Honglu; Cucinotta, Francis A

2011-06-03

During long-term space travel or cancer therapy, humans are exposed to high linear energy transfer (LET) energetic heavy ions. High-LET radiation is much more effective than low-LET radiation 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, and cytogenetic damage can be utilized as a biomarker for radiation insults. Epidemiological data, mainly from survivors of the atomic bomb detonations in Japan, have enabled risk estimation from low-LET radiation exposures. The identification of a cytogenetic signature that distinguishes high- from low-LET exposure remains a long-term goal in radiobiology. Recently developed fluorescence in situ hybridization (FISH)-painting methodologies have revealed unique endpoints related to radiation quality. Heavy-ions induce a high fraction of complex-type exchanges, and possibly unique chromosome rearrangements. This review will concentrate on recent data obtained with multicolor banding in situ hybridization (mBAND) methods in mammalian cells exposed to low- and high-LET radiations. Chromosome analysis with mBAND technique allows detection of both inter- and intrachromosomal exchanges, and also distribution of the breakpoints of aberrations. 2011 Elsevier B.V. All rights reserved.

Complex chromatid-isochromatid exchanges following irradiation with heavy ions?

PubMed

Loucas, B D; Eberle, R L; Durante, M; Cornforth, M N

2004-01-01

We describe a peculiar and relatively rare type of chromosomal rearrangement induced in human peripheral lymphocytes that were ostensibly irradiated in G(0) phase of the cell cycle by accelerated heavy ions, and which, to the best of our knowledge, have not been previously described. The novel rearrangements which were detected using mFISH following exposure to 500 MeV/nucleon and 5 GeV/n 56Fe particles, but were not induced by either 137Cs gamma rays or 238Pu alpha particles, can alternatively be described as either complex chromatid-isochromatid or complex chromatid-chromosome exchanges. Different mechanisms potentially responsible for their formation are discussed. Copyright 2003 S. Karger AG, Basel

Lack of Spontaneous Sister Chromatid Exchanges in Somatic Cells of DROSOPHILA MELANOGASTER

PubMed Central

Gatti, M.; Santini, G.; Pimpinelli, S.; Olivieri, G.

1979-01-01

Neural ganglia of wild type third-instar larvae of Drosophila melanogaster were incubated for 13 hours at various concentrations of BUdR (1, 3, 9, 27 µg/ml). Metaphases were collected with colchicine, stained with Hoechst 33258, and scored under a fluorescence microscope. Metaphases in which the sister chromatids were clearly differentiated were scored for the presence of sister-chromatid exchanges (SCEs). At the lowest concentration of BUdR (1 µg/ml), no SCEs were observed in either male or female neuroblasts. The SCEs were found at the higher concentrations of BUdR (3, 9 and 27 µg/ml) and with a greater frequency in females than in males. Therefore SCEs are not a spontaneous phenomenon in D. melanogaster, but are induced by BUdR incorporated in the DNA. A striking nonrandomness was found in the distribution of SCEs along the chromosomes. More than a third of the SCEs were clustered in the junctions between euchromatin and heterochromatin. The remaining SCEs were preferentially localized within the heterochromatic regions of the X chromosome and the autosomes and primarily on the entirely heterochromatic Y chromosome.—In order to find an alternative way of measuring the frequency of SCEs in Drosophila neuroblasts, the occurrence of double dicentric rings was studied in two stocks carrying monocentric ring-X chromosomes. One ring chromosome, C(1)TR 94–2, shows a rate of dicentric ring formation corresponding to the frequency of SCEs observed in the BUdR-labelled rod chromosomes. The other ring studied, R(1)2, exhibits a frequency of SCEs higher than that observed with both C(1)TR 94–2 and rod chromosomes. PMID:109350

Natural Genetic Transformation Generates a Population of Merodiploids in Streptococcus pneumoniae

PubMed Central

Zomer, Aldert; Bootsma, Hester J.; Prudhomme, Marc; Granadel, Chantal; Hermans, Peter W. M.; Polard, Patrice; Martin, Bernard; Claverys, Jean-Pierre

2013-01-01

Partial duplication of genetic material is prevalent in eukaryotes and provides potential for evolution of new traits. Prokaryotes, which are generally haploid in nature, can evolve new genes by partial chromosome duplication, known as merodiploidy. Little is known about merodiploid formation during genetic exchange processes, although merodiploids have been serendipitously observed in early studies of bacterial transformation. Natural bacterial transformation involves internalization of exogenous donor DNA and its subsequent integration into the recipient genome by homology. It contributes to the remarkable plasticity of the human pathogen Streptococcus pneumoniae through intra and interspecies genetic exchange. We report that lethal cassette transformation produced merodiploids possessing both intact and cassette-inactivated copies of the essential target gene, bordered by repeats (R) corresponding to incomplete copies of IS861. We show that merodiploidy is transiently stimulated by transformation, and only requires uptake of a ∼3-kb DNA fragment partly repeated in the chromosome. We propose and validate a model for merodiploid formation, providing evidence that tandem-duplication (TD) formation involves unequal crossing-over resulting from alternative pairing and interchromatid integration of R. This unequal crossing-over produces a chromosome dimer, resolution of which generates a chromosome with the TD and an abortive chromosome lacking the duplicated region. We document occurrence of TDs ranging from ∼100 to ∼900 kb in size at various chromosomal locations, including by self-transformation (transformation with recipient chromosomal DNA). We show that self-transformation produces a population containing many different merodiploid cells. Merodiploidy provides opportunities for evolution of new genetic traits via alteration of duplicated genes, unrestricted by functional selective pressure. Transient stimulation of a varied population of merodiploids by transformation, which can be triggered by stresses such as antibiotic treatment in S. pneumoniae, reinforces the plasticity potential of this bacterium and transformable species generally. PMID:24086154

mBAND analysis of chromosome aberrations in human epithelial cells induced by gamma-rays and secondary neutrons of low dose rate.

PubMed

Hada, M; Gersey, B; Saganti, P B; Wilkins, R; Cucinotta, F A; Wu, H

2010-08-14

Human risks from chronic exposures to both low- and high-LET radiation are of intensive research interest in recent years. In the present study, human epithelial cells were exposed in vitro to gamma-rays at a dose rate of 17 mGy/h or secondary neutrons of 25 mGy/h. The secondary neutrons have a broad energy spectrum that simulates the Earth's atmosphere at high altitude, as well as the environment inside spacecrafts like the Russian MIR station and the International Space Station (ISS). Chromosome aberrations in the exposed cells were analyzed using the multicolor banding in situ hybridization (mBAND) technique with chromosome 3 painted in 23 colored bands that allows identification of both inter- and intrachromosome exchanges including inversions. Comparison of present dose responses between gamma-rays and neutron irradiations for the fraction of cells with damaged chromosome 3 yielded a relative biological effectiveness (RBE) value of 26+/-4 for the secondary neutrons. Our results also revealed that secondary neutrons of low dose rate induced a higher fraction of intrachromosome exchanges than gamma-rays, but the fractions of inversions observed between these two radiation types were indistinguishable. Similar to the previous findings after acute radiation exposures, most of the inversions observed in the present study were accompanied by other aberrations. The fractions of complex type aberrations and of unrejoined chromosomal breakages were also found to be higher in the neutron-exposed cells than after gamma-rays. We further analyzed the location of the breaks involved in chromosome aberrations along chromosome 3, and observed hot spots after gamma-ray, but not neutron, exposures.

Natural genetic transformation generates a population of merodiploids in Streptococcus pneumoniae.

PubMed

Johnston, Calum; Caymaris, Stéphanie; Zomer, Aldert; Bootsma, Hester J; Prudhomme, Marc; Granadel, Chantal; Hermans, Peter W M; Polard, Patrice; Martin, Bernard; Claverys, Jean-Pierre

2013-01-01

Partial duplication of genetic material is prevalent in eukaryotes and provides potential for evolution of new traits. Prokaryotes, which are generally haploid in nature, can evolve new genes by partial chromosome duplication, known as merodiploidy. Little is known about merodiploid formation during genetic exchange processes, although merodiploids have been serendipitously observed in early studies of bacterial transformation. Natural bacterial transformation involves internalization of exogenous donor DNA and its subsequent integration into the recipient genome by homology. It contributes to the remarkable plasticity of the human pathogen Streptococcus pneumoniae through intra and interspecies genetic exchange. We report that lethal cassette transformation produced merodiploids possessing both intact and cassette-inactivated copies of the essential target gene, bordered by repeats (R) corresponding to incomplete copies of IS861. We show that merodiploidy is transiently stimulated by transformation, and only requires uptake of a ~3-kb DNA fragment partly repeated in the chromosome. We propose and validate a model for merodiploid formation, providing evidence that tandem-duplication (TD) formation involves unequal crossing-over resulting from alternative pairing and interchromatid integration of R. This unequal crossing-over produces a chromosome dimer, resolution of which generates a chromosome with the TD and an abortive chromosome lacking the duplicated region. We document occurrence of TDs ranging from ~100 to ~900 kb in size at various chromosomal locations, including by self-transformation (transformation with recipient chromosomal DNA). We show that self-transformation produces a population containing many different merodiploid cells. Merodiploidy provides opportunities for evolution of new genetic traits via alteration of duplicated genes, unrestricted by functional selective pressure. Transient stimulation of a varied population of merodiploids by transformation, which can be triggered by stresses such as antibiotic treatment in S. pneumoniae, reinforces the plasticity potential of this bacterium and transformable species generally.

Introgression in the Drosophila subobscura--D. Madeirensis sister species: evidence of gene flow in nuclear genes despite mitochondrial differentiation.

PubMed

Herrig, Danielle K; Modrick, Alec J; Brud, Evgeny; Llopart, Ana

2014-03-01

Species hybridization, and thus the potential for gene flow, was once viewed as reproductive mistake. However, recent analysis based on large datasets and newly developed models suggest that gene exchange is not as rare as originally suspected. To investigate the history and speciation of the closely related species Drosophila subobscura, D. madeirensis, and D. guanche, we obtained polymorphism and divergence data for 26 regions throughout the genome, including the Y chromosome and mitochondrial DNA. We found that the D. subobscura X/autosome ratio of silent nucleotide diversity is significantly smaller than the 0.75 expected under neutrality. This pattern, if held genomewide, may reflect a faster accumulation of beneficial mutations on the X chromosome than on autosomes. We also detected evidence of gene flow in autosomal regions, while sex chromosomes remain distinct. This is consistent with the large X effect on hybrid male sterility seen in this system and the presence of two X chromosome inversions fixed between species. Overall, our data conform to chromosomal speciation models in which rearrangements are proposed to serve as gene flow barriers. Contrary to other observations in Drosophila, the mitochondrial genome appears resilient to gene flow in the presence of nuclear exchange. © 2013 The Authors. Evolution published by Wiley Periodicals, Inc. on behalf of The Society for the Study of Evolution.

Genotoxic assessment in peripheral blood lymphocytes of post-polio individuals using sister chromatid exchange analysis and micronucleus assay.

PubMed

Bhattacharya, Saurabh Kumar; Saraswathy, Radha; Sivakumar, E

2011-07-01

Environmental pollution is a complex issue because of the diversity of anthropogenic agents, both chemical and physical, that have been detected and catalogued. The consequences to biota from exposure to genotoxic agents present an additional problem because of the potential for these agents to produce adverse change at the cellular and organism levels. Past studies in virus have focused on structural damage to the DNA of environmental species that may occur after exposure to genotoxic agents and the use of this information to document exposure and to monitor remediation. In an effort to predict effects at the population, community and ecosystem levels, in the present study, we attempt to characterize damage occurring through genotoxic agents like 5-bromo-2-deoxyuridine, BrdU, using sister chromatid exchange technique and the formation of micronuclei (MN) in the peripheral lymphocytes of the post-polio syndrome sequelae affected by poliovirus. Analysis of structural chromosomal aberrations (CAs) and involvement of the specific chromosome break were pursued in this study. They revealed a significantly higher incidence of CAs (chromatid and chromosome breaks) in patients compared with controls, where the specific chromosome break has emerged as specific. Also, the maximum numbers of breaks were found to be in chromosome 1 at the position 1p36.1. The results also suggest a correlation between CAs and content of MN.

Meiotic Crossover Control by Concerted Action of Rad51-Dmc1 in Homolog Template Bias and Robust Homeostatic Regulation

PubMed Central

Huang, Chu-Chun; Grubb, Jennifer; Thacker, Drew; Lee, Chih-Ying; Dresser, Michael E.; Hunter, Neil; Bishop, Douglas K.

2013-01-01

During meiosis, repair of programmed DNA double-strand breaks (DSBs) by recombination promotes pairing of homologous chromosomes and their connection by crossovers. Two DNA strand-exchange proteins, Rad51 and Dmc1, are required for meiotic recombination in many organisms. Studies in budding yeast imply that Rad51 acts to regulate Dmc1's strand exchange activity, while its own exchange activity is inhibited. However, in a dmc1 mutant, elimination of inhibitory factor, Hed1, activates Rad51's strand exchange activity and results in high levels of recombination without participation of Dmc1. Here we show that Rad51-mediated meiotic recombination is not subject to regulatory processes associated with high-fidelity chromosome segregation. These include homolog bias, a process that directs strand exchange between homologs rather than sister chromatids. Furthermore, activation of Rad51 does not effectively substitute for Dmc1's chromosome pairing activity, nor does it ensure formation of the obligate crossovers required for accurate homolog segregation. We further show that Dmc1's dominance in promoting strand exchange between homologs involves repression of Rad51's strand-exchange activity. This function of Dmc1 is independent of Hed1, but requires the meiotic kinase, Mek1. Hed1 makes a relatively minor contribution to homolog bias, but nonetheless this is important for normal morphogenesis of synaptonemal complexes and efficient crossing-over especially when DSB numbers are decreased. Super-resolution microscopy shows that Dmc1 also acts to organize discrete complexes of a Mek1 partner protein, Red1, into clusters along lateral elements of synaptonemal complexes; this activity may also contribute to homolog bias. Finally, we show that when interhomolog bias is defective, recombination is buffered by two feedback processes, one that increases the fraction of events that yields crossovers, and a second that we propose involves additional DSB formation in response to defective homolog interactions. Thus, robust crossover homeostasis is conferred by integrated regulation at initiation, strand-exchange and maturation steps of meiotic recombination. PMID:24367271

Effects of Inversions on Within- and Between-Species Recombination and Divergence

PubMed Central

Stevison, Laurie S.; Hoehn, Kenneth B.; Noor, Mohamed A. F.

2011-01-01

Chromosomal inversions disrupt recombination in heterozygotes by both reducing crossing-over within inverted regions and increasing it elsewhere in the genome. The reduction of recombination in inverted regions facilitates the maintenance of hybridizing species, as outlined by various models of chromosomal speciation. We present a comprehensive comparison of the effects of inversions on recombination rates and on nucleotide divergence. Within an inversion differentiating Drosophila pseudoobscura and Drosophila persimilis, we detected one double recombinant among 9,739 progeny from F1 hybrids screened, consistent with published double-crossover frequencies observed within species. Despite similar rates of exchange within and between species, we found no sequence-based evidence of ongoing gene exchange between species within this inversion, but significant exchange was inferred within species. We also observed greater differentiation at regions near inversion breakpoints between species versus within species. Moreover, we observed strong “interchromosomal effect” (higher recombination in inversion heterozygotes between species) with up to 9-fold higher recombination rates along collinear segments of chromosome two in hybrids. Further, we observed that regions most susceptible to changes in recombination rates corresponded to regions with lower recombination rates in homokaryotypes. Finally, we showed that interspecies nucleotide divergence is lower in regions with greater increases in recombination rate, potentially resulting from greater interspecies exchange. Overall, we have identified several similarities and differences between inversions segregating within versus between species in their effects on recombination and divergence. We conclude that these differences are most likely due to lower frequency of heterokaryotypes and to fitness consequences from the accumulation of various incompatibilities between species. Additionally, we have identified possible effects of inversions on interspecies gene exchange that had not been considered previously. PMID:21828374

Cytogenic studies of blood (experiment M111)

NASA Technical Reports Server (NTRS)

Lockhart, L. H.

1974-01-01

The Skylab M111 experiment was a continuation of the preflight and postflight chromosomal analyses of the flight crews that have been performed since the Gemini 3 mission. The experiment was designed to determine whether some space flight parameter produces cytogenetic effects in human cells and to provide biological radiation dosimetric capability in the event of significant radiation exposure to a flight crew. On each of the Skylab flights, blood lymphocytes for analysis of chromosomes for structural defects were obtained from each of the prime crewmembers and from a ground-based control group before and after flight. Two types of defects were recorded. The minor defects included the following aberrations: chromatid fragments, chromosome fragments, and deletions. Structural rearrangements such as dicentrics, exchanges, ring chromosomes, and translocations were photographed, and the cells were karyotyped to delineate, when possible, the chromosome or chromosomes involved in the rearrangement. Result seems to indicate that the flight itself was not a major contributing factor.

Direct visualization reveals kinetics of meiotic chromosome synapsis

DOE PAGES

Rog, Ofer; Dernburg, Abby  F.

2015-03-17

The synaptonemal complex (SC) is a conserved protein complex that stabilizes interactions along homologous chromosomes (homologs) during meiosis. The SC regulates genetic exchanges between homologs, thereby enabling reductional division and the production of haploid gametes. Here, we directly observe SC assembly (synapsis) by optimizing methods for long-term fluorescence recording in C. elegans. We report that synapsis initiates independently on each chromosome pair at or near pairing centers—specialized regions required for homolog associations. Once initiated, the SC extends rapidly and mostly irreversibly to chromosome ends. Quantitation of SC initiation frequencies and extension rates reveals that initiation is a rate-limiting step inmore » homolog interactions. Eliminating the dynein-driven chromosome movements that accompany synapsis severely retards SC extension, revealing a new role for these conserved motions. This work provides the first opportunity to directly observe and quantify key aspects of meiotic chromosome interactions and will enable future in vivo analysis of germline processes.« less

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

Couples, Pairs, and Clusters: Mechanisms and Implications of Centromere Associations in Meiosis

PubMed Central

Obeso, David; Pezza, Roberto J; Dawson, Dean

2013-01-01

Observations from a wide range of organisms show the centromeres form associations of pairs or small groups at different stages of meiotic prophase. Little is known about the functions or mechanisms of these associations, but in many cases synaptonemal complex elements seem to play a fundamental role. Two main associations are observed: homology-independent associations very early in the meiotic program – sometimes referred to as centromere coupling, and a later association of homologous centromeres, referred to as centromere pairing or tethering. The later centromere pairing initiates during synaptonemal complex assembly, then persists after the dissolution of the synaptonemal complex. While the function of the homology-independent centromere coupling remains a mystery, centromere pairing appears to have a direct impact on the chromosome segregation fidelity of achiasmatic chromosomes. Recent work in yeast, Drosophila, and mice suggest centromere pairing is a previously unappreciated, general meiotic feature that may promote meiotic segregation fidelity of the exchange and non-exchange chromosomes. PMID:24126501

Couples, pairs, and clusters: mechanisms and implications of centromere associations in meiosis.

PubMed

Obeso, David; Pezza, Roberto J; Dawson, Dean

2014-03-01

Observations of a wide range of organisms show that the centromeres form associations of pairs or small groups at different stages of meiotic prophase. Little is known about the functions or mechanisms of these associations, but in many cases, synaptonemal complex elements seem to play a fundamental role. Two main associations are observed: homology-independent associations very early in the meiotic program-sometimes referred to as centromere coupling-and a later association of homologous centromeres, referred to as centromere pairing or tethering. The later centromere pairing initiates during synaptonemal complex assembly, then persists after the dissolution of the synaptonemal complex. While the function of the homology-independent centromere coupling remains a mystery, centromere pairing appears to have a direct impact on the chromosome segregation fidelity of achiasmatic chromosomes. Recent work in yeast, Drosophila, and mice suggest that centromere pairing is a previously unappreciated, general meiotic feature that may promote meiotic segregation fidelity of the exchange and non-exchange chromosomes.

SMC condensation centers in Bacillus subtilis are dynamic structures.

PubMed

Kleine Borgmann, Luise A K; Hummel, Hanna; Ulbrich, Maximilian H; Graumann, Peter L

2013-05-01

SMC and MukB complexes consist of a central SMC dimer and two essential binding partners, ScpA and ScpB (MukE and MukF), and are crucial for correct chromosome compaction and segregation. The complexes form two bipolar assemblies on the chromosome, one in each cell half. Using fluorescence recovery after photobleaching (FRAP), we provide evidence that the SMC complex has high exchange rates. This depends to a considerable degree on de novo protein synthesis, revealing that the bacterial SMC complex has high on and off rates for binding to the chromosome. A mutation in SMC that affects ATPase activity and results in exaggerated DNA binding in vitro causes a strong segregation defect in vivo and affects the localization of the entire SMC complex, which localizes to many more sites in the cell than under normal conditions. These data indicate that ATP turnover is important for the function of Bacillus subtilis SMC. In contrast, the centromere protein Spo0J and DNA gyrase showed much less exchange between distinct binding sites on the chromosome than that seen with SMC. Binding of Spo0J to the origin regions was rather static and remained partially conserved until the next cell cycle. Our experiments reveal that the SMC complex has a high, condensin-like turnover rate and that an alteration of the ATPase cycle affects SMC function in vivo, while several nucleoid-associated proteins feature limited or slow exchange between different sites on the nucleoid, which may be the basis for epigenetic-like phenomena observed in bacteria.

The Biological Effectiveness of Silicon Ions is Significantly Higher than Iron Ions for the Induction of Chromosome Damage in Human Lymphocytes

NASA Technical Reports Server (NTRS)

George, Kerry; Hada, Megumi; Cucinotta, F. A.

2010-01-01

Chromosome aberrations were measured in human peripheral blood lymphocytes after in vitro exposure to Si-28-ions with energies ranging from 90 to 600 MeV/u, or Fe-56-ions with energies ranging from 200 to 5,000 MeV/u. The LET of the various Fe beams in this study ranged from 145 to 440 keV/micron and the LET Si ions ranged from 48 to 158 keV/micron. Doses delivered were in the 10 to 200 cGy range. Dose response curves for chromosome exchanges in cells at first division after exposure, measured using fluorescence in situ hybridization (FISH) with whole chromosome probes, were fitted with linear or linear-quadratic functions. The relative biological effectiveness (RBE) was estimated from the initial slope of the dose response curve for chromosome damage with respect to gamma-rays. The estimates of RBE(sub max) values for total chromosome exchanges ranged from 4.4+/-0.4 to 31.5+/-2.6 for Fe ions, and 11.8+/-1.0 to 42.2+/-3.3 for Si ions. The highest RBE(sub max) value for Fe ions was obtained with the 600 Mev/u beam and 170 MeV/u beam produced the highest RBE(sub max) value for Si ions. For both ions the RBE(sub max) values increased with LET, reaching a maximum at about 180 keV/micron for Fe and about 100 keV/micron for Si, and decreased with further increase in LET.

Induction of chromosomal aberrations at fluences of less than one HZE particle per cell nucleus.

PubMed

Hada, Megumi; Chappell, Lori J; Wang, Minli; George, Kerry A; Cucinotta, Francis A

2014-10-01

The assumption of a linear dose response used to describe the biological effects of high-LET radiation is fundamental in radiation protection methodologies. We investigated the dose response for chromosomal aberrations for exposures corresponding to less than one particle traversal per cell nucleus by high-energy charged (HZE) nuclei. Human fibroblast and lymphocyte cells were irradiated with several low doses of <0.1 Gy, and several higher doses of up to 1 Gy with oxygen (77 keV/μm), silicon (99 keV/μm) or Fe (175 keV/μm), Fe (195 keV/μm) or Fe (240 keV/μm) particles. Chromosomal aberrations at first mitosis were scored using fluorescence in situ hybridization (FISH) with chromosome specific paints for chromosomes 1, 2 and 4 and DAPI staining of background chromosomes. Nonlinear regression models were used to evaluate possible linear and nonlinear dose-response models based on these data. Dose responses for simple exchanges for human fibroblasts irradiated under confluent culture conditions were best fit by nonlinear models motivated by a nontargeted effect (NTE). The best fits for dose response data for human lymphocytes irradiated in blood tubes were a linear response model for all particles. Our results suggest that simple exchanges in normal human fibroblasts have an important NTE contribution at low-particle fluence. The current and prior experimental studies provide important evidence against the linear dose response assumption used in radiation protection for HZE particles and other high-LET radiation at the relevant range of low doses.

Stacked thin layers of metaphase chromatin explain the geometry of chromosome rearrangements and banding.

PubMed

Daban, Joan-Ramon

2015-10-08

The three-dimensional organization of tightly condensed chromatin within metaphase chromosomes has been one of the most challenging problems in structural biology since the discovery of the nucleosome. This study shows that chromosome images obtained from typical banded karyotypes and from different multicolour cytogenetic analyses can be used to gain information about the internal structure of chromosomes. Chromatin bands and the connection surfaces in sister chromatid exchanges and in cancer translocations are planar and orthogonal to the chromosome axis. Chromosome stretching produces band splitting and even the thinnest bands are orthogonal and well defined, indicating that short stretches of DNA can occupy completely the chromosome cross-section. These observations impose strong physical constraints on models that attempt to explain chromatin folding in chromosomes. The thin-plate model, which consists of many stacked layers of planar chromatin perpendicular to the chromosome axis, is compatible with the observed orientation of bands, with the existence of thin bands, and with band splitting; it is also compatible with the orthogonal orientation and planar geometry of the connection surfaces in chromosome rearrangements. The results obtained provide a consistent interpretation of the chromosome structural properties that are used in clinical cytogenetics for the diagnosis of hereditary diseases and cancers.

A Rare De novo Complex Chromosomal Rearrangement (CCR) Involving Four Chromosomes in An Oligo-asthenosperm Infertile Man

PubMed Central

Asia, Saba; Vaziri Nasab, Hamed; Sabbaghian, Marjan; Kalantari, Hamid; Zari Moradi, Shabnam; Gourabi, Hamid; Mohseni Meybodi, Anahita

2014-01-01

Complex chromosomal rearrangements (CCRs) are rare events involving more than two chromosomes and over two breakpoints. They are usually associated with infertility or sub fertility in male carriers. Here we report a novel case of a CCR in a 30-year-old oligoasthenosperm man with a history of varicocelectomy, normal testes size and normal endocrinology profile referred for chromosome analysis to the Genetics unit of Royan Reproductive Biomedicine Research Center. Chromosomal analysis was performed using peripheral blood lymphocyte cultures and analyzed by GTG banding. Additional tests such as C-banding and multicolor fluorescence in situ hybridization (FISH) procedure for each of the involved chromosomes were performed to determine the patterns of the segregations. Y chromosome microdeletions in the azoospermia factor (AZF) region were analyzed with multiplex polymerase chain reaction. To identify the history and origin of this CCR, all the family members were analyzed. No micro deletion in Y chromosome was detected. The same de novo reciprocal exchange was also found in his monozygous twin brother. The other siblings and parents were normal. CCRs are associated with male infertility as a result of spermatogenic disruption due to complex meiotic configurations and the production of chromosomally abnormal sperms. These chromosomal rearrangements might have an influence on decreasing the number of sperms. PMID:24611143

Correlation between pairing initiation sites, recombination nodules and meiotic recombination in Sordaria macrospora.

PubMed

Zickler, D; Moreau, P J; Huynh, A D; Slezec, A M

1992-09-01

The decrease of meiotic exchanges (crossing over and conversion) in two mutants of Sordaria macrospora correlated strongly with a reduction of chiasmata and of both types of "recombination nodules." Serial section reconstruction electron microscopy was used to compare the synapsis pattern of meiotic prophase I in wild type and mutants. First, synapsis occurred but the number of synaptonemal complex initiation sites was reduced in both mutants. Second, this reduction was accompanied by, or resulted in, modifications of the pattern of synapsis. Genetic and synaptonemal complex maps were compared in three regions along one chromosome arm divided into well marked intervals. Reciprocal exchange frequencies and number of recombination nodules correlated in wild type in the three analyzed intervals, but disparity was found between the location of recombination nodules and exchanges in the mutants. Despite the twofold exchange decrease, sections of the genome such as the short arm of chromosome 2 and telomere regions were sheltered from nodule decrease and from pairing modifications. This indicated a certain amount of diversity in the control of these features and suggested that exchange frequency was dependent not only on the amount of effective pairing but also on the localization of the pairing sites, as revealed by the synaptonemal complex progression in the mutants.

Correlation between Pairing Initiation Sites, Recombination Nodules and Meiotic Recombination in Sordaria Macrospora

PubMed Central

Zickler, D.; Moreau, PJF.; Huynh, A. D.; Slezec, A. M.

1992-01-01

The decrease of meiotic exchanges (crossing over and conversion) in two mutants of Sordaria macrospora correlated strongly with a reduction of chiasmata and of both types of ``recombination nodules.'' Serial section reconstruction electron microscopy was used to compare the synapsis pattern of meiotic prophase I in wild type and mutants. First, synapsis occurred but the number of synaptonemal complex initiation sites was reduced in both mutants. Second, this reduction was accompanied by, or resulted in, modifications of the pattern of synapsis. Genetic and synaptonemal complex maps were compared in three regions along one chromosome arm divided into well marked intervals. Reciprocal exchange frequencies and number of recombination nodules correlated in wild type in the three analyzed intervals, but disparity was found between the location of recombination nodules and exchanges in the mutants. Despite the twofold exchange decrease, sections of the genome such as the short arm of chromosome 2 and telomere regions were sheltered from nodule decrease and from pairing modifications. This indicated a certain amount of diversity in the control of these features and suggested that exchange frequency was dependent not only on the amount of effective pairing but also on the localization of the pairing sites, as revealed by the synaptonemal complex progression in the mutants. PMID:1398050

Rex and a Suppressor of Rex Are Repeated Neomorphic Loci in the Drosophila Melanogaster Ribosomal DNA

PubMed Central

Rasooly, R. S.; Robbins, L. G.

1991-01-01

The Rex locus of Drosophila melanogaster induces a high frequency of mitotic exchange between two separated ribosomal DNA arrays on a single chromosome. The exchanges take place in the progeny of Rex mothers and occur very early, before the third mitotic division. A number of common laboratory stocks have also been found to carry dominant suppressors of Rex (Su(Rex)). Rex was mapped to the X centric heterochromatin, proximal to su(f), by genetic and molecular analysis of two spontaneous recombinants. Using deficiencies and duplications of the heterochromatin, both Rex and one Su(Rex) were shown to behave as neomorphs. Rex-induced exchange in a target chromosome bearing both Rex and Su(Rex) was then used to map these functions to the bb locus itself. Molecular analysis of the recombinants, using length variants of the ribosomal DNA intergenic spacer as genetic markers, mapped Su(Rex) and Rex within the bb locus and demonstrated that both are repeated elements. PMID:1936953

The Biological Effectiveness of Different Radiation Qualities for the Induction of Chromosome Damage in Human Lymphocytes

NASA Technical Reports Server (NTRS)

Hada, M.; George, K.; Cucinotta, F. A.

2010-01-01

Chromosome aberrations were measured in human peripheral blood lymphocytes after in vitro exposure to 28Si- ions with energies ranging from 90 to 600 MeV/u, or to 56Fe-ions with energies ranging from 200 to 5,000 MeV/u. The LET of the various Fe beams in this study ranged from 145 to 440 keV/micron and the LET of the Si ions ranged from 48 to 158 keV/ m. Doses delivered were in the 10- to 200-cGy range. Dose-response curves for chromosome exchanges in cells at first division after exposure, measured using fluorescence in situ hybridization (FISH) with whole-chromosome probes, were fitted with linear or linear-quadratic functions. The relative biological effectiveness (RBE) was estimated from the initial slope of the dose-response curve for chromosome damage with respect to -rays. The estimates of RBE(sub max) values for total chromosome exchanges ranged from 4.4+/-0.4 to 31.5+/-2.6 for Fe ions, and 11.8+/-1.0 to 42.2+/-3.3 for Si ions. The highest RBE(sub max) value for Fe ions was obtained with the 600-Mev/u beam, and the highest RBE(sub max) value for Si ions was obtained with the 170 MeV/u beam. For both ions the RBEmax values increased with LET, reaching a maximum at about 180 keV/micron for Fe and about 100 keV/ m for Si, and decreasing with further increase in LET. Additional studies for low doses 28Si-ions down to 0.02 Gy will be discussed.

Prediction of a rare chromosomal aberration simultaneously with next generation sequencing-based comprehensive chromosome screening in human preimplantation embryos for recurrent pregnancy loss.

PubMed

Lee, Yi-Xuan; Chen, Chien-Wen; Lin, Yi-Hui; Tzeng, Chii-Ruey; Chen, Chi-Huang

2018-01-01

Preimplantation genetic testing has been used widely in recent years as a part of assisted reproductive technology (ART) owing to the breakthrough development of deoxyribonucleic acid (DNA) sequencing. With the advancement of technology and increased resolution of next generation sequencing (NGS), extensive comprehensive chromosome screening along with small clinically significant deletions and duplications can possibly be performed simultaneously. Here, we present a case of rare chromosomal aberrations: 46,XY,dup(15)(q11.2q13),t(16;18)(q23;p11.2), which resulted in a normally developed adult but abnormal gametes leading to recurrent pregnancy loss (RPL). To our best knowledge, this is the first report of t(16;18) translocation with such a small exchanged segment detected by NGS platform of MiSeq system in simultaneous 24-chromosome aneuploidy screening.

Stability of chromosome aberrations in the blood lymphocytes of astronauts measured after space flight by FISH chromosome painting.

PubMed

George, K; Willingham, V; Cucinotta, F A

2005-10-01

Follow-up measurements of chromosome aberrations in the blood lymphocytes of astronauts were performed by FISH chromosome painting at various intervals from 5 months to more than 5 years after space flight and compared to preflight baseline measurements. For five of the six astronauts studied, the analysis of individual time courses for translocations revealed a temporal decline of yields with half-lives ranging from 10 to 58 months. The yield of exchanges remained unchanged for the sixth astronaut during an observation period of 5 months after flight. These results may indicate complications with the use of stable aberrations for retrospective dose reconstruction, and the differences in the decay time may reflect individual variability in risk from space radiation exposure.

Stability of chromosome aberrations in the blood lymphocytes of astronauts measured after space flight by FISH chromosome painting

NASA Technical Reports Server (NTRS)

George, K.; Willingham, V.; Cucinotta, F. A.

2005-01-01

Follow-up measurements of chromosome aberrations in the blood lymphocytes of astronauts were performed by FISH chromosome painting at various intervals from 5 months to more than 5 years after space flight and compared to preflight baseline measurements. For five of the six astronauts studied, the analysis of individual time courses for translocations revealed a temporal decline of yields with half-lives ranging from 10 to 58 months. The yield of exchanges remained unchanged for the sixth astronaut during an observation period of 5 months after flight. These results may indicate complications with the use of stable aberrations for retrospective dose reconstruction, and the differences in the decay time may reflect individual variability in risk from space radiation exposure.

Familial polyposis coli: no evidence for increased sensitivity to mitomycin C.

PubMed Central

Mazzullo, H A; Attwood, J; Delhanty, J D

1988-01-01

Spontaneous chromosome instability is well established for the dominantly inherited cancer prone condition, familial polyposis coli (FPC), but conflicting results have been obtained regarding sensitivity to mitomycin C (MMC). We have investigated cell survival in fibroblasts and the induction of sister chromatid exchanges and chromosome damage in lymphocytes and fibroblasts after MMC treatment. We can find no evidence for a differential response of FPC cells as measured by any of these parameters, although individual FPC fibroblast cultures did show an enhanced chromosomal response. Overall, the FPC mutation does not appear to result in defective DNA repair in response to MMC. PMID:2835481

Centromere pairing – tethering partner chromosomes in meiosis I

PubMed Central

Kurdzo, Emily L; Dawson, Dean S

2015-01-01

In meiosis, homologous chromosomes face the obstacle of finding, holding onto and segregating away from their partner chromosome. There is increasing evidence, in a diverse range of organisms, that centromere–centromere interactions that occur in late prophase are an important mechanism in ensuring segregation fidelity. Centromere pairing appears to initiate when homologous chromosomes synapse in meiotic prophase. Structural proteins of the synaptonemal complex have been shown to help mediate centromere pairing, but how the structure that maintains centromere pairing differs from the structure of the synaptonemal complex along the chromosomal arms remains unknown. When the synaptonemal complex proteins disassemble from the chromosome arms in late prophase, some of these synaptonemal complex components persist at the centromeres. In yeast and Drosophila these centromere-pairing behaviors promote the proper segregation of chromosome partners that have failed to become linked by chiasmata. Recent studies of mouse spermatocytes have described centromere pairing behaviors that are similar in several respects to what has been described in the fly and yeast systems. In humans, chromosomes that fail to experience crossovers in meiosis are error-prone and are a major source of aneuploidy. The finding that centromere pairing is a conserved phenomenon raises the possibility that it may play a role in promoting the segregation fidelity of non-exchange chromosome pairs in humans. PMID:25817724

Biodosimetry results from space flight Mir-18.

PubMed

Yang, T C; George, K; Johnson, A S; Durante, M; Fedorenko, B S

1997-11-01

Astronauts are classified as radiation workers due to the presence of ionizing radiation in space. For the assessment of health risks, physical dosimetry has been indispensable. However, the change of the location of dosimeters on the crew members, the variation in dose rate with location inside the spacecraft and the unknown biological effects of microgravity can introduce significant uncertainties in estimating exposure. To circumvent such uncertainty, a study on the cytogenetic effects of space radiation in human lymphocytes was proposed and conducted for Mir-18, a 115-day mission. This study used fluorescence in situ hybridization (FISH) with whole-chromosome painting probes to score chromosomal exchanges and the Giemsa staining method to determine the frequency of dicentrics. The growth kinetics of cells and sister chromatid exchanges (SCEs) were examined to ensure that chromosomal aberrations were scored in the first mitosis and were induced primarily by space radiation. Our results showed that the frequency of chromosomal aberrations increased significantly in postflight samples compared to samples drawn prior to flight, and that the frequency of SCEs was similar for both pre- and postflight samples. Based on a dose-response curve for preflight samples exposed to gamma rays, the absorbed dose received by crew members during the mission was estimated to be about 14.75 cSv. Because the absorbed dose measured by physical dosimeters is 5.2 cGy for the entire mission, the RBE is about 2.8.

Biodosimetry results from space flight Mir-18

NASA Technical Reports Server (NTRS)

Yang, T. C.; George, K.; Johnson, A. S.; Durante, M.; Fedorenko, B. S.

1997-01-01

Astronauts are classified as radiation workers due to the presence of ionizing radiation in space. For the assessment of health risks, physical dosimetry has been indispensable. However, the change of the location of dosimeters on the crew members, the variation in dose rate with location inside the spacecraft and the unknown biological effects of microgravity can introduce significant uncertainties in estimating exposure. To circumvent such uncertainty, a study on the cytogenetic effects of space radiation in human lymphocytes was proposed and conducted for Mir-18, a 115-day mission. This study used fluorescence in situ hybridization (FISH) with whole-chromosome painting probes to score chromosomal exchanges and the Giemsa staining method to determine the frequency of dicentrics. The growth kinetics of cells and sister chromatid exchanges (SCEs) were examined to ensure that chromosomal aberrations were scored in the first mitosis and were induced primarily by space radiation. Our results showed that the frequency of chromosomal aberrations increased significantly in postflight samples compared to samples drawn prior to flight, and that the frequency of SCEs was similar for both pre- and postflight samples. Based on a dose-response curve for preflight samples exposed to gamma rays, the absorbed dose received by crew members during the mission was estimated to be about 14.75 cSv. Because the absorbed dose measured by physical dosimeters is 5.2 cGy for the entire mission, the RBE is about 2.8.

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.

Comparison of chromosome aberration frequencies in pre- and post-flight astronaut lymphocytes irradiated in vitro with gamma rays

NASA Technical Reports Server (NTRS)

Wu, H.; George, K.; Willingham, V.; Cucinotta, F. A.

2001-01-01

If radiosensitivity is altered in a microgravity environment, it will affect the accuracy of assessing astronauts' risk from exposure to space radiation. To investigate the effects of space flight on radiosensitivity, we exposed a crewmember's blood to gamma rays at doses ranging from 0 to 3 Gy and analyzed chromosome aberrations in mitotic lymphocytes. The blood samples were collected 10 days prior to an 8-day Shuttle mission, the day the flight returned, and 14 days after the flight. After exposure, lymphocytes were stimulated to grow in media containing phytohaemagglutinin (PHA) and mitotic cells were harvested for chromosome analysis using a fluorescence in situ hybridization (FISH) with whole chromosome specific probes. The dose response of total exchanges showed no changes in the radiosensitivity after the mission.

The effect of space radiation on the induction of chromosome damage

NASA Technical Reports Server (NTRS)

George, K.; Wu, H.; Willingham, V.; Cucinotta, F. A.

2001-01-01

To obtain information on the cytogenetic damage caused by space radiation, chromosome exchanges in lymphocytes from crewmembers of long-term Mir missions, and a shorter duration shuttle mission, were examined using fluorescence in situ hybridization. A significant increase in chromosomal aberrations was observed after the long duration flights. The ratio of aberrations identified as complex was higher post-flight for some crewmembers, which is thought to be an indication of exposure to high-LET radiation. Ground-based studies have shown that the frequency of aberrations measured post-flight could be influenced by a mitotic delay in cells damaged by high-LET radiation and this effect could lower biological dose estimates. To counteract this effect, prematurely condensed chromosome (PCC) spreads were collected. Frequencies of aberrations in PCC were compared with those in metaphase spreads.

Homologous Recombination Repair Protects Against Particulate Chromate-induced Chromosome Instability in Chinese Hamster Cells

PubMed Central

Stackpole, Megan M.; Wise, Sandra S.; Duzevik, Eliza Grlickova; Munroe, Ray C.; Thompson, W. Douglas; Thacker, John; Thompson, Larry H.; Hinz, John M.; Wise, John Pierce

2008-01-01

Particulate hexavalent chromium [Cr(VI)] compounds are well-established human carcinogens. Cr(VI)-induced tumors are characterized by chromosomal instability (CIN); however, the mechanisms of this effect are unknown. We investigated the hypothesis that homologous recombination (HR) repair of DNA double strand breaks protect cells from Cr(VI)-induced CIN by focusing on the XRCC3 and RAD51C genes, which play an important role in cellular resistance to DNA double strand breaks. We used Chinese hamster cells defective in each HR gene (irs3 for RAD51C and irs1SF for XRCC3) and compared with their wildtype parental and cDNA-complemented controls. We found that the intracellular Cr ion levels varied among the cell lines after particulate chromate treatment. Importantly, accounting for differences in Cr ion levels, we discovered that XRCC3 and RAD51C cells treated with lead chromate had increased cytotoxicity and chromosomal aberrations, relative to wild-type and cDNA-complimented cells. We also observed the emergence of high levels of chromatid exchanges in the two mutant cell lines. For example, 1 ug/cm2 lead chromate induced 20 and 32 exchanges in XRCC3- and RAD51C-deficient cells, respectively, whereas no exchanges were detected in the wildtype and cDNA-complemented cells. These observations suggest that HR protects cells from Cr(VI)-induced CIN, consistent with the ability of particulate Cr(VI) to induce double strand breaks. PMID:17662313

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.

Analysis of Chromosomal Aberrations after Low and High Dose Rate Gamma Irradiation in ATM or NBS Suppressed Human Fibroblast Cells

NASA Technical Reports Server (NTRS)

Hada, M.; Huff, J. L.; Patel, Z.; Pluth, J. M.; George, K. A.; Cucinotta, F. A.

2009-01-01

A detailed understanding of the biological effects of heavy nuclei is needed for space radiation protection and for cancer therapy. High-LET radiation produces more complex DNA lesions that may be non-repairable or that may require additional processing steps compared to endogenous DSBs, increasing the possibility of misrepair. Interplay between radiation sensitivity, dose, and radiation quality has not been studied extensively. Previously we studied chromosome aberrations induced by low- and high- LET radiation in several cell lines deficient in ATM (ataxia telangactasia mutated; product of the gene that is mutated in ataxia telangiectasia patients) or NBS (nibrin; product of the gene mutated in the Nijmegen breakage syndrome), and gliomablastoma cells that are proficient or lacking in DNA-dependent protein kinase (DNA-PK) activity. We found that the yields of both simple and complex chromosomal aberrations were significantly increased in the DSB repair defective cells compared to normal cells. The increased aberrations observed for the ATM and NBS defective lines was due to a significantly larger quadratic dose-response term compared to normal fibroblasts for both simple and complex aberrations, while the linear dose-response term was significantly higher in NBS cells only for simple exchanges. These results point to the importance of the functions of ATM and NBS in chromatin modifications that function to facilitate correct DSB repair and minimize aberration formation. To further understand the sensitivity differences that were observed in ATM and NBS deficient cells, in this study, chromosomal aberration analysis was performed in normal lung fibroblast cells treated with KU-55933, a specific ATM kinase inhibitor, or Mirin, an MRN complex inhibitor involved in activation of ATM. We are also testing siRNA knockdown of these proteins. Normal and ATM or NBS suppressed cells were irradiated with gamma-rays and chromosomes were collected with a premature chromosome condensation (PCC) technique at the first mitosis post-irradiation. Chromosomes were analyzed using a multicolor fluorescence in-situ hybridization (mFISH) chromosome painting method. Preliminary analysis showed that chromosomal exchanges were increased in the cells treated with the specific ATM inhibitor. Possible cytogenetic signatures of acute and low dose-rate gamma irradiation in ATM or Nibrin deficient and suppressed cells will be discussed.

The ubiquitous mitochondrial creatine kinase gene maps to a conserved region on human chromosome 15q15 and mouse chromosome 2 bands F1-F3

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

Steeghs, K.; Wieringa, B.; Merkx, G.

1994-11-01

Members of the creatine kinase isoenzyme family (CKs; EC 2.7.3.2) are found in mitochondria and specialized subregions of the cytoplasm and catalyze the reversible exchange of high-energy phosphoryl between ATP and phosphocreatine. At least four functionally active genes, which encode the distinct CK subunits CKB, CKM, CKMT1 (ubiquitous), and CKMT2 (sarcomeric), and a variable number of CKB pseudogenes have been identified. Here, we report the use of a CKMT1 containing phage to map the CKMT1 gene by in situ hybridization on both human and mouse chromosomes.

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

Chromosome speciation: Humans, Drosophila, and mosquitoes

PubMed Central

Ayala, Francisco J.; Coluzzi, Mario

2005-01-01

Chromosome rearrangements (such as inversions, fusions, and fissions) may play significant roles in the speciation between parapatric (contiguous) or partly sympatric (geographically overlapping) populations. According to the “hybrid-dysfunction” model, speciation occurs because hybrids with heterozygous chromosome rearrangements produce dysfunctional gametes and thus have low reproductive fitness. Natural selection will, therefore, promote mutations that reduce the probability of intercrossing between populations carrying different rearrangements and thus promote their reproductive isolation. This model encounters a disabling difficulty: namely, how to account for the spread in a population of a chromosome rearrangement after it first arises as a mutation in a single individual. The “suppressed-recombination” model of speciation points out that chromosome rearrangements act as a genetic filter between populations. Mutations associated with the rearranged chromosomes cannot flow from one to another population, whereas genetic exchange will freely occur between colinear chromosomes. Mutations adaptive to local conditions will, therefore, accumulate differentially in the protected chromosome regions so that parapatric or partially sympatric populations will genetically differentiate, eventually evolving into different species. The speciation model of suppressed recombination has recently been tested by gene and DNA sequence comparisons between humans and chimpanzees, between Drosophila species, and between species related to Anopheles gambiae, the vector of malignant malaria in Africa. PMID:15851677

Release of Mps1 from kinetochores is crucial for timely anaphase onset.

PubMed

Jelluma, Nannette; Dansen, Tobias B; Sliedrecht, Tale; Kwiatkowski, Nicholas P; Kops, Geert J P L

2010-10-18

Mps1 kinase activity is required for proper chromosome segregation during mitosis through its involvements in microtubule-chromosome attachment error correction and the mitotic checkpoint. Mps1 dynamically exchanges on unattached kinetochores but is largely removed from kinetochores in metaphase. Here we show that Mps1 promotes its own turnover at kinetochores and that removal of Mps1 upon chromosome biorientation is a prerequisite for mitotic checkpoint silencing. Inhibition of Mps1 activity increases its half-time of recovery at unattached kinetochores and causes accumulation of Mps1 protein at these sites. Strikingly, preventing dissociation of active Mps1 from kinetochores delays anaphase onset despite normal chromosome attachment and alignment, and high interkinetochore tension. This delay is marked by continued recruitment of Mad1 and Mad2 to bioriented chromosomes and is attenuated by Mad2 depletion, indicating chronic engagement of the mitotic checkpoint in metaphase. We propose that release of Mps1 from kinetochores is essential for mitotic checkpoint silencing and a fast metaphase-to-anaphase transition.

Effects of Simultaneous Radiofrequency Radiation and Chemical Exposure of Mammalian Cells. Volume 2

DTIC Science & Technology

1988-07-01

chromosome - - - - - - -I aberrations and sister chromatid exchanges (SCE). Yao (1982) exposed rat kangaroo RH5 and RH1l6 cells to 2.45 GHz radiation, and...control was reported in chromosome aberrations. Yac (1982) investigated the cytogenetic consequences of chronic microwave exposure on rat kangaroo RH5...was said to be 280C. The cells were exposed both as conidia, which are "rather inactive metabolically ," and also after DNA replication had been

Efficiency of cytogenetic methods in detecting a chromosome rearrangement induced by ionizing radiation in a cultivated chili pepper line (Capsicum baccatum var. pendulum--Solanaceae).

PubMed

Scaldaferro, Marisel A; Grabiele, Mauro; Seijo, J Guillermo; Debat, Humberto; Romero, M Victoria; Ducasse, Daniel A; Prina, Alberto R; Moscone, Eduardo A

2014-01-01

To locate transient chromosome aberrations on a selected pepper cultivar and determine the tracing efficiency of different cytogenetic methods. Seeds from Capsicum baccatum var. pendulum cultivar 'Cayenne' were treated with an acute dose of X-rays (300 Gy) and chromosome aberrations were analysed by different cytogenetic methods [Feulgen, silver staining for nucleolus organizer regions (silver positive nucleolus organizing regions or AgNOR), fluorescent banding, fluorescence in situ hybridization (FISH) and meiotic analysis]. A rearranged chromosome carrying two nucleolus organizing regions (NOR) induced by ionizing radiation was detected in the cultivar, with the occurrence of a small reciprocal exchange between a chromosome of pair no. 1 and another chromosome of pair no. 3, both carrying active NOR in short arms and associated chromomycin A positive/diamidino-phenylindole negative (CMA+/DAPI-) heterochromatin. Meiotic analysis showed a quadrivalent configuration, confirming a reciprocal translocation between two chromosomes. The use of X-rays in Capsicum allowed us to develop and identify a pepper line with structural rearrangements between two NOR-carrying chromosomes. We postulate that all the cytological techniques employed in this research were efficient in the search for chromosome aberrations. Particularly, Feulgen and AgNOR were the most suitable in those cases of transient rearrangements, whereas fluorescent banding and FISH were appropriate for intransitive ones.

DNA Strand Exchange and RecA Homologs in Meiosis

PubMed Central

Brown, M. Scott; Bishop, Douglas K.

2015-01-01

Homology search and DNA strand–exchange reactions are central to homologous recombination in meiosis. During meiosis, these processes are regulated such that the probability of choosing a homolog chromatid as recombination partner is enhanced relative to that of choosing a sister chromatid. This regulatory process occurs as homologous chromosomes pair in preparation for assembly of the synaptonemal complex. Two strand–exchange proteins, Rad51 and Dmc1, cooperate in regulated homology search and strand exchange in most organisms. Here, we summarize studies on the properties of these two proteins and their accessory factors. In addition, we review current models for the assembly of meiotic strand–exchange complexes and the possible mechanisms through which the interhomolog bias of recombination partner choice is achieved. PMID:25475089

Chromosomal Rearrangements as Barriers to Genetic Homogenization between Archaic and Modern Humans

PubMed Central

Rogers, Rebekah L.

2015-01-01

Chromosomal rearrangements, which shuffle DNA throughout the genome, are an important source of divergence across taxa. Using a paired-end read approach with Illumina sequence data for archaic humans, I identify changes in genome structure that occurred recently in human evolution. Hundreds of rearrangements indicate genomic trafficking between the sex chromosomes and autosomes, raising the possibility of sex-specific changes. Additionally, genes adjacent to genome structure changes in Neanderthals are associated with testis-specific expression, consistent with evolutionary theory that new genes commonly form with expression in the testes. I identify one case of new-gene creation through transposition from the Y chromosome to chromosome 10 that combines the 5′-end of the testis-specific gene Fank1 with previously untranscribed sequence. This new transcript experienced copy number expansion in archaic genomes, indicating rapid genomic change. Among rearrangements identified in Neanderthals, 13% are transposition of selfish genetic elements, whereas 32% appear to be ectopic exchange between repeats. In Denisovan, the pattern is similar but numbers are significantly higher with 18% of rearrangements reflecting transposition and 40% ectopic exchange between distantly related repeats. There is an excess of divergent rearrangements relative to polymorphism in Denisovan, which might result from nonuniform rates of mutation, possibly reflecting a burst of transposable element activity in the lineage that led to Denisovan. Finally, loci containing genome structure changes show diminished rates of introgression from Neanderthals into modern humans, consistent with the hypothesis that rearrangements serve as barriers to gene flow during hybridization. Together, these results suggest that this previously unidentified source of genomic variation has important biological consequences in human evolution. PMID:26399483

Chromosome Aberration in Human Blood Lymphocytes Exposed to Energetic Protons

NASA Technical Reports Server (NTRS)

Hada, M.; George, Kerry A.; Cucinotta, F. A.

2008-01-01

During space flight, astronauts are exposed to a space radiation consisting of high-energy protons, high charge and energy (HZE) nuclei, as well as secondary particles that are generated when the primary particles penetrate the spacecraft shielding. Secondary particles have a higher LET value than primary protons and therefore expected to have a higher relative biological effectiveness (RBE). To investigate this theory, we exposed human peripheral blood lymphocytes to protons with energies of 250 MeV, 800MeV, 2 GeV, or 2.5 GeV. LET values for these protons ranged from 0.4 to 0.2 keV/micrometer. and doses ranged from 0.2 to 3 Gy. Over this energy the probability of nuclear reaction leading to secondary radiation, and the multiplicity of reaction produces such as neutrons and mesons increases substantially. The effect of aluminum and polyethylene shielding was also assessed using the 2 GeV and 2.5GeV proton beams. After exposure lymphocytes were stimulated to divide and chromosomes were collected from cells in the first G2 and metaphase cell cycle after exposure using a chemical induced premature chromosome condensation (PCC) technique. Dose response data for chromosome damage was analyzed using the fluorescence in situ hybridization (FISH) chromosome painting technique. Selected samples were also analyzed with multicolor FISH (mFISH) and multicolor banding FISH (mBAND) techniques. Data indicates that the dose response for simple-type exchanges is similar for proton and gamma exposure, whereas protons induce higher yields of complex exchanges that are LET dependent. RBE values will be presented for each proton energy, and the effects of shielding and possible cytogenetic signatures of proton exposure will be discussed.

Chromosome aberrations in human blood lymphocytes exposed to energetic protons

NASA Astrophysics Data System (ADS)

Hada, Megumi; George, Ms Kerry; Cucinotta, Francis A.

During space flight, astronauts are exposed to space radiation consisting of high-energy protons, high charge and energy (HZE) nuclei, as well as secondary particles that are generated when the primary particles penetrate the spacecraft shielding. Secondary particles have a higher LET value than primary protons and are therefore expected to have a higher relative biological effectiveness (RBE). To investigate this theory, we exposed human peripheral blood lymphocytes to protons with energies of 250 MeV, 800MeV, 2 GeV, or 2.5 GeV. LET values for these protons ranged from 0.4 to 0.2 keV/µm. and doses ranged from 0.2 to 3 Gy. Over this energy range the probability of nuclear reaction leading to secondary radiation, and the multiplicity of reaction products such as neutrons and mesons increases substantially. The effect of aluminum and polyethylene shielding was also assessed using the 2 GeV and 2.5GeV proton beams. After exposure lymphocytes were stimulated to divide and chromosomes were collected from cells in the first G2 and metaphase cell cycle after exposure using a chemical induced premature chromosome condensation (PCC) technique. Dose response data for chromosome damage was analyzed using the fluorescence in situ hybridization (FISH) chromosome painting technique. Selected samples were also analyzed with multicolor FISH (mFISH) and multicolor banding FISH (mBAND) techniques. Data indicates that the dose response for simple-type exchanges is similar for proton and gamma exposure, whereas protons induce higher yields of complex exchanges that are energy dependent. RBE values will be presented for each proton energy, and the effects of shielding and possible cytogenetic signatures of proton exposure will be discussed.

Chromosome analysis from peripheral blood lymphocytes of workers after an acute exposure to benzene.

PubMed Central

Clare, M G; Yardley-Jones, A; Maclean, A C; Dean, B J

1984-01-01

A spillage of about 1200 gallons of benzene occurred during the loading of a ship, and 10 workers on a single shift were exposed to benzene. Shortly afterwards, an assay of the urine of these individuals showed that substantial amounts of phenol were being excreted. About three months after the incident samples of venous blood were taken from 10 individuals exposed to benzene and 11 men on a comparable shift who acted as controls. The lymphocytes were stimulated to divide in short term cultures. For each subject, 200 cells at metaphase were examined for chromosome damage using 48 h cultures, and sister chromatid exchanges (SCE) were analysed from about 30 cells in their second division, using 72 h cultures. The most frequent types of aberrations in all the individuals were chromatid gaps, with occasional breaks of chromatids and chromosomes. There were few exchanges within or between the arms of chromatids or chromosomes. More cells in the control than in the exposed group showed damage, an effect that was especially noticeable for chromatid gaps. All values, however, were considered to be within a normal range. There were slightly more SCE in some of the exposed individuals than in the controls and there was a trend towards a positive association between the frequency of SCE recorded for each individual and the maximum value for the excretion of phenol in the urine on the day after the incident. There is no evidence to indicate that benzene induced any type of lasting chromosome damage in the lymphocytes of the 10 exposed workers when cells were examined about three months after the incident. PMID:6722051

Aberrant and multiaberrant (rogue) cells in peripheral lymphocytes of Hodgkin's lymphoma patients after chemotherapy.

PubMed

Ryabchenko, Nikolay I; Nasonova, Valentina A; Fesenko, Eleonora V; Kondrashova, Tatiana V; Antoschina, Margarita M; Pavlov, Vyacheslav V; Ryabikina, Natalya V

2006-10-10

We analyzed spontaneous chromosome lesions in peripheral lymphocytes cultured from Hodgkin's lymphoma (HL) patients before and after cytostatic chemotherapy. The mean aberration frequency was significantly higher in HL patients after chemotherapy (7.20+/-0.58 per 100 metaphases) than in non-treated HL patients (4.80+/-0.54), and in non-treated patients than in healthy subjects (2.12+/-0.13). In lymphocytes of HL patients, who received chemotherapy, we found, in addition to ordinary aberrant cells, a large number of multiaberrant (or rogue) cells, i.e. metaphases carrying multiple (at least four) chromosome-type exchange aberrations. Rogue cells were found in 15 out of 18 chemotherapeutically treated HL patients (in total, 60 rogue cells per 5,568 scored cells), whereas in 30 non-treated patients only 1 rogue cell was found (per 4,988 scored cells). No correlation was found between the yield of rogue cells and the aberration frequency in ordinary aberrant cells. Aberration spectra (ratios of chromatid- to chromosome-type aberrations and of breaks to exchanges) were essentially different in ordinary aberrant and multiaberrant cells. These data, as well as analysis of cellular distributions of aberrations, implied independent induction of chromosome damage in ordinary aberrant and rogue cells. Analysis of aberration patterns in diploid and polyploid rogue metaphases belonging to the first, second, and third in vitro division indicated that rogue cells could be formed both in vivo and in vitro, and could survive at least two rounds of in vitro replication, given blocked chromosome segregation. These results suggested that formation of rogue cells, unlike ordinary aberrant cells, was triggered by events other than direct DNA and/or chromosome lesions. A hypothesis regarding disrupted apoptosis as a candidate mechanism for rogue cell formation seems to be most suitable for interpretation of our data. Cultured lymphocytes of chemotherapeutically treated HL patients may represent a model system for further examination of the multiaberrancy phenomenon.

The Biological Effectiveness of Different Radiation Qualities for the Induction of Chromosome Damage in Human Lymphocytes

NASA Technical Reports Server (NTRS)

Hada, M.; George, Kerry; Cucinotta, F. A.

2011-01-01

Chromosome aberrations were measured in human peripheral blood lymphocytes after in vitro exposure to Si-28-ions with energies ranging from 90 to 600 MeV/u, Ti-48-ions with energies ranging from 240 to 1000 MeV/u, or to Fe-56-ions with energies ranging from 200 to 5,000 MeV/u. The LET of the various Si beams in this study ranged from 48 to 158 keV/ m, the LET of the Ti ions ranged from 107 to 240 keV/micron, and the LET of the Fe-ions ranged from 145 to 440 keV/ m. Doses delivered were in the 10- to 200-cGy range. Dose-response curves for chromosome exchanges in cells at first division after exposure, measured using fluorescence in situ hybridization (FISH) with whole-chromosome probes, were fitted with linear or linear-quadratic functions. The relative biological effectiveness (RBE) was estimated from the initial slope of the dose-response curve for chromosome damage with respect to gamma-rays. The estimates of RBEmax values for total chromosome exchanges ranged from 4.4+/-0.4 to 31.5+/-2.6 for Fe ions, 21.4+/-1.7 to 28.3+/-2.4 for Ti ions, and 11.8+/-1.0 to 42.2+/-3.3 for Si ions. The highest RBEmax value for Fe ions was obtained with the 600 MeV/u beam, the highest RBEmax value for Ti ions was obtained 1000 MeV/u beam, and the highest RBEmax value for Si ions was obtained with the 170 MeV/u beam. For Si and Fe ions the RBEmax values increased with LET, reaching a maximum at about 180 keV/micron for Fe and about 100 keV/micron for Si, and decreasing with further increase in LET. Additional studies for low doses Si-28-ions down to 0.02 Gy will be discussed.

Induction of Chromosomal Aberrations at Fluences of Less Than One HZE Particle per Cell Nucleus

NASA Technical Reports Server (NTRS)

Hada, Megumi; Chappell, Lori J.; Wang, Minli; George, Kerry A.; Cucinotta, Francis A.

2014-01-01

The assumption of a linear dose response used to describe the biological effects of high LET radiation is fundamental in radiation protection methodologies. We investigated the dose response for chromosomal aberrations for exposures corresponding to less than one particle traversal per cell nucleus by high energy and charge (HZE) nuclei. Human fibroblast and lymphocyte cells where irradiated with several low doses of <0.1 Gy, and several higher doses of up to 1 Gy with O (77 keV/ (long-s)m), Si (99 keV/ (long-s)m), Fe (175 keV/ (long-s)m), Fe (195 keV/ (long-s)m) or Fe (240 keV/ (long-s)m) particles. Chromosomal aberrations at first mitosis were scored using fluorescence in situ hybridization (FISH) with chromosome specific paints for chromosomes 1, 2 and 4 and DAPI staining of background chromosomes. Non-linear regression models were used to evaluate possible linear and non-linear dose response models based on these data. Dose responses for simple exchanges for human fibroblast irradiated under confluent culture conditions were best fit by non-linear models motivated by a non-targeted effect (NTE). Best fits for the dose response data for human lymphocytes irradiated in blood tubes were a NTE model for O and a linear response model fit best for Si and Fe particles. Additional evidence for NTE were found in low dose experiments measuring gamma-H2AX foci, a marker of double strand breaks (DSB), and split-dose experiments with human fibroblasts. Our results suggest that simple exchanges in normal human fibroblasts have an important NTE contribution at low particle fluence. The current and prior experimental studies provide important evidence against the linear dose response assumption used in radiation protection for HZE particles and other high LET radiation at the relevant range of low doses.

Chromosome aberration analysis in peripheral lymphocytes of Gulf War and Balkans War veterans.

PubMed

Schröder, H; Heimers, A; Frentzel-Beyme, R; Schott, A; Hoffmann, W

2003-01-01

Chromosome aberrations and sister chromatid exchanges (SCEs) were determined in standard peripheral lymphocyte metaphase preparations of 13 British Gulf War veterans, two veterans of the recent war in the Balkans and one veteran of both wars. All 16 volunteers suspect exposures to depleted uranium (DU) while deployed at the two different theatres of war in 1990 and later on. The Bremen laboratory control served as a reference in this study. Compared with this control there was a statistically significant increase in the frequency of dicentric chromosomes (dic) and centric ring chromosomes (cR) in the veterans' group. indicating a previous exposure to ionising radiation. The statistically significant overdispersion of die and cR indicates non-uniform irradiation as would be expected after non-uniform exposure and/or exposure to radiation with a high linear energy transfer (LET). The frequency of SCEs was decreased when compared with the laboratory control.

Interphase Chromosome Conformation and Chromatin-chromatin Interactions in Human Epithelial Cells Cultured Under Different Gravity Conditions

NASA Technical Reports Server (NTRS)

Zhang, Ye; Hada, Megumi; Wu, Honglu

2014-01-01

On a multi-mega base pair scale of the DNA, the arrangement of chromatin is non-random. In M10 epithelial cells, both telomere regions tend to be located towards the exterior of the chromosome domain, whereas the rest p-arm of the chromatin region towards the interior. In contrast, most of the q-arm of the chromatin is found in the peripheral of the domain. In lymphocytes, the p-arm chromatin regions towards the interior in close proximity with each other, whereas two q-arm regions are nearness in space. It indicates that G0 lymphocytes may lack secondary 3D chromatin folding. There chromatin folding patterns are consistent with our previous finding of non-random distribution of intra-chromosomal exchanges. In simulated microgravity conditions, the chromosome conformation may be altered and new regions in close proximity, especially to region 2 are suggested.

Localization and characterization of X chromosome inversion breakpoints separating Drosophila mojavensis and Drosophila arizonae.

PubMed

Cirulli, Elizabeth T; Noor, Mohamed A F

2007-01-01

Ectopic exchange between transposable elements or other repetitive sequences along a chromosome can produce chromosomal inversions. As a result, genome sequence studies typically find sequence similarity between corresponding inversion breakpoint regions. Here, we identify and investigate the breakpoint regions of the X chromosome inversion distinguishing Drosophila mojavensis and Drosophila arizonae. We localize one inversion breakpoint to 13.7 kb and localize the other to a 1-Mb interval. Using this localization and assuming microsynteny between Drosophila melanogaster and D. arizonae, we pinpoint likely positions of the inversion breakpoints to windows of less than 3000 bp. These breakpoints define the size of the inversion to approximately 11 Mb. However, in contrast to many other studies, we fail to find significant sequence similarity between the 2 breakpoint regions. The localization of these inversion breakpoints will facilitate future genetic and molecular evolutionary studies in this species group, an emerging model system for ecological genetics.

RecA: Regulation and Mechanism of a Molecular Search Engine.

PubMed

Bell, Jason C; Kowalczykowski, Stephen C

2016-06-01

Homologous recombination maintains genomic integrity by repairing broken chromosomes. The broken chromosome is partially resected to produce single-stranded DNA (ssDNA) that is used to search for homologous double-stranded DNA (dsDNA). This homology driven 'search and rescue' is catalyzed by a class of DNA strand exchange proteins that are defined in relation to Escherichia coli RecA, which forms a filament on ssDNA. Here, we review the regulation of RecA filament assembly and the mechanism by which RecA quickly and efficiently searches for and identifies a unique homologous sequence among a vast excess of heterologous DNA. Given that RecA is the prototypic DNA strand exchange protein, its behavior affords insight into the actions of eukaryotic RAD51 orthologs and their regulators, BRCA2 and other tumor suppressors. Copyright © 2016 Elsevier Ltd. All rights reserved.

The Molecular Structure of Te146 and Its Derivatives in Drosophila Melanogaster

PubMed Central

Lovering, R.; Harden, N.; Ashburner, M.

1991-01-01

TE146 is a giant transposon of Drosophila melanogaster. It carries two copies of the white and roughest genes, normally found on the X chromosome. The structure of this transposon has been studied at the molecular level. TE146 may transpose to new chromosome positions, excise and be lost from the genome or undergo internal rearrangements. The termini of TE146 are foldback DNA elements (FB); the transposon also carries two internal FB elements. Loss or internal rearrangement of TE146 involves recombination between different FB elements. These events have been mapped molecularly, by taking advantage of the fact that the FB sequences are composed largely of a regular 155-bp repeat sequence that is cut by the restriction enzyme TaqI, and are shown to be nonrandom. We suggest that these FB-FB exchange events occur by mitotic sister-chromatid exchange in the premeiotic germ line. PMID:1649070

Dissecting the telomere-inner nuclear membrane interface formed in meiosis.

PubMed

Pendlebury, Devon F; Fujiwara, Yasuhiro; Tesmer, Valerie M; Smith, Eric M; Shibuya, Hiroki; Watanabe, Yoshinori; Nandakumar, Jayakrishnan

2017-12-01

Tethering telomeres to the inner nuclear membrane (INM) allows homologous chromosome pairing during meiosis. The meiosis-specific protein TERB1 binds the telomeric protein TRF1 to establish telomere-INM connectivity and is essential for mouse fertility. Here we solve the structure of the human TRF1-TERB1 interface to reveal the structural basis for telomere-INM linkage. Disruption of this interface abrogates binding and compromises telomere-INM attachment in mice. An embedded CDK-phosphorylation site within the TRF1-binding region of TERB1 provides a mechanism for cap exchange, a late-pachytene phenomenon involving the dissociation of the TRF1-TERB1 complex. Indeed, further strengthening this interaction interferes with cap exchange. Finally, our biochemical analysis implicates distinct complexes for telomere-INM tethering and chromosome-end protection during meiosis. Our studies unravel the structure, stoichiometry, and physiological implications underlying telomere-INM tethering, thereby providing unprecedented insights into the unique function of telomeres in meiosis.

Plant centromere organization: a dynamic structure with conserved functions.

PubMed

Ma, Jianxin; Wing, Rod A; Bennetzen, Jeffrey L; Jackson, Scott A

2007-03-01

Although the structural features of centromeres from most multicellular eukaryotes remain to be characterized, recent analyses of the complete sequences of two centromeric regions of rice, together with data from Arabidopsis thaliana and maize, have illuminated the considerable size variation and sequence divergence of plant centromeres. Despite the severe suppression of meiotic chromosomal exchange in centromeric and pericentromeric regions of rice, the centromere core shows high rates of unequal homologous recombination in the absence of chromosomal exchange, resulting in frequent and extensive DNA rearrangement. Not only is the sequence of centromeric tandem and non-tandem repeats highly variable but also the copy number, spacing, order and orientation, providing ample natural variation as the basis for selection of superior centromere performance. This review article focuses on the structural and evolutionary dynamics of plant centromere organization and the potential molecular mechanisms responsible for the rapid changes of centromeric components.

PRDM9 and Its Role in Genetic Recombination.

PubMed

Paigen, Kenneth; Petkov, Petko M

2018-04-01

PRDM9 is a zinc finger protein that binds DNA at specific locations in the genome where it trimethylates histone H3 at lysines 4 and 36 at surrounding nucleosomes. During meiosis in many species, including humans and mice where PRDM9 has been most intensely studied, these actions determine the location of recombination hotspots, where genetic recombination occurs. In addition, PRDM9 facilitates the association of hotspots with the chromosome axis, the site of the programmed DNA double-strand breaks (DSBs) that give rise to genetic exchange between chromosomes. In the absence of PRDM9 DSBs are not properly repaired. Collectively, these actions determine patterns of genetic linkage and the possibilities for chromosome reorganization over successive generations. Copyright © 2017 Elsevier Ltd. All rights reserved.

FISH analysis in the derivation of a 12, 15, 21 complex chromosomal rearrangement

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

Stein, C.K.; Muscolino, D.; Baird, N.

Cytogenetic analysis was performed for a couple referred for recurrent pregnancy loss. Routine GTG banded studies revealed a 46,XY karyotype for the husband, but in the woman, an apparently balanced complex rearrangement involving chromosomes 12, 15, and 21 was detected. The 46,XX,t(12;15)(q13.3;q23),t(12;21)(q21;q11.2) karyotype is the consequence of 2 translocation events resulting in 3 rearranged chromosomes: (1) a derivative 12 arising from the exchange of the short arms of 12 and 21; (2) a derivative chromosome 15 consisting of segments of the long arms of chromosomes 12 and 15; and (3) a complex derivative chromosome 21 which includes the short armmore » and centromere of 21, and portions of the long arms of both chromosomes 12 and 15. Because the 12;21 translocation occurred at the centromeric region on both chromosomes, it was not possible to cytogenetically differentiate the derivative chromosomes 12 and 21. To clarify this issue, fluorescence in situ hybridization (FISH) was performed utilizing a 13/21 alpha-satellite probe. The location of the FITC signal clearly indicated a chromosome 21 centromere present on the derivative containing portions of all three chromosomes. A family history of spontaneous fetal losses suggested the possibility of a familial translocation. However, the likelihood of transmission of such a complex set of translocations is low, leading to the hypothesis that only one of the translocations was inherited with the second a de novo event in this individual. Karyotype analysis of both parents revealed no cytogenetic anomalies. Therefore, the extremely unusual occurrence of two independent translocations involving 3 chromosomes arose de novo in this patient.« less

Chromosome damage in human cells by γ rays, α particles and heavy ions: track interactions in basic dose-response relationships.

PubMed

Loucas, Bradford D; Durante, Marco; Bailey, Susan M; Cornforth, Michael N

2013-01-01

We irradiated normal human lymphocytes and fibroblasts with (137)Cs γ rays, 3.5 MeV α particles and 1 GeV/amu (56)Fe ions and measured the subsequent formation of chromosome-type aberrations by mFISH at the first mitosis following irradiation. This was done for the purposes of characterizing the shape of dose-response relationships and determining the frequency distribution of various aberration types with respect to the parameters of dose, radiation quality and cell type. Salient results and conclusions include the following. For low-LET γ rays, lymphocytes showed a more robust dose response for overall damage and a higher degree of upward curvature compared to fibroblasts. For both sources of high-LET radiation, and for both cell types, the response for simple and complex exchanges was linear with dose. Independent of all three parameters considered, the most likely damage outcome was the formation of a simple exchange event involving two breaks. However, in terms of the breakpoints making up exchange events, the majority of damage registered following HZE particle irradiation was due to complex aberrations involving multiple chromosomes. This adds a decidedly nonlinear component to the overall breakpoint response, giving it a significant degree of positive curvature, which we interpret as being due to interaction between ionizations of the primary HZE particle track and long-range δ rays produced by other nearby tracks. While such track interaction had been previously theorized, to the best of our knowledge, it has never been demonstrated experimentally.

Chromosome Damage in Human Cells by γ Rays, α Particles and Heavy Ions: Track Interactions in Basic Dose-Response Relationships

PubMed Central

Loucas, Bradford D.; Durante, Marco; Bailey, Susan M.; Cornforth, Michael N.

2013-01-01

We irradiated normal human lymphocytes and fibroblasts with 137Cs γ rays, 3.5 MeV α particles and 1 GeV/amu 56Fe ions and measured the subsequent formation of chromosome-type aberrations by mFISH at the first mitosis following irradiation. This was done for the purposes of characterizing the shape of dose-response relationships and determining the frequency distribution of various aberration types with respect to the parameters of dose, radiation quality and cell type. Salient results and conclusions include the following. For low-LET γ rays, lymphocytes showed a more robust dose response for overall damage and a higher degree of upward curvature compared to fibroblasts. For both sources of high-LET radiation, and for both cell types, the response for simple and complex exchanges was linear with dose. Independent of all three parameters considered, the most likely damage outcome was the formation of a simple exchange event involving two breaks. However, in terms of the breakpoints making up exchange events, the majority of damage registered following HZE particle irradiation was due to complex aberrations involving multiple chromosomes. This adds a decidedly nonlinear component to the overall breakpoint response, giving it a significant degree of positive curvature, which we interpret as being due to interaction between ionizations of the primary HZE particle track and long-range δ rays produced by other nearby tracks. While such track interaction had been previously theorized, to the best of our knowledge, it has never been demonstrated experimentally. PMID:23198992

A Link between Meiotic Prophase Progression and CrossoverControl

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

Carlton, Peter M.; Farruggio, Alfonso P.; Dernburg, Abby F.

2005-07-06

During meiosis, most organisms ensure that homologous chromosomes undergo at least one exchange of DNA, or crossover, to link chromosomes together and accomplish proper segregation. How each chromosome receives a minimum of one crossover is unknown. During early meiosis in Caenorhabditis elegans and many other species, chromosomes adopt a polarized organization within the nucleus, which normally disappears upon completion of homolog synapsis. Mutations that impair synapsis even between a single pair of chromosomes in C. elegans delay this nuclear reorganization. We quantified this delay by developing a classification scheme for discrete stages of meiosis. Immunofluorescence localization of RAD-51 protein revealedmore » that delayed meiotic cells also contained persistent recombination intermediates. Through genetic analysis, we found that this cytological delay in meiotic progression requires double-strand breaks and the function of the crossover-promoting heteroduplex HIM-14 (Msh4) and MSH-5. Failure of X chromosome synapsis also resulted in impaired crossover control on autosomes, which may result from greater numbers and persistence of recombination intermediates in the delayed nuclei. We conclude that maturation of recombination events on chromosomes promotes meiotic progression, and is coupled to the regulation of crossover number and placement. Our results have broad implications for the interpretation of meiotic mutants, as we have shown that asynapsis of a single chromosome pair can exert global effects on meiotic progression and recombination frequency.« less

Regions of the bread wheat D genome associated with variation in key photosynthesis traits and shoot biomass under both well watered and water deficient conditions.

PubMed

Osipova, Svetlana; Permyakov, Alexey; Permyakova, Marina; Pshenichnikova, Tatyana; Verkhoturov, Vasiliy; Rudikovsky, Alexandr; Rudikovskaya, Elena; Shishparenok, Alexandr; Doroshkov, Alexey; Börner, Andreas

2016-05-01

A quantitative trait locus (QTL) approach was taken to reveal the genetic basis in wheat of traits associated with photosynthesis during a period of exposure to water deficit stress. The performance, with respect to shoot biomass, gas exchange and chlorophyll fluorescence, leaf pigment content and the activity of various ascorbate-glutathione cycle enzymes and catalase, of a set of 80 wheat lines, each containing a single chromosomal segment introgressed from the bread wheat D genome progenitor Aegilops tauschii, was monitored in plants exposed to various water regimes. Four of the seven D genome chromosomes (1D, 2D, 5D, and 7D) carried clusters of both major (LOD >3.0) and minor (LOD between 2.0 and 3.0) QTL. A major QTL underlying the activity of glutathione reductase was located on chromosome 2D, and another, controlling the activity of ascorbate peroxidase, on chromosome 7D. A region of chromosome 2D defined by the microsatellite locus Xgwm539 and a second on chromosome 7D flanked by the marker loci Xgwm1242 and Xgwm44 harbored a number of QTL associated with the water deficit stress response.

M-Band Analysis of Chromosome Aberrations in Human Epithelial Cells Induced By Low- and High-Let Radiations

NASA Technical Reports Server (NTRS)

Hada, M.; Gersey, B.; Saganti, P. B.; Wilkins, R.; Gonda, S. R.; Cucinotta, F. A.; Wu, H.

2007-01-01

Energetic primary and secondary particles pose a health risk to astronauts in extended ISS and future Lunar and Mars missions. High-LET radiation is much more effective than low-LET radiation in the induction of various biological effects, including cell inactivation, genetic mutations, cataracts and cancer. Most of these biological endpoints are closely correlated to chromosomal damage, which can be utilized as a biomarker for radiation insult. In this study, human epithelial cells were exposed in vitro to gamma rays, 1 GeV/nucleon Fe ions and secondary neutrons whose spectrum is similar to that measured inside the Space Station. Chromosomes were condensed using a premature chromosome condensation technique and chromosome aberrations were analyzed with the multi-color banding (mBAND) technique. With this technique, individually painted chromosomal bands on one chromosome allowed the identification of both interchromosomal (translocation to unpainted chromosomes) and intrachromosomal aberrations (inversions and deletions within a single painted chromosome). Results of the study confirmed the observation of higher incidence of inversions for high-LET irradiation. However, detailed analysis of the inversion type revealed that all of the three radiation types in the study induced a low incidence of simple inversions. Half of the inversions observed in the low-LET irradiated samples were accompanied by other types of intrachromosome aberrations, but few inversions were accompanied by interchromosome aberrations. In contrast, Fe ions induced a significant fraction of inversions that involved complex rearrangements of both the inter- and intrachromosome exchanges.

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.

Inter- and Intra-Chromosomal Aberrations in Human Cells Exposed in vitro to Space-like Radiations

NASA Technical Reports Server (NTRS)

Hada, Megumi; Cucinotta, F. A.; Gonda, S. R.; Wu, H.

2005-01-01

Energetic heavy ions pose a great health risk to astronauts in extended ISS and future exploration missions. High-LET heavy ions are particularly effective in causing various biological effects, including cell inactivation, genetic mutations 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 chromosome aberrations in human lymphocytes and fibroblasts induced by both low- and high-LET radiation using FISH and multicolor fluorescence in situ hybridization (mFISH) techniques. In this study, we exposed human cells in vitro to gamma rays and energetic particles of varying types and energies and dose rates, and analyzed chromosomal damages using the multicolor banding in situ hybridization (mBAND) procedure. Confluent human epithelial cells and lymphocytes were exposed to energetic heavy ions at NASA Space Radiation Laboratory (NSRL) at the Brookhaven National Laboratory (Upton, NY) or Cs-137 gamma radiation source at the Baylor College (Houston, TX). After colcemid and Calyculin A treatment, cells were fixed and painted with XCyte3 mBAND kit (MetaSystems) and chromosome aberrations were analyzed with mBAND analysis system (MetaSystems). 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). The possible relationship between the frequency of inter- and intra-chromosomal exchanges and the track structure of radiation is discussed. The work was supported by the NASA Space Radiation Health Program.

Cre recombinase-mediated site-specific recombination between plant chromosomes.

PubMed Central

Qin, M; Bayley, C; Stockton, T; Ow, D W

1994-01-01

We report the use of the bacteriophage P1 Cre-lox system for generating conservative site-specific recombination between tobacco chromosomes. Two constructs, one containing a promoterless hygromycin-resistance gene preceded by a lox site (lox-hpt) and the other containing a cauliflower mosaic virus 35S promoter linked to a lox sequence and the cre coding region (35S-lox-cre), were introduced separately into tobacco plants. Crosses between plants harboring either construct produced plants with the two constructs situated on different chromosomes. Plants with recombination events were identified by selecting for hygromycin resistance, a phenotype expressed upon recombination. Molecular analysis showed that these recombination events occurred specifically at the lox sites and resulted in the reciprocal exchange of flanking host DNA. Progenies of these plants showed 67-100% cotransmission of the new transgenes, 35S-lox-hpt and lox-cre, consistent with the preferential cosegregation of translocated chromosomes. These results illustrate that site-specific recombination systems can be useful tools for the large-scale manipulation of eukaryotic chromosomes in vivo. Images PMID:8127869

A model of chromosome aberration induction: applications to space research.

PubMed

Ballarini, Francesca; Ottolenghi, Andrea

2005-10-01

A mechanistic model and Monte Carlo code simulating chromosome aberration induction in human lymphocytes is presented. The model is based on the assumption that aberrations arise from clustered DNA lesions and that only the free ends of clustered lesions created in neighboring chromosome territories or in the same territory can join and produce exchanges. The lesions are distributed in the cell nucleus according to the radiation track structure. Interphase chromosome territories are modeled as compact intranuclear regions with volumes proportional to the chromosome DNA contents. Both Giemsa staining and FISH painting can be simulated, and background aberrations can be taken into account. The good agreement with in vitro data provides validation of the model in terms of both the assumptions adopted and the simulation techniques. As an application in the field of space research, the model predictions were compared with aberration yields measured among crew members of long-term missions on board Mir and ISS, assuming an average radiation quality factor of 2.4. The agreement obtained also validated the model for in vivo exposure scenarios and suggested possible applications to the prediction of other relevant aberrations, typically translocations.

40 CFR 725.3 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... controls means any combination of engineering, mechanical, procedural, or biological controls designed and... purposes other than research and development. Genome means the sum total of chromosomal and... surveys, tests, and studies of: Survival and transport in air, water, and soil; ability to exchange...

40 CFR 725.3 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... controls means any combination of engineering, mechanical, procedural, or biological controls designed and... purposes other than research and development. Genome means the sum total of chromosomal and... surveys, tests, and studies of: Survival and transport in air, water, and soil; ability to exchange...

40 CFR 725.3 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... controls means any combination of engineering, mechanical, procedural, or biological controls designed and... purposes other than research and development. Genome means the sum total of chromosomal and... surveys, tests, and studies of: Survival and transport in air, water, and soil; ability to exchange...

40 CFR 725.3 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... controls means any combination of engineering, mechanical, procedural, or biological controls designed and... purposes other than research and development. Genome means the sum total of chromosomal and... surveys, tests, and studies of: Survival and transport in air, water, and soil; ability to exchange...

40 CFR 725.3 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... controls means any combination of engineering, mechanical, procedural, or biological controls designed and... purposes other than research and development. Genome means the sum total of chromosomal and... surveys, tests, and studies of: Survival and transport in air, water, and soil; ability to exchange...

Interstitial telomeric sequences in human chromosomes cluster with common fragile sites, mutagen sensitive sites, viral integration sites, cancer breakpoints, proto-oncogenes and breakpoints involved in primate evolution

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

Adekunle, S.S.A.; Wyandt, H.; Mark, H.F.L.

1994-09-01

Recently we mapped the telomeric repeat sequences to 111 interstitial sites in the human genome and to sites of gaps and breaks induced by aphidicolin and sister chromatid exchange sites detected by BrdU. Many of these sites correspond to conserved fragile sites in man, gorilla and chimpazee, to sites of conserved sister chromatid exchange in the mammalian X chromosome, to mutagenic sensitive sites, mapped locations of proto-oncogenes, breakpoints implicated in primate evolution and to breakpoints indicated as the sole anomaly in neoplasia. This observation prompted us to investigate if the interstitial telomeric sites cluster with these sites. An extensive literaturemore » search was carried out to find all the available published sites mentioned above. For comparison, we also carried out a statistical analysis of the clustering of the sites of the telomeric repeats with the gene locations where only nucleotide mutations have been observed as the only chromosomal abnormality. Our results indicate that the telomeric repeats cluster most with fragile sites, mutagenic sensitive sites and breakpoints implicated in primate evolution and least with cancer breakpoints, mapped locations of proto-oncogenes and other genes with nucleotide mutations.« less

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.

Simulation of the Formation of DNA Double Strand Breaks and Chromosome Aberrations in Irradiated Cells

NASA Technical Reports Server (NTRS)

Plante, Ianik; Ponomarev, Artem L.; Wu, Honglu; Blattnig, Steve; George, Kerry

2014-01-01

The formation of DNA double-strand breaks (DSBs) and chromosome aberrations is an important consequence of ionizing radiation. To simulate DNA double-strand breaks and the formation of chromosome aberrations, we have recently merged the codes RITRACKS (Relativistic Ion Tracks) and NASARTI (NASA Radiation Track Image). The program RITRACKS is a stochastic code developed to simulate detailed event-by-event radiation track structure: [1] This code is used to calculate the dose in voxels of 20 nm, in a volume containing simulated chromosomes, [2] The number of tracks in the volume is calculated for each simulation by sampling a Poisson distribution, with the distribution parameter obtained from the irradiation dose, ion type and energy. The program NASARTI generates the chromosomes present in a cell nucleus by random walks of 20 nm, corresponding to the size of the dose voxels, [3] The generated chromosomes are located within domains which may intertwine, and [4] Each segment of the random walks corresponds to approx. 2,000 DNA base pairs. NASARTI uses pre-calculated dose at each voxel to calculate the probability of DNA damage at each random walk segment. Using the location of double-strand breaks, possible rejoining between damaged segments is evaluated. This yields various types of chromosomes aberrations, including deletions, inversions, exchanges, etc. By performing the calculations using various types of radiations, it will be possible to obtain relative biological effectiveness (RBE) values for several types of chromosome aberrations.

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

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.

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

The spatial regulation of meiotic recombination hotspots: are all DSB hotspots crossover hotspots?

PubMed

Serrentino, Maria-Elisabetta; Borde, Valérie

2012-07-15

A key step for the success of meiosis is programmed homologous recombination, during which crossovers, or exchange of chromosome arms, take place. Crossovers increase genetic diversity but their main function is to ensure accurate chromosome segregation. Defects in crossover number and position produce aneuploidies that represent the main cause of miscarriages and chromosomal abnormalities such as Down's syndrome. Recombination is initiated by the formation of programmed double strand breaks (DSBs), which occur preferentially at places called DSB hotspots. Among all DSBs generated, only a small fraction is repaired by crossover, the other being repaired by other homologous recombination pathways. Crossover maps have been generated in a number of organisms, defining crossover hotspots. With the availability of genome-wide maps of DSBs as well as the ability to measure genetically the repair outcome at several hotspots, it is becoming more and more clear that not all DSB hotspots behave the same for crossover formation, suggesting that chromosomal features distinguish different types of hotspots. Copyright © 2012. Published by Elsevier Inc.

Abnormally banded chromosomal regions in doxorubicin-resistant B16-BL6 murine melanoma cells.

PubMed

Slovak, M L; Hoeltge, G A; Ganapathi, R

1986-08-01

B16-BL6 murine melanoma cells were selected for cytogenetic evaluation during the stepwise development of increasing resistance in vitro to the antitumor antibiotic, doxorubicin (DOX). Karyotypic studies demonstrated extensive heteroploidy with both numerical and structural abnormalities which were not present in the parental DOX-sensitive B16-BL6 cells. Trypsin-Giemsa banding revealed the presence of several marker chromosomes containing abnormally banding regions (ABRs) in the 44-fold B16-BL6 DOX-resistant subline. These ABRs appeared to be more homogeneously staining at the higher DOX concentrations. Length measurements (ABR index) in seven banded metaphases indicated a direct correlation with increasing DOX concentration. When the DOX-resistant cells were grown in drug-free medium for 1 yr, the drug-resistant phenotype gradually declined in parallel with the level of resistance and the ABR index. DOX-induced cytogenetic damage examined by sister chromatid exchange methodology in parental B16-BL6 cells indicated a linear sister chromatid exchange:DOX dose-response relationship. However, after continuous treatment of parental B16-BL6 cells with DOX (0.01 microgram/ml) for 30 days, sister chromatid exchange scores were found to return to base-line values. The B16-BL6 resistant cells demonstrated a cross-resistant phenotype with N-trifluoroacetyladriamycin-14-valerate, actinomycin D, and the Vinca alkaloids but not with 1-beta-D-arabinofuranosylcytosine. The results suggest that ABR-containing chromosomes in DOX-resistant sublines may represent cytogenetic alterations of specific amplified genes involved in the expression of DOX resistance. Further studies are required to identify and define the possible gene products and to correlate their relationship to the cytotoxic action of doxorubicin.

Elucidating the mechanisms of paternal non-disjunction of chromosome 21 in humans.

PubMed

Savage, A R; Petersen, M B; Pettay, D; Taft, L; Allran, K; Freeman, S B; Karadima, G; Avramopoulos, D; Torfs, C; Mikkelsen, M; Hassold, T J; Sherman, S L

1998-08-01

Paternal non-disjunction of chromosome 21 accounts for 5-10% of Down syndrome cases, therefore, relative to the maternally derived cases, little is known about paternally derived trisomy 21. We present the first analysis of recombination and non-disjunction for a large paternally derived population of free trisomy 21 conceptuses ( n = 67). Unlike maternal cases where the ratio of meiosis I (MI) to meiosis II (MII) errors is 3:1, a near 1:1 ratio exists among paternal cases, with a slight excess of MII errors. We found no paternal age effect for the overall population nor when classifying cases according to stage of non-disjunction error. Among 22 MI cases, only five had an observable recombinant event. This differs significantly from the 11 expected events ( P < 0.02, Fisher's exact), suggesting reduced recombination along the non-disjoined chromosomes 21 involved in paternal MI non-disjunction. No difference in recombination was detected among 27 paternal MII cases as compared with controls. However, cases exhibited a slight increase in the frequency of proximal and medial exchange when compared with controls (0.37 versus 0.28, respectively). Lastly, this study confirmed previous reports of excess male probands among paternally derived trisomy 21 cases. However, we report evidence suggesting an MII stage-specific sex ratio disturbance where 2.5 male probands were found for each female proband. Classification of MII cases based on the position of the exchange event suggested that the proband sex ratio disturbance was restricted to non-telomeric exchange cases. Based on these findings, we propose new models to explain the association between paternally derived trisomy 21 and excessive male probands.

Inter- and Intra-Chromosomal Aberrations in Human Cells Exposed in vitro to High and Low LET Radiations

NASA Technical Reports Server (NTRS)

Hada, M.; Wilkins, R.; Saganti, P. B.; Gersey, B.; Cucinotta, F. A.; Wu, H.

2006-01-01

Energetic heavy ions pose a health risk to astronauts in extended ISS and future Mars missions. High-LET heavy ions are particularly effective in causing various biological effects including cell inactivation, genetic mutations 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 chromosome aberrations in human lymphocytes and fibroblasts induced by both low- and high-LET radiation using FISH and multicolor fluorescence in situ hybridization (mFISH) techniques. In this study, we exposed human epithelial cells in vitro to gamma rays and energetic particles of varying types and energies and dose rates, and analyzed chromosomal damages using the multicolor banding in situ hybridization (mBAND) procedure. Confluent human epithelial cells (CH184B5F5/M10) were exposed to energetic heavy ions at NASA Space Radiation Laboratory (NSRL) at the Brookhaven National Laboratory, high energy neutron at the Los Alamos Nuclear Science Center (LANSCE) or Cs-137-gamma radiation source at the University of Texas, MD Anderson Cancer Center. After colcemid and Calyculin A treatment, cells were fixed and painted with XCyte3 mBAND kit (MetaSystems) and chromosome aberrations were analyzed with mBAND analysis system (MetaSystems). 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). The results of the mBAND study showed a higher ratio of inversion involved with interchromosomal exchange in heavy ions compared to -ray irradiation. Analysis of chromosome aberrations using mBAND has the potential to provide useful information on human cell response to space-like radiation.

Homoeologous chromosome pairing between the A and B genomes of Musa spp. revealed by genomic in situ hybridization

PubMed Central

Jeridi, Mouna; Bakry, Frédéric; Escoute, Jacques; Fondi, Emmanuel; Carreel, Françoise; Ferchichi, Ali; D'Hont, Angélique; Rodier-Goud, Marguerite

2011-01-01

Background and Aims Most cooking banana and several desert bananas are interspecific triploid hybrids between Musa acuminata (A genome) and Musa balbisiana (B genome). In addition, M. balbisiana has agronomical characteristics such as resistance to biotic and abiotic stresses that could be useful to improve monospecific acuminata cultivars. To develop efficient breeding strategies for improving Musa cultivars, it is therefore important to understand the possibility of chromosome exchange between these two species. Methods A protocol was developed to prepare chromosome at meiosis metaphase I suitable for genomic in situ hybridization. A series of technical challenges were encountered, the main ones being the hardness of the cell wall and the density of the microsporocyte's cytoplasm, which hampers accessibility of the probes to the chromosomes. Key parameters in solving these problems were addition of macerozyme in the enzyme mix, the duration of digestion and temperature during the spreading phase. Results and Conclusions This method was applied to analyse chromosome pairing in metaphase from triploid interspecific cultivars, and it was clearly demonstrated that interspecific recombinations between M. acuminata and M. balbisiana chromosomes do occur and may be frequent in triploid hybrids. These results provide new insight into Musa cultivar evolution and have important implications for breeding. PMID:21835815

Chromosomal Aberrations in Normal and AT Cells Exposed to High Dose of Low Dose Rate Irradiation

NASA Technical Reports Server (NTRS)

Kawata, T.; Shigematsu, N.; Kawaguchi, O.; Liu, C.; Furusawa, Y.; Hirayama, R.; George, K.; Cucinotta, F.

2011-01-01

Ataxia telangiectasia (A-T) is a human autosomally recessive syndrome characterized by cerebellar ataxia, telangiectases, immune dysfunction, and genomic instability, and high rate of cancer incidence. A-T cell lines are abnormally sensitive to agents that induce DNA double strand breaks, including ionizing radiation. The diverse clinical features in individuals affected by A-T and the complex cellular phenotypes are all linked to the functional inactivation of a single gene (AT mutated). It is well known that cells deficient in ATM show increased yields of both simple and complex chromosomal aberrations after high-dose-rate irradiation, but, less is known on how cells respond to low-dose-rate irradiation. It has been shown that AT cells contain a large number of unrejoined breaks after both low-dose-rate irradiation and high-dose-rate irradiation, however sensitivity for chromosomal aberrations at low-dose-rate are less often studied. To study how AT cells respond to low-dose-rate irradiation, we exposed confluent normal and AT fibroblast cells to up to 3 Gy of gamma-irradiation at a dose rate of 0.5 Gy/day and analyzed chromosomal aberrations in G0 using fusion PCC (Premature Chromosomal Condensation) technique. Giemsa staining showed that 1 Gy induces around 0.36 unrejoined fragments per cell in normal cells and around 1.35 fragments in AT cells, whereas 3Gy induces around 0.65 fragments in normal cells and around 3.3 fragments in AT cells. This result indicates that AT cells can rejoin breaks less effectively in G0 phase of the cell cycle? compared to normal cells. We also analyzed chromosomal exchanges in normal and AT cells after exposure to 3 Gy of low-dose-rate rays using a combination of G0 PCC and FISH techniques. Misrejoining was detected in the AT cells only? When cells irradiated with 3 Gy were subcultured and G2 chromosomal aberrations were analyzed using calyculin-A induced PCC technique, the yield of unrejoined breaks decreased in both normal and AT cells and misrejoined breaks increased in both cell lines. The present study suggests that AT cells begin to rejoin breaks when a certain number of breaks are accumulated and an increased number of exchanges were observed in G0 AT cells, which is similar situation after high-dose-rate irradiation.

Dissecting the telomere–inner nuclear membrane interface formed in meiosis

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

Pendlebury, Devon F.; Fujiwara, Yasuhiro; Tesmer, Valerie M.

Tethering telomeres to the inner nuclear membrane (INM) allows homologous chromosome pairing during meiosis. The meiosis-specific protein TERB1 binds the telomeric protein TRF1 to establish telomere–INM connectivity and is essential for mouse fertility. Here we solve the structure of the human TRF1–TERB1 interface to reveal the structural basis for telomere–INM linkage. Disruption of this interface abrogates binding and compromises telomere–INM attachment in mice. An embedded CDK-phosphorylation site within the TRF1-binding region of TERB1 provides a mechanism for cap exchange, a late-pachytene phenomenon involving the dissociation of the TRF1–TERB1 complex. Indeed, further strengthening this interaction interferes with cap exchange. Finally, ourmore » biochemical analysis implicates distinct complexes for telomere–INM tethering and chromosome-end protection during meiosis. Our studies unravel the structure, stoichiometry, and physiological implications underlying telomere–INM tethering, thereby providing unprecedented insights into the unique function of telomeres in meiosis.« less

The effects of boric acid on sister chromatid exchanges and chromosome aberrations in cultured human lymphocytes.

PubMed

Arslan, Mehmet; Topaktas, Mehmet; Rencuzogullari, Eyyüp

2008-02-01

The aim of this study was to determine the possible genotoxic effects of boric acid (BA) (E284), which is used as an antimicrobial agent in food, by using sister chromatid exchange (SCEs) and chromosome aberration (CAs) tests in human peripheral lymphocytes. The human lymphocytes were treated with 400, 600, 800, and 1000 mug/mL concentrations of BA dissolved in dimethyl sulfoxide (DMSO), for 24 h and 48 h treatment periods. BA did not increase the SCEs for all the concentrations and treatment periods when compared to control and solvent control (DMSO). BA induced structural and total CAs at all the tested concentrations for 24 and 48 h treatment periods. The induction of the total CAs was dose dependent for the 24 h treatment period. However, BA did not cause numerical CAs. BA showed a cytotoxic effect by decreasing the replication index (RI) and mitotic index (MI). BA decreased the MI in a dose-dependent manner for the 24 h treatment period.

[Cytogenetic examinations in biomonitoring residents residing closest to the area near the Sendzimir metallurgy plant in Krakow exposed to environmental pollution].

PubMed

Kubiak, R; Rudek, Z; Cieszkowski, J; Garlicki, S

1993-01-01

There are many studies done to identify the genetic hazard from occupational exposure of workers, but rather little is known about genetic effects in inhabitants of polluted areas. The aim of the study was to examine chromosome aberrations, sister chromatid exchanges and number of micronuclei in lymphocytes of persons living in the close vicinity of a large metallurgical plant. The results were compared with those obtained for the inhabitants of a village located 40 km from the city of Cracow and from the plant. An increased incidence of chromosome aberrations (0.66-4.66%, control 0.78%), sister chromatid exchanges (mean 9.73, control: 6.0) was found in the group living near the steel foundry. The paper also includes some data on measurements of the air pollution in the Nowa Huta region as well as on the amounts of heavy metals in vegetables in this region. Environmental pollution is worsening.

The Cohesion Protein SOLO Associates with SMC1 and Is Required for Synapsis, Recombination, Homolog Bias and Cohesion and Pairing of Centromeres in Drosophila Meiosis

PubMed Central

Yan, Rihui; McKee, Bruce D.

2013-01-01

Cohesion between sister chromatids is mediated by cohesin and is essential for proper meiotic segregation of both sister chromatids and homologs. solo encodes a Drosophila meiosis-specific cohesion protein with no apparent sequence homology to cohesins that is required in male meiosis for centromere cohesion, proper orientation of sister centromeres and centromere enrichment of the cohesin subunit SMC1. In this study, we show that solo is involved in multiple aspects of meiosis in female Drosophila. Null mutations in solo caused the following phenotypes: 1) high frequencies of homolog and sister chromatid nondisjunction (NDJ) and sharply reduced frequencies of homolog exchange; 2) reduced transmission of a ring-X chromosome, an indicator of elevated frequencies of sister chromatid exchange (SCE); 3) premature loss of centromere pairing and cohesion during prophase I, as indicated by elevated foci counts of the centromere protein CID; 4) instability of the lateral elements (LE)s and central regions of synaptonemal complexes (SCs), as indicated by fragmented and spotty staining of the chromosome core/LE component SMC1 and the transverse filament protein C(3)G, respectively, at all stages of pachytene. SOLO and SMC1 are both enriched on centromeres throughout prophase I, co-align along the lateral elements of SCs and reciprocally co-immunoprecipitate from ovarian protein extracts. Our studies demonstrate that SOLO is closely associated with meiotic cohesin and required both for enrichment of cohesin on centromeres and stable assembly of cohesin into chromosome cores. These events underlie and are required for stable cohesion of centromeres, synapsis of homologous chromosomes, and a recombination mechanism that suppresses SCE to preferentially generate homolog crossovers (homolog bias). We propose that SOLO is a subunit of a specialized meiotic cohesin complex that mediates both centromeric and axial arm cohesion and promotes homolog bias as a component of chromosome cores. PMID:23874232

The cohesion protein SOLO associates with SMC1 and is required for synapsis, recombination, homolog bias and cohesion and pairing of centromeres in Drosophila Meiosis.

PubMed

Yan, Rihui; McKee, Bruce D

2013-01-01

Cohesion between sister chromatids is mediated by cohesin and is essential for proper meiotic segregation of both sister chromatids and homologs. solo encodes a Drosophila meiosis-specific cohesion protein with no apparent sequence homology to cohesins that is required in male meiosis for centromere cohesion, proper orientation of sister centromeres and centromere enrichment of the cohesin subunit SMC1. In this study, we show that solo is involved in multiple aspects of meiosis in female Drosophila. Null mutations in solo caused the following phenotypes: 1) high frequencies of homolog and sister chromatid nondisjunction (NDJ) and sharply reduced frequencies of homolog exchange; 2) reduced transmission of a ring-X chromosome, an indicator of elevated frequencies of sister chromatid exchange (SCE); 3) premature loss of centromere pairing and cohesion during prophase I, as indicated by elevated foci counts of the centromere protein CID; 4) instability of the lateral elements (LE)s and central regions of synaptonemal complexes (SCs), as indicated by fragmented and spotty staining of the chromosome core/LE component SMC1 and the transverse filament protein C(3)G, respectively, at all stages of pachytene. SOLO and SMC1 are both enriched on centromeres throughout prophase I, co-align along the lateral elements of SCs and reciprocally co-immunoprecipitate from ovarian protein extracts. Our studies demonstrate that SOLO is closely associated with meiotic cohesin and required both for enrichment of cohesin on centromeres and stable assembly of cohesin into chromosome cores. These events underlie and are required for stable cohesion of centromeres, synapsis of homologous chromosomes, and a recombination mechanism that suppresses SCE to preferentially generate homolog crossovers (homolog bias). We propose that SOLO is a subunit of a specialized meiotic cohesin complex that mediates both centromeric and axial arm cohesion and promotes homolog bias as a component of chromosome cores.

Pathogenicity Island-Directed Transfer of Unlinked Chromosomal Virulence Genes

PubMed Central

Chen, John; Ram, Geeta; Penadés, José R.; Brown, Stuart; Novick, Richard P.

2014-01-01

Summary In recent decades, the notorious pathogen Staphylococcus aureus has become progressively more contagious, more virulent and more resistant to antibiotics. This implies a rather dynamic evolutionary capability, representing a remarkable level of genomic plasticity, most probably maintained by horizontal gene transfer. Here we report that the staphylococcal pathogenicity islands have a dual role in gene transfer: they not only mediate their own transfer, but they can independently direct the transfer of unlinked chromosomal segments containing virulence genes. While transfer of the island itself requires specific helper phages, transfer of unlinked chromosomal segments does not, so that potentially any pac-type phage will serve. These results reveal that SaPIs can increase the horizontal exchange of accessory genes associated with disease, and may shape pathogen genomes beyond the confines of their attachment sites. PMID:25498143

Rat chromosome 1: regional localization of seven genes (Slc9a3, Srd5a1, Esr, Tcp1, Grik5, Tnnt3, Jak2) and anchoring of the genetic linkage map to the cytogenetic map.

PubMed

Szpirer, C; Szpirer, J; Tissir, F; Stephanova, E; Vanvooren, P; Kurtz, T W; Iwai, N; Inagami, T; Pravenec, M; Kren, V; Klinga-Levan, K; Levan, G

1997-09-01

Seven genes were regionally localized on rat Chromosome (Chr) 1, from 1p11 to 1q42, and two of these genes were also included in a linkage map. This mapping work integrates the genetic linkage map and the cytogenetic map, and allows us to orient the linkage map with respect to the centromere, and to deduce the approximate position of the centromere in the linkage map. These mapping data also indicate that the Slc9a3 gene, encoding the Na+/H+ exchanger 3, is an unlikely candidate for the blood pressure loci assigned to rat Chr 1. These new localizations expand comparative mapping between rat Chr 1 and mouse or human chromosomes.

Termini of human chromosomes display elevated rates of mitotic recombination.

PubMed

Cornforth, M N; Eberle, R L

2001-01-01

The strand-specific in situ hybridization technique of CO-FISH was used to probe telomeres of human mitotic cells in order to determine the spontaneous frequency of crossover. This approach allowed the detection of recombinational crossovers occurring anywhere along the length of individual chromosomes, including reciprocal events taking place between sister chromatids. Although the process of sister chromatid exchange (SCE) is the most prominent type of recombination in somatic mammalian cells, our results show that SCEs accounted for less than a third of the recombinational events revealed by CO-FISH. It is concluded that chromosomal regions near the termini of chromosome arms undergo extraordinarily high rates of spontaneous recombination, producing terminal crossovers whose small size precludes detection by standard cytogenetic methods. That similar results were observed for transformed epithelial cells, as well as primary fibroblasts, suggests that the phenomenon is a common characteristic of human cells. These findings are noteworthy because, although telomeric and subtelomeric DNA is known to be preferentially involved in certain types of recombination, the tips of somatic mammalian chromosomes have not previously been identified as preferred sites for crossover. Implications of these results are discussed in terms of limitations imposed on CO-FISH for its proposed use in directional hybridization mapping.

Association between genomic instability and evolutionary chromosomal rearrangements in Neotropical Primates.

PubMed

Puntieri, Fiona; Andrioli, Nancy B; Nieves, Mariela

2018-06-14

During the last decades the mammalian genome has been proposed to have regions prone to breakage and reorganization concentrated in certain chromosomal bands that seem to correspond to evolutionary breakpoints. These bands are likely to be involved in chromosome fragility or instability. In Primates, some biomarkers of genetic damage may be associated with various degrees of genomic instability. Here, we investigated the usefulness of Sister Chromatid Exchange (SCE) as a biomarker of potential sites of frequent chromosome breakage and rearrangement in Alouatta caraya, Ateles chamek, Ateles paniscus and Cebus cay. These Neotropical species have particular genomic and chromosomal features allowing the analysis of genomic instability for comparative purposes. We determined the frequency of spontaneous induction of SCEs and assessed the relationship between these and structural rearrangements implicated in the evolution of the primates of interest. Overall, A. caraya and C. cay presented a low proportion of statistically significant unstable bands, suggesting fairly stable genomes and the existence of some kind of protection against endogenous damage. In contrast, Ateles showed a highly significant proportion of unstable bands; these were mainly found in the rearranged regions, which is consistent with the numerous genomic reorganizations that might have occurred during the evolution of this genus.

In vitro effect of fenthion on human lymphocytes

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

Rani, M.V.U.; Rao, M.S.

1991-08-01

Fenthion is an organophosphorus insecticide which is extensively used in control of leaf hoppers, cutworms, mites on vegetable crops. It has been reported that organophosphorus pesticides cause a significant increase in sister chromatid exchanges in mammalian cell lines. A significant increase of chromosomal aberrations has been reported in rural population exposed to pesticides. Organosphosphorus pesticides malathion, diazinon, dimethoate, phosdrin and dursban induced sister chromatid exchanges in human lymphoid cells. Exchange type of aberration has been reported in fluoriculturist who were exposed to organophosphorus, organochlorine pesticides. In the present investigation an attempt has been made to evaluate the cytogenetic effect ofmore » fenthion in human lymphocyte cultures in vitro.« less

Cyclophosphamide induced in vivo sister chromatid exchanges (SCE) in Mus musculus. I: Strain differences and empirical association with relative chromosome size.

PubMed

Reimer, D L; Singh, S M

1982-01-01

The inducibility of sister chromatid exchanges (SCEs) by cyclophosphamide (CP) in bone marrow cells was evaluated in vivo in the three genetic strains of mice (C3H/s, C57BL/6J, and Balb/c). Female mice (10 to 12 wks old, mean = 22.9g, SD = 3.2g) were administered with nine hourly injections of 214.19 mg/kg 5-Bromo-2' deoxyuridine (BrdU) followed by 0, 0.048, 0.449, 4.585 or 46.93 mg/kg CP and 4 mg/kg colcemid. SCEs were evaluated following differential staining procedures of Perry and Wolff (1974). The base-line SCEs were similar in all strains with about ten SCEs/cell. Increasing CP concentrations yielded an increased level of SCEs. Most cells showed extensive damage in CP doses exceeding 4.55 mg/kg. No SCE evaluation was possible beyond this concentration. Strain differences were evident at every dose of CP, and Balb/c was the least susceptible strain to SCE induction. F1 hybrids involving C3H/s female and Balb/c male showed SCE values closer to Balb/c. Data on the association between chromosome length and frequency of SCEs are provided. They empirically establish a positive correlation (r = 0.90) between the two features. Most induced SCEs were interstitially located rather than terminally positioned on 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.

Interclonal Variations in the Molecular Karyotype of Trypanosoma cruzi: Chromosome Rearrangements in a Single Cell-Derived Clone of the G Strain

PubMed Central

Lima, Fabio Mitsuo; Souza, Renata Torres; Santori, Fábio Rinaldo; Santos, Michele Fernandes; Cortez, Danielle Rodrigues; Barros, Roberto Moraes; Cano, Maria Isabel; Valadares, Helder Magno Silva; Macedo, Andréa Mara; Mortara, Renato Arruda; da Silveira, José Franco

2013-01-01

Trypanosoma cruzi comprises a pool of populations which are genetically diverse in terms of DNA content, growth and infectivity. Inter- and intra-strain karyotype heterogeneities have been reported, suggesting that chromosomal rearrangements occurred during the evolution of this parasite. Clone D11 is a single-cell-derived clone of the T. cruzi G strain selected by the minimal dilution method and by infecting Vero cells with metacyclic trypomastigotes. Here we report that the karyotype of clone D11 differs from that of the G strain in both number and size of chromosomal bands. Large chromosomal rearrangement was observed in the chromosomes carrying the tubulin loci. However, most of the chromosome length polymorphisms were of small amplitude, and the absence of one band in clone D11 in relation to its reference position in the G strain could be correlated to the presence of a novel band migrating above or below this position. Despite the presence of chromosomal polymorphism, large syntenic groups were conserved between the isolates. The appearance of new chromosomal bands in clone D11 could be explained by chromosome fusion followed by a chromosome break or interchromosomal exchange of large DNA segments. Our results also suggest that telomeric regions are involved in this process. The variant represented by clone D11 could have been induced by the stress of the cloning procedure or could, as has been suggested for Leishmania infantum, have emerged from a multiclonal, mosaic parasite population submitted to frequent DNA amplification/deletion events, leading to a 'mosaic' structure with different individuals having differently sized versions of the same chromosomes. If this is the case, the variant represented by clone D11 would be better adapted to survive the stress induced by cloning, which includes intracellular development in the mammalian cell. Karyotype polymorphism could be part of the T. cruzi arsenal for responding to environmental pressure. PMID:23667668

Chromosome aberrations in human lymphocytes induced by 250 MeV protons: effects of dose, dose rate and shielding.

PubMed

George, K; Willingham, V; Wu, H; Gridley, D; Nelson, G; Cucinotta, F A

2002-01-01

Although the space radiation environment consists predominantly of energetic protons, astronauts inside a spacecraft are chronically exposed to both primary particles as well as secondary particles that are generated when the primary particles penetrate the spacecraft shielding. Secondary neutrons and secondary charged particles can have an LET value that is greater than the primary protons and, therefore, produce a higher relative biological effectiveness (RBE). Using the accelerator facility at Loma Linda University, we exposed human lymphocytes in vitro to 250 MeV protons with doses ranging from 0 to 60 cGy at three different dose rates: a low dose rate of 7.5 cGy/h, an intermediate dose rate of 30 cGy/h and a high dose rate of 70 cGy/min. The effect of 15 g/cm2 aluminum shielding on the induction of chromosome aberrations was investigated for each dose rate. After exposure, lymphocytes were incubated in growth medium containing phytohemagglutinin (PHA) and chromosome spreads were collected using a chemical-induced premature chromosome condensation (PCC) technique. Aberrations were analyzed using the fluorescence in situ hybridization (FISH) technique with three different colored chromosome-painting probes. The frequency of reciprocal and complex-type chromosome exchanges were compared in shielded and unshielded samples. c2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

Chromosome aberrations in human lymphocytes induced by 250 MeV protons: effects of dose, dose rate and shielding

NASA Technical Reports Server (NTRS)

George, K.; Willingham, V.; Wu, H.; Gridley, D.; Nelson, G.; Cucinotta, F. A.

2002-01-01

Although the space radiation environment consists predominantly of energetic protons, astronauts inside a spacecraft are chronically exposed to both primary particles as well as secondary particles that are generated when the primary particles penetrate the spacecraft shielding. Secondary neutrons and secondary charged particles can have an LET value that is greater than the primary protons and, therefore, produce a higher relative biological effectiveness (RBE). Using the accelerator facility at Loma Linda University, we exposed human lymphocytes in vitro to 250 MeV protons with doses ranging from 0 to 60 cGy at three different dose rates: a low dose rate of 7.5 cGy/h, an intermediate dose rate of 30 cGy/h and a high dose rate of 70 cGy/min. The effect of 15 g/cm2 aluminum shielding on the induction of chromosome aberrations was investigated for each dose rate. After exposure, lymphocytes were incubated in growth medium containing phytohemagglutinin (PHA) and chromosome spreads were collected using a chemical-induced premature chromosome condensation (PCC) technique. Aberrations were analyzed using the fluorescence in situ hybridization (FISH) technique with three different colored chromosome-painting probes. The frequency of reciprocal and complex-type chromosome exchanges were compared in shielded and unshielded samples. c2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

Distribution of Chromosome Breakpoints in Human Epithelial Cells Exposed to Low- and High-LET Radiations

NASA Technical Reports Server (NTRS)

Hada, Megumi; Cucinotta, Francis; Wu, Honglu

2009-01-01

The advantage of the multicolor banding in situ hybridization (mBAND) technique is not only its ability to identify simultaneously both inter- and intrachromosome exchanges, but also the ability to measure the breakpoint location along the length of the chromosome in a precision that is unmatched with other traditional banding techniques. Breakpoints on specific regions of a chromosome have been known to associate with specific cancers. The breakpoint distribution in cells after low- and high-LET radiation exposures will also provide the data for biophysical modeling of the chromatin structure, as well as the data for the modeling the formation of radiation-induced chromosome aberrations. In a series of experiments, we studied low- and high-LET radiation-induced chromosome aberrations using the mBAND technique with chromosome 3 painted in 23 different colored bands. Human epithelial cells (CH1 84B5F5/M10) were exposed in vitro to Cs- 137 rays at both low and high dose rates, secondary neutrons with a broad energy spectrum at a low dose rate and 600 MeV/u Fe ions at a high dose rate. The data of both inter- and intrachromosome aberrations involving the painted chromosome have been reported previously. Here we present data of the location of the chromosome breaks along the length of chromosome 3 in the cells after exposures to each of the four radiation scenarios. In comparison to the expected breakpoint distribution based on the length of the bands, the observed distribution appeared to be non-random for both the low- and high-LET radiations. In particular, hot spots towards both ends of the chromosome were found after low-LET irradiations of either low or high dose rates. For both high-LET radiation types (Fe ions and neutrons), the breakpoint distributions were similar, and were much smoother than that for low-LET radiation. The dependence of the breakpoint distribution on the radiation quality requires further investigations.

Evolutionary consequences of polyploidy in prokaryotes and the origin of mitosis and meiosis.

PubMed

Markov, Alexander V; Kaznacheev, Ilya S

2016-06-08

The origin of eukaryote-specific traits such as mitosis and sexual reproduction remains disputable. There is growing evidence that both mitosis and eukaryotic sex (i.e., the alternation of syngamy and meiosis) may have already existed in the basal eukaryotes. The mating system of the halophilic archaeon Haloferax volcanii probably represents an intermediate stage between typical prokaryotic and eukaryotic sex. H. volcanii is highly polyploid, as well as many other Archaea. Here, we use computer simulation to explore genetic and evolutionary outcomes of polyploidy in amitotic prokaryotes and its possible role in the origin of mitosis, meiosis and eukaryotic sex. Modeling suggests that polyploidy can confer strong short-term evolutionary advantage to amitotic prokaryotes. However, it also promotes the accumulation of recessive deleterious mutations and the risk of extinction in the long term, especially in highly mutagenic environment. There are several possible strategies that amitotic polyploids can use in order to reduce the genetic costs of polyploidy while retaining its benefits. Interestingly, most of these strategies resemble different components or aspects of eukaryotic sex. They include asexual ploidy cycles, equalization of genome copies by gene conversion, high-frequency lateral gene transfer between relatives, chromosome exchange coupled with homologous recombination, and the evolution of more accurate chromosome distribution during cell division (mitosis). Acquisition of mitosis by an amitotic polyploid results in chromosome diversification and specialization. Ultimately, it transforms a polyploid cell into a functionally monoploid one with multiple unique, highly redundant chromosomes. Specialization of chromosomes makes the previously evolved modes of promiscuous chromosome shuffling deleterious. This can result in selective pressure to develop accurate mechanisms of homolog pairing, and, ultimately, meiosis. Emergence of mitosis and the first evolutionary steps towards eukaryotic sex could have taken place in the ancestral polyploid, amitotic proto-eukaryotes, as they were struggling to survive in the highly mutagenic environment of the Early Proterozoic shallow water microbial communities, through the succession of the following stages: (1) acquisition of high-frequency between-individual genetic exchange coupled with homologous recombination; (2) acquisition of mitosis, followed by rapid chromosome diversification and specialization; (3) evolution of homolog synapsis and meiosis. Additional evidence compatible with this scenario includes mass acquisition of new families of paralogous genes by the basal eukaryotes, and recently discovered correlation between polyploidy and the presence of histones in Archaea. This article was reviewed by Eugene Koonin, Uri Gophna and Armen Mulkidjanian. For the full reviews, please go to the Reviewers' comments section.

Destiny of a transgene escape from Brassica napus into Brassica rapa.

PubMed

Lu, M.; Kato, M.; Kakihara, F.

2002-07-01

Transgenic Brassica napus can be easily crossed with wild Brassica rapa. The spread of the transgene to wild species has aroused the general concern about its effect on ecological and agricultural systems. This paper was designated, by means of population genetics, to study the fate of a transgene escape from B. napus to B. rapa. Three models were proposed to survey the change in gene frequency during successive backcross processes by considering selection pressures against aneuploids, against herbicide-susceptible individuals, and by considering A-C intergenomic recombination and the effect of genetic drift. The transmission rate of an A-chromosome gene through an individual to the next generation was 50%, irrespective of the chromosome number; while that of a C-chromosome transgene varied from 8.7% to 39.9%, depending on the chromosome number of the individual used in the backcross. Without spraying herbicide, the frequency of an A-chromosome gene was 50% in the BC(1) generation, and decreased by 50% with the advance of each backcross generation; that of a C-chromosome gene was around 39.9% in BC(1), 7.7% in BC(2), 1.2% in BC(3) and 0.1% in the BC(4) generation. Under the selection pressure against herbicide-susceptible individuals, the frequency of a transgene reached a stable value of about 5.5% within six generations of successive backcrossings. The effect of genetic drift and intergenomic exchange on gene transmission rate was discussed. It is suggested that the transgene integrated on a C-chromosome (or better on a cytoplasm genome) is safer than that on an A-chromosome. The transgenic cultivars should be cultivated rotationally by year(s) with other non-transgenic varieties in order to reduce the transfer of the transgene to wild B. rapa species.

Chromosome Aberrations in Human Epithelial Cells Exposed Los Alamos High-Energy Secondary Neutrons: M-BAND Analysis

NASA Technical Reports Server (NTRS)

Hada, M.; Saganti, P. B.; Gersey, B.; Wilkins, R.; Cucinotta, F. A.; Wu, H.

2007-01-01

High-energy secondary neutrons, produced by the interaction of galactic cosmic rays (GCR) with the atmosphere, spacecraft structure and planetary surfaces, contribute a significant fraction to the dose equivalent radiation measurement in crew members and passengers of commercial aviation travel as well as astronauts in space missions. The Los Alamos Nuclear Science Center (LANSCE) neutron facility's 30L beam line (4FP30L-A/ICE House) is known to generate neutrons that simulate the secondary neutron spectrum of the Earth's atmosphere at high altitude. The neutron spectrum is also similar to that measured onboard spacecrafts like the MIR and the International Space Station (ISS). To evaluate the biological damage, we exposed human epithelial cells in vitro to the LANSCE neutron beams with an entrance dose rate of 2.5 cGy/hr, and studied the induction of chromosome aberrations that were identified with multicolor-banding in situ hybridization (mBAND) technique. With this technique, individually painted chromosomal bands on one chromosome allowed the identification of inter-chromosomal aberrations (translocation to unpainted chromosomes) and intra-chromosomal aberrations (inversions and deletions within a single painted chromosome). Compared to our previous results with gamma-rays and 600 MeV/nucleon Fe ions of high dose rate at NSRL (NASA Space Radiation Laboratory at Brookhaven National Laboratory), the neutron data from the LANSCE experiments showed significantly higher frequency of chromosome aberrations. However, detailed analysis of the inversion type revealed that all of the three radiation types in the study induced a low incidence of simple inversions. Most of the inversions in gamma-ray irradiated samples were accompanied by other types of intrachromosomal aberrations but few inversions were accompanied by interchromosomal aberrations. In contrast, neutrons and Fe ions induced a significant fraction of inversions that involved complex rearrangements of both inter- and intrachromosome exchanges. The distribution of damage sites on chromosome 3 was also compared for different radiation types. The breakpoints were randomly localized on chromosome 3 with neutrons and Fe ions exposure, whereas non-random distribution with clustering breakpoints was observed with gamma-rays exposure. The specific fingerprint of neutron radiations on chromosomal aberrations will be discussed.

Mus81 and Yen1 promote reciprocal exchange during mitotic recombination to maintain genome integrity in budding yeast

PubMed Central

Ho, Chu Kwen; Mazón, Gerard; Lam, Alicia F.; Symington, Lorraine S.

2010-01-01

Holliday junction (HJ) resolution is required for segregation of chromosomes and for formation of crossovers during homologous recombination. The identity of the resolvase(s) that functions in vivo has yet to be established, although several proteins able to cut HJs in vitro have been identified as candidates in yeasts and mammals. Using an assay to detect unselected products of mitotic recombination we found a significant decrease in crossovers in the Saccharomyces cerevisiae mus81Δ mutant. Yen1 serves a back-up function responsible for resolving intermediates in mus81Δ mutants, or when conversion tracts are short. In the absence of both Mus81 and Yen1 intermediates are not channeled exclusively to non-crossover recombinants, but instead are processed by Pol32-dependent break-induced replication (BIR). The channeling of recombination from reciprocal exchange to BIR results in greatly increased spontaneous loss of heterozygosity (LOH) and chromosome mis-segregation in the mus81Δ yen1Δ mutant, typical of the genomic instability found in tumor cells. PMID:21172663

The homologous recombination machinery modulates the formation of RNA–DNA hybrids and associated chromosome instability

PubMed Central

Wahba, Lamia; Gore, Steven K; Koshland, Douglas

2013-01-01

Genome instability in yeast and mammals is caused by RNA–DNA hybrids that form as a result of defects in different aspects of RNA biogenesis. We report that in yeast mutants defective for transcription repression and RNA degradation, hybrid formation requires Rad51p and Rad52p. These proteins normally promote DNA–DNA strand exchange in homologous recombination. We suggest they also directly promote the DNA–RNA strand exchange necessary for hybrid formation since we observed accumulation of Rad51p at a model hybrid-forming locus. Furthermore, we provide evidence that Rad51p mediates hybridization of transcripts to homologous chromosomal loci distinct from their site of synthesis. This hybrid formation in trans amplifies the genome-destabilizing potential of RNA and broadens the exclusive co-transcriptional models that pervade the field. The deleterious hybrid-forming activity of Rad51p is counteracted by Srs2p, a known Rad51p antagonist. Thus Srs2p serves as a novel anti-hybrid mechanism in vivo. DOI: http://dx.doi.org/10.7554/eLife.00505.001 PMID:23795288

The Genetics of a Small Chromosome Region of DROSOPHILA MELANOGASTER Containing the Structural Gene for Alcohol Dehydrogenase. IV: Scutoid, an Antimorphic Mutation

PubMed Central

Ashburner, M.; Tsubota, S.; Woodruff, R. C.

1982-01-01

Exchange mapping locates the dominant mutation Scutoid to the right of Adh on chromosome arm 2L of D. melanogaster. However, deletion mapping indicates that Sco is to the left of Adh. The phenotype of Sco is sensitive to mutation, or deletion, of noc+ and of three genes, el, l(2)br22, and l(2)br29 mapping immediately distal to noc. The four contiguous loci, el, l(2)br22, l(2)br29 and noc, although separable by deletion end points, interact, because certain (or all) alleles of these four loci show partial failure of complementation, or even negative complementation. The simplest hypothesis is that Sco is a small reciprocal transposition, the genes noc, osp, and Adh exchanging places with three genes normally mapping proximal to them: l(2)br34, l(2)br35 and rd. The Sco phenotype is thought to result from a position effect at the newly created noc/l(2)br28 junction. PMID:6816673

Generalized time-dependent model of radiation-induced chromosomal aberrations in normal and repair-deficient human cells.

PubMed

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

2014-03-01

We have developed a model that can simulate the yield of radiation-induced chromosomal aberrations (CAs) and unrejoined chromosome breaks in normal and repair-deficient cells. The model predicts the kinetics of chromosomal aberration formation after exposure in the G₀/G₁ phase of the cell cycle to either low- or high-LET radiation. A previously formulated model based on a stochastic Monte Carlo approach was updated to consider the time dependence of DNA double-strand break (DSB) repair (proper or improper), and different cell types were assigned different kinetics of DSB repair. The distribution of the DSB free ends was derived from a mechanistic model that takes into account the structure of chromatin and DSB clustering from high-LET radiation. The kinetics of chromosomal aberration formation were derived from experimental data on DSB repair kinetics in normal and repair-deficient cell lines. We assessed different types of chromosomal aberrations with the focus on simple and complex exchanges, and predicted the DSB rejoining kinetics and misrepair probabilities for different cell types. The results identify major cell-dependent factors, such as a greater yield of chromosome misrepair in ataxia telangiectasia (AT) cells and slower rejoining in Nijmegen (NBS) cells relative to the wild-type. The model's predictions suggest that two mechanisms could exist for the inefficiency of DSB repair in AT and NBS cells, one that depends on the overall speed of joining (either proper or improper) of DNA broken ends, and another that depends on geometric factors, such as the Euclidian distance between DNA broken ends, which influences the relative frequency of misrepair.

Baseline frequency of chromosomal aberrations and sister chromatid exchanges in peripheral blood lymphocytes of healthy individuals living in Turin (North-Western Italy): assessment of the effects of age, sex and GSTs gene polymorphisms on the levels of genomic damage.

PubMed

Santovito, Alfredo; Cervella, Piero; Delpero, Massimiliano

2016-05-01

The increased exposure to environmental pollutants has led to the awareness of the necessity for constant monitoring of human populations, especially those living in urban areas. This study evaluated the background levels of genomic damage in a sample of healthy subjects living in the urban area of Turin (Italy). The association between DNA damage with age, sex and GSTs polymorphisms was assessed. One hundred and one individuals were randomly sampled. Sister Chromatid Exchanges (SCEs) and Chromosomal Aberrations (CAs) assays, as well as genotyping of GSTT1 and GSTM1 genes, were performed. Mean values of SCEs and CAs were 5.137 ± 0.166 and 0.018 ± 0.002, respectively. Results showed age and gender associated with higher frequencies of these two cytogenetic markers. The eldest subjects (51-65 years) showed significantly higher levels of genomic damage than younger individuals. GSTs polymorphisms did not appear to significantly influence the frequencies of either markers. The CAs background frequency observed in this study is one of the highest reported among European populations. Turin is one of the most polluted cities in Europe in terms of air fine PM10 and ozone and the clastogenic potential of these pollutants may explain the high frequencies of chromosomal rearrangements reported here.

Positive regulation of meiotic DNA double-strand break formation by activation of the DNA damage checkpoint kinase Mec1(ATR).

PubMed

Gray, Stephen; Allison, Rachal M; Garcia, Valerie; Goldman, Alastair S H; Neale, Matthew J

2013-07-31

During meiosis, formation and repair of programmed DNA double-strand breaks (DSBs) create genetic exchange between homologous chromosomes-a process that is critical for reductional meiotic chromosome segregation and the production of genetically diverse sexually reproducing populations. Meiotic DSB formation is a complex process, requiring numerous proteins, of which Spo11 is the evolutionarily conserved catalytic subunit. Precisely how Spo11 and its accessory proteins function or are regulated is unclear. Here, we use Saccharomyces cerevisiae to reveal that meiotic DSB formation is modulated by the Mec1(ATR) branch of the DNA damage signalling cascade, promoting DSB formation when Spo11-mediated catalysis is compromised. Activation of the positive feedback pathway correlates with the formation of single-stranded DNA (ssDNA) recombination intermediates and activation of the downstream kinase, Mek1. We show that the requirement for checkpoint activation can be rescued by prolonging meiotic prophase by deleting the NDT80 transcription factor, and that even transient prophase arrest caused by Ndt80 depletion is sufficient to restore meiotic spore viability in checkpoint mutants. Our observations are unexpected given recent reports that the complementary kinase pathway Tel1(ATM) acts to inhibit DSB formation. We propose that such antagonistic regulation of DSB formation by Mec1 and Tel1 creates a regulatory mechanism, where the absolute frequency of DSBs is maintained at a level optimal for genetic exchange and efficient chromosome segregation.

The Relationship between the (In-)Stability of NORs and Their Chromosomal Location: The Example of Cercopithecidae and a Short Review of Other Primates.

PubMed

Gerbault-Seureau, Michèle; Cacheux, Lauriane; Dutrillaux, Bernard

2017-01-01

Amongst Cercopithecidae, the species of the Cercopithecini tribe underwent a very active chromosome evolution, principally by fissions, which increased their chromosome number up to 72. In contrast, all the species of Papionini have fairly similar karyotypes with 42 chromosomes. In animals, nucleolus organizer regions (NORs) are generally considered as instable structures, which frequently vary in size, number, and location at both infra- and interspecific levels. Although in Cercopithecinae the NORs, involved in breaks, exchanges, and translocations, behave like fragile sites in somatic cells, their number and location appear to be very stable between species. Fluorescence in situ hybridization of a 28S rDNA probe on metaphase chromosomes displayed a unique interstitial location in either an acrocentric pair (in 12 species of Cercopithecini) or a metacentric pair (in 6 species of Papionini). A non-exhaustive survey of literature data on NOR location in other primates shows that numerical variations of the NORs principally depend on their location: most multiple NORs are in terminal positions, while almost all unique NORs are in interstitial positions. We propose that this correlation is the consequence of the selection against gametic imbalances involving the chromosomal material distal to the NORs, which is effective when they are interstitially, but not terminally, located. Thus, the consequences of the interstitial NOR instability for reproduction are essentially limited to their size variations, as observed in Cercopithecidae. © 2018 S. Karger AG, Basel.

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.

mBAND Analysis of Early and Late Damages in the Chromosome of Human Lymphocytes after Exposures to Gamma Rays and Fe Ions

NASA Technical Reports Server (NTRS)

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

2013-01-01

Stable type chromosome aberrations that survive multiple generations of cell division include translocation and inversions. 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. 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. Detailed analysis of breaks participating in total chromosome exchanges within the first cell cycle post irradiation revealed a common hotspot located in the 3p21 region, which is a known fragile site corresponding to the band 6 in the mBand analysis. The breakpoint distribution in chromosomes collected at 7 days, but not at 14 days, post irradiation appeared similar to the distribution in cells collected within the first cell cycle post irradiation. The breakpoint distribution for human lymphocytes after radiation exposure was different from the previously published distribution for human mammary epithelial cells, indicating that interphase chromatin folding structures play a role in the distribution of radiation-induced breaks.

Transcription Factors Encoded on Core and Accessory Chromosomes of Fusarium oxysporum Induce Expression of Effector Genes

PubMed Central

van der Does, H. Charlotte; Schmidt, Sarah M.; Langereis, Léon; Hughes, Timothy R.

2016-01-01

Proteins secreted by pathogens during host colonization largely determine the outcome of pathogen-host interactions and are commonly called ‘effectors’. In fungal plant pathogens, coordinated transcriptional up-regulation of effector genes is a key feature of pathogenesis and effectors are often encoded in genomic regions with distinct repeat content, histone code and rate of evolution. In the tomato pathogen Fusarium oxysporum f. sp. lycopersici (Fol), effector genes reside on one of four accessory chromosomes, known as the ‘pathogenicity’ chromosome, which can be exchanged between strains through horizontal transfer. The three other accessory chromosomes in the Fol reference strain may also be important for virulence towards tomato. Expression of effector genes in Fol is highly up-regulated upon infection and requires Sge1, a transcription factor encoded on the core genome. Interestingly, the pathogenicity chromosome itself contains 13 predicted transcription factor genes and for all except one, there is a homolog on the core genome. We determined DNA binding specificity for nine transcription factors using oligonucleotide arrays. The binding sites for homologous transcription factors were highly similar, suggesting that extensive neofunctionalization of DNA binding specificity has not occurred. Several DNA binding sites are enriched on accessory chromosomes, and expression of FTF1, its core homolog FTF2 and SGE1 from a constitutive promoter can induce expression of effector genes. The DNA binding sites of only these three transcription factors are enriched among genes up-regulated during infection. We further show that Ftf1, Ftf2 and Sge1 can activate transcription from their binding sites in yeast. RNAseq analysis revealed that in strains with constitutive expression of FTF1, FTF2 or SGE1, expression of a similar set of plant-responsive genes on the pathogenicity chromosome is induced, including most effector genes. We conclude that the Fol pathogenicity chromosome may be partially transcriptionally autonomous, but there are also extensive transcriptional connections between core and accessory chromosomes. PMID:27855160

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.

Relative Biological Effectiveness of HZE Particles for Chromosomal Exchanges and Other Surrogate Cancer Risk Endpoints.

PubMed

Cacao, Eliedonna; Hada, Megumi; Saganti, Premkumar B; George, Kerry A; Cucinotta, Francis A

2016-01-01

The biological effects of high charge and energy (HZE) particle exposures are of interest in space radiation protection of astronauts and cosmonauts, and estimating secondary cancer risks for patients undergoing Hadron therapy for primary cancers. The large number of particles types and energies that makeup primary or secondary radiation in HZE particle exposures precludes tumor induction studies in animal models for all but a few particle types and energies, thus leading to the use of surrogate endpoints to investigate the details of the radiation quality dependence of relative biological effectiveness (RBE) factors. In this report we make detailed RBE predictions of the charge number and energy dependence of RBE's using a parametric track structure model to represent experimental results for the low dose response for chromosomal exchanges in normal human lymphocyte and fibroblast cells with comparison to published data for neoplastic transformation and gene mutation. RBE's are evaluated against acute doses of γ-rays for doses near 1 Gy. Models that assume linear or non-targeted effects at low dose are considered. Modest values of RBE (<10) are found for simple exchanges using a linear dose response model, however in the non-targeted effects model for fibroblast cells large RBE values (>10) are predicted at low doses <0.1 Gy. The radiation quality dependence of RBE's against the effects of acute doses γ-rays found for neoplastic transformation and gene mutation studies are similar to those found for simple exchanges if a linear response is assumed at low HZE particle doses. Comparisons of the resulting model parameters to those used in the NASA radiation quality factor function are discussed.

Relative Biological Effectiveness of HZE Particles for Chromosomal Exchanges and Other Surrogate Cancer Risk Endpoints

DOE PAGES

Cacao, Eliedonna; Hada, Megumi; Saganti, Premkumar B.; ...

2016-04-25

The biological effects of high charge and energy (HZE) particle exposures are of interest in space radiation protection of astronauts and cosmonauts, and estimating secondary cancer risks for patients undergoing Hadron therapy for primary cancers. The large number of particles types and energies that makeup primary or secondary radiation in HZE particle exposures precludes tumor induction studies in animal models for all but a few particle types and energies, thus leading to the use of surrogate endpoints to investigate the details of the radiation quality dependence of relative biological effectiveness (RBE) factors. In this report we make detailed RBE predictionsmore » of the charge number and energy dependence of RBE’s using a parametric track structure model to represent experimental results for the low dose response for chromosomal exchanges in normal human lymphocyte and fibroblast cells with comparison to published data for neoplastic transformation and gene mutation. RBE’s are evaluated against acute doses of γ-rays for doses near 1 Gy. Models that assume linear or non-targeted effects at low dose are considered. Modest values of RBE (<10) are found for simple exchanges using a linear dose response model, however in the non-targeted effects model for fibroblast cells large RBE values (>10) are predicted at low doses <0.1 Gy. The radiation quality dependence of RBE’s against the effects of acute doses γ-rays found for neoplastic transformation and gene mutation studies are similar to those found for simple exchanges if a linear response is assumed at low HZE particle doses. Finally, we discuss comparisons of the resulting model parameters to those used in the NASA radiation quality factor function.« less

Relative Biological Effectiveness of HZE Particles for Chromosomal Exchanges and Other Surrogate Cancer Risk Endpoints

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

Cacao, Eliedonna; Hada, Megumi; Saganti, Premkumar B.

The biological effects of high charge and energy (HZE) particle exposures are of interest in space radiation protection of astronauts and cosmonauts, and estimating secondary cancer risks for patients undergoing Hadron therapy for primary cancers. The large number of particles types and energies that makeup primary or secondary radiation in HZE particle exposures precludes tumor induction studies in animal models for all but a few particle types and energies, thus leading to the use of surrogate endpoints to investigate the details of the radiation quality dependence of relative biological effectiveness (RBE) factors. In this report we make detailed RBE predictionsmore » of the charge number and energy dependence of RBE’s using a parametric track structure model to represent experimental results for the low dose response for chromosomal exchanges in normal human lymphocyte and fibroblast cells with comparison to published data for neoplastic transformation and gene mutation. RBE’s are evaluated against acute doses of γ-rays for doses near 1 Gy. Models that assume linear or non-targeted effects at low dose are considered. Modest values of RBE (<10) are found for simple exchanges using a linear dose response model, however in the non-targeted effects model for fibroblast cells large RBE values (>10) are predicted at low doses <0.1 Gy. The radiation quality dependence of RBE’s against the effects of acute doses γ-rays found for neoplastic transformation and gene mutation studies are similar to those found for simple exchanges if a linear response is assumed at low HZE particle doses. Finally, we discuss comparisons of the resulting model parameters to those used in the NASA radiation quality factor function.« less

Effects of alpha-particles on survival and chromosomal aberrations in human mammary epithelial cells

NASA Technical Reports Server (NTRS)

Durante, M.; Grossi, G. F.; Gialanella, G.; Pugliese, M.; Nappo, M.; Yang, T. C.

1995-01-01

We have studied the radiation responses of a human mammary epithelial cell line, H184B5 F5-1 M/10. This cell line was derived from primary mammary cells after treatment with chemicals and heavy ions. The F5-1 M/10 cells are immortal, density-inhibited in growth, and non-tumorigenic in athymic nude mice and represent an in vitro model of the human epithelium for radiation studies. Because epithelial cells are the target of alpha-particles emitted from radon daughters, we concentrated our studies on the efficiency of alpha-particles. Confluent cultures of M/10 cells were exposed to accelerated alpha-particles [beam energy incident at the cell monolayer = 3.85 MeV, incident linear energy transfer (LET) in cell = 109 keV/microns] and, for comparison, to 80 kVp x-rays. The following endpoints were studied: (1) survival, (2) chromosome aberrations at the first postirradiation mitosis, and (3) chromosome alterations at later passages following irradiation. The survival curve was exponential for alpha-particles (D0 = 0.73 +/- 0.04 Gy), while a shoulder was observed for x-rays (alpha/beta = 2.9 Gy; D0 = 2.5 Gy, extrapolation number 1.6). The relative biological effectiveness (RBE) of high-LET alpha-particles for human epithelial cell killing was 3.3 at 37% survival. Dose-response curves for the induction of chromosome aberrations were linear for alpha-particles and linearquadratic for x-rays. The RBE for the induction of chromosome aberrations varied with the type of aberration scored and was high (about 5) for chromosome breaks and low (about 2) for chromosome exchanges.(ABSTRACT TRUNCATED AT 250 WORDS).

Persistence of radiation-induced chromosome aberrations in a long-term cell culture.

PubMed

Duran, Assumpta; Barquinero, Joan Francesc; Caballín, María Rosa; Ribas, Montserrat; Barrios, Leonardo

2009-04-01

The aim of the present study was to evaluate the persistence of chromosome aberrations induced by X rays. FISH painting and mFISH techniques were applied to long-term cultures of irradiated cells. With painting, at 2 Gy the frequency of apparently simple translocations remained almost invariable during all the culture, whereas at 4 Gy a rapid decline was observed between the first and the second samples, followed by a slight decrease until the end of the culture. Apparently simple dicentrics and complex aberrations disappeared after the first sample at 2 and 4 Gy. By mFISH, at 2 Gy the frequency of complete plus one-way translocations remained invariable between the first and last sample, but at 4 Gy a 60% decline was observed. True incomplete simple translocations disappeared at 2 and 4 Gy, indicating that incompleteness could be a factor to consider when the persistence of translocations is analyzed. The analysis by mFISH showed that the frequency of complex aberrations and their complexity increased with dose and tended to disappear in the last sample. Our results indicate that the influence of dose on the decrease in the frequency of simple translocations with time postirradiation cannot be fully explained by the disappearance of true incomplete translocations and complex aberrations. The chromosome involvement was random for radiation-induced exchange aberrations and non-random for total aberrations. Chromosome 7 showed the highest deviations from expected, being less and more involved than expected in the first and last samples, respectively. Some preferential chromosome-chromosome associations were observed, including a coincidence with a cluster from radiogenic chromosome aberrations described in other studies.

Effects of alpha-particles on survival and chromosomal aberrations in human mammary epithelial cells.

PubMed

Durante, M; Grossi, G F; Gialanella, G; Pugliese, M; Nappo, M; Yang, T C

1995-08-01

We have studied the radiation responses of a human mammary epithelial cell line, H184B5 F5-1 M/10. This cell line was derived from primary mammary cells after treatment with chemicals and heavy ions. The F5-1 M/10 cells are immortal, density-inhibited in growth, and non-tumorigenic in athymic nude mice and represent an in vitro model of the human epithelium for radiation studies. Because epithelial cells are the target of alpha-particles emitted from radon daughters, we concentrated our studies on the efficiency of alpha-particles. Confluent cultures of M/10 cells were exposed to accelerated alpha-particles [beam energy incident at the cell monolayer = 3.85 MeV, incident linear energy transfer (LET) in cell = 109 keV/microns] and, for comparison, to 80 kVp x-rays. The following endpoints were studied: (1) survival, (2) chromosome aberrations at the first postirradiation mitosis, and (3) chromosome alterations at later passages following irradiation. The survival curve was exponential for alpha-particles (D0 = 0.73 +/- 0.04 Gy), while a shoulder was observed for x-rays (alpha/beta = 2.9 Gy; D0 = 2.5 Gy, extrapolation number 1.6). The relative biological effectiveness (RBE) of high-LET alpha-particles for human epithelial cell killing was 3.3 at 37% survival. Dose-response curves for the induction of chromosome aberrations were linear for alpha-particles and linearquadratic for x-rays. The RBE for the induction of chromosome aberrations varied with the type of aberration scored and was high (about 5) for chromosome breaks and low (about 2) for chromosome exchanges.(ABSTRACT TRUNCATED AT 250 WORDS)

Derivative chromosomes involving 5p large rearranged segments went unnoticed with the use of conventional cytogenetics.

PubMed

Yokoyama, Emiy; Del Castillo, Victoria; Sánchez, Silvia; Ramos, Sandra; Molina, Bertha; Torres, Leda; Navarro, María José; Avila, Silvia; Castrillo, José Luis; García-De Teresa, Benilde; Asch, Bárbara; Frías, Sara

2018-01-01

In countries where comparative genomic hybridization arrays (aCGH) and next generation sequencing are not widely available due to accessibility and economic constraints, conventional 400-500-band karyotyping is the first-line choice for the etiological diagnosis of patients with congenital malformations and intellectual disability. Conventional karyotype analysis can rule out chromosomal alterations greater than 10 Mb. However, some large structural abnormalities, such as derivative chromosomes, may go undetected when the analysis is performed at less than a 550-band resolution and the size and banding pattern of the interchanged segments are similar. Derivatives frequently originate from inter-chromosomal exchanges and sometimes are inherited from a parent who carries a reciprocal translocation. We present two cases with derivative chromosomes involving a 9.1 Mb 5p deletion/14.8 Mb 10p duplication in the first patient and a 19.9 Mb 5p deletion/ 18.5 Mb 9p duplication in the second patient. These long chromosomal imbalances were ascertained by aCGH but not by conventional cytogenetics. Both patients presented with a deletion of the Cri du chat syndrome region and a duplication of another genomic region. Each patient had a unique clinical picture, and although they presented some features of Cri du chat syndrome, the phenotype did not conclusively point towards this diagnosis, although a chromosomopathy was suspected. These cases highlight the fundamental role of the clinical suspicion in guiding the approach for the etiological diagnosis of patients. Molecular cytogenetics techniques, such as aCGH, should be considered when the clinician suspects the presence of a chromosomal imbalance in spite of a normal karyotype.

Differential Radiosensitivity Phenotypes of DNA-PKcs Mutations Affecting NHEJ and HRR Systems following Irradiation with Gamma-Rays or Very Low Fluences of Alpha Particles

PubMed Central

Little, John B.; Kato, Takamitsu A.; Shih, Hung-Ying; Xie, Xian-Jin; Wilson Jr., Paul F.; Brogan, John R.; Kurimasa, Akihiro; Chen, David J.; Bedford, Joel S.; Chen, Benjamin P. C.

2014-01-01

We have examined cell-cycle dependence of chromosomal aberration induction and cell killing after high or low dose-rate γ irradiation in cells bearing DNA-PKcs mutations in the S2056 cluster, the T2609 cluster, or the kinase domain. We also compared sister chromatid exchanges (SCE) production by very low fluences of α-particles in DNA-PKcs mutant cells, and in homologous recombination repair (HRR) mutant cells including Rad51C, Rad51D, and Fancg/xrcc9. Generally, chromosomal aberrations and cell killing by γ-rays were similarly affected by mutations in DNA-PKcs, and these mutant cells were more sensitive in G1 than in S/G2 phase. In G1-irradiated DNA-PKcs mutant cells, both chromosome- and chromatid-type breaks and exchanges were in excess than wild-type cells. For cells irradiated in late S/G2 phase, mutant cells showed very high yields of chromatid breaks compared to wild-type cells. Few exchanges were seen in DNA-PKcs-null, Ku80-null, or DNA-PKcs kinase dead mutants, but exchanges in excess were detected in the S2506 or T2609 cluster mutants. SCE induction by very low doses of α-particles is resulted from bystander effects in cells not traversed by α-particles. SCE seen in wild-type cells was completely abolished in Rad51C- or Rad51D-deficient cells, but near normal in Fancg/xrcc9 cells. In marked contrast, very high levels of SCEs were observed in DNA-PKcs-null, DNA-PKcs kinase-dead and Ku80-null mutants. SCE induction was also abolished in T2609 cluster mutant cells, but was only slightly reduced in the S2056 cluster mutant cells. Since both non-homologous end-joining (NHEJ) and HRR systems utilize initial DNA lesions as a substrate, these results suggest the possibility of a competitive interference phenomenon operating between NHEJ and at least the Rad51C/D components of HRR; the level of interaction between damaged DNA and a particular DNA-PK component may determine the level of interaction of such DNA with a relevant HRR component. PMID:24714417

Influence of homologous recombinational repair on cell survival and chromosomal aberration induction during the cell cycle in γ-irradiated CHO cells

PubMed Central

Wilson, Paul F.; Hinz, John M.; Urbin, Salustra S.; Nham, Peter B.; Thompson, Larry H.

2010-01-01

The repair of DNA double-strand breaks (DSB) by homologous recombinational repair (HRR) underlies the high radioresistance and low mutability observed in S-phase mammalian cells. To evaluate the contributions of HRR and nonhomologous end-joining (NHEJ) to overall DSB repair capacity throughout the cell cycle after γ-irradiation, we compared HRR-deficient RAD51D-knockout 51D1 to CgRAD51D-complemented 51D1 (51D1.3) CHO cells for survival and chromosomal aberrations (CAs). Asynchronous cultures were irradiated with 150 or 300 cGy and separated by cell size using centrifugal elutriation. Cell survival of each synchronous fraction (~20 fractions total from early G1 to late G2/M) was measured by colony formation. 51D1.3 cells were most resistant in S, while 51D1 cells were most resistant in early G1 (with survival and chromosome-type CA levels similar to 51D1.3) and became progressively more sensitive throughout S and G2. Both cell lines experienced significantly reduced survival from late S into G2. Metaphases were collected from every third elutriation fraction at the first post-irradiation mitosis and scored for CAs. 51D1 cells irradiated in S and G2 had ~2-fold higher chromatid-type CAs and a remarkable ~25-fold higher level of complex chromatid-type exchanges compared to 51D1.3 cells. Complex exchanges in 51D1.3 cells were only observed in G2. These results show an essential role for HRR in preventing gross chromosomal rearrangements in proliferating cells and, with our previous report of reduced survival of G2-phase NHEJ-deficient prkdc CHO cells [Hinz et al. DNA Repair 4, 782–792, 2005], imply reduced activity/efficiency of both HRR and NHEJ as cells transition from S to G2. PMID:20434408

The putative oncogene Pim-1 in the mouse: its linkage and variation among t haplotypes.

PubMed

Nadeau, J H; Phillips, S J

1987-11-01

Pim-1, a putative oncogene involved in T-cell lymphomagenesis, was mapped between the pseudo-alpha globin gene Hba-4ps and the alpha-crystallin gene Crya-1 on mouse chromosome 17 and therefore within the t complex. Pim-1 restriction fragment variants were identified among t haplotypes. Analysis of restriction fragment sizes obtained with 12 endonucleases demonstrated that the Pim-1 genes in some t haplotypes were indistinguishable from the sizes for the Pim-1b allele in BALB/c inbred mice. There are now three genes, Pim-1, Crya-1 and H-2 I-E, that vary among independently derived t haplotypes and that have indistinguishable alleles in t haplotypes and inbred strains. These genes are closely linked within the distal inversion of the t complex. Because it is unlikely that these variants arose independently in t haplotypes and their wild-type homologues, we propose that an exchange of chromosomal segments, probably through double crossingover, was responsible for indistinguishable Pim-1 genes shared by certain t haplotypes and their wild-type homologues. There was, however, no apparent association between variant alleles of these three genes among t haplotypes as would be expected if a single exchange introduced these alleles into t haplotypes. If these variant alleles can be shown to be identical to the wild-type allele, then lack of association suggests that multiple exchanges have occurred during the evolution of the t complex.

Ribosomal DNA Organization Before and After Magnification in Drosophila melanogaster

PubMed Central

Bianciardi, Alessio; Boschi, Manuela; Swanson, Ellen E.; Belloni, Massimo; Robbins, Leonard G.

2012-01-01

In all eukaryotes, the ribosomal RNA genes are stably inherited redundant elements. In Drosophila melanogaster, the presence of a Ybb− chromosome in males, or the maternal presence of the Ribosomal exchange (Rex) element, induces magnification: a heritable increase of rDNA copy number. To date, several alternative classes of mechanisms have been proposed for magnification: in situ replication or extra-chromosomal replication, either of which might act on short or extended strings of rDNA units, or unequal sister chromatid exchange. To eliminate some of these hypotheses, none of which has been clearly proven, we examined molecular-variant composition and compared genetic maps of the rDNA in the bb2 mutant and in some magnified bb+ alleles. The genetic markers used are molecular-length variants of IGS sequences and of R1 and R2 mobile elements present in many 28S sequences. Direct comparison of PCR products does not reveal any particularly intensified electrophoretic bands in magnified alleles compared to the nonmagnified bb2 allele. Hence, the increase of rDNA copy number is diluted among multiple variants. We can therefore reject mechanisms of magnification based on multiple rounds of replication of short strings. Moreover, we find no changes of marker order when pre- and postmagnification maps are compared. Thus, we can further restrict the possible mechanisms to two: replication in situ of an extended string of rDNA units or unequal exchange between sister chromatids. PMID:22505623

The C-terminal domain of the Bloom syndrome DNA helicase is essential for genomic stability

PubMed Central

Yankiwski, Victor; Noonan, James P; Neff, Norma F

2001-01-01

Background Bloom syndrome is a rare cancer-prone disorder in which the cells of affected persons have a high frequency of somatic mutation and genomic instability. Bloom syndrome cells have a distinctive high frequency of sister chromatid exchange and quadriradial formation. BLM, the protein altered in BS, is a member of the RecQ DNA helicase family, whose members share an average of 40% identity in the helicase domain and have divergent N-terminal and C-terminal flanking regions of variable lengths. The BLM DNA helicase has been shown to localize to the ND10 (nuclear domain 10) or PML (promyelocytic leukemia) nuclear bodies, where it associates with TOPIIIα, and to the nucleolus. Results This report demonstrates that the N-terminal domain of BLM is responsible for localization of the protein to the nuclear bodies, while the C-terminal domain directs the protein to the nucleolus. Deletions of the N-terminal domain of BLM have little effect on sister chromatid exchange frequency and chromosome stability as compared to helicase and C-terminal mutations which can increase SCE frequency and chromosome abnormalities. Conclusion The helicase activity and the C-terminal domain of BLM are critical for maintaining genomic stability as measured by the sister chromatid exchange assay. The localization of BLM into the nucleolus by the C-terminal domain appears to be more important to genomic stability than localization in the nuclear bodies. PMID:11472631

Tracing Genetic Exchange and Biogeography of Cryptococcus neoformans var. grubii at the Global Population Level.

PubMed

Rhodes, Johanna; Desjardins, Christopher A; Sykes, Sean M; Beale, Mathew A; Vanhove, Mathieu; Sakthikumar, Sharadha; Chen, Yuan; Gujja, Sharvari; Saif, Sakina; Chowdhary, Anuradha; Lawson, Daniel John; Ponzio, Vinicius; Colombo, Arnaldo Lopes; Meyer, Wieland; Engelthaler, David M; Hagen, Ferry; Illnait-Zaragozi, Maria Teresa; Alanio, Alexandre; Vreulink, Jo-Marie; Heitman, Joseph; Perfect, John R; Litvintseva, Anastasia P; Bicanic, Tihana; Harrison, Thomas S; Fisher, Matthew C; Cuomo, Christina A

2017-09-01

Cryptococcus neoformans var. grubii is the causative agent of cryptococcal meningitis, a significant source of mortality in immunocompromised individuals, typically human immunodeficiency virus/AIDS patients from developing countries. Despite the worldwide emergence of this ubiquitous infection, little is known about the global molecular epidemiology of this fungal pathogen. Here we sequence the genomes of 188 diverse isolates and characterize the major subdivisions, their relative diversity, and the level of genetic exchange between them. While most isolates of C. neoformans var. grubii belong to one of three major lineages (VNI, VNII, and VNB), some haploid isolates show hybrid ancestry including some that appear to have recently interbred, based on the detection of large blocks of each ancestry across each chromosome. Many isolates display evidence of aneuploidy, which was detected for all chromosomes. In diploid isolates of C. neoformans var. grubii ( serotype AA) and of hybrids with C. neoformans var. neoformans (serotype AD) such aneuploidies have resulted in loss of heterozygosity, where a chromosomal region is represented by the genotype of only one parental isolate. Phylogenetic and population genomic analyses of isolates from Brazil reveal that the previously "African" VNB lineage occurs naturally in the South American environment. This suggests migration of the VNB lineage between Africa and South America prior to its diversification, supported by finding ancestral recombination events between isolates from different lineages and regions. The results provide evidence of substantial population structure, with all lineages showing multi-continental distributions; demonstrating the highly dispersive nature of this pathogen. Copyright © 2017 Rhodes et al.

Ultraviolet-induced sister chromatid exchanges in V-79 cells with normal and BrdUrd-substituted DNA and the influence of intercalating substances and cysteine

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

Speit, G.; Mehnert, K.; Wolf, M.

1982-06-01

The influence of intercalating substances (proflavine, ethidium bromide) and of an SH compound (L-cysteine) on uv-induced sister chromatid exchanges (SCEs) was investigated in V-79 cells with normal and BrdUrd-substituted DNA. The results are discussed in relation to the primary damages leading to SCE induction produced by uv irradiation. The data indicate that neither the pyrimidine dimers nor DNA single-strand breaks are the primary cause of SCE induction, and that the damages leading to SCEs by uv irradiation differ from those which cause chromosome aberrations.

Molecular analysis of germline t(3;6) and t(3;12) associated with conventional renal cell carcinomas indicates their rate-limiting role and supports the three-hit model of carcinogenesis.

PubMed

Yusenko, Maria V; Nagy, Anetta; Kovacs, Gyula

2010-08-01

We describe the molecular analysis of chromosomal rearrangements in familial t(3;6)(p12.3;q24.3) and t(3;12)(q13.13;q24.23) associated with the development of conventional renal cell carcinomas (RCC). We mapped the breakpoints by high-density oligo array comparative genomic hybridization of tumor cells in t(3;6) at chromosome 3p12.3 between PDZRN3 and CNTN3; the chromosomal rearrangement at 6q24.3 was mapped within the seventh intron of the STXBP5 gene. In the second case, the break at 3q13.13 was mapped downstream of PVRL3 and the breakpoint at 12q24.23 between HSPB8 and CCDC60, one allele of the latter being deleted. Reverse transcriptase polymerase chain reaction analysis of the PDZRN3, CNTN3, STXBP5, PVRL3, HSPB8, and CCDC60 genes revealed slight variation in the copy number of transcripts, but without correlation to the chromosomal rearrangements in translocation-associated and sporadic conventional RCCs. Loss of heterozygosity at chromosome 3p and mutation of VHL occurred at the same frequency in both familial and sporadic cases. Based on our model of nonhomologous chromatid exchange and the data on molecular studies, we suggest that the germline translocation serves as a rate-limiting step toward tumor development by generating a high number of cells with loss of the derivative chromosome carrying the 3p segment. Copyright (c) 2010 Elsevier Inc. All rights reserved.

Break Point Distribution on Chromosome 3 of Human Epithelial Cells exposed to Gamma Rays, Neutrons and Fe Ions

NASA Technical Reports Server (NTRS)

Hada, M.; Saganti, P. B.; Gersey, B.; Wilkins, R.; Cucinotta, F. A.; Wu, H.

2007-01-01

Most of the reported studies of break point distribution on the damaged chromosomes from radiation exposure were carried out with the G-banding technique or determined based on the relative length of the broken chromosomal fragments. However, these techniques lack the accuracy in comparison with the later developed multicolor banding in situ hybridization (mBAND) technique that is generally used for analysis of intrachromosomal aberrations such as inversions. Using mBAND, we studied chromosome aberrations in human epithelial cells exposed in vitro to both low or high dose rate gamma rays in Houston, low dose rate secondary neutrons at Los Alamos National Laboratory and high dose rate 600 MeV/u Fe ions at NASA Space Radiation Laboratory. Detailed analysis of the inversion type revealed that all of the three radiation types induced a low incidence of simple inversions. Half of the inversions observed after neutron or Fe ion exposure, and the majority of inversions in gamma-irradiated samples were accompanied by other types of intrachromosomal aberrations. In addition, neutrons and Fe ions induced a significant fraction of inversions that involved complex rearrangements of both inter- and intrachromosome exchanges. We further compared the distribution of break point on chromosome 3 for the three radiation types. The break points were found to be randomly distributed on chromosome 3 after neutrons or Fe ions exposure, whereas non-random distribution with clustering break points was observed for gamma-rays. The break point distribution may serve as a potential fingerprint of high-LET radiation exposure.

Kinetics of chromatid break repair in G2-human fibroblasts exposed to low- and high-LET radiations

NASA Technical Reports Server (NTRS)

Kawata, T.; Durante, M.; George, K.; Furusawa, Y.; Gotoh, E.; Takai, N.; Wu, H.; Cucinotta, F. A.

2001-01-01

The purpose of this study is to determine the kinetics of chromatid break rejoining following exposure to radiations of different quality. Exponentially growing human fibroblast cells AG1522 were irradiated with gamma-rays, energetic carbon (290 MeV/u), silicon (490 MeV/u) and iron (200 MeV/u, 600 MeV/u). Chromosomes were prematurely condensed using calyculin A. Prematurely condensed chromosomes were collected after several post-irradiation incubation times, ranging from 5 to 600 minutes, and the number of chromatid breaks and exchanges in G2 cells were scored. The relative biological effectiveness (RBE) for initial chromatid breaks per unit dose showed LET dependency having a peak at 55 keV/micrometers silicon (2.4) or 80 keV/micrometers carbon particles (2.4) and then decreased with increasing LET. The kinetics of chromatid break rejoining following low- or high-LET irradiation consisted of two exponential components. Chromatid breaks decreased rapidly after exposure, and then continued to decrease at a slower rate. The rejoining kinetics was similar for exposure to each type of radiation, although the rate of unrejoined breaks was higher for high-LET radiation. Chromatid exchanges were also formed quickly.

A proteomic approach to identifying new drug targets (potentiating topoisomerase II poisons).

PubMed

Jenkins, J R

2008-10-01

Topoisomerase II poisons are an established part of best clinical practice for the treatment of a number of solid tumours and haematological malignancies. However, toxicity and resistance to chemotherapeutic drugs often complicate the treatment. Furthermore, topoisomerase II poisons can also induce sister chromatid exchange, chromosomal recombination and chromosome aberrations and are associated with a significant risk of secondary leukaemia. It would therefore be of great clinical benefit if the efficacy of topoisomerase II inhibitors could be enhanced without the increased toxic side effects. It is proposed that clinical agents targeting topoisomerase II can be enhanced by inhibiting proteins that modulate topoisomerase II. The aim is to identify proteins, that by the nature of their interaction with topoisomerase II, represent putative drug targets.

[Molecular cloning and expression of Nattokinase gene in Bacillus subtilis].

PubMed

Liu, B Y; Song, H Y

2002-05-01

In order to characterize biochemically the nattokinase,the nucleotide sequence of the nattokinase gene was amplified from the chromosomal DNA of B.subtilis (natto) by PCR. The expression plasmid pBL NK was constructed and was used to transform Bacillus subtilis containing a chromosomal deletion in its subtilisin gene. The supernatant of the culture was collected after 15 h culture. The target proteins were identified by SDS-PAGE. Nattokinase was purified by a method including ultrafiltration, Sephacryl S-100 gel filtration and S-Sepharose ion-exchange chromatography, and 100 mg of purified nattokinase was obtained from one liter of culture. The purity of the protein and the specific activity were 95% and 12 000 u/mg (compared to tPA), respectively.

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

Cytogenetic damage in the blood lymphocytes of astronauts: effects of repeat long-duration space missions.

PubMed

George, K; Rhone, J; Beitman, A; Cucinotta, F A

2013-08-30

Human missions onboard the International Space Station (ISS) are increasing in duration and several astronauts have now participated in second ISS increments. The radiation environment in space is very different from terrestrial radiation exposure and it is still unclear if space flight effects and radiation from repeat missions are simply additive, which potentially confounds the assessment of the cumulative risk of radiation exposure. It has been shown that single space missions of a few months or more on the ISS can induce measureable increases in the yield of chromosome damage in the blood lymphocytes of astronauts, and it appears that cytogenetic biodosimetry can be used reliably to estimate equivalent dose and radiation risk. We have now obtained direct in vivo measurements of chromosome damage in blood lymphocytes of five astronauts before and after their first and second long duration space flights. Chromosome damage was assessed by fluorescence in situ hybridization technique using three different chromosome painting probes. All astronauts showed an increase in total exchanges and translocations after both the first and second flight. Biological dose measured using either individual assessment or a population assessment supports an additive risk model. Copyright © 2013 The Authors. Published by Elsevier B.V. All rights reserved.

Chromosome r(10)(p15.3q26.12) in a newborn child: case report.

PubMed

Gunnarsson, Cecilia; Graffmann, Barbara; Jonasson, Jon

2009-12-07

Ring chromosome 10 is a rare cytogenetic finding. Of the less than 10 reported cases we have found in the literature, none was characterized using high-resolution microarray analysis. Ring chromosomes are frequently unstable due to sister chromatid exchanges and mitotic failures. When mosaicism is present, the interpretation of genotype-phenotype correlations becomes extremely difficult. We report on a newborn girl with growth retardation, microcephaly, congenital heart defects, dysmorphic features and psychomotor retardation. Karyotyping revealed a non-mosaic apparently stable ring chromosome 10 replacing one of the normal homologues in all analyzed metaphases. High-resolution oligonucleotide microarray analysis showed a de novo approximately 12.5 Mb terminal deletion 10q26.12 -> qter and a corresponding 285 kb terminal deletion of 10pter -> p15.3. This case demonstrates that an increased nuchal translucency thickness detected by early ultrasonography should preferably lead to not only QF-PCR for the diagnosis of Down syndrome but also karyotyping. In the future, microarray analysis, which needs further evaluation, might become the method of choice. The clinical phenotype of our patient was in agreement with that of patients with a terminal 10q deletion. For the purpose of genotype-phenotype analysis, there seems to be no need for a "ring syndrome" concept.

Analysis of the Ambient Particulate Matter-induced Chromosomal Aberrations Using an In Vitro System.

PubMed

Miousse, Isabelle R; Koturbash, Igor; Chalbot, Marie-Cécile; Hauer-Jensen, Martin; Kavouras, Ilias; Pathak, Rupak

2016-12-21

Exposure to particulate matter (PM) is a major world health concern, which may damage various cellular components, including the nuclear genetic material. To assess the impact of PM on nuclear genetic integrity, structural chromosomal aberrations are scored in the metaphase spreads of mouse RAW264.7 macrophage cells. PM is collected from ambient air with a high volume total suspended particles sampler. The collected material is solubilized and filtered to retain the water-soluble, fine portion. The particles are characterized for chemical composition by nuclear magnetic resonance (NMR) spectroscopy. Different concentrations of particle suspension are added onto an in vitro culture of RAW264.7 mouse macrophages for a total exposure time of 72 hr, along with untreated control cells. At the end of exposure, the culture is treated with colcemid to arrest cells in metaphase. Cells are then harvested, treated with hypotonic solution, fixed in acetomethanol, dropped onto glass slides and finally stained with Giemsa solution. Slides are examined to assess the structural chromosomal aberrations (CAs) in metaphase spreads at 1,000X magnification using a bright-field microscope. 50 to 100 metaphase spread are scored for each treatment group. This technique is adapted for the detection of structural chromosomal aberrations (CAs), such as chromatid-type breaks, chromatid-type exchanges, acentric fragments, dicentric and ring chromosomes, double minutes, endoreduplication, and Robertsonian translocations in vitro after exposure to PM. It is a powerful method to associate a well-established cytogenetic endpoint to epigenetic alterations.

Balanced complex chromosome rearrangements: reproductive aspects. A review.

PubMed

Madan, Kamlesh

2012-04-01

This review examines the reproductive consequences for carriers of a balanced complex chromosome rearrangement (CCR). It is based on an analysis of CCRs in 103 adults referred for reproductive problems, including male infertility. The main focus is on reproductive risks based on data from 84 CCRs. Carriers of balanced CCRs have a high risk of an abortion and/or a chromosomally unbalanced child. I have identified roughly four different types of CCRs (I-IV); most (44%) belong to Type I with a simple 3-way or 4-way exchange of segments and risk factors similar to those for reciprocal translocations. There were only three CCRs (4%) of type II, which involve an inversion. Type III CCRs (21%) involve one or more insertions with ∼35% risk of a child with a duplication or a deletion of the inserted segment. Type IV CCRs (31%) involve a "middle segment" in a derivative chromosome with segments from at least three chromosomes. In ∼35% of these CCRs, recombination occurs in this segment, which can produce imbalance but in many cases it changes a CCR into a simpler balanced rearrangement in the next generation. Balanced CCRs, which have been often considered together in one group, can now be split into four types, each with a risk of a different type of imbalance. This analysis provides a better understanding of the reproductive consequences for carriers of balanced CCRs and should be useful in prenatal diagnosis and genetic counseling. Copyright © 2012 Wiley Periodicals, Inc.

Stability of Radiation Induced Chromosome Damage in Human Peripheral Blood Lymphocytes

NASA Technical Reports Server (NTRS)

Cucinotta, F. A.; George, K.; Willingham, V.

2006-01-01

Chromosome damage in an individual's peripheral blood lymphocytes can be an indicator of radiation exposure and this data can be used to evaluate dose after accidental or occupational exposure. Evidence suggests that the yield of chromosome damage in lymphocytes is also a relevant biomarker of cancer risk in humans that reflects individual cancer susceptibility. It follows that biomonitoring studies can be used to uncover subjects who are particularly susceptible to radiation damage and therefore at higher risk of cancer. Translocations and other stable aberrations are commonly believed to persist in peripheral blood cells for many years after exposure, and it has been suggested that translocations can be used for assessing retrospective radiation doses or chronic exposures. However, recent investigations suggest that translocations might not always persist indefinitely. We measured chromosome aberrations in the blood lymphocytes of six astronauts before their respective missions of approximately 3 to 6 months onboard the international space station, and again at various intervals up to 5 years after flight. In samples collected a few days after return to earth, the yield of chromosome translocations had significantly increased compared with preflight values, and results indicate that biodosimetry estimates lie within the range expected from physical dosimetry. However, for five of the astronauts, follow up analysis revealed a temporal decline in translocations with half-lives ranging from 10 to 58 months. The yield of exchanges remained unchanged for the sixth astronaut during an observation period of 5 months post-flight. These results may indicate complications with the use of stable aberrations for retrospective dose reconstruction and could affect cancer risk predictions that are estimated from yields of chromosome damage obtained shortly after exposure.

Reduced chromosome aberration complexity in normal human bronchial epithelial cells exposed to low-LET γ-rays and high-LET α-particles

PubMed Central

2013-01-01

Purpose: Cells of the lung are at risk from exposure to low and moderate doses of ionizing radiation from a range of environmental and medical sources. To help assess human health risks from such exposures, a better understanding of the frequency and types of chromosome aberration initially-induced in human lung cell types is required to link initial DNA damage and rearrangements with transmission potential and, to assess how this varies with radiation quality. Materials and methods: We exposed normal human bronchial lung epithelial (NHBE) cells in vitro to 0.5 and 1 Gy low-linear energy transfer (LET) γ-rays and a low fluence of high-LET α-particles and assayed for chromosome aberrations in premature chromosome condensation (PCC) spreads by 24-color multiplex-fluorescence in situ hybridization (M-FISH). Results: Both simple and complex aberrations were induced in a LET and dose-dependent manner; however, the frequency and complexity observed were reduced in comparison to that previously reported in spherical cell types after exposure to comparable doses or fluence of radiation. Approximately 1–2% of all exposed cells were categorized as being capable of transmitting radiation-induced chromosomal damage to future NHBE cell generations, irrespective of dose. Conclusion: One possible mechanistic explanation for this reduced complexity is the differing geometric organization of chromosome territories within ellipsoid nuclei compared to spherical nuclei. This study highlights the need to better understand the role of nuclear organization in the formation of exchange aberrations and, the influence three-dimensional (3D) tissue architecture may have on this in vivo. PMID:23679558

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

Harrison, F.L.; Rice, D.W. Jr., Moore, D.H.

Traditional bioassays are unsuitable for assessing sublethal effects from ocean disposal of low-level radioactive waste because mortality and phenotypic responses are not anticipated. We compared the usefulness of chromosomal aberration and sister chromatid exchange (SCE) induction as measures of low-level radiation effects in a sediment-dwelling marine worm, Neanthes arenaceodentata. The SCEs, in contrast to chromosomal aberrations, do not alter the overall chromosome morphology and in mammalian cells appear to be a more sensitive indicator of DNA alterations caused by environmental mutagens. Newly hatched larvae were exposed to two radiation-exposure regimes of either x rays at a high dose rate ofmore » 0.7 Gy (70 rad)/min for as long as 5.5 min or to /sup 60/Co gamma rays at a low dose rate of from 4.8 x 10/sup -5/ to 1.2 x 10/sup -1/ Gy (0.0048 to 12 rad)/h for 24 h. After irradiation, the larvae were exposed to 3 x 10/sup -5/M bromodeoxyuridine (BrdUrd) for 28 h (x-ray-irradiated larvae) or for 54 h (/sup 60/Co-irradiated larvae). Larval cells were examined for the proportion of cells in first, second, and third or greater division. Frequencies of chromosomal aberrations and SCEs were determined in first and second division cells, respectively. Results from x-ray irradiation indicated that dose-related increases occur in chromosome and chromatid deletions, but a dose of equal or greater 2 Gy (equal to or greater than 200 rad) was required to observe a significant increase. Worm larvae receiving /sup 60/Co irradiation showed elevated SCE frequencies with a significant increase of 0.6 Gy (60 rad). We suggest that both SCEs and chromosomal aberrations may be useful for measuring effects on genetic material induced by radiation. 56 references, 7 figures, 9 tables.« less

Chromosomal and cytoplasmic context determines predisposition to maternal age-related aneuploidy: brief overview and update on MCAK in mammalian oocytes.

PubMed

Eichenlaub-Ritter, Ursula; Staubach, Nora; Trapphoff, Tom

2010-12-01

It has been known for more than half a century that the risk of conceiving a child with trisomy increases with advanced maternal age. However, the origin of the high susceptibility to nondisjunction of whole chromosomes and precocious separation of sister chromatids, leading to aneuploidy in aged oocytes and embryos derived from them, cannot be traced back to a single disturbance and mechanism. Instead, analysis of recombination patterns of meiotic chromosomes of spread oocytes from embryonal ovary, and of origins and exchange patterns of extra chromosomes in trisomies, as well as morphological and molecular studies of oocytes and somatic cells from young and aged females, show chromosome-specific risk patterns and cellular aberrations related to the chronological age of the female. In addition, analysis of the function of meiotic- and cell-cycle-regulating genes in oogenesis, and the study of the spindle and chromosomal status of maturing oocytes, suggest that several events contribute synergistically to errors in chromosome segregation in aged oocytes in a chromosome-specific fashion. For instance, loss of cohesion may differentially predispose chromosomes with distal or pericentromeric chiasmata to nondisjunction. Studies on expression in young and aged oocytes from human or model organisms, like the mouse, indicate that the presence and functionality/activity of gene products involved in cell-cycle regulation, spindle formation and organelle integrity may be altered in aged oocytes, thus contributing to a high risk of error in chromosome segregation in meiosis I and II. Genes that are often altered in aged mouse oocytes include MCAK (mitotic-centromere-associated protein), a microtubule depolymerase, and AURKB (Aurora kinase B), a protein of the chromosomal passenger complex that has many targets and can also phosphorylate and regulate MCAK localization and activity. Therefore we explored the role of MCAK in maturing mouse oocytes by immunofluorescence, overexpression of a MCAK-EGFP (enhanced green fluorescent protein) fusion protein, knockdown of MCAK by RNAi (RNA interference) and inhibition of AURKB. The observations suggest that MCAK is involved in spindle regulation, chromosome congression and cell-cycle control, and that reductions in mRNA and protein in a context of permissive SAC (spindle assembly checkpoint) predispose to aneuploidy. Failure to recruit MCAK to centromeres and low expression patterns, as well as disturbances in regulation of enzyme localization and activity, e.g. due to alterations in activity of AURKB, may therefore contribute to maternal age-related rises in aneuploidy in mammalian oocytes.

Novel Missense Mutation A789V in IQSEC2 Underlies X-Linked Intellectual Disability in the MRX78 Family

PubMed Central

Kalscheuer, Vera M.; James, Victoria M.; Himelright, Miranda L.; Long, Philip; Oegema, Renske; Jensen, Corinna; Bienek, Melanie; Hu, Hao; Haas, Stefan A.; Topf, Maya; Hoogeboom, A. Jeannette M.; Harvey, Kirsten; Walikonis, Randall; Harvey, Robert J.

2016-01-01

Disease gene discovery in neurodevelopmental disorders, including X-linked intellectual disability (XLID) has recently been accelerated by next-generation DNA sequencing approaches. To date, more than 100 human X chromosome genes involved in neuronal signaling pathways and networks implicated in cognitive function have been identified. Despite these advances, the mutations underlying disease in a large number of XLID families remained unresolved. We report the resolution of MRX78, a large family with six affected males and seven affected females, showing X-linked inheritance. Although a previous linkage study had mapped the locus to the short arm of chromosome X (Xp11.4-p11.23), this region contained too many candidate genes to be analyzed using conventional approaches. However, our X-chromosome exome resequencing, bioinformatics analysis and inheritance testing revealed a missense mutation (c.C2366T, p.A789V) in IQSEC2, encoding a neuronal GDP-GTP exchange factor for Arf family GTPases (ArfGEF) previously implicated in XLID. Molecular modeling of IQSEC2 revealed that the A789V substitution results in the insertion of a larger side-chain into a hydrophobic pocket in the catalytic Sec7 domain of IQSEC2. The A789V change is predicted to result in numerous clashes with adjacent amino acids and disruption of local folding of the Sec7 domain. Consistent with this finding, functional assays revealed that recombinant IQSEC2A789V was not able to catalyze GDP-GTP exchange on Arf6 as efficiently as wild-type IQSEC2. Taken together, these results strongly suggest that the A789V mutation in IQSEC2 is the underlying cause of XLID in the MRX78 family. PMID:26793055

Meiotic recombination hotspots - a comparative view.

PubMed

Choi, Kyuha; Henderson, Ian R

2015-07-01

During meiosis homologous chromosomes pair and undergo reciprocal genetic exchange, termed crossover. Meiotic recombination has a profound effect on patterns of genetic variation and is an important tool during crop breeding. Crossovers initiate from programmed DNA double-stranded breaks that are processed to form single-stranded DNA, which can invade a homologous chromosome. Strand invasion events mature into double Holliday junctions that can be resolved as crossovers. Extensive variation in the frequency of meiotic recombination occurs along chromosomes and is typically focused in narrow hotspots, observed both at the level of DNA breaks and final crossovers. We review methodologies to profile hotspots at different steps of the meiotic recombination pathway that have been used in different eukaryote species. We then discuss what these studies have revealed concerning specification of hotspot locations and activity and the contributions of both genetic and epigenetic factors. Understanding hotspots is important for interpreting patterns of genetic variation in populations and how eukaryotic genomes evolve. In addition, manipulation of hotspots will allow us to accelerate crop breeding, where meiotic recombination distributions can be limiting. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

Induction and prevention of micronuclei and chromosomal aberrations in cultured human lymphocytes exposed to the light of halogen tungsten lamps.

PubMed

D'Agostini, F; Caimo, A; De Filippi, S; De Flora, S

1999-07-01

Previous studies have shown that the light emitted by halogen tungsten lamps contains UV radiation in the UV-A, UV-B and UV-C regions, induces mutations and irreparable DNA damage in bacteria, enhances the frequency of micronuclei in cultured human lymphocytes and is potently carcinogenic to the skin of hairless mice. The present study showed that the light emitted by an uncovered, traditional halogen lamp induces a significant, dose-related and time-related increase not only in micronuclei but also in chromosome-type aberrations, such as breaks, and even more in chromatid-type aberrations, such as isochromatid breaks, exchanges and isochromatid/chromatid interchanges, all including gaps or not, in cultured human lymphocytes. All these genotoxic effects were completely prevented by shielding the same lamp with a silica glass cover, blocking UV radiation. A new model of halogen lamp, having the quartz bulb treated in order to reduce the output of UV radiation, was considerably less genotoxic than the uncovered halogen lamp, yet induction of chromosomal alterations was observed at high illuminance levels.

[Radiation biology of structurally different Drosophila genes. Report 2. The vestigial gene: molecular characteristics of chromosome mutations].

PubMed

Afanas'eva, K P; Aleksandrova, M V; Aleksandrov, I D; Korablinova, S V

2012-01-01

The results of the PCR-assay of mutation lesions at each of 16 fragments overlapping the entire vestigial (vg) gene of Drosophila melanogaster in 52 gamma-ray-, neutron- and neutron + gamma-ray-induced vg mutants having the inversion or translocation breakpoint within the vg microregion are presented. 4 from 52 mutants studied were found to have large deletions of about 200 kb covering the entire vg gene and adjacent to sca and l(2)C gene-markers as well. 23 mutants from 48 (47.9%) were found to have a wild-type gene structure showing that the exchange breakpoints are located outside of the vg gene. 25 others display the intragenic lesions of different complexity detected by PCR as the absence of(i) either one fragment or (ii) two or more (6-7) adjacent fragments and (iii) simultaneously several (i) or (i) and (ii) types separated by normal gene regions. It is important that 6 from 25 mutants have the breakpoint inside the vg gene and display the (i) or (ii) type of lesions at the gene regions containing the putative break whereas 5 others from 25 with the above lesions have the exchange breakpoint outside the vg gene. Therefore, the breakpoints underlying either inversions or translocations induced by low- and high-LET radiation are likely to be located within and outside the gene under study. Thereby, the formation of exchanges is accompanied by DNA deletions of various sizes at the exchange breakpoints. The molecular model of formation of such exchange-deletion rearrangements is elaborated and presented. Also, conception of the predominately clustered action of both low- and high-LET radiation on the germ cell genome is suggested as the summing-up of the presented results. The ability of ionizing radiation to induce the clusters of genetic alterations in the form of hidden DNA damages as well as gene/chromosome mutations is determined by the track structure and hierarchical organization of the genome. To detect the quality and frequency patterns of all components of the cluster, joint molecular, genetic and cytological techniques need to be used.

High-LET radiation-induced aberrations in prematurely condensed G2 chromosomes of human fibroblasts

NASA Technical Reports Server (NTRS)

Kawata, T.; Gotoh, E.; Durante, M.; Wu, H.; George, K.; Furusawa, Y.; Cucinotta, F. A.; Dicello, J. F. (Principal Investigator)

2000-01-01

PURPOSE: To determine the number of initial chromatid breaks induced by low- or high-LET irradiations, and to compare the kinetics of chromatid break rejoining for radiations of different quality. MATERIAL AND METHODS: Exponentially growing human fibroblast cells AG1522 were irradiated with gamma-rays, energetic carbon (290MeV/u), silicon (490MeV/u) and iron (200 and 600 MeV/u). Chromosomes were prematurely condensed using calyculin A. Chromatid breaks and exchanges in G2 cells were scored. PCC were collected after several post-irradiation incubation times, ranging from 5 to 600 min. RESULTS: The kinetics of chromatid break rejoining following low- or high-LET irradiation consisted of two exponential components representing a rapid and a slow time constant. Chromatid breaks decreased rapidly during the first 10min after exposure, then continued to decrease at a slower rate. The rejoining kinetics were similar for exposure to each type of radiation. Chromatid exchanges were also formed quickly. Compared to low-LET radiation, isochromatid breaks were produced more frequently and the proportion of unrejoined breaks was higher for high-LET radiation. CONCLUSIONS: Compared with gamma-rays, isochromatid breaks were observed more frequently in high-LET irradiated samples, suggesting that an increase in isochromatid breaks is a signature of high-LET radiation exposure.

Rampant Gene Exchange Across a Strong Reproductive Barrier Between the Annual Sunflowers, Helianthus annuus and H. petiolaris

PubMed Central

Yatabe, Yoko; Kane, Nolan C.; Scotti-Saintagne, Caroline; Rieseberg, Loren H.

2007-01-01

Plant species may remain morphologically distinct despite gene exchange with congeners, yet little is known about the genomewide pattern of introgression among species. Here we analyze the effects of persistent gene flow on genomic differentiation between the sympatric sunflower species Helianthus annuus and H. petiolaris. While the species are strongly isolated in testcrosses, genetic distances at 108 microsatellite loci and 14 sequenced genes are highly variable and much lower (on average) than for more closely related but historically allopatric congeners. Our analyses failed to detect a positive association between levels of genetic differentiation and chromosomal rearrangements (as reported in a prior publication) or proximity to QTL for morphological differences or hybrid sterility. However, a significant increase in differentiation was observed for markers within 5 cM of chromosomal breakpoints. Together, these results suggest that islands of differentiation between these two species are small, except in areas of low recombination. Furthermore, only microsatellites associated with ESTs were identified as outlier loci in tests for selection, which might indicate that the ESTs themselves are the targets of selection rather than linked genes (or that coding regions are not randomly distributed). In general, these results indicate that even strong and genetically complex reproductive barriers cannot prevent widespread introgression. PMID:17277373

RecFOR Is Not Required for Pneumococcal Transformation but Together with XerS for Resolution of Chromosome Dimers Frequently Formed in the Process

PubMed Central

Johnston, Calum; Mortier-Barrière, Isabelle; Granadel, Chantal; Polard, Patrice; Martin, Bernard; Claverys, Jean-Pierre

2015-01-01

Homologous recombination (HR) is required for both genome maintenance and generation of diversity in eukaryotes and prokaryotes. This process initiates from single-stranded (ss) DNA and is driven by a universal recombinase, which promotes strand exchange between homologous sequences. The bacterial recombinase, RecA, is loaded onto ssDNA by recombinase loaders, RecBCD and RecFOR for genome maintenance. DprA was recently proposed as a third loader dedicated to genetic transformation. Here we assessed the role of RecFOR in transformation of the human pathogen Streptococcus pneumoniae. We firstly established that RecFOR proteins are not required for plasmid transformation, strongly suggesting that DprA ensures annealing of plasmid single-strands internalized in the process. We then observed no reduction in chromosomal transformation using a PCR fragment as donor, contrasting with the 10,000-fold drop in dprA - cells and demonstrating that RecFOR play no role in transformation. However, a ∼1.45-fold drop in transformation was observed with total chromosomal DNA in recFOR mutants. To account for this limited deficit, we hypothesized that transformation with chromosomal DNA stimulated unexpectedly high frequency (>30% of cells) formation of chromosome dimers as an intermediate in the generation of tandem duplications, and that RecFOR were crucial for dimer resolution. We validated this hypothesis, showing that the site-specific recombinase XerS was also crucial for dimer resolution. An even higher frequency of dimer formation (>80% of cells) was promoted by interspecies transformation with Streptococcus mitis chromosomal DNA, which contains numerous inversions compared to pneumococcal chromosome, each potentially promoting dimerization. In the absence of RecFOR and XerS, dimers persist, as confirmed by DAPI staining, and can limit the efficiency of transformation, since resulting in loss of transformant chromosome. These findings strengthen the view that different HR machineries exist for genome maintenance and transformation in pneumococci. These observations presumably apply to most naturally transformable species. PMID:25569614

The transposon Galileo generates natural chromosomal inversions in Drosophila by ectopic recombination.

PubMed

Delprat, Alejandra; Negre, Bàrbara; Puig, Marta; Ruiz, Alfredo

2009-11-18

Transposable elements (TEs) are responsible for the generation of chromosomal inversions in several groups of organisms. However, in Drosophila and other Dipterans, where inversions are abundant both as intraspecific polymorphisms and interspecific fixed differences, the evidence for a role of TEs is scarce. Previous work revealed that the transposon Galileo was involved in the generation of two polymorphic inversions of Drosophila buzzatii. To assess the impact of TEs in Drosophila chromosomal evolution and shed light on the mechanism involved, we isolated and sequenced the two breakpoints of another widespread polymorphic inversion from D. buzzatii, 2z(3). In the non inverted chromosome, the 2z(3) distal breakpoint was located between genes CG2046 and CG10326 whereas the proximal breakpoint lies between two novel genes that we have named Dlh and Mdp. In the inverted chromosome, the analysis of the breakpoint sequences revealed relatively large insertions (2,870-bp and 4,786-bp long) including two copies of the transposon Galileo (subfamily Newton), one at each breakpoint, plus several other TEs. The two Galileo copies: (i) are inserted in opposite orientation; (ii) present exchanged target site duplications; and (iii) are both chimeric. Our observations provide the best evidence gathered so far for the role of TEs in the generation of Drosophila inversions. In addition, they show unequivocally that ectopic recombination is the causative mechanism. The fact that the three polymorphic D. buzzatii inversions investigated so far were generated by the same transposon family is remarkable and is conceivably due to Galileo's unusual structure and current (or recent) transpositional activity.

Persistence of Space Radiation-Induced Cytogenetic Damage in the Blood Lymphocytes of Astronauts and the Effects of Repeat Long Duration Space Missions

NASA Technical Reports Server (NTRS)

George, Kerry A.; Cucinotta, Francis A.

2009-01-01

The yield of chromosome damage in astronauts blood lymphocytes has been shown to increase after long duration space missions of a few months or more. This provides a useful in vivo measurement of space radiation induced damage that takes into account individual radiosensitivity and considers the influence of microgravity and other stress conditions. We present our latest follow-up analyses of chromosome damage in astronauts blood lymphocytes assessed by fluorescence in situ hybridization (FISH) chromosome painting and collected at various times, from directly after return from space to several years after flight. For most individuals the analysis of individual time-courses for translocations revealed a temporal decline of yields with different half-lives. Dose was derived from frequencies of chromosome exchanges using preflight calibration curves, and estimates derived from samples collected a few days after return to earth lie within the range expected from physical dosimetry. However, a temporal decline in yields may indicate complications with the use of stable aberrations for retrospective dose reconstruction, and the differences in the decay time may reflect individual variability in risk from space radiation exposure. Limited data on three individuals who have participated in repeat long duration space flights indicates a lack of correlation between time in space and translocation yields, and show a possible adaptive response to space radiation exposure.

Studies of DNA and chromosome damage in skin fibroblasts and blood lymphocytes from psoriasis patients treated with 8-methoxypsoralen and UVA irradiation

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

Bredberg, A.; Lambert, B.; Lindblad, A.

1983-08-01

Exposure of human lymphocytes and skin fibroblasts in vitro to a single, clinically used dose of PUVA, i.e., 0.1 micrograms/ml of 8-methoxypsoralen (8-MOP) plus 0.9-4 J/cm2 of longwave ultraviolet radiation (UVA), lead to the formation of DNA damage as determined by alkaline elution, and to chromosome aberrations and sister chromatid exchanges (SCE). When lymphocyte-enriched plasma was obtained from psoriasis patients 2 h after oral intake of 8-MOP and then UVA irradiated (1.8-3.6 J/cm2) in vitro, an increased frequency of chromosome aberrations and SCE was observed. Normal levels of chromosome aberrations and SCE were found in lymphocytes of psoriasis patients aftermore » 3-30 weeks of PUVA treatment in vivo. A small but statistically significant increase in the SCE frequency was observed in the lymphocytes of psoriasis patients treated for 1-6 years with PUVA (mean 18.0 SCE/cell) as compared with before PUVA (mean 15.8, p less than 0.05). Skin fibroblasts of psoriasis patients analyzed 5 years after the start of PUVA treatment showed a normal number of SCE but a high fraction of filter-retained DNA in the alkaline elution assay, suggesting the presence of cross-linked DNA.« less

Molecular Variation of Adh and P6 Genes in an African Population of Drosophila Melanogaster and Its Relation to Chromosomal Inversions

PubMed Central

Benassi, V.; Aulard, S.; Mazeau, S.; Veuille, M.

1993-01-01

Four-cutter molecular polymorphism of Adh and P6, and chromosome inversion polymorphism of chromosome II were investigated in 95 isogenic lines of an Ivory Coast population of Drosophila melanogaster, a species assumed to have recently spread throughout the world from a West African origin. The P6 gene showed little linkage disequilibrium with the In(2L)t inversion, although it is located within this inversion. This suggests that the inversion and the P6 locus have extensively exchanged genetic information through either double crossover or gene conversion. Allozymic variation in ADH was in linkage disequilibrium with In(2L)t and In(2R)NS inversions. Evidence suggests either that inversion linkage with the Fast allele is selectively maintained, or that this allele only recently appeared. Molecular polymorphism at the Adh locus in the Ivory Coast is not higher than in North American populations. New haplotypes specific to the African population were found, some of them connect the ``Wa(s)-like'' haplotypes found at high frequencies in the United States to the other slow haplotypes. Their relation with In(2L)t supports the hypothesis that Wa(s) recently recombined away from an In(2L)t chromosome which may be the cause of its divergence from the other haplotypes. PMID:8349110

Identification of Balanced Chromosomal Rearrangements Previously Unknown Among Participants in the 1000 Genomes Project: Implications for Interpretation of Structural Variation in Genomes and the Future of Clinical Cytogenetics

PubMed Central

Dong, Zirui; Wang, Huilin; Chen, Haixiao; Jiang, Hui; Yuan, Jianying; Yang, Zhenjun; Wang, Wen-Jing; Xu, Fengping; Guo, Xiaosen; Cao, Ye; Zhu, Zhenzhen; Geng, Chunyu; Cheung, Wan Chee; Kwok, Yvonne K; Yang, Huangming; Leung, Tak Yeung; Morton, Cynthia C.; Cheung, Sau Wai; Choy, Kwong Wai

2017-01-01

Purpose Recent studies demonstrate that whole-genome sequencing (WGS) enables detection of cryptic rearrangements in apparently balanced chromosomal rearrangements (also known as balanced chromosomal abnormalities, BCAs) previously identified by conventional cytogenetic methods. We aimed to assess our analytical tool for detecting BCAs in The 1000 Genomes Project without knowing affected bands. Methods The 1000 Genomes Project provides an unprecedented integrated map of structural variants in phenotypically normal subjects, but there is no information on potential inclusion of subjects with apparently BCAs akin to those traditionally detected in diagnostic cytogenetics laboratories. We applied our analytical tool to 1,166 genomes from the 1000 Genomes Project with sufficient physical coverage (8.25-fold). Results Our approach detected four reciprocal balanced translocations and four inversions ranging in size from 57.9 kb to 13.3 Mb, all of which were confirmed by cytogenetic methods and PCR studies. One of DNAs has a subtle translocation that is not readily identified by chromosome analysis due to similar banding patterns and size of exchanged segments, and another results in disruption of all transcripts of an OMIM gene. Conclusions Our study demonstrates the extension of utilizing low-coverage WGS for unbiased detection of BCAs including translocations and inversions previously unknown in the 1000 Genomes Project. PMID:29095815

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

Harrison, F.L.; Rice, D.W. Jr.

The usefulness of sister chromatid exchange (SCE) induction as a measure of low-level radiation effect was examined in a benthic marine worm, Neanthes arenaceodentata. Larvae were exposed to /sup 60/Co radiation for 12 to 24 h at total doses ranging from 0.5 to 309 R and at dose rates from 0.04 to 13 R/h. Animals exposed at intermediate dose rates (0.5, 0.6, 1.25, 2.0, and 2.5 R/h) had SCE frequencies per chromosome about twice that of those receiving no radiation (controls), whereas those exposed at the higher dose rates (7.0 and 13 R/h) had SCE frequencies lower than the controls.more » Animals exposed at the lower dose rates (0.04 and 0.1 R/h) had lower SCE frequencies than those exposed at intermediate dose rates (and higher SCE frequencies than controls). The length of chromosome pair number one differed among metaphase spreads and was used as an index of chromosome condensation in a given metaphase. Because there is a possibility that chromosome morphology may affect the ability to resolve SCEs, morphology will be monitored in future studies. A preliminary experiment was performed to assess the effects of 2.2 and 11.5 R/h for 24 h on growth and development. Larvae observed at 6 and 17 d after irradiation did not have significantly different numbers of abnormal larvae or survival rates.« less

Bion M1. Peculiarities of life activities of microbes in 30-day spaceflight

NASA Astrophysics Data System (ADS)

Viacheslav, Ilyin; Korshunov, Denis; Morozova, Julia; Voeikova, Tatiana; Tyaglov, Boris; Novikova, Liudmila; Krestyanova, Irina; Emelyanova, Lydia

The aim of this work was to analyze the influence of space flight factors ( SFF) to microorganism strains , exposed inside unmanned spacecraft Bion M-1 during the 30- day space flight. Objectives of the work - the study of the influence of the SFF exchange chromosomal DNA in crosses microorganisms of the genus Streptomyces; the level of spontaneous phage induction of lysogenic strains fS31 from Streptomyces lividans 66 and Streptomyces coelicolor A3 ( 2 ) on the biosynthesis of the antibiotic tylosin strain of Streptomyces fradiae; survival electrogenic bacteria Shewanella oneidensis MR- 1 is used in the microbial fuel cell As a result of this work it was found that the SFF affect the exchange of chromosomal DNA by crossing strains of Streptomyces. Was detected polarity crossing , expressed in an advantageous contribution chromosome fragment of one of the parent strains in recombinant offspring. This fact may indicate a more prolonged exposure of cells in microgravity and , as a consequence, the transfer of longer fragments of chromosomal DNA This feature is the transfer of genetic material in microgravity could lead to wider dissemination and horizontal transfer of chromosomal and plasmid DNA of symbiotic microflora astronauts and other strains present in the spacecraft. It was shown no effect on the frequency of recombination PCF and the level of mutation model reversion of auxotrophic markers to prototrophy It was demonstrated that PCF increase the level of induction of cell actinophage fS31 lysogenic strain of S. lividans 66, but did not affect the level of induction of this phage cells S. coelicolor A3 ( 2). It is shown that the lower the level of synthesis PCF antibiotic aktinorodina (actinorhodin) in lysogenic strain S. coelicolor A3 ( 2). 66 Strains of S. lividans and S. coelicolor A3 ( 2 ) can be used as a biosensor for studying the effect on microorganisms PCF It is shown that the effect of the PCF reduces synthesis of tylosin and desmicosyn S. fradiae at about 30 % as compared with the synchronous control, but the ratio of desmycosine to tylosin does not change. It was estimated that the strain S. oneidensis MR- 1 under the conditions of flight remains viable in all types of culture media Reducing the level of activity of the cells is similar in flight samples and the laboratory strain Strain S. oneidensis MR- 1 can be used in the microbial fuel cell while conducting experiments on board the spacecraft

Mek1 Down Regulates Rad51 Activity during Yeast Meiosis by Phosphorylation of Hed1.

PubMed

Callender, Tracy L; Laureau, Raphaelle; Wan, Lihong; Chen, Xiangyu; Sandhu, Rima; Laljee, Saif; Zhou, Sai; Suhandynata, Ray T; Prugar, Evelyn; Gaines, William A; Kwon, YoungHo; Börner, G Valentin; Nicolas, Alain; Neiman, Aaron M; Hollingsworth, Nancy M

2016-08-01

During meiosis, programmed double strand breaks (DSBs) are repaired preferentially between homologs to generate crossovers that promote proper chromosome segregation at Meiosis I. In many organisms, there are two strand exchange proteins, Rad51 and the meiosis-specific Dmc1, required for interhomolog (IH) bias. This bias requires the presence, but not the strand exchange activity of Rad51, while Dmc1 is responsible for the bulk of meiotic recombination. How these activities are regulated is less well established. In dmc1Δ mutants, Rad51 is actively inhibited, thereby resulting in prophase arrest due to unrepaired DSBs triggering the meiotic recombination checkpoint. This inhibition is dependent upon the meiosis-specific kinase Mek1 and occurs through two different mechanisms that prevent complex formation with the Rad51 accessory factor Rad54: (i) phosphorylation of Rad54 by Mek1 and (ii) binding of Rad51 by the meiosis-specific protein Hed1. An open question has been why inhibition of Mek1 affects Hed1 repression of Rad51. This work shows that Hed1 is a direct substrate of Mek1. Phosphorylation of Hed1 at threonine 40 helps suppress Rad51 activity in dmc1Δ mutants by promoting Hed1 protein stability. Rad51-mediated recombination occurring in the absence of Hed1 phosphorylation results in a significant increase in non-exchange chromosomes despite wild-type levels of crossovers, confirming previous results indicating a defect in crossover assurance. We propose that Rad51 function in meiosis is regulated in part by the coordinated phosphorylation of Rad54 and Hed1 by Mek1.

Computational Model Prediction and Biological Validation Using Simplified Mixed Field Exposures for the Development of a GCR Reference Field

NASA Technical Reports Server (NTRS)

Hada, M.; Rhone, J.; Beitman, A.; Saganti, P.; Plante, I.; Ponomarev, A.; Slaba, T.; Patel, Z.

2018-01-01

The yield of chromosomal aberrations has been shown to increase in the lymphocytes of astronauts after long-duration missions of several months in space. Chromosome exchanges, especially translocations, are positively correlated with many cancers and are therefore a potential biomarker of cancer risk associated with radiation exposure. Although extensive studies have been carried out on the induction of chromosomal aberrations by low- and high-LET radiation in human lymphocytes, fibroblasts, and epithelial cells exposed in vitro, there is a lack of data on chromosome aberrations induced by low dose-rate chronic exposure and mixed field beams such as those expected in space. Chromosome aberration studies at NSRL will provide the biological validation needed to extend the computational models over a broader range of experimental conditions (more complicated mixed fields leading up to the galactic cosmic rays (GCR) simulator), helping to reduce uncertainties in radiation quality effects and dose-rate dependence in cancer risk models. These models can then be used to answer some of the open questions regarding requirements for a full GCR reference field, including particle type and number, energy, dose rate, and delivery order. In this study, we designed a simplified mixed field beam with a combination of proton, helium, oxygen, and iron ions with shielding or proton, helium, oxygen, and titanium without shielding. Human fibroblasts cells were irradiated with these mixed field beam as well as each single beam with acute and chronic dose rate, and chromosome aberrations (CA) were measured with 3-color fluorescent in situ hybridization (FISH) chromosome painting methods. Frequency and type of CA induced with acute dose rate and chronic dose rates with single and mixed field beam will be discussed. A computational chromosome and radiation-induced DNA damage model, BDSTRACKS (Biological Damage by Stochastic Tracks), was updated to simulate various types of CA induced by acute exposures of the mixed field beams used for the experiments. The chromosomes were simulated by a polymer random walk algorithm with restrictions to their respective domains in the nucleus [1]. The stochastic dose to the nucleus was calculated with the code RITRACKS [2]. Irradiation of a target volume by a mixed field of ions was implemented within RITRACKs, and the fields of ions can be delivered over specific periods of time, allowing the simulation of dose-rate effects. Similarly, particles of various types and energies extracted from a pre-calculated spectra of galactic cosmic rays (GCR) can be used in RITRACKS. The number and spatial location of DSBs (DNA double-strand breaks) were calculated in BDSTRACKS using the simulated chromosomes and local (voxel) dose. Assuming that DSBs led to chromosome breaks, and simulating the rejoining of damaged chromosomes occurring during repair, BDSTRACKS produces the yield of various types of chromosome aberrations as a function of time (only final yields are presented). A comparison between experimental and simulation results will be shown.

Diploid yeast cells yield homozygous spontaneous mutations

NASA Technical Reports Server (NTRS)

Esposito, M. S.; Bruschi, C. V.; Brushi, C. V. (Principal Investigator)

1993-01-01

A leucine-requiring hybrid of Saccharomyces cerevisiae, homoallelic at the LEU1 locus (leu1-12/leu1-12) and heterozygous for three chromosome-VII genetic markers distal to the LEU1 locus, was employed to inquire: (1) whether spontaneous gene mutation and mitotic segregation of heterozygous markers occur in positive nonrandom association and (2) whether homozygous LEU1/LEU1 mutant diploids are generated. The results demonstrate that gene mutation of leu1-12 to LEU1 and mitotic segregation of heterozygous chromosome-VII markers occur in strong positive nonrandom association, suggesting that the stimulatory DNA lesion is both mutagenic and recombinogenic. In addition, genetic analysis of diploid Leu+ revertants revealed that approximately 3% of mutations of leu1-12 to LEU1 result in LEU1/LEU1 homozygotes. Red-white sectored Leu+ colonies exhibit genotypes that implicate post-replicational chromatid breakage and exchange near the site of leu1-12 reversion, chromosome loss, and subsequent restitution of diploidy, in the sequence of events leading to mutational homozygosis. By analogy, diploid cell populations can yield variants homozygous for novel recessive gene mutations at biologically significant rates. Mutational homozygosis may be relevant to both carcinogenesis and the evolution of asexual diploid organisms.

Linear Streptomyces plasmids form superhelical circles through interactions between their terminal proteins

PubMed Central

Tsai, Hsiu-Hui; Huang, Chih-Hung; Tessmer, Ingrid; Erie, Dorothy A.; Chen, Carton W.

2011-01-01

Linear chromosomes and linear plasmids of Streptomyces possess covalently bound terminal proteins (TPs) at the 5′ ends of their telomeres. These TPs are proposed to act as primers for DNA synthesis that patches the single-stranded gaps at the 3′ ends during replication. Most (‘archetypal’) Streptomyces TPs (designated Tpg) are highly conserved in size and sequence. In addition, there are a number of atypical TPs with heterologous sequences and sizes, one of which is Tpc that caps SCP1 plasmid of Streptomyces coelicolor. Interactions between the TPs on the linear Streptomyces replicons have been suggested by electrophoretic behaviors of TP-capped DNA and circular genetic maps of Streptomyces chromosomes. Using chemical cross-linking, we demonstrated intramolecular and intermolecular interactions in vivo between Tpgs, between Tpcs and between Tpg and Tpc. Interactions between the chromosomal and plasmid telomeres were also detected in vivo. The intramolecular telomere interactions produced negative superhelicity in the linear DNA, which was relaxed by topoisomerase I. Such intramolecular association between the TPs poses a post-replicational complication in the formation of a pseudo-dimeric structure that requires resolution by exchanging TPs or DNA. PMID:21109537

Generalized species sampling priors with latent Beta reinforcements

PubMed Central

Airoldi, Edoardo M.; Costa, Thiago; Bassetti, Federico; Leisen, Fabrizio; Guindani, Michele

2014-01-01

Many popular Bayesian nonparametric priors can be characterized in terms of exchangeable species sampling sequences. However, in some applications, exchangeability may not be appropriate. We introduce a novel and probabilistically coherent family of non-exchangeable species sampling sequences characterized by a tractable predictive probability function with weights driven by a sequence of independent Beta random variables. We compare their theoretical clustering properties with those of the Dirichlet Process and the two parameters Poisson-Dirichlet process. The proposed construction provides a complete characterization of the joint process, differently from existing work. We then propose the use of such process as prior distribution in a hierarchical Bayes modeling framework, and we describe a Markov Chain Monte Carlo sampler for posterior inference. We evaluate the performance of the prior and the robustness of the resulting inference in a simulation study, providing a comparison with popular Dirichlet Processes mixtures and Hidden Markov Models. Finally, we develop an application to the detection of chromosomal aberrations in breast cancer by leveraging array CGH data. PMID:25870462

Comparison of F ratios generated from interphase and metaphase chromosome damage induced by high doses of low- and high-LET radiation

NASA Technical Reports Server (NTRS)

Wu, H.; George, K.; Willingham, V.; Kawata, T.; Cucinotta, F. A.

2001-01-01

Although biophysical models predict a difference in the ratio of interchromosomal to intrachromosomal interarm exchanges (F ratio) for low- and high-LET radiations, few experimental data support this prediction. However, the F ratios in experiments to date have been generated using data on chromosome aberrations in samples collected at the first postirradiation mitosis, which may not be indicative of the aberrations formed in interphase after exposure to high-LET radiations. In the present study, we exposed human lymphocytes in vitro to 2 and 5 Gy of gamma rays and 3 Gy of 1 GeV/nucleon iron ions (LET = 140 keV/micrometer), stimulated the cells to grow with phytohemagglutinin (PHA), and collected the condensed chromosomes after 48 h of incubation using both chemically induced premature chromosome condensation (PCC) and the conventional metaphase techniques. The PCC technique used here condenses chromosomes mostly in the G(2) phase of the cell cycle. The F ratio was calculated using data on asymmetrical chromosome aberrations in both the PCC and metaphase samples. It was found that the F ratios were similar for the samples irradiated with low- and high-LET radiation and collected at metaphase. However, for irradiated samples assayed by PCC, the F ratio was found to be 8.2 +/- 2.0 for 5 Gy gamma rays and 5.2 +/- 0.9 for 3 Gy iron ions. The distribution of the aberrations indicated that, in the PCC samples irradiated with iron ions, most of the centric rings occurred in spreads containing five or more asymmetrical aberrations. These heavily damaged cells, which were either less likely to reach mitosis or may reach mitosis at a later time, were responsible for the difference in the F ratios generated from interphase and metaphase analysis after exposure to iron ions.

Effect of americium-241 alpha-particles on the dose-response of chromosome aberrations in human lymphocytes analysed by fluorescence in situ hybridization.

PubMed

Barquinero, J F; Stephan, G; Schmid, E

2004-02-01

To evaluate by the fluorescent in-situ hybridization (FISH) technique the dose-response and intercellular distribution of alpha-particle-induced chromosome aberrations. In particular, the validity of using the yield of characteristic types of chromosome abnormalities in stable cells as quantitative indicators for retrospective dose reconstruction has been evaluated. Monolayers of human peripheral lymphocytes were exposed at doses from 0.02 to 1 Gy to alpha-particles emitted from a source of americium-241. The most probable energy of the alpha-particles entering the cells was 2.7 MeV. FISH painting was performed using DNA probes for chromosomes 2, 4 and 8 in combination with a pan-centromeric probe. In complete first-division cells, identified by harlequin staining, aberrations involving painted target chromosomal material were recorded as well as aberrations involving only unpainted chromosomal material. In total, the percentage of complex aberrations was about 35% and no dose dependence was observed. When complex-type exchanges were reduced to simple base types, the different cell distributions were clearly over-dispersed, and the linear coefficients of the dose-effect curves for translocations were significantly higher than for dicentrics. For past dose reconstruction, only a few complex aberrations were in stable cells. The linear coefficient obtained for transmissible aberrations in stable cells was more than seven times lower than that obtained in all analysed cells, i.e. including unstable cells. FISH-based analysis of complex rearrangements allows discrimination between partial-body exposures to low-linear energy transfer radiation and high-linear energy transfer exposures. In assessing past or chronic exposure to alpha-particles, the use of a dose-effect curve obtained by FISH-based translocation data, which had not excluded data determined in unstable cells, would underestimate the dose. Insertions are ineffective biomarkers because their frequency is too low.

The Transposon Galileo Generates Natural Chromosomal Inversions in Drosophila by Ectopic Recombination

PubMed Central

Delprat, Alejandra; Ruiz, Alfredo

2009-01-01

Background Transposable elements (TEs) are responsible for the generation of chromosomal inversions in several groups of organisms. However, in Drosophila and other Dipterans, where inversions are abundant both as intraspecific polymorphisms and interspecific fixed differences, the evidence for a role of TEs is scarce. Previous work revealed that the transposon Galileo was involved in the generation of two polymorphic inversions of Drosophila buzzatii. Methodology/Principal Findings To assess the impact of TEs in Drosophila chromosomal evolution and shed light on the mechanism involved, we isolated and sequenced the two breakpoints of another widespread polymorphic inversion from D. buzzatii, 2z 3. In the non inverted chromosome, the 2z 3 distal breakpoint was located between genes CG2046 and CG10326 whereas the proximal breakpoint lies between two novel genes that we have named Dlh and Mdp. In the inverted chromosome, the analysis of the breakpoint sequences revealed relatively large insertions (2,870-bp and 4,786-bp long) including two copies of the transposon Galileo (subfamily Newton), one at each breakpoint, plus several other TEs. The two Galileo copies: (i) are inserted in opposite orientation; (ii) present exchanged target site duplications; and (iii) are both chimeric. Conclusions/Significance Our observations provide the best evidence gathered so far for the role of TEs in the generation of Drosophila inversions. In addition, they show unequivocally that ectopic recombination is the causative mechanism. The fact that the three polymorphic D. buzzatii inversions investigated so far were generated by the same transposon family is remarkable and is conceivably due to Galileo's unusual structure and current (or recent) transpositional activity. PMID:19936241

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

Ortiz, Rosario, E-mail: r_oh@ciencias.unam.mx; Kouznetsova, Anna, E-mail: Anna.Kouznetsova@ki.se; Echeverría-Martínez, Olga M., E-mail: omem@ciencias.unam.mx

The synaptonemal complex (SC) is a proteinaceous structure that holds the homologous chromosomes in close proximity while they exchange genetic material in a process known as meiotic recombination. This meiotic recombination leads to genetic variability in sexually reproducing organisms. The ultrastructure of the SC is studied by electron microscopy and it is observed as a tripartite structure. Two lateral elements (LE) separated by a central region (CR) confer its classical tripartite organization. The LEs are the anchoring platform for the replicated homologous chromosomes to properly exchange genetic material with one another. An accurate assembly of the LE is indispensable formore » the proper completion of meiosis. Ultrastructural studies suggested that the LE is organized as a multilayered unit. However, no validation of this model has been previously provided. In this ultrastructural study, by using mice with different genetic backgrounds that affect the LE width, we provide further evidence that support a multilayered organization of the LE. Additionally, we provide data suggesting additional roles of the different cohesin complex components in the structure of the LEs of the SC. - Highlights: • The lateral element of the synaptonemal complex is a multilayered structure. • The width of the lateral element in synaptonemal complex-null mice is different. • Two cohesin complex cores plus one axial element form a wild-type lateral element. • The layers of the lateral element can be analyzed in different null mice models.« less

Homologous Recombination—Experimental Systems, Analysis and Significance

PubMed Central

Kuzminov, Andrei

2014-01-01

Homologous recombination is the most complex of all recombination events that shape genomes and produce material for evolution. Homologous recombination events are exchanges between DNA molecules in the lengthy regions of shared identity, catalyzed by a group of dedicated enzymes. There is a variety of experimental systems in E. coli and Salmonella to detect homologous recombination events of several different kinds. Genetic analysis of homologous recombination reveals three separate phases of this process: pre-synapsis (the early phase), synapsis (homologous strand exchange) and post-synapsis (the late phase). In E. coli, there are at least two independent pathway of the early phase and at least two independent pathways of the late phase. All this complexity is incongruent with the originally ascribed role of homologous recombination as accelerator of genome evolution: there is simply not enough duplication and repetition in enterobacterial genomes for homologous recombination to have a detectable evolutionary role, and therefore not enough selection to maintain such a complexity. At the same time, the mechanisms of homologous recombination are uniquely suited for repair of complex DNA lesions called chromosomal lesions. In fact, the two major classes of chromosomal lesions are recognized and processed by the two individual pathways at the early phase of homologous recombination. It follows, therefore, that homologous recombination events are occasional reflections of the continual recombinational repair, made possible in cases of natural or artificial genome redundancy. PMID:26442506

Microsatellite and HLA class II oligonucleotide typing in a population of Yanomami Indians.

PubMed

Roewer, L; Nagy, M; Schmidt, P; Epplen, J T; Herzog-Schröder, G

1993-01-01

We have used three different microsatellites (on chromosome 12 and Y) together with HLA class II oligonucleotide typing (DQA and DQB) to analyze families of Yanomami indians settling in villages in Southern Venezuela. There exist complex networks of biological relationship between villages as a result of wife exchange, village fissioning and changing patterns of alliances associated with inter-village warfare. Social status in this society is largely determined by the kinship system. Polygyny is common, especially among headmen, with additional wives, frequently being chosen among the sisters of the first wife. Our preliminary results mainly obtained from inhabitants of the village HAP show the expected allele distribution in populations with a high degree of consanguinity: (i) deficiency of observed heterozygotes at the autosomal loci and (ii) almost all men carry the same Y chromosomal allele. Nevertheless in the Yanomami village two thirds of the described autosomal microsatellite alleles were identified. Several paternities were clarified.

Unequal crossing-over associated with asymmetrical synapsis between nomadic elements in the Drosophila melanogaster genome

PubMed Central

Goldberg, Michael L.; Sheen, Jenq-Yunn; Gehring, Walter J.; Green, M. M.

1983-01-01

The molecular structure of reciprocal duplications and deficiencies produced by unequal crossing-over at the white (w) locus of Drosophila melanogaster females heterozygous for the alleles wa and wa4 has been examined. A transposable, copia-like element is found at the rearrangement breakpoints. Further characterization indicates that asymmetrical pairing between two copies of this element, which are at least 60 kilobases apart in the parental chromosomes, followed by a crossover within the paired elements, is responsible for the duplication and deficiencies observed. The frequency of these events is high compared with normal homologous exchange, implying that synaptic pairing during meiosis must be sufficiently flexible as to allow efficient recognition of sequences located in nonidentical positions on homologous chromosomes. These results suggest a possible mechanism for the generation of tandem duplications in eukaryotic organisms. Images PMID:16593354

An Overview of the Molecular Mechanisms of Recombinational DNA Repair

PubMed Central

Kowalczykowski, Stephen C.

2015-01-01

Recombinational DNA repair is a universal aspect of DNA metabolism and is essential for genomic integrity. It is a template-directed process that uses a second chromosomal copy (sister, daughter, or homolog) to ensure proper repair of broken chromosomes. The key steps of recombination are conserved from phage through human, and an overview of those steps is provided in this review. The first step is resection by helicases and nucleases to produce single-stranded DNA (ssDNA) that defines the homologous locus. The ssDNA is a scaffold for assembly of the RecA/RAD51 filament, which promotes the homology search. On finding homology, the nucleoprotein filament catalyzes exchange of DNA strands to form a joint molecule. Recombination is controlled by regulating the fate of both RecA/RAD51 filaments and DNA pairing intermediates. Finally, intermediates that mature into Holliday structures are disjoined by either nucleolytic resolution or topological dissolution. PMID:26525148

Effect of betel chewing on the frequency of sister chromatid exchanges in pregnant women and women using oral contraceptives.

PubMed

Ghosh, P K; Ghosh, R

1988-06-01

The incidence of sister chromatid exchange (SCE) was investigated in the lymphocyte chromosomes of betel chewing and non-chewing normal women, pregnant women, and women using oral contraceptives. The frequency of SCE was found to be 7.82 +/- 0.24 and 8.27 +/- 0.27 in non-chewing pregnant women and women using oral contraceptives respectively, which were significantly higher than the mean value of 5.21 +/- 0.18 observed in non-chewing normal women. Betel chewing induced higher SCE in pregnant women and women using oral contraceptives, the frequencies being 11.79 +/- 0.38 and 12.51 +/- 0.44, respectively, which were significantly higher than the SCE frequency of 6.28 +/- 0.21 found in normal betel chewing females.

Chromosomal transfers in mycoplasmas: when minimal genomes go mobile.

PubMed

Dordet-Frisoni, Emilie; Sagné, Eveline; Baranowski, Eric; Breton, Marc; Nouvel, Laurent Xavier; Blanchard, Alain; Marenda, Marc Serge; Tardy, Florence; Sirand-Pugnet, Pascal; Citti, Christine

2014-11-25

Horizontal gene transfer (HGT) is a main driving force of bacterial evolution and innovation. This phenomenon was long thought to be marginal in mycoplasmas, a large group of self-replicating bacteria characterized by minute genomes as a result of successive gene losses during evolution. Recent comparative genomic analyses challenged this paradigm, but the occurrence of chromosomal exchanges had never been formally addressed in mycoplasmas. Here, we demonstrated the conjugal transfer of large chromosomal regions within and among ruminant mycoplasma species, with the incorporation of the incoming DNA occurring by homologous recombination into the recipient chromosome. By combining classical mating experiments with high-throughput next-generation sequencing, we documented the transfer of almost every position of the mycoplasma chromosome. Mycoplasma conjugation relies on the occurrence of an integrative conjugative element (ICE) in at least one parent cell. While ICE propagates horizontally from ICE-positive to ICE-negative cells, chromosomal transfers (CTs) occurred in the opposite direction, from ICE-negative to ICE-positive cells, independently of ICE movement. These findings challenged the classical mechanisms proposed for other bacteria in which conjugative CTs are driven by conjugative elements, bringing into the spotlight a new means for rapid mycoplasma innovation. Overall, they radically change our current views concerning the evolution of mycoplasmas, with particularly far-reaching implications given that over 50 species are human or animal pathogens. Horizontal gene transfers (HGT) shape bacterial genomes and are key contributors to microbial diversity and innovation. One main mechanism involves conjugation, a process that allows the simultaneous transfer of significant amounts of DNA upon cell-to-cell contact. Recognizing and deciphering conjugal mechanisms are thus essential in understanding the impact of gene flux on bacterial evolution. We addressed this issue in mycoplasmas, the smallest and simplest self-replicating bacteria. In these organisms, HGT was long thought to be marginal. We showed here that nearly every position of the Mycoplasma agalactiae chromosome could be transferred via conjugation, using an unconventional mechanism. The transfer involved DNA blocks containing up to 80 genes that were incorporated into the host chromosome by homologous recombination. These findings radically change our views concerning mycoplasma evolution and adaptation with particularly far-reaching implications given that over 50 species are human or animal pathogens. Copyright © 2014 Dordet-Frisoni et al.

Activation of the Lbc Rho Exchange Factor Proto-Oncogene by Truncation of an Extended C Terminus That Regulates Transformation and Targeting

PubMed Central

Sterpetti, Paola; Hack, Andrew A.; Bashar, Mariam P.; Park, Brian; Cheng, Sou-De; Knoll, Joan H. M.; Urano, Takeshi; Feig, Larry A.; Toksoz, Deniz

1999-01-01

The human lbc oncogene product is a guanine nucleotide exchange factor that specifically activates the Rho small GTP binding protein, thus resulting in biologically active, GTP-bound Rho, which in turn mediates actin cytoskeletal reorganization, gene transcription, and entry into the mitotic S phase. In order to elucidate the mechanism of onco-Lbc transformation, here we report that while proto- and onco-lbc cDNAs encode identical N-terminal dbl oncogene homology (DH) and pleckstrin homology (PH) domains, proto-Lbc encodes a novel C terminus absent in the oncoprotein that includes a predicted α-helical region homologous to cyto-matrix proteins, followed by a proline-rich region. The lbc proto-oncogene maps to chromosome 15, and onco-lbc represents a fusion of the lbc proto-oncogene N terminus with a short, unrelated C-terminal sequence from chromosome 7. Both onco- and proto-Lbc can promote formation of GTP-bound Rho in vivo. Proto-Lbc transforming activity is much reduced compared to that of onco-Lbc, and a significant increase in transforming activity requires truncation of both the α-helical and proline-rich regions in the proto-Lbc C terminus. Deletion of the chromosome 7-derived C terminus of onco-Lbc does not destroy transforming activity, demonstrating that it is loss of the proto-Lbc C terminus, rather than gain of an unrelated C-terminus by onco-Lbc, that confers transforming activity. Mutations of onco-Lbc DH and PH domains demonstrate that both domains are necessary for full transforming activity. The proto-Lbc product localizes to the particulate (membrane) fraction, while the majority of the onco-Lbc product is cytosolic, and mutations of the PH domain do not affect this localization. The proto-Lbc C-terminus alone localizes predominantly to the particulate fraction, indicating that the C terminus may play a major role in the correct subcellular localization of proto-Lbc, thus providing a mechanism for regulating Lbc oncogenic potential. PMID:9891067

Networking in microbes: conjugative elements and plasmids in the genus Alteromonas.

PubMed

López-Pérez, Mario; Ramon-Marco, Nieves; Rodriguez-Valera, Francisco

2017-01-05

To develop evolutionary models for the free living bacterium Alteromonas the genome sequences of isolates of the genus have been extensively analyzed. However, the main genetic exchange drivers in these microbes, conjugative elements (CEs), have not been considered in detail thus far. In this work, CEs have been searched in several complete Alteromonas genomes and their sequence studied to understand their role in the evolution of this genus. Six genomes are reported here for the first time. We have found nine different plasmids of sizes ranging from 85 to 600 Kb, most of them were found in a single strain. Networks of gene similarity could be established among six of the plasmids that were also connected with another cluster of plasmids found in Shewanella strains. The cargo genes found in these plasmids included cassettes found before in chromosome flexible genomic islands of Alteromonas strains. We describe also the plasmids pAMCP48-600 and pAMCP49-600, the largest found in Alteromonas thus far (ca. 600 Kb) and containing all the hallmarks to be classified as chromids. We found in them some housekeeping genes and a cluster that code for an exocellular polysaccharide. They could represent the transport vectors for the previously described replacement flexible genomic islands. Integrative and conjugative elements (ICEs) were more common than plasmids and showed similar patterns of variation with cargo genes coding for components of additive flexible genomic islands. A nearly identical ICE was found in A. mediterranea MED64 and Vibrio cholera AHV1003 isolated from a human pathogen, indicating the potential exchange of these genes across phylogenetic distances exceeding the family threshold. We have seen evidence of how CEs can be vectors to transfer gene cassettes acquired in the chromosomal flexible genomic islands, both of the additive and replacement kind. These CEs showed evidence of how genetic material is exchanged among members of the same species but also (albeit less frequently) across genus and family barriers. These gradients of exchange frequency are probably one of the main drivers of species origin and maintenance in prokaryotes and also provide these taxa with large genetic diversity.

In vitro studies on chemoprotective effect of Purnark against benzo(a)pyrene-induced chromosomal damage in human lymphocytes.

PubMed

Ghaisas, S D; Bhide, S V

1994-01-01

Human lymphocytes were used as an assay system to test chemopreventive activity of natural products. Purnark, a mixture of extracts of turmeric, betel leaf and catechu, was tested for its chemoprotective activity against BP induced DNA damage. Sister chromatid exchange and micronuclei were used as markers to assess the protective activity of Purnark. Purnark gave 50-60% protection against BP induced SCEs and micronuclei. Purnark at 100 micrograms dose did not show any genotoxicity.

Genetic exchange of fimbrial alleles exemplifies the adaptive virulence strategy of Porphyromonas gingivalis.

PubMed

Kerr, Jennifer E; Abramian, Jared R; Dao, Doan-Hieu V; Rigney, Todd W; Fritz, Jamie; Pham, Tan; Gay, Isabel; Parthasarathy, Kavitha; Wang, Bing-yan; Zhang, Wenjian; Tribble, Gena D

2014-01-01

Porphyromonas gingivalis is a gram-negative anaerobic bacterium, a member of the human oral microbiome, and a proposed "keystone" pathogen in the development of chronic periodontitis, an inflammatory disease of the gingiva. P. gingivalis is a genetically diverse species, and is able to exchange chromosomal DNA between strains by natural competence and conjugation. In this study, we investigate the role of horizontal DNA transfer as an adaptive process to modify behavior, using the major fimbriae as our model system, due to their critical role in mediating interactions with the host environment. We show that P. gingivalis is able to exchange fimbrial allele types I and IV into four distinct strain backgrounds via natural competence. In all recombinants, we detected a complete exchange of the entire fimA allele, and the rate of exchange varies between the different strain backgrounds. In addition, gene exchange within other regions of the fimbrial genetic locus was identified. To measure the biological implications of these allele swaps we compared three genotypes of fimA in an isogenic background, strain ATCC 33277. We demonstrate that exchange of fimbrial allele type results in profound phenotypic changes, including the quantity of fimbriae elaborated, membrane blebbing, auto-aggregation and other virulence-associated phenotypes. Replacement of the type I allele with either the type III or IV allele resulted in increased invasion of gingival fibroblast cells relative to the isogenic parent strain. While genetic variability is known to impact host-microbiome interactions, this is the first study to quantitatively assess the adaptive effect of exchanging genes within the pan genome cloud. This is significant as it presents a potential mechanism by which opportunistic pathogens may acquire the traits necessary to modify host-microbial interactions.

Telomere sister chromatid exchange in telomerase deficient murine cells.

PubMed

Wang, Yisong; Giannone, Richard J; Liu, Yie

2005-10-01

We have recently demonstrated that several types of genomic rearrangements (i.e., telomere sister chromatid exchange (T-SCE), genomic-SCE, or end-to-end fusions) were more often detected in long-term cultured murine telomerase deficient embryonic stem (ES) cells than in freshly prepared murine splenocytes, even through they possessed similar frequencies of critically short telomeres. The high rate of genomic rearrangements in telomerase deficient ES cells, when compared to murine splenocytes, may reflect the cultured cells' gained ability to protect chromosome ends with eroded telomeres allowing them to escape "end crisis". However, the possibility that ES cells were more permissive to genomic rearrangements than other cell types or that differences in the microenvironment or genetic background of the animals might consequentially determine the rate of T-SCEs or other genomic rearrangements at critically short telomeres could not be ruled out.

[Molecular variability in the commom shrew Sorex araneus L. from European Russia and Siberia inferred from the length polymorphism of DNA regions flanked by short interspersed elements (Inter-SINE PCR) and the relationships between the Moscow and Seliger chromosome races].

PubMed

Bannikova, A A; Bulatova, N Sh; Kramerov, D A

2006-06-01

Genetic exchange among chromosomal races of the common shrew Sorex araneus and the problem of reproductive barriers have been extensively studied by means of such molecular markers as mtDNA, microsatellites, and allozymes. In the present study, the interpopulation and interracial polymorphism in the common shrew was derived, using fingerprints generated by amplified DNA regions flanked by short interspersed repeats (SINEs)-interSINE PCR (IS-PCR). We used primers, complementary to consensus sequences of two short retroposons: mammalian element MIR and the SOR element from the genome of Sorex araneus. Genetic differentiation among eleven populations of the common shrew from eight chromosome races was estimated. The NP and MJ analyses, as well as multidimensional scaling showed that all samples examined grouped into two main clusters, corresponding to European Russia and Siberia. The bootstrap support of the European Russia cluster in the NJ and MP analyses was respectively 76 and 61%. The bootstrap index for the Siberian cluster was 100% in both analyses; the Tomsk race, included into this cluster, was separated with the bootstrap support of NJ/MP 92/95%.

The complete nucleotide sequences of the five genetically distinct plastid genomes of Oenothera, subsection Oenothera: I. sequence evaluation and plastome evolution.

PubMed

Greiner, Stephan; Wang, Xi; Rauwolf, Uwe; Silber, Martina V; Mayer, Klaus; Meurer, Jörg; Haberer, Georg; Herrmann, Reinhold G

2008-04-01

The flowering plant genus Oenothera is uniquely suited for studying molecular mechanisms of speciation. It assembles an intriguing combination of genetic features, including permanent translocation heterozygosity, biparental transmission of plastids, and a general interfertility of well-defined species. This allows an exchange of plastids and nuclei between species often resulting in plastome-genome incompatibility. For evaluation of its molecular determinants we present the complete nucleotide sequences of the five basic, genetically distinguishable plastid chromosomes of subsection Oenothera (=Euoenothera) of the genus, which are associated in distinct combinations with six basic genomes. Sizes of the chromosomes range from 163 365 bp (plastome IV) to 165 728 bp (plastome I), display between 96.3% and 98.6% sequence similarity and encode a total of 113 unique genes. Plastome diversification is caused by an abundance of nucleotide substitutions, small insertions, deletions and repetitions. The five plastomes deviate from the general ancestral design of plastid chromosomes of vascular plants by a subsection-specific 56 kb inversion within the large single-copy segment. This inversion disrupted operon structures and predates the divergence of the subsection presumably 1 My ago. Phylogenetic relationships suggest plastomes I-III in one clade, while plastome IV appears to be closest to the common ancestor.

The complete nucleotide sequences of the five genetically distinct plastid genomes of Oenothera, subsection Oenothera: I. Sequence evaluation and plastome evolution†

PubMed Central

Greiner, Stephan; Wang, Xi; Rauwolf, Uwe; Silber, Martina V.; Mayer, Klaus; Meurer, Jörg; Haberer, Georg; Herrmann, Reinhold G.

2008-01-01

The flowering plant genus Oenothera is uniquely suited for studying molecular mechanisms of speciation. It assembles an intriguing combination of genetic features, including permanent translocation heterozygosity, biparental transmission of plastids, and a general interfertility of well-defined species. This allows an exchange of plastids and nuclei between species often resulting in plastome–genome incompatibility. For evaluation of its molecular determinants we present the complete nucleotide sequences of the five basic, genetically distinguishable plastid chromosomes of subsection Oenothera (=Euoenothera) of the genus, which are associated in distinct combinations with six basic genomes. Sizes of the chromosomes range from 163 365 bp (plastome IV) to 165 728 bp (plastome I), display between 96.3% and 98.6% sequence similarity and encode a total of 113 unique genes. Plastome diversification is caused by an abundance of nucleotide substitutions, small insertions, deletions and repetitions. The five plastomes deviate from the general ancestral design of plastid chromosomes of vascular plants by a subsection-specific 56 kb inversion within the large single-copy segment. This inversion disrupted operon structures and predates the divergence of the subsection presumably 1 My ago. Phylogenetic relationships suggest plastomes I–III in one clade, while plastome IV appears to be closest to the common ancestor. PMID:18299283

Rejoining and misrejoining of radiation-induced chromatin breaks. II. Biophysical Model

NASA Technical Reports Server (NTRS)

Wu, H.; Durante, M.; George, K.; Goodwin, E. H.; Yang, T. C.

1996-01-01

A biophysical model for the kinetics of the formation of radiation-induced chromosome aberrations is developed to account for the recent experimental results obtained with a combination of the premature chromosome condensation (PCC) and fluorescence in situ hybridization (FISH) techniques. In this model, we consider the broken ends of DNA double-strand breaks (DSBs) to be reactant and make use of the interaction distance hypothesis. The repair/misrepair process between broken ends is suggested to consist of two steps; the first step represents the two break ends approaching each other, and the second step represents the enzymatic processes leading to DNA end-to-end rejoining. Only the second step is reflected in the kinetics observed in experiments using PCC. The model appears to be able to fit existing data for human cells. It is shown that the kinetics of the formation of chromosome aberrations can be explained by a single rate that characterizes both rejoining and misrejoining of DSBs, suggesting that repair and misrepair share the same mechanism. Fast repair (completed in minutes) in a subset of DSBs is suggested as an explanation of the complete exchanges observed with PCC in human lymphocytes immediately after irradiation. The fast repair component seems to be absent in human fibroblasts.

RPA homologs and ssDNA processing during meiotic recombination.

PubMed

Ribeiro, Jonathan; Abby, Emilie; Livera, Gabriel; Martini, Emmanuelle

2016-06-01

Meiotic homologous recombination is a specialized process that involves homologous chromosome pairing and strand exchange to guarantee proper chromosome segregation and genetic diversity. The formation and repair of DNA double-strand breaks (DSBs) during meiotic recombination differs from those during mitotic recombination in that the homologous chromosome rather than the sister chromatid is the preferred repair template. The processing of single-stranded DNA (ssDNA) formed on intermediate recombination structures is central to driving the specific outcomes of DSB repair during meiosis. Replication protein A (RPA) is the main ssDNA-binding protein complex involved in DNA metabolism. However, the existence of RPA orthologs in plants and the recent discovery of meiosis specific with OB domains (MEIOB), a widely conserved meiosis-specific RPA1 paralog, strongly suggest that multiple RPA complexes evolved and specialized to subdivide their roles during DNA metabolism. Here we review ssDNA formation and maturation during mitotic and meiotic recombination underlying the meiotic specific features. We describe and discuss the existence and properties of MEIOB and multiple RPA subunits in plants and highlight how they can provide meiosis-specific fates to ssDNA processing during homologous recombination. Understanding the functions of these RPA homologs and how they interact with the canonical RPA subunits is of major interest in the fields of meiosis and DNA repair.

Rejoining of isochromatid breaks induced by heavy ions in G2-phase normal human fibroblasts

NASA Technical Reports Server (NTRS)

Kawata, T.; Durante, M.; Furusawa, Y.; George, K.; Ito, H.; Wu, H.; Cucinotta, F. A.

2001-01-01

We reported previously that exposure of normal human fibroblasts in G2 phase of the cell cycle to high-LET radiation produces a much higher frequency of isochromatid breaks than exposure to gamma rays. We concluded that an increase in the production of isochromatid breaks is a signature of initial high-LET radiation-induced G2-phase damage. In this paper, we report the repair kinetics of isochromatid breaks induced by high-LET radiation in normal G2-phase human fibroblasts. Exponentially growing human fibroblasts (AG1522) were irradiated with gamma rays or energetic carbon (290 MeV/nucleon), silicon (490 MeV/nucleon), or iron (200 MeV/nucleon) ions. Prematurely condensed chromosomes were induced by calyculin A after different postirradiation incubation times ranging from 0 to 600 min. Chromosomes were stained with Giemsa, and aberrations were scored in cells at G2 phase. G2-phase fragments, the result of the induction of isochromatid breaks, decreased quickly with incubation time. The curve for the kinetics of the rejoining of chromatid-type breaks showed a slight upward curvature with time after exposure to 440 keV/microm iron particles, probably due to isochromatid-isochromatid break rejoining. The formation of chromatid exchanges after exposure to high-LET radiation therefore appears to be underestimated, because isochromatid-isochromatid exchanges cannot be detected. Increased induction of isochromatid breaks and rejoining of isochromatid breaks affect the overall kinetics of chromatid-type break rejoining after exposure to high-LET radiation.

Space Radiation Induced Cytogenetic Damage in the Blood Lymphocytes of Astronauts

NASA Technical Reports Server (NTRS)

George, K.; Cucinotta, F. A.

2008-01-01

Cytogenetic analysis of astronauts blood lymphocytes provides a direct in vivo measurement of space radiation damage, which takes into account individual radiosensitivity and considers the influence of microgravity and other stress conditions. We present our latest analyses of chromosome damage in astronauts blood lymphocytes assessed by fluorescence in situ hybridization (FISH) chromosome painting and collected at various times beginning directly after return from space to several years after flight. Dose was derived from frequencies of chromosome exchanges using preflight calibration curves, and the Relative Biological Effect (RBE) was estimated by comparison with individually measured physically absorbed doses. Values for average RBE were compared to the average quality factor (Q), from direct measurements of the lineal energy spectra using a tissue-equivalent proportional counter (TEPC) and radiation transport codes. Results prove that cytogenetic biodosimetry analyses on blood collected within a week or two of return from space provides a reliable estimate of equivalent radiation dose and risk after protracted exposure to space radiation of a few months or more. However, data collected several months or years after flight suggests that the yield of chromosome translocations may decline with time after the mission, indicating that retrospective doses may be more difficult to estimate. In addition, limited data on multiple flights show a lack of correlation between time in space and translocation yields. Data from one crewmember, who has participated in two separate long-duration space missions and has been followed up for over 10 years, provide limited information on the effect of repeat flights and show a possible adaptive response to space radiation exposure.

ATRX contributes to epigenetic asymmetry and silencing of major satellite transcripts in the maternal genome of the mouse embryo

PubMed Central

De La Fuente, Rabindranath; Baumann, Claudia; Viveiros, Maria M.

2015-01-01

A striking proportion of human cleavage-stage embryos exhibit chromosome instability (CIN). Notably, until now, no experimental model has been described to determine the origin and mechanisms of complex chromosomal rearrangements. Here, we examined mouse embryos deficient for the chromatin remodeling protein ATRX to determine the cellular mechanisms activated in response to CIN. We demonstrate that ATRX is required for silencing of major satellite transcripts in the maternal genome, where it confers epigenetic asymmetry to pericentric heterochromatin during the transition to the first mitosis. This stage is also characterized by a striking kinetochore size asymmetry established by differences in CENP-C protein between the parental genomes. Loss of ATRX results in increased centromeric mitotic recombination, a high frequency of sister chromatid exchanges and double strand DNA breaks, indicating the formation of mitotic recombination break points. ATRX-deficient embryos exhibit a twofold increase in transcripts for aurora kinase B, the centromeric cohesin ESCO2, DNMT1, the ubiquitin-ligase (DZIP3) and the histone methyl transferase (EHMT1). Thus, loss of ATRX activates a pathway that integrates epigenetic modifications and DNA repair in response to chromosome breaks. These results reveal the cellular response of the cleavage-stage embryo to CIN and uncover a mechanism by which centromeric fission induces the formation of large-scale chromosomal rearrangements. Our results have important implications to determine the epigenetic origins of CIN that lead to congenital birth defects and early pregnancy loss, as well as the mechanisms involved in the oocyte to embryo transition. PMID:25926359

Both nuclear and cytoplasmic components are defective in oocytes of the B6.Y(TIR) sex-reversed female mouse.

PubMed

Amleh, A; Smith, L; Chen, H; Taketo, T

2000-03-15

In the mammalian gonadal primordium, activation of the Sry gene on the Y chromosome initiates a cascade of genetic events leading to testicular organization whereas its absence results in ovarian differentiation. An exception occurs when the Y chromosome of Mus musculus domesticus from Tirano, Italy (Y(TIR)), is placed on the C57BL/6J (B6) genetic background. The B6.Y(TIR) progeny develop only ovaries or ovotestes despite Sry transcription in fetal life. Consequently, the XY offspring with bilateral ovaries develop into apparently normal females, but their eggs fail to develop after fertilization. Our previous studies have shown that the primary cause of infertility can be attributed to oocytes rather than their surrounding somatic cells in the XY ovary. This study attempted to identify the defects in oocytes from the B6.Y(TIR) female mouse. We examined the developmental potential of embryos from XY and XX females after exchanging their nuclear components by microsurgery following in vitro maturation and fertilization. The results suggest that both nuclear and cytoplasmic components are defective in oocytes from XY females. In the XY fetal ovary, most germ cells entered meiosis and their autosomes appeared to synapse normally while the X and Y chromosomes remained unpaired during meiotic prophase. This lack of X-Y pairing probably caused aneuploidy in some secondary oocytes following in vitro maturation. However, normal numbers of chromosomes in the rest of the secondary oocytes indicate that aneuploidy alone can not explain the nuclear defect in oocytes. Copyright 2000 Academic Press.

Identification of balanced chromosomal rearrangements previously unknown among participants in the 1000 Genomes Project: implications for interpretation of structural variation in genomes and the future of clinical cytogenetics.

PubMed

Dong, Zirui; Wang, Huilin; Chen, Haixiao; Jiang, Hui; Yuan, Jianying; Yang, Zhenjun; Wang, Wen-Jing; Xu, Fengping; Guo, Xiaosen; Cao, Ye; Zhu, Zhenzhen; Geng, Chunyu; Cheung, Wan Chee; Kwok, Yvonne K; Yang, Huanming; Leung, Tak Yeung; Morton, Cynthia C; Cheung, Sau Wai; Choy, Kwong Wai

2017-11-02

PurposeRecent studies demonstrate that whole-genome sequencing enables detection of cryptic rearrangements in apparently balanced chromosomal rearrangements (also known as balanced chromosomal abnormalities, BCAs) previously identified by conventional cytogenetic methods. We aimed to assess our analytical tool for detecting BCAs in the 1000 Genomes Project without knowing which bands were affected.MethodsThe 1000 Genomes Project provides an unprecedented integrated map of structural variants in phenotypically normal subjects, but there is no information on potential inclusion of subjects with apparent BCAs akin to those traditionally detected in diagnostic cytogenetics laboratories. We applied our analytical tool to 1,166 genomes from the 1000 Genomes Project with sufficient physical coverage (8.25-fold).ResultsWith this approach, we detected four reciprocal balanced translocations and four inversions, ranging in size from 57.9 kb to 13.3 Mb, all of which were confirmed by cytogenetic methods and polymerase chain reaction studies. One of these DNAs has a subtle translocation that is not readily identified by chromosome analysis because of the similarity of the banding patterns and size of exchanged segments, and another results in disruption of all transcripts of an OMIM gene.ConclusionOur study demonstrates the extension of utilizing low-pass whole-genome sequencing for unbiased detection of BCAs including translocations and inversions previously unknown in the 1000 Genomes Project.GENETICS in MEDICINE advance online publication, 2 November 2017; doi:10.1038/gim.2017.170.

GDP-to-GTP exchange on the microtubule end can contribute to the frequency of catastrophe

PubMed Central

Piedra, Felipe-Andrés; Kim, Tae; Garza, Emily S.; Geyer, Elisabeth A.; Burns, Alexander; Ye, Xuecheng; Rice, Luke M.

2016-01-01

Microtubules are dynamic polymers of αβ-tubulin that have essential roles in chromosome segregation and organization of the cytoplasm. Catastrophe—the switch from growing to shrinking—occurs when a microtubule loses its stabilizing GTP cap. Recent evidence indicates that the nucleotide on the microtubule end controls how tightly an incoming subunit will be bound (trans-acting GTP), but most current models do not incorporate this information. We implemented trans-acting GTP into a computational model for microtubule dynamics. In simulations, growing microtubules often exposed terminal GDP-bound subunits without undergoing catastrophe. Transient GDP exposure on the growing plus end slowed elongation by reducing the number of favorable binding sites on the microtubule end. Slower elongation led to erosion of the GTP cap and an increase in the frequency of catastrophe. Allowing GDP-to-GTP exchange on terminal subunits in simulations mitigated these effects. Using mutant αβ-tubulin or modified GTP, we showed experimentally that a more readily exchangeable nucleotide led to less frequent catastrophe. Current models for microtubule dynamics do not account for GDP-to-GTP exchange on the growing microtubule end, so our findings provide a new way of thinking about the molecular events that initiate catastrophe. PMID:27146111

Efficient conditional and promoter-specific in vivo expression of cDNAs of choice by taking advantage of recombinase-mediated cassette exchange using FlEx gene traps

PubMed Central

Schebelle, Laura; Wolf, Claudia; Stribl, Carola; Javaheri, Tahereh; Schnütgen, Frank; Ettinger, Andreas; Ivics, Zoltán; Hansen, Jens; Ruiz, Patricia; von Melchner, Harald; Wurst, Wolfgang; Floss, Thomas

2010-01-01

Recombinase-mediated cassette exchange (RMCE) exploits the possibility to unidirectionally exchange any genetic material flanked by heterotypic recombinase recognition sites (RRS) with target sites in the genome. Due to a limited number of available pre-fabricated target sites, RMCE in mouse embryonic stem (ES) cells has not been tapped to its full potential to date. Here, we introduce a universal system, which allows the targeted insertion of any given transcriptional unit into 85 742 previously annotated retroviral conditional gene trap insertions, representing 7013 independent genes in mouse ES cells, by RMCE. This system can be used to express any given cDNA under the control of endogenous trapped promoters in vivo, as well as for the generation of transposon ‘launch pads’ for chromosomal region-specific ‘Sleeping Beauty’ insertional mutagenesis. Moreover, transcription of the gene-of-interest is only activated upon Cre-recombinase activity, a feature that adds conditionality to this expression system, which is demonstrated in vivo. The use of the RMCE system presented in this work requires one single-cloning step followed by one overnight gateway clonase reaction and subsequent cassette exchange in ES cells with efficiencies of 40% in average. PMID:20139417

A Transmissible Plasmid Controlling Camphor Oxidation in Pseudomonas putida

PubMed Central

Rheinwald, J. G.; Chakrabarty, A. M.; Gunsalus, I. C.

1973-01-01

Earlier papers demonstrated an extensive genetic exchange among fluorescent Pseudomonads; this one documents for genes specifying enzymes of peripheral dissimilation an extrachromosomal array, segregation, and frequent interstrain transfer. An hypothesis is presented of a general mechanism for the formation and maintenance of metabolic diversity. The example used, the path of oxidative cleavage of the carbocyclic rings of the bicyclic monoterpene D- and L-camphor, terminates in acetate release and isobutyrate chain debranching. By transduction, two gene linkage groups are shown for the reactions before and after isobutyrate. The group for reactions before isobutyrate is plasmid borne, contransferable by conjugation, mitomycin curable, and shows a higher segregation rate from cells that are multiplasmid rather than carrying a single plasmid. The genes that code for isobutyrate and essential anaplerotic and amphibolic metabolism are chromosomal. By conjugation plasmid-borne genes are transferred at a higher frequency than are chromosomal, and are transferred in homologous crosses more frequently than between heterologous species. Most isobutyrate-positive fluorescent pseudomonad strains will accept and express the camphor plasmid. PMID:4351810

Analysis of mutagenic activity of biohazardous organics in Kanawha River sediments. Technical completion report

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

White, A.R.; Waldron, M.C.

1988-01-01

Residual chemical contamination of Kanawha River sediments may constitute a health hazard. Sediment cores have been analyzed using a coupled bioassay/chemical fractionation procedure. Both bacterial mutagenicity and sister chromatid exchange (SCE) analyses were conducted on sediment samples. Pocatalico River sediments extracts showed no response in either bacterial mutagenicity assay or SCE assay. Extracts from Armour Creek and the Kanawha River induced mutagenicities in the presence of S9 enzymes. The same extracts produced a significant increase in human chromosomal cross-over events.

Radiation dose-response curves: cell repair mechanisms vs. ion track overlapping

NASA Astrophysics Data System (ADS)

Kowalska, Agata; Czerski, Konrad; Nasonova, Elena; Kutsalo, Polina; Krasavin, Eugen

2017-12-01

Chromosome aberrations in human lymphocytes exposed to different doses of particle radiation: 150 MeV and spread out Bragg peak proton beams, 22 MeV/u boron beam and 199 V/u carbon beam were studied. For comparison, an experiment with 60Co γ-rays was also performed. We investigated distributions of aberration frequency and the shape of dose-response curves for the total aberration yield as well as for exchange and non-exchange aberrations, separately. Applying the linear-quadratic model, we could derive a relation between the fitted parameters and the ion track radius which could explain experimentally observed curvature of the dose-response curves. The results compared with physical expectations clearly show that the biological effects of cell repair are much more important than the ion track overlapping. Contribution to the Topical Issue "Dynamics of Systems at the Nanoscale", edited by Andrey Solov'yov and Andrei Korol.

Sister-chromatid exchanges and cell-cycle kinetics in the lymphocytes of workers occupationally exposed to a chemical mixture in the tyre industry.

PubMed

Sasiadek, M

1993-08-01

Cytogenetic studies of clinically healthy workers employed in the rubber industry showed an increase in chromosome aberrations (CAs), sister-chromatid exchanges (SCEs) and a decrease in proliferation indices (PIs). The aim of the present study was to establish, using the SCE and PI tests, genotoxic effects of hazardous chemicals in the rubber industry. An increase in mean SCEs in the lymphocytes of vulcanizers as compared to controls was observed. Since the PI in the exposed group was insignificantly decreased as compared to the controls, it could be concluded that the SCE test is the most sensitive cytogenetic test for the detection of a genotoxic effect of chemicals in the rubber industry. There was no evidence in the present study that the genotoxic effect of chemicals in the rubber industry was enhanced by cigarette smoking.

Telomere sister chromatid exchange in telomerase deficient murine cells

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

Wang, Yisong; Giannone, Richard J; Liu, Yie

2005-01-01

We have recently demonstrated that several types of genomic rearrangements (i.e., telomere sister chromatid exchange (T-SCE), genomic-SCE, or end-to-end fusions) were more often detected in long-term cultured murine telomerase deficient embryonic stem (ES) cells than in freshly prepared murine splenocytes, even through they possessed similar frequencies of critically short telomeres. The high rate of genomic rearrangements in telomerase deficient ES cells, when compared to murine splenocytes, may reflect the cultured cells' gained ability to protect chromosome ends with eroded telomeres allowing them to escape 'end crisis'. However, the possibility that ES cells were more permissive to genomic rearrangements than othermore » cell types or that differences in the microenvironment or genetic background of the animals might consequentially determine the rate of T-SCEs or other genomic rearrangements at critically short telomeres could not be ruled out.« less

Common fragile sites (CFS) and extremely large CFS genes are targets for human papillomavirus integrations and chromosome rearrangements in oropharyngeal squamous cell carcinoma.

PubMed

Gao, Ge; Johnson, Sarah H; Vasmatzis, George; Pauley, Christina E; Tombers, Nicole M; Kasperbauer, Jan L; Smith, David I

2017-01-01

Common fragile sites (CFS) are chromosome regions that are prone to form gaps or breaks in response to DNA replication stress. They are often found as hotspots for sister chromatid exchanges, deletions, and amplifications in different cancers. Many of the CFS regions are found to span genes whose genomic sequence is greater than 1 Mb, some of which have been demonstrated to function as important tumor suppressors. CFS regions are also hotspots for human papillomavirus (HPV) integrations in cervical cancer. We used mate-pair sequencing to examine HPV integration events and chromosomal structural variations in 34 oropharyngeal squamous cell carcinoma (OPSCC). We used endpoint PCR and Sanger sequencing to validate each HPV integration event and found HPV integrations preferentially occurred within CFS regions similar to what is observed in cervical cancer. We also found that many of the chromosomal alterations detected also occurred at or near the cytogenetic location of CFSs. Several large genes were also found to be recurrent targets of rearrangements, independent of HPV integrations, including CSMD1 (2.1Mb), LRP1B (1.9Mb), and LARGE1 (0.7Mb). Sanger sequencing revealed that the nucleotide sequences near to identified junction sites contained repetitive and AT-rich sequences that were shown to have the potential to form stem-loop DNA secondary structures that might stall DNA replication fork progression during replication stress. This could then cause increased instability in these regions which could lead to cancer development in human cells. Our findings suggest that CFSs and some specific large genes appear to play important roles in OPSCC. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Isolated chromosome 8p23.2‑pter deletion: Novel evidence for developmental delay, intellectual disability, microcephaly and neurobehavioral disorders.

PubMed

Shi, Shanshan; Lin, Shaobin; Chen, Baojiang; Zhou, Yi

2017-11-01

The current study presents a patient carrying a de novo ~6 Mb deletion of the isolated chromosome 8p23.2‑pter that was identified with a single‑nucleotide polymorphism array. The patient was characterized by developmental delay (DD)/intellectual disability (ID), microcephaly, autism spectrum disorder, attention‑deficit/hyperactivity disorders and mildly dysmorphic features. The location, size and gene content of the deletion observed in this patient were compared with those in 7 patients with isolated 8p23.2 to 8pter deletions reported in previous studies (4 patients) or recorded in the Database of Chromosomal Imbalance and Phenotype in Humans Using Ensembl Resources (DECIPHER) database (3 patients). The deletions reported in previous studies were assessed using a chromosomal microarray analysis. The 8p23.2‑pter deletion was a distinct microdeletion syndrome, as similar phenotypes were observed in patients with this deletion. Furthermore, following a detailed review of the potential associations between the genes located from 8p23.2 to 8pter and their clinical significance, it was hypothesized that DLG associated protein 2, ceroid‑lipofuscinosis neuronal 8, Rho guanine nucleotide exchange factor 10 and CUB and sushi multiple domains 1 may be candidate genes for DD/ID, microcephaly and neurobehavioral disorders. However, firm evidence should be accumulated from high‑resolution studies of patients with small, isolated, overlapping and interstitial deletions involving the region from 8p23.2 to 8pter. These studies will allow determination of genotype‑phenotype associations for the specific genes crucial to 8p23.2‑pter.

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.

Identification and characterization of a subtelomeric satellite DNA in Callitrichini monkeys.

PubMed

Araújo, Naiara Pereira; de Lima, Leonardo Gomes; Dias, Guilherme Borges; Kuhn, Gustavo Campos Silva; de Melo, Alan Lane; Yonenaga-Yassuda, Yatiyo; Stanyon, Roscoe; Svartman, Marta

2017-08-01

Repetitive DNAs are abundant fast-evolving components of eukaryotic genomes, which often possess important structural and functional roles. Despite their ubiquity, repetitive DNAs are poorly studied when compared with the genic fraction of genomes. Here, we took advantage of the availability of the sequenced genome of the common marmoset Callithrix jacchus to assess its satellite DNAs (satDNAs) and their distribution in Callitrichini. After clustering analysis of all reads and comparisons by similarity, we identified a satDNA composed by 171 bp motifs, named MarmoSAT, which composes 1.09% of the C. jacchus genome. Fluorescent in situ hybridization on chromosomes of species from the genera Callithrix, Mico and Callimico showed that MarmoSAT had a subtelomeric location. In addition to the common monomeric, we found that MarmoSAT was also organized in higher-order repeats of 338 bp in Callimico goeldii. Our phylogenetic analyses showed that MarmoSAT repeats from C. jacchus lack chromosome-specific features, suggesting exchange events among subterminal regions of non-homologous chromosomes. MarmoSAT is transcribed in several tissues of C. jacchus, with the highest transcription levels in spleen, thymus and heart. The transcription profile and subtelomeric location suggest that MarmoSAT may be involved in the regulation of telomerase and modulation of telomeric chromatin. © The Author 2017. Published by Oxford University Press on behalf of Kazusa DNA Research Institute.

Evolutionary Origins and Dynamics of Octoploid Strawberry Subgenomes Revealed by Dense Targeted Capture Linkage Maps

PubMed Central

Tennessen, Jacob A.; Govindarajulu, Rajanikanth; Ashman, Tia-Lynn; Liston, Aaron

2014-01-01

Whole-genome duplications are radical evolutionary events that have driven speciation and adaptation in many taxa. Higher-order polyploids have complex histories often including interspecific hybridization and dynamic genomic changes. This chromosomal reshuffling is poorly understood for most polyploid species, despite their evolutionary and agricultural importance, due to the challenge of distinguishing homologous sequences from each other. Here, we use dense linkage maps generated with targeted sequence capture to improve the diploid strawberry (Fragaria vesca) reference genome and to disentangle the subgenomes of the wild octoploid progenitors of cultivated strawberry, Fragaria virginiana and Fragaria chiloensis. Our novel approach, POLiMAPS (Phylogenetics Of Linkage-Map-Anchored Polyploid Subgenomes), leverages sequence reads to associate informative interhomeolog phylogenetic markers with linkage groups and reference genome positions. In contrast to a widely accepted model, we find that one of the four subgenomes originates with the diploid cytoplasm donor F. vesca, one with the diploid Fragaria iinumae, and two with an unknown ancestor close to F. iinumae. Extensive unidirectional introgression has converted F. iinumae-like subgenomes to be more F. vesca-like, but never the reverse, due either to homoploid hybridization in the F. iinumae-like diploid ancestors or else strong selection spreading F. vesca-like sequence among subgenomes through homeologous exchange. In addition, divergence between homeologous chromosomes has been substantially augmented by interchromosomal rearrangements. Our phylogenetic approach reveals novel aspects of the complicated web of genetic exchanges that occur during polyploid evolution and suggests a path forward for unraveling other agriculturally and ecologically important polyploid genomes. PMID:25477420

Extremely Rare Interbreeding Events Can Explain Neanderthal DNA in Living Humans

PubMed Central

Neves, Armando G. M.; Serva, Maurizio

2012-01-01

Considering the recent experimental discovery of Green et al that present-day non-Africans have 1 to of their nuclear DNA of Neanderthal origin, we propose here a model which is able to quantify the genetic interbreeding between two subpopulations with equal fitness, living in the same geographic region. The model consists of a solvable system of deterministic ordinary differential equations containing as a stochastic ingredient a realization of the neutral Wright-Fisher process. By simulating the stochastic part of the model we are able to apply it to the interbreeding ofthe African ancestors of Eurasians and Middle Eastern Neanderthal subpopulations and estimate the only parameter of the model, which is the number of individuals per generation exchanged between subpopulations. Our results indicate that the amount of Neanderthal DNA in living non-Africans can be explained with maximum probability by the exchange of a single pair of individuals between the subpopulations at each 77 generations, but larger exchange frequencies are also allowed with sizeable probability. The results are compatible with a long coexistence time of 130,000 years, a total interbreeding population of order individuals, and with all living humans being descendants of Africans both for mitochondrial DNA and Y chromosome. PMID:23112810

Point mutation impairs centromeric CENH3 loading and induces haploid plants.

PubMed

Karimi-Ashtiyani, Raheleh; Ishii, Takayoshi; Niessen, Markus; Stein, Nils; Heckmann, Stefan; Gurushidze, Maia; Banaei-Moghaddam, Ali Mohammad; Fuchs, Jörg; Schubert, Veit; Koch, Kerstin; Weiss, Oda; Demidov, Dmitri; Schmidt, Klaus; Kumlehn, Jochen; Houben, Andreas

2015-09-08

The chromosomal position of the centromere-specific histone H3 variant CENH3 (also called "CENP-A") is the assembly site for the kinetochore complex of active centromeres. Any error in transcription, translation, modification, or incorporation can affect the ability to assemble intact CENH3 chromatin and can cause centromere inactivation [Allshire RC, Karpen GH (2008) Nat Rev Genet 9 (12):923-937]. Here we show that a single-point amino acid exchange in the centromere-targeting domain of CENH3 leads to reduced centromere loading of CENH3 in barley, sugar beet, and Arabidopsis thaliana. Haploids were obtained after cenh3 L130F-complemented cenh3-null mutant plants were crossed with wild-type A. thaliana. In contrast, in a noncompeting situation (i.e., centromeres possessing only mutated or only wild-type CENH3), no uniparental chromosome elimination occurs during early embryogenesis. The high degree of evolutionary conservation of the identified mutation site offers promising opportunities for application in a wide range of crop species in which haploid technology is of interest.

Point mutation impairs centromeric CENH3 loading and induces haploid plants

PubMed Central

Karimi-Ashtiyani, Raheleh; Ishii, Takayoshi; Niessen, Markus; Stein, Nils; Heckmann, Stefan; Gurushidze, Maia; Banaei-Moghaddam, Ali Mohammad; Fuchs, Jörg; Schubert, Veit; Koch, Kerstin; Weiss, Oda; Demidov, Dmitri; Schmidt, Klaus; Kumlehn, Jochen; Houben, Andreas

2015-01-01

The chromosomal position of the centromere-specific histone H3 variant CENH3 (also called “CENP-A”) is the assembly site for the kinetochore complex of active centromeres. Any error in transcription, translation, modification, or incorporation can affect the ability to assemble intact CENH3 chromatin and can cause centromere inactivation [Allshire RC, Karpen GH (2008) Nat Rev Genet 9 (12):923–937]. Here we show that a single-point amino acid exchange in the centromere-targeting domain of CENH3 leads to reduced centromere loading of CENH3 in barley, sugar beet, and Arabidopsis thaliana. Haploids were obtained after cenh3 L130F-complemented cenh3-null mutant plants were crossed with wild-type A. thaliana. In contrast, in a noncompeting situation (i.e., centromeres possessing only mutated or only wild-type CENH3), no uniparental chromosome elimination occurs during early embryogenesis. The high degree of evolutionary conservation of the identified mutation site offers promising opportunities for application in a wide range of crop species in which haploid technology is of interest. PMID:26294252

Magnesium Increases Homoeologous Crossover Frequency During Meiosis in ZIP4 (Ph1 Gene) Mutant Wheat-Wild Relative Hybrids.

PubMed

Rey, María-Dolores; Martín, Azahara C; Smedley, Mark; Hayta, Sadiye; Harwood, Wendy; Shaw, Peter; Moore, Graham

2018-01-01

Wild relatives provide an important source of useful traits in wheat breeding. Wheat and wild relative hybrids have been widely used in breeding programs to introduce such traits into wheat. However, successful introgression is limited by the low frequency of homoeologous crossover (CO) between wheat and wild relative chromosomes. Hybrids between wheat carrying a 70 Mb deletion on chromosome 5B ( ph1b ) and wild relatives, have been exploited to increase the level of homoeologous CO, allowing chromosome exchange between their chromosomes. In ph1b -rye hybrids, CO number increases from a mean of 1 CO to 7 COs per cell. CO number can be further increased up to a mean of 12 COs per cell in these ph1b hybrids by treating the plants with Hoagland solution. More recently, it was shown that the major meiotic crossover gene ZIP4 on chromosome 5B ( TaZIP4-B2 ) within the 70 Mb deletion, was responsible for the restriction of homoeologous COs in wheat-wild relative hybrids, confirming the ph1b phenotype as a complete Tazip4-B2 deletion mutant ( Tazip4-B2 ph1b) . In this study, we have identified the particular Hoagland solution constituent responsible for the increased chiasma frequency in Tazip4-B2 ph1b mutant-rye hybrids and extended the analysis to Tazip4-B2 TILLING and CRISPR mutant- Ae variabilis hybrids. Chiasma frequency at meiotic metaphase I, in the absence of each Hoagland solution macronutrient (NH 4 H 2 PO 4 , KNO 3 , Ca (NO 3 )2·4H 2 O or Mg SO 4 ·7H 2 O) was analyzed. A significant decrease in homoeologous CO frequency was observed when the Mg 2+ ion was absent. A significant increase of homoeologous CO frequency was observed in all analyzed hybrids, when plants were irrigated with a 1 mM Mg 2+ solution. These observations suggest a role for magnesium supplementation in improving the success of genetic material introgression from wild relatives into wheat.

Plasmid integration in a wide range of bacteria mediated by the integrase of Lactobacillus delbrueckii bacteriophage mv4.

PubMed Central

Auvray, F; Coddeville, M; Ritzenthaler, P; Dupont, L

1997-01-01

Bacteriophage mv4 is a temperate phage infecting Lactobacillus delbrueckii subsp. bulgaricus. During lysogenization, the phage integrates its genome into the host chromosome at the 3' end of a tRNA(Ser) gene through a site-specific recombination process (L. Dupont et al., J. Bacteriol., 177:586-595, 1995). A nonreplicative vector (pMC1) based on the mv4 integrative elements (attP site and integrase-coding int gene) is able to integrate into the chromosome of a wide range of bacterial hosts, including Lactobacillus plantarum, Lactobacillus casei (two strains), Lactococcus lactis subsp. cremoris, Enterococcus faecalis, and Streptococcus pneumoniae. Integrative recombination of pMC1 into the chromosomes of all of these species is dependent on the int gene product and occurs specifically at the pMC1 attP site. The isolation and sequencing of pMC1 integration sites from these bacteria showed that in lactobacilli, pMC1 integrated into the conserved tRNA(Ser) gene. In the other bacterial species where this tRNA gene is less or not conserved; secondary integration sites either in potential protein-coding regions or in intergenic DNA were used. A consensus sequence was deduced from the analysis of the different integration sites. The comparison of these sequences demonstrated the flexibility of the integrase for the bacterial integration site and suggested the importance of the trinucleotide CCT at the 5' end of the core in the strand exchange reaction. PMID:9068626

Single-cell template strand sequencing by Strand-seq enables the characterization of individual homologs.

PubMed

Sanders, Ashley D; Falconer, Ester; Hills, Mark; Spierings, Diana C J; Lansdorp, Peter M

2017-06-01

The ability to distinguish between genome sequences of homologous chromosomes in single cells is important for studies of copy-neutral genomic rearrangements (such as inversions and translocations), building chromosome-length haplotypes, refining genome assemblies, mapping sister chromatid exchange events and exploring cellular heterogeneity. Strand-seq is a single-cell sequencing technology that resolves the individual homologs within a cell by restricting sequence analysis to the DNA template strands used during DNA replication. This protocol, which takes up to 4 d to complete, relies on the directionality of DNA, in which each single strand of a DNA molecule is distinguished based on its 5'-3' orientation. Culturing cells in a thymidine analog for one round of cell division labels nascent DNA strands, allowing for their selective removal during genomic library construction. To preserve directionality of template strands, genomic preamplification is bypassed and labeled nascent strands are nicked and not amplified during library preparation. Each single-cell library is multiplexed for pooling and sequencing, and the resulting sequence data are aligned, mapping to either the minus or plus strand of the reference genome, to assign template strand states for each chromosome in the cell. The major adaptations to conventional single-cell sequencing protocols include harvesting of daughter cells after a single round of BrdU incorporation, bypassing of whole-genome amplification, and removal of the BrdU + strand during Strand-seq library preparation. By sequencing just template strands, the structure and identity of each homolog are preserved.

Widespread Gene Conversion in Centromere Cores

PubMed Central

Shi, Jinghua; Wolf, Sarah E.; Burke, John M.; Presting, Gernot G.; Ross-Ibarra, Jeffrey; Dawe, R. Kelly

2010-01-01

Centromeres are the most dynamic regions of the genome, yet they are typified by little or no crossing over, making it difficult to explain the origin of this diversity. To address this question, we developed a novel CENH3 ChIP display method that maps kinetochore footprints over transposon-rich areas of centromere cores. A high level of polymorphism made it possible to map a total of 238 within-centromere markers using maize recombinant inbred lines. Over half of the markers were shown to interact directly with kinetochores (CENH3) by chromatin immunoprecipitation. Although classical crossing over is fully suppressed across CENH3 domains, two gene conversion events (i.e., non-crossover marker exchanges) were identified in a mapping population. A population genetic analysis of 53 diverse inbreds suggests that historical gene conversion is widespread in maize centromeres, occurring at a rate >1×10−5/marker/generation. We conclude that gene conversion accelerates centromere evolution by facilitating sequence exchange among chromosomes. PMID:20231874

N-terminal-mediated oligomerization of DnaA drives the occupancy-dependent rejuvenation of the protein on the membrane.

PubMed

Aranovich, Alexander; Braier-Marcovitz, Shani; Ansbacher, Esti; Granek, Rony; Parola, Abraham H; Fishov, Itzhak

2015-08-13

DnaA, the initiator of chromosome replication in most known eubacteria species, is activated once per cell division cycle. Its overall activity cycle is driven by ATP hydrolysis and ADP-ATP exchange. The latter can be promoted by binding to specific sequences on the chromosome and/or to acidic phospholipids in the membrane. We have previously shown that the transition into an active form (rejuvenation) is strongly co-operative with respect to DnaA membrane occupancy. Only at low membrane occupancy is DnaA reactivation efficiently catalysed by the acidic phospholipids. The present study was aimed at unravelling the molecular mechanism underlying the occupancy-dependent DnaA rejuvenation. We found that truncation of the DnaA N-terminal completely abolishes the co-operative transformation between the high and low occupancy states (I and II respectively) without affecting the membrane binding. The environmentally sensitive fluorophore specifically attached to the N-terminal cysteines of DnaA reported on occupancy-correlated changes in its vicinity. Cross-linking of DnaA with a short homobifunctional reagent revealed that state II of the protein on the membrane corresponds to a distinct oligomeric form of DnaA. The kinetic transition of DnaA on the membrane surface is described in the present study by a generalized 2D condensation phase transition model, confirming the existence of two states of DnaA on the membrane and pointing to the possibility that membrane protein density serves as an on-off switch in vivo. We conclude that the DnaA conformation attained at low surface density drives its N-terminal-mediated oligomerization, which is presumably a pre-requisite for facilitated nt exchange. © 2015 Authors.

Evaluation of chemopreventive effects of betel leaf on the genotoxicity of pan masala.

PubMed

Trivedi, A H; Patel, R K; Rawal, U M; Adhvaryu, S G; Balar, D B

1994-01-01

The antigenotoxic effect of the aqueous extract of betel leaf (BL-ext.) against the pan masala was tested with the help of cytogenetic endpoints like chromosome aberration (CA) and sister chromatid exchange (SCE) utilizing Chinese hamster ovary (CHO) cells. Compared to the cultures treated with aqueous extract of pan masala alone, a reduction in CA and SCE frequencies in CHO cells was observed following a combined treatment with pan masala (with or without tobacco) extract and BL-ext. The protective effect of BL-ext. against the genomic damage caused by pan masala was statistically significant only after treating the cells for a longer period.

Genome-wide characterization of genetic diversity and population structure in Secale

PubMed Central

2014-01-01

Background Numerous rye accessions are stored in ex situ genebanks worldwide. Little is known about the extent of genetic diversity contained in any of them and its relation to contemporary varieties, since to date rye genetic diversity studies had a very limited scope, analyzing few loci and/ or few accessions. Development of high throughput genotyping methods for rye opened the possibility for genome wide characterizations of large accessions sets. In this study we used 1054 Diversity Array Technology (DArT) markers with defined chromosomal location to characterize genetic diversity and population structure in a collection of 379 rye accessions including wild species, landraces, cultivated materials, historical and contemporary rye varieties. Results Average genetic similarity (GS) coefficients and average polymorphic information content (PIC) values varied among chromosomes. Comparison of chromosome specific average GS within and between germplasm sub-groups indicated regions of chromosomes 1R and 4R as being targeted by selection in current breeding programs. Bayesian clustering, principal coordinate analysis and Neighbor Joining clustering demonstrated that source and improvement status contributed significantly to the structure observed in the analyzed set of Secale germplasm. We revealed a relatively limited diversity in improved rye accessions, both historical and contemporary, as well as lack of correlation between clustering of improved accessions and geographic origin, suggesting common genetic background of rye accessions from diverse geographic regions and extensive germplasm exchange. Moreover, contemporary varieties were distinct from the remaining accessions. Conclusions Our results point to an influence of reproduction methods on the observed diversity patterns and indicate potential of ex situ collections for broadening the genetic diversity in rye breeding programs. Obtained data show that DArT markers provide a realistic picture of the genetic diversity and population structure present in the collection of 379 rye accessions and are an effective platform for rye germplasm characterization and association mapping studies. PMID:25085433

Micronuclear DNA of Oxytricha nova contains sequences with autonomously replicating activity in Saccharomyces cerevisiae.

PubMed Central

Colombo, M M; Swanton, M T; Donini, P; Prescott, D M

1984-01-01

Oxytricha nova is a hypotrichous ciliate with micronuclei and macronuclei. Micronuclei, which contain large, chromosomal-sized DNA, are genetically inert but undergo meiosis and exchange during cell mating. Macronuclei, which contain only small, gene-sized DNA molecules, provide all of the nuclear RNA needed to run the cell. After cell mating the macronucleus is derived from a micronucleus, a derivation that includes excision of the genes from chromosomes and elimination of the remaining DNA. The eliminated DNA includes all of the repetitious sequences and approximately 95% of the unique sequences. We cloned large restriction fragments from the micronucleus that confer replication ability on a replication-deficient plasmid in Saccharomyces cerevisiae. Sequences that confer replication ability are called autonomously replicating sequences. The frequency and effectiveness of autonomously replicating sequences in micronuclear DNA are similar to those reported for DNAs of other organisms introduced into yeast cells. Of the 12 micronuclear fragments with autonomously replicating sequence activity, 9 also showed homology to macronuclear DNA, indicating that they contain a macronuclear gene sequence. We conclude from this that autonomously replicating sequence activity is nonrandomly distributed throughout micronuclear DNA and is preferentially associated with those regions of micronuclear DNA that contain genes. Images PMID:6092934

Extensive concerted evolution of rice paralogs and the road to regaining independence.

PubMed

Wang, Xiyin; Tang, Haibao; Bowers, John E; Feltus, Frank A; Paterson, Andrew H

2007-11-01

Many genes duplicated by whole-genome duplications (WGDs) are more similar to one another than expected. We investigated whether concerted evolution through conversion and crossing over, well-known to affect tandem gene clusters, also affects dispersed paralogs. Genome sequences for two Oryza subspecies reveal appreciable gene conversion in the approximately 0.4 MY since their divergence, with a gradual progression toward independent evolution of older paralogs. Since divergence from subspecies indica, approximately 8% of japonica paralogs produced 5-7 MYA on chromosomes 11 and 12 have been affected by gene conversion and several reciprocal exchanges of chromosomal segments, while approximately 70-MY-old "paleologs" resulting from a genome duplication (GD) show much less conversion. Sequence similarity analysis in proximal gene clusters also suggests more conversion between younger paralogs. About 8% of paleologs may have been converted since rice-sorghum divergence approximately 41 MYA. Domain-encoding sequences are more frequently converted than nondomain sequences, suggesting a sort of circularity--that sequences conserved by selection may be further conserved by relatively frequent conversion. The higher level of concerted evolution in the 5-7 MY-old segmental duplication may reflect the behavior of many genomes within the first few million years after duplication or polyploidization.

Modulation of radiation-induced and mitomycin C-induced chromosome damage by apigenin in human lymphocytes in vitro.

PubMed

Sharma, Narinder K

2013-09-01

Apigenin (APG), a flavone, is known to exhibit antioxidant, antimutagenic and antitumorigenic activity, both in vivo and in vitro. The aim of this study is to investigate the modulatory effects of APG on human lymphocytes after irradiation with gamma rays (3 Gy) or treatment with the antineoplastic agent, mitomycin C (MMC), in vitro. Cytogenetic biomarkers such as chromosome aberrations (CAs), sister chromatid exchanges (SCEs) and cytochalasin-B blocked micronuclei (CBMN), were studied in blood lymphocytes treated with radiation, or antineoplastic agent (MMC), and APG. Whole blood lymphocytes were cultured in vitro using a standard protocol. No significant differences were found in the frequency of CAs or micronuclei (MN) in human peripheral blood lymphocytes irradiated with gamma rays (3 Gy) and then post-treated with APG. There was an increase in the frequency of SCEs per cell in APG-treated samples compared with the controls. Lymphocytes treated with MMC in the presence of APG exhibited a significant decrease (P < 0.01) in the frequency of SCEs compared with MMC treatment alone. The data for the MN test indicated that APG treatment significantly reduced (P < 0.01) the frequency of MMC-induced MN.

Modulation of radiation-induced and mitomycin C-induced chromosome damage by apigenin in human lymphocytes in vitro

PubMed Central

Sharma, Narinder K.

2013-01-01

Apigenin (APG), a flavone, is known to exhibit antioxidant, antimutagenic and antitumorigenic activity, both in vivo and in vitro. The aim of this study is to investigate the modulatory effects of APG on human lymphocytes after irradiation with gamma rays (3 Gy) or treatment with the antineoplastic agent, mitomycin C (MMC), in vitro. Cytogenetic biomarkers such as chromosome aberrations (CAs), sister chromatid exchanges (SCEs) and cytochalasin-B blocked micronuclei (CBMN), were studied in blood lymphocytes treated with radiation, or antineoplastic agent (MMC), and APG. Whole blood lymphocytes were cultured in vitro using a standard protocol. No significant differences were found in the frequency of CAs or micronuclei (MN) in human peripheral blood lymphocytes irradiated with gamma rays (3 Gy) and then post-treated with APG. There was an increase in the frequency of SCEs per cell in APG-treated samples compared with the controls. Lymphocytes treated with MMC in the presence of APG exhibited a significant decrease (P < 0.01) in the frequency of SCEs compared with MMC treatment alone. The data for the MN test indicated that APG treatment significantly reduced (P < 0.01) the frequency of MMC-induced MN. PMID:23764456

The right half of the Escherichia coli replication origin is not essential for viability, but facilitates multi-forked replication

PubMed Central

Stepankiw, Nicholas; Kaidow, Akihiro; Boye, Erik; Bates, David

2010-01-01

Summary Replication initiation is a key event in the cell cycle of all organisms and oriC, the replication origin in Escherichia coli, serves as the prototypical model for this process. The minimal sequence required for oriC function was originally determined entirely from plasmid studies using cloned origin fragments, which have previously been shown to differ dramatically in sequence requirement from the chromosome. Using an in vivo recombineering strategy to exchange wt oriCs for mutated ones regardless of whether they are functional origins or not, we have determined the minimal origin sequence that will support chromosome replication. Nearly the entire right half of oriC could be deleted without loss of origin function, demanding a reassessment of existing models for initiation. Cells carrying the new DnaA box-depleted 163 bp minimal oriC exhibited little or no loss of fitness under slow-growth conditions, but were sensitive to rich medium, suggesting that the dense packing of initiator binding sites that is a hallmark of prokaryotic origins, has likely evolved to support the increased demands of multi-forked replication. PMID:19737351

Paleogenetical study of pre-Columbian samples from Pampa Grande (Salta, Argentina).

PubMed

Carnese, Fransisco R; Mendisco, Fanny; Keyser, Christine; Dejean, Cristina B; Dugoujon, Jean-Michel; Bravi, Claudio M; Ludes, Bertrand; Crubézy, Eric

2010-03-01

Ancient DNA recovered from 21 individuals excavated from burial sites in the Pampa Grande (PG) region (Salta province) of North-Western Argentina (NWA) was analyzed using various genetic markers (mitochondrial DNA, autosomal STRs, and Y chromosomal STRs). The results were compared to ancient and modern DNA from various populations in the Andean and North Argentinean regions, with the aim of establishing their relationships with PG. The mitochondrial haplogroup frequencies described (11% A, 47% B, and 42% D) presented values comparable to those found for the ancient Andean populations from Peru and San Pedro de Atacama. On the other hand, mitochondrial and Y chromosomal haplotypes were specific to PG, as they did not match any other of the South American populations studied. The described genetic diversity indicates homogeneity in the genetic structure of the ancient Andean populations, which was probably facilitated by the intense exchange network in the Andean zone, in particular among Tiwanaku, San Pedro de Atacama, and NWA. The discovery of haplotypes unique to PG could be due to a loss of genetic diversity caused by recent events affecting the autochthonous populations (establishment of the Inca Empire in the region, colonization by the Europeans).

Arabidopsis thaliana FANCD2 Promotes Meiotic Crossover Formation[OPEN

PubMed Central

Kurzbauer, Marie-Therese; Kerzendorfer, Claudia; Sims, Jason; Oliver, Cecilia; Mosiolek, Magdalena; Schweizer, Dieter

2018-01-01

Fanconi anemia (FA) is a human autosomal recessive disorder characterized by chromosomal instability, developmental pathologies, predisposition to cancer, and reduced fertility. So far, 19 genes have been implicated in FA, most of them involved in DNA repair. Some are conserved across higher eukaryotes, including plants. The Arabidopsis thaliana genome encodes a homolog of the Fanconi anemia D2 gene (FANCD2) whose function in DNA repair is not yet fully understood. Here, we provide evidence that AtFANCD2 is required for meiotic homologous recombination. Meiosis is a specialized cell division that ensures reduction of genomic content by half and DNA exchange between homologous chromosomes via crossovers (COs) prior to gamete formation. In plants, a mutation in AtFANCD2 results in a 14% reduction of CO numbers. Genetic analysis demonstrated that AtFANCD2 acts in parallel to both MUTS HOMOLOG4 (AtMSH4), known for its role in promoting interfering COs and MMS AND UV SENSITIVE81 (AtMUS81), known for its role in the formation of noninterfering COs. AtFANCD2 promotes noninterfering COs in a MUS81-independent manner and is therefore part of an uncharted meiotic CO-promoting mechanism, in addition to those described previously. PMID:29352063

GDP-to-GTP exchange on the microtubule end can contribute to the frequency of catastrophe.

PubMed

Piedra, Felipe-Andrés; Kim, Tae; Garza, Emily S; Geyer, Elisabeth A; Burns, Alexander; Ye, Xuecheng; Rice, Luke M

2016-11-07

Microtubules are dynamic polymers of αβ-tubulin that have essential roles in chromosome segregation and organization of the cytoplasm. Catastrophe-the switch from growing to shrinking-occurs when a microtubule loses its stabilizing GTP cap. Recent evidence indicates that the nucleotide on the microtubule end controls how tightly an incoming subunit will be bound (trans-acting GTP), but most current models do not incorporate this information. We implemented trans-acting GTP into a computational model for microtubule dynamics. In simulations, growing microtubules often exposed terminal GDP-bound subunits without undergoing catastrophe. Transient GDP exposure on the growing plus end slowed elongation by reducing the number of favorable binding sites on the microtubule end. Slower elongation led to erosion of the GTP cap and an increase in the frequency of catastrophe. Allowing GDP-to-GTP exchange on terminal subunits in simulations mitigated these effects. Using mutant αβ-tubulin or modified GTP, we showed experimentally that a more readily exchangeable nucleotide led to less frequent catastrophe. Current models for microtubule dynamics do not account for GDP-to-GTP exchange on the growing microtubule end, so our findings provide a new way of thinking about the molecular events that initiate catastrophe. © 2016 Piedra 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).

Sister chromatid exchange, (SCE), High-Frequency Cells (HFCs) and SCE distribution patterns in peripheral blood lymphocytes of Spanish adult smokers compared to non-smokers.

PubMed

Sebastià, Natividad; Hervás, David; Almonacid, Miguel; Villaescusa, Juan Ignacio; Soriano, José Miguel; Sahuquillo, Vicenta; Esteban, Valentín; Barquinero, Joan Francesc; Verdú, Gumersindo; Cervera, José; Such, Esperanza; Montoro, Alegría

2014-04-01

According to the International Agency for Research on Cancer, smoking tobacco is a major cause of cancer in humans. It causes about half of all male cancer deaths and an ever increasing number of cancer deaths in females. The aim of this study was to establish whether cigarette smoking increases sister chromatid exchanges (SCEs) in peripheral blood lymphocytes in two Spanish population groups; light and heavy smokers. The mean number of High-Frequency Cells (HFCs) was determined and, the SCE distribution pattern among the chromosomes was analysed represented by a ratio described below. A local sample of 101 adult smokers (n=48) and non-smokers (n=53), aged from 18 to 49 years, was studied using SCE levels in peripheral lymphocytes. Heavy smoking (≥ 10 cigarettes per day) increased significantly the SCE frequency and the HFC parameters. Neither age nor sex significantly influenced the frequencies in the groups studied. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

Cytogenetic analysis of children under long-term antibacterial therapy with nitroheterocyclic compound furagin.

PubMed

Slapsyte, G; Jankauskiene, A; Mierauskiene, J; Lazutka, J R

2001-04-05

Cytogenetic analysis of chromosome aberrations (CAs) and sister chromatid exchanges (SCEs) was performed in 109 blood samples from 95 pediatric patients with urinary tract infections (UTIs). Children were exposed to diagnostic levels of X-rays during voiding cystourethrography and subsequently treated for one to 12 months with low doses of furagin - N-(5-nitro-2-furyl)-allylidene-1-aminohydantoin. Furagin is 2-substituted 5-nitrofuran, chemically and structurally similar to well-known antibacterial compound nitrofurantoin. Increased frequencies of CAs were found in children undergoing voiding cystourethrography as compared with the unexposed, acentric fragments being the most frequent alteration (2.03 versus 0.88 per 100 cells, P=0.006). However, a significant decrease in the frequency of acentric fragments was determined with the time elapsed since X-ray examination was performed. A time-independent increase in SCE frequency was found in lymphocytes of children treated with furagin. Total CA frequency did not differ significantly between groups of children with various duration of furagin treatment. However, frequency of chromatid exchanges (triradials and quadriradials) increased significantly with duration of treatment.

Laser Stimulated Genomic Exchange in Stem Cells. Laser Non-cloning Techniques

NASA Astrophysics Data System (ADS)

Stefan, V. Alexander

2012-02-01

I propose a novel technique for a pluripotent stem cell generation. Genomic exchange is stimulated by the beat-wave free electron laser, (B-W FEL), frequency matching with the frequencies of the DNAootnotetextJ.D. Watson and F. H. C. Crick, Nature, 171, 737-738 (1953). eigen-oscillations. B-W FEL-1ootnotetextV. Stefan, B.I.Cohen, C. Joshi Science, 243,4890, (Jan 27,1989); Stefan, et al., Bull. APS. 32, No. 9, 1713 (1987); Stefan, APS March-2011, #S1.143; APS- March-2009, #K1.276. scans entire stem cell; B-W FEL-2 probes the chromosomes. The scanning and probing lasers: 300-500nm and 100-300nm, respectively; irradiances: the order-of-10s mW/cm^2 (above the threshold value for a particular gene structure); repetition rate of few-100s Hz. A variety of genetic-matching conditions can be arranged. Genomic glitches, (the cell nucleus transferootnotetextScott Noggle et al. Nature, 478, 70-75 (06 October 2011).), can be hedged by the use of lasers.

Telomere length maintenance--an ALTernative mechanism.

PubMed

Royle, N J; Foxon, J; Jeyapalan, J N; Mendez-Bermudez, A; Novo, C L; Williams, J; Cotton, V E

2008-01-01

The Alternative Lengthening of Telomeres (ALT) mechanism is utilised by approximately 10% of human tumours and a higher proportion of some types of sarcomas. ALT+ cell lines and tumours show heterogeneous telomere length, extra-chromosomal circular and linear telomeric DNA, ALT associated promyelocytic bodies (APBs), a high frequency of post-replication exchanges in telomeres (designated as telomere-sister chromatid exchanges, T-SCE) and high instability at a GC-rich minisatellite, MS32 (D1S8). It is clear that there is a link between the minisatellite instability and the mechanism that underpins ALT, however currently the nature of this relationship is uncertain. Single molecule analysis of telomeric DNA from ALT+ cell lines and tumours has revealed complex telomere mutations that have not been seen in cell lines or tumours that express telomerase. These complex telomere mutations cannot be explained by T-SCE but must arise by another inter-molecular process. The break-induced replication (BIR) model that may explain the observed high frequency of T-SCE and the presence of complex telomere mutations is reviewed. Copyright 2008 S. Karger AG, Basel.

Phylogeny and a structural model of plant MHX transporters

PubMed Central

2013-01-01

Background The Arabidopsis thaliana MHX gene (AtMHX) encodes a Mg2+/H+ exchanger. Among non-plant proteins, AtMHX showed the highest similarity to mammalian Na+/Ca2+ exchanger (NCX) transporters, which are part of the Ca2+/cation (CaCA) exchanger superfamily. Results Sequences showing similarity to AtMHX were searched in the databases or sequenced from cDNA clones. Phylogenetic analysis showed that the MHX family is limited to plants, and constitutes a sixth family within the CaCA superfamily. Some plants include, besides a full MHX gene, partial MHX-related sequences. More than one full MHX gene was currently identified only in Oryza sativa and Mimulus guttatus, but an EST for more than one MHX was identified only in M. guttatus. MHX genes are not present in the currently available chlorophyte genomes. The prevalence of upstream ORFs in MHX genes is much higher than in most plant genes, and can limit their expression. A structural model of the MHXs, based on the resolved structure of NCX1, implies that the MHXs include nine transmembrane segments. The MHXs and NCXs share 32 conserved residues, including a GXG motif implicated in the formation of a tight-turn in a reentrant-loop. Three residues differ between all MHX and NCX proteins. Altered mobility under reducing and non-reducing conditions suggests the presence of an intramolecular disulfide-bond in AtMHX. Conclusions The absence of MHX genes in non-plant genomes and in the currently available chlorophyte genomes, and the presence of an NCX in Chlamydomonas, are consistent with the suggestion that the MHXs evolved from the NCXs after the split of the chlorophyte and streptophyte lineages of the plant kingdom. The MHXs underwent functional diploidization in most plant species. De novo duplication of MHX occurred in O. sativa before the split between the Indica and Japonica subspecies, and was apparently followed by translocation of one MHX paralog from chromosome 2 to chromosome 11 in Japonica. The structural analysis presented and the identification of elements that differ between the MHXs and the NCXs, or between the MHXs of specific plant groups, can contribute to clarification of the structural basis of the function and ion selectivity of MHX transporters. PMID:23634958

Esophageal cancer alters the expression of nuclear pore complex binding protein Hsc70 and eIF5A-1.

PubMed

Moghanibashi, Mehdi; Rastgar Jazii, Ferdous; Soheili, Zahra-Soheila; Zare, Maryam; Karkhane, Aliasghar; Parivar, Kazem; Mohamadynejad, Parisa

2013-06-01

Nuclear pore complex (NPC) is the only corridor for macromolecules exchange between nucleus and cytoplasm. NPC and its components, nucleoporins, play important role in the diverse physiological processes including macromolecule exchange, chromosome segregation, apoptosis and gene expression. Recent reports also suggest involvement of nucleoporins in carcinogenesis. Applying proteomics, we analyzed expression pattern of the NPC components in a newly established esophageal cancer cell line from Persia (Iran), the high-risk region for esophageal cancer. Our results indicate overexpression of Hsc70 and downregulation of subunit alpha type-3 of proteasome, calpain small subunit 1, and eIF5A-1. Among these proteins, Hsc70 and eIF5A-1 are in direct interaction with NPC and involved in the nucleocytoplasmic exchange. Hsc70 plays a critical role as a chaperone in the formation of a cargo-receptor complex in nucleocytoplasmic transport. On the other hand, it is an NPC-associated protein that binds to nucleoporins and contributes in recycling of the nucleocytoplasmic transport receptors in mammals and affects transport of proteins between nucleus and cytoplasm. The other nuclear pore interacting protein: eIF5A-1 binds to the several nucleoporins and participates in nucleocytoplasmic transport. Altered expression of Hsc70 and eIF5A-1 may cause defects in nucleocytoplasmic transport and play a role in esophageal carcinogenesis.

Timely binding of IHF and Fis to DARS2 regulates ATP–DnaA production and replication initiation

PubMed Central

Kasho, Kazutoshi; Fujimitsu, Kazuyuki; Matoba, Toshihiro; Oshima, Taku; Katayama, Tsutomu

2014-01-01

In Escherichia coli, the ATP-bound form of DnaA (ATP–DnaA) promotes replication initiation. During replication, the bound ATP is hydrolyzed to ADP to yield the ADP-bound form (ADP–DnaA), which is inactive for initiation. The chromosomal site DARS2 facilitates the regeneration of ATP–DnaA by catalyzing nucleotide exchange between free ATP and ADP bound to DnaA. However, the regulatory mechanisms governing this exchange reaction are unclear. Here, using in vitro reconstituted experiments, we show that two nucleoid-associated proteins, IHF and Fis, bind site-specifically to DARS2 to activate coordinately the exchange reaction. The regenerated ATP–DnaA was fully active in replication initiation and underwent DnaA–ATP hydrolysis. ADP–DnaA formed heteromultimeric complexes with IHF and Fis on DARS2, and underwent nucleotide dissociation more efficiently than ATP–DnaA. Consistently, mutant analyses demonstrated that specific binding of IHF and Fis to DARS2 stimulates the formation of ATP–DnaA production, thereby promoting timely initiation. Moreover, we show that IHF–DARS2 binding is temporally regulated during the cell cycle, whereas Fis only binds to DARS2 in exponentially growing cells. These results elucidate the regulation of ATP–DnaA and replication initiation in coordination with the cell cycle and growth phase. PMID:25378325

corona Is Required for Higher-Order Assembly of Transverse Filaments into Full-Length Synaptonemal Complex in Drosophila Oocytes

PubMed Central

Page, Scott L.; Khetani, Radhika S.; Lake, Cathleen M.; Nielsen, Rachel J.; Jeffress, Jennifer K.; Warren, William D.; Bickel, Sharon E.; Hawley, R. Scott

2008-01-01

The synaptonemal complex (SC) is an intricate structure that forms between homologous chromosomes early during the meiotic prophase, where it mediates homolog pairing interactions and promotes the formation of genetic exchanges. In Drosophila melanogaster, C(3)G protein forms the transverse filaments (TFs) of the SC. The N termini of C(3)G homodimers localize to the Central Element (CE) of the SC, while the C-termini of C(3)G connect the TFs to the chromosomes via associations with the axial elements/lateral elements (AEs/LEs) of the SC. Here, we show that the Drosophila protein Corona (CONA) co-localizes with C(3)G in a mutually dependent fashion and is required for the polymerization of C(3)G into mature thread-like structures, in the context both of paired homologous chromosomes and of C(3)G polycomplexes that lack AEs/LEs. Although AEs assemble in cona oocytes, they exhibit defects that are characteristic of c(3)G mutant oocytes, including failure of AE alignment and synapsis. These results demonstrate that CONA, which does not contain a coiled coil domain, is required for the stable ‘zippering’ of TFs to form the central region of the Drosophila SC. We speculate that CONA's role in SC formation may be similar to that of the mammalian CE proteins SYCE2 and TEX12. However, the observation that AE alignment and pairing occurs in Tex12 and Syce2 mutant meiocytes but not in cona oocytes suggests that the SC plays a more critical role in the stable association of homologs in Drosophila than it does in mammalian cells. PMID:18802461

Cytogenetic effects of high-energy iron ions: dependence on shielding thickness and material.

PubMed

Durante, M; George, K; Gialanella, G; Grossi, G; La Tessa, C; Manti, L; Miller, J; Pugliese, M; Scampoli, P; Cucinotta, F A

2005-10-01

We report results for chromosomal aberrations in human peripheral blood lymphocytes after they were exposed to high-energy iron ions with or without shielding at the HIMAC, AGS and NSRL accelerators. Isolated lymphocytes were exposed to iron ions with energies between 200 and 5000 MeV/nucleon in the 0.1-1-Gy dose range. Shielding materials consisted of polyethylene, lucite (PMMA), carbon, aluminum and lead, with mass thickness ranging from 2 to 30 g/cm2. After exposure, lymphocytes were stimulated to grow in vitro, and chromosomes were prematurely condensed using a phosphatase inhibitor (calyculin A). Aberrations were scored using FISH painting. The yield of total interchromosomal exchanges (including dicentrics, translocations and complex rearrangements) increased linearly with dose or fluence in the range studied. Shielding decreased the effectiveness per unit dose of iron ions. The highest RBE value was measured with the 1 GeV/nucleon iron-ion beam at NSRL. However, the RBE for the induction of aberrations apparently is not well correlated with the mean LET. When shielding thickness was increased, the frequency of aberrations per particle incident on the shield increased for the 500 MeV/nucleon ions and decreased for the 1 GeV/nucleon ions. Maximum variation at equal mass thickness was obtained with light materials (polyethylene, carbon or PMMA). Variations in the yield of chromosomal aberrations per iron particle incident on the shield follow variations in the dose per incident particle behind the shield but can be modified by the different RBE of the mixed radiation field produced by nuclear fragmentation. The results suggest that shielding design models should be benchmarked using both physics and biological data.

Characterization of three Agrobacterium tumefaciens avirulent mutants with chromosomal mutations that affect induction of vir genes.

PubMed

Metts, J; West, J; Doares, S H; Matthysse, A G

1991-02-01

Three Agrobacterium tumefaciens mutants with chromosomal mutations that affect bacterial virulence were isolated by transposon mutagenesis. Two of the mutants were avirulent on all hosts tested. The third mutant, Ivr-211, was a host range mutant which was avirulent on Bryophyllum diagremontiana, Nicotiana tabacum, N. debneyi, N. glauca, and Daucus carota but was virulent on Zinnia elegans and Lycopersicon esculentum (tomato). That the mutant phenotype was due to the transposon insertion was determined by cloning the DNA containing the transposon insertion and using the cloned DNA to replace the wild-type DNA in the parent bacterial strain by marker exchange. The transposon insertions in the three mutants mapped at three widely separated locations on the bacterial chromosome. The effects of the mutations on various steps in tumor formation were examined. All three mutants showed no alteration in binding to carrot cells. However, none of the mutants showed any induction of vir genes by acetosyringone under conditions in which the parent strain showed vir gene induction. When the mutant bacteria were examined for changes in surface components, it was found that all three of the mutants showed a similar alteration in lipopolysaccharide (LPS). LPS from the mutants was larger in size and more heavily saccharide substituted than LPS from the parent strain. Two of the mutants showed no detectable alteration in outer membrane and periplasmic space proteins. The third mutant, Ivr-225, was missing a 79-kDa surface peptide. The reason(s) for the failure of vir gene induction in these mutants and its relationship, if any, to the observed alteration in LPS are unknown.

The response of mammalian cells to UV-light reveals Rad54-dependent and independent pathways of homologous recombination.

PubMed

Eppink, Berina; Tafel, Agnieszka A; Hanada, Katsuhiro; van Drunen, Ellen; Hickson, Ian D; Essers, Jeroen; Kanaar, Roland

2011-11-10

Ultraviolet (UV) radiation-induced DNA lesions can be efficiently repaired by nucleotide excision repair (NER). However, NER is less effective during replication of UV-damaged chromosomes. In contrast, translesion DNA synthesis (TLS) and homologous recombination (HR) are capable of dealing with lesions in replicating DNA. The core HR protein in mammalian cells is the strand exchange protein RAD51, which is aided by numerous proteins, including RAD54. We used RAD54 as a cellular marker for HR to study the response of mammalian embryonic stem (ES) cells to UV irradiation. In contrast to yeast, ES cells lacking RAD54 are not UV sensitive. Here we show that the requirement for mammalian RAD54 is masked by active NER. By genetically inactivating NER and HR through disruption of the Xpa and Rad54 genes, respectively, we demonstrate the contribution of HR to chromosomal integrity upon UV irradiation. We demonstrate using chromosome fiber analysis at the individual replication fork level, that HR activity is important for the restart of DNA replication after induction of DNA damage by UV-light in NER-deficient cells. Furthermore, our data reveal RAD54-dependent and -independent contributions of HR to the cellular sensitivity to UV-light, and they uncover that RAD54 can compensate for the loss of TLS polymerase η with regard to UV-light sensitivity. In conclusion, we show that HR is important for the progression of UV-stalled replication forks in ES cells, and that protection of the fork is an interplay between HR and TLS. Copyright © 2011 Elsevier B.V. All rights reserved.

Genetic basis of human complement C8[beta] deficiency

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

Kaufmann, T.; Rittner, C.; Schneider, P.M.

1993-06-01

The eighth component of human complement (c8) is a serum protein consisting of three chains ([alpha], [beta], and [gamma]) and encoded by three different genes, C8A, C8B, and C8G. C8A and C8B are closely linked on chromosome 1p, whereas C8G is located on chromosome 9q. In the serum the [beta] subunit is non-covalently bound to the disulfide-linked [alpha]-[gamma] subunit. Patients with C8[beta] deficiency suffer from recurrent neisserial infections such as meningitis. Exon-specific polymerase chain reaction (PCR) amplification with primer pairs from the flanking intron sequences was used to amplify all 12 C8B exons separately. No difference regarding the exon sizesmore » was observed in a C8[beta]-deficient patient compared with a normal person. Therefore, direct sequence analysis of all exon-specific PCR products from normal and C8[beta]-deficient individuals was carried out. As a cause for C8[beta] deficiency, we found a single C-T exchange in exon 9 leading to a stop codon. An allele-specific PCR system was designed to detect the normal and the deficiency allele simultaneously. Using this approach as well as PCR typing of the Taql polymorphism located in intron 11, five families with 7 C8[beta]-deficient members were investigated. The mutation was not found to be restricted to one of the two Taql RFLP alleles. The mutant allele was observed in all families investigated and can therefore be regarded as a major cause of C8[beta] deficiency in the Caucasian population. In addition, two C8[beta]-deficient patients were found to be heterozygous for the C-T exchange. The molecular basis of the alleles without this point mutation also causing deficiency has not yet been defined. 23 refs., 4 figs., 3 tabs.« less

Mouse Y-linked Zfy1 and Zfy2 are expressed during the male-specific interphase between meiosis I and meiosis II and promote the 2nd meiotic division.

PubMed

Vernet, Nadège; Mahadevaiah, Shantha K; Yamauchi, Yasuhiro; Decarpentrie, Fanny; Mitchell, Michael J; Ward, Monika A; Burgoyne, Paul S

2014-06-01

Mouse Zfy1 and Zfy2 encode zinc finger transcription factors that map to the short arm of the Y chromosome (Yp). They have previously been shown to promote meiotic quality control during pachytene (Zfy1 and Zfy2) and at the first meiotic metaphase (Zfy2). However, from these previous studies additional roles for genes encoded on Yp during meiotic progression were inferred. In order to identify these genes and investigate their function in later stages of meiosis, we created three models with diminishing Yp and Zfy gene complements (but lacking the Y-long-arm). Since the Y-long-arm mediates pairing and exchange with the X via their pseudoautosomal regions (PARs) we added a minute PAR-bearing X chromosome derivative to enable formation of a sex bivalent, thus avoiding Zfy2-mediated meiotic metaphase I (MI) checkpoint responses to the unpaired (univalent) X chromosome. Using these models we obtained definitive evidence that genetic information on Yp promotes meiosis II, and by transgene addition identified Zfy1 and Zfy2 as the genes responsible. Zfy2 was substantially more effective and proved to have a much more potent transactivation domain than Zfy1. We previously established that only Zfy2 is required for the robust apoptotic elimination of MI spermatocytes in response to a univalent X; the finding that both genes potentiate meiosis II led us to ask whether there was de novo Zfy1 and Zfy2 transcription in the interphase between meiosis I and meiosis II, and this proved to be the case. X-encoded Zfx was also expressed at this stage and Zfx over-expression also potentiated meiosis II. An interphase between the meiotic divisions is male-specific and we previously hypothesised that this allows meiosis II critical X and Y gene reactivation following sex chromosome silencing in meiotic prophase. The interphase transcription and meiosis II function of Zfx, Zfy1 and Zfy2 validate this hypothesis.

Mouse Y-Linked Zfy1 and Zfy2 Are Expressed during the Male-Specific Interphase between Meiosis I and Meiosis II and Promote the 2nd Meiotic Division

PubMed Central

Vernet, Nadège; Mahadevaiah, Shantha K.; Yamauchi, Yasuhiro; Decarpentrie, Fanny; Mitchell, Michael J.; Ward, Monika A.; Burgoyne, Paul S.

2014-01-01

Mouse Zfy1 and Zfy2 encode zinc finger transcription factors that map to the short arm of the Y chromosome (Yp). They have previously been shown to promote meiotic quality control during pachytene (Zfy1 and Zfy2) and at the first meiotic metaphase (Zfy2). However, from these previous studies additional roles for genes encoded on Yp during meiotic progression were inferred. In order to identify these genes and investigate their function in later stages of meiosis, we created three models with diminishing Yp and Zfy gene complements (but lacking the Y-long-arm). Since the Y-long-arm mediates pairing and exchange with the X via their pseudoautosomal regions (PARs) we added a minute PAR-bearing X chromosome derivative to enable formation of a sex bivalent, thus avoiding Zfy2-mediated meiotic metaphase I (MI) checkpoint responses to the unpaired (univalent) X chromosome. Using these models we obtained definitive evidence that genetic information on Yp promotes meiosis II, and by transgene addition identified Zfy1 and Zfy2 as the genes responsible. Zfy2 was substantially more effective and proved to have a much more potent transactivation domain than Zfy1. We previously established that only Zfy2 is required for the robust apoptotic elimination of MI spermatocytes in response to a univalent X; the finding that both genes potentiate meiosis II led us to ask whether there was de novo Zfy1 and Zfy2 transcription in the interphase between meiosis I and meiosis II, and this proved to be the case. X-encoded Zfx was also expressed at this stage and Zfx over-expression also potentiated meiosis II. An interphase between the meiotic divisions is male-specific and we previously hypothesised that this allows meiosis II critical X and Y gene reactivation following sex chromosome silencing in meiotic prophase. The interphase transcription and meiosis II function of Zfx, Zfy1 and Zfy2 validate this hypothesis. PMID:24967676

Phenotypic Analysis of ATM Protein Kinase in DNA Double-Strand Break Formation and Repair.

PubMed

Mian, Elisabeth; Wiesmüller, Lisa

2017-01-01

Ataxia telangiectasia mutated (ATM) encodes a serine/threonine protein kinase, which is involved in various regulatory processes in mammalian cells. Its best-known role is apical activation of the DNA damage response following generation of DNA double-strand breaks (DSBs). When DSBs appear, sensor and mediator proteins are recruited, activating transducers such as ATM, which in turn relay a widespread signal to a multitude of downstream effectors. ATM mutation causes Ataxia telangiectasia (AT), whereby the disease phenotype shows differing characteristics depending on the underlying ATM mutation. However, all phenotypes share progressive neurodegeneration and marked predisposition to malignancies at the organismal level and sensitivity to ionizing radiation and chromosome aberrations at the cellular level. Expression and localization of the ATM protein can be determined via western blotting and immunofluorescence microscopy; however, detection of subtle alterations such as resulting from amino acid exchanges rather than truncating mutations requires functional testing. Previous studies on the role of ATM in DSB repair, which connects with radiosensitivity and chromosomal stability, gave at first sight contradictory results. To systematically explore the effects of clinically relevant ATM mutations on DSB repair, we engaged a series of lymphoblastoid cell lines (LCLs) derived from AT patients and controls. To examine DSB repair both in a quantitative and qualitative manners, we used an EGFP-based assay comprising different substrates for distinct DSB repair mechanisms. In this way, we demonstrated that particular signaling defects caused by individual ATM mutations led to specific DSB repair phenotypes. To explore the impact of ATM on carcinogenic chromosomal aberrations, we monitored chromosomal breakage at a breakpoint cluster region hotspot within the MLL gene that has been associated with therapy-related leukemia. PCR-based MLL-breakage analysis of HeLa cells treated with and without pharmacological kinase inhibitors revealed ATM-dependent chromatin remodeling at the MLL break site giving access to DNA repair proteins but also nucleases triggering MLL rearrangements. This chapter summarizes these methods for functional characterization of ATM in patient LCLs and human cell lines.

The Cohesive Population Genetics of Molecular Drive

PubMed Central

Ohta, Tomoko; Dover, Gabriel A.

1984-01-01

The long-term population genetics of multigene families is influenced by several biased and unbiased mechanisms of nonreciprocal exchanges (gene conversion, unequal exchanges, transposition) between member genes, often distributed on several chromosomes. These mechanisms cause fluctuations in the copy number of variant genes in an individual and lead to a gradual replacement of an original family of n genes (A) in N number of individuals by a variant gene (a). The process for spreading a variant gene through a family and through a population is called molecular drive. Consideration of the known slow rates of nonreciprocal exchanges predicts that the population variance in the copy number of gene a per individual is small at any given generation during molecular drive. Genotypes at a given generation are expected only to range over a small section of all possible genotypes from one extreme (n number of A) to the other (n number of a). A theory is developed for estimating the size of the population variance by using the concept of identity coefficients. In particular, the variance in the course of spreading of a single mutant gene of a multigene family was investigated in detail, and the theory of identity coefficients at the state of steady decay of genetic variability proved to be useful. Monte Carlo simulations and numerical analysis based on realistic rates of exchange in families of known size reveal the correctness of the theoretical prediction and also assess the effect of bias in turnover. The population dynamics of molecular drive in gradually increasing the mean copy number of a variant gene without the generation of a large variance (population cohesion) is of significance regarding potential interactions between natural selection and molecular drive. PMID:6500260

Plasmid Replicons from Pseudomonas Are Natural Chimeras of Functional, Exchangeable Modules

PubMed Central

Bardaji, Leire; Añorga, Maite; Ruiz-Masó, José A.; del Solar, Gloria; Murillo, Jesús

2017-01-01

Plasmids are a main factor for the evolution of bacteria through horizontal gene exchange, including the dissemination of pathogenicity genes, resistance to antibiotics and degradation of pollutants. Their capacity to duplicate is dependent on their replication determinants (replicon), which also define their bacterial host range and the inability to coexist with related replicons. We characterize a second replicon from the virulence plasmid pPsv48C, from Pseudomonas syringae pv. savastanoi, which appears to be a natural chimera between the gene encoding a newly described replication protein and a putative replication control region present in the widespread family of PFP virulence plasmids. We present extensive evidence of this type of chimerism in structurally similar replicons from species of Pseudomonas, including environmental bacteria as well as plant, animal and human pathogens. We establish that these replicons consist of two functional modules corresponding to putative control (REx-C module) and replication (REx-R module) regions. These modules are functionally separable, do not show specificity for each other, and are dynamically exchanged among replicons of four distinct plasmid families. Only the REx-C module displays strong incompatibility, which is overcome by a few nucleotide changes clustered in a stem-and-loop structure of a putative antisense RNA. Additionally, a REx-C module from pPsv48C conferred replication ability to a non-replicative chromosomal DNA region containing features associated to replicons. Thus, the organization of plasmid replicons as independent and exchangeable functional modules is likely facilitating rapid replicon evolution, fostering their diversification and survival, besides allowing the potential co-option of appropriate genes into novel replicons and the artificial construction of new replicon specificities. PMID:28243228

The cohesive population genetics of molecular drive.

PubMed

Ohta, T; Dover, G A

1984-10-01

The long-term population genetics of multigene families is influenced by several biased and unbiased mechanisms of nonreciprocal exchanges (gene conversion, unequal exchanges, transposition) between member genes, often distributed on several chromosomes. These mechanisms cause fluctuations in the copy number of variant genes in an individual and lead to a gradual replacement of an original family of n genes (A) in N number of individuals by a variant gene (a). The process for spreading a variant gene through a family and through a population is called molecular drive. Consideration of the known slow rates of nonreciprocal exchanges predicts that the population variance in the copy number of gene a per individual is small at any given generation during molecular drive. Genotypes at a given generation are expected only to range over a small section of all possible genotypes from one extreme (n number of A) to the other (n number of a). A theory is developed for estimating the size of the population variance by using the concept of identity coefficients. In particular, the variance in the course of spreading of a single mutant gene of a multigene family was investigated in detail, and the theory of identity coefficients at the state of steady decay of genetic variability proved to be useful. Monte Carlo simulations and numerical analysis based on realistic rates of exchange in families of known size reveal the correctness of the theoretical prediction and also assess the effect of bias in turnover. The population dynamics of molecular drive in gradually increasing the mean copy number of a variant gene without the generation of a large variance (population cohesion) is of significance regarding potential interactions between natural selection and molecular drive.

Biased distributions and decay of long interspersed nuclear elements in the chicken genome.

PubMed

Abrusán, György; Krambeck, Hans-Jürgen; Junier, Thomas; Giordano, Joti; Warburton, Peter E

2008-01-01

The genomes of birds are much smaller than mammalian genomes, and transposable elements (TEs) make up only 10% of the chicken genome, compared with the 45% of the human genome. To study the mechanisms that constrain the copy numbers of TEs, and as a consequence the genome size of birds, we analyzed the distributions of LINEs (CR1's) and SINEs (MIRs) on the chicken autosomes and Z chromosome. We show that (1) CR1 repeats are longest on the Z chromosome and their length is negatively correlated with the local GC content; (2) the decay of CR1 elements is highly biased, and the 5'-ends of the insertions are lost much faster than their 3'-ends; (3) the GC distribution of CR1 repeats shows a bimodal pattern with repeats enriched in both AT-rich and GC-rich regions of the genome, but the CR1 families show large differences in their GC distribution; and (4) the few MIRs in the chicken are most abundant in regions with intermediate GC content. Our results indicate that the primary mechanism that removes repeats from the chicken genome is ectopic exchange and that the low abundance of repeats in avian genomes is likely to be the consequence of their high recombination rates.

Extensive Concerted Evolution of Rice Paralogs and the Road to Regaining Independence

PubMed Central

Wang, Xiyin; Tang, Haibao; Bowers, John E.; Feltus, Frank A.; Paterson, Andrew H.

2007-01-01

Many genes duplicated by whole-genome duplications (WGDs) are more similar to one another than expected. We investigated whether concerted evolution through conversion and crossing over, well-known to affect tandem gene clusters, also affects dispersed paralogs. Genome sequences for two Oryza subspecies reveal appreciable gene conversion in the ∼0.4 MY since their divergence, with a gradual progression toward independent evolution of older paralogs. Since divergence from subspecies indica, ∼8% of japonica paralogs produced 5–7 MYA on chromosomes 11 and 12 have been affected by gene conversion and several reciprocal exchanges of chromosomal segments, while ∼70-MY-old “paleologs” resulting from a genome duplication (GD) show much less conversion. Sequence similarity analysis in proximal gene clusters also suggests more conversion between younger paralogs. About 8% of paleologs may have been converted since rice–sorghum divergence ∼41 MYA. Domain-encoding sequences are more frequently converted than nondomain sequences, suggesting a sort of circularity—that sequences conserved by selection may be further conserved by relatively frequent conversion. The higher level of concerted evolution in the 5–7 MY-old segmental duplication may reflect the behavior of many genomes within the first few million years after duplication or polyploidization. PMID:18039882

Chromosomal Integrity after UV Irradiation Requires FANCD2-Mediated Repair of Double Strand Breaks

PubMed Central

Federico, María Belén; Vallerga, María Belén; Radl, Analía; Paviolo, Natalia Soledad; Bocco, José Luis; Di Giorgio, Marina; Soria, Gastón; Gottifredi, Vanesa

2016-01-01

Fanconi Anemia (FA) is a rare autosomal recessive disorder characterized by hypersensitivity to inter-strand crosslinks (ICLs). FANCD2, a central factor of the FA pathway, is essential for the repair of double strand breaks (DSBs) generated during fork collapse at ICLs. While lesions different from ICLs can also trigger fork collapse, the contribution of FANCD2 to the resolution of replication-coupled DSBs generated independently from ICLs is unknown. Intriguingly, FANCD2 is readily activated after UV irradiation, a DNA-damaging agent that generates predominantly intra-strand crosslinks but not ICLs. Hence, UV irradiation is an ideal tool to explore the contribution of FANCD2 to the DNA damage response triggered by DNA lesions other than ICL repair. Here we show that, in contrast to ICL-causing agents, UV radiation compromises cell survival independently from FANCD2. In agreement, FANCD2 depletion does not increase the amount of DSBs generated during the replication of UV-damaged DNA and is dispensable for UV-induced checkpoint activation. Remarkably however, FANCD2 protects UV-dependent, replication-coupled DSBs from aberrant processing by non-homologous end joining, preventing the accumulation of micronuclei and chromatid aberrations including non-homologous chromatid exchanges. Hence, while dispensable for cell survival, FANCD2 selectively safeguards chromosomal stability after UV-triggered replication stress. PMID:26765540

Molecular Diversity and Population Structure of a Worldwide Collection of Cultivated Tetraploid Alfalfa (Medicago sativa subsp. sativa L.) Germplasm as Revealed by Microsatellite Markers.

PubMed

Qiang, Haiping; Chen, Zhihong; Zhang, Zhengli; Wang, Xuemin; Gao, Hongwen; Wang, Zan

2015-01-01

Information on genetic diversity and population structure of a tetraploid alfalfa collection might be valuable in effective use of the genetic resources. A set of 336 worldwide genotypes of tetraploid alfalfa (Medicago sativa subsp. sativa L.) was genotyped using 85 genome-wide distributed SSR markers to reveal the genetic diversity and population structure in the alfalfa. Genetic diversity analysis identified a total of 1056 alleles across 85 marker loci. The average expected heterozygosity and polymorphism information content values were 0.677 and 0.638, respectively, showing high levels of genetic diversity in the cultivated tetraploid alfalfa germplasm. Comparison of genetic characteristics across chromosomes indicated regions of chromosomes 2 and 3 had the highest genetic diversity. A higher genetic diversity was detected in alfalfa landraces than that of wild materials and cultivars. Two populations were identified by the model-based population structure, principal coordinate and neighbor-joining analyses, corresponding to China and other parts of the world. However, lack of strictly correlation between clustering and geographic origins suggested extensive germplasm exchanges of alfalfa germplasm across diverse geographic regions. The quantitative analysis of the genetic diversity and population structure in this study could be useful for genetic and genomic analysis and utilization of the genetic variation in alfalfa breeding.

A Plasmodium yoelii HECT-like E3 ubiquitin ligase regulates parasite growth and virulence.

PubMed

Nair, Sethu C; Xu, Ruixue; Pattaradilokrat, Sittiporn; Wu, Jian; Qi, Yanwei; Zilversmit, Martine; Ganesan, Sundar; Nagarajan, Vijayaraj; Eastman, Richard T; Orandle, Marlene S; Tan, John C; Myers, Timothy G; Liu, Shengfa; Long, Carole A; Li, Jian; Su, Xin-Zhuan

2017-08-09

Infection of mice with strains of Plasmodium yoelii parasites can result in different pathology, but molecular mechanisms to explain this variation are unclear. Here we show that a P. yoelii gene encoding a HECT-like E3 ubiquitin ligase (Pyheul) influences parasitemia and host mortality. We genetically cross two lethal parasites with distinct disease phenotypes, and identify 43 genetically diverse progeny by typing with microsatellites and 9230 single-nucleotide polymorphisms. A genome-wide quantitative trait loci scan links parasite growth and host mortality to two major loci on chromosomes 1 and 7 with LOD (logarithm of the odds) scores = 6.1 and 8.1, respectively. Allelic exchange of partial sequences of Pyheul in the chromosome 7 locus and modification of the gene expression alter parasite growth and host mortality. This study identifies a gene that may have a function in parasite growth, virulence, and host-parasite interaction, and therefore could be a target for drug or vaccine development.Many strains of Plasmodium differ in virulence, but factors that control these distinctions are not known. Here the authors comparatively map virulence loci using the offspring from a P. yoelii YM and N67 genetic cross, and identify a putative HECT E3 ubiquitin ligase that may explain the variance.

Chromosomal Evolution and Patterns of Introgression in Helianthus

PubMed Central

Barb, Jessica G.; Bowers, John E.; Renaut, Sebastien; Rey, Juan I.; Knapp, Steven J.; Rieseberg, Loren H.; Burke, John M.

2014-01-01

Knowledge of the nature and extent of karyotypic differences between species provides insight into the evolutionary history of the genomes in question and, in the case of closely related species, the potential for genetic exchange between taxa. We constructed high-density genetic maps of the silverleaf sunflower (Helianthus argophyllus) and Algodones Dune sunflower (H. niveus ssp. tephrodes) genomes and compared them to a consensus map of cultivated sunflower (H. annuus) to identify chromosomal rearrangements between species. The genetic maps of H. argophyllus and H. niveus ssp. tephrodes included 17 linkage groups each and spanned 1337 and 1478 cM, respectively. Comparative analyses revealed greater divergence between H. annuus and H. niveus ssp. tephrodes (13 inverted segments, 18 translocated segments) than between H. annuus and H. argophyllus (10 inverted segments, 8 translocated segments), consistent with their known phylogenetic relationships. Marker order was conserved across much of the genome, with 83 and 64% of the H. argophyllus and H. niveus ssp. tephrodes genomes, respectively, being syntenic with H. annuus. Population genomic analyses between H. annuus and H. argophyllus, which are sympatric across a portion of the natural range of H. annuus, revealed significantly elevated genetic structure in rearranged portions of the genome, indicating that such rearrangements are associated with restricted gene flow between these two species. PMID:24770331

Meiotic Parthenogenesis in a Root-Knot Nematode Results in Rapid Genomic Homozygosity

PubMed Central

Liu, Qingli L.; Thomas, Varghese P.; Williamson, Valerie M.

2007-01-01

Many isolates of the plant-parasitic nematode Meloidogyne hapla reproduce by facultative meiotic parthenogenesis. Sexual crosses can occur, but, in the absence of males, the diploid state appears to be restored by reuniting sister chromosomes of a single meiosis. We have crossed inbred strains of M. hapla that differ in DNA markers and produced hybrids and F2 lines. Here we show that heterozygous M. hapla females, upon parthenogenetic reproduction, produce progeny that segregate 1:1 for the presence or absence of dominant DNA markers, as would be expected if sister chromosomes are rejoined, rather than the 3:1 ratio typical of a Mendelian cross. Codominant markers also segregate 1:1 and heterozygotes are present at low frequency (<3%). Segregation patterns and recombinant analysis indicate that a homozygous condition is prevalent for markers flanking recombination events, suggesting that recombination occurs preferentially as four-strand exchanges at similar locations between both pairs of non-sister chromatids. With this mechanism, meiotic parthenogenesis would be expected to result in rapid genomic homozygosity. This type of high negative crossover interference coupled with positive chromatid interference has not been observed in fungal or other animal systems in which it is possible to examine the sister products of a single meiosis and may indicate that meiotic recombination in this nematode has novel features. PMID:17483427

Chromosomal Integrity after UV Irradiation Requires FANCD2-Mediated Repair of Double Strand Breaks.

PubMed

Federico, María Belén; Vallerga, María Belén; Radl, Analía; Paviolo, Natalia Soledad; Bocco, José Luis; Di Giorgio, Marina; Soria, Gastón; Gottifredi, Vanesa

2016-01-01

Fanconi Anemia (FA) is a rare autosomal recessive disorder characterized by hypersensitivity to inter-strand crosslinks (ICLs). FANCD2, a central factor of the FA pathway, is essential for the repair of double strand breaks (DSBs) generated during fork collapse at ICLs. While lesions different from ICLs can also trigger fork collapse, the contribution of FANCD2 to the resolution of replication-coupled DSBs generated independently from ICLs is unknown. Intriguingly, FANCD2 is readily activated after UV irradiation, a DNA-damaging agent that generates predominantly intra-strand crosslinks but not ICLs. Hence, UV irradiation is an ideal tool to explore the contribution of FANCD2 to the DNA damage response triggered by DNA lesions other than ICL repair. Here we show that, in contrast to ICL-causing agents, UV radiation compromises cell survival independently from FANCD2. In agreement, FANCD2 depletion does not increase the amount of DSBs generated during the replication of UV-damaged DNA and is dispensable for UV-induced checkpoint activation. Remarkably however, FANCD2 protects UV-dependent, replication-coupled DSBs from aberrant processing by non-homologous end joining, preventing the accumulation of micronuclei and chromatid aberrations including non-homologous chromatid exchanges. Hence, while dispensable for cell survival, FANCD2 selectively safeguards chromosomal stability after UV-triggered replication stress.

Dominant Epistasis Between Two Quantitative Trait Loci Governing Sporulation Efficiency in Yeast Saccharomyces cerevisiae

PubMed Central

Bergman, Juraj; Mitrikeski, Petar T.

2015-01-01

Summary Sporulation efficiency in the yeast Saccharomyces cerevisiae is a well-established model for studying quantitative traits. A variety of genes and nucleotides causing different sporulation efficiencies in laboratory, as well as in wild strains, has already been extensively characterised (mainly by reciprocal hemizygosity analysis and nucleotide exchange methods). We applied a different strategy in order to analyze the variation in sporulation efficiency of laboratory yeast strains. Coupling classical quantitative genetic analysis with simulations of phenotypic distributions (a method we call phenotype modelling) enabled us to obtain a detailed picture of the quantitative trait loci (QTLs) relationships underlying the phenotypic variation of this trait. Using this approach, we were able to uncover a dominant epistatic inheritance of loci governing the phenotype. Moreover, a molecular analysis of known causative quantitative trait genes and nucleotides allowed for the detection of novel alleles, potentially responsible for the observed phenotypic variation. Based on the molecular data, we hypothesise that the observed dominant epistatic relationship could be caused by the interaction of multiple quantitative trait nucleotides distributed across a 60--kb QTL region located on chromosome XIV and the RME1 locus on chromosome VII. Furthermore, we propose a model of molecular pathways which possibly underlie the phenotypic variation of this trait. PMID:27904371

Length Variation of Cag/Caa Trinucleotide Repeats in Natural Populations of Drosophila Melanogaster and Its Relation to the Recombination Rate

PubMed Central

Michalakis, Y.; Veuille, M.

1996-01-01

Eleven genes distributed along the Drosophila melanogaster chromosome 2 and showing exonic tandem repeats of glutamine codons (CAG or CAA) were surveyed for length variation in a sample of four European and African populations. Only one gene was monomorphic. Eight genes were polymorphic in all populations, with a total number of alleles varying between five and 12 for 120 chromosomes. The average heterozygozity per locus and population was 0.41. Selective neutrality in length variation could not be rejected under the assumptions of the infinite allele model. Significant population subdivision was found though no geographical pattern emerged, all populations being equally different. Significant linkage disequilibrium was found in four out of seven cases where the genetic distance between loci was <1 cM and was negligible when the distance was larger. There is evidence that these associations were established after the populations separated. An unexpected result was that variation at each locus was independent of the coefficient of exchange, although the latter ranged from zero to the relatively high value of 6.7%. This would indicate that background selection and selective hitchhiking, which are thought to affect levels of nucleotide substitution polymorphism, have no effect on trinucleotide repeat variation. PMID:8844158

Binding Linkage in a Telomere DNA–Protein Complex at the Ends of Oxytricha nova Chromosomes

PubMed Central

Buczek, Pawel; Orr, Rochelle S.; Pyper, Sean R.; Shum, Mili; Ota, Emily Kimmel Irene; Gerum, Shawn E.; Horvath, Martin P.

2005-01-01

Alpha and beta protein subunits of the telomere end binding protein from Oxytricha nova (OnTEBP) combine with telomere single strand DNA to form a protective cap at the ends of chromosomes. We tested how protein–protein interactions seen in the co-crystal structure relate to DNA binding through use of fusion proteins engineered as different combinations of domains and subunits derived from OnTEBP. Joining alpha and beta resulted in a protein that bound single strand telomere DNA with high affinity (KD-DNA=1.4 nM). Another fusion protein, constructed without the C-terminal protein–protein interaction domain of alpha, bound DNA with 200-fold diminished affinity (KD-DNA=290 nM) even though the DNA-binding domains of alpha and beta were joined through a peptide linker. Adding back the alpha C-terminal domain as a separate protein restored high-affinity DNA binding. The binding behaviors of these fusion proteins and the native protein subunits are consistent with cooperative linkage between protein-association and DNA-binding equilibria. Linking DNA–protein stability to protein–protein contacts at a remote site may provide a trigger point for DNA–protein disassembly during telomere replication when the single strand telomere DNA must exchange between a very stable OnTEBP complex and telomerase. PMID:15967465

Chromosome-damaging activity of saliva of betel nut and tobacco chewers.

PubMed

Stich, H F; Stich, W

1982-01-01

Saliva of volunteers chewing betel quid, cured betel nut (Areca catechu), betel leaves (Piper betle), a mixture of quid ingredients (dried betel nut flakes, catechu, cardamon, lime, copra and menthol) and Indian tobacco was collected and examined for its genotoxic activity. Chromosome aberrations (chromatid breaks and chromatid exchanges) in Chinese hamster ovary (CHO) cells were used to estimate the genotoxic effect. No detectable levels of clastogenic activity were observed in the saliva of non-chewing individuals. After 5 min of chewing betel quid, betel nut, betel leaves, quid ingredients and Indian tobacco, the saliva samples showed relatively potent clastogenic activities. The addition of transition metals Mn2+ and Cu2+ to the saliva samples of betel nut and Indian tobacco chewers enhanced their clastogenic activities, whereas Fe3+ increased the clastogenicity of the betel nut saliva but decreased the genotoxic effect of the saliva of Indian tobacco chewers. After removal of the betel quid or its components from the mouth, the clastogenic activity disappeared within 5 min. The western-type chewing tobacco did not produce a genotoxic activity in the saliva of chewers. A possible association between the genotoxicity in the saliva of betel quid chewers and the development of oral, pharyngeal and esophageal carcinomas is discussed.

A missense mutation in the vasopressin-neurophysin precursor gene cosegregates with human autosomal dominant neurohypophyseal diabetes insipidus.

PubMed Central

Bahnsen, U; Oosting, P; Swaab, D F; Nahke, P; Richter, D; Schmale, H

1992-01-01

Familial neurohypophyseal diabetes insipidus in humans is a rare disease transmitted as an autosomal dominant trait. Affected individuals have very low or undetectable levels of circulating vasopressin and suffer from polydipsia and polyuria. An obvious candidate gene for the disease is the vasopressin-neurophysin (AVP-NP) precursor gene on human chromosome 20. The 2 kb gene with three exons encodes a composite precursor protein consisting of the neuropeptide vasopressin and two associated proteins, neurophysin and a glycopeptide. Cloning and nucleotide sequence analysis of both alleles of the AVP-NP gene present in a Dutch ADNDI family reveals a point mutation in one allele of the affected family members. Comparison of the nucleotide sequences shows a G----T transversion within the neurophysin-encoding exon B. This missense mutation converts a highly conserved glycine (Gly17 of neurophysin) to a valine residue. RFLP analysis of six related family members indicates cosegregation of the mutant allele with the DI phenotype. The mutation is not present in 96 chromosomes of an unrelated control group. These data suggest that a single amino acid exchange within a highly conserved domain of the human vasopressin-associated neurophysin is the primary cause of one form of ADNDI. Images PMID:1740104

Chromosome identification by new molecular markers and genomic in situ hybridization in the Triticum-Secale-Thinopyrum trigeneric hybrids.

PubMed

Dai, Yi; Duan, Yamei; Chi, Dawn; Liu, Huiping; Huang, Shuai; Cao, Wenguang; Gao, Yong; Fedak, George; Chen, Jianmin

2017-08-01

It is very important to use chromosome-specific markers for identifying alien chromosomes in advanced generations of distant hybridization. The chromosome-specific markers of rye and Thinopyrum elongatum, as well as genomic in situ hybridization, were used to identify the alien chromosomes in eight lines that were derived from the crossing between Triticum trititrigia (AABBEE) and triticale (AABBRR). The results showed that four lines contained all rye chromosomes but no Th. elongatum chromosomes. The line RE36-1 contained all of the rye chromosomes except for chromosome 2R. The lines RE33-2 and RE62-1 contained all rye chromosomes and 1E and 5E translocated chromosome, respectively. The line RE24-4 contained 12 rye chromosomes plus a 7E chromosome or 12 rye chromosomes plus one R-E translocated chromosome. Chromosome identification in the above lines was consistent using chromosome-specific markers and genomic in situ hybridization. These chromosome-specific markers provide useful tools for detecting alien chromosomes in trigeneric hybrids, and these lines could be utilized as valuable germplasm in wheat improvement.

Gametocidal chromosomes enhancing chromosome aberration in common wheat induced by 5-azacytidine.

PubMed

Su, W-Y; Cong, W-W; Shu, Y-J; Wang, D; Xu, G-H; Guo, C-H

2013-07-08

The gametocidal (Gc) chromosome from Aegilops spp induces chromosome mutation, which is introduced into common wheat as a tool of chromosome manipulation for genetic improvement. The Gc chromosome functions similar to a restriction-modification system in bacteria, in which DNA methylation is an important regulator. We treated root tips of wheat carrying Gc chromosomes with the hypomethylation agent 5-azacytidine; chromosome breakage and micronuclei were observed in these root tips. The frequency of aberrations differed in wheat containing different Gc chromosomes, suggesting different functions inducing chromosome breakage. Gc chromosome 3C caused the greatest degree of chromosome aberration, while Gc chromosome 3C(SAT) and 2C caused only slight chromosome aberration. Gc chromosome 3C induced different degrees of chromosome aberration in wheat varieties Triticum aestivum var. Chinese Spring and Norin 26, demonstrating an inhibition function in common wheat.

Timely binding of IHF and Fis to DARS2 regulates ATP-DnaA production and replication initiation.

PubMed

Kasho, Kazutoshi; Fujimitsu, Kazuyuki; Matoba, Toshihiro; Oshima, Taku; Katayama, Tsutomu

2014-12-01

In Escherichia coli, the ATP-bound form of DnaA (ATP-DnaA) promotes replication initiation. During replication, the bound ATP is hydrolyzed to ADP to yield the ADP-bound form (ADP-DnaA), which is inactive for initiation. The chromosomal site DARS2 facilitates the regeneration of ATP-DnaA by catalyzing nucleotide exchange between free ATP and ADP bound to DnaA. However, the regulatory mechanisms governing this exchange reaction are unclear. Here, using in vitro reconstituted experiments, we show that two nucleoid-associated proteins, IHF and Fis, bind site-specifically to DARS2 to activate coordinately the exchange reaction. The regenerated ATP-DnaA was fully active in replication initiation and underwent DnaA-ATP hydrolysis. ADP-DnaA formed heteromultimeric complexes with IHF and Fis on DARS2, and underwent nucleotide dissociation more efficiently than ATP-DnaA. Consistently, mutant analyses demonstrated that specific binding of IHF and Fis to DARS2 stimulates the formation of ATP-DnaA production, thereby promoting timely initiation. Moreover, we show that IHF-DARS2 binding is temporally regulated during the cell cycle, whereas Fis only binds to DARS2 in exponentially growing cells. These results elucidate the regulation of ATP-DnaA and replication initiation in coordination with the cell cycle and growth phase. © The Author(s) 2014. Published by Oxford University Press on behalf of Nucleic Acids Research.

DNA strand-exchange patterns associated with double-strand break-induced and spontaneous mitotic crossovers in Saccharomyces cerevisiae

PubMed Central

2018-01-01

Mitotic recombination can result in loss of heterozygosity and chromosomal rearrangements that shape genome structure and initiate human disease. Engineered double-strand breaks (DSBs) are a potent initiator of recombination, but whether spontaneous events initiate with the breakage of one or both DNA strands remains unclear. In the current study, a crossover (CO)-specific assay was used to compare heteroduplex DNA (hetDNA) profiles, which reflect strand exchange intermediates, associated with DSB-induced versus spontaneous events in yeast. Most DSB-induced CO products had the two-sided hetDNA predicted by the canonical DSB repair model, with a switch in hetDNA position from one product to the other at the position of the break. Approximately 40% of COs, however, had hetDNA on only one side of the initiating break. This anomaly can be explained by a modified model in which there is frequent processing of an early invasion (D-loop) intermediate prior to extension of the invading end. Finally, hetDNA tracts exhibited complexities consistent with frequent expansion of the DSB into a gap, migration of strand-exchange junctions, and template switching during gap-filling reactions. hetDNA patterns in spontaneous COs isolated in either a wild-type background or in a background with elevated levels of reactive oxygen species (tsa1Δ mutant) were similar to those associated with the DSB-induced events, suggesting that DSBs are the major instigator of spontaneous mitotic recombination in yeast. PMID:29579095

Karyotyping of Transformed Human Epithelial Cells from Exposures of Heavy Ions

NASA Technical Reports Server (NTRS)

Yeshitla, Samrawit

2013-01-01

It is most likely that the untreated transformed single clone (clone #2) cell undergoes unequal segregation of chromosome in two daughter cell that result in 94 chromosome during mitosis, particularly in anaphase stage. Chromosome aberration observed. I. Breakage of part of chromosome 7. II. One additional number of chromosome 8 instead of the total chromosome can only be explained by early abnormal cell division. III. Complete lost of chromosome and translocation and fusion of chromosome 3 and X-chromosome. IV. Our result for translocation and fusion of chromosome 3 and X- Chromosome is conformed by mBAND pattern. There is no different between the transformed parental cell and the single cloned transformed cell. Both harbor the chromosome 5 and 16 translocation and both harbor has the trisomy chromosome 20. Transformed cells may have the number of chromosomes greater or less than 46. Doubling of chromosome numbers is a signature of tumor. Chromosomal aberration was observed on HBEC-3kt non-irradiated-soft agar (Clone #2) sample, and indication of chromosome instability in the tumor development process.

Microdissection and chromosome painting of the alien chromosome in an addition line of wheat-Thinopyrum intermedium

USDA-ARS?s Scientific Manuscript database

The chromosome painting is an efficient tool for chromosome research. However, plant chromosome painting is relatively underdeveloped. In this study, chromosome painting was developed and used to identify alien chromosomes in TAi-27, a wheat-Thinopyrum intermedium addition line, and chromosomes of...

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

Human Artificial Chromosomes with Alpha Satellite-Based De Novo Centromeres Show Increased Frequency of Nondisjunction and Anaphase Lag

PubMed Central

Rudd, M. Katharine; Mays, Robert W.; Schwartz, Stuart; Willard, Huntington F.

2003-01-01

Human artificial chromosomes have been used to model requirements for human chromosome segregation and to explore the nature of sequences competent for centromere function. Normal human centromeres require specialized chromatin that consists of alpha satellite DNA complexed with epigenetically modified histones and centromere-specific proteins. While several types of alpha satellite DNA have been used to assemble de novo centromeres in artificial chromosome assays, the extent to which they fully recapitulate normal centromere function has not been explored. Here, we have used two kinds of alpha satellite DNA, DXZ1 (from the X chromosome) and D17Z1 (from chromosome 17), to generate human artificial chromosomes. Although artificial chromosomes are mitotically stable over many months in culture, when we examined their segregation in individual cell divisions using an anaphase assay, artificial chromosomes exhibited more segregation errors than natural human chromosomes (P < 0.001). Naturally occurring, but abnormal small ring chromosomes derived from chromosome 17 and the X chromosome also missegregate more than normal chromosomes, implicating overall chromosome size and/or structure in the fidelity of chromosome segregation. As different artificial chromosomes missegregate over a fivefold range, the data suggest that variable centromeric DNA content and/or epigenetic assembly can influence the mitotic behavior of artificial chromosomes. PMID:14560014

Human artificial chromosomes with alpha satellite-based de novo centromeres show increased frequency of nondisjunction and anaphase lag.

PubMed

Rudd, M Katharine; Mays, Robert W; Schwartz, Stuart; Willard, Huntington F

2003-11-01

Human artificial chromosomes have been used to model requirements for human chromosome segregation and to explore the nature of sequences competent for centromere function. Normal human centromeres require specialized chromatin that consists of alpha satellite DNA complexed with epigenetically modified histones and centromere-specific proteins. While several types of alpha satellite DNA have been used to assemble de novo centromeres in artificial chromosome assays, the extent to which they fully recapitulate normal centromere function has not been explored. Here, we have used two kinds of alpha satellite DNA, DXZ1 (from the X chromosome) and D17Z1 (from chromosome 17), to generate human artificial chromosomes. Although artificial chromosomes are mitotically stable over many months in culture, when we examined their segregation in individual cell divisions using an anaphase assay, artificial chromosomes exhibited more segregation errors than natural human chromosomes (P < 0.001). Naturally occurring, but abnormal small ring chromosomes derived from chromosome 17 and the X chromosome also missegregate more than normal chromosomes, implicating overall chromosome size and/or structure in the fidelity of chromosome segregation. As different artificial chromosomes missegregate over a fivefold range, the data suggest that variable centromeric DNA content and/or epigenetic assembly can influence the mitotic behavior of artificial chromosomes.

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

Designing of plant artificial chromosome (PAC) by using the Chlorella smallest chromosome as a model system.

PubMed

Noutoshi, Y; Arai, R; Fujie, M; Yamada, T

1997-01-01

As a model for plant-type chromosomes, we have been characterizing molecular organization of the Chlorella vulgaris C-169 chromosome I. To identify chromosome structural elements including the centromeric region and replication origins, we constructed a chromosome I specific cosmid library and aligned each cosmid clones to generate contigs. So far, more than 80% of the entire chromosome I has been covered. A complete clonal physical reconstitution of chromosome I provides information on the structure and genomic organization of plant genome. We propose our strategy to construct an artificial chromosome by assembling the functional chromosome structural elements identified on Chrorella chromosome I.

Meiosis Leads to Pervasive Copy-Number Variation and Distorted Inheritance of Accessory Chromosomes of the Wheat Pathogen Zymoseptoria tritici.

PubMed

Fouché, Simone; Plissonneau, Clémence; McDonald, Bruce A; Croll, Daniel

2018-06-01

Meiosis is one of the most conserved molecular processes in eukaryotes. The fidelity of pairing and segregation of homologous chromosomes has a major impact on the proper transmission of genetic information. Aberrant chromosomal transmission can have major phenotypic consequences, yet the mechanisms are poorly understood. Fungi are excellent models to investigate processes of chromosomal transmission, because many species have highly polymorphic genomes that include accessory chromosomes. Inheritance of accessory chromosomes is often unstable and chromosomal losses have little impact on fitness. We analyzed chromosomal inheritance in 477 progeny coming from two crosses of the fungal wheat pathogen Zymoseptoria tritici. For this, we developed a high-throughput screening method based on restriction site-associated DNA sequencing that generated dense coverage of genetic markers along each chromosome. We identified rare instances of chromosomal duplications (disomy) in core chromosomes. Accessory chromosomes showed high overall frequencies of disomy. Chromosomal rearrangements were found exclusively on accessory chromosomes and were more frequent than disomy. Accessory chromosomes present in only one of the parents in an analyzed cross were inherited at significantly higher rates than the expected 1:1 segregation ratio. Both the chromosome and the parental background had significant impacts on the rates of disomy, losses, rearrangements, and distorted inheritance. We found that chromosomes with higher sequence similarity and lower repeat content were inherited more faithfully. The large number of rearranged progeny chromosomes identified in this species will enable detailed analyses of the mechanisms underlying chromosomal rearrangement.

Numerous Transitions of Sex Chromosomes in Diptera

PubMed Central

Vicoso, Beatriz; Bachtrog, Doris

2015-01-01

Many species groups, including mammals and many insects, determine sex using heteromorphic sex chromosomes. Diptera flies, which include the model Drosophila melanogaster, generally have XY sex chromosomes and a conserved karyotype consisting of six chromosomal arms (five large rods and a small dot), but superficially similar karyotypes may conceal the true extent of sex chromosome variation. Here, we use whole-genome analysis in 37 fly species belonging to 22 different families of Diptera and uncover tremendous hidden diversity in sex chromosome karyotypes among flies. We identify over a dozen different sex chromosome configurations, and the small dot chromosome is repeatedly used as the sex chromosome, which presumably reflects the ancestral karyotype of higher Diptera. However, we identify species with undifferentiated sex chromosomes, others in which a different chromosome replaced the dot as a sex chromosome or in which up to three chromosomal elements became incorporated into the sex chromosomes, and others yet with female heterogamety (ZW sex chromosomes). Transcriptome analysis shows that dosage compensation has evolved multiple times in flies, consistently through up-regulation of the single X in males. However, X chromosomes generally show a deficiency of genes with male-biased expression, possibly reflecting sex-specific selective pressures. These species thus provide a rich resource to study sex chromosome biology in a comparative manner and show that similar selective forces have shaped the unique evolution of sex chromosomes in diverse fly taxa. PMID:25879221

Discovery of Supernumerary B Chromosomes in Drosophila melanogaster

PubMed Central

Bauerly, Elisabeth; Hughes, Stacie E.; Vietti, Dana R.; Miller, Danny E.; McDowell, William; Hawley, R. Scott

2014-01-01

B chromosomes are small, heterochromatic chromosomes that are transmitted in a non-Mendelian manner. We have identified a stock of Drosophila melanogaster that recently (within the last decade) acquired an average of 10 B chromosomes per fly. These B chromosomes are transmitted by both males and females and can be maintained for multiple generations in a wild-type genetic background despite the fact that they cause high levels of 4th chromosome meiotic nondisjunction in females. Most curiously, these B chromosomes are mitotically unstable, suggesting either the absence of critical chromosomal sites or the inability of the meiotic or mitotic systems to cope with many additional chromosomes. These B chromosomes also contain centromeres and are primarily composed of the heterochromatic AATAT satellite sequence. Although the AATAT sequence comprises the majority of the 4th chromosome heterochromatin, the B chromosomes lack most, if not all, 4th chromosome euchromatin. Presumably as a consequence of their heterochromatic content, these B chromosomes significantly modify position-effect variegation in two separate reporter systems, acting as enhancers of variegation in one case and suppressors in the other. The identification of B chromosomes in a genetically tractable organism like D. melanogaster will facilitate studies of chromosome evolution and the analysis of the mechanisms by which meiotic and mitotic processes cope with additional chromosomes. PMID:24478336

Genetical Analysis of Chromosomal Interaction Effects on the Activities of the Glucose 6-Phosphate and 6-Phosphogluconate Dehydrogenases in DROSOPHILA MELANOGASTER

PubMed Central

Miyashita, Naohiko; Laurie-Ahlberg, C. C.

1984-01-01

By combining ten second and ten third chromosomes, we investigated chromosomal interaction with respect to the action of the modifier factors on G6PD and 6PGD activities in Drosophila melanogaster. Analysis of variance revealed that highly significant chromosomal interaction exists for both enzyme activities. From the estimated variance components, it was concluded that the variation in enzyme activity attributed to the interaction is as great as the variation attributed to the second chromosome but less than attributed to the third chromosome. The interaction is not explained by the variation of body size (live weight). The interaction is generated from both the lack of correlation of second chromosomes for third chromosome backgrounds and the heterogeneous variance of second chromosomes for different third chromosome backgrounds. Large and constant correlation between G6PD and 6PGD activities were found for third chromosomes with any second chromosome background, whereas the correlations for second chromosomes were much smaller and varied considerably with the third chromosome background. This result suggests that the activity modifiers on the second chromosome are under the influence of third chromosome factors. PMID:6425115

Degeneration of the Y chromosome in evolutionary aging models

NASA Astrophysics Data System (ADS)

Lobo, M. P.; Onody, R. N.

2005-06-01

The Y chromosomes are genetically degenerated and do not recombine with their matching partners X. Recombination of XX pairs is pointed out as the key factor for the Y chromosome degeneration. However, there is an additional evolutionary force driving sex-chromosomes evolution. Here we show this mechanism by means of two different evolutionary models, in which sex chromosomes with non-recombining XX and XY pairs of chromosomes is considered. Our results show three curious effects. First, we observed that even when both XX and XY pairs of chromosomes do not recombine, the Y chromosomes still degenerate. Second, the accumulation of mutations on Y chromosomes followed a completely different pattern then those accumulated on X chromosomes. And third, the models may differ with respect to sexual proportion. These findings suggest that a more primeval mechanism rules the evolution of Y chromosomes due exclusively to the sex-chromosomes asymmetry itself, i.e., the fact that Y chromosomes never experience female bodies. Over aeons, natural selection favored X chromosomes spontaneously, even if at the very beginning of evolution, both XX and XY pairs of chromosomes did not recombine.

Technique of laser chromosome welding for chromosome repair and artificial chromosome creation.

PubMed

Huang, Yao-Xiong; Li, Lin; Yang, Liu; Zhang, Yi

2018-04-01

Here we report a technique of laser chromosome welding that uses a violet pulse laser micro-beam for welding. The technique can integrate any size of a desired chromosome fragment into recipient chromosomes by combining with other techniques of laser chromosome manipulation such as chromosome cutting, moving, and stretching. We demonstrated that our method could perform chromosomal modifications with high precision, speed and ease of use in the absence of restriction enzymes, DNA ligases and DNA polymerases. Unlike the conventional methods such as de novo artificial chromosome synthesis, our method has no limitation on the size of the inserted chromosome fragment. The inserted DNA size can be precisely defined and the processed chromosome can retain its intrinsic structure and integrity. Therefore, our technique provides a high quality alternative approach to directed genetic recombination, and can be used for chromosomal repair, removal of defects and artificial chromosome creation. The technique may also have applicability on the manipulation and extension of large pieces of synthetic DNA.

Identification of Prostate Cancer Predisposition Genes on the Y Chromosome

DTIC Science & Technology

2017-10-01

sequencing was submitted. We used available Utah data for ~1,000 Y chromosome SNPs on 80 high risk Y chromosomes and 150 low risk Y chromosomes with some Y...chromosome genotype data available . The set of ~1,000 SNPs was used to perform a phylogenetic analysis of the high vs low r isk Y chromosomes; some...SNPs on a set of 80 high risk Y chromosomes and a set of 150 low risk Y chromosomes with some Y chromosome genotype data available . We identified

Chromosome heteromorphism quantified by high-resolution bivariate flow karyotyping.

PubMed Central

Trask, B; van den Engh, G; Mayall, B; Gray, J W

1989-01-01

Maternal and paternal homologues of many chromosome types can be differentiated on the basis of their peak position in Hoechst 33258 versus chromomycin A3 bivariate flow karyotypes. We demonstrate here the magnitude of DNA content differences among normal chromosomes of the same type. Significant peak-position differences between homologues were observed for an average of four chromosome types in each of the karyotypes of 98 different individuals. The frequency of individuals with differences in homologue peak positions varied among chromosome types: e.g., chromosome 15, 61%; chromosome 3, 4%. Flow karyotypes of 33 unrelated individuals were compared to determine the range of peak position among normal chromosomes. Chromosomes Y, 21, 22, 15, 16, 13, 14, and 19 were most heteromorphic, and chromosomes 2-8 and X were least heteromorphic. The largest chromosome 21 was 45% larger than the smallest 21 chromosome observed. The base composition of the variable regions differed among chromosome types. DNA contents of chromosome variants determined from flow karyotypes were closely correlated to measurements of DNA content made of gallocyanin chrome alum-stained metaphase chromosomes on slides. Fluorescence in situ hybridization with chromosome-specific repetitive sequences indicated that variability in their copy number is partly responsible for peak-position variability in some chromosomes. Heteromorphic chromosomes are identified for which parental flow karyotype information will be essential if de novo rearrangements resulting in small DNA content changes are to be detected with flow karyotyping. Images Figure 5 PMID:2479266

Mechanisms and Regulation of Mitotic Recombination in Saccharomyces cerevisiae

PubMed Central

Symington, Lorraine S.; Rothstein, Rodney; Lisby, Michael

2014-01-01

Homology-dependent exchange of genetic information between DNA molecules has a profound impact on the maintenance of genome integrity by facilitating error-free DNA repair, replication, and chromosome segregation during cell division as well as programmed cell developmental events. This chapter will focus on homologous mitotic recombination in budding yeast Saccharomyces cerevisiae. However, there is an important link between mitotic and meiotic recombination (covered in the forthcoming chapter by Hunter et al. 2015) and many of the functions are evolutionarily conserved. Here we will discuss several models that have been proposed to explain the mechanism of mitotic recombination, the genes and proteins involved in various pathways, the genetic and physical assays used to discover and study these genes, and the roles of many of these proteins inside the cell. PMID:25381364

An easy “SteamDrop” method for high quality plant chromosome preparation

PubMed Central

2014-01-01

Background The chromosome preparation is a crucial step for obtaining satisfactory results in molecular cytogenetic researches. The preparation of plant chromosomes for molecular cytogenetic purposes remains a challenge for some species. In contrast to human chromosome preparation, the processes occurring during plant chromosome preparation and causing chromosome spreading are still poorly understood. Results We studied the dynamics of plant chromosome spreading after dropping cell suspension on slides. We showed that steam stimulates cytoplasm hydrolysis and rapid chromosome spreading and that chromosomes stretch during this chromosome spreading. Based on these observations, we developed a novel method, named “SteamDrop”, for the preparation of well-spread mitotic and pachytene chromosomes and successfully used it for 28 plant species with large and small chromosomes. We applied cell suspensions in ethanol instead of the commonly used ethanol/acetic acid fixative. Mitotic and meiotic chromosomes prepared via “SteamDrop” were used in fluorescent in situ hybridization (FISH) experiments with repetitive and unique DNA probes. Long storage of cell suspensions in ethanol did not impair the quality of chromosome preparations. Conclusion The SteamDrop procedure provides a robust and routine method for high quality plant chromosome preparations. The method can be applied for metaphase as well as pachytene chromosome preparation in wide range of species. The chromosomes prepared by SteamDrop are well suitable for repetitive and unique DNA visualization. PMID:24602284

Identification of the facultative heterochromatic X chromosome in females of 25 rodent species.

PubMed

Kanda, N; Yosida, T H

1979-01-01

Treatment of the chromosomes of 25 rodent species with a 50 degrees C hypotonic solution and Giemsa staining permitted identification of the heterochromatic X chromosome in 24 species. With this technique, the facultative of the heterochromatic X chromosome or the facultative portion of large, composite-type X chromosoms is stained darker than the other chromosomes, allowing it to be distinguished from the homologous euchromatic X chromosome in female metaphase cells. Intense staining of the single X chromosome was not observed in male metaphase cells. It is suggested that this differential staining of one of the two X chromosomes might be due to qualitative differences in chromosomal proteins rather than to differences in the degree of chromosomal condensation or in DNA base sequence.

Development of chromosome-specific markers with high polymorphism for allotetraploid cotton based on genome-wide characterization of simple sequence repeats in diploid cottons (Gossypium arboreum L. and Gossypium raimondii Ulbrich).

PubMed

Lu, Cairui; Zou, Changsong; Zhang, Youping; Yu, Daoqian; Cheng, Hailiang; Jiang, Pengfei; Yang, Wencui; Wang, Qiaolian; Feng, Xiaoxu; Prosper, Mtawa Andrew; Guo, Xiaoping; Song, Guoli

2015-02-06

Tetraploid cotton contains two sets of homologous chromosomes, the At- and Dt-subgenomes. Consequently, many markers in cotton were mapped to multiple positions during linkage genetic map construction, posing a challenge to anchoring linkage groups and mapping economically-important genes to particular chromosomes. Chromosome-specific markers could solve this problem. Recently, the genomes of two diploid species were sequenced whose progenitors were putative contributors of the At- and Dt-subgenomes to tetraploid cotton. These sequences provide a powerful tool for developing chromosome-specific markers given the high level of synteny among tetraploid and diploid cotton genomes. In this study, simple sequence repeats (SSRs) on each chromosome in the two diploid genomes were characterized. Chromosome-specific SSRs were developed by comparative analysis and proved to distinguish chromosomes. A total of 200,744 and 142,409 SSRs were detected on the 13 chromosomes of Gossypium arboreum L. and Gossypium raimondii Ulbrich, respectively. Chromosome-specific SSRs were obtained by comparing SSR flanking sequences from each chromosome with those from the other 25 chromosomes. The average was 7,996 per chromosome. To confirm their chromosome specificity, these SSRs were used to distinguish two homologous chromosomes in tetraploid cotton through linkage group construction. The chromosome-specific SSRs and previously-reported chromosome markers were grouped together, and no marker mapped to another homologous chromosome, proving that the chromosome-specific SSRs were unique and could distinguish homologous chromosomes in tetraploid cotton. Because longer dinucleotide AT-rich repeats were the most polymorphic in previous reports, the SSRs on each chromosome were sorted by motif type and repeat length for convenient selection. The primer sequences of all chromosome-specific SSRs were also made publicly available. Chromosome-specific SSRs are efficient tools for chromosome identification by anchoring linkage groups to particular chromosomes during genetic mapping and are especially useful in mapping of qualitative-trait genes or quantitative trait loci with just a few markers. The SSRs reported here will facilitate a number of genetic and genomic studies in cotton, including construction of high-density genetic maps, positional gene cloning, fingerprinting, and genetic diversity and comparative evolutionary analyses among Gossypium species.

PinX1 is recruited to the mitotic chromosome periphery by Nucleolin and facilitates chromosome congression.

PubMed

Li, Na; Yuan, Kai; Yan, Feng; Huo, Yuda; Zhu, Tongge; Liu, Xing; Guo, Zhen; Yao, Xuebiao

2009-06-19

Mitotic chromosome movements are orchestrated by interactions between spindle microtubules and chromosomes. It is well known that kinetochore is the major site where microtubule-chromosome attachment occurs. However, the functions of other domains of chromosome such as chromosome periphery have remained elusive. Our previous studies show that PinX1 distributes to chromosome periphery and kinetochore during mitosis, and harbors the microtubule binding activity. Here we report that PinX1 interacts with Nucleolin, a chromosome periphery protein, through its C-termini. Deconvolution microscopic analyses show PinX1 mainly co-localizes with Nucleolin at chromosome periphery in prometaphase. Moreover, depletion of Nucleolin abolishes chromosome periphery localizations of PinX1, suggesting a functional interrelationship between PinX1 and Nucleolin. Importantly, repression of PinX1 and Nucleolin abrogates chromosome segregation in real-time mitosis, validating the functional importance of PinX1-Nucleolin interaction. We propose PinX1 is recruited to chromosome periphery by Nucleolin and a complex of PinX1 and Nucleolin is essential for faithful chromosome congression.

The ZW sex microchromosomes of an Australian dragon lizard share no homology with those of other reptiles or birds.

PubMed

Ezaz, Tariq; Moritz, Benjamin; Waters, Paul; Marshall Graves, Jennifer A; Georges, Arthur; Sarre, Stephen D

2009-01-01

Reptiles show a diverse array of sex chromosomal systems but, remarkably, the Z sex chromosomes of chicken are homologous to the ZW sex chromosomes of a species of gecko, Gekko hokouensis, suggesting an ancient but common origin. This is in contrast to the ZW sex chromosomes of snakes and a species of soft-shelled turtle, Pelodiscus sinensis, which are nonhomologous to those of chicken or each other and appear to have been independently derived. In this paper, we determine what homology, if any, the sex chromosomes of the Australian dragon lizard Pogona vitticeps shares with those of snake and chicken by mapping the dragon homologs of five snake Z chromosome genes (WAC, KLF6, TAX1BP1, RAB5A, and CTNNB1) and five chicken Z chromosome genes (ATP5A1, GHR, DMRT1, CHD1, and APTX) to chromosomes in the dragon. The dragon homologs of snake and chicken sex chromosome genes map to chromosomes 6 and chromosome 2, respectively, in the dragon and that DMRT1, the bird sex-determining gene, is not located on the sex chromosomes of P. vitticeps. Indeed, our data show that the dragon homolog to the chicken Z chromosome is likely to be wholly contained within chromosome 2 in P. vitticeps, which suggests that the sex-determining factor in P. vitticeps is not the sex-determining gene of chicken. Homology between chicken Z chromosome and G. hokouensis ZW chromosome pairs has been interpreted as retention of ancient ZW sex chromosomes in which case the nonhomologous sex chromosomes of snake and dragons would be independently derived. Our data add another case of independently derived sex chromosomes in a squamate reptile, which makes retention of ancient sex chromosome homology in the squamates less plausible. Alternatively, the conservation between the bird Z chromosome and the G. hokouensis ZW chromosomes pairs is coincidental, may be an example of convergent evolution, its status as the Z chromosome having been independently derived in birds and G. hokouensis.

X-derived marker chromosome in patient with mosaic Turner syndrome and Dandy-Walker syndrome: a case report.

PubMed

Telepova, Alena S; Romanenko, Svetlana A; Lemskaya, Natalya A; Maksimova, Yulia V; Shorina, Asia R; Yudkin, Dmitry V

2017-01-01

Small supernumerary marker chromosomes can be derived from autosomes and sex chromosomes and can accompany chromosome pathologies, such as Turner syndrome. Here, we present a case report of a patient with mosaic Turner syndrome and Dandy-Walker syndrome carrying a marker chromosome. We showed the presence of the marker chromosome in 33.8% of blood cells. FISH of the probe derived from the marker chromosome by microdissection revealed that it originated from the centromeric region of chromosome X. Additionally, we showed no telomeric sequences and no XIST sequence in the marker chromosome. This is the first report of these two syndromes accompanied by the presence of a marker chromosome. Marker chromosome was X-derived and originated from centromeric region. Patient has mild symptoms but there is no XIST gene in marker chromosome. CPG137. Registered 03 March 2017.

The gametocidal chromosome as a tool for chromosome manipulation in wheat.

PubMed

Endo, T R

2007-01-01

Many alien chromosomes have been introduced into common wheat (the genus Triticum) from related wild species (the genus Aegilops). Some alien chromosomes have unique genes that secure their existence in the host by causing chromosome breakage in the gametes lacking them. Such chromosomes or genes, called gametocidal (Gc) chromosomes or Gc genes, are derived from different genomes (C, S, S(l) and M(g)) and belong to three different homoeologous groups 2, 3 and 4. The Gc genes of the C and M(g) genomes induce mild, or semi-lethal, chromosome mutations in euploid and alien addition lines of common wheat. Thus, induced chromosomal rearrangements have been identified and established in wheat stocks carrying deletions of wheat and alien (rye and barley) chromosomes or wheat-alien translocations. The gametocidal chromosomes isolated in wheat to date are reviewed here, focusing on their feature as a tool for chromosome manipulation.

Somatic Crossing over in GLYCINE MAX (L.) Merrill: Effect of Some Inhibitors of DNA Synthesis on the Induction of Somatic Crossing over and Point Mutations.

PubMed

Vig, B K

1973-04-01

Glycine max (soybean) is the only known higher plant with a definitely established occurrence of somatic crossing over. This material lends itself to the analysis of somatic crossing over, gross chromosomal aberrations and mutations, all of which may be induced by the same treatment of the mutagen given to seeds. This is made possible because gene Y(11) for chlorophyll development in the variety L65-1237 is incompletely dominant over its allele y(11), so that twin or double spots composed of a dark green (Y(11)Y(11)) and a yellow (y(11)y(11)) component can be observed adjacent to and as mirror images of each other on the light green Y(11)y(11) leaves in the areas of complementary exchange for these genes. Lack of growth of either component of this double spot as well as several types of chromosomal disturbances give rise to single spots resembling phenotypes of y(11)y(11) or Y(11)Y(11) leaves. Point mutations can be studied by looking for green sectors originating from Y(11)y(11) genotype on the y(11)y(11) plants. Seeds obtained from heterozygous plants were treated with caffeine, cytosine arabinoside, actinomycin D and 5-fluoro-deoxyuridine, all known inhibitors of DNA synthesis, and puromycin, an inhibitor of synthesis of proteins. The treatments with caffeine and actinomycin D increased the frequency of somatic crossing over as measured by the frequency of double spots on Y(11)y(11) leaves, but cytosine arabinoside, 5-fluorodeoxyuridine and puromycin did not. Thus somatic crossing over was induced only by those chemicals which are known to allow rejoining of chromosomes, thereby suggesting a correlation between the two phenomena. These observations indicate that it is not the mere inhibition of DNA synthesis, but some rather more specific event in DNA repair which is responsible for complementary exchanges. Some of these results differ from studies carried out with fungi. The main effect of all chemicals tested, except caffeine and actinomycin D, was inferred to be the production of deletions in Y(11)y(11) plants which raised the frequency of single (dark green or yellow) spots relative to the doubles. Caffeine was the only chemical which constantly increased the frequency of specific point mutations. In the control material, the great majority of spots are found on the upper surface of the leaf. This picture could not be changed in any of the treated materials, thus indicating uniform resistance of spongy mesophyll tissue to the mutagens applied.

Chromosome painting reveals asynaptic full alignment of homologs and HIM-8-dependent remodeling of X chromosome territories during Caenorhabditis elegans meiosis.

PubMed

Nabeshima, Kentaro; Mlynarczyk-Evans, Susanna; Villeneuve, Anne M

2011-08-01

During early meiotic prophase, a nucleus-wide reorganization leads to sorting of chromosomes into homologous pairs and to establishing associations between homologous chromosomes along their entire lengths. Here, we investigate global features of chromosome organization during this process, using a chromosome painting method in whole-mount Caenorhabditis elegans gonads that enables visualization of whole chromosomes along their entire lengths in the context of preserved 3D nuclear architecture. First, we show that neither spatial proximity of premeiotic chromosome territories nor chromosome-specific timing is a major factor driving homolog pairing. Second, we show that synaptonemal complex-independent associations can support full lengthwise juxtaposition of homologous chromosomes. Third, we reveal a prominent elongation of chromosome territories during meiotic prophase that initiates prior to homolog association and alignment. Mutant analysis indicates that chromosome movement mediated by association of chromosome pairing centers (PCs) with mobile patches of the nuclear envelope (NE)-spanning SUN-1/ZYG-12 protein complexes is not the primary driver of territory elongation. Moreover, we identify new roles for the X chromosome PC (X-PC) and X-PC binding protein HIM-8 in promoting elongation of X chromosome territories, separable from their role(s) in mediating local stabilization of pairing and association of X chromosomes with mobile SUN-1/ZYG-12 patches. Further, we present evidence that HIM-8 functions both at and outside of PCs to mediate chromosome territory elongation. These and other data support a model in which synapsis-independent elongation of chromosome territories, driven by PC binding proteins, enables lengthwise juxtaposition of chromosomes, thereby facilitating assessment of their suitability as potential pairing partners.

Chromosome Painting Reveals Asynaptic Full Alignment of Homologs and HIM-8–Dependent Remodeling of X Chromosome Territories during Caenorhabditis elegans Meiosis

PubMed Central

Nabeshima, Kentaro; Mlynarczyk-Evans, Susanna; Villeneuve, Anne M.

2011-01-01

During early meiotic prophase, a nucleus-wide reorganization leads to sorting of chromosomes into homologous pairs and to establishing associations between homologous chromosomes along their entire lengths. Here, we investigate global features of chromosome organization during this process, using a chromosome painting method in whole-mount Caenorhabditis elegans gonads that enables visualization of whole chromosomes along their entire lengths in the context of preserved 3D nuclear architecture. First, we show that neither spatial proximity of premeiotic chromosome territories nor chromosome-specific timing is a major factor driving homolog pairing. Second, we show that synaptonemal complex-independent associations can support full lengthwise juxtaposition of homologous chromosomes. Third, we reveal a prominent elongation of chromosome territories during meiotic prophase that initiates prior to homolog association and alignment. Mutant analysis indicates that chromosome movement mediated by association of chromosome pairing centers (PCs) with mobile patches of the nuclear envelope (NE)–spanning SUN-1/ZYG-12 protein complexes is not the primary driver of territory elongation. Moreover, we identify new roles for the X chromosome PC (X-PC) and X-PC binding protein HIM-8 in promoting elongation of X chromosome territories, separable from their role(s) in mediating local stabilization of pairing and association of X chromosomes with mobile SUN-1/ZYG-12 patches. Further, we present evidence that HIM-8 functions both at and outside of PCs to mediate chromosome territory elongation. These and other data support a model in which synapsis-independent elongation of chromosome territories, driven by PC binding proteins, enables lengthwise juxtaposition of chromosomes, thereby facilitating assessment of their suitability as potential pairing partners. PMID:21876678

Molecular Diversity and Population Structure of a Worldwide Collection of Cultivated Tetraploid Alfalfa (Medicago sativa subsp. sativa L.) Germplasm as Revealed by Microsatellite Markers

PubMed Central

Qiang, Haiping; Chen, Zhihong; Zhang, Zhengli; Wang, Xuemin; Gao, Hongwen; Wang, Zan

2015-01-01

Information on genetic diversity and population structure of a tetraploid alfalfa collection might be valuable in effective use of the genetic resources. A set of 336 worldwide genotypes of tetraploid alfalfa (Medicago sativa subsp. sativa L.) was genotyped using 85 genome-wide distributed SSR markers to reveal the genetic diversity and population structure in the alfalfa. Genetic diversity analysis identified a total of 1056 alleles across 85 marker loci. The average expected heterozygosity and polymorphism information content values were 0.677 and 0.638, respectively, showing high levels of genetic diversity in the cultivated tetraploid alfalfa germplasm. Comparison of genetic characteristics across chromosomes indicated regions of chromosomes 2 and 3 had the highest genetic diversity. A higher genetic diversity was detected in alfalfa landraces than that of wild materials and cultivars. Two populations were identified by the model-based population structure, principal coordinate and neighbor-joining analyses, corresponding to China and other parts of the world. However, lack of strictly correlation between clustering and geographic origins suggested extensive germplasm exchanges of alfalfa germplasm across diverse geographic regions. The quantitative analysis of the genetic diversity and population structure in this study could be useful for genetic and genomic analysis and utilization of the genetic variation in alfalfa breeding. PMID:25901573

Persistence of chromosome aberrations in mice acutely exposed to 56Fe+26 ions.

PubMed

Tucker, James D; Marples, Brian; Ramsey, Marilyn J; Lutze-Mann, Louise H

2004-06-01

Space exploration has the potential to yield exciting and significant discoveries, but it also brings with it many risks for flight crews. Among the less well studied of these are health effects from space radiation, which includes the highly charged, energetic particles of elements with high atomic numbers that constitute the galactic cosmic rays. In this study, we demonstrated that 1 Gy iron ions acutely administered to mice in vivo resulted in highly complex chromosome damage. We found that all types of aberrations, including dicentrics as well as translocations, insertions and acentric fragments, disappear rapidly with time after exposure, probably as a result of the death of heavily damaged cells, i.e. cells with multiple and/or complex aberrations. In addition, numerous cells have apparently simple exchanges as their only aberrations, and these cells appear to survive longer than heavily damaged cells. Eight weeks after exposure, the frequency of cells showing cytogenetic damage was reduced to less than 20% of the levels evident at 1 week, with little further decline apparent over an additional 8 weeks. These results indicate that exposure to 1 Gy iron ions produces heavily damaged cells, a small fraction of which appear to be capable of surviving for relatively long periods. The health effects of exposure to high-LET radiation in humans on prolonged space flights should remain a matter of concern.

The role of cytogenetic tests in detection and prevention of cancer.

PubMed

Bishun, N P

1981-01-01

Although simplified and improved techniques have increased at a fast rate in recent years, a great number of compounds released into our environment still remain untested. It has been estimated that between 80-90% of human cancer is a result of exposure to such compounds, and if by the application of short-term mutagenic tests, the use of many of these compounds can be severely restricted, an enormous impact can be made on the solution of human health problems. Batteries of mutagenic tests have established an empirical relationship between mutagenisis and carcinogenisis, and, in view of the cost in terms of time and money, short-term tests are playing an important role in first detecting, and second, eliminating potential hazards in our environment. The use of bacteria and other unicellular organisms in these assay systems has met with much criticism; due to the fact that the DNA materials affected do not directly relate to that of man. However, in conjunction with other tests, utilizing human and other mammalian cells, firm conclusions can be drawn regarding the potential hazards of certain chemicals. Recent advances in cytogenetic tests (e.g., banding chromosomes and sister chromatid exchange) have improved the sensitivity of chromosomal tests and, in so doing, have rendered them more usual in the selecting out process that can reduce substantially the mutagenic and carcinogenic hazards caused by chemicals and other deleterious agents in the environment.

Differences in genotoxic activity of alpha-Ni3S2 on human lymphocytes from nickel-hypersensitized and nickel-unsensitized donors.

PubMed

Arrouijal, F Z; Marzin, D; Hildebrand, H F; Pestel, J; Haguenoer, J M

1992-05-01

The genotoxic activity of alpha-Ni3S2 was assessed on human lymphocytes from nickel-hypersensitized (SSL) and nickel-unsensitized (USL) subjects. Three genotoxicity tests were performed: the sister chromatid exchange (SCE) test, the metaphase analysis test and the micronucleus test. (i) The SCE test (3-100 micrograms/ml) showed a weak but statistically significant increase in the number of SCE in both lymphocyte types with respect to controls, USL presenting a slightly higher SCE incidence but only at one concentration. (ii) The metaphase analysis test demonstrated a high dose-dependent clastogenic activity of alpha-Ni3S2 in both lymphocyte types. The frequency of chromosomal anomalies was significantly higher in USL than in SSL for all concentrations applied. (iii) The micronucleus test confirmed the dose-dependent clastogenic activity of alpha-Ni3S2 and the differences already observed between USL and SSL, i.e. the number of cells with micronuclei was statistically higher in USL. Finally, the incorporation study with alpha-63Ni3S2 showed a higher uptake of its solubilized fraction by USL. This allows an explanation of the different genotoxic action of nickel on the two cell types. In this study we demonstrated that hypersensitivity has an influence on the incorporation of alpha-Ni3S2 and subsequently on the different induction of chromosomal aberrations in human lymphocytes.

Recombination and horizontal transfer of nodulation and ACC deaminase (acdS) genes within Alpha- and Betaproteobacteria nodulating legumes of the Cape Fynbos biome.

PubMed

Lemaire, Benny; Van Cauwenberghe, Jannick; Chimphango, Samson; Stirton, Charles; Honnay, Olivier; Smets, Erik; Muasya, A Muthama

2015-11-01

The goal of this work is to study the evolution and the degree of horizontal gene transfer (HGT) within rhizobial genera of both Alphaproteobacteria (Mesorhizobium, Rhizobium) and Betaproteobacteria (Burkholderia), originating from South African Fynbos legumes. By using a phylogenetic approach and comparing multiple chromosomal and symbiosis genes, we revealed conclusive evidence of high degrees of horizontal transfer of nodulation genes among closely related species of both groups of rhizobia, but also among species with distant genetic backgrounds (Rhizobium and Mesorhizobium), underscoring the importance of lateral transfer of symbiosis traits as an important evolutionary force among rhizobia of the Cape Fynbos biome. The extensive exchange of symbiosis genes in the Fynbos is in contrast with a lack of significant events of HGT among Burkholderia symbionts from the South American Cerrado and Caatinga biome. Furthermore, homologous recombination among selected housekeeping genes had a substantial impact on sequence evolution within Burkholderia and Mesorhizobium. Finally, phylogenetic analyses of the non-symbiosis acdS gene in Mesorhizobium, a gene often located on symbiosis islands, revealed distinct relationships compared to the chromosomal and symbiosis genes, suggesting a different evolutionary history and independent events of gene transfer. The observed events of HGT and incongruence between different genes necessitate caution in interpreting topologies from individual data types. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Telomere and ribosomal DNA repeats are chromosomal targets of the bloom syndrome DNA helicase

PubMed Central

Schawalder, James; Paric, Enesa; Neff, Norma F

2003-01-01

Background Bloom syndrome is one of the most cancer-predisposing disorders and is characterized by genomic instability and a high frequency of sister chromatid exchange. The disorder is caused by loss of function of a 3' to 5' RecQ DNA helicase, BLM. The exact role of BLM in maintaining genomic integrity is not known but the helicase has been found to associate with several DNA repair complexes and some DNA replication foci. Results Chromatin immunoprecipitation of BLM complexes recovered telomere and ribosomal DNA repeats. The N-terminus of BLM, required for NB localization, is the same as the telomere association domain of BLM. The C-terminus is required for ribosomal DNA localization. BLM localizes primarily to the non-transcribed spacer region of the ribosomal DNA repeat where replication forks initiate. Bloom syndrome cells expressing the deletion alleles lacking the ribosomal DNA and telomere association domains have altered cell cycle populations with increased S or G2/M cells relative to normal. Conclusion These results identify telomere and ribosomal DNA repeated sequence elements as chromosomal targets for the BLM DNA helicase during the S/G2 phase of the cell cycle. BLM is localized in nuclear bodies when it associates with telomeric repeats in both telomerase positive and negative cells. The BLM DNA helicase participates in genomic stability at ribosomal DNA repeats and telomeres. PMID:14577841

Evidence That BRCA1- or BRCA2-Associated Cancers Are Not Inevitable

PubMed Central

Levin, Bess; Lech, Denise; Friedenson, Bernard

2012-01-01

Inheriting a BRCA1 or BRCA2 gene mutation can cause a deficiency in repairing complex DNA damage. This step leads to genomic instability and probably contributes to an inherited predisposition to breast and ovarian cancer. Complex DNA damage has been viewed as an integral part of DNA replication before cell division. It causes temporary replication blocks, replication fork collapse, chromosome breaks and sister chromatid exchanges (SCEs). Chemical modification of DNA may also occur spontaneously as a byproduct of normal processes. Pathways containing BRCA1 and BRCA2 gene products are essential to repair spontaneous complex DNA damage or to carry out SCEs if repair is not possible. This scenario creates a theoretical limit that effectively means there are spontaneous BRCA1/2-associated cancers that cannot be prevented or delayed. However, much evidence for high rates of spontaneous DNA mutation is based on measuring SCEs by using bromodeoxyuridine (BrdU). Here we find that the routine use of BrdU has probably led to overestimating spontaneous DNA damage and SCEs because BrdU is itself a mutagen. Evidence based on spontaneous chromosome abnormalities and epidemiologic data indicates strong effects from exogenous mutagens and does not support the inevitability of cancer in all BRCA1/2 mutation carriers. We therefore remove a theoretical argument that has limited efforts to develop chemoprevention strategies to delay or prevent cancers in BRCA1/2 mutation carriers. PMID:22972572

LARG at chromosome 11q23 has functional characteristics of a tumor suppressor in human breast and colorectal cancer

PubMed Central

Ong, DCT; Ho, YM; Rudduck, C; Chin, K; Kuo, W-L; Lie, DKH; Chua, CLM; Tan, PH; Eu, KW; Seow-Choen, F; Wong, CY; Hong, GS; Gray, JW; Lee, ASG

2010-01-01

Deletion of 11q23–q24 is frequent in a diverse variety of malignancies, including breast and colorectal carcinoma, implicating the presence of a tumor suppressor gene at that chromosomal region. We examined a 6-Mb region on 11q23 by high-resolution deletion mapping, using both loss of heterozygosity analysis and customized microarray comparative genomic hybridization. LARG (leukemia-associated Rho guanine-nucleotide exchange factor) (also called ARHGEF12), identified from the analysed region, is frequently underexpressed in breast and colorectal carcinomas with a reduced expression observed in all breast cancer cell lines (n=11), in 12 of 38 (32%) primary breast cancers, 5 of 10 (50%) colorectal cell lines and in 20 of 37 (54%) primary colorectal cancers. Underexpression of the LARG transcript was significantly associated with genomic loss (P=0.00334). Hypermethylation of the LARG promoter was not detected in either breast or colorectal cancer, and treatment of four breast and four colorectal cancer cell lines with 5-aza-2′-deoxycytidine and/or trichostatin A did not result in a reactivation of LARG. Enforced expression of LARG in breast and colorectal cancer cells by stable transfection resulted in reduced cell proliferation and colony formation, as well as in a markedly slower cell migration rate in colorectal cancer cells, providing functional evidence for LARG as a candidate tumor suppressor gene. PMID:19734946

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

Harrison, F.L.; Rice, D.W. Jr.; Moore, D.H.

Traditional bioassays are unsuitable for assessing sublethal effects of low levels of radioactivity because mortality and phenotypic responses are not anticipated. We compared the usefulness of chromosomal aberration (CA) and sister chromatid exchange (SCE) induction as measures of low-level radiation effects in a sediment-dwelling marine worm, Neanthes arenaceodentata. Newly hatched larvae were exposed to two radiation exposure regimes. Groups of 100 larvae were exposed to either x rays delivered at high dose rates (0.7 Gy min/sup -1/) or to /sup 60/Co gamma rays delivered at low dose rates (4.8 X 10/sup -5/ to 1.2 X 10/sup -1/ Gy h/sup -1/).more » After irradiation, the larvae were exposed to 3 X 10/sup -5/M bromodeoxyuridine (BrdUrd) for 28 h (x-ray-irradiated larvae) or for 54 h (/sup 60/Co-irradiated larvae). Slides of larval cells were prepared for observation of CAs and SCEs. Frequencies of CAs were determined in first division cells; frequencies of SCEs were determined in second division cells. Results from x-ray irradiation indicated that dose-related increases occur in chromosome and chromatid deletions, but an x-ray dose greater than or equal to 2 Gy was required to observe a significant increase. Worm larvae receiving /sup 60/Co irradiation showed elevated SCE frequencies; a significant increase in SCE frequency was observed at 0.6 Gy. 49 references, 2 figures.« less

Monitoring Recombination During Meiosis in Budding Yeast.

PubMed

Owens, Shannon; Tang, Shangming; Hunter, Neil

2018-01-01

Homologous recombination is fundamental to sexual reproduction, facilitating accurate segregation of homologous chromosomes at the first division of meiosis, and creating novel allele combinations that fuel evolution. Following initiation of meiotic recombination by programmed DNA double-strand breaks (DSBs), homologous pairing and DNA strand exchange form joint molecule (JM) intermediates that are ultimately resolved into crossover and noncrossover repair products. Physical monitoring of the DNA steps of meiotic recombination in Saccharomyces cerevisiae (budding yeast) cultures undergoing synchronous meiosis has provided seminal insights into the molecular basis of meiotic recombination and affords a powerful tool for dissecting the molecular roles of recombination factors. This chapter describes a suit of electrophoretic and Southern hybridization techniques used to detect and quantify the DNA intermediates of meiotic recombination at recombination hotspots in budding yeast. DSBs and recombination products (crossovers and noncrossovers) are resolved using one-dimensional electrophoresis and distinguished by restriction site polymorphisms between the parental chromosomes. Psoralen cross-linking is used to stabilize branched JMs, which are resolved from linear species by native/native two-dimensional electrophoresis. Native/denaturing two-dimensional electrophoresis is employed to determine the component DNA strands of JMs and to measure the processing of DSBs. These techniques are generally applicable to any locus where the frequency of recombination is high enough to detect intermediates by Southern hybridization. © 2018 Elsevier Inc. All rights reserved.

Vibrio chromosomes share common history.

PubMed

Kirkup, Benjamin C; Chang, LeeAnn; Chang, Sarah; Gevers, Dirk; Polz, Martin F

2010-05-10

While most gamma proteobacteria have a single circular chromosome, Vibrionales have two circular chromosomes. Horizontal gene transfer is common among Vibrios, and in light of this genetic mobility, it is an open question to what extent the two chromosomes themselves share a common history since their formation. Single copy genes from each chromosome (142 genes from chromosome I and 42 genes from chromosome II) were identified from 19 sequenced Vibrionales genomes and their phylogenetic comparison suggests consistent phylogenies for each chromosome. Additionally, study of the gene organization and phylogeny of the respective origins of replication confirmed the shared history. Thus, while elements within the chromosomes may have experienced significant genetic mobility, the backbones share a common history. This allows conclusions based on multilocus sequence analysis (MLSA) for one chromosome to be applied equally to both chromosomes.

Micromechanics of human mitotic chromosomes

NASA Astrophysics Data System (ADS)

Sun, Mingxuan; Kawamura, Ryo; Marko, John F.

2011-02-01

Eukaryote cells dramatically reorganize their long chromosomal DNAs to facilitate their physical segregation during mitosis. The internal organization of folded mitotic chromosomes remains a basic mystery of cell biology; its understanding would likely shed light on how chromosomes are separated from one another as well as into chromosome structure between cell divisions. We report biophysical experiments on single mitotic chromosomes from human cells, where we combine micromanipulation, nano-Newton-scale force measurement and biochemical treatments to study chromosome connectivity and topology. Results are in accord with previous experiments on amphibian chromosomes and support the 'chromatin network' model of mitotic chromosome structure. Prospects for studies of chromosome-organizing proteins using siRNA expression knockdowns, as well as for differential studies of chromosomes with and without mutations associated with genetic diseases, are also discussed.

B-chromosome systems in the greater glider (Petauroides volans volans) (Marsupialia:Petauridae). I. B-chromosome distribution.

PubMed

McQuade, L R

1985-01-01

Variations in diploid chromosome number, due to the presence of B chromosomes, are found within the distribution of P. v. volans. B chromosomes vary in number between one and eight per animal, are mitotically stable in various body tissues and, unlike the Y chromosome in male P. v. volans, are not eliminated from bone marrow cells. Animals possessing B chromosomes have a distinct distribution, and it appears that a stable equilibrium between the forces of B chromosome accumulation or elimination is operating in those populations possessing these chromosomes.

[Effects of chlorobenzene stress on seedling growth and cell division of Vicia faba].

PubMed

Liu, Wan; Zhou, Qixing; Li, Peijun; Sun, Tieheng; Tai, Peidong; Xu, Huaxia; Zhang, Chungui; Zhang, Hairong

2003-04-01

Effects of 1, 2, 4-trichlorobenzene (TCB) stress on seedling growth, cell division and chromosomal aberration frequency of root-tip cells of Vicia faba were studied. The results indicated that the growth of the root length and mitotic index of root tip cells were successively decreased and even stopped with the increase of TCB concentrations and treatment duration. Numerical and structural chromosomal aberrations at metaphase and anaphase of root-tip cells in Vicia faba seedlings were produced by 50-300 micrograms.g-1 TCB treatment for 12-96 h. The percentage of c-mitosis, chromosomal bridge and chromosomal asymmetry array in root tip cells exposed to 50-100 micrograms.g-1 TCB for 12-24 h was up to 1.0-10.3%. The percentage of chromosomal stickness (S), chromosomal stickiness + chromosomal breakage (S + B), chromosomal stickness + chromosomal ring (S + R), chromosomal stickiness + chromosomal asymmetry array (S + A) and chromosomal stickness + chromosomal bridge (S + Be) in root tip cells reached 47.9-88.9%, and 18.1-29.6% for different kinds of chromosomal breakage at 300 micrograms.g-1 TCB for 12-96 h. Thus, the chromosomal aberration of root tip cells in Vicia faba seedlings could be used as a sensitive biomarker of monitoring soil contaminated with TCB.

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.

Characterization of chromosomal architecture in Arabidopsis by chromosome conformation capture

PubMed Central

2013-01-01

Background The packaging of long chromatin fibers in the nucleus poses a major challenge, as it must fulfill both physical and functional requirements. Until recently, insights into the chromosomal architecture of plants were mainly provided by cytogenetic studies. Complementary to these analyses, chromosome conformation capture technologies promise to refine and improve our view on chromosomal architecture and to provide a more generalized description of nuclear organization. Results Employing circular chromosome conformation capture, this study describes chromosomal architecture in Arabidopsis nuclei from a genome-wide perspective. Surprisingly, the linear organization of chromosomes is reflected in the genome-wide interactome. In addition, we study the interplay of the interactome and epigenetic marks and report that the heterochromatic knob on the short arm of chromosome 4 maintains a pericentromere-like interaction profile and interactome despite its euchromatic surrounding. Conclusion Despite the extreme condensation that is necessary to pack the chromosomes into the nucleus, the Arabidopsis genome appears to be packed in a predictive manner, according to the following criteria: heterochromatin and euchromatin represent two distinct interactomes; interactions between chromosomes correlate with the linear position on the chromosome arm; and distal chromosome regions have a higher potential to interact with other chromosomes. PMID:24267747

Targeted tandem duplication of a large chromosomal segment in Aspergillus oryzae.

PubMed

Takahashi, Tadashi; Sato, Atsushi; Ogawa, Masahiro; Hanya, Yoshiki; Oguma, Tetsuya

2014-08-01

We describe here the first successful construction of a targeted tandem duplication of a large chromosomal segment in Aspergillus oryzae. The targeted tandem chromosomal duplication was achieved by using strains that had a 5'-deleted pyrG upstream of the region targeted for tandem chromosomal duplication and a 3'-deleted pyrG downstream of the target region. Consequently,strains bearing a 210-kb targeted tandem chromosomal duplication near the centromeric region of chromosome 8 and strains bearing a targeted tandem chromosomal duplication of a 700-kb region of chromosome 2 were successfully constructed. The strains bearing the tandem chromosomal duplication were efficiently obtained from the regenerated protoplast of the parental strains. However, the generation of the chromosomal duplication did not depend on the introduction of double-stranded breaks(DSBs) by I-SceI. The chromosomal duplications of these strains were stably maintained after five generations of culture under nonselective conditions. The strains bearing the tandem chromosomal duplication in the 700-kb region of chromosome 2 showed highly increased protease activity in solid-state culture, indicating that the duplication of large chromosomal segments could be a useful new breeding technology and gene analysis method.

The chromokinesin Kid is necessary for chromosome arm orientation and oscillation, but not congression, on mitotic spindles

PubMed Central

Levesque, Aime A.; Compton, Duane A.

2001-01-01

Chromokinesins have been postulated to provide the polar ejection force needed for chromosome congression during mitosis. We have evaluated that possibility by monitoring chromosome movement in vertebrate-cultured cells using time-lapse differential interference contrast microscopy after microinjection with antibodies specific for the chromokinesin Kid. 17.5% of cells injected with Kid-specific antibodies have one or more chromosomes that remain closely opposed to a spindle pole and fail to enter anaphase. In contrast, 82.5% of injected cells align chromosomes in metaphase, progress to anaphase, and display chromosome velocities not significantly different from control cells. However, injected cells lack chromosome oscillations, and chromosome orientation is atypical because chromosome arms extend toward spindle poles during both congression and metaphase. Furthermore, chromosomes cluster into a mass and fail to oscillate when Kid is perturbed in cells containing monopolar spindles. These data indicate that Kid generates the polar ejection force that pushes chromosome arms away from spindle poles in vertebrate-cultured cells. This force increases the efficiency with which chromosomes make bipolar spindle attachments and regulates kinetochore activities necessary for chromosome oscillation, but is not essential for chromosome congression. PMID:11564754

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

Flow karyotyping and sorting of human chromosomes

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

Gray, J.W.; Lucas, J.; Peters, D.

1986-07-16

Flow cytometry and sorting are becoming increasingly useful as tools for chromosome classfication and for the detection of numerical and structural chromosome aberrations. Chromosomes of a single type can be purified with these tools to facilitate gene mapping or production of chromosome specific recombinant DNA libraries. For analysis of chromosomes with flow cytometry, the chromosomes are extracted from mitotic cells, stained with one or more fluorescent dyes and classified one-by-one according to their dye content(s). Thus, the flow approach is fundamentally different than conventional karyotyping where chromosomes are classified within the context of a metaphase spread. Flow sorting allows purificationmore » of chromosomes that can be distinguished flow cytometrically. The authors describe the basic principles of flow cytometric chromosome classification i.e. flow karyotyping, and chromosome sorting and describe several applications. 30 refs., 8 figs.« less

Unrepaired DNA damage facilitates elimination of uniparental chromosomes in interspecific hybrid cells

PubMed Central

Wang, Zheng; Yin, Hao; Lv, Lei; Feng, Yingying; Chen, Shaopeng; Liang, Junting; Huang, Yun; Jiang, Xiaohua; Jiang, Hanwei; Bukhari, Ihtisham; Wu, Lijun; Cooke, Howard J; Shi, Qinghua

2014-01-01

Elimination of uniparental chromosomes occurs frequently in interspecific hybrid cells. For example, human chromosomes are always eliminated during clone formation when human cells are fused with mouse cells. However, the underlying mechanisms are still elusive. Here, we show that the elimination of human chromosomes in human–mouse hybrid cells is accompanied by continued cell division at the presence of DNA damage on human chromosomes. Deficiency in DNA damage repair on human chromosomes occurs after cell fusion. Furthermore, increasing the level of DNA damage on human chromosomes by irradiation accelerates human chromosome loss in hybrid cells. Our results indicate that the elimination of human chromosomes in human–mouse hybrid cells results from unrepaired DNA damage on human chromosomes. We therefore provide a novel mechanism underlying chromosome instability which may facilitate the understanding of carcinogenesis. PMID:24608870

Development of a quantitative pachytene chromosome map and its unification with somatic chromosome and linkage maps of rice (Oryza sativa L.).

PubMed

Ohmido, Nobuko; Iwata, Aiko; Kato, Seiji; Wako, Toshiyuki; Fukui, Kiichi

2018-01-01

A quantitative pachytene chromosome map of rice (Oryza sativa L.) was developed using imaging methods. The map depicts not only distribution patterns of chromomeres specific to pachytene chromosomes, but also the higher order information of chromosomal structures, such as heterochromatin (condensed regions), euchromatin (decondensed regions), the primary constrictions (centromeres), and the secondary constriction (nucleolar organizing regions, NOR). These features were image analyzed and quantitatively mapped onto the map by Chromosome Image Analyzing System ver. 4.0 (CHIAS IV). Correlation between H3K9me2, an epigenetic marker and formation and/or maintenance of heterochromatin, thus was, clearly visualized. Then the pachytene chromosome map was unified with the existing somatic chromosome and linkage maps by physically mapping common DNA markers among them, such as a rice A genome specific tandem repeat sequence (TrsA), 5S and 45S ribosomal RNA genes, five bacterial artificial chromosome (BAC) clones, four P1 bacteriophage artificial chromosome (PAC) clones using multicolor fluorescence in situ hybridization (FISH). Detailed comparison between the locations of the DNA probes on the pachytene chromosomes using multicolor FISH, and the linkage map enabled determination of the chromosome number and short/long arms of individual pachytene chromosomes using the chromosome number and arm assignment designated for the linkage map. As a result, the quantitative pachytene chromosome map was unified with two other major rice chromosome maps representing somatic prometaphase chromosomes and genetic linkages. In conclusion, the unification of the three rice maps serves as an indispensable basic information, not only for an in-depth comparison between genetic and chromosomal data, but also for practical breeding programs.

Chromosome painting reveals specific patterns of chromosome occurrence in mitomycin C- and diethylstilboestrol-induced micronuclei.

PubMed

Fauth, E; Scherthan, H; Zankl, H

2000-11-01

Cultures of human blood lymphocytes from three subjects were incubated with the clastogen mitomycin C (MMC, 500 ng/ml) and the aneugen diethylstilboestrol (DES, 80 microM) 23 h before harvesting, to induce formation of micronuclei (MN) and numerical and structural alterations in metaphase chromosomes. We used fluorescence in situ hybridization (FISH) with painting probes for all human chromosomes to determine which chromosomes had contributed material to the induced MN. MMC treatment induced an approximately 18-fold increase in MN and led to a significant increase in hypodiploidy and structural chromosome aberrations in metaphase preparations. Undercondensation of pericentromeric heterochromatin of chromosomes 9 and 1 occurred in 20-75% of metaphases and FISH disclosed an abundance of material from these chromosomes in induced MN (62-69% from chromosome 9 and 7-12% from chromosome 1). DES treatment of lymphocytes induced a seven-fold increase in MN frequency and four-fold increase in the frequency of numerical aberrations; structural aberrations were not significantly increased. FISH analysis showed that material from all chromosomes was present in DES-induced MN, with material from chromosome 1 present in 16% of MN and material from each other chromosomes being present in 2-10% of MN. Material from chromosomes 14, 19 and 21 was significantly more frequent material from chromosome Y significantly less frequent in DES-treated cells than in controls. The findings of the MMC studies indicate that the heterochromatin block of chromosome 9 is a specific target for MMC-induced undercondensation, which induces a preferential occurrence of chromosome 9 material in MN. DES, in contrast, does not trigger heterochromatin decondensation and fails to induce such a significant appearance of material of particular chromosomes in MN.

Convergent evolution of chicken Z and human X chromosomes by expansion and gene acquisition.

PubMed

Bellott, Daniel W; Skaletsky, Helen; Pyntikova, Tatyana; Mardis, Elaine R; Graves, Tina; Kremitzki, Colin; Brown, Laura G; Rozen, Steve; Warren, Wesley C; Wilson, Richard K; Page, David C

2010-07-29

In birds, as in mammals, one pair of chromosomes differs between the sexes. In birds, males are ZZ and females ZW. In mammals, males are XY and females XX. Like the mammalian XY pair, the avian ZW pair is believed to have evolved from autosomes, with most change occurring in the chromosomes found in only one sex--the W and Y chromosomes. By contrast, the sex chromosomes found in both sexes--the Z and X chromosomes--are assumed to have diverged little from their autosomal progenitors. Here we report findings that challenge this assumption for both the chicken Z chromosome and the human X chromosome. The chicken Z chromosome, which we sequenced essentially to completion, is less gene-dense than chicken autosomes but contains a massive tandem array containing hundreds of duplicated genes expressed in testes. A comprehensive comparison of the chicken Z chromosome with the finished sequence of the human X chromosome demonstrates that each evolved independently from different portions of the ancestral genome. Despite this independence, the chicken Z and human X chromosomes share features that distinguish them from autosomes: the acquisition and amplification of testis-expressed genes, and a low gene density resulting from an expansion of intergenic regions. These features were not present on the autosomes from which the Z and X chromosomes originated but were instead acquired during the evolution of Z and X as sex chromosomes. We conclude that the avian Z and mammalian X chromosomes followed convergent evolutionary trajectories, despite their evolving with opposite (female versus male) systems of heterogamety. More broadly, in birds and mammals, sex chromosome evolution involved not only gene loss in sex-specific chromosomes, but also marked expansion and gene acquisition in sex chromosomes common to males and females.

The Precarious Prokaryotic Chromosome

PubMed Central

2014-01-01

Evolutionary selection for optimal genome preservation, replication, and expression should yield similar chromosome organizations in any type of cells. And yet, the chromosome organization is surprisingly different between eukaryotes and prokaryotes. The nuclear versus cytoplasmic accommodation of genetic material accounts for the distinct eukaryotic and prokaryotic modes of genome evolution, but it falls short of explaining the differences in the chromosome organization. I propose that the two distinct ways to organize chromosomes are driven by the differences between the global-consecutive chromosome cycle of eukaryotes and the local-concurrent chromosome cycle of prokaryotes. Specifically, progressive chromosome segregation in prokaryotes demands a single duplicon per chromosome, while other “precarious” features of the prokaryotic chromosomes can be viewed as compensations for this severe restriction. PMID:24633873

Porphyromonas gingivalis Uses Specific Domain Rearrangements and Allelic Exchange to Generate Diversity in Surface Virulence Factors.

PubMed

Dashper, Stuart G; Mitchell, Helen L; Seers, Christine A; Gladman, Simon L; Seemann, Torsten; Bulach, Dieter M; Chandry, P Scott; Cross, Keith J; Cleal, Steven M; Reynolds, Eric C

2017-01-01

Porphyromonas gingivalis is a keystone pathogen of chronic periodontitis. The virulence of P. gingivalis is reported to be strain related and there are currently a number of strain typing schemes based on variation in capsular polysaccharide, the major and minor fimbriae and adhesin domains of Lys-gingipain (Kgp), amongst other surface proteins. P. gingivalis can exchange chromosomal DNA between strains by natural competence and conjugation. The aim of this study was to determine the genetic variability of P. gingivalis strains sourced from international locations over a 25-year period and to determine if variability in surface virulence factors has a phylogenetic basis. Whole genome sequencing was performed on 13 strains and comparison made to 10 previously sequenced strains. A single nucleotide polymorphism-based phylogenetic analysis demonstrated a shallow tri-lobed phylogeny. There was a high level of reticulation in the phylogenetic network, demonstrating extensive horizontal gene transfer between the strains. Two highly conserved variants of the catalytic domain of the major virulence factor the Kgp proteinase (Kgp cat I and Kgp cat II) were found. There were three variants of the fourth Kgp C-terminal cleaved adhesin domain. Specific variants of the cell surface proteins FimA, FimCDE, MfaI, RagAB, Tpr, and PrtT were also identified. The occurrence of all these variants in the P. gingivalis strains formed a mosaic that was not related to the SNP-based phylogeny. In conclusion P. gingivalis uses domain rearrangements and genetic exchange to generate diversity in specific surface virulence factors.

Extensive recombination events and horizontal gene transfer shaped the Legionella pneumophila genomes

PubMed Central

2011-01-01

Background Legionella pneumophila is an intracellular pathogen of environmental protozoa. When humans inhale contaminated aerosols this bacterium may cause a severe pneumonia called Legionnaires' disease. Despite the abundance of dozens of Legionella species in aquatic reservoirs, the vast majority of human disease is caused by a single serogroup (Sg) of a single species, namely L. pneumophila Sg1. To get further insights into genome dynamics and evolution of Sg1 strains, we sequenced strains Lorraine and HL 0604 1035 (Sg1) and compared them to the available sequences of Sg1 strains Paris, Lens, Corby and Philadelphia, resulting in a comprehensive multigenome analysis. Results We show that L. pneumophila Sg1 has a highly conserved and syntenic core genome that comprises the many eukaryotic like proteins and a conserved repertoire of over 200 Dot/Icm type IV secreted substrates. However, recombination events and horizontal gene transfer are frequent. In particular the analyses of the distribution of nucleotide polymorphisms suggests that large chromosomal fragments of over 200 kbs are exchanged between L. pneumophila strains and contribute to the genome dynamics in the natural population. The many secretion systems present might be implicated in exchange of these fragments by conjugal transfer. Plasmids also play a role in genome diversification and are exchanged among strains and circulate between different Legionella species. Conclusion Horizontal gene transfer among bacteria and from eukaryotes to L. pneumophila as well as recombination between strains allows different clones to evolve into predominant disease clones and others to replace them subsequently within relatively short periods of time. PMID:22044686

An increase in telomere sister chromatid exchange in murine embryonic stem cells possessing critically shortened telomeres

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

Wang, Yisong; Giannone, Richard J; Wu, Jun

Telomerase deficiency leads to a progressive loss of telomeric DNA that eventually triggers cell apoptosis in human primary cells during prolonged growth in culture. Rare survivors can maintain telomere length through either activation of telomerase or recombination-based telomere lengthening, and thus proliferate indefinitely. We have explored the possibility that telomeres may be maintained through telomere sister chromatid exchange (T-SCE) in murine telomere reverse transcriptase-deficient (mTert -/-) splenocytes and ES cells. Because telomerase deficiency leads to gradual loss of telomeric DNA in mTert -/- splenocytes and ES cells and eventually to chromosomes with telomere signal-free ends (SFEs), we examined these cellmore » types for evidence of sister chromatid exchange at telomeres, and observed an increase in T-SCEs only in a subset of mTert -/- splenocytes or ES cells that possessed multiple SFEs. Furthermore, T-SCEs were more often detected in ES cells than in splenocytes that harbored a similar frequency of SFEs. In mTert heterozygous (mTert +/-) ES cells or splenocytes, which are known to exhibit a decrease in average telomere length but no SFEs, no increase in T-SCE was observed. In addition to T-SCE, other genomic rearrangements (i.e., SCE) were also significantly increased in mTert -/- ES cells possessing critically short telomeres, but not in splenocytes. Our results suggest that animals and cell culture differ in their ability to carry out genomic rearrangements as a means of maintaining telomere integrity when telomeres become critically shortened.« less

Centromere inactivation on a neo-Y fusion chromosome in threespine stickleback fish

PubMed Central

Cech, Jennifer N.; Peichel, Catherine L.

2016-01-01

Having one and only one centromere per chromosome is essential for proper chromosome segregation during both mitosis and meiosis. Chromosomes containing two centromeres are known as dicentric and often mis-segregate during cell division, resulting in aneuploidy or chromosome breakage. Dicentric chromosome can be stabilized by centromere inactivation, a process which re-establishes monocentric chromosomes. However, little is known about this process in naturally occurring dicentric chromosomes. Using a combination of fluorescence in situ hybridization (FISH) and immunoflourescence combined with FISH (IF-FISH) on metaphase chromosome spreads, we demonstrate that centromere inactivation has evolved on a neo-Y chromosome fusion in the Japan Sea threespine stickleback fish (Gasterosteus nipponicus). We found that the centromere derived from the ancestral Y chromosome has been inactivated. Our data further suggest that there have been genetic changes to this centromere in the two million years since the formation of the neo-Y chromosome, but it remains unclear whether these genetic changes are a cause or consequence of centromere inactivation. PMID:27553478

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.

Lack of sex chromosome specific meiotic silencing in platypus reveals origin of MSCI in therian mammals.

PubMed

Daish, Tasman J; Casey, Aaron E; Grutzner, Frank

2015-12-10

In therian mammals heteromorphic sex chromosomes are subject to meiotic sex chromosome inactivation (MSCI) during meiotic prophase I while the autosomes maintain transcriptional activity. The evolution of this sex chromosome silencing is thought to result in retroposition of genes required in spermatogenesis from the sex chromosomes to autosomes. In birds sex chromosome specific silencing appears to be absent and global transcriptional reductions occur through pachytene and sex chromosome-derived autosomal retrogenes are lacking. Egg laying monotremes are the most basal mammalian lineage, feature a complex and highly differentiated XY sex chromosome system with homology to the avian sex chromosomes, and also lack autosomal retrogenes. In order to delineate the point of origin of sex chromosome specific silencing in mammals we investigated whether MSCI exists in platypus. Our results show that platypus sex chromosomes display only partial or transient colocalisation with a repressive histone variant linked to therian sex chromosome silencing and surprisingly lack a hallmark MSCI epigenetic signature present in other mammals. Remarkably, platypus instead feature an avian like period of general low level transcription through prophase I with the sex chromosomes and the future mammalian X maintaining association with a nucleolus-like structure. Our work demonstrates for the first time that in mammals meiotic silencing of sex chromosomes evolved after the divergence of monotremes presumably as a result of the differentiation of the therian XY sex chromosomes. We provide a novel evolutionary scenario on how the future therian X chromosome commenced the trajectory toward MSCI.

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.

Characterization of the genetic elements required for site-specific integration of plasmid pSE211 in Saccharopolyspora erythraea.

PubMed Central

Brown, D P; Idler, K B; Katz, L

1990-01-01

The 18.1-kilobase plasmid pSE211 integrates into the chromosome of Saccharopolyspora erythraea at a specific attB site. Restriction analysis of the integrated plasmid, pSE211int, and adjacent chromosomal sequences allowed identification of attP, the plasmid attachment site. Nucleotide sequencing of attP, attB, attL, and attR revealed a 57-base-pair sequence common to all sites with no duplications of adjacent plasmid or chromosomal sequences in the integrated state, indicating that integration takes place through conservative, reciprocal strand exchange. An analysis of the sequences indicated the presence of a putative gene for Phe-tRNA at attB which is preserved at attL after integration has occurred. A comparison of the attB site for a number of actinomycete plasmids is presented. Integration at attB was also observed when a 2.4-kilobase segment of pSE211 containing attP and the adjacent plasmid sequence was used to transform a pSE211- host. Nucleotide sequencing of this segment revealed the presence of two complete open reading frames (ORFs) and a segment of a third ORF. The ORF adjacent to attP encodes a putative polypeptide 437 amino acids in length that shows similarity, at its C-terminal domain, to sequences of site-specific recombinases of the integrase family. The adjacent ORF encodes a putative 98-amino-acid basic polypeptide that contains a helix-turn-helix motif at its N terminus which corresponds to domains in the Xis proteins of a number of bacteriophages. A proposal for the function of this polypeptide is presented. The deduced amino acid sequence of the third ORF did not reveal similarities to polypeptide sequences in the current data banks. Images FIG. 2 FIG. 3 PMID:2180909

Assessment of adaptability of zebu cattle ( Bos indicus) breeds in two different climatic conditions: using cytogenetic techniques on genome integrity

NASA Astrophysics Data System (ADS)

Kumar, Anil; Waiz, Syma Ashraf; Sridhar Goud, T.; Tonk, R. K.; Grewal, Anita; Singh, S. V.; Yadav, B. R.; Upadhyay, R. C.

2016-06-01

The aim of this study was to evaluate the genome integrity so as to assess the adaptability of three breeds of indigenous cattle reared under arid and semi-arid regions of Rajasthan (Bikaner) and Haryana (Karnal) India. The cattle were of homogenous group (same age and sex) of indigenous breeds viz. Sahiwal, Tharparkar and Kankrej. A total of 100 animals were selected for this study from both climatic conditions. The sister chromatid exchanges (SCE's), chromosomal gaps and chromatid breaks were observed in metaphase plates of chromosome preparations obtained from in vitro culture of peripheral blood lymphocytes. The mean number of breaks and gaps in Sahiwal and Tharparkar of semi-arid zone were 8.56 ± 3.16, 6.4 ± 3.39 and 8.72 ± 2.04, 3.52 ± 6.29, respectively. Similarly, the mean number of breaks and gaps in Tharparkar and Kankrej cattle of arid zone were 5.26 ± 1.76, 2.74 ± 1.76 and 5.24 ± 1.84, 2.5 ± 1.26, respectively. The frequency of SCEs in chromosomes was found significantly higher ( P < 0.05) in Tharparkar of semi-arid region (4.72 ± 1.55) compared to arid region (2.83 ± 1.01). Similarly, the frequency of SCEs was found to be 4.0 ± 1.41 in the Sahiwal of semi-arid region and 2.69 ± 1.12 in Kankrej of arid zone. Statistical analysis revealed significant differences ( P < 0.05) amongst the different zones, i.e. arid and semi-arid, whereas no significant difference ( P > 0.05) was observed in the same zone. The analysis of frequency of CAs and SCEs revealed significant effects of environmental conditions on the genome integrity of animals, thereby indicating an association with their adaptability.

Analysis and Toxicity of Plain (PMP) and Blended (PMT) Indian Pan Masala (PM).

PubMed

Nigam, Suresh Kumar; Venkatakrishna-Bhatt, H

2013-02-01

Betel leaf combined with areca nut is known as betel quid pan masala (PM), and tobacco with areca nut, catechu and lime is pan masala (PMT) blended with gulkhand. These narcotics are popular among young and old individuals. A prima facia chemical analysis and a toxicity assessment of PM in mice were conducted to study the relationship between longtime consumption of PM and health hazards. Chemical analysis of different types of PM was done employing HPLC, GLC, AAS, ES, TLC, GCMS and sequential extraction for PAH, pesticides, metals and minerals, electrolytes, drugs and xenobiotics. Ethanolic PM extracts were tested by IP and PO routes in inbred Swiss mice. PAH, which are known xenobiotics for pre-cancerous lesions, were significantly high (p<0.01) in Rajaniganda and Pan Parag Zarda. Isomers of DDT and BHC, which principally act on nerves and muscles, were also high (p<0.01) in PM. The enhanced metal and mineral content of PM results in massive oral fibrosis. There is a high level of narcotics in PM, especially nicotine, a potentially cancerous agent in the gastrointestinal tract. Experimental studies with different extracts of plain and blended PM in mice fed for 16 and 90 days revealed no effect on blood and organ weights (kidney, heart, spleen and liver), but we did observe attenuated testis. However, in the bone marrow of the mice, chromosomes were most affected in the mice fed PM-Zarda blend for 3 months. The chromosomal abnormalities included ploidy, loss, breaks, gaps, deletions and exchanges in ring chromosomes. The PM caused sperm head anomalies (narrow, blunt, triangular and banana shapes), and the sperm were irregular, amorphous, tailless and rudimentary, with the maximum effect among the groups fed PM for 3 months. Significantly higher levels (p<0.01) of testis glycogen, cholesterol and protein were found. The group fed for 16 days showed no change in red blood corpuscles (RBC), white blood corpuscles (WBC), hemoglobin and erythrocyte sedimentation counts.

X Chromosome Crossover Formation and Genome Stability in Caenorhabditis elegans Are Independently Regulated by xnd-1

PubMed Central

McClendon, T. Brooke; Mainpal, Rana; Amrit, Francis R. G.; Krause, Michael W.; Ghazi, Arjumand; Yanowitz, Judith L.

2016-01-01

The germ line efficiently combats numerous genotoxic insults to ensure the high fidelity propagation of unaltered genomic information across generations. Yet, germ cells in most metazoans also intentionally create double-strand breaks (DSBs) to promote DNA exchange between parental chromosomes, a process known as crossing over. Homologous recombination is employed in the repair of both genotoxic lesions and programmed DSBs, and many of the core DNA repair proteins function in both processes. In addition, DNA repair efficiency and crossover (CO) distribution are both influenced by local and global differences in chromatin structure, yet the interplay between chromatin structure, genome integrity, and meiotic fidelity is still poorly understood. We have used the xnd-1 mutant of Caenorhabditis elegans to explore the relationship between genome integrity and crossover formation. Known for its role in ensuring X chromosome CO formation and germ line development, we show that xnd-1 also regulates genome stability. xnd-1 mutants exhibited a mortal germ line, high embryonic lethality, high incidence of males, and sensitivity to ionizing radiation. We discovered that a hypomorphic allele of mys-1 suppressed these genome instability phenotypes of xnd-1, but did not suppress the CO defects, suggesting it serves as a separation-of-function allele. mys-1 encodes a histone acetyltransferase, whose homolog Tip60 acetylates H2AK5, a histone mark associated with transcriptional activation that is increased in xnd-1 mutant germ lines, raising the possibility that thresholds of H2AK5ac may differentially influence distinct germ line repair events. We also show that xnd-1 regulated him-5 transcriptionally, independently of mys-1, and that ectopic expression of him-5 suppressed the CO defects of xnd-1. Our work provides xnd-1 as a model in which to study the link between chromatin factors, gene expression, and genome stability. PMID:27678523

Assessment of adaptability of zebu cattle (Bos indicus) breeds in two different climatic conditions: using cytogenetic techniques on genome integrity.

PubMed

Kumar, Anil; Waiz, Syma Ashraf; Sridhar Goud, T; Tonk, R K; Grewal, Anita; Singh, S V; Yadav, B R; Upadhyay, R C

2016-06-01

The aim of this study was to evaluate the genome integrity so as to assess the adaptability of three breeds of indigenous cattle reared under arid and semi-arid regions of Rajasthan (Bikaner) and Haryana (Karnal) India. The cattle were of homogenous group (same age and sex) of indigenous breeds viz. Sahiwal, Tharparkar and Kankrej. A total of 100 animals were selected for this study from both climatic conditions. The sister chromatid exchanges (SCE's), chromosomal gaps and chromatid breaks were observed in metaphase plates of chromosome preparations obtained from in vitro culture of peripheral blood lymphocytes. The mean number of breaks and gaps in Sahiwal and Tharparkar of semi-arid zone were 8.56 ± 3.16, 6.4 ± 3.39 and 8.72 ± 2.04, 3.52 ± 6.29, respectively. Similarly, the mean number of breaks and gaps in Tharparkar and Kankrej cattle of arid zone were 5.26 ± 1.76, 2.74 ± 1.76 and 5.24 ± 1.84, 2.5 ± 1.26, respectively. The frequency of SCEs in chromosomes was found significantly higher (P < 0.05) in Tharparkar of semi-arid region (4.72 ± 1.55) compared to arid region (2.83 ± 1.01). Similarly, the frequency of SCEs was found to be 4.0 ± 1.41 in the Sahiwal of semi-arid region and 2.69 ± 1.12 in Kankrej of arid zone. Statistical analysis revealed significant differences (P < 0.05) amongst the different zones, i.e. arid and semi-arid, whereas no significant difference (P > 0.05) was observed in the same zone. The analysis of frequency of CAs and SCEs revealed significant effects of environmental conditions on the genome integrity of animals, thereby indicating an association with their adaptability.

Mps1 phosphorylation of condensin II controls chromosome condensation at the onset of mitosis.

PubMed

Kagami, Yuya; Nihira, Keishi; Wada, Shota; Ono, Masaya; Honda, Mariko; Yoshida, Kiyotsugu

2014-06-23

During mitosis, genomic DNA is condensed into chromosomes to promote its equal segregation into daughter cells. Chromosome condensation occurs during cell cycle progression from G2 phase to mitosis. Failure of chromosome compaction at prophase leads to subsequent misregulation of chromosomes. However, the molecular mechanism that controls the early phase of mitotic chromosome condensation is largely unknown. Here, we show that Mps1 regulates initial chromosome condensation during mitosis. We identify condensin II as a novel Mps1-associated protein. Mps1 phosphorylates one of the condensin II subunits, CAP-H2, at Ser492 during mitosis, and this phosphorylation event is required for the proper loading of condensin II on chromatin. Depletion of Mps1 inhibits chromosomal targeting of condensin II and accurate chromosome condensation during prophase. These findings demonstrate that Mps1 governs chromosomal organization during the early stage of mitosis to facilitate proper chromosome segregation. © 2014 Kagami et al.

Mps1 phosphorylation of condensin II controls chromosome condensation at the onset of mitosis

PubMed Central

Kagami, Yuya; Nihira, Keishi; Wada, Shota; Ono, Masaya; Honda, Mariko

2014-01-01

During mitosis, genomic DNA is condensed into chromosomes to promote its equal segregation into daughter cells. Chromosome condensation occurs during cell cycle progression from G2 phase to mitosis. Failure of chromosome compaction at prophase leads to subsequent misregulation of chromosomes. However, the molecular mechanism that controls the early phase of mitotic chromosome condensation is largely unknown. Here, we show that Mps1 regulates initial chromosome condensation during mitosis. We identify condensin II as a novel Mps1-associated protein. Mps1 phosphorylates one of the condensin II subunits, CAP-H2, at Ser492 during mitosis, and this phosphorylation event is required for the proper loading of condensin II on chromatin. Depletion of Mps1 inhibits chromosomal targeting of condensin II and accurate chromosome condensation during prophase. These findings demonstrate that Mps1 governs chromosomal organization during the early stage of mitosis to facilitate proper chromosome segregation. PMID:24934155

Fluorescence imaging of chromosomal DNA using click chemistry

NASA Astrophysics Data System (ADS)

Ishizuka, Takumi; Liu, Hong Shan; Ito, Kenichiro; Xu, Yan

2016-09-01

Chromosome visualization is essential for chromosome analysis and genetic diagnostics. Here, we developed a click chemistry approach for multicolor imaging of chromosomal DNA instead of the traditional dye method. We first demonstrated that the commercially available reagents allow for the multicolor staining of chromosomes. We then prepared two pro-fluorophore moieties that served as light-up reporters to stain chromosomal DNA based on click reaction and visualized the clear chromosomes in multicolor. We applied this strategy in fluorescence in situ hybridization (FISH) and identified, with high sensitivity and specificity, telomere DNA at the end of the chromosome. We further extended this approach to observe several basic stages of cell division. We found that the click reaction enables direct visualization of the chromosome behavior in cell division. These results suggest that the technique can be broadly used for imaging chromosomes and may serve as a new approach for chromosome analysis and genetic diagnostics.

Reversal of an ancient sex chromosome to an autosome in Drosophila.

PubMed

Vicoso, Beatriz; Bachtrog, Doris

2013-07-18

Although transitions of sex-determination mechanisms are frequent in species with homomorphic sex chromosomes, heteromorphic sex chromosomes are thought to represent a terminal evolutionary stage owing to chromosome-specific adaptations such as dosage compensation or an accumulation of sex-specific mutations. Here we show that an autosome of Drosophila, the dot chromosome, was ancestrally a differentiated X chromosome. We analyse the whole genome of true fruitflies (Tephritidae), flesh flies (Sarcophagidae) and soldier flies (Stratiomyidae) to show that genes located on the dot chromosome of Drosophila are X-linked in outgroup species, whereas Drosophila X-linked genes are autosomal. We date this chromosomal transition to early drosophilid evolution by sequencing the genome of other Drosophilidae. Our results reveal several puzzling aspects of Drosophila dot chromosome biology to be possible remnants of its former life as a sex chromosome, such as its minor feminizing role in sex determination or its targeting by a chromosome-specific regulatory mechanism. We also show that patterns of biased gene expression of the dot chromosome during early embryogenesis, oogenesis and spermatogenesis resemble that of the current X chromosome. Thus, although sex chromosomes are not necessarily evolutionary end points and can revert back to an autosomal inheritance, the highly specialized genome architecture of this former X chromosome suggests that severe fitness costs must be overcome for such a turnover to occur.

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.

Deciphering evolutionary strata on plant sex chromosomes and fungal mating-type chromosomes through compositional segmentation.

PubMed

Pandey, Ravi S; Azad, Rajeev K

2016-03-01

Sex chromosomes have evolved from a pair of homologous autosomes which differentiated into sex determination systems, such as XY or ZW system, as a consequence of successive recombination suppression between the gametologous chromosomes. Identifying the regions of recombination suppression, namely, the "evolutionary strata", is central to understanding the history and dynamics of sex chromosome evolution. Evolution of sex chromosomes as a consequence of serial recombination suppressions is well-studied for mammals and birds, but not for plants, although 48 dioecious plants have already been reported. Only two plants Silene latifolia and papaya have been studied until now for the presence of evolutionary strata on their X chromosomes, made possible by the sequencing of sex-linked genes on both the X and Y chromosomes, which is a requirement of all current methods that determine stratum structure based on the comparison of gametologous sex chromosomes. To circumvent this limitation and detect strata even if only the sequence of sex chromosome in the homogametic sex (i.e. X or Z chromosome) is available, we have developed an integrated segmentation and clustering method. In application to gene sequences on the papaya X chromosome and protein-coding sequences on the S. latifolia X chromosome, our method could decipher all known evolutionary strata, as reported by previous studies. Our method, after validating on known strata on the papaya and S. latifolia X chromosome, was applied to the chromosome 19 of Populus trichocarpa, an incipient sex chromosome, deciphering two, yet unknown, evolutionary strata. In addition, we applied this approach to the recently sequenced sex chromosome V of the brown alga Ectocarpus sp. that has a haploid sex determination system (UV system) recovering the sex determining and pseudoautosomal regions, and then to the mating-type chromosomes of an anther-smut fungus Microbotryum lychnidis-dioicae predicting five strata in the non-recombining region of both the chromosomes.

Highly conserved Z and molecularly diverged W chromosomes in the fish genus Triportheus (Characiformes, Triportheidae).

PubMed

Yano, C F; Bertollo, L A C; Ezaz, T; Trifonov, V; Sember, A; Liehr, T; Cioffi, M B

2017-03-01

The main objectives of this study were to test: (1) whether the W-chromosome differentiation matches to species' evolutionary divergence (phylogenetic concordance) and (2) whether sex chromosomes share a common ancestor within a congeneric group. The monophyletic genus Triportheus (Characiformes, Triportheidae) was the model group for this study. All species in this genus so far analyzed have ZW sex chromosome system, where the Z is always the largest chromosome of the karyotype, whereas the W chromosome is highly variable ranging from almost homomorphic to highly heteromorphic. We applied conventional and molecular cytogenetic approaches including C-banding, ribosomal DNA mapping, comparative genomic hybridization (CGH) and cross-species whole chromosome painting (WCP) to test our questions. We developed Z- and W-chromosome paints from T. auritus for cross-species WCP and performed CGH in a representative species (T. signatus) to decipher level of homologies and rates of differentiation of W chromosomes. Our study revealed that the ZW sex chromosome system had a common origin, showing highly conserved Z chromosomes and remarkably divergent W chromosomes. Notably, the W chromosomes have evolved to different shapes and sequence contents within ~15-25 Myr of divergence time. Such differentiation highlights a dynamic process of W-chromosome evolution within congeneric species of Triportheus.

Higher-order genome organization in platypus and chicken sperm and repositioning of sex chromosomes during mammalian evolution.

PubMed

Tsend-Ayush, Enkhjargal; Dodge, Natasha; Mohr, Julia; Casey, Aaron; Himmelbauer, Heinz; Kremitzki, Colin L; Schatzkamer, Kyriena; Graves, Tina; Warren, Wesley C; Grützner, Frank

2009-02-01

In mammals, chromosomes occupy defined positions in sperm, whereas previous work in chicken showed random chromosome distribution. Monotremes (platypus and echidnas) are the most basal group of living mammals. They have elongated sperm like chicken and a complex sex chromosome system with homology to chicken sex chromosomes. We used platypus and chicken genomic clones to investigate genome organization in sperm. In chicken sperm, about half of the chromosomes investigated are organized non-randomly, whereas in platypus chromosome organization in sperm is almost entirely non-random. The use of genomic clones allowed us to determine chromosome orientation and chromatin compaction in sperm. We found that in both species chromosomes maintain orientation of chromosomes in sperm independent of random or non-random positioning along the sperm nucleus. The distance of loci correlated with the total length of sperm nuclei, suggesting that chromatin extension depends on sperm elongation. In platypus, most sex chromosomes cluster in the posterior region of the sperm nucleus, presumably the result of postmeiotic association of sex chromosomes. Chicken and platypus autosomes sharing homology with the human X chromosome located centrally in both species suggesting that this is the ancestral position. This suggests that in some therian mammals a more anterior position of the X chromosome has evolved independently.

Higher-order genome organization in platypus and chicken sperm and repositioning of sex chromosomes during mammalian evolution

PubMed Central

Tsend-Ayush, Enkhjargal; Dodge, Natasha; Mohr, Julia; Casey, Aaron; Himmelbauer, Heinz; Kremitzki, Colin L.; Schatzkamer, Kyriena; Graves, Tina; Warren, Wesley C.

2013-01-01

In mammals, chromosomes occupy defined positions in sperm, whereas previous work in chicken showed random chromosome distribution. Monotremes (platypus and echidnas) are the most basal group of living mammals. They have elongated sperm like chicken and a complex sex chromosome system with homology to chicken sex chromosomes. We used platypus and chicken genomic clones to investigate genome organization in sperm. In chicken sperm, about half of the chromosomes investigated are organized non-randomly, whereas in platypus chromosome organization in sperm is almost entirely non-random. The use of genomic clones allowed us to determine chromosome orientation and chromatin compaction in sperm. We found that in both species chromosomes maintain orientation of chromosomes in sperm independent of random or non-random positioning along the sperm nucleus. The distance of loci correlated with the total length of sperm nuclei, suggesting that chromatin extension depends on sperm elongation. In platypus, most sex chromosomes cluster in the posterior region of the sperm nucleus, presumably the result of postmeiotic association of sex chromosomes. Chicken and platypus autosomes sharing homology with the human X chromosome located centrally in both species suggesting that this is the ancestral position. This suggests that in some therian mammals a more anterior position of the X chromosome has evolved independently. PMID:18726609

The Multipartite Mitochondrial Genome of Liposcelis bostrychophila: Insights into the Evolution of Mitochondrial Genomes in Bilateral Animals

PubMed Central

Yuan, Ming-Long; Dou, Wei; Barker, Stephen C.; Wang, Jin-Jun

2012-01-01

Booklice (order Psocoptera) in the genus Liposcelis are major pests to stored grains worldwide and are closely related to parasitic lice (order Phthiraptera). We sequenced the mitochondrial (mt) genome of Liposcelis bostrychophila and found that the typical single mt chromosome of bilateral animals has fragmented into and been replaced by two medium-sized chromosomes in this booklouse; each of these chromosomes has about half of the genes of the typical mt chromosome of bilateral animals. These mt chromosomes are 8,530 bp (mt chromosome I) and 7,933 bp (mt chromosome II) in size. Intriguingly, mt chromosome I is twice as abundant as chromosome II. It appears that the selection pressure for compact mt genomes in bilateral animals favors small mt chromosomes when small mt chromosomes co-exist with the typical large mt chromosomes. Thus, small mt chromosomes may have selective advantages over large mt chromosomes in bilateral animals. Phylogenetic analyses of mt genome sequences of Psocodea (i.e. Psocoptera plus Phthiraptera) indicate that: 1) the order Psocoptera (booklice and barklice) is paraphyletic; and 2) the order Phthiraptera (the parasitic lice) is monophyletic. Within parasitic lice, however, the suborder Ischnocera is paraphyletic; this differs from the traditional view that each suborder of parasitic lice is monophyletic. PMID:22479490

MECHANISMS IN ENDOCRINOLOGY: Aberrations of the X chromosome as cause of male infertility.

PubMed

Röpke, Albrecht; Tüttelmann, Frank

2017-11-01

Male infertility is most commonly caused by spermatogenetic failure, clinically noted as oligo- or a-zoospermia. Today, in approximately 20% of azoospermic patients, a causal genetic defect can be identified. The most frequent genetic causes of azoospermia (or severe oligozoospermia) are Klinefelter syndrome (47,XXY), structural chromosomal abnormalities and Y-chromosomal microdeletions. Consistent with Ohno's law, the human X chromosome is the most stable of all the chromosomes, but contrary to Ohno's law, the X chromosome is loaded with regions of acquired, rapidly evolving genes, which are of special interest because they are predominantly expressed in the testis. Therefore, it is not surprising that the X chromosome, considered as the female counterpart of the male-associated Y chromosome, may actually play an essential role in male infertility and sperm production. This is supported by the recent description of a significantly increased copy number variation (CNV) burden on both sex chromosomes in infertile men and point mutations in X-chromosomal genes responsible for male infertility. Thus, the X chromosome seems to be frequently affected in infertile male patients. Four principal X-chromosomal aberrations have been identified so far: (1) aneuploidy of the X chromosome as found in Klinefelter syndrome (47,XXY or mosaicism for additional X chromosomes). (2) Translocations involving the X chromosome, e.g. nonsyndromic 46,XX testicular disorders of sex development (XX-male syndrome) or X-autosome translocations. (3) CNVs affecting the X chromosome. (4) Point mutations disrupting X-chromosomal genes. All these are reviewed herein and assessed concerning their importance for the clinical routine diagnostic workup of the infertile male as well as their potential to shape research on spermatogenic failure in the next years. © 2017 European Society of Endocrinology.

Risk of Gonadoblastoma Development in Patients with Turner Syndrome with Cryptic Y Chromosome Material.

PubMed

Kwon, Ahreum; Hyun, Sei Eun; Jung, Mo Kyung; Chae, Hyun Wook; Lee, Woo Jung; Kim, Tae Hyuk; Kim, Duk Hee; Kim, Ho-Seong

2017-06-01

Current guidelines recommend that testing for Y chromosome material should be performed only in patients with Turner syndrome harboring a marker chromosome and exhibiting virilization in order to detect individuals who are at high risk of gonadoblastoma. However, cryptic Y chromosome material is suggested to be a risk factor for gonadoblastoma in patients with Turner syndrome. Here, we aimed to estimate the frequency of cryptic Y chromosome material in patients with Turner syndrome and determine whether Y chromosome material increased the risk for development of gonadoblastoma. A total of 124 patients who were diagnosed with Turner syndrome by conventional cytogenetic techniques underwent additional molecular analysis to detect cryptic Y chromosome material. In addition, patients with Turner syndrome harboring Y chromosome cell lines had their ovaries removed prophylactically. Finally, we assessed the occurrence of gonadoblastoma in patients with Turner syndrome. Molecular analysis demonstrated that 10 patients had Y chromosome material among 118 patients without overt Y chromosome (8.5%). Six patients with overt Y chromosome and four patients with cryptic Y chromosome material underwent oophorectomy. Histopathological analysis revealed that the occurrence of gonadoblastoma in the total group was 2.4%, and gonadoblastoma occurred in one of six patients with an overt Y chromosome (16.7%) and 2 of 10 patients with cryptic Y chromosome material (20.0%). The risk of developing gonadoblastoma in patients with cryptic Y chromosome material was similar to that in patients with overt Y chromosome. Therefore, molecular screening for Y chromosome material should be recommended for all patients with Turner syndrome to detect individuals at a high risk of gonadoblastoma and to facilitate proper management of the disease.

Updating the maize karyotype by chromosome DNA sizing.

PubMed

Silva, Jéssica Coutinho; Carvalho, Carlos Roberto; Clarindo, Wellington Ronildo

2018-01-01

The karyotype is a basic concept regarding the genome, fundamentally described by the number and morphological features of all chromosomes. Chromosome class, centromeric index, intra- and interchromosomal asymmetry index, and constriction localization are important in clinical, systematic and evolutionary approaches. In spite of the advances in karyotype characterization made over the last years, new data about the chromosomes can be generated from quantitative methods, such as image cytometry. Therefore, using Zea mays L., this study aimed to update the species' karyotype by supplementing information on chromosome DNA sizing. After adjustment of the procedures, chromosome morphometry and class as well as knob localization enabled describing the Z. mays karyotype. In addition, applying image cytometry, DNA sizing was unprecedentedly measured for the arms and satellite of all chromosomes. This way, unambiguous identification of the chromosome pairs, and hence the assembly of 51 karyograms, were only possible after the DNA sizing of each chromosome, their arms and satellite portions. These accurate, quantitative and reproducible data also enabled determining the distribution and variation of DNA content in each chromosome. From this, a correlation between DNA amount and total chromosome length evidenced that the mean DNA content of chromosome 9 was higher than that of chromosome 8. The chromosomal DNA sizing updated the Z. mays karyotype, providing insights into its dynamic genome with regards to the organization of the ten chromosomes and their respective portions. Considering the results and the relevance of cytogenetics in the current scenario of comparative sequencing and genomics, chromosomal DNA sizing should be incorporated as an additional parameter for karyotype definition. Based on this study, it can be affirmed that cytogenetic approaches go beyond the simple morphological description of chromosomes.

Karyological characterization of the endemic Iberian rock lizard, Iberolacerta monticola (Squamata, Lacertidae): insights into sex chromosome evolution.

PubMed

Rojo, V; Giovannotti, M; Naveira, H; Nisi Cerioni, P; González-Tizón, A M; Caputo Barucchi, V; Galán, P; Olmo, E; Martínez-Lage, A

2014-01-01

Rock lizards of the genus Iberolacerta constitute a promising model to examine the process of sex chromosome evolution, as these closely related taxa exhibit remarkable diversity in the degree of sex chromosome differentiation with no clear phylogenetic segregation, ranging from cryptic to highly heteromorphic ZW chromosomes and even multiple chromosome systems (Z1Z1Z2Z2/Z1Z2W). To gain a deeper insight into the patterns of karyotype and sex chromosome evolution, we performed a cytogenetic analysis based on conventional staining, banding techniques and fluorescence in situ hybridization in the species I. monticola, for which previous cytogenetic investigations did not detect differentiated sex chromosomes. The karyotype is composed of 2n = 36 acrocentric chromosomes. NORs and the major ribosomal genes were located in the subtelomeric region of chromosome pair 6. Hybridization signals of the telomeric sequences (TTAGGG)n were visualized at the telomeres of all chromosomes and interstitially in 5 chromosome pairs. C-banding showed constitutive heterochromatin at the centromeres of all chromosomes, as well as clear pericentromeric and light telomeric C-bands in several chromosome pairs. These results highlight some chromosomal markers which can be useful to identify species-specific diagnostic characters, although they may not accurately reflect the phylogenetic relationships among the taxa. In addition, C-banding revealed the presence of a heteromorphic ZW sex chromosome pair, where W is smaller than Z and almost completely heterochromatic. This finding sheds light on sex chromosome evolution in the genus Iberolacerta and suggests that further comparative cytogenetic analyses are needed to understand the processes underlying the origin, differentiation and plasticity of sex chromosome systems in lacertid lizards. © 2013 S. Karger AG, Basel.

Updating the maize karyotype by chromosome DNA sizing

PubMed Central

2018-01-01

The karyotype is a basic concept regarding the genome, fundamentally described by the number and morphological features of all chromosomes. Chromosome class, centromeric index, intra- and interchromosomal asymmetry index, and constriction localization are important in clinical, systematic and evolutionary approaches. In spite of the advances in karyotype characterization made over the last years, new data about the chromosomes can be generated from quantitative methods, such as image cytometry. Therefore, using Zea mays L., this study aimed to update the species’ karyotype by supplementing information on chromosome DNA sizing. After adjustment of the procedures, chromosome morphometry and class as well as knob localization enabled describing the Z. mays karyotype. In addition, applying image cytometry, DNA sizing was unprecedentedly measured for the arms and satellite of all chromosomes. This way, unambiguous identification of the chromosome pairs, and hence the assembly of 51 karyograms, were only possible after the DNA sizing of each chromosome, their arms and satellite portions. These accurate, quantitative and reproducible data also enabled determining the distribution and variation of DNA content in each chromosome. From this, a correlation between DNA amount and total chromosome length evidenced that the mean DNA content of chromosome 9 was higher than that of chromosome 8. The chromosomal DNA sizing updated the Z. mays karyotype, providing insights into its dynamic genome with regards to the organization of the ten chromosomes and their respective portions. Considering the results and the relevance of cytogenetics in the current scenario of comparative sequencing and genomics, chromosomal DNA sizing should be incorporated as an additional parameter for karyotype definition. Based on this study, it can be affirmed that cytogenetic approaches go beyond the simple morphological description of chromosomes. PMID:29293613

The architecture of chicken chromosome territories changes during differentiation

PubMed Central

Stadler, Sonja; Schnapp, Verena; Mayer, Robert; Stein, Stefan; Cremer, Christoph; Bonifer, Constanze; Cremer, Thomas; Dietzel, Steffen

2004-01-01

Background Between cell divisions the chromatin fiber of each chromosome is restricted to a subvolume of the interphase cell nucleus called chromosome territory. The internal organization of these chromosome territories is still largely unknown. Results We compared the large-scale chromatin structure of chromosome territories between several hematopoietic chicken cell types at various differentiation stages. Chromosome territories were labeled by fluorescence in situ hybridization in structurally preserved nuclei, recorded by confocal microscopy and evaluated visually and by quantitative image analysis. Chromosome territories in multipotent myeloid precursor cells appeared homogeneously stained and compact. The inactive lysozyme gene as well as the centromere of the lysozyme gene harboring chromosome located to the interior of the chromosome territory. In further differentiated cell types such as myeloblasts, macrophages and erythroblasts chromosome territories appeared increasingly diffuse, disaggregating to separable substructures. The lysozyme gene, which is gradually activated during the differentiation to activated macrophages, as well as the centromere were relocated increasingly to more external positions. Conclusions Our results reveal a cell type specific constitution of chromosome territories. The data suggest that a repositioning of chromosomal loci during differentiation may be a consequence of general changes in chromosome territory morphology, not necessarily related to transcriptional changes. PMID:15555075

Molecular and cytogenetic characterization of a chinese hamster/human hybrid cell line containing a der (21)t(Ypter [yields] cenY::cen21 [yields] 21qter) chromosome

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

Patterson, D.; Hart, I.; Jones, C.

1993-01-01

Human/rodent somatic cell hybrids have been exceedingly useful in assigning human genes and DNA sequences to specific human chromosomes. As new technologies for analyzing the human chromosome complement of such human/rodent hybrid cells become available, it is of critical importance that these be applied to enhance characterization of existing hybrids. This is particularly important since human chromosomes in such hybrids have been observed to rearrange with time. We report here the use of fluorescence in situ hybridization of DNA probes to metaphase chromosomes to analyze one hybrid designated 72532X6. This analysis shows that the chromosome suspected to be a normalmore » human chromosome 21 in this hybrid is actually a translocation chromosome containing Yp and 21 q. In addition, the hybrid contains a fragment of human chromosome 9 translocated to a Chinese hamster chromosome. Analysis of the chromosomes from the human donor indicates that his chromosomes are normal. Thus, this translocation chromosome appears to have arisen after formation of the hybrid. 14 refs., 2 figs.« less

Y-chromosome evolution: emerging insights into processes of Y-chromosome degeneration.

PubMed

Bachtrog, Doris

2013-02-01

The human Y chromosome is intriguing not only because it harbours the master-switch gene that determines gender but also because of its unusual evolutionary history. The Y chromosome evolved from an autosome, and its evolution has been characterized by massive gene decay. Recent whole-genome and transcriptome analyses of Y chromosomes in humans and other primates, in Drosophila species and in plants have shed light on the current gene content of the Y chromosome, its origins and its long-term fate. Furthermore, comparative analysis of young and old Y chromosomes has given further insights into the evolutionary and molecular forces triggering Y-chromosome degeneration and into the evolutionary destiny of the Y chromosome.

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.

Chromosome Connections: Compelling Clues to Common Ancestry

ERIC Educational Resources Information Center

Flammer, Larry

2013-01-01

Students compare banding patterns on hominid chromosomes and see striking evidence of their common ancestry. To test this, human chromosome no. 2 is matched with two shorter chimpanzee chromosomes, leading to the hypothesis that human chromosome 2 resulted from the fusion of the two shorter chromosomes. Students test that hypothesis by looking for…

[Analysis of chromosome composition in interspecific embryonic stem hybrid cells of mice].

PubMed

Pristiazhniuk, I E; Matveeva, N M; Grafodatskiĭ, A S; Serdiukova, N A; Serov, O L

2010-01-01

Chromosome complements of twenty hybrid clones obtained by fusion of Mus musculus embryonic stem cells (ESC) and M. caroli splenocytes were studied. Using of double-color in situ hybridization with chromosome- and species-specific probes we were able to detect the parental origin for each chromosome in hybrid cells. Based on parental chromosome ratio, all 20 hybrid clones were separated in some different groups: from the group containing practically tetraploid M. musculus genome with single M. caroli chromosomes to hybrids with dominance of M. caroli chromosome homologues. In 8 hybrid cells clones we observed prevalence of chromosomes originated from ESC in ratio from 5:1 to 3:1. Another hybrid cells clones have either equal (1:1, 1:2) ratio of M. musculus to M. caroli chromosomes or with the prevalence of ESC- (2:1) or splenocyte- (1:2) originated parental chromosome homologues. In 3 hybrid cells clones, we observed preferable segregation of ESC-originated pluripotent chromosomes. This phenomenon was found for the first time and it possibly indicates compensation of the epigenetic differences between parental chromosomes of ESC- and splenocyte-origination.

Intranuclear DNA density affects chromosome condensation in metazoans

PubMed Central

Hara, Yuki; Iwabuchi, Mari; Ohsumi, Keita; Kimura, Akatsuki

2013-01-01

Chromosome condensation is critical for accurate inheritance of genetic information. The degree of condensation, which is reflected in the size of the condensed chromosomes during mitosis, is not constant. It is differentially regulated in embryonic and somatic cells. In addition to the developmentally programmed regulation of chromosome condensation, there may be adaptive regulation based on spatial parameters such as genomic length or cell size. We propose that chromosome condensation is affected by a spatial parameter called the chromosome amount per nuclear space, or “intranuclear DNA density.” Using Caenorhabditis elegans embryos, we show that condensed chromosome sizes vary during early embryogenesis. Of importance, changing DNA content to haploid or polyploid changes the condensed chromosome size, even at the same developmental stage. Condensed chromosome size correlates with interphase nuclear size. Finally, a reduction in nuclear size in a cell-free system from Xenopus laevis eggs resulted in reduced condensed chromosome sizes. These data support the hypothesis that intranuclear DNA density regulates chromosome condensation. This suggests an adaptive mode of chromosome condensation regulation in metazoans. PMID:23783035

Origin of B chromosomes in Characidium alipioi (Characiformes, Crenuchidae) and its relationship with supernumerary chromosomes in other Characidium species.

PubMed

Serrano, Érica Alves; Utsunomia, Ricardo; Scudeller, Patrícia Sobrinho; Oliveira, Claudio; Foresti, Fausto

2017-01-01

B chromosomes are apparently dispensable components found in the genomes of many species that are mainly composed of repetitive DNA sequences. Among the numerous questions concerning B chromosomes, the origin of these elements has been widely studied. To date, supernumerary chromosomes have been identified in approximately 60 species of fish, including species of the genus Characidium Reinhardt, 1867 in which these elements appear to have independently originated. In this study, we used molecular cytogenetic techniques to investigate the origin of B chromosomes in a population of Characidium alipioi Travassos, 1955 and determine their relationship with the extra chromosomes of other species of the genus. The results showed that the B chromosomes of Characidium alipioi had an intraspecific origin, apparently originated independently in relation to the B chromosomes of Characidium gomesi Travassos, 1956 Characidium pterostictum Gomes, 1947 and Characidium oiticicai Travassos, 1967, since they do not share specific DNA sequences, as well as their possible ancestral chromosomes and belong to different phylogenetic clades. The shared sequences between the supernumerary chromosomes and the autosommal sm pair indicate the origin of these chromosomes.

Analysis of SINE and LINE repeat content of Y chromosomes in the platypus, Ornithorhynchus anatinus.

PubMed

Kortschak, R Daniel; Tsend-Ayush, Enkhjargal; Grützner, Frank

2009-01-01

Monotremes feature an extraordinary sex-chromosome system that consists of five X and five Y chromosomes in males. These sex chromosomes share homology with bird sex chromosomes but no homology with the therian X. The genome of a female platypus was recently completed, providing unique insights into sequence and gene content of autosomes and X chromosomes, but no Y-specific sequence has so far been analysed. Here we report the isolation, sequencing and analysis of approximately 700 kb of sequence of the non-recombining regions of Y2, Y3 and Y5, which revealed differences in base composition and repeat content between autosomes and sex chromosomes, and within the sex chromosomes themselves. This provides the first insights into repeat content of Y chromosomes in platypus, which overall show similar patterns of repeat composition to Y chromosomes in other species. Interestingly, we also observed differences between the various Y chromosomes, and in combination with timing and activity patterns we provide an approach that can be used to examine the evolutionary history of the platypus sex-chromosome chain.

[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.

Introduction of new genetic markers on human chromosomes

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

Satoh, Hitoshi; Barrett, J.C.; Oshimura, Mitsuo

1991-03-01

The purpose of this study was to use DNA transfection and microcell chromosome transfer techniques to engineer a human chromosome containing multiple biochemical markers for which selectable growth conditions exist. The starting chromosome was a t(X;3)(3pter{yields}3p12::Xq26{yields}Xpter) chromosome from a reciprocal translocation in the normal human fibroblast cell line GM0439. This chromosome was transferred to a HPRT (hypoxanthine phosphoribosyltransferase)-deficient mouse A9 cell line by microcell fusion and selected under growth conditions for the HPRT gene on the human t(X;3) chromosome. A resultant HAT-resistant cell line (A9(GM0439)-1) contained a single human t(X;3) chromosome. These results demonstrate that microcell chromosome transfer can bemore » used to select chromosomes containing multiple markers.« less

Behavior of Aberrant Chromosome Configurations in Drosophila melanogaster Female Meiosis I

PubMed Central

Gilliland, William D.; Colwell, Eileen M.; Lane, Fiona M.; Snouffer, Ashley A.

2014-01-01

One essential role of the first meiotic division is to reduce chromosome number by half. Although this is normally accomplished by segregating homologous chromosomes from each other, it is possible for a genome to have one or more chromosomes that lack a homolog (such as compound chromosomes), or have chromosomes with multiple potential homologs (such as in XXY females). These configurations complete meiosis but engage in unusual segregation patterns. In Drosophila melanogaster females carrying two compound chromosomes, the compounds can accurately segregate from each other, a process known as heterologous segregation. Similarly, in XXY females, when the X chromosomes fail to cross over, they often undergo secondary nondisjunction, where both Xs segregate away from the Y. Although both of these processes have been known for decades, the orientation mechanisms involved are poorly understood. Taking advantage of the recent discovery of chromosome congression in female meiosis I, we have examined a number of different aberrant chromosome configurations. We show that these genotypes complete congression normally, with their chromosomes bioriented at metaphase I arrest at the same rates that they segregate, indicating that orientation must be established during prometaphase I before congression. We also show that monovalent chromosomes can move out on the prometaphase I spindle, but the dot 4 chromosomes appear required for this movement. Finally, we show that, similar to achiasmate chromosomes, heterologous chromosomes can be connected by chromatin threads, suggesting a mechanism for how heterochromatic homology establishes these unusual biorientation patterns. PMID:25491942

Behavior of aberrant chromosome configurations in Drosophila melanogaster female meiosis I.

PubMed

Gilliland, William D; Colwell, Eileen M; Lane, Fiona M; Snouffer, Ashley A

2014-12-09

One essential role of the first meiotic division is to reduce chromosome number by half. Although this is normally accomplished by segregating homologous chromosomes from each other, it is possible for a genome to have one or more chromosomes that lack a homolog (such as compound chromosomes), or have chromosomes with multiple potential homologs (such as in XXY females). These configurations complete meiosis but engage in unusual segregation patterns. In Drosophila melanogaster females carrying two compound chromosomes, the compounds can accurately segregate from each other, a process known as heterologous segregation. Similarly, in XXY females, when the X chromosomes fail to cross over, they often undergo secondary nondisjunction, where both Xs segregate away from the Y. Although both of these processes have been known for decades, the orientation mechanisms involved are poorly understood. Taking advantage of the recent discovery of chromosome congression in female meiosis I, we have examined a number of different aberrant chromosome configurations. We show that these genotypes complete congression normally, with their chromosomes bioriented at metaphase I arrest at the same rates that they segregate, indicating that orientation must be established during prometaphase I before congression. We also show that monovalent chromosomes can move out on the prometaphase I spindle, but the dot 4 chromosomes appear required for this movement. Finally, we show that, similar to achiasmate chromosomes, heterologous chromosomes can be connected by chromatin threads, suggesting a mechanism for how heterochromatic homology establishes these unusual biorientation patterns. Copyright © 2015 Gilliland et al.

Comparison of spontaneous and idoxuridine-induced micronuclei by chromosome painting.

PubMed

Fauth, E; Zankl, H

1999-04-06

Fluorescence in situ hybridisation (FISH) technique with chromosome specific library (CSL) DNA probes for all human chromosomes were used to study about 9000 micronuclei (MN) in normal and idoxuridine (IUdR)-treated lymphocyte cultures of female and male donors. In addition, MN rates and structural chromosome aberrations were scored in Giemsa-stained chromosome spreads of these cultures. IUdR treatment (40 microg/ml) induced on the average a 12-fold increase of the MN rate. Metaphase analysis revealed no distinct increase of chromosome breaks but a preferential decondensation at chromosome 9q12 (28-79%) and to a lower extend at 1q12 (8-21%). Application of FISH technique with CSL probes to one male and one female untreated proband showed that all human chromosomes except chromosome 12 (and to a striking high frequency chromosomes 9, X and Y) occurred in spontaneous MN. In cultures containing IUdR, the chromosomal spectrum found in MN was reduced to 10 chromosomes in the male and 13 in the female proband. Eight chromosomes (2, 6, 12, 13, 14, 15, 17 and 18) did not occur in MN of both probands. On the contrary chromosomes 1 and especially 9 were found much more frequently in the MN of IUdR-treated cultures than in MN of control cultures. DAPI-staining revealed heterochromatin signals in most of the IUdR-induced MN. In an additional study, spontaneous and IUdR-induced MN were investigated in lymphocytes of another female donor using CSL probes only for chromosomes 1, 6, 9, 15, 16 and X. The results confirmed the previous finding that chromosomes 1 and 9 occur very often in MN after IUdR-treatment. The results indicate that decondensation of heterochromatic regions on chromosomes 1 and 9 caused by IUdR treatment strongly correlates with MN formation by these chromosomes. Copyright 1999 Elsevier Science B.V.

Detection of {open_quotes}cryptic{close_quotes}karyotypic rearrangements in closely related primate species by fluorescence in situ hybridization (FISH) using human subtelomeric DNA probes

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

Youngblom, J.J.; Trask, B.J.; Friedman, C.

Specific human subtelomeric DNA probes were used to reveal cryptic chromosomal rearrangements that cannot be detected by conventional high resolution cytogenetic techniques, or by chromosomal in situ suppression hybridization using whole chromosome paint analysis. Two cosmids containing different subtelomeric DNA sequences were derived from human chromosome 19 and designated as 7501 and 16432. Cosmid 7501 was hybridized to chromosomes from humans, chimpanzee, gorilla and orangutan. In humans, 7501 consistently labeled chromosomes 3q, 15q, and 19p. Additional chromosomes were labeled in different individuals, indicating a polymorphic distribution of this sequence in the human genome. In contrast, 7501 consistently and strongly labeledmore » only the q arm terminus of chromosome 3 in both chimp and gorilla. The identification of the chromosome was made by two-color FISH analysis using human chromosome 4-specific paint and homologous to human chromosome 4. None of the human subjects showed labeling of chromosome 4 with 7501. This finding suggests that in the course of human evolution, subsequent to the divergence of humans and African apes, a cryptic translocation occurred between the ancestral human chromosome 4 and one or more of the other human chromosomes that now contain this DNA segment. In orangutan, 7501 labeled a single acrocentric chromosome pair, a distinctly different chromosome than that labeled in chimp and gorilla. Comparison of chromosome sites labeled with cosmid 16432 showed the distribution of signals on chromosome 1q arm is the same for humans and chimp, but different in the gorilla. Humans and chimps show distinct labeling on sites 1q terminus and 1q41-42. In gorilla, there is instead a large cluster of intense signal near the terminus of 1q that clearly does not extend all the way to the terminus. A paracentric inversion or an unequal cross-over event may account for the observed difference between these species.« less

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.

Assessment of aneuploidy in human oocytes and preimplantation embryos by chromosome painting

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

Rougier, N.; Viegas-Pequignot, E.; Plachot, M.

1994-09-01

The poor quality of chromosome preparations often observed after fixation of oocytes and embryos did not usually allow accurate identification of chromosomes involved in non-disjunctions. We, therefore, used chromosome painting to determine the incidence of abnormalities for chromosomes 1 and 7. A total of 50 oocytes inseminated for IVF and showing no signs of fertilization as well as 37 diploid embryos donated for research were fixed according to the Dyban`s technique. Fluorescence in situ hybridization was carried out using whole chromosome painting DNA probes specific for human chromosome 1 and 7. The incidence of aneuploidy was 28%, 10% and 60%more » for metaphase II, polar body and sperm chromosomes, respectively. The high incidence of aneuploidy observed in sperm prematurely condensed sperm chromosomes is due to the fact that usually far less than 23 sperm chromatids are observed, maybe as a consequence of incomplete chromosome condensation. Thirty seven embryos were analyzed with the same probes. 48% of early embryos were either monosomic 1 or 7 or mosaics comprising blastomeres with 1, 2 or 3 signals. Thus, 8 among the 11 abnormal embryos had hypodiploid cells (25 to 37 chromosomes) indicating either an artefactual loss of chromosomes or a complex anomaly of nuclear division (maltinucleated blastomeres, abnormal migration of chromosomes at anaphase). We therefore calculated a {open_quotes}corrected{close_quotes} incidence of aneuploidy for chromosomes 1 or 7 in early embryos: 18%. 86% of the blastocysts showed mosaicism 2n/3 or 4n as a consequence of the formation of the syncitiotrophoblast. To conclude, chromosome painting is an efficient method to accurately identify chromosomes involved in aneuploidy. This technique should allow us to evaluate the incidence of non-disjunction for all chromosome pairs. Our results confirm the high incidence of chromosome abnormalities occurring as a consequence of meiotic or mitotic non-disjunctions in human oocytes and embryos.« less

Numerically abnormal chromosome constitutions in humans

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

NONE

1993-12-31

Chapter 24, discusses numerically abnormal chromosome constitutions in humans. This involves abnormalities of human chromosome number, including polyploidy (when the number of sets of chromosomes increases) and aneuploidy (when the number of individual normal chromosomes changes). Chapter sections discuss the following chromosomal abnormalities: human triploids, imprinting and uniparental disomy, human tetraploids, hydatidiform moles, anomalies caused by chromosomal imbalance, 13 trisomy (D{sub 1} trisomy, Patau syndrome), 21 trisomy (Down syndrome), 18 trisomy syndrome (Edwards syndrome), other autosomal aneuploidy syndromes, and spontaneous abortions. The chapter concludes with remarks on the nonrandom participation of chromosomes in trisomy. 69 refs., 3 figs., 4 tabs.

Titanium Dioxide Nanoparticles are not Cytotoxic or Clastogenic in Human Skin Cells

PubMed Central

Browning, Cynthia L; The, Therry; Mason, Michael D; Wise, John Pierce

2015-01-01

The application of nanoparticle technology is rapidly expanding. The reduced dimensionality of nanoparticles can give rise to changes in chemical and physical properties, often resulting in altered toxicity. People are exposed dermally to titanium dioxide (TiO2) nanoparticles in industrial and residential settings. The general public is increasingly exposed to these nanoparticles as their use in cosmetics, sunscreens and lotions expands. The toxicity of TiO2 nanoparticles towards human skin cells is unclear and understudied. We used a human skin fibroblast cell line to investigate the cytotoxicity and clastogenicity of TiO2 nanoparticles after 24 h exposure. In a clonogenic survival assay, treatments of 10, 50 and 100 μg/cm2 induced 97.8, 88.8 and 84.7% relative survival, respectively. Clastogenicity was assessed using a chromosomal aberration assay in order to determine whether TiO2 nanoparticles induced serious forms of DNA damage such as chromatid breaks, isochromatid lesions or chromatid exchanges. Treatments of 0, 10, 50 and 100 μg/cm2 induced 3.3, 3.0, 3.0 and 2.7% metaphases with damage, respectively. No isochromatid lesions or chromatid exchanges were detected. These data show that TiO2 nanoparticles are not cytotoxic or clastogenic to human skin cells. PMID:26568896

Titanium Dioxide Nanoparticles are not Cytotoxic or Clastogenic in Human Skin Cells.

PubMed

Browning, Cynthia L; The, Therry; Mason, Michael D; Wise, John Pierce

2014-11-01

The application of nanoparticle technology is rapidly expanding. The reduced dimensionality of nanoparticles can give rise to changes in chemical and physical properties, often resulting in altered toxicity. People are exposed dermally to titanium dioxide (TiO 2 ) nanoparticles in industrial and residential settings. The general public is increasingly exposed to these nanoparticles as their use in cosmetics, sunscreens and lotions expands. The toxicity of TiO 2 nanoparticles towards human skin cells is unclear and understudied. We used a human skin fibroblast cell line to investigate the cytotoxicity and clastogenicity of TiO 2 nanoparticles after 24 h exposure. In a clonogenic survival assay, treatments of 10, 50 and 100 μg/cm 2 induced 97.8, 88.8 and 84.7% relative survival, respectively. Clastogenicity was assessed using a chromosomal aberration assay in order to determine whether TiO 2 nanoparticles induced serious forms of DNA damage such as chromatid breaks, isochromatid lesions or chromatid exchanges. Treatments of 0, 10, 50 and 100 μg/cm 2 induced 3.3, 3.0, 3.0 and 2.7% metaphases with damage, respectively. No isochromatid lesions or chromatid exchanges were detected. These data show that TiO 2 nanoparticles are not cytotoxic or clastogenic to human skin cells.

Evolutionary implications of phylogenetic analyses of the gene transfer agent (GTA) of Rhodobacter capsulatus.

PubMed

Lang, Andrew S; Taylor, Terumi A; Beatty, J Thomas

2002-11-01

The gene transfer agent (GTA) of the a-proteobacterium Rhodobacter capsulatus is a cell-controlled genetic exchange vector. Genes that encode the GTA structure are clustered in a 15-kb region of the R. capsulatus chromosome, and some of these genes show sequence similarity to known bacteriophage head and tail genes. However, the production of GTA is controlled at the level of transcription by a cellular two-component signal transduction system. This paper describes homologues of both the GTA structural gene cluster and the GTA regulatory genes in the a-proteobacteria Rhodopseudomonas palustris, Rhodobacter sphaeroides, Caulobacter crescentus, Agrobacterium tumefaciens and Brucella melitensis. These sequences were used in a phylogenetic tree approach to examine the evolutionary relationships of selected GTA proteins to these homologues and (pro)phage proteins, which was compared to a 16S rRNA tree. The data indicate that a GTA-like element was present in a single progenitor of the extant species that contain both GTA structural cluster and regulatory gene homologues. The evolutionary relationships of GTA structural proteins to (pro)phage proteins indicated by the phylogenetic tree patterns suggest a predominantly vertical descent of GTA-like sequences in the a-proteobacteria and little past gene exchange with (pro)phages.

Contrasting Histories of Three Gene Regions Associated with In(3l)payne of Drosophila Melanogaster

PubMed Central

Hasson, E.; Eanes, W. F.

1996-01-01

In the present report, we studied nucleotide variation in three gene regions of Drosophila melanogaster, spanning >5 kb and showing different degrees of association with the cosmopolitan inversion In(3-L)Payne. The analysis of sequence variation in the regions surrounding the breakpoints and the heat shock 83 (Hsp83) gene locus, located close to the distal breakpoint, revealed the absence of shared polymorphisms and the presence of a number of fixed differences between arrangements, indicating absence of genetic exchange. In contrast, for the esterase-6 gene region, located in the center of the inversion, we observed the presence of shared polymorphisms between arrangements suggesting genetic exchange. In the regions close to the breakpoints, the common St arrangement is 10 times more polymorphic than inverted chromosomes. We propose that the lack of recombination between arrangements in these regions coupled with genetic hitchhiking is the best explanation for the low heterozygosity observed in inverted lines. Using the data for the breakpoints, we estimate that this inversion polymorphism is around 0.36 million yr old. Although it is widely accepted that inversions are examples of balanced polymorphisms, none of the current neutrality tests including our Monte Carlo simulations showed significant departure from neutral expectations. PMID:8978045

Co-activation of RanGTPase and inhibition of GTP dissociation by Ran-GTP binding protein RanBP1.

PubMed Central

Bischoff, F R; Krebber, H; Smirnova, E; Dong, W; Ponstingl, H

1995-01-01

RCC1 (the regulator of chromosome condensation) stimulates guanine nucleotide dissociation on the Ras-related nuclear protein Ran. Both polypeptides are components of a regulatory pathway that has been implicated in regulating DNA replication, onset of and exit from mitosis, mRNA processing and transport, and import of proteins into the nucleus. In a search for further members of the RCC1-Ran signal pathway, we have identified proteins of 23, 45 and 300 kDa which tightly bind to Ran-GTP but not Ran-GDP. The purified soluble 23 kDa Ran binding protein RanBP1 does not activate RanGTPase, but increases GTP hydrolysis induced by the RanGTPase-activating protein RanGAP1 by an order of magnitude. In the absence of RanGAP, it strongly inhibits RCC1-induced exchange of Ran-bound GTP. In addition, it forms a stable complex with nucleotide-free RCC1-Ran. With these properties, it differs markedly from guanine diphosphate dissociation inhibitors which preferentially prevent the exchange of protein-bound GDP and in some cases were shown to inhibit GAP-induced GTP hydrolysis. RanBP1 is the first member of a new class of proteins regulating the binding and hydrolysis of GTP by Ras-related proteins. Images PMID:7882974

Evolutionary Role of Interspecies Hybridization and Genetic Exchanges in Yeasts

PubMed Central

Dujon, Bernard

2012-01-01

Summary: Forced interspecific hybridization has been used in yeasts for many years to study speciation or to construct artificial strains with novel fermentative and metabolic properties. Recent genome analyses indicate that natural hybrids are also generated spontaneously between yeasts belonging to distinct species, creating lineages with novel phenotypes, varied genetic stability, or altered virulence in the case of pathogens. Large segmental introgressions from evolutionarily distant species are also visible in some yeast genomes, suggesting that interspecific genetic exchanges occur during evolution. The origin of this phenomenon remains unclear, but it is likely based on weak prezygotic barriers, limited Dobzhansky-Muller (DM) incompatibilities, and rapid clonal expansions. Newly formed interspecies hybrids suffer rapid changes in the genetic contribution of each parent, including chromosome loss or aneuploidy, translocations, and loss of heterozygosity, that, except in a few recently studied cases, remain to be characterized more precisely at the genomic level by use of modern technologies. We review here known cases of natural or artificially formed interspecies hybrids between yeasts and discuss their potential importance in terms of genome evolution. Problems of meiotic fertility, ploidy constraint, gene and gene product compatibility, and nucleomitochondrial interactions are discussed and placed in the context of other known mechanisms of yeast genome evolution as a model for eukaryotes. PMID:23204364

X Chromosome of female cells shows dynamic changes in status during human somatic cell reprogramming.

PubMed

Kim, Kun-Yong; Hysolli, Eriona; Tanaka, Yoshiaki; Wang, Brandon; Jung, Yong-Wook; Pan, Xinghua; Weissman, Sherman Morton; Park, In-Hyun

2014-06-03

Induced pluripotent stem cells (iPSCs) acquire embryonic stem cell (ESC)-like epigenetic states, including the X chromosome. Previous studies reported that human iPSCs retain the inactive X chromosome of parental cells, or acquire two active X chromosomes through reprogramming. Most studies investigated the X chromosome states in established human iPSC clones after completion of reprogramming. Thus, it is still not fully understood when and how the X chromosome reactivation occurs during reprogramming. Here, we report a dynamic change in the X chromosome state throughout reprogramming, with an initial robust reactivation of the inactive X chromosome followed by an inactivation upon generation of nascent iPSC clones. iPSCs with two active X chromosomes or an eroded X chromosome arise in passaging iPSCs. These data provide important insights into the plasticity of the X chromosome of human female iPSCs and will be crucial for the future application of such cells in cell therapy and X-linked disease modeling.

The importance of having two X chromosomes

PubMed Central

Arnold, Arthur P.; Reue, Karen; Eghbali, Mansoureh; Vilain, Eric; Chen, Xuqi; Ghahramani, Negar; Itoh, Yuichiro; Li, Jingyuan; Link, Jenny C.; Ngun, Tuck; Williams-Burris, Shayna M.

2016-01-01

Historically, it was thought that the number of X chromosomes plays little role in causing sex differences in traits. Recently, selected mouse models have been used increasingly to compare mice with the same type of gonad but with one versus two copies of the X chromosome. Study of these models demonstrates that mice with one X chromosome can be strikingly different from those with two X chromosomes, when the differences are not attributable to confounding group differences in gonadal hormones. The number of X chromosomes affects adiposity and metabolic disease, cardiovascular ischaemia/reperfusion injury and behaviour. The effects of X chromosome number are likely the result of inherent differences in expression of X genes that escape inactivation, and are therefore expressed from both X chromosomes in XX mice, resulting in a higher level of expression when two X chromosomes are present. The effects of X chromosome number contribute to sex differences in disease phenotypes, and may explain some features of X chromosome aneuploidies such as in Turner and Klinefelter syndromes. PMID:26833834

Holokinetic centromeres and efficient telomere healing enable rapid karyotype evolution.

PubMed

Jankowska, Maja; Fuchs, Jörg; Klocke, Evelyn; Fojtová, Miloslava; Polanská, Pavla; Fajkus, Jiří; Schubert, Veit; Houben, Andreas

2015-12-01

Species with holocentric chromosomes are often characterized by a rapid karyotype evolution. In contrast to species with monocentric chromosomes where acentric fragments are lost during cell division, breakage of holocentric chromosomes creates fragments with normal centromere activity. To decipher the mechanism that allows holocentric species an accelerated karyotype evolution via chromosome breakage, we analyzed the chromosome complements of irradiated Luzula elegans plants. The resulting chromosomal fragments and rearranged chromosomes revealed holocentromere-typical CENH3 and histone H2AThr120ph signals as well as the same mitotic mobility like unfragmented chromosomes. Newly synthesized telomeres at break points become detectable 3 weeks after irradiation. The presence of active telomerase suggests a telomerase-based mechanism of chromosome healing. A successful transmission of holocentric chromosome fragments across different generations was found for most offspring of irradiated plants. Hence, a combination of holokinetic centromere activity and the fast formation of new telomeres at break points enables holocentric species a rapid karyotype evolution involving chromosome fissions and rearrangements.

Cytotaxonomy of two species of genus Chrysolaena H. Robinson, 1988 (Vernonieae, Asteraceae) from Northeast Paraguay

PubMed Central

Pico, Gisela M. Via Do; Dematteis, Massimiliano

2014-01-01

Abstract Chromosome counts and karyotypes of two species of Chrysolaena H. Robinson 1988 are presented in this paper. Mitotic analysis revealed that both taxa have x=10, a basic chromosome number considered characteristic of the genus. The chromosome number and the karyotype of Chrysolaena cristobaliana are reported for the first time, as well as a new cytotype and the karyotype of Chrysolaena sceptrum. Chrysolaena cristobaliana showed heptaploid cytotype with 2n=7x=70 and a karyotype composed of 46 m + 24 sm chromosomes. On the other hand, Chrysolaena sceptrum presented tetraploid cytotype with 2n=4x=40 and a karyotype with 30 m + 10 sm chromosomes. Accessory chromosomes were observed in cells of both species. The chromosome analysis showed that these species differ in the chromosome number and the total chromosome length, although they showed similar chromosome morphology and asymmetry indexes. The results support the use of chromosome data in taxonomic treatments of the American members of the tribe Vernonieae. PMID:25147624

Chromosome Evolution in Connection with Repetitive Sequences and Epigenetics in Plants.

PubMed

Li, Shu-Fen; Su, Ting; Cheng, Guang-Qian; Wang, Bing-Xiao; Li, Xu; Deng, Chuan-Liang; Gao, Wu-Jun

2017-10-24

Chromosome evolution is a fundamental aspect of evolutionary biology. The evolution of chromosome size, structure and shape, number, and the change in DNA composition suggest the high plasticity of nuclear genomes at the chromosomal level. Repetitive DNA sequences, which represent a conspicuous fraction of every eukaryotic genome, particularly in plants, are found to be tightly linked with plant chromosome evolution. Different classes of repetitive sequences have distinct distribution patterns on the chromosomes. Mounting evidence shows that repetitive sequences may play multiple generative roles in shaping the chromosome karyotypes in plants. Furthermore, recent development in our understanding of the repetitive sequences and plant chromosome evolution has elucidated the involvement of a spectrum of epigenetic modification. In this review, we focused on the recent evidence relating to the distribution pattern of repetitive sequences in plant chromosomes and highlighted their potential relevance to chromosome evolution in plants. We also discussed the possible connections between evolution and epigenetic alterations in chromosome structure and repatterning, such as heterochromatin formation, centromere function, and epigenetic-associated transposable element inactivation.

Non-random Mis-segregation of Human Chromosomes.

PubMed

Worrall, Joseph Thomas; Tamura, Naoka; Mazzagatti, Alice; Shaikh, Nadeem; van Lingen, Tineke; Bakker, Bjorn; Spierings, Diana Carolina Johanna; Vladimirou, Elina; Foijer, Floris; McClelland, Sarah Elizabeth

2018-06-12

A common assumption is that human chromosomes carry equal chances of mis-segregation during compromised cell division. Human chromosomes vary in multiple parameters that might generate bias, but technological limitations have precluded a comprehensive analysis of chromosome-specific aneuploidy. Here, by imaging specific centromeres coupled with high-throughput single-cell analysis as well as single-cell sequencing, we show that aneuploidy occurs non-randomly following common treatments to elevate chromosome mis-segregation. Temporary spindle disruption leads to elevated mis-segregation and aneuploidy of a subset of chromosomes, particularly affecting chromosomes 1 and 2. Unexpectedly, we find that a period of mitotic delay weakens centromeric cohesion and promotes chromosome mis-segregation and that chromosomes 1 and 2 are particularly prone to suffer cohesion fatigue. Our findings demonstrate that inherent properties of individual chromosomes can bias chromosome mis-segregation and aneuploidy rates, with implications for studies on aneuploidy in human disease. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Cytogenetic analysis of five Hypostomus species (Siluriformes, Loricariidae)

PubMed Central

Martinez, Emanuel Ricardo Monteiro; Zawadzki, Claudio Henrique; Foresti, Fausto; Oliveira, Claudio

2011-01-01

In this work, we analyzed the karyotypes of five Hypostomus species. Hypostomus cf. heraldoi, from the Mogi-Guaçu River, had 2n = 72 chromosomes, with a nucleolar organizer region (NOR) in one chromosomal pair. Hypostomus regani, from the Mogi-Guaçu River had 2n = 72 chromosomes with NORs in two chromosomal pairs. Hypostomus sp., from the Mogi-Guaçu River basin, had 2n = 68 chromosomes, with NORs in two chromosomal pairs. Hypostomus aff. agna, from Cavalo Stream, had 2n = 74 chromosomes with NORs in two chromosomal pairs. Hypostomus cf. topavae, from Carrapato Stream, had 2n = 80 chromosomes, with NORs in two chromosomal pairs. Hypostomus species showed marked diversity in the karyotypic formula, which suggested the occurrence of several Robertsonian rearrangements and pericentric inversions during the evolutionary history of this genus. This hypothesis was supported by the occurrence of a large number of uniarmed chromosomes and multiple NORs in a terminal position in most species and may be a derived condition in the Loricariidae. PMID:22215958

A new chromosome was born: comparative chromosome painting in Boechera.

PubMed

Koch, Marcus A

2015-09-01

Comparative chromosome painting is a powerful tool to study the evolution of chromosomes and genomes. Analyzing karyotype evolution in cruciferous plants highlights the origin of aberrant chromosomes in apomictic Boechera and further establishes the cruciferous plants as important model system for our understanding of plant chromosome and genome evolution. Copyright © 2015 Elsevier Ltd. All rights reserved.

Ancient Male Recombination Shaped Genetic Diversity of Neo-Y Chromosome in Drosophila albomicans.

PubMed

Satomura, Kazuhiro; Tamura, Koichiro

2016-02-01

Researchers studying Y chromosome evolution have drawn attention to neo-Y chromosomes in Drosophila species due to their resembling the initial stage of Y chromosome evolution. In the studies of neo-Y chromosome of Drosophila miranda, the extremely low genetic diversity observed suggested various modes of natural selection acting on the nonrecombining genome. However, alternative possibility may come from its peculiar origin from a single chromosomal fusion event with male achiasmy, which potentially caused and maintained the low genetic diversity of the neo-Y chromosome. Here, we report a real case where a neo-Y chromosome is in transition from an autosome to a typical Y chromosome. The neo-Y chromosome of Drosophila albomicans harbored a rich genetic diversity comparable to its gametologous neo-X chromosome and an autosome in the same genome. Analyzing sequence variations in 53 genes and measuring recombination rates between pairs of loci by cross experiments, we elucidated the evolutionary scenario of the neo-Y chromosome of D. albomicans having high genetic diversity without assuming selective force, i.e., it originated from a single chromosomal fusion event, experienced meiotic recombination during the initial stage of evolution and diverged from neo-X chromosome by the suppression of recombination tens or a few hundreds of thousand years ago. Consequently, the observed high genetic diversity on the neo-Y chromosome suggested a strong effect of meiotic recombination to introduce genetic variations into the newly arisen sex chromosome. © The Author 2015. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Comparative mapping of human alphoid centromeric sequences in great apes

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

Archidiacono, N.; Antonacci, R.; Marzella, R.

1994-09-01

Metaphase spreads from chimpanzees (Pan troglodytes and Pan paniscus) and gorilla (Gorilla gorilla) have been hybridized in situ with 27 alphoid DNA probes specific for the centromere of human chromosomes, to investigate the evolutionary relationship between centromeric regions of human and great apes. The results showed that most human probes do not recognize their corresponding homologs in great apes. Chromosome X is the only chromosome showing localization consistency in all the four species. Each suprachromosomal family (SCF) exhibits a distinct and peculiar evolutionary history. SCF1 (chromosomes 1, 3, 6, 7, 19, 12, 16) is very heterogeneous: some probes gave intensemore » signals, but always on non-homologous chromosomes; others did not produce any hybridization signal. All probes localized on SCF2 (chromosomes 2, 4, 8, 9, 13, 14, 15, 18, 20, 21, and 22) recognize a single chromosome: chromosome 11 (phylogenetic IX) in PTR and PPA; chromosome 4 (phylogenetic V) in GGO. SCF3 subsets (chromosomes 1, 11, 17, X) are substantially conserved in PTR and PPA, but not in GGO, with the exception restricted to chromosome X. No signals have been detected on PPA chromosomes I, III, IV, V, VI and in PTR chromosomes V, suggesting that the centromeric region of some chromsomes have probably lost homology with human alphoid sequences.« less

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.

Repetitive DNA and meiotic behavior of sex chromosomes in Gymnotus pantanal (Gymnotiformes, Gymnotidae).

PubMed

da Silva, M; Matoso, D A; Vicari, M R; de Almeida, M C; Margarido, V P; Artoni, R F

2011-01-01

Neotropical fishes have a low rate of chromosome differentiation between sexes. The present study characterizes the first meiotic analysis of sex chromosomes in the order Gymnotiformes. Gymnotus pantanal - females had 40 chromosomes (14m/sm, 26st/a) and males had 39 chromosomes (15m/sm, 24st/a), with a fundamental number of 54 - showed a multiple sexual determination chromosome system of the type X(1)X(1)X(2)X(2)/X(1)X(2)Y. The heterochromatin is restricted to centromeres of all chromosomes of the karyotype. The meiotic behavior of sex chromosomes involved in this system in males is from a trivalent totally pared in the pachytene stage, with a high degree of similarity. The cells of metaphase II exhibit 19 and 20 chromosomes, normal disjunction of sex chromosomes and the formation of balanced gametes with 18 + Y and 18 + X(1)X(2) chromosomes, respectively. The small amount of heterochromatin and repetitive DNA involved in this system and the high degree of chromosome similarity indicated a recent origin of the X(1)X(1)X(2)X(2)/X(1)X(2)Y system in G. pantanal and suggests the existence of a simple ancestral system with morphologically undifferentiated chromosomes. Copyright © 2011 S. Karger AG, Basel.

Preferential elimination of chromosome 1D from homoeologous group-1 alien addition lines in hexaploid wheat.

PubMed

Garg, Monika; Elamein, Hala M M; Tanaka, Hiroyuki; Tsujimoto, Hisashi

2007-10-01

Alien chromosome addition lines are useful genetic material for studying the effect of an individual chromosome in the same genetic background. However, addition lines are sometimes unstable and tend to lose the alien chromosome in subsequent generations. In this study, we report preferential removal of chromosome 1D rather than the alien chromosome from homoeologous group-1 addition lines. The Agropyron intermedium chromosome 1Agi (1E) addition line, created in the background of 'Vilmorin 27', showed loss of a part of chromosome 1D, thereby losing its HMW glutenin locus. Even in the case of Aegilops longissima and Ae. peregrina, the genomes of which are closer to the B genome than D genome, chromosome 1D was lost from chromosome 1Sl and 1Sv addition lines in cv. 'Chinese Spring' rather than chromosome 1B during transfer from one generation to another. A similar observation was also observed in the case of a chromosome 1E disomic addition line of Ag. elongatum and alloplasmic common wheat line with Ag. intermedium ssp. trichophorum cytoplasm. The reason for this strange observation is thought to lie in the history of wheat evolution, the size of chromosome 1D compared to 1A and 1B, or differing pollen competition abilities.

Single cell Hi-C reveals cell-to-cell variability in chromosome structure

PubMed Central

Schoenfelder, Stefan; Yaffe, Eitan; Dean, Wendy; Laue, Ernest D.; Tanay, Amos; Fraser, Peter

2013-01-01

Large-scale chromosome structure and spatial nuclear arrangement have been linked to control of gene expression and DNA replication and repair. Genomic techniques based on chromosome conformation capture assess contacts for millions of loci simultaneously, but do so by averaging chromosome conformations from millions of nuclei. Here we introduce single cell Hi-C, combined with genome-wide statistical analysis and structural modeling of single copy X chromosomes, to show that individual chromosomes maintain domain organisation at the megabase scale, but show variable cell-to-cell chromosome territory structures at larger scales. Despite this structural stochasticity, localisation of active gene domains to boundaries of territories is a hallmark of chromosomal conformation. Single cell Hi-C data bridge current gaps between genomics and microscopy studies of chromosomes, demonstrating how modular organisation underlies dynamic chromosome structure, and how this structure is probabilistically linked with genome activity patterns. PMID:24067610

Chromosomal evolution of the Canidae. II. Divergence from the primitive carnivore karyotype.

PubMed

Wayne, R K; Nash, W G; O'Brien, S J

1987-01-01

The Giemsa-banding patterns of chromosomes from the arctic fox (Alopex lagopus), the red fox (Vulpes vulpes), the kit fox (Vulpes macrotis), and the raccoon dog (Nyctereutes procyonoides) are compared. Despite their traditional placement in different genera, the arctic fox and the kit fox have an identical chromosome morphology and G-banding pattern. The red fox has extensive chromosome arm homoeology with these two species, but has only two entire chromosomes in common. All three species share some chromosomes with the raccoon dog, as does the high diploid-numbered grey wolf (Canis lupus, 2n = 78). Moreover, some chromosomes of the raccoon dog show partial or complete homoeology with metacentric feline chromosomes which suggests that these are primitive canid chromosomes. We present the history of chromosomal rearrangements within the Canidae family based on the assumption that a metacentric-dominated karyotype is primitive for the group.

Function of the Sex Chromosomes in Mammalian Fertility

PubMed Central

Heard, Edith; Turner, James

2011-01-01

The sex chromosomes play a highly specialized role in germ cell development in mammals, being enriched in genes expressed in the testis and ovary. Sex chromosome abnormalities (e.g., Klinefelter [XXY] and Turner [XO] syndrome) constitute the largest class of chromosome abnormalities and the commonest genetic cause of infertility in humans. Understanding how sex-gene expression is regulated is therefore critical to our understanding of human reproduction. Here, we describe how the expression of sex-linked genes varies during germ cell development; in females, the inactive X chromosome is reactivated before meiosis, whereas in males the X and Y chromosomes are inactivated at this stage. We discuss the epigenetics of sex chromosome inactivation and how this process has influenced the gene content of the mammalian X and Y chromosomes. We also present working models for how perturbations in sex chromosome inactivation or reactivation result in subfertility in the major classes of sex chromosome abnormalities. PMID:21730045

Identification of supernumerary ring chromosome 1 mosaicism using fluorescence in situ hybridization.

PubMed

Chen, H; Tuck-Muller, C M; Batista, D A; Wertelecki, W

1995-03-27

We report on a 15-year-old black boy with severe mental retardation, multiple congenital anomalies, and a supernumerary ring chromosome mosaicism. Fluorescence in situ hybridization with a chromosome 1 painting probe (pBS1) identified the ring as derived from chromosome 1. The karyotype was 46,XY/47,XY,+r(1)(p13q23). A review showed 8 reports of ring chromosome 1. In 5 cases, the patients had a non-supernumerary ring chromosome 1 resulting in partial monosomies of the short and/or long arm of chromosome 1. In 3 cases, the presence of a supernumerary ring resulted in partial trisomy of different segments of chromosome 1. In one of these cases the supernumerary ring was composed primarily of the centromere and the heterochromatic region of chromosome 1, resulting in normal phenotype. Our patient represents the third report of a supernumerary ring chromosome 1 resulting in abnormal phenotype.

Geographic distribution of chromosome and microsatellite DNA polymorphisms in Oncorhynchus mykiss native to western Washington

USGS Publications Warehouse

Ostberg, C.O.; Thorgaard, G.H.

1999-01-01

Chromosome studies of native populations of Oncorhynchus mykiss (steelhead and rainbow trout) in western Washington and southern British Columbia revealed the presence of two evolutionarily distinct chromosome lineages. Populations between, and including, the Elwha River, Washington, and Chilliwack River, British Columbia, contained 2n = 60 chromosomes. Populations on the central Washington coast contained 2n = 58 chromosomes. The north Washington coast and western Strait of Juan de Fuca contained individuals with 58, 59, or 60 chromosomes, suggesting this is a transition zone between 58 and 60 chromosome groups. The differences in chromosomal structure between 2n = 58 and 2n = 60 groups are presumably a Robertsonian rearrangement and an inversion. Allelic variation at three microsatellite loci (One ??6, One ??11 and Omy 77) also was examined, and no significant variation was detected among the 58 and 60 chromosome races. A hypothesis is presented concerning the origin of the 60 chromosome lineage.

Mitotic Recombination in the Heterochromatin of the Sex Chromosomes of DROSOPHILA MELANOGASTER

PubMed Central

Ripoll, P.; Garcia-Bellido, A.

1978-01-01

The frequency of spontaneous and X-ray-induced mitotic recombination involving the Y chromosome has been studied in individuals with a marked Y chromosome arm and different XY compound chromosomes. The genotypes used include X chromosomes with different amounts of X heterochromatin and either or both arms of the Y chromosome attached to either side of the centromere. Individuals with two Y chromosomes have also been studied. The results show that the bulk of mitotic recombination takes place between homologous regions. PMID:100372

Evidence for different origin of sex chromosomes in snakes, birds, and mammals and step-wise differentiation of snake sex chromosomes

PubMed Central

Matsubara, Kazumi; Tarui, Hiroshi; Toriba, Michihisa; Yamada, Kazuhiko; Nishida-Umehara, Chizuko; Agata, Kiyokazu; Matsuda, Yoichi

2006-01-01

All snake species exhibit genetic sex determination with the ZZ/ZW type of sex chromosomes. To investigate the origin and evolution of snake sex chromosomes, we constructed, by FISH, a cytogenetic map of the Japanese four-striped rat snake (Elaphe quadrivirgata) with 109 cDNA clones. Eleven of the 109 clones were localized to the Z chromosome. All human and chicken homologues of the snake Z-linked genes were located on autosomes, suggesting that the sex chromosomes of snakes, mammals, and birds were all derived from different autosomal pairs of the common ancestor. We mapped the 11 Z-linked genes of E. quadrivirgata to chromosomes of two other species, the Burmese python (Python molurus bivittatus) and the habu (Trimeresurus flavoviridis), to investigate the process of W chromosome differentiation. All and 3 of the 11 clones were localized to both the Z and W chromosomes in P. molurus and E. quadrivirgata, respectively, whereas no cDNA clones were mapped to the W chromosome in T. flavoviridis. Comparative mapping revealed that the sex chromosomes are only slightly differentiated in P. molurus, whereas they are fully differentiated in T. flavoviridis, and E. quadrivirgata is at a transitional stage of sex-chromosome differentiation. The differentiation of sex chromosomes was probably initiated from the distal region on the short arm of the protosex chromosome of the common ancestor, and then deletion and heterochromatization progressed on the sex-specific chromosome from the phylogenetically primitive boids to the more advanced viperids. PMID:17110446

Selfish supernumerary chromosome reveals its origin as a mosaic of host genome and organellar sequences.

PubMed

Martis, Mihaela Maria; Klemme, Sonja; Banaei-Moghaddam, Ali Mohammad; Blattner, Frank R; Macas, Jiří; Schmutzer, Thomas; Scholz, Uwe; Gundlach, Heidrun; Wicker, Thomas; Šimková, Hana; Novák, Petr; Neumann, Pavel; Kubaláková, Marie; Bauer, Eva; Haseneyer, Grit; Fuchs, Jörg; Doležel, Jaroslav; Stein, Nils; Mayer, Klaus F X; Houben, Andreas

2012-08-14

Supernumerary B chromosomes are optional additions to the basic set of A chromosomes, and occur in all eukaryotic groups. They differ from the basic complement in morphology, pairing behavior, and inheritance and are not required for normal growth and development. The current view is that B chromosomes are parasitic elements comparable to selfish DNA, like transposons. In contrast to transposons, they are autonomously inherited independent of the host genome and have their own mechanisms of mitotic or meiotic drive. Although B chromosomes were first described a century ago, little is known about their origin and molecular makeup. The widely accepted view is that they are derived from fragments of A chromosomes and/or generated in response to interspecific hybridization. Through next-generation sequencing of sorted A and B chromosomes, we show that B chromosomes of rye are rich in gene-derived sequences, allowing us to trace their origin to fragments of A chromosomes, with the largest parts corresponding to rye chromosomes 3R and 7R. Compared with A chromosomes, B chromosomes were also found to accumulate large amounts of specific repeats and insertions of organellar DNA. The origin of rye B chromosomes occurred an estimated ∼1.1-1.3 Mya, overlapping in time with the onset of the genus Secale (1.7 Mya). We propose a comprehensive model of B chromosome evolution, including its origin by recombination of several A chromosomes followed by capturing of additional A-derived and organellar sequences and amplification of B-specific repeats.

High-resolution FISH on super-stretched flow-sorted plant chromosomes.

PubMed

Valárik, M; Bartos, J; Kovárová, P; Kubaláková, M; de Jong, J H; Dolezel, J

2004-03-01

A novel high-resolution fluorescence in situ hybridisation (FISH) strategy, using super-stretched flow-sorted plant chromosomes as targets, is described. The technique that allows longitudinal extension of chromosomes of more than 100 times their original metaphase size is especially attractive for plant species with large chromosomes, whose pachytene chromosomes are generally too long and heterochromatin patterns too complex for FISH analysis. The protocol involves flow cytometric sorting of metaphase chromosomes, mild proteinase-K digestion of air-dried chromosomes on microscopic slides, followed by stretching with ethanol:acetic acid (3 : 1). Stretching ratios were assessed in a number of FISH experiments with super-stretched chromosomes from barley, wheat, rye and chickpea, hybridised with 45S and 5S ribosomal DNAs and the [GAA]n microsatellite, the [TTTAGGG]n telomeric repeat and a bacterial artificial chromosome (BAC) clone as probes. FISH signals on stretched chromosomes were brighter than those on the untreated control, resulting from better accessibility of the stretched chromatin and maximum observed sensitivity of 1 kbp. Spatial resolution of neighbouring loci was improved down to 70 kbp as compared to 5-10 Mbp after FISH on mitotic chromosomes, revealing details of adjacent DNA sequences hitherto not obtained with any other method. Stretched chromosomes are advantageous over extended DNA fibres from interphase nuclei as targets for FISH studies because they still retain chromosomal integrity. Although the method is confined to species for which chromosome flow sorting has been developed, it provides a unique system for controlling stretching degree of mitotic chromosomes and high-resolution bar-code FISH.

Dynamics of chromosome number and genome size variation in a cytogenetically variable sedge (Carex scoparia var. scoparia, Cyperaceae).

PubMed

Chung, Kyong-Sook; Weber, Jaime A; Hipp, Andrew L

2011-01-01

High intraspecific cytogenetic variation in the sedge genus Carex (Cyperaceae) is hypothesized to be due to the "diffuse" or non-localized centromeres, which facilitate chromosome fission and fusion. If chromosome number changes are dominated by fission and fusion, then chromosome evolution will result primarily in changes in the potential for recombination among populations. Chromosome duplications, on the other hand, entail consequent opportunities for divergent evolution of paralogs. In this study, we evaluate whether genome size and chromosome number covary within species. We used flow cytometry to estimate genome sizes in Carex scoparia var. scoparia, sampling 99 plants (23 populations) in the Chicago region, and we used meiotic chromosome observations to document chromosome numbers and chromosome pairing relations. Chromosome numbers range from 2n = 62 to 2n = 68, and nuclear DNA 1C content from 0.342 to 0.361 pg DNA. Regressions of DNA content on chromosome number are nonsignificant for data analyzed by individual or population, and a regression model that excludes slope is favored over a model in which chromosome number predicts genome size. Chromosome rearrangements within cytogenetically variable Carex species are more likely a consequence of fission and fusion than of duplication and deletion. Moreover, neither genome size nor chromosome number is spatially autocorrelated, which suggests the potential for rapid chromosome evolution by fission and fusion at a relatively fine geographic scale (<350 km). These findings have important implications for ecological restoration and speciation within the largest angiosperm genus of the temperate zone.

Isolation and evaluation of cytogenetic effect of Brahmi saponins on cultured human lymphocytes exposed in vitro.

PubMed

Kalachaveedu, Mangathayaru; Papacchan, Sunu; Sanyal, Sudip; Koshy, Teena; Telapolu, Srivani

2015-01-01

Major saponins of Brahmi (Bacopa monniera, Fam: Scrophulariaceae) - bacosides A and B - were isolated from the total methanol extract and characterised based on melting point, TLC, IR, (1)H NMR and (13)C NMR. They were evaluated for their in vitro cytogenetic effects on human peripheral blood lymphocytes by chromosomal aberration (CA) assay and sister chromatid exchange (SCE) assay. The frequency of chromatid type aberrations and reciprocal interchanges between sister chromatids in the treated cells was scored in comparison to the untreated control. At 30 μg/mL dose, bacoside A showed a statistically significant increase in the frequency of both CA and SCE and bacoside B showed an increase only in SCE. Our report of the genotoxicity of the saponins is significant in view of the reports of anticancer activity of Brahmi extracts.

Plant genetics. Early allopolyploid evolution in the post-Neolithic Brassica napus oilseed genome.

PubMed

Chalhoub, Boulos; Denoeud, France; Liu, Shengyi; Parkin, Isobel A P; Tang, Haibao; Wang, Xiyin; Chiquet, Julien; Belcram, Harry; Tong, Chaobo; Samans, Birgit; Corréa, Margot; Da Silva, Corinne; Just, Jérémy; Falentin, Cyril; Koh, Chu Shin; Le Clainche, Isabelle; Bernard, Maria; Bento, Pascal; Noel, Benjamin; Labadie, Karine; Alberti, Adriana; Charles, Mathieu; Arnaud, Dominique; Guo, Hui; Daviaud, Christian; Alamery, Salman; Jabbari, Kamel; Zhao, Meixia; Edger, Patrick P; Chelaifa, Houda; Tack, David; Lassalle, Gilles; Mestiri, Imen; Schnel, Nicolas; Le Paslier, Marie-Christine; Fan, Guangyi; Renault, Victor; Bayer, Philippe E; Golicz, Agnieszka A; Manoli, Sahana; Lee, Tae-Ho; Thi, Vinh Ha Dinh; Chalabi, Smahane; Hu, Qiong; Fan, Chuchuan; Tollenaere, Reece; Lu, Yunhai; Battail, Christophe; Shen, Jinxiong; Sidebottom, Christine H D; Wang, Xinfa; Canaguier, Aurélie; Chauveau, Aurélie; Bérard, Aurélie; Deniot, Gwenaëlle; Guan, Mei; Liu, Zhongsong; Sun, Fengming; Lim, Yong Pyo; Lyons, Eric; Town, Christopher D; Bancroft, Ian; Wang, Xiaowu; Meng, Jinling; Ma, Jianxin; Pires, J Chris; King, Graham J; Brunel, Dominique; Delourme, Régine; Renard, Michel; Aury, Jean-Marc; Adams, Keith L; Batley, Jacqueline; Snowdon, Rod J; Tost, Jorg; Edwards, David; Zhou, Yongming; Hua, Wei; Sharpe, Andrew G; Paterson, Andrew H; Guan, Chunyun; Wincker, Patrick

2014-08-22

Oilseed rape (Brassica napus L.) was formed ~7500 years ago by hybridization between B. rapa and B. oleracea, followed by chromosome doubling, a process known as allopolyploidy. Together with more ancient polyploidizations, this conferred an aggregate 72× genome multiplication since the origin of angiosperms and high gene content. We examined the B. napus genome and the consequences of its recent duplication. The constituent An and Cn subgenomes are engaged in subtle structural, functional, and epigenetic cross-talk, with abundant homeologous exchanges. Incipient gene loss and expression divergence have begun. Selection in B. napus oilseed types has accelerated the loss of glucosinolate genes, while preserving expansion of oil biosynthesis genes. These processes provide insights into allopolyploid evolution and its relationship with crop domestication and improvement. Copyright © 2014, American Association for the Advancement of Science.

Amplification of chromosomal DNA in situ

DOEpatents

Christian, Allen T.; Coleman, Matthew A.; Tucker, James D.

2002-01-01

Amplification of chromosomal DNA in situ to increase the amount of DNA associated with a chromosome or chromosome region is described. The amplification of chromosomal DNA in situ provides for the synthesis of Fluorescence in situ Hybridization (FISH) painting probes from single dissected chromosome fragments, the production of cDNA libraries from low copy mRNAs and improved in Comparative Genomic Hybridization (CGH) procedures.

Characterizing the chromosomes of the platypus (Ornithorhynchus anatinus).

PubMed

McMillan, Daniel; Miethke, Pat; Alsop, Amber E; Rens, Willem; O'Brien, Patricia; Trifonov, Vladimir; Veyrunes, Frederic; Schatzkamer, Kyriena; Kremitzki, Colin L; Graves, Tina; Warren, Wesley; Grützner, Frank; Ferguson-Smith, Malcolm A; Graves, Jennifer A Marshall

2007-01-01

Like the unique platypus itself, the platypus genome is extraordinary because of its complex sex chromosome system, and is controversial because of difficulties in identification of small autosomes and sex chromosomes. A 6-fold shotgun sequence of the platypus genome is now available and is being assembled with the help of physical mapping. It is therefore essential to characterize the chromosomes and resolve the ambiguities and inconsistencies in identifying autosomes and sex chromosomes. We have used chromosome paints and DAPI banding to identify and classify pairs of autosomes and sex chromosomes. We have established an agreed nomenclature and identified anchor BAC clones for each chromosome that will ensure unambiguous gene localizations.

Chromosomal location and gene paucity of the male specific region on papaya Y chromosome.

PubMed

Yu, Qingyi; Hou, Shaobin; Hobza, Roman; Feltus, F Alex; Wang, Xiue; Jin, Weiwei; Skelton, Rachel L; Blas, Andrea; Lemke, Cornelia; Saw, Jimmy H; Moore, Paul H; Alam, Maqsudul; Jiang, Jiming; Paterson, Andrew H; Vyskot, Boris; Ming, Ray

2007-08-01

Sex chromosomes in flowering plants evolved recently and many of them remain homomorphic, including those in papaya. We investigated the chromosomal location of papaya's small male specific region of the hermaphrodite Y (Yh) chromosome (MSY) and its genomic features. We conducted chromosome fluorescence in situ hybridization mapping of Yh-specific bacterial artificial chromosomes (BACs) and placed the MSY near the centromere of the papaya Y chromosome. Then we sequenced five MSY BACs to examine the genomic features of this specialized region, which resulted in the largest collection of contiguous genomic DNA sequences of a Y chromosome in flowering plants. Extreme gene paucity was observed in the papaya MSY with no functional gene identified in 715 kb MSY sequences. A high density of retroelements and local sequence duplications were detected in the MSY that is suppressed for recombination. Location of the papaya MSY near the centromere might have provided recombination suppression and fostered paucity of genes in the male specific region of the Y chromosome. Our findings provide critical information for deciphering the sex chromosomes in papaya and reference information for comparative studies of other sex chromosomes in animals and plants.

Unique sex chromosome systems in Ellobius: How do male XX chromosomes recombine and undergo pachytene chromatin inactivation?

PubMed

Matveevsky, Sergey; Bakloushinskaya, Irina; Kolomiets, Oxana

2016-07-18

Most mammalian species have heteromorphic sex chromosomes in males, except for a few enigmatic groups such as the mole voles Ellobius, which do not have the Y chromosome and Sry gene. The Ellobius (XX ♀♂) system of sex chromosomes has no analogues among other animals. The structure and meiotic behaviour of the two X chromosomes were investigated for males of the sibling species Ellobius talpinus and Ellobius tancrei. Their sex chromosomes, despite their identical G-structure, demonstrate short synaptic fragments and crossover-associated MLH1 foci in both telomeric regions only. The chromatin undergoes modifications in the meiotic sex chromosomes. SUMO-1 marks a small nucleolus-like body of the meiotic XX. ATR and ubiH2A are localized in the asynaptic area and the histone γH2AFX covers the entire XX bivalent. The distribution of some markers of chromatin inactivation differentiates sex chromosomes of mole voles from those of other mammals. Sex chromosomes of both studied species have identical recombination and meiotic inactivation patterns. In Ellobius, similar chromosome morphology masks the functional heteromorphism of the male sex chromosomes, which can be seen at meiosis.

Unique sex chromosome systems in Ellobius: How do male XX chromosomes recombine and undergo pachytene chromatin inactivation?

PubMed Central

Matveevsky, Sergey; Bakloushinskaya, Irina; Kolomiets, Oxana

2016-01-01

Most mammalian species have heteromorphic sex chromosomes in males, except for a few enigmatic groups such as the mole voles Ellobius, which do not have the Y chromosome and Sry gene. The Ellobius (XX ♀♂) system of sex chromosomes has no analogues among other animals. The structure and meiotic behaviour of the two X chromosomes were investigated for males of the sibling species Ellobius talpinus and Ellobius tancrei. Their sex chromosomes, despite their identical G-structure, demonstrate short synaptic fragments and crossover-associated MLH1 foci in both telomeric regions only. The chromatin undergoes modifications in the meiotic sex chromosomes. SUMO-1 marks a small nucleolus-like body of the meiotic XX. ATR and ubiH2A are localized in the asynaptic area and the histone γH2AFX covers the entire XX bivalent. The distribution of some markers of chromatin inactivation differentiates sex chromosomes of mole voles from those of other mammals. Sex chromosomes of both studied species have identical recombination and meiotic inactivation patterns. In Ellobius, similar chromosome morphology masks the functional heteromorphism of the male sex chromosomes, which can be seen at meiosis. PMID:27425629

Optical selection and collection of DNA fragments

DOEpatents

Roslaniec, Mary C.; Martin, John C.; Jett, James H.; Cram, L. Scott

1998-01-01

Optical selection and collection of DNA fragments. The present invention includes the optical selection and collection of large (>.mu.g) quantities of clonable, chromosome-specific DNA from a sample of chromosomes. Chromosome selection is based on selective, irreversible photoinactivation of unwanted chromosomal DNA. Although more general procedures may be envisioned, the invention is demonstrated by processing chromosomes in a conventional flow cytometry apparatus, but where no droplets are generated. All chromosomes in the sample are first stained with at least one fluorescent analytic dye and bonded to a photochemically active species which can render chromosomal DNA unclonable if activated. After passing through analyzing light beam(s), unwanted chromosomes are irradiated using light which is absorbed by the photochemically active species, thereby causing photoinactivation. As desired chromosomes pass this photoinactivation point, the inactivating light source is deflected by an optical modulator; hence, desired chromosomes are not photoinactivated and remain clonable. The selection and photoinactivation processes take place on a microsecond timescale. By eliminating droplet formation, chromosome selection rates 50 times greater than those possible with conventional chromosome sorters may be obtained. Thus, usable quantities of clonable DNA from any source thereof may be collected.

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.

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

Andrew, S.E.; Goldberg, Y.P.; Squitieri, F.

Huntington disease (HD) is one of 7 disorders now known to be caused by expansion of a trinucleotide repeat. The HD mutation is a polymorphic trinucleotide (CAG) repeat in the 5{prime} region of a novel gene that expands beyond the normal range of 10-35 repeats in persons destined to develop the disease. Haplotype analysis of other dynamic mutation disorders such as myotonic dystrophy and Fragil X have suggested that a rare ancestral expansion event on a normal chromosome is followed by subsequent expansion events, resulting in a pool of chromosomes in the premutation range, which is inherently unstable and pronemore » to further multiple expansion events leading to disease range chromosomes. Haplotype analysis of 67 HD and 84 control chromosomes using 5 polymorphic markers, both intragenic and 5{prime} to the disease mutation, demonstrate that multiple haplotypes underlie HD. However, 94% of the chromosomes can be grouped under two major haplotypes. These two haplotypes are also present in the normal population. A third major haplotype is seen on 38% of normal chromosomes but rarely on HD chromosomes (6%). CAG lengths on the normal chromosomes with the two haplotypes seen in the HD population are higher than those seen on the normal chromosomes with the haplotype rarely seen on HD chromosomes. Furthermore, in populations with a diminished frequency of HD, CAG length on normal chromosomes is significantly less than other populations with higher prevalence rates for HD. These data suggest that CAG length on normal chromosomes may be a significant factor contributing to repeat instability that eventually leads to chromosomes with CAG repeat lengths in the HD range. Haplotypes on the HD chromosomes are identical to those normal chromosomes which have CAG lengths in the high range of normal, suggesting that further expansions of this pool of chromosomes leads to chromosomes with CAG repeat sizes within the disease range, consistent with a multistep model.« less

Chromosomal Aneuploidy Improves the Brewing Characteristics of Sake Yeast.

PubMed

Kadowaki, Masafumi; Fujimaru, Yuki; Taguchi, Seiga; Ferdouse, Jannatul; Sawada, Kazutaka; Kimura, Yuta; Terasawa, Yohei; Agrimi, Gennaro; Anai, Toyoaki; Noguchi, Hideki; Toyoda, Atsushi; Fujiyama, Asao; Akao, Takeshi; Kitagaki, Hiroshi

2017-12-15

The effect of chromosomal aneuploidy on the brewing characteristics of brewery yeasts has not been studied. Here we report that chromosomal aneuploidy in sake brewery yeast ( Saccharomyces cerevisiae ) leads to the development of favorable brewing characteristics. We found that pyruvate-underproducing sake yeast, which produces less off-flavor diacetyl, is aneuploid and trisomic for chromosomes XI and XIV. To confirm that this phenotype is due to aneuploidy, we obtained 45 haploids with various chromosomal additions and investigated their brewing profiles. A greater number of chromosomes correlated with a decrease in pyruvate production. Especially, sake yeast haploids with extra chromosomes in addition to chromosome XI produced less pyruvate than euploids. Mitochondrion-related metabolites and intracellular oxygen species in chromosome XI aneuploids were higher than those in euploids, and this effect was canceled in their "petite" strains, suggesting that an increase in chromosomes upregulated mitochondrial activity and decreased pyruvate levels. These findings suggested that an increase in chromosome number, including chromosome XI, in sake yeast haploids leads to pyruvate underproduction through the augmentation of mitochondrial activity. This is the first report proposing that aneuploidy in brewery yeasts improves their brewing profile. IMPORTANCE Chromosomal aneuploidy has not been evaluated in development of sake brewing yeast strains. This study shows the relationship between chromosomal aneuploidy and brewing characteristics of brewery yeast strains. High concentrations of pyruvate during sake storage give rise to α-acetolactate and, in turn, to high concentrations of diacetyl, which is considered an off-flavor. It was demonstrated that pyruvate-underproducing sake yeast is trisomic for chromosome XI and XIV. Furthermore, sake yeast haploids with extra chromosomes produced reduced levels of pyruvate and showed metabolic processes characteristic of increased mitochondrial activity. This novel discovery will enable the selection of favorable brewery yeasts by monitoring the copy numbers of specific chromosomes through a process that does not involve generation/use of genetically modified organisms. Copyright © 2017 American Society for Microbiology.

Chromosomal Aneuploidy Improves the Brewing Characteristics of Sake Yeast

PubMed Central

Kadowaki, Masafumi; Fujimaru, Yuki; Taguchi, Seiga; Ferdouse, Jannatul; Sawada, Kazutaka; Kimura, Yuta; Terasawa, Yohei; Agrimi, Gennaro; Anai, Toyoaki; Noguchi, Hideki; Toyoda, Atsushi; Fujiyama, Asao; Akao, Takeshi

2017-01-01

ABSTRACT The effect of chromosomal aneuploidy on the brewing characteristics of brewery yeasts has not been studied. Here we report that chromosomal aneuploidy in sake brewery yeast (Saccharomyces cerevisiae) leads to the development of favorable brewing characteristics. We found that pyruvate-underproducing sake yeast, which produces less off-flavor diacetyl, is aneuploid and trisomic for chromosomes XI and XIV. To confirm that this phenotype is due to aneuploidy, we obtained 45 haploids with various chromosomal additions and investigated their brewing profiles. A greater number of chromosomes correlated with a decrease in pyruvate production. Especially, sake yeast haploids with extra chromosomes in addition to chromosome XI produced less pyruvate than euploids. Mitochondrion-related metabolites and intracellular oxygen species in chromosome XI aneuploids were higher than those in euploids, and this effect was canceled in their “petite” strains, suggesting that an increase in chromosomes upregulated mitochondrial activity and decreased pyruvate levels. These findings suggested that an increase in chromosome number, including chromosome XI, in sake yeast haploids leads to pyruvate underproduction through the augmentation of mitochondrial activity. This is the first report proposing that aneuploidy in brewery yeasts improves their brewing profile. IMPORTANCE Chromosomal aneuploidy has not been evaluated in development of sake brewing yeast strains. This study shows the relationship between chromosomal aneuploidy and brewing characteristics of brewery yeast strains. High concentrations of pyruvate during sake storage give rise to α-acetolactate and, in turn, to high concentrations of diacetyl, which is considered an off-flavor. It was demonstrated that pyruvate-underproducing sake yeast is trisomic for chromosome XI and XIV. Furthermore, sake yeast haploids with extra chromosomes produced reduced levels of pyruvate and showed metabolic processes characteristic of increased mitochondrial activity. This novel discovery will enable the selection of favorable brewery yeasts by monitoring the copy numbers of specific chromosomes through a process that does not involve generation/use of genetically modified organisms. PMID:28986374

Chromosome diversity and similarity within the Actinomycetales.

PubMed

Kirby, Ralph

2011-06-01

Many chromosomes from Actinomycetales, an order within the Actinobacteria, have been sequenced over the last 10 years and the pace is increasing. This group of Gram-positive and high G+C% bacteria is economically and medically important. However, this group of organisms also is just about the only order in the kingdom Bacteria to have a relatively high proportion of linear chromosomes. Chromosome topology varies within the order according to the genera. Streptomyces, Kitasatospora and Rhodococcus, at least as chromosome sequencing stands at present, have a very high proportion of linear chromosomes, whereas most other genera seem to have circular chromosomes. This review examines chromosome topology across the Actinomycetales and how this affects our concepts of chromosome evolution. © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

A STUDY OF MEIOSIS IN THE PROGENY OF X-IRRADIATED LUZULA PURPUREA

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

Nordenskiold, H.

1963-01-01

In Luzula the chromosomes have diffuse or nonlocalized centromeres; thus, if the chromosomes are broken or rearranged by x-ray treatment, the changed chromosome patterns may survive through the mitotic cell divisions, on account of the centromeric action along the whole chromosomes. Hence, such plants with diffuse centromeres are able to survive and reach adult stages in spite of the fact that their chromosomes have been rearranged or broken by x-ray treatment of the seedlings. A study was made of plants selected from the progeny of material treated as seedlings with 1000 or 2500 r. Plants treated with stronger doses (5000more » to 10000 r) were almost or completely sterile. The chromosome patterns of the root tips of X/sub 2/ plants were investigated in order to find plants with desirable chrom-osome patterns for the meiotic investigation. The x-irradiated plants themselves showed intricate metaphasic configurations during meiosis. The separation of the multi-associations at first anaphase is cytologically equational, and in most cases without bridges. Migration of chromatids during second anaphase is also regular without lagging chromosomes, but chromosome sets of 4 tetrad cells usually become unbalanced, causing reduced fertility. The mitotic chromosome patterns of X/sub 2/ plants showed three categories of patterns: 2n = 6; most of these plants have all chromosomes the same size, but some of them possess one long and one short chromosome indicating a reciprocal translocation between two chromosomes; 2n = 7, with one of the original chromosomes fragmented into two pieces; and 2n = 8, with two of the original chromosomes fragmented into two pieces each. A study was made of meiosis in X/ sub 2/ plants with a cytologically observable rearrangement in the root tips, determined as a reciprocal progeny plants were obtained. Meiosis of X/sub 2/ plants heterozygous for one chromosome fragmented into two pieces, i.e., possessing 2n = 7 with five normal-sized and two small half-sized chromosomes, was also studied. The expected course of meiosis was realized, giving rise to four balanced chromosome sets of the tetrads, two of them containing three normal- sized chromosomes and the remaining two having two normal-sized and two half- sized ones. These studied plants were all fertile. Examination of somatic chromosome patterns of the progenies originating from the X/sub 2/ plants heterozygous for one fragmented chromosome revealed the three expected chromosome patterns, i.e., 2n =6, 2n =7, 2n =8. X/sub 2/ plants with 2n =8 were homozygous for the fragmented chromosome, and had a completely regular meiosis with two large and two small bivalents during first metaphase and a regular pairing and separation during the second division. Consequently they gave rise to a fertile strain with a constart chromosome pattern. The origin of the aneuploidy and endonuclear polyploidy of material with diffuse centromeres was discussed in relation to the survival of the fragmented chromosomes in L. purpurea. The survival of broken chromosomes through consecutive generations thus gives an explanation of the occurrence of aneuploid chromosome numbers in material with diffuse centromeres. However, no interpretation of the phenomenon causing the survival of the fragments was provided by this study, since sufficient knowledge about the nature of the diffuse or nonlocalized centromeres is unavailable. (BBB)« less

Discovery of the youngest sex chromosomes reveals first case of convergent co-option of ancestral autosomes in turtles.

PubMed

Montiel, E E; Badenhorst, D; Tamplin, J; Burke, R L; Valenzuela, N

2017-02-01

Most turtle species possess temperature-dependent sex determination (TSD), but genotypic sex determination (GSD) has evolved multiple times independently from the TSD ancestral condition. GSD in animals typically involves sex chromosomes, yet the sex chromosome system of only 9 out of 18 known GSD turtles has been characterized. Here, we combine comparative genome hybridization (CGH) and BAC clone fluorescent in situ hybridization (BAC FISH) to identify a macro-chromosome XX/XY system in the GSD wood turtle Glyptemys insculpta (GIN), the youngest known sex chromosomes in chelonians (8-20 My old). Comparative analyses show that GIN-X/Y is homologous to chromosome 4 of Chrysemys picta (CPI) painted turtles, chromosome 5 of Gallus gallus chicken, and thus to the X/Y sex chromosomes of Siebenrockiella crassicollis black marsh turtles. We tentatively assign the gene content of the mapped BACs from CPI chromosome 4 (CPI-4) to GIN-X/Y. Chromosomal rearrangements were detected in G. insculpta sex chromosome pair that co-localize with the male-specific region of GIN-Y and encompass a gene involved in sexual development (Wt1-a putative master gene in TSD turtles). Such inversions may have mediated the divergence of G. insculpta sex chromosome pair and facilitated GSD evolution in this turtle. Our results illuminate the structure, origin, and evolution of sex chromosomes in G. insculpta and reveal the first case of convergent co-option of an autosomal pair as sex chromosomes within chelonians.

Chromosome Evolution in Connection with Repetitive Sequences and Epigenetics in Plants

PubMed Central

Li, Shu-Fen; Su, Ting; Cheng, Guang-Qian; Wang, Bing-Xiao; Li, Xu; Deng, Chuan-Liang; Gao, Wu-Jun

2017-01-01

Chromosome evolution is a fundamental aspect of evolutionary biology. The evolution of chromosome size, structure and shape, number, and the change in DNA composition suggest the high plasticity of nuclear genomes at the chromosomal level. Repetitive DNA sequences, which represent a conspicuous fraction of every eukaryotic genome, particularly in plants, are found to be tightly linked with plant chromosome evolution. Different classes of repetitive sequences have distinct distribution patterns on the chromosomes. Mounting evidence shows that repetitive sequences may play multiple generative roles in shaping the chromosome karyotypes in plants. Furthermore, recent development in our understanding of the repetitive sequences and plant chromosome evolution has elucidated the involvement of a spectrum of epigenetic modification. In this review, we focused on the recent evidence relating to the distribution pattern of repetitive sequences in plant chromosomes and highlighted their potential relevance to chromosome evolution in plants. We also discussed the possible connections between evolution and epigenetic alterations in chromosome structure and repatterning, such as heterochromatin formation, centromere function, and epigenetic-associated transposable element inactivation. PMID:29064432

Engineering of Systematic Elimination of a Targeted Chromosome in Human Cells.

PubMed

Sato, Hiroshi; Kato, Hiroki; Yamaza, Haruyoshi; Masuda, Keiji; Nguyen, Huong Thi Nguyen; Pham, Thanh Thi Mai; Han, Xu; Hirofuji, Yuta; Nonaka, Kazuaki

2017-01-01

Embryonic trisomy leads to abortion or congenital genetic disorders in humans. The most common autosomal chromosome abnormalities are trisomy of chromosomes 13, 18, and 21. Although alteration of gene dosage is thought to contribute to disorders caused by extra copies of chromosomes, genes associated with specific disease phenotypes remain unclear. To generate a normal cell from a trisomic cell as a means of etiological analysis or candidate therapy for trisomy syndromes, we developed a system to eliminate a targeted chromosome from human cells. Chromosome 21 was targeted by integration of a DNA cassette in HeLa cells that harbored three copies of chromosome 21. The DNA cassette included two inverted loxP sites and a herpes simplex virus thymidine kinase (HSV-tk) gene. This system causes missegregation of chromosome 21 after expression of Cre recombinase and subsequently enables the selection of cells lacking the chromosome by culturing in a medium that includes ganciclovir (GCV). Cells harboring only two copies of chromosome 21 were efficiently induced by transfection of a Cre expression vector, indicating that this approach is useful for eliminating a targeted chromosome.

Frequencies of occurrence of all human chromosomes in micronuclei from normal and 5-azacytidine-treated lymphocytes as revealed by chromosome painting.

PubMed

Fauth, E; Scherthan, H; Zankl, H

1998-05-01

Chromosome painting with library DNA probes specific for all human chromosomes was used to study the chromosomal content of micronuclei (MN) in normal and 5-azacytidine (5-aza-C)-treated lymphocyte cultures. More than 60,000 normal lymphocytes were screened for associated MN after in situ hybridization. At least 50 MN were scored for each probe. With the exception of chromosomes 12 and 19, which did not occur in MN, all other chromosomes were detected in MN at frequencies varying from 1 to 11.5%. Treatment of lymphocyte cultures with 5-aza-C induced preferential exclusion of chromosomes 1 (34%), 9 (32%) and 16 (20%) material in MN, whereas chromosome 8, 10, 12-15 and 21 material was not detected in MN. The results obtained from normal lymphocytes allow for the first time an estimation of the frequency of occurrence of all chromosomes in spontaneously occurring MN in human cells. Data derived from 5-aza-C-treated lymphocytes are furthermore consistent with the view that undermethylation of heterochromatin may be associated with loss of specific chromosomes at metaphase.

Specific end-to-end attachment of chromosomes in Ornithogalum virens.

PubMed

Ashley, T

1979-08-01

C-banding of nonhomologous chromosomes in haploid generative nuclei of Ornithogalum virens (n = 3) reveals a high degree of specificity with respect to end-to-end connexions. The centromeric end of chromosome 2 preferentially associates with the centromeric end of chromosome 3 and the telomeric end of chromosome 3 associates preferentially with the telomeric end of chromosome 1. This same association of nonhomologous chromosomes persists in prophase nuclei of diploid root tips. In addition, the telomeric ends of the 2 chromosome 2s are connected to one another as are the centromeric ends of the chromosome 1s. This results in a ring of chromosomes in which homologues lie opposite one another. Centromeric ends lie on one side of the nucleus and telomeric ends on the other. It is proposed that this specific association of chromosome ends reflects an order which was probably established at the preceding anaphase or telophase and which persists throughout interphase. The suggestion is made that the proximity of homologous ends and consequently homologous alignment may facilitate initiation of pairing at meiosis.

Biological dosimetry by interphase chromosome painting

NASA Technical Reports Server (NTRS)

Durante, M.; George, K.; Yang, T. C.

1996-01-01

Both fluorescence in situ hybridization of metaphase spreads with whole-chromosome probes and premature chromosome condensation in interphase nuclei have been used in the past to estimate the radiation dose to lymphocytes. We combined these techniques to evaluate the feasibility of using painted interphase chromosomes for biodosimetry. Human peripheral lymphocytes were exposed to gamma rays and fused to mitotic Chinese hamster cells either immediately after irradiation or after 8 h incubation at 37 degrees C. Interphase or metaphase human chromosomes were hybridized with a composite probe specific for human chromosomes 3 and 4. The dose-response curve for fragment induction immediately after irradiation was linear; these results reflected breakage frequency in the total genome in terms of DNA content per chromosome. At 8 h after irradiation, the dose-response curve for chromosome interchanges, the prevalent aberration in interphase chromosomes, was linear-quadratic and similar to that observed for metaphase chromosomes. These results suggest that painting prematurely condensed chromosomes can be useful for biological dosimetry when blood samples are available shortly after the exposure, or when interphase cells are to be scored instead of mitotic cells.

Acentric chromosome ends are prone to fusion with functional chromosome ends through a homology-directed rearrangement

PubMed Central

Ohno, Yuko; Ogiyama, Yuki; Kubota, Yoshino; Kubo, Takuya; Ishii, Kojiro

2016-01-01

The centromeres of many eukaryotic chromosomes are established epigenetically on potentially variable tandem repeats; hence, these chromosomes are at risk of being acentric. We reported previously that artificially created acentric chromosomes in the fission yeast Schizosaccharomyces pombe can be rescued by end-to-end fusion with functional chromosomes. Here, we show that most acentric/functional chromosome fusion events in S. pombe cells harbouring an acentric chromosome I differed from the non-homologous end-joining-mediated rearrangements that result in deleterious dicentric fusions in normal cells, and were elicited by a previously unidentified homologous recombination (HR) event between chromosome end-associated sequences. The subtelomere repeats associated with the non-fusogenic ends were also destabilized in the surviving cells, suggesting a causal link between general subtelomere destabilization and acentric/functional chromosome fusion. A mutational analysis indicated that a non-canonical HR pathway was involved in the rearrangement. These findings are indicative of a latent mechanism that conditionally induces general subtelomere instability, presumably in the face of accidental centromere loss events, resulting in rescue of the fatal acentric chromosomes by interchromosomal HR. PMID:26433224

Biological dosimetry by interphase chromosome painting.

PubMed

Durante, M; George, K; Yang, T C

1996-01-01

Both fluorescence in situ hybridization of metaphase spreads with whole-chromosome probes and premature chromosome condensation in interphase nuclei have been used in the past to estimate the radiation dose to lymphocytes. We combined these techniques to evaluate the feasibility of using painted interphase chromosomes for biodosimetry. Human peripheral lymphocytes were exposed to gamma rays and fused to mitotic Chinese hamster cells either immediately after irradiation or after 8 h incubation at 37 degrees C. Interphase or metaphase human chromosomes were hybridized with a composite probe specific for human chromosomes 3 and 4. The dose-response curve for fragment induction immediately after irradiation was linear; these results reflected breakage frequency in the total genome in terms of DNA content per chromosome. At 8 h after irradiation, the dose-response curve for chromosome interchanges, the prevalent aberration in interphase chromosomes, was linear-quadratic and similar to that observed for metaphase chromosomes. These results suggest that painting prematurely condensed chromosomes can be useful for biological dosimetry when blood samples are available shortly after the exposure, or when interphase cells are to be scored instead of mitotic cells.

B-chromosome systems in the greater glider, Petauroides volans (Marsupialia: Pseudocheiridae). II. Investigation of B-chromosome DNA sequences isolated by micromanipulation and PCR.

PubMed

McQuade, L R; Hill, R J; Francis, D

1994-01-01

B chromosomes, despite their common occurrence throughout the animal and plant kingdoms, have not been investigated extensively at the molecular level. While the majority of B chromosomes occurring in animals have been described as heterochromatic, only a few researchers have examined the DNA of these chromosomes beyond this gross cytological level. This is the case in the largest of the gliding marsupial possums, the greater glider, Petauroides volans. To examine the molecular composition and localization of B-chromosome DNA sequences in P. volans, a combination of micromanipulation and the polymerase chain reaction was used in this study to isolate and then amplify the DNA of the B chromosomes. Localization of the isolated B-chromosome sequences to metaphase chromosomes was investigated using fluorescence in situ hybridization. The B chromosomes in this species are shown to be composed of a heterogeneous mixture of sequences, some of which are unique to the B chromosomes, while others exhibit homology to the centromeric regions of the autosomal complement.

Chromosome Banding in Amphibia. XXXVI. Multimorphic Sex Chromosomes and an Enigmatic Sex Determination in Eleutherodactylus johnstonei (Anura, Eleutherodactylidae).

PubMed

Schmid, Michael; Steinlein, Claus

2018-01-01

A detailed cytogenetic study on the leaf litter frog Eleutherodactylus johnstonei from 14 different Caribbean islands and the mainlands of Venezuela and Guyana revealed the existence of multimorphic XY♂/XX♀ sex chromosomes 14. Their male sex determination and development depends either on the presence of 2 telocentric chromosomes 14 (XtYt), or on 1 submetacentric chromosome 14 (Xsm) plus 1 telocentric chromosome 14 (Yt), or on the presence of 2 submetacentric chromosomes 14 (XsmYsm). The female sex determination and development requires either the presence of 2 telocentric chromosomes 14 (XtXt) or 2 submetacentric chromosomes 14 (XsmXsm). In all individuals analyzed, the sex chromosomes 14 carry a prominent nucleolus organizer region in their long arms. An explanation is given for the origin of the (XtYt)♂, (XsmYt)♂, (XsmYsm)♂, (XtXt)♀, and (XsmXsm)♀ in the different populations of E. johnstonei. Furthermore, the present study gives detailed data on the chromosome banding patterns, in situ hybridization experiments, and the genome size of E. johnstonei. © 2018 S. Karger AG, Basel.

The Chromosome Microdissection and Microcloning Technique.

PubMed

Zhang, Ying-Xin; Deng, Chuan-Liang; Hu, Zan-Min

2016-01-01

Chromosome microdissection followed by microcloning is an efficient tool combining cytogenetics and molecular genetics that can be used for the construction of the high density molecular marker linkage map and fine physical map, the generation of probes for chromosome painting, and the localization and cloning of important genes. Here, we describe a modified technique to microdissect a single chromosome, paint individual chromosomes, and construct single-chromosome DNA libraries.

A cytogenetic view of sex chromosome evolution in plants.

PubMed

Armstrong, S J; Filatov, D A

2008-01-01

The recent origin of sex chromosomes in plant species provides an opportunity to study the early stages of sex chromosome evolution. This review focuses on the cytogenetic aspects of the analysis of sex chromosome evolution in plants and in particular, on the best-studied case, the sex chromosomes in Silene latifolia. We discuss the emerging picture of sex chromosome evolution in plants and the further work that is required to gain better understanding of the similarities and differences between the trends in animal and plant sex chromosome evolution. Similar to mammals, suppression of recombination between the X and Y in S. latifolia species has occurred in several steps, however there is little evidence that inversions on the S. latifolia Y chromosome have played a role in cessation of X/Y recombination. Secondly, in S. latifolia there is a lack of evidence for genetic degeneration of the Y chromosome, unlike the events documented in mammalian sex chromosomes. The insufficient number of genes isolated from this and other plant sex chromosomes does not allow us to generalize whether the trends revealed on S. latifolia Y chromosome are general for other dioecious plants. Isolation of more plant sex-linked genes and their cytogenetic mapping with fluorescent in situ hybridisation (FISH) will ultimately lead to a much better understanding of the processes driving sex chromosome evolution in plants. 2008 S. Karger AG, Basel

Effect of met-enkephalin on chromosomal aberrations in the lymphocytes of the peripheral blood of patients with multiple sclerosis.

PubMed

Rakanović-Todić, Maida; Burnazović-Ristić, Lejla; Ibrulj, Slavka; Mulbegović, Nedžad

2014-05-01

Endogenious opiod met-enkephalin throughout previous research manifested cytoprotective and anti-inflammatory effects. Previous research suggests that met-enkephalin has cytogenetic effects. Reducement in the frequency of structural chromosome aberrations as well as a suppressive effect on lymphocyte cell cycle is found. It also reduces apoptosis in the blood samples of the patients with immune-mediated diseases. Met-enkephalin exerts immunomodulatory properties and induces stabilization of the clinical condition in patients with multiple Sclerosis (MS). The goal of the present research was to evaluate met-enkephalin in vitro effects on the number and type of chromosome aberrations in the peripheral blood lymphocytes of patients with MS. Our research detected disappearance of ring chromosomes and chromosome fragmentations in the cultures of the peripheral blood lymphocytes treated with met-enkephalin (1.2 μg/mL). However, this research did not detect any significant effects of met-enkephalin on the reduction of structural chromosome aberrations and disappearance of dicentric chromosomes. Chromosomes with the greatest percent of inclusion in chromosome aberrations were noted as: chromosome 1, chromosome 2 and chromosome 9. Additionally, we confirmed chromosome 14 as the most frequently included in translocations. Furthermore, met-enkephalin effects on the increase of the numerical aberrations in both concentrations applied were detected. Those findings should be interpreted cautiously and more research in this field should be conducted.

Identification of the linkage group of the Z sex chromosomes of the sand lizard (Lacerta agilis, Lacertidae) and elucidation of karyotype evolution in lacertid lizards.

PubMed

Srikulnath, Kornsorn; Matsubara, Kazumi; Uno, Yoshinobu; Nishida, Chizuko; Olsson, Mats; Matsuda, Yoichi

2014-12-01

The sand lizard (Lacerta agilis, Lacertidae) has a chromosome number of 2n = 38, with 17 pairs of acrocentric chromosomes, one pair of microchromosomes, a large acrocentric Z chromosome, and a micro-W chromosome. To investigate the process of karyotype evolution in L. agilis, we performed chromosome banding and fluorescent in situ hybridization for gene mapping and constructed a cytogenetic map with 86 functional genes. Chromosome banding revealed that the Z chromosome is the fifth largest chromosome. The cytogenetic map revealed homology of the L. agilis Z chromosome with chicken chromosomes 6 and 9. Comparison of the L. agilis cytogenetic map with those of four Toxicofera species with many microchromosomes (Elaphe quadrivirgata, Varanus salvator macromaculatus, Leiolepis reevesii rubritaeniata, and Anolis carolinensis) showed highly conserved linkage homology of L. agilis chromosomes (LAG) 1, 2, 3, 4, 5(Z), 7, 8, 9, and 10 with macrochromosomes and/or macrochromosome segments of the four Toxicofera species. Most of the genes located on the microchromosomes of Toxicofera were localized to LAG6, small acrocentric chromosomes (LAG11-18), and a microchromosome (LAG19) in L. agilis. These results suggest that the L. agilis karyotype resulted from frequent fusions of microchromosomes, which occurred in the ancestral karyotype of Toxicofera and led to the disappearance of microchromosomes and the appearance of many small macrochromosomes.