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Sample records for eutherian sex chromosomes

  1. Meiotic Pairing and Segregation of Achiasmate Sex Chromosomes in Eutherian Mammals: The Role of SYCP3 Protein

    PubMed Central

    de la Fuente, Roberto; Parra, María Teresa; Viera, Alberto; Calvente, Adela; Gómez, Rocío; Suja, José Ángel; Rufas, Julio S; Page, Jesús

    2007-01-01

    In most eutherian mammals, sex chromosomes synapse and recombine during male meiosis in a small region called pseudoautosomal region. However in some species sex chromosomes do not synapse, and how these chromosomes manage to ensure their proper segregation is under discussion. Here we present a study of the meiotic structure and behavior of sex chromosomes in one of these species, the Mongolian gerbil (Meriones unguiculatus). We have analyzed the location of synaptonemal complex (SC) proteins SYCP1 and SYCP3, as well as three proteins involved in the process of meiotic recombination (RAD51, MLH1, and γ-H2AX). Our results show that although X and Y chromosomes are associated at pachytene and form a sex body, their axial elements (AEs) do not contact, and they never assemble a SC central element. Furthermore, MLH1 is not detected on the AEs of the sex chromosomes, indicating the absence of reciprocal recombination. At diplotene the organization of sex chromosomes changes strikingly, their AEs associate end to end, and SYCP3 forms an intricate network that occupies the Y chromosome and the distal region of the X chromosome long arm. Both the association of sex chromosomes and the SYCP3 structure are maintained until metaphase I. In anaphase I sex chromosomes migrate to opposite poles, but SYCP3 filaments connecting both chromosomes are observed. Hence, one can assume that SYCP3 modifications detected from diplotene onwards are correlated with the maintenance of sex chromosome association. These results demonstrate that some components of the SC may participate in the segregation of achiasmate sex chromosomes in eutherian mammals. PMID:17983272

  2. Reconstruction and evolutionary history of eutherian chromosomes.

    PubMed

    Kim, Jaebum; Farré, Marta; Auvil, Loretta; Capitanu, Boris; Larkin, Denis M; Ma, Jian; Lewin, Harris A

    2017-07-03

    Whole-genome assemblies of 19 placental mammals and two outgroup species were used to reconstruct the order and orientation of syntenic fragments in chromosomes of the eutherian ancestor and six other descendant ancestors leading to human. For ancestral chromosome reconstructions, we developed an algorithm (DESCHRAMBLER) that probabilistically determines the adjacencies of syntenic fragments using chromosome-scale and fragmented genome assemblies. The reconstructed chromosomes of the eutherian, boreoeutherian, and euarchontoglires ancestor each included >80% of the entire length of the human genome, whereas reconstructed chromosomes of the most recent common ancestor of simians, catarrhini, great apes, and humans and chimpanzees included >90% of human genome sequence. These high-coverage reconstructions permitted reliable identification of chromosomal rearrangements over ∼105 My of eutherian evolution. Orangutan was found to have eight chromosomes that were completely conserved in homologous sequence order and orientation with the eutherian ancestor, the largest number for any species. Ruminant artiodactyls had the highest frequency of intrachromosomal rearrangements, and interchromosomal rearrangements dominated in murid rodents. A total of 162 chromosomal breakpoints in evolution of the eutherian ancestral genome to the human genome were identified; however, the rate of rearrangements was significantly lower (0.80/My) during the first ∼60 My of eutherian evolution, then increased to greater than 2.0/My along the five primate lineages studied. Our results significantly expand knowledge of eutherian genome evolution and will facilitate greater understanding of the role of chromosome rearrangements in adaptation, speciation, and the etiology of inherited and spontaneously occurring diseases.

  3. A chromosome painting test of the basal eutherian karyotype.

    PubMed

    Svartman, Marta; Stone, Gary; Page, John E; Stanyon, Roscoe

    2004-01-01

    We studied the chromosomes of an Afrotherian species, the short-eared elephant shrew Macroscelides proboscideus with traditional banding techniques and mapped the homology to human chromosomes by in-situ hybridization of human chromosome paints. Here we present for the first time the karyotype of this species, including banding patterns. The chromosome painting allowed us to test various hypotheses of the ancestral Eutherian karyotype, the validity of the radical taxonomic assemblage known as Afrotheria and the phylogenetic position of the elephant shrew within the Afrotheria. Current hypotheses concerning the Eutherian ancestral karyotype include diploid numbers ranging from 2n = 44 to 50 while molecular studies have proposed a new superordinal grouping of extant Eutherians. In particular, the Afrotheria is hotly debated, as it appears to be an odd mixture of species from Ungulata, Tubulidentata, Macroscelidea and Lipotyphla, which have no apparent morphological traits to unite them. The hybridization pattern delimited a total of 37 segments in the elephant shrew genome and revealed 21 different associations of human chromosome segments. Associations 1/19 and 5/21 link all Afrotheria so far studied and support the Afrotheria assemblage. Associations 2/8, 3/20, and 10/17 strongly link aardvarks and elephant shrews after the divergence of the line leading to elephants. The most likely ancestral Eutherian karyotype would be 2n = 48 chromosomes. However, the lack of comparative chromosome painting data between Eutherians and an appropriate outgroup is a severe limitation on attempts to delineate the ancestral genome of Eutherians. Current attempts lack legitimacy until this situation is corrected.

  4. Meiotic sex chromosome inactivation in the marsupial Monodelphis domestica.

    PubMed

    Hornecker, Jacey L; Samollow, Paul B; Robinson, Edward S; Vandeberg, John L; McCarrey, John R

    2007-11-01

    In eutherian mammals, the X and Y chromosomes undergo meiotic sex chromosome inactivation (MSCI) during spermatogenesis in males. However, following fertilization, both the paternally (Xp) and maternally (Xm) inherited X chromosomes are active in the inner cell mass of the female blastocyst, and then random inactivation of one X chromosome occurs in each cell, leading to a mosaic pattern of X-chromosome activity in adult female tissues. In contrast, marsupial females show a nonrandom pattern of X chromosome activity, with repression of the Xp in all somatic tissues. Here, we show that MSCI also occurs during spermatogenesis in marsupials in a manner similar to, but more stable than that in eutherians. These findings support the suggestion that MSCI may have provided the basis for an early dosage compensation mechanism in mammals based solely on gametogenic events, and that random X-chromosome inactivation during embryogenesis may have evolved subsequently in eutherian mammals.

  5. Abnormal human sex chromosome constitutions

    SciTech Connect

    1993-12-31

    Chapter 22, discusses abnormal human sex chromosome constitution. Aneuploidy of X chromosomes with a female phenotype, sex chromosome aneuploidy with a male phenotype, and various abnormalities in X chromosome behavior are described. 31 refs., 2 figs.

  6. Sex Chromosome Drive

    PubMed Central

    Helleu, Quentin; Gérard, Pierre R.; Montchamp-Moreau, Catherine

    2015-01-01

    Sex chromosome drivers are selfish elements that subvert Mendel's first law of segregation and therefore are overrepresented among the products of meiosis. The sex-biased progeny produced then fuels an extended genetic conflict between the driver and the rest of the genome. Many examples of sex chromosome drive are known, but the occurrence of this phenomenon is probably largely underestimated because of the difficulty to detect it. Remarkably, nearly all sex chromosome drivers are found in two clades, Rodentia and Diptera. Although very little is known about the molecular and cellular mechanisms of drive, epigenetic processes such as chromatin regulation could be involved in many instances. Yet, its evolutionary consequences are far-reaching, from the evolution of mating systems and sex determination to the emergence of new species. PMID:25524548

  7. [Sex chromosomes and meiosis].

    PubMed

    Guichaoua, M-R; Geoffroy-Siraudin, C; Tassistro, V; Ghalamoun-Slaimi, R; Perrin, J; Metzler-Guillemain, C

    2009-01-01

    Sex chromosome behaviour fundamentally differs between male and female meiosis. In oocyte, X chromosomes synapse giving a XX bivalent which is not recognizable in their morphology and behaviour from autosomal bivalents. In human male, X and Y chromosomes differ from one another in their morphology and their genetic content, leading to a limited pairing and preventing genetic recombination, excepted in homologous region PAR1. During pachytene stage of the first meiotic prophase, X and Y chromosomes undergo a progressive condensation and form a transcriptionally silenced peripheral XY body. The condensation of the XY bivalent during pachytene stage led us to describe four pachytene substages and to localize the pachytene checkpoint between substages 2 and 3. We also defined the pachytene index (PI=P1+P2/P1+P2+P3+P4) which is always less than 0.50 in normal meiosis. XY body undergoes decondensation at diplotene stage, but transcriptional inactivation of the two sex chromosomes or Meiotic Sex Chromosome Inactivation (MSCI) persists through to the end of spermatogenesis. Sex chromosome inactivation involves several proteins, some of them were now identified. Two isoforms of the HP1 protein, HP1beta and HP1gamma, are involved in the facultative heterochromatinization of the XY body, but the initiation of this process involves the phosphorylation of the protein H2AX by the kinase ATR whose recruitment depends on BRCA1. Extensive researches on the inactivation of the sex chromosomes during male meiosis will allow to a better understanding of some male infertilities.

  8. Meiotic sex chromosome inactivation.

    PubMed

    Turner, James M A

    2007-05-01

    X chromosome inactivation is most commonly studied in the context of female mammalian development, where it performs an essential role in dosage compensation. However, another form of X-inactivation takes place in the male, during spermatogenesis, as germ cells enter meiosis. This second form of X-inactivation, called meiotic sex chromosome inactivation (MSCI) has emerged as a novel paradigm for studying the epigenetic regulation of gene expression. New studies have revealed that MSCI is a special example of a more general mechanism called meiotic silencing of unsynapsed chromatin (MSUC), which silences chromosomes that fail to pair with their homologous partners and, in doing so, may protect against aneuploidy in subsequent generations. Furthermore, failure in MSCI is emerging as an important etiological factor in meiotic sterility.

  9. Did sex chromosome turnover promote divergence of the major mammal groups?

    PubMed Central

    2016-01-01

    Comparative mapping and sequencing show that turnover of sex determining genes and chromosomes, and sex chromosome rearrangements, accompany speciation in many vertebrates. Here I review the evidence and propose that the evolution of therian mammals was precipitated by evolution of the male‐determining SRY gene, defining a novel XY sex chromosome pair, and interposing a reproductive barrier with the ancestral population of synapsid reptiles 190 million years ago (MYA). Divergence was reinforced by multiple translocations in monotreme sex chromosomes, the first of which supplied a novel sex determining gene. A sex chromosome‐autosome fusion may have separated eutherians (placental mammals) from marsupials 160 MYA. Another burst of sex chromosome change and speciation is occurring in rodents, precipitated by the degradation of the Y. And although primates have a more stable Y chromosome, it may be just a matter of time before the same fate overtakes our own lineage. Also watch the video abstract. PMID:27334831

  10. Reciprocal chromosome painting among human, aardvark, and elephant (superorder Afrotheria) reveals the likely eutherian ancestral karyotype.

    PubMed

    Yang, F; Alkalaeva, E Z; Perelman, P L; Pardini, A T; Harrison, W R; O'Brien, P C M; Fu, B; Graphodatsky, A S; Ferguson-Smith, M A; Robinson, T J

    2003-02-04

    The Afrotheria, a supraordinal grouping of mammals whose radiation is rooted in Africa, is strongly supported by DNA sequence data but not by their disparate anatomical features. We have used flow-sorted human, aardvark, and African elephant chromosome painting probes and applied reciprocal painting schemes to representatives of two of the Afrotherian orders, the Tubulidentata (aardvark) and Proboscidea (elephants), in an attempt to shed additional light on the evolutionary affinities of this enigmatic group of mammals. Although we have not yet found any unique cytogenetic signatures that support the monophyly of the Afrotheria, embedded within the aardvark genome we find the strongest evidence yet of a mammalian ancestral karyotype comprising 2n = 44. This karyotype includes nine chromosomes that show complete conserved synteny to those of man, six that show conservation as single chromosome arms or blocks in the human karyotype but that occur on two different chromosomes in the ancestor, and seven neighbor-joining combinations (i.e., the synteny is maintained in the majority of species of the orders studied so far, but which corresponds to two chromosomes in humans). The comparative chromosome maps presented between human and these Afrotherian species provide further insight into mammalian genome organization and comparative genomic data for the Afrotheria, one of the four major evolutionary clades postulated for the Eutheria.

  11. 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

  12. Numerous transitions of sex chromosomes in Diptera.

    PubMed

    Vicoso, Beatriz; Bachtrog, Doris

    2015-04-01

    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.

  13. First description of multivalent ring structures in eutherian mammalian meiosis: new chromosomal characterization of Cormura brevirostris (Emballonuridae, Chiroptera).

    PubMed

    de Araújo, Ramon Everton Ferreira; Nagamachi, Cleusa Yoshiko; da Costa, Marlyson Jeremias Rodrigues; Noronha, Renata Coelho Rodrigues; Rodrigues, Luís Reginaldo Ribeiro; Pieczarka, Julio César

    2016-08-01

    Twelve specimens of the bat Cormura brevirostris (Emballonuridae: Chiroptera) were collected from four localities in the Brazilian Amazon region and analyzed by classical and molecular cytogenetics. The diploid number and autosomal fundamental number were as previously reported (2n = 22 and FNa = 40, respectively). Fluorescence in situ hybridization using rDNA probes and silver nitrate technique demonstrated the presence of two NOR sites and the presence of internal telomeric sequences at pericentromeric regions of all chromosomes with exception of Y. Based on meiotic studies and chromosome banding we suggest that the sex chromosome pair of C. brevirostris was equivocally identified as it appears in the literature. Meiotic analysis demonstrated that at diplotene-diakinesis the cells had a ring conformation involving four chromosome pairs. This suggests the occurrence of multiple reciprocal translocations among these chromosomes, which is a very rare phenomenon in vertebrates, and has never been described in Eutheria.

  14. Sex determination in marsupials: evidence for a marsupial-eutherian dichotomy.

    PubMed

    Renfree, M B; Short, R V

    1988-12-01

    In this paper, we review briefly the current state of knowledge about sexual differentiation in eutherian mammals, and then describe the situation in detail in two marsupial species: the North American opossum and the tammar wallaby. The conventional explanation for the genesis of all male somatic sexual dimorphisms in mammals is that they are a consequence of the systemic action of testicular hormones. In the absence of testes, the embryo will develop a female phenotype. We present evidence for the tammar wallaby that calls into question the universal applicability of this hormonal theory of mammalian sexual differentiation. We have shown that extensive somatic sexual dimorphisms precede by many days the first morphological evidence of testicular formation, which does not occur until around the third day of pouch life. Male foetuses, and pouch young on the day of birth, already have a well-developed gubernaculum and processus vaginalis, paired scrotal anlagen, and a complete absence of mammary anlagen, whereas female foetuses and newborn pouch young have a poorly developed gubernaculum and processus vaginalis, no scrotal anlagen, and well-developed mammary anlagen. Because it seems unlikely that the male gonad could begin hormone secretion until after the Sertoli and Leydig cells are developed, our results strongly suggest that some sexually dimorphic somatic characteristics develop autonomously, depending on their genotype rather than the hormonal environment to which they are exposed. We have been able to confirm the hormonal independence of the scrotum, pouch and mammary gland by administering testosterone propionate daily by mouth to female pouch young from the day of birth; although the Wolffian duct was hyperstimulated, there was no sign of scrotal development, or pouch or mammary inhibition. When male pouch young were treated with oestradiol benzoate in a similar fashion, there was hyperstimulation of the Müllerian duct and inhibition of testicular

  15. Sex chromosome abnormalities and psychiatric diseases

    PubMed Central

    Zhang, Xinzhu; Yang, Jian; Li, Yuhong; Ma, Xin; Li, Rena

    2017-01-01

    Excesses of sex chromosome abnormalities in patients with psychiatric diseases have recently been observed. It remains unclear whether sex chromosome abnormalities are related to sex differences in some psychiatric diseases. While studies showed evidence of susceptibility loci over many sex chromosomal regions related to various mental diseases, others demonstrated that the sex chromosome aneuploidies may be the key to exploring the pathogenesis of psychiatric disease. In this review, we will outline the current evidence on the interaction of sex chromosome abnormalities with schizophrenia, autism, ADHD and mood disorders. PMID:27992373

  16. Conservation of sex chromosomes in lacertid lizards.

    PubMed

    Rovatsos, Michail; Vukić, Jasna; Altmanová, Marie; Johnson Pokorná, Martina; Moravec, Jiří; Kratochvíl, Lukáš

    2016-07-01

    Sex chromosomes are believed to be stable in endotherms, but young and evolutionary unstable in most ectothermic vertebrates. Within lacertids, the widely radiated lizard group, sex chromosomes have been reported to vary in morphology and heterochromatinization, which may suggest turnovers during the evolution of the group. We compared the partial gene content of the Z-specific part of sex chromosomes across major lineages of lacertids and discovered a strong evolutionary stability of sex chromosomes. We can conclude that the common ancestor of lacertids, living around 70 million years ago (Mya), already had the same highly differentiated sex chromosomes. Molecular data demonstrating an evolutionary conservation of sex chromosomes have also been documented for iguanas and caenophidian snakes. It seems that differences in the evolutionary conservation of sex chromosomes in vertebrates do not reflect the distinction between endotherms and ectotherms, but rather between amniotes and anamniotes, or generally, the differences in the life history of particular lineages.

  17. B chromosomes and sex in animals.

    PubMed

    Camacho, J P M; Schmid, M; Cabrero, J

    2011-01-01

    Supernumerary (B) chromosomes are dispensable elements found in many eukaryote genomes in addition to standard (A) chromosomes. In many respects, B chromosomes resemble sex chromosomes, so that a common ancestry for them has frequently been suggested. For instance, B chromosomes in grasshoppers, and other insects, show a pycnotic cycle of condensation-decondensation during meiosis remarkably similar to that of the X chromosome. In some cases, B chromosome size is even very similar to that of the X chromosome. These resemblances have led to suggest the X as the B ancestor in many cases. In addition, sex chromosome origin from B chromosomes has also been suggested. In this article, we review the existing evidence for both evolutionary pathways, as well as sex differences for B frequency at adult and embryo progeny levels, B chromosome effects or B chromosome transmission. In addition, we review cases found in the literature showing sex-ratio distortion associated with B chromosome presence, the most extreme case being the paternal sex ratio (PSR) chromosomes in some Hymenoptera. We finally analyse the possibility of B chromosome regularisation within the host genome and, as a consequence of it, whether B chromosomes can become regular members of the host genome.

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

    SciTech Connect

    Watson, J.M.; Spencer, J.A.; Graves, J.A.M. ); Riggs, A.D. )

    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 is 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.

  19. Physical mapping of the elephant X chromosome: conservation of gene order over 105 million years.

    PubMed

    Delgado, Claudia Leticia Rodríguez; Waters, Paul D; Gilbert, Clément; Robinson, Terence J; Graves, Jennifer A Marshall

    2009-01-01

    All therian mammals (eutherians and marsupials) have an XX female/XY male sex chromosome system or some variant of it. The X and Y evolved from a homologous pair of autosomes over the 166 million years since therian mammals diverged from monotremes. Comparing the sex chromosomes of eutherians and marsupials defined an ancient X conserved region that is shared between species of these mammalian clades. However, the eutherian X (and the Y) was augmented by a recent addition (XAR) that is autosomal in marsupials. XAR is part of the X in primates, rodents, and artiodactyls (which belong to the eutherian clade Boreoeutheria), but it is uncertain whether XAR is part of the X chromosome in more distantly related eutherian mammals. Here we report on the gene content and order on the X of the elephant (Loxodonta africana)-a representative of Afrotheria, a basal endemic clade of African mammals-and compare these findings to those of other documented eutherian species. A total of 17 genes were mapped to the elephant X chromosome. Our results support the hypothesis that the eutherian X and Y chromosomes were augmented by the addition of autosomal material prior to eutherian radiation. Not only does the elephant X bear the same suite of genes as other eutherian X chromosomes, but gene order appears to have been maintained across 105 million years of evolution, perhaps reflecting strong constraints posed by the eutherian X inactivation system.

  20. Chromosome chains and platypus sex: kinky connections.

    PubMed

    Ashley, Terry

    2005-07-01

    Mammal sex determination depends on an XY chromosome system, a gene for testis development and a means of activating the X chromosome. The duckbill platypus challenges these dogmas.(1,2) Gutzner et al.(1) find no recognizable SRY sequence and question whether the mammalian X was even the original sex chromosome in the platypus. Instead they suggest that the original platypus sex chromosomes were derived from the ZW chromosome system of birds and reptiles. Unraveling the puzzles of sex determination and dosage compensation in the platypus has been complicated by the fact that it has a surplus of sex chromosomes. Rather than a single X and Y chromosome, the male platypus has five Xs and five Ys.

  1. Implications of monotreme and marsupial chromosome evolution on sex determination and differentiation.

    PubMed

    Deakin, Janine E

    2017-04-01

    Studies of chromosomes from monotremes and marsupials endemic to Australasia have provided important insight into the evolution of their genomes as well as uncovering fundamental differences in their sex determination/differentiation pathways. Great advances have been made this century into solving the mystery of the complicated sex chromosome system in monotremes. Monotremes possess multiple different X and Y chromosomes and a candidate sex determining gene has been identified. Even greater advancements have been made for marsupials, with reconstruction of the ancestral karyotype enabling the evolutionary history of marsupial chromosomes to be determined. Furthermore, the study of sex chromosomes in intersex marsupials has afforded insight into differences in the sexual differentiation pathway between marsupials and eutherians, together with experiments showing the insensitivity of the mammary glands, pouch and scrotum to exogenous hormones, led to the hypothesis that there is a gene (or genes) on the X chromosome responsible for the development of either pouch or scrotum. This review highlights the major advancements made towards understanding chromosome evolution and how this has impacted on our understanding of sex determination and differentiation in these interesting mammals.

  2. Sexual maldevelopment and sex reversal, chromosomal causes.

    PubMed

    Magenis, R Ellen

    2006-01-01

    The SRY gene on the Y chromosome is the testis determining factor (TDF). It is therefore the initial male determining factor. However, phenotypic sex determination includes a cascade of genes located on autosomes as well as sex chromosomes. Aberrations of these genes may cause sexual maldevelopment or sex reversal. Abnormalities may include single gene mutations and gene loss or gain-changes may involve only sex organs or may be part of syndromes. These changes may also arise as chromosome abnormalities involving contiguous genes. Eight cases with chromosomal abnormalities involving different causative mechanisms are described herein. The most common cause is nondisjunction, including loss or gain of sex chromosomes. Less common causes are mispairing and crossing over in meiosis, chromosome breaks with repair, nonhomologous pairing due to low copy repeats and crossing over, and translocation (familial or de novo) with segregation. Cases include: [see: text].

  3. Learning Disorders and Sex Chromosome Aberrations.

    ERIC Educational Resources Information Center

    Hier, D. B.; And Others

    1980-01-01

    In a prospective study of 20 adult dyslexic men, no sex chromosome aberrations were detected. A retrospective study of 89 Ss with known sex chromosome aberrations revealed 20 of them to be mentally retarded. Among the 69 Ss of normal intelligence, learning, speech, and attention disorders were frequent. (Author/DLS)

  4. Evolution and conservation of Characidium sex chromosomes.

    PubMed

    Utsunomia, R; Scacchetti, P C; Hermida, M; Fernández-Cebrián, R; Taboada, X; Fernández, C; Bekaert, M; Mendes, N J; Robledo, D; Mank, J E; Taggart, J B; Oliveira, C; Foresti, F; Martínez, P

    2017-10-01

    Fish species exhibit substantial variation in the degree of genetic differentiation between sex chromosome pairs, and therefore offer the opportunity to study the full range of sex chromosome evolution. We used restriction-site associated DNA sequencing (RAD-seq) to study the sex chromosomes of Characidium gomesi, a species with conspicuous heteromorphic ZW/ZZ sex chromosomes. We screened 9863 single-nucleotide polymorphisms (SNPs), corresponding to ~1 marker/100 kb distributed across the genome for sex-linked variation. With this data set, we identified 26 female-specific RAD loci, putatively located on the W chromosome, as well as 148 sex-associated SNPs showing significant differentiation (average FST=0.144) between males and females, and therefore in regions of more recent divergence between the Z and W chromosomes. In addition, we detected 25 RAD loci showing extreme heterozygote deficiency in females but which were in Hardy-Weinberg equilibrium in males, consistent with degeneration of the W chromosome and therefore female hemizygosity. We validated seven female-specific and two sex-associated markers in a larger sample of C. gomesi, of which three localised to the W chromosome, thereby providing useful markers for sexing wild samples. Validated markers were evaluated in other populations and species of the genus Characidium, this exploration suggesting a rapid turnover of W-specific repetitive elements. Together, our analyses point to a complex origin for the sex chromosome of C. gomesi and highlight the utility of RAD-seq for studying the composition and evolution of sex chromosomes systems in wild populations.

  5. Evolution of Sex Chromosomes in Insects

    PubMed Central

    Kaiser, Vera B.; Bachtrog, Doris

    2011-01-01

    Sex chromosomes have many unusual features relative to autosomes. Y (or W) chromosomes lack genetic recombination, are male- (female-) limited, and show an abundance of genetically inert heterochromatic DNA but contain few functional genes. X (or Z) chromosomes also show sex-biased transmission (i.e., X chromosomes show female-biased and Z-chromosomes show male-biased inheritance) and are hemizygous in the heterogametic sex. Their unusual ploidy level and pattern of inheritance imply that sex chromosomes play a unique role in many biological processes and phenomena, including sex determination, epigenetic chromosome-wide regulation of gene expression, the distribution of genes in the genome, genomic conflict, local adaptation, and speciation. The vast diversity of sex chromosome systems in insects—ranging from the classical male heterogametic XY system in Drosophila to ZW systems in Lepidoptera or mobile genes determining sex as found in house flies—implies that insects can serve as unique model systems to study various functional and evolutionary aspects of these different processes. PMID:21047257

  6. Comparative genome maps of the pangolin, hedgehog, sloth, anteater and human revealed by cross-species chromosome painting: further insight into the ancestral karyotype and genome evolution of eutherian mammals.

    PubMed

    Yang, Fengtang; Graphodatsky, Alexander S; Li, Tangliang; Fu, Beiyuan; Dobigny, Gauthier; Wang, Jinghuan; Perelman, Polina L; Serdukova, Natalya A; Su, Weiting; O'Brien, Patricia Cm; Wang, Yingxiang; Ferguson-Smith, Malcolm A; Volobouev, Vitaly; Nie, Wenhui

    2006-01-01

    To better understand the evolution of genome organization of eutherian mammals, comparative maps based on chromosome painting have been constructed between human and representative species of three eutherian orders: Xenarthra, Pholidota, and Eulipotyphla, as well as between representative species of the Carnivora and Pholidota. These maps demonstrate the conservation of such syntenic segment associations as HSA3/21, 4/8, 7/16, 12/22, 14/15 and 16/19 in Eulipotyphla, Pholidota and Xenarthra and thus further consolidate the notion that they form part of the ancestral karyotype of the eutherian mammals. Our study has revealed many potential ancestral syntenic associations of human chromosomal segments that serve to link the families as well as orders within the major superordinial eutherian clades defined by molecular markers. The HSA2/8 and 7/10 associations could be the cytogenetic signatures that unite the Xenarthrans, while the HSA1/19p could be a putative signature that links the Afrotheria and Xenarthra. But caution is required in the interpretation of apparently shared syntenic associations as detailed analyses also show examples of apparent convergent evolution that differ in breakpoints and extent of the involved segments.

  7. Evolutionary stability of sex chromosomes in snakes

    PubMed Central

    Rovatsos, Michail; Vukić, Jasna; Lymberakis, Petros; Kratochvíl, Lukáš

    2015-01-01

    Amniote vertebrates possess various mechanisms of sex determination, but their variability is not equally distributed. The large evolutionary stability of sex chromosomes in viviparous mammals and birds was believed to be connected with their endothermy. However, some ectotherm lineages seem to be comparably conserved in sex determination, but previously there was a lack of molecular evidence to confirm this. Here, we document a stability of sex chromosomes in advanced snakes based on the testing of Z-specificity of genes using quantitative PCR (qPCR) across 37 snake species (our qPCR technique is suitable for molecular sexing in potentially all advanced snakes). We discovered that at least part of sex chromosomes is homologous across all families of caenophidian snakes (Acrochordidae, Xenodermatidae, Pareatidae, Viperidae, Homalopsidae, Colubridae, Elapidae and Lamprophiidae). The emergence of differentiated sex chromosomes can be dated back to about 60 Ma and preceded the extensive diversification of advanced snakes, the group with more than 3000 species. The Z-specific genes of caenophidian snakes are (pseudo)autosomal in the members of the snake families Pythonidae, Xenopeltidae, Boidae, Erycidae and Sanziniidae, as well as in outgroups with differentiated sex chromosomes such as monitor lizards, iguanas and chameleons. Along with iguanas, advanced snakes are therefore another example of ectothermic amniotes with a long-term stability of sex chromosomes comparable with endotherms. PMID:26702042

  8. The tilapias' chromosomes influencing sex determination.

    PubMed

    Cnaani, A

    2013-01-01

    The sex chromosomes of tilapias (family Cichlidae; genera Oreochromis, Sarotherodon and Tilapia) have been studied for over 50 years, which has gained interest from both agricultural and basic scientific perspectives. Several closely related tilapia species which can interbreed have been studied, and it has been repeatedly demonstrated that there is variation within and between species in the chromosomal sex-determination mechanism. Both male and female heterogametic sex-determination systems have been characterized, as well as epistatic and environmental influences on sex determination. Three different linkage groups (LG1, LG3 and LG23) have been identified as sex-associated chromosomes and have been subjected to further cytogenetic research and analyses of the genes located around the sex-determining region. Variation in the genetic and physical characteristics of the sex chromosomes makes tilapias an excellent model system for studying the evolution of vertebrate sex chromosomes. This review summarizes the progress made along 5 decades of research and the current knowledge of the tilapias' sex chromosomes.

  9. Evolutionary stability of sex chromosomes in snakes.

    PubMed

    Rovatsos, Michail; Vukić, Jasna; Lymberakis, Petros; Kratochvíl, Lukáš

    2015-12-22

    Amniote vertebrates possess various mechanisms of sex determination, but their variability is not equally distributed. The large evolutionary stability of sex chromosomes in viviparous mammals and birds was believed to be connected with their endothermy. However, some ectotherm lineages seem to be comparably conserved in sex determination, but previously there was a lack of molecular evidence to confirm this. Here, we document a stability of sex chromosomes in advanced snakes based on the testing of Z-specificity of genes using quantitative PCR (qPCR) across 37 snake species (our qPCR technique is suitable for molecular sexing in potentially all advanced snakes). We discovered that at least part of sex chromosomes is homologous across all families of caenophidian snakes (Acrochordidae, Xenodermatidae, Pareatidae, Viperidae, Homalopsidae, Colubridae, Elapidae and Lamprophiidae). The emergence of differentiated sex chromosomes can be dated back to about 60 Ma and preceded the extensive diversification of advanced snakes, the group with more than 3000 species. The Z-specific genes of caenophidian snakes are (pseudo)autosomal in the members of the snake families Pythonidae, Xenopeltidae, Boidae, Erycidae and Sanziniidae, as well as in outgroups with differentiated sex chromosomes such as monitor lizards, iguanas and chameleons. Along with iguanas, advanced snakes are therefore another example of ectothermic amniotes with a long-term stability of sex chromosomes comparable with endotherms. © 2015 The Author(s).

  10. Sex Determination, Sex Chromosomes, and Karyotype Evolution in Insects.

    PubMed

    Blackmon, Heath; Ross, Laura; Bachtrog, Doris

    2017-01-01

    Insects harbor a tremendous diversity of sex determining mechanisms both within and between groups. For example, in some orders such as Hymenoptera, all members are haplodiploid, whereas Diptera contain species with homomorphic as well as male and female heterogametic sex chromosome systems or paternal genome elimination. We have established a large database on karyotypes and sex chromosomes in insects, containing information on over 13000 species covering 29 orders of insects. This database constitutes a unique starting point to report phylogenetic patterns on the distribution of sex determination mechanisms, sex chromosomes, and karyotypes among insects and allows us to test general theories on the evolutionary dynamics of karyotypes, sex chromosomes, and sex determination systems in a comparative framework. Phylogenetic analysis reveals that male heterogamety is the ancestral mode of sex determination in insects, and transitions to female heterogamety are extremely rare. Many insect orders harbor species with complex sex chromosomes, and gains and losses of the sex-limited chromosome are frequent in some groups. Haplodiploidy originated several times within insects, and parthenogenesis is rare but evolves frequently. Providing a single source to electronically access data previously distributed among more than 500 articles and books will not only accelerate analyses of the assembled data, but also provide a unique resource to guide research on which taxa are likely to be informative to address specific questions, for example, for genome sequencing projects or large-scale comparative studies. © The American Genetic Association 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  11. Independent evolution of transcriptional inactivation on sex chromosomes in birds and mammals.

    PubMed

    Livernois, Alexandra M; Waters, Shafagh A; Deakin, Janine E; Marshall Graves, Jennifer A; Waters, Paul D

    2013-01-01

    X chromosome inactivation in eutherian mammals has been thought to be tightly controlled, as expected from a mechanism that compensates for the different dosage of X-borne genes in XX females and XY males. However, many X genes escape inactivation in humans, inactivation of the X in marsupials is partial, and the unrelated sex chromosomes of monotreme mammals have incomplete and gene-specific inactivation of X-linked genes. The bird ZW sex chromosome system represents a third independently evolved amniote sex chromosome system with dosage compensation, albeit partial and gene-specific, via an unknown mechanism (i.e. upregulation of the single Z in females, down regulation of one or both Zs in males, or a combination). We used RNA-fluorescent in situ hybridization (RNA-FISH) to demonstrate, on individual fibroblast cells, inactivation of 11 genes on the chicken Z and 28 genes on the X chromosomes of platypus. Each gene displayed a reproducible frequency of 1Z/1X-active and 2Z/2X-active cells in the homogametic sex. Our results indicate that the probability of inactivation is controlled on a gene-by-gene basis (or small domains) on the chicken Z and platypus X chromosomes. This regulatory mechanism must have been exapted independently to the non-homologous sex chromosomes in birds and mammals in response to an over-expressed Z or X in the homogametic sex, highlighting the universal importance that (at least partial) silencing plays in the evolution on amniote dosage compensation and, therefore, the differentiation of sex chromosomes.

  12. Dosage Compensation of the Sex Chromosomes

    PubMed Central

    Disteche, Christine M.

    2013-01-01

    Differentiated sex chromosomes evolved because of suppressed recombination once sex became genetically controlled. In XX/XY and ZZ/ZW systems, the heterogametic sex became partially aneuploid after degeneration of the Y or W. Often, aneuploidy causes abnormal levels of gene expression throughout the entire genome. Dosage compensation mechanisms evolved to restore balanced expression of the genome. These mechanisms include upregulation of the heterogametic chromosome as well as repression in the homogametic sex. Remarkably, strategies for dosage compensation differ between species. In organisms where more is known about molecular mechanisms of dosage compensation, specific protein complexes containing noncoding RNAs are targeted to the X chromosome. In addition, the dosage-regulated chromosome often occupies a specific nuclear compartment. Some genes escape dosage compensation, potentially resulting in sex-specific differences in gene expression. This review focuses on dosage compensation in mammals, with comparisons to fruit flies, nematodes, and birds. PMID:22974302

  13. Old but not (so) degenerated--slow evolution of largely homomorphic sex chromosomes in ratites.

    PubMed

    Yazdi, Homa Papoli; Ellegren, Hans

    2014-06-01

    Degeneration of the nonrecombining chromosome is a common feature of sex chromosome evolution, readily evident by the presence of a pair of largely heteromorphic chromosomes, like in eutherian mammals and birds. However, in ratites (order Palaeognathae, including, e.g., ostrich), the Z and W chromosomes are similar in size and largely undifferentiated, despite avian sex chromosome evolution was initiated > 130 Ma. To better understand what may limit sex chromosome evolution, we performed ostrich transcriptome sequencing and studied genes from the nonrecombining region of the W chromosome. Fourteen gametologous gene pairs present on the W chromosome and Z chromosome were identified, with synonymous sequence divergence of 0.027-0.177. The location of these genes on the Z chromosome was consistent with a sequential increase in divergence, starting 110-157 and ending 24-30 Ma. On the basis of the occurrence of Z-linked genes hemizygous in females, we estimate that about one-third of the Z chromosome does not recombine with the W chromosome in female meiosis. Pairwise d(N)/d(S) between gametologs decreased with age, suggesting strong evolutionary constraint in old gametologs. Lineage-specific d(N)/d(S) was consistently higher in W-linked genes, in accordance with the lower efficacy of selection expected in nonrecombining chromosomes. A higher ratio of GC > AT:AT > GC substitutions in W-linked genes supports a role for GC-biased gene conversion in differentially driving base composition on the two sex chromosomes. A male-to-female (M:F) expression ratio of close to one for recombining genes and close to two for Z-linked genes lacking a W copy show that dosage compensation is essentially absent. Some gametologous genes have retained active expression of the W copy in females (giving a M:F ratio of 1 for the gametologous gene pair), whereas for others W expression has become severely reduced resulting in a M:F ratio of close to 2. These observations resemble the patterns

  14. Did sex chromosome turnover promote divergence of the major mammal groups?: De novo sex chromosomes and drastic rearrangements may have posed reproductive barriers between monotremes, marsupials and placental mammals.

    PubMed

    Graves, Jennifer A M

    2016-08-01

    Comparative mapping and sequencing show that turnover of sex determining genes and chromosomes, and sex chromosome rearrangements, accompany speciation in many vertebrates. Here I review the evidence and propose that the evolution of therian mammals was precipitated by evolution of the male-determining SRY gene, defining a novel XY sex chromosome pair, and interposing a reproductive barrier with the ancestral population of synapsid reptiles 190 million years ago (MYA). Divergence was reinforced by multiple translocations in monotreme sex chromosomes, the first of which supplied a novel sex determining gene. A sex chromosome-autosome fusion may have separated eutherians (placental mammals) from marsupials 160 MYA. Another burst of sex chromosome change and speciation is occurring in rodents, precipitated by the degradation of the Y. And although primates have a more stable Y chromosome, it may be just a matter of time before the same fate overtakes our own lineage. Also watch the video abstract. © 2016 The Authors. BioEssays Published by WILEY Periodicals, Inc.

  15. Sex-biased gene expression at homomorphic sex chromosomes in emus and its implication for sex chromosome evolution.

    PubMed

    Vicoso, Beatriz; Kaiser, Vera B; Bachtrog, Doris

    2013-04-16

    Sex chromosomes originate from autosomes. The accumulation of sexually antagonistic mutations on protosex chromosomes selects for a loss of recombination and sets in motion the evolutionary processes generating heteromorphic sex chromosomes. Recombination suppression and differentiation are generally viewed as the default path of sex chromosome evolution, and the occurrence of old, homomorphic sex chromosomes, such as those of ratite birds, has remained a mystery. Here, we analyze the genome and transcriptome of emu (Dromaius novaehollandiae) and confirm that most genes on the sex chromosome are shared between the Z and W. Surprisingly, however, levels of gene expression are generally sex-biased for all sex-linked genes relative to autosomes, including those in the pseudoautosomal region, and the male-bias increases after gonad formation. This expression bias suggests that the emu sex chromosomes have become masculinized, even in the absence of ZW differentiation. Thus, birds may have taken different evolutionary solutions to minimize the deleterious effects imposed by sexually antagonistic mutations: some lineages eliminate recombination along the protosex chromosomes to physically restrict sexually antagonistic alleles to one sex, whereas ratites evolved sex-biased expression to confine the product of a sexually antagonistic allele to the sex it benefits. This difference in conflict resolution may explain the preservation of recombining, homomorphic sex chromosomes in other lineages and illustrates the importance of sexually antagonistic mutations driving the evolution of sex chromosomes.

  16. The genomics of plant sex chromosomes.

    PubMed

    Vyskot, Boris; Hobza, Roman

    2015-07-01

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

  17. Neo-sex chromosomes of Ronderosia bergi: insight into the evolution of sex chromosomes in grasshoppers.

    PubMed

    Palacios-Gimenez, O M; Marti, D A; Cabral-de-Mello, D C

    2015-09-01

    Sex chromosomes have evolved many times from morphologically identical autosome pairs, most often presenting several recombination suppression events, followed by accumulation of repetitive DNA sequences. In Orthoptera, most species have an X0♂ sex chromosome system. However, in the subfamily Melanoplinae, derived variants of neo-sex chromosomes (neo-XY♂ or neo-X1X2Y♂) emerged several times. Here, we examined the differentiation of neo-sex chromosomes in a Melanoplinae species with a neo-XY♂/XX♀ system, Ronderosia bergi, using several approaches: (i) classical cytogenetic analysis, (ii) mapping via fluorescent in situ hybridization of some selected repetitive DNA sequences and microdissected sex chromosomes, and (iii) immunolocalization of distinct histone modifications. The microdissected sex chromosomes were also used as sources for Polymerase chain reaction (PCR) amplification of RNA-coding multigene families, to study variants related to the sex chromosomes. Our data suggest that the R. bergi neo-Y has become differentiated after its formation by a Robertsonian translocation and inversions, and has accumulated repetitive DNA sequences. Interestingly, the ex autosomes incorporated into the neo-sex chromosomes retain some autosomal post-translational histone modifications, at least in metaphase I, suggesting that the establishment of functional modifications in neo-sex chromosomes is slower than their sequence differentiation.

  18. Conflict on the sex chromosomes: cause, effect, and complexity.

    PubMed

    Mank, Judith E; Hosken, David J; Wedell, Nina

    2014-10-03

    Intralocus sexual conflict and intragenomic conflict both affect sex chromosome evolution and can in extreme cases even cause the complete turnover of sex chromosomes. Additionally, established sex chromosomes often become the focus of heightened conflict. This creates a tangled relationship between sex chromosomes and conflict with respect to cause and effect. To further complicate matters, sexual and intragenomic conflict may exacerbate one another and thereby further fuel sex chromosome change. Different magnitudes and foci of conflict offer potential explanations for lineage-specific variation in sex chromosome evolution and answer long-standing questions as to why some sex chromosomes are remarkably stable, whereas others show rapid rates of evolutionary change.

  19. Bird-like sex chromosomes of platypus imply recent origin of mammal sex chromosomes.

    PubMed

    Veyrunes, Frédéric; Waters, Paul D; Miethke, Pat; Rens, Willem; McMillan, Daniel; Alsop, Amber E; Grützner, Frank; Deakin, Janine E; Whittington, Camilla M; Schatzkamer, Kyriena; Kremitzki, Colin L; Graves, Tina; Ferguson-Smith, Malcolm A; Warren, Wes; Marshall Graves, Jennifer A

    2008-06-01

    In therian mammals (placentals and marsupials), sex is determined by an XX female: XY male system, in which a gene (SRY) on the Y affects male determination. There is no equivalent in other amniotes, although some taxa (notably birds and snakes) have differentiated sex chromosomes. Birds have a ZW female: ZZ male system with no homology with mammal sex chromosomes, in which dosage of a Z-borne gene (possibly DMRT1) affects male determination. As the most basal mammal group, the egg-laying monotremes are ideal for determining how the therian XY system evolved. The platypus has an extraordinary sex chromosome complex, in which five X and five Y chromosomes pair in a translocation chain of alternating X and Y chromosomes. We used physical mapping to identify genes on the pairing regions between adjacent X and Y chromosomes. Most significantly, comparative mapping shows that, contrary to earlier reports, there is no homology between the platypus and therian X chromosomes. Orthologs of genes in the conserved region of the human X (including SOX3, the gene from which SRY evolved) all map to platypus chromosome 6, which therefore represents the ancestral autosome from which the therian X and Y pair derived. Rather, the platypus X chromosomes have substantial homology with the bird Z chromosome (including DMRT1) and to segments syntenic with this region in the human genome. Thus, platypus sex chromosomes have strong homology with bird, but not to therian sex chromosomes, implying that the therian X and Y chromosomes (and the SRY gene) evolved from an autosomal pair after the divergence of monotremes only 166 million years ago. Therefore, the therian X and Y are more than 145 million years younger than previously thought.

  20. Female meiotic sex chromosome inactivation in chicken.

    PubMed

    Schoenmakers, Sam; Wassenaar, Evelyne; Hoogerbrugge, Jos W; Laven, Joop S E; Grootegoed, J Anton; Baarends, Willy M

    2009-05-01

    During meiotic prophase in male mammals, the heterologous X and Y chromosomes remain largely unsynapsed, and meiotic sex chromosome inactivation (MSCI) leads to formation of the transcriptionally silenced XY body. In birds, the heterogametic sex is female, carrying Z and W chromosomes (ZW), whereas males have the homogametic ZZ constitution. During chicken oogenesis, the heterologous ZW pair reaches a state of complete heterologous synapsis, and this might enable maintenance of transcription of Z- and W chromosomal genes during meiotic prophase. Herein, we show that the ZW pair is transiently silenced, from early pachytene to early diplotene using immunocytochemistry and gene expression analyses. We propose that ZW inactivation is most likely achieved via spreading of heterochromatin from the W on the Z chromosome. Also, persistent meiotic DNA double-strand breaks (DSBs) may contribute to silencing of Z. Surprisingly, gammaH2AX, a marker of DSBs, and also the earliest histone modification that is associated with XY body formation in mammalian and marsupial spermatocytes, does not cover the ZW during the synapsed stage. However, when the ZW pair starts to desynapse, a second wave of gammaH2AX accumulates on the unsynapsed regions of Z, which also show a reappearance of the DSB repair protein RAD51. This indicates that repair of meiotic DSBs on the heterologous part of Z is postponed until late pachytene/diplotene, possibly to avoid recombination with regions on the heterologously synapsed W chromosome. Two days after entering diplotene, the Z looses gammaH2AX and shows reactivation. This is the first report of meiotic sex chromosome inactivation in a species with female heterogamety, providing evidence that this mechanism is not specific to spermatogenesis. It also indicates the presence of an evolutionary force that drives meiotic sex chromosome inactivation independent of the final achievement of synapsis.

  1. Cytogenetic comparison of heteromorphic and homomorphic sex chromosomes in Coccinia (Cucurbitaceae) points to sex chromosome turnover.

    PubMed

    Sousa, Aretuza; Fuchs, Jörg; Renner, Susanne S

    2017-06-01

    Our understanding of the evolution of plant sex chromosomes is increasing rapidly due to high-throughput sequencing data and phylogenetic and molecular-cytogenetic approaches that make it possible to infer the evolutionary direction and steps leading from homomorphic to heteromorphic sex chromosomes. Here, we focus on four species of Coccinia, a genus of 25 dioecious species, including Coccinia grandis, the species with the largest known plant Y chromosome. Based on a phylogeny for the genus, we selected three species close to C. grandis to test the distribution of eight repetitive elements including two satellites, and several plastid and mitochondrial probes, that we had previously found to have distinct accumulation patterns in the C. grandis genome. Additionally, we determined C-values and performed immunostaining experiments with (peri-)centromere-specific antibodies on two species (for comparison with C. grandis). In spite of no microscopic chromosomal heteromorphism, single pairs of chromosomes in male cells of all three species accumulate some of the very same repeats that are enriched on the C. grandis Y chromosome, pointing to either old (previous) sex chromosomes or incipient (newly arising) ones, that is, to sex chromosome turnover. A 144-bp centromeric satellite repeat (CgCent) that characterizes all C. grandis chromosomes except the Y is highly abundant in all centromeric regions of the other species, indicating that the centromeric sequence of the Y chromosome diverged very recently.

  2. Klinefelter syndrome and other sex chromosomal aneuploidies

    PubMed Central

    Visootsak, Jeannie; Graham, John M

    2006-01-01

    The term Klinefelter syndrome (KS) describes a group of chromosomal disorder in which there is at least one extra X chromosome to a normal male karyotype, 46,XY. XXY aneuploidy is the most common disorder of sex chromosomes in humans, with prevalence of one in 500 males. Other sex chromosomal aneuploidies have also been described, although they are much less frequent, with 48,XXYY and 48,XXXY being present in 1 per 17,000 to 1 per 50,000 male births. The incidence of 49,XXXXY is 1 per 85,000 to 100,000 male births. In addition, 46,XX males also exist and it is caused by translocation of Y material including sex determining region (SRY) to the X chromosome during paternal meiosis. Formal cytogenetic analysis is necessary to make a definite diagnosis, and more obvious differences in physical features tend to be associated with increasing numbers of sex chromosomes. If the diagnosis is not made prenatally, 47,XXY males may present with a variety of subtle clinical signs that are age-related. In infancy, males with 47,XXY may have chromosomal evaluations done for hypospadias, small phallus or cryptorchidism, developmental delay. The school-aged child may present with language delay, learning disabilities, or behavioral problems. The older child or adolescent may be discovered during an endocrine evaluation for delayed or incomplete pubertal development with eunuchoid body habitus, gynecomastia, and small testes. Adults are often evaluated for infertility or breast malignancy. Androgen replacement therapy should begin at puberty, around age 12 years, in increasing dosage sufficient to maintain age appropriate serum concentrations of testosterone, estradiol, follicle stimulating hormone (FSH), and luteinizing hormone (LH). The effects on physical and cognitive development increase with the number of extra Xs, and each extra X is associated with an intelligence quotient (IQ) decrease of approximately 15–16 points, with language most affected, particularly expressive

  3. 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.

  4. Psychoeducational Implications of Sex Chromosome Anomalies

    ERIC Educational Resources Information Center

    Wodrich, David L.; Tarbox, Jennifer

    2008-01-01

    Numerous anomalies involving the sex chromosomes (X or Y) have been documented and their impact on development, learning, and behavior studied. This article reviews three of these disorders, Turner syndrome, Klinefelter syndrome, and Lesch-Nyhan disease. Each of these three is associated with one or more selective impairments or behavioral…

  5. Psychoeducational Implications of Sex Chromosome Anomalies

    ERIC Educational Resources Information Center

    Wodrich, David L.; Tarbox, Jennifer

    2008-01-01

    Numerous anomalies involving the sex chromosomes (X or Y) have been documented and their impact on development, learning, and behavior studied. This article reviews three of these disorders, Turner syndrome, Klinefelter syndrome, and Lesch-Nyhan disease. Each of these three is associated with one or more selective impairments or behavioral…

  6. Sex chromosome inactivation in the male.

    PubMed

    Yan, Wei; McCarrey, John R

    2009-10-01

    Mammalian females have two X chromosomes, while males have only one X plus a Y chromosome. In order to balance X-linked gene dosage between the sexes, one X chromosome undergoes inactivation during development of female embryos. This process has been termed X-chromosome inactivation (XCI). Inactivation of the single X chromosome also occurs in the male, but is transient and is confined to the late stages of first meiotic prophase during spermatogenesis. This phenomenon has been termed meiotic sex chromosome inactivation (MSCI). A substantial portion ( approximately 15-25%) of X-linked mRNA-encoding genes escapes XCI in female somatic cells. While no mRNA genes are known to escape MSCI in males, approximately 80% of X-linked miRNA genes have been shown to escape this process. Recent results have led to the proposal that the RNA interference mechanism may be involved in regulating XCI in female cells. We suggest that some MSCI-escaping miRNAs may play a similar role in regulating MSCI in male germ cells.

  7. Human Male Meiotic Sex Chromosome Inactivation

    PubMed Central

    de Vries, Marieke; Vosters, Sanne; Merkx, Gerard; D'Hauwers, Kathleen; Wansink, Derick G.; Ramos, Liliana; de Boer, Peter

    2012-01-01

    In mammalian male gametogenesis the sex chromosomes are distinctive in both gene activity and epigenetic strategy. At first meiotic prophase the heteromorphic X and Y chromosomes are placed in a separate chromatin domain called the XY body. In this process, X,Y chromatin becomes highly phosphorylated at S139 of H2AX leading to the repression of gonosomal genes, a process known as meiotic sex chromosome inactivation (MSCI), which has been studied best in mice. Post-meiotically this repression is largely maintained. Disturbance of MSCI in mice leads to harmful X,Y gene expression, eventuating in spermatocyte death and sperm heterogeneity. Sperm heterogeneity is a characteristic of the human male. For this reason we were interested in the efficiency of MSCI in human primary spermatocytes. We investigated MSCI in pachytene spermatocytes of seven probands: four infertile men and three fertile controls, using direct and indirect in situ methods. A considerable degree of variation in the degree of MSCI was detected, both between and within probands. Moreover, in post-meiotic stages this variation was observed as well, indicating survival of spermatocytes with incompletely inactivated sex chromosomes. Furthermore, we investigated the presence of H3K9me3 posttranslational modifications on the X and Y chromatin. Contrary to constitutive centromeric heterochromatin, this heterochromatin marker did not specifically accumulate on the XY body, with the exception of the heterochromatic part of the Y chromosome. This may reflect the lower degree of MSCI in man compared to mouse. These results point at relaxation of MSCI, which can be explained by genetic changes in sex chromosome composition during evolution and candidates as a mechanism behind human sperm heterogeneity. PMID:22355370

  8. Human male meiotic sex chromosome inactivation.

    PubMed

    de Vries, Marieke; Vosters, Sanne; Merkx, Gerard; D'Hauwers, Kathleen; Wansink, Derick G; Ramos, Liliana; de Boer, Peter

    2012-01-01

    In mammalian male gametogenesis the sex chromosomes are distinctive in both gene activity and epigenetic strategy. At first meiotic prophase the heteromorphic X and Y chromosomes are placed in a separate chromatin domain called the XY body. In this process, X,Y chromatin becomes highly phosphorylated at S139 of H2AX leading to the repression of gonosomal genes, a process known as meiotic sex chromosome inactivation (MSCI), which has been studied best in mice. Post-meiotically this repression is largely maintained. Disturbance of MSCI in mice leads to harmful X,Y gene expression, eventuating in spermatocyte death and sperm heterogeneity. Sperm heterogeneity is a characteristic of the human male. For this reason we were interested in the efficiency of MSCI in human primary spermatocytes. We investigated MSCI in pachytene spermatocytes of seven probands: four infertile men and three fertile controls, using direct and indirect in situ methods. A considerable degree of variation in the degree of MSCI was detected, both between and within probands. Moreover, in post-meiotic stages this variation was observed as well, indicating survival of spermatocytes with incompletely inactivated sex chromosomes. Furthermore, we investigated the presence of H3K9me3 posttranslational modifications on the X and Y chromatin. Contrary to constitutive centromeric heterochromatin, this heterochromatin marker did not specifically accumulate on the XY body, with the exception of the heterochromatic part of the Y chromosome. This may reflect the lower degree of MSCI in man compared to mouse. These results point at relaxation of MSCI, which can be explained by genetic changes in sex chromosome composition during evolution and candidates as a mechanism behind human sperm heterogeneity.

  9. Gonadal sex chromosome complement in individuals with sex chromosomal and/or gonadal disorders

    SciTech Connect

    Bridge, J.A.; Sanger, W.G.; Seemayer, T.

    1994-09-01

    Gonadal abnormalities are characteristically seen in patients with sex chromosomal aneuploidy. Morphologically these abnormalities can be variable and are hypothesized to be dependent on the sex chromosomal consititution of the gonad (independent of the chromosomal complement of other tissues, such as peripheral blood lymphocytes). In this study, the gonadal sex chromosome complement was evaluated for potential mosaicism and correlated with the histopathology from 5 patients with known sex chromosomal and/or gonadal disorders. FISH techniques using X and Y chromosome specific probes were performed on nuclei extracted from paraffin embedded tissue. Gonadal tissue obtained from case 1 (a true hemaphroditic newborn) consisted of ovotestes and epididymis (left side) and ovary with fallopian tube (right side). Cytogenetic and FISH studies performed on blood, ovotestes and ovary revealed an XX complement. Cytogenetic analysis of blood from case 2, a 4-year-old with suspected Turner syndrome revealed 45,X/46,X,del(Y)(q11.21). FISH analysis of the resected gonads (histologically = immature testes) confirmed an X/XY mosaic complement. Histologically, the gonadal tissue was testicular. Severe autolysis prohibited successful analysis in the 2 remaining cases. In summary, molecular cytogenetic evaluation of gonadal tissue from individuals with sex chromosomal and/or gonadal disorders did not reveal tissue-specific anomalies which could account for differences observed pathologically.

  10. Transposable elements and early evolution of sex chromosomes in fish.

    PubMed

    Chalopin, Domitille; Volff, Jean-Nicolas; Galiana, Delphine; Anderson, Jennifer L; Schartl, Manfred

    2015-09-01

    In many organisms, the sex chromosome pair can be recognized due to heteromorphy; the Y and W chromosomes have often lost many genes due to the absence of recombination during meiosis and are frequently heterochromatic. Repetitive sequences are found at a high proportion on such heterochromatic sex chromosomes and the evolution and emergence of sex chromosomes has been connected to the dynamics of repeats and transposable elements. With an amazing plasticity of sex determination mechanisms and numerous instances of independent emergence of novel sex chromosomes, fish represent an excellent lineage to investigate the early stages of sex chromosome differentiation, where sex chromosomes often are homomorphic and not heterochromatic. We have analyzed the composition, distribution, and relative age of TEs from available sex chromosome sequences of seven teleost fish. We observed recent bursts of TEs and simple repeat accumulations around young sex determination loci. More strikingly, we detected transposable element (TE) amplifications not only on the sex determination regions of the Y and W sex chromosomes, but also on the corresponding regions of the X and Z chromosomes. In one species, we also clearly demonstrated that the observed TE-rich sex determination locus originated from a TE-poor genomic region, strengthening the link between TE accumulation and emergence of the sex determination locus. Altogether, our results highlight the role of TEs in the initial steps of differentiation and evolution of sex chromosomes.

  11. Signatures of Sex-Antagonistic Selection on Recombining Sex Chromosomes

    PubMed Central

    Kirkpatrick, Mark; Guerrero, Rafael F.

    2014-01-01

    Sex-antagonistic (SA) selection has major evolutionary consequences: it can drive genomic change, constrain adaptation, and maintain genetic variation for fitness. The recombining (or pseudoautosomal) regions of sex chromosomes are a promising setting in which to study SA selection because they tend to accumulate SA polymorphisms and because recombination allows us to deploy the tools of molecular evolution to locate targets of SA selection and quantify evolutionary forces. Here we use coalescent models to characterize the patterns of polymorphism expected within and divergence between recombining X and Y (or Z and W) sex chromosomes. SA selection generates peaks of divergence between X and Y that can extend substantial distances away from the targets of selection. Linkage disequilibrium between neutral sites is also inflated. We show how the pattern of divergence is altered when the SA polymorphism or the sex-determining region was recently established. We use data from the flowering plant Silene latifolia to illustrate how the strength of SA selection might be quantified using molecular data from recombining sex chromosomes. PMID:24578352

  12. Signatures of sex-antagonistic selection on recombining sex chromosomes.

    PubMed

    Kirkpatrick, Mark; Guerrero, Rafael F

    2014-06-01

    Sex-antagonistic (SA) selection has major evolutionary consequences: it can drive genomic change, constrain adaptation, and maintain genetic variation for fitness. The recombining (or pseudoautosomal) regions of sex chromosomes are a promising setting in which to study SA selection because they tend to accumulate SA polymorphisms and because recombination allows us to deploy the tools of molecular evolution to locate targets of SA selection and quantify evolutionary forces. Here we use coalescent models to characterize the patterns of polymorphism expected within and divergence between recombining X and Y (or Z and W) sex chromosomes. SA selection generates peaks of divergence between X and Y that can extend substantial distances away from the targets of selection. Linkage disequilibrium between neutral sites is also inflated. We show how the pattern of divergence is altered when the SA polymorphism or the sex-determining region was recently established. We use data from the flowering plant Silene latifolia to illustrate how the strength of SA selection might be quantified using molecular data from recombining sex chromosomes.

  13. Sex differences in the human brain and the impact of sex chromosomes and sex hormones.

    PubMed

    Lentini, E; Kasahara, M; Arver, S; Savic, I

    2013-10-01

    While there has been increasing support for the existence of cerebral sex differences, the mechanisms underlying these differences are unclear. Based on animal data, it has long been believed that sexual differentiation of the brain is primarily linked to organizational effects of fetal testosterone. This view is, however, in question as more recent data show the presence of sex differences before the onset of testosterone production. The present study focuses on the impact that sex chromosomes might have on these differences. Utilizing the inherent differences in sex and X-chromosome dosage among XXY males, XY males, and XX females, comparative voxel-based morphometry was conducted using sex hormones and sex chromosomes as covariates. Sex differences in the cerebellar and precentral gray matter volumes (GMV) were found to be related to X-chromosome dosage, whereas sex differences in the amygdala, the parahippocamus, and the occipital cortex were linked to testosterone levels. An increased number of sex chromosomes was associated with reduced GMV in the amygdala, caudate, and the temporal and insular cortices, with increased parietal GMV and reduced frontotemporal white matter volume. No selective, testosterone independent, effect of the Y-chromosome was detected. Based on these observations, it was hypothesized that programming of the motor cortex and parts of cerebellum is mediated by processes linked to X-escapee genes, which do not have Y-chromosome homologs, and that programming of certain limbic structures involves testosterone and X-chromosome escapee genes with Y-homologs.

  14. Evolution of sex chromosomes in Sauropsida

    PubMed Central

    Organ, Christopher L.; Janes, Daniel E.

    2008-01-01

    Reptiles (sauropsids) represent the sister group to mammals, and the basal members of Reptilia may provide a good model for the condition of the common ancestor of both groups. Sex-determining mechanisms (SDM) and organizations of sex chromosomes among genotypically sex-determining (GSD) species vary widely across reptiles. Birds and snakes, for example, are entirely GSD whereas other reptiles, like all crocodilians, exhibit temperature-dependent sex determination (TSD). Here we explore the evolution of sex chromosomes and SDM within reptiles, using family-level analyses of character evolution and applying parsimony, likelihood, Bayesian, and stochastic methods. We find support for the common ancestor of amphisbaenians and whiptail lizards (Laterata) possessing the XY (male heterogametic) GSD mechanism, while the ancestors of Testudines and Crocodylia, as well as the larger group Archosauromorpha (here containing turtles) are inferred to have exhibited TSD. We also find evidence consistent with the hypothesis that the XY system is more labile and evolves faster than does the ZW (female heterogametic) system. Phylogenetic-based speciation tests do not support an association between GSD and speciation, and reject the hypothesis that the presence of the XY system is associated with speciation in reptiles. PMID:21669812

  15. Learning disorders and sex chromosome aberrations.

    PubMed

    Hier, D B; Atkins, L; Perlo, V P

    1980-03-01

    No sex chromosome aberrations were detected in a prospective study of twenty adult dyslexic men. A retrospective study of eighty-nine subjects with known sex chromosome aberrations revealed twenty of them to be mentally-retarded. Among the sixty-nine subjects of normal intelligence, learning, speech and attention disorders were frequent. Children with 47,XYY, 47,XXY, and 47,XXX karyotypes appeared particularly prone to experience delays in speech development as well as later academic underachievement in language-related subjects. In contrast, speech development was normal in all of the girls with Turner's syndrome and later academic difficulties were usually confined to mathematics or science. Hyperactivity was noted with considerable frequency among 47,XYY and Turner's syndrome subjects, but not among subjects with a 47,XXX or 47,XXY karyotype.

  16. On the origin of sex chromosomes from meiotic drive.

    PubMed

    Úbeda, Francisco; Patten, Manus M; Wild, Geoff

    2015-01-07

    Most animals and many plants make use of specialized chromosomes (sex chromosomes) to determine an individual's sex. Best known are the XY and ZW sex-determination systems. Despite having evolved numerous times, sex chromosomes present something of an evolutionary puzzle. At their origin, alleles that dictate development as one sex or the other (primitive sex chromosomes) face a selective penalty, as they will be found more often in the more abundant sex. How is it possible that primitive sex chromosomes overcome this disadvantage? Any theory for the origin of sex chromosomes must identify the benefit that outweighs this cost and enables a sex-determining mutation to establish in the population. Here we show that a new sex-determining allele succeeds when linked to a sex-specific meiotic driver. The new sex-determining allele benefits from confining the driving allele to the sex in which it gains the benefit of drive. Our model requires few special assumptions and is sufficiently general to apply to the evolution of sex chromosomes in outbreeding cosexual or dioecious species. We highlight predictions of the model that can discriminate between this and previous theories of sex-chromosome origins.

  17. Origin of Amniote Sex Chromosomes: An Ancestral Super-Sex Chromosome, or Common Requirements?

    PubMed

    Ezaz, Tariq; Srikulnath, Kornsorn; Graves, Jennifer A Marshall

    2017-01-01

    The diversity of sex chromosomes among amniotes is the product of independent evolution of different systems in different lineages, defined by novel sex-determining genes. Convergent evolution is very common, suggesting that some genes are particularly adept at taking on a sex-determining role. Comparative gene mapping, and more recently whole genome sequencing, have now turned up other surprising relationships; different regions of the amniote genome that have become sex determining in some taxa seem to share synteny, or share sequence, in others. Is this, after all, evidence that these regions were once linked in a super-sex chromosome that underwent multiple fission in different ways in different amniote lineages? Or does it signify that special properties of sex chromosomes (paucity of active genes, low recombination, epigenetic regulation to achieve dosage compensation) predispose particular chromosomes to a sex-determining role? © The American Genetic Association 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  18. 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

  19. Are some chromosomes particularly good at sex? Insights from amniotes.

    PubMed

    O'Meally, Denis; Ezaz, Tariq; Georges, Arthur; Sarre, Stephen D; Graves, Jennifer A Marshall

    2012-01-01

    Several recent studies have produced comparative maps of genes on amniote sex chromosomes, revealing homology of gene content and arrangement across lineages as divergent as mammals and lizards. For example, the chicken Z chromosome, which shares homology with the sex chromosomes of all birds, monotremes, and a gecko, is a striking example of stability of genome organization and retention, or independent acquisition, of function in sex determination. In other lineages, such as snakes and therian mammals, well conserved but independently evolved sex chromosome systems have arisen. Among lizards, novel sex chromosomes appear frequently, even in congeneric species. Here, we review recent gene mapping data, examine the evolutionary relationships of amniote sex chromosomes and argue that gene content can predispose some chromosomes to a specialized role in sex determination.

  20. Chromatin configuration and epigenetic landscape at the sex chromosome bivalent during equine spermatogenesis

    PubMed Central

    Baumann, Claudia; Daly, Christopher M.; McDonnell, Sue M.; Viveiros, Maria M.; De La Fuente, Rabindranath

    2011-01-01

    Pairing of the sex chromosomes during mammalian meiosis is characterized by the formation of a unique heterochromatin structure at the XY body. The mechanisms underlying the formation of this nuclear domain are reportedly highly conserved from marsupials to mammals. In this study, we demonstrate that in contrast to all eutherian species studied to date, partial synapsis of the heterologous sex chromosomes during pachytene stage in the horse is not associated with the formation of a typical macrochromatin domain at the XY body. While phosphorylated histone H2AX (γH2AX) and macroH2A1.2 are present as a diffuse signal over the entire macrochromatin domain in mouse pachytene spermatocytes, γH2AX, macroH2A1.2, and the cohesin subunit SMC3 are preferentially enriched at meiotic sex chromosome cores in equine spermatocytes. Moreover, although several histone modifications associated with this nuclear domain in the mouse such as H3K4me2 and ubH2A are conspicuously absent in the equine XY body, prominent RNA polymerase II foci persist at the sex chromosomes. Thus, the localization of key marker proteins and histone modifications associated with the XY body in the horse differs significantly from all other mammalian systems described. These results demonstrate that the epigenetic landscape and heterochromatinization of the equine XY body might be regulated by alternative mechanisms and that some features of XY body formation may be evolutionary divergent in the domestic horse. We propose equine spermatogenesis as a unique model system for the study of the regulatory networks leading to the epigenetic control of gene expression during XY body formation. PMID:21274552

  1. Anolis sex chromosomes are derived from a single ancestral pair.

    PubMed

    Gamble, Tony; Geneva, Anthony J; Glor, Richard E; Zarkower, David

    2014-04-01

    To explain the frequency and distribution of heteromorphic sex chromosomes in the lizard genus Anolis, we compared the relative roles of sex chromosome conservation versus turnover of sex-determining mechanisms. We used model-based comparative methods to reconstruct karyotype evolution and the presence of heteromorphic sex chromosomes onto a newly generated Anolis phylogeny. We found that heteromorphic sex chromosomes evolved multiple times in the genus. Fluorescent in situ hybridization (FISH) of repetitive DNA showed variable rates of Y chromosome degeneration among Anolis species and identified previously undetected, homomorphic sex chromosomes in two species. We confirmed homology of sex chromosomes in the genus by performing FISH of an X-linked bacterial artificial chromosome (BAC) and quantitative PCR of X-linked genes in multiple Anolis species sampled across the phylogeny. Taken together, these results are consistent with long-term conservation of sex chromosomes in the group. Our results pave the way to address additional questions related to Anolis sex chromosome evolution and describe a conceptual framework that can be used to evaluate the origins and evolution of heteromorphic sex chromosomes in other clades. © 2013 The Author(s). Evolution © 2013 The Society for the Study of Evolution.

  2. Reproductive performance in women with sex chromosome mosaicism.

    PubMed

    Singh, D N; Hara, S; Foster, H W; Grimes, E M

    1980-05-01

    Among chromosomal analyses performed in 23 couples with a history of 2 or more spontaneous abortions, 5 women had mosaicism of the sex chromosomes, 46,XX/47,XXX, but all the men had normal 46,XY chromosomal complements. A review of the literature revealed that 75% of the fetuses of mothers with sex chromosome mosaicism were abnormal. Fifty percent of theses pregnancies ended in abortion and one third of the infants exhibited a chromosomal or physical abnormality. The possible effect of sex chromosome mosaicism on outcome of pregnancy is emphasized.

  3. Functional significance of the sex chromosomes during spermatogenesis

    PubMed Central

    Hu, Yueh-Chiang; Namekawa, Satoshi H.

    2015-01-01

    Mammalian sex chromosomes arose from an ordinary pair of autosomes. Over hundreds of millions of years, they have evolved into highly divergent X and Y chromosomes and have become increasingly specialized for male reproduction. Both sex chromosomes have acquired and amplified testis-specific genes, suggestive of roles in spermatogenesis. To understand how the sex chromosome genes participate in the regulation of spermatogenesis, we review genes, including single-copy, multi-copy, and ampliconic genes, whose spermatogenic functions have been demonstrated in mouse genetic studies. Sex chromosomes are subject to chromosome-wide transcriptional silencing in meiotic and postmeiotic stages of spermatogenesis. We also discuss particular sex-linked genes that escape postmeiotic silencing and their evolutionary implications. The unique gene contents and genomic structures of the sex chromosomes reflect their strategies to express genes at various stages of spermatogenesis and reveal the driving forces that shape their evolution. PMID:25948089

  4. 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

  5. Evidence for Sex Chromosome Turnover in Proteid Salamanders.

    PubMed

    Sessions, Stanley K; Bizjak Mali, Lilijana; Green, David M; Trifonov, Vladimir; Ferguson-Smith, Malcolm

    2016-01-01

    A major goal of genomic and reproductive biology is to understand the evolution of sex determination and sex chromosomes. Species of the 2 genera of the Salamander family Proteidae - Necturus of eastern North America, and Proteus of Southern Europe - have similar-looking karyotypes with the same chromosome number (2n = 38), which differentiates them from all other salamanders. However, Necturus possesses strongly heteromorphic X and Y sex chromosomes that Proteus lacks. Since the heteromorphic sex chromosomes of Necturus were detectable only with C-banding, we hypothesized that we could use C-banding to find sex chromosomes in Proteus. We examined mitotic material from colchicine-treated intestinal epithelium, and meiotic material from testes in specimens of Proteus, representing 3 genetically distinct populations in Slovenia. We compared these results with those from Necturus. We performed FISH to visualize telomeric sequences in meiotic bivalents. Our results provide evidence that Proteus represents an example of sex chromosome turnover in which a Necturus-like Y-chromosome has become permanently translocated to another chromosome converting heteromorphic sex chromosomes to homomorphic sex chromosomes. These results may be key to understanding some unusual aspects of demographics and reproductive biology of Proteus, and are discussed in the context of models of the evolution of sex chromosomes in amphibians.

  6. Meiotic sex chromosome inactivation in Drosophila.

    PubMed

    Vibranovski, Maria D

    2014-01-01

    In several different taxa, there is indubitable evidence of transcriptional silencing of the X and Y chromosomes in male meiotic cells of spermatogenesis. However, the so called meiotic sex chromosome inactivation (MSCI) has been recently a hot bed for debate in Drosophila melanogaster. This review covers cytological and genetic observations, data from transgenic constructs with testis-specific promoters, global expression profiles obtained from mutant, wild-type, larvae and adult testes as well as from cells of different stages of spermatogenesis. There is no dispute on that D. melanogaster spermatogenesis presents a down-regulation of X chromosome that does not result from the lack of dosage compensation. However, the issue is currently focused on the level of reduction of X-linked expression, the precise time it occurs and how many genes are affected. The deep examination of data and experiments in this review exposes the limitations intrinsic to the methods of studying MSCI in D. melanogaster. The current methods do not allow us to affirm anything else than the X chromosome down-regulation in meiosis (MSCI). Therefore, conclusion about level, degree or precise timing is inadequate until new approaches are implemented to know the details of MSCI or other processes involved for D. melanogaster model.

  7. Heteromorphic Sex Chromosomes: Navigating Meiosis without a Homologous Partner

    PubMed Central

    Checchi, Paula M.; Engebrecht, JoAnne

    2011-01-01

    Accurate chromosome segregation during meiosis relies on homology between the maternal and paternal chromosomes. Yet by definition, sex chromosomes of the heterogametic sex lack a homologous partner. Recent studies in a number of systems have shed light on the unique meiotic behavior of heteromorphic sex chromosomes, and highlight both the commonalities and differences in divergent species. During meiotic prophase, the homology-dependent processes of pairing, synapsis, and recombination have been modified in many different ways to ensure segregation of heteromorphic sex chromosomes at the first meiotic division. Additionally, an almost universal feature of heteromorphic sex chromosomes during meiosis is transcriptional silencing, or meiotic sex chromosome inactivation, an essential process proposed to prevent expression of genes deleterious to meiosis in the heterogametic sex as well as to shield unpaired sex chromosomes from recognition by meiotic checkpoints. Comparative analyses of the meiotic behavior of sex chromosomes in nematodes, mammals, and birds reveal important conserved features as well as provide insight into sex chromosome evolution. PMID:22113949

  8. Heteromorphic sex chromosomes: navigating meiosis without a homologous partner.

    PubMed

    Checchi, Paula M; Engebrecht, Joanne

    2011-09-01

    Accurate chromosome segregation during meiosis relies on homology between the maternal and paternal chromosomes. Yet by definition, sex chromosomes of the heterogametic sex lack a homologous partner. Recent studies in a number of systems have shed light on the unique meiotic behavior of heteromorphic sex chromosomes, and highlight both the commonalities and differences in divergent species. During meiotic prophase, the homology-dependent processes of pairing, synapsis, and recombination have been modified in many different ways to ensure segregation of heteromorphic sex chromosomes at the first meiotic division. Additionally, an almost universal feature of heteromorphic sex chromosomes during meiosis is transcriptional silencing, or meiotic sex chromosome inactivation, an essential process proposed to prevent expression of genes deleterious to meiosis in the heterogametic sex as well as to shield unpaired sex chromosomes from recognition by meiotic checkpoints. Comparative analyses of the meiotic behavior of sex chromosomes in nematodes, mammals, and birds reveal important conserved features as well as provide insight into sex chromosome evolution. Copyright © 2011 Wiley-Liss, Inc.

  9. Anolis sex chromosomes are derived from a single ancestral pair

    PubMed Central

    Gamble, Tony; Geneva, Anthony J.; Glor, Richard E.; Zarkower, David

    2014-01-01

    To explain the frequency and distribution of heteromorphic sex chromosomes in the lizard genus Anolis we compared the relative roles of sex chromosome conservation vs. turnover of sex determining mechanisms. We used model based comparative methods to reconstruct karyotype evolution and the presence of heteromorphic sex chromosomes onto a newly generated Anolis phylogeny. We found that heteromorphic sex chromosomes evolved multiple times in the genus. Fluorescent in situ hybridization (FISH) of repetitive DNA showed variable rates of Y chromosome degeneration among Anolis species and identified previously undetected, homomorphic sex chromosomes in two species. We confirmed homology of sex chromosomes in the genus by performing FISH of an X-linked BAC and qPCR of X-linked genes in multiple Anolis species sampled across the phylogeny. Taken together, these results are consistent with long-term conservation of sex chromosomes in the group. Our results pave the way to address additional questions related to Anolis sex chromosome evolution and describe a conceptual framework that can be used to evaluate the origins and evolution of heteromorphic sex chromosomes in other clades. PMID:24279795

  10. Sex Hormones and Sex Chromosomes Cause Sex Differences in the Development of Cardiovascular Diseases.

    PubMed

    Arnold, Arthur P; Cassis, Lisa A; Eghbali, Mansoureh; Reue, Karen; Sandberg, Kathryn

    2017-05-01

    This review summarizes recent evidence concerning hormonal and sex chromosome effects in obesity, atherosclerosis, aneurysms, ischemia/reperfusion injury, and hypertension. Cardiovascular diseases occur and progress differently in the 2 sexes, because biological factors differing between the sexes have sex-specific protective and harmful effects. By comparing the 2 sexes directly, and breaking down sex into its component parts, one can discover sex-biasing protective mechanisms that might be targeted in the clinic. Gonadal hormones, especially estrogens and androgens, have long been found to account for some sex differences in cardiovascular diseases, and molecular mechanisms mediating these effects have recently been elucidated. More recently, the inherent sexual inequalities in effects of sex chromosome genes have also been implicated as contributors in animal models of cardiovascular diseases, especially a deleterious effect of the second X chromosome found in females but not in males. Hormonal and sex chromosome mechanisms interact in the sex-specific control of certain diseases, sometimes by opposing the action of the other. © 2017 American Heart Association, Inc.

  11. The X factor: X chromosome dosage compensation in the evolutionarily divergent monotremes and marsupials.

    PubMed

    Whitworth, Deanne J; Pask, Andrew J

    2016-08-01

    Marsupials and monotremes represent evolutionarily divergent lineages from the majority of extant mammals which are eutherian, or placental, mammals. Monotremes possess multiple X and Y chromosomes that appear to have arisen independently of eutherian and marsupial sex chromosomes. Dosage compensation of X-linked genes occurs in monotremes on a gene-by-gene basis, rather than through chromosome-wide silencing, as is the case in eutherians and marsupials. Specifically, studies in the platypus have shown that for any given X-linked gene, a specific proportion of nuclei within a cell population will silence one locus, with the percentage of cells undergoing inactivation at that locus being highly gene-specific. Hence, it is perhaps not surprising that the expression level of X-linked genes in female platypus is almost double that in males. This is in contrast to the situation in marsupials where one of the two X chromosomes is inactivated in females by the long non-coding RNA RSX, a functional analogue of the eutherian XIST. However, marsupial X chromosome inactivation differs from that seen in eutherians in that it is exclusively the paternal X chromosome that is silenced. In addition, marsupials appear to have globally upregulated X-linked gene expression in both sexes, thus balancing their expression levels with those of the autosomes, a process initially proposed by Ohno in 1967 as being a fundamental component of the X chromosome dosage compensation mechanism but which may not have evolved in eutherians.

  12. Autosomal origin of sex chromosome in a polyploid plant

    USDA-ARS?s Scientific Manuscript database

    While theory on sex chromosome evolution is well developed, evidence of the early stages of this process remains elusive, in part because this process unfolded in many animals so long ago. The relatively recent and repeated evolution of separate sexes (dioecy) and sex chromosomes in plants, however,...

  13. Comparative analysis of sex chromosomes in Leporinus species (Teleostei, Characiformes) using chromosome painting.

    PubMed

    Parise-Maltempi, Patrícia Pasquali; da Silva, Edson Lourenço; Rens, Willem; Dearden, Frances; O'Brien, Patricia C M; Trifonov, Vladimir; Ferguson-Smith, Malcolm A

    2013-07-03

    The Leporinus genus, belonging to the Anostomidae family, is an interesting model for studies of sex chromosome evolution in fish, particularly because of the presence of heteromorphic sex chromosomes only in some species of the genus. In this study we used W chromosome-derived probes in a series of cross species chromosome painting experiments to try to understand events of sex chromosome evolution in this family. W chromosome painting probes from Leporinus elongatus, L. macrocephalus and L. obtusidens were hybridized to each others chromosomes. The results showed signals along their W chromosomes and the use of L. elongatus W probe against L. macrocephalus and L. obtusidens also showed signals over the Z chromosome. No signals were observed when the later aforementioned probe was used in hybridization procedures against other four Anostomidae species without sex chromosomes. Our results demonstrate a common origin of sex chromosomes in L. elongatus, L. macrocephalus and L. obtusidens but suggest that the L. elongatus chromosome system is at a different evolutionary stage. The absence of signals in the species without differentiated sex chromosomes does not exclude the possibility of cryptic sex chromosomes, but they must contain other Leporinus W sequences than those described here.

  14. Learning Disabilities in Children with Sex Chromosome Anomalies.

    ERIC Educational Resources Information Center

    Pennington, Bruce F.; And Others

    1982-01-01

    Results obtained from 44 children (ages 7 through 16) with sex chromosome abnormalities and from 17 chromosomally normal siblings demonstrated that children in the former group have an increased risk of encountering learning problems. (MP)

  15. Learning Disabilities in Children with Sex Chromosome Anomalies.

    ERIC Educational Resources Information Center

    Pennington, Bruce F.; And Others

    1982-01-01

    Results obtained from 44 children (ages 7 through 16) with sex chromosome abnormalities and from 17 chromosomally normal siblings demonstrated that children in the former group have an increased risk of encountering learning problems. (MP)

  16. Conserved sex chromosomes across adaptively radiated Anolis lizards.

    PubMed

    Rovatsos, Michail; Altmanová, Marie; Pokorná, Martina; Kratochvíl, Lukáš

    2014-07-01

    Vertebrates possess diverse sex-determining systems, which differ in evolutionary stability among particular groups. It has been suggested that poikilotherms possess more frequent turnovers of sex chromosomes than homoiotherms, whose effective thermoregulation can prevent the emergence of the sex reversals induced by environmental temperature. Squamate reptiles used to be regarded as a group with an extensive variability in sex determination; however, we document how the rather old radiation of lizards from the genus Anolis, known for exceptional ecomorphological variability, was connected with stability in sex chromosomes. We found that 18 tested species, representing most of the phylogenetic diversity of the genus, share the gene content of their X chromosomes. Furthermore, we discovered homologous sex chromosomes in species of two genera (Sceloporus and Petrosaurus) from the family Phrynosomatidae, serving here as an outgroup to Anolis. We can conclude that the origin of sex chromosomes within iguanas largely predates the Anolis radiation and that the sex chromosomes of iguanas remained conserved for a significant part of their evolutionary history. Next to therian mammals and birds, Anolis lizards therefore represent another adaptively radiated amniote clade with conserved sex chromosomes. We argue that the evolutionary stability of sex-determining systems may reflect an advanced stage of differentiation of sex chromosomes rather than thermoregulation strategy.

  17. Conserved Patterns of Sex Chromosome Dosage Compensation in the Lepidoptera (WZ/ZZ): Insights from a Moth Neo-Z Chromosome.

    PubMed

    Gu, Liuqi; Walters, James R; Knipple, Douglas C

    2017-03-01

    Where previously described, patterns of sex chromosome dosage compensation in the Lepidoptera (moths and butterflies) have several unusual characteristics. Other female-heterogametic (ZW/ZZ) species exhibit female Z-linked expression that is reduced compared with autosomal expression and male Z expression. In the Lepidoptera, however, Z expression typically appears balanced between sexes but overall reduced relative to autosomal expression, that is Z ≈ ZZ < AA. This pattern is not easily reconciled with theoretical expectations for the evolution of sex chromosome dosage compensation. Moreover, conflicting results linger due to discrepancies in data analyses and tissues sampled among lepidopterans. To address these issues, we performed RNA-seq to analyze sex chromosome dosage compensation in the codling moth, Cydia pomonella, which is a species from the earliest diverging lepidopteran lineage yet examined for dosage compensation and has a neo-Z chromosome resulting from an ancient Z:autosome fusion. While supported by intraspecific analyses, the Z ≈ ZZ < AA pattern was further evidenced by comparative study using autosomal orthologs of C. pomonella neo-Z genes in outgroup species. In contrast, dosage compensation appears to be absent in reproductive tissues. We thus argue that inclusion of reproductive tissues may explain the incongruence from a prior study on another moth species and that patterns of dosage compensation are likely conserved in the Lepidoptera. Notably, this pattern appears convergent with patterns in eutherian mammals (X ≈ XX < AA). Overall, our results contribute to the notion that the Lepidoptera present challenges both to classical theories regarding the evolution of sex chromosome dosage compensation and the emerging view of the association of dosage compensation with sexual heterogamety. © The Author(s) 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

  18. Conserved Patterns of Sex Chromosome Dosage Compensation in the Lepidoptera (WZ/ZZ): Insights from a Moth Neo-Z Chromosome

    PubMed Central

    Walters, James R.; Knipple, Douglas C.

    2017-01-01

    Where previously described, patterns of sex chromosome dosage compensation in the Lepidoptera (moths and butterflies) have several unusual characteristics. Other female-heterogametic (ZW/ZZ) species exhibit female Z-linked expression that is reduced compared with autosomal expression and male Z expression. In the Lepidoptera, however, Z expression typically appears balanced between sexes but overall reduced relative to autosomal expression, that is Z ≈ ZZ < AA. This pattern is not easily reconciled with theoretical expectations for the evolution of sex chromosome dosage compensation. Moreover, conflicting results linger due to discrepancies in data analyses and tissues sampled among lepidopterans. To address these issues, we performed RNA-seq to analyze sex chromosome dosage compensation in the codling moth, Cydia pomonella, which is a species from the earliest diverging lepidopteran lineage yet examined for dosage compensation and has a neo-Z chromosome resulting from an ancient Z:autosome fusion. While supported by intraspecific analyses, the Z ≈ ZZ < AA pattern was further evidenced by comparative study using autosomal orthologs of C. pomonella neo-Z genes in outgroup species. In contrast, dosage compensation appears to be absent in reproductive tissues. We thus argue that inclusion of reproductive tissues may explain the incongruence from a prior study on another moth species and that patterns of dosage compensation are likely conserved in the Lepidoptera. Notably, this pattern appears convergent with patterns in eutherian mammals (X ≈ XX < AA). Overall, our results contribute to the notion that the Lepidoptera present challenges both to classical theories regarding the evolution of sex chromosome dosage compensation and the emerging view of the association of dosage compensation with sexual heterogamety. PMID:28338816

  19. Effects of sex chromosome dosage on corpus callosum morphology in supernumerary sex chromosome aneuploidies

    PubMed Central

    2014-01-01

    Background Supernumerary sex chromosome aneuploidies (sSCA) are characterized by the presence of one or more additional sex chromosomes in an individual’s karyotype; they affect around 1 in 400 individuals. Although there is high variability, each sSCA subtype has a characteristic set of cognitive and physical phenotypes. Here, we investigated the differences in the morphometry of the human corpus callosum (CC) between sex-matched controls 46,XY (N =99), 46,XX (N =93), and six unique sSCA karyotypes: 47,XYY (N =29), 47,XXY (N =58), 48,XXYY (N =20), 47,XXX (N =30), 48,XXXY (N =5), and 49,XXXXY (N =6). Methods We investigated CC morphometry using local and global area, local curvature of the CC boundary, and between-landmark distance analysis (BLDA). We hypothesized that CC morphometry would vary differentially along a proposed spectrum of Y:X chromosome ratio with supernumerary Y karyotypes having the largest CC areas and supernumerary X karyotypes having significantly smaller CC areas. To investigate this, we defined an sSCA spectrum based on a descending Y:X karyotype ratio: 47,XYY, 46,XY, 48,XXYY, 47,XXY, 48,XXXY, 49,XXXXY, 46,XX, 47,XXX. We similarly explored the effects of both X and Y chromosome numbers within sex. Results of shape-based metrics were analyzed using permutation tests consisting of 5,000 iterations. Results Several subregional areas, local curvature, and BLDs differed between groups. Moderate associations were found between area and curvature in relation to the spectrum and X and Y chromosome counts. BLD was strongly associated with X chromosome count in both male and female groups. Conclusions Our results suggest that X- and Y-linked genes have differential effects on CC morphometry. To our knowledge, this is the first study to compare CC morphometry across these extremely rare groups. PMID:25780557

  20. The Evolution of Sex Chromosomes and Dosage Compensation in Plants

    PubMed Central

    Shearn, Rylan; Marais, Gabriel AB

    2017-01-01

    Plant sex chromosomes can be vastly different from those of the few historical animal model organisms from which most of our understanding of sex chromosome evolution is derived. Recently, we have seen several advancements from studies on green algae, brown algae, and land plants that are providing a broader understanding of the variable ways in which sex chromosomes can evolve in distant eukaryotic groups. Plant sex-determining genes are being identified and, as expected, are completely different from those in animals. Species with varying levels of differentiation between the X and Y have been found in plants, and these are hypothesized to be representing different stages of sex chromosome evolution. However, we are also finding that sex chromosomes can remain morphologically unchanged over extended periods of time. Where degeneration of the Y occurs, it appears to proceed similarly in plants and animals. Dosage compensation (a phenomenon that compensates for the consequent loss of expression from the Y) has now been documented in a plant system, its mechanism, however, remains unknown. Research has also begun on the role of sex chromosomes in sexual conflict resolution, and it appears that sex-biased genes evolve similarly in plants and animals, although the functions of these genes remain poorly studied. Because the difficulty in obtaining sex chromosome sequences is increasingly being overcome by methodological developments, there is great potential for further discovery within the field of plant sex chromosome evolution. PMID:28391324

  1. A neo-sex-chromosome that drives post-zygotic sex determiniation in the Hessian fly

    USDA-ARS?s Scientific Manuscript database

    Two nonoverlapping autosomal inversions defined unusual neo-sex chromosomes in the Hessian fly (Mayetiola destructor). Like other neo-sex chromosomes, these were normally heterozygous, present only in one sex, and suppressed recombination around a sex-determining master switch. Their unusual propert...

  2. Insights into the evolution of mammalian telomerase: Platypus TERT shares similarities with genes of birds and other reptiles and localizes on sex chromosomes

    PubMed Central

    2012-01-01

    Background The TERT gene encodes the catalytic subunit of the telomerase complex and is responsible for maintaining telomere length. Vertebrate telomerase has been studied in eutherian mammals, fish, and the chicken, but less attention has been paid to other vertebrates. The platypus occupies an important evolutionary position, providing unique insight into the evolution of mammalian genes. We report the cloning of a platypus TERT (OanTERT) ortholog, and provide a comparison with genes of other vertebrates. Results The OanTERT encodes a protein with a high sequence similarity to marsupial TERT and avian TERT. Like the TERT of sauropsids and marsupials, as well as that of sharks and echinoderms, OanTERT contains extended variable linkers in the N-terminal region suggesting that they were present already in basal vertebrates and lost independently in ray-finned fish and eutherian mammals. Several alternatively spliced OanTERT variants structurally similar to avian TERT variants were identified. Telomerase activity is expressed in all platypus tissues like that of cold-blooded animals and murine rodents. OanTERT was localized on pseudoautosomal regions of sex chromosomes X3/Y2, expanding the homology between human chromosome 5 and platypus sex chromosomes. Synteny analysis suggests that TERT co-localized with sex-linked genes in the last common mammalian ancestor. Interestingly, female platypuses express higher levels of telomerase in heart and liver tissues than do males. Conclusions OanTERT shares many features with TERT of the reptilian outgroup, suggesting that OanTERT represents the ancestral mammalian TERT. Features specific to TERT of eutherian mammals have, therefore, evolved more recently after the divergence of monotremes. PMID:22655747

  3. Morphologically differentiated sex chromosomes in neotropical freshwater fish.

    PubMed

    de Almeida Toledo, L F; Foresti, F

    2001-01-01

    A general survey of the occurrence of morphologically differentiated sex chromosomes in the neotropical freshwater fishes is presented. The total number of 32 occurrences involving simple XX-XY and ZZ-ZW, and multiple X1X2Y, XY1Y2 and ZW1W2 sex chromosome systems is described, with comments on the aspects of sex chromosome evolution in this fish fauna. The occurrence of different sex chromosome systems in related species of the same genus, or in different populations of the same nominal species, involving male and sometimes female heterogamety, and differences in the molecular composition of sex-linked heterochromatin, are considered as indicative of the early stage of sex chromosomes evolution in fish.

  4. Single origin of sex chromosomes and multiple origins of B chromosomes in fish genus Characidium.

    PubMed

    Pansonato-Alves, José Carlos; Serrano, Érica Alves; Utsunomia, Ricardo; Camacho, Juan Pedro M; da Costa Silva, Guilherme José; Vicari, Marcelo Ricardo; Artoni, Roberto Ferreira; Oliveira, Cláudio; Foresti, Fausto

    2014-01-01

    Chromosome painting with DNA probes obtained from supernumerary (B) and sex chromosomes in three species of fish genus Characidium (C. gomesi, C. pterostictum and C. oiticicai) showed a close resemblance in repetitive DNA content between B and sex chromosomes in C. gomesi and C. pterostictum. This suggests an intraspecific origin for B chromosomes in these two species, probably deriving from sex chromosomes. In C. oiticicai, however, a DNA probe obtained from its B chromosome hybridized with the B but not with the A chromosomes, suggesting that the B chromosome in this species could have arisen interspecifically, although this hypothesis needs further investigation. A molecular phylogenetic analysis performed on nine Characidium species, with two mtDNA genes, showed that the presence of heteromorphic sex chromosomes in these species is a derived condition, and that their origin could have been unique, a conclusion also supported by interspecific chromosome painting with a CgW probe derived from the W chromosome in C. gomesi. Summing up, our results indicate that whereas heteromorphic sex chromosomes in the genus Characidium appear to have had a common and unique origin, B chromosomes may have had independent origins in different species. Our results also show that molecular phylogenetic analysis is an excellent complement for cytogenetic studies by unveiling the direction of evolutionary chromosome changes.

  5. Single Origin of Sex Chromosomes and Multiple Origins of B Chromosomes in Fish Genus Characidium

    PubMed Central

    Pansonato-Alves, José Carlos; Serrano, Érica Alves; Utsunomia, Ricardo; Camacho, Juan Pedro M.; da Costa Silva, Guilherme José; Vicari, Marcelo Ricardo; Artoni, Roberto Ferreira; Oliveira, Cláudio; Foresti, Fausto

    2014-01-01

    Chromosome painting with DNA probes obtained from supernumerary (B) and sex chromosomes in three species of fish genus Characidium (C. gomesi, C. pterostictum and C. oiticicai) showed a close resemblance in repetitive DNA content between B and sex chromosomes in C. gomesi and C. pterostictum. This suggests an intraspecific origin for B chromosomes in these two species, probably deriving from sex chromosomes. In C. oiticicai, however, a DNA probe obtained from its B chromosome hybridized with the B but not with the A chromosomes, suggesting that the B chromosome in this species could have arisen interspecifically, although this hypothesis needs further investigation. A molecular phylogenetic analysis performed on nine Characidium species, with two mtDNA genes, showed that the presence of heteromorphic sex chromosomes in these species is a derived condition, and that their origin could have been unique, a conclusion also supported by interspecific chromosome painting with a CgW probe derived from the W chromosome in C. gomesi. Summing up, our results indicate that whereas heteromorphic sex chromosomes in the genus Characidium appear to have had a common and unique origin, B chromosomes may have had independent origins in different species. Our results also show that molecular phylogenetic analysis is an excellent complement for cytogenetic studies by unveiling the direction of evolutionary chromosome changes. PMID:25226580

  6. Comparative analysis by chromosome painting of the sex chromosomes in arvicolid rodents.

    PubMed

    Acosta, M J; Romero-Fernández, I; Sánchez, A; Marchal, J A

    2011-01-01

    Sex chromosome evolution in mammals has been extensively investigated through chromosome-painting analyses. In some rodent species from the subfamily Arvicolinae the sex chromosomes contain remarkable features such as giant size, a consequence of heterochromatic enlargement, or asynaptic behaviour during male meiosis. Here, we have made a comparative study of the sex chromosomes in 6 arvicolid species using different probes from the X and Y chromosomes of 3 species, in order to gain knowledge about intra- or interspecific preservation of euchromatic regions. Our results clearly reveal poor conservation of the euchromatic region of the Y chromosome within these species, while the euchromatin on the X chromosome is extremely well preserved. Furthermore, we detected no clear correlation between the synaptic/asynaptic behaviour of the sex chromosomes, and the presence or absence of sequence homology within their euchromatic regions. Notably, our study has shown a new relationship between the giant sex chromosomes of 2 species, Microtus agrestis and Microtus cabrerae, that is, both X and Y share a novel region of common sequences in the euchromatin that is not present in the other species analysed. This interspecific euchromatic conservation, limited to the giant sex chromosomes, could point towards a common evolutionary origin for the heterochromatic enlargement process that has characterized the evolution of the sex chromosomes in some arvicolid species. Copyright © 2010 S. Karger AG, Basel.

  7. Aplastic Anemia in Two Patients with Sex Chromosome Aneuploidies.

    PubMed

    Rush, Eric T; Schaefer, G Bradley; Sanger, Warren G; Coccia, Peter F

    2015-01-01

    Sex chromosome aneuploidies range in incidence from rather common to exceedingly rare and have a variable phenotype. We report 2 patients with sex chromosome aneuploidies who developed severe aplastic anemia requiring treatment. The first patient had tetrasomy X (48,XXXX) and presented at 9 years of age, and the second patient had trisomy X (47,XXX) and presented at 5 years of age. Although aplastic anemia has been associated with other chromosomal abnormalities, sex chromosome abnormalities have not been traditionally considered a risk factor for this condition. A review of the literature reveals that at least one other patient with a sex chromosome aneuploidy (45,X) has suffered from aplastic anemia and that other autosomal chromosomal anomalies have been described. Despite the uncommon nature of each condition, it is possible that the apparent association is coincidental. A better understanding of the genetic causes of aplastic anemia remains important.

  8. Chromosome landmarks and autosome-sex chromosome translocations in Rumex hastatulus, a plant with XX/XY1Y2 sex chromosome system.

    PubMed

    Grabowska-Joachimiak, Aleksandra; Kula, Adam; Książczyk, Tomasz; Chojnicka, Joanna; Sliwinska, Elwira; Joachimiak, Andrzej J

    2015-06-01

    Rumex hastatulus is the North American endemic dioecious plant with heteromorphic sex chromosomes. It is differentiated into two chromosomal races: Texas (T) race characterised by a simple XX/XY sex chromosome system and North Carolina (NC) race with a polymorphic XX/XY1Y2 sex chromosome system. The gross karyotype morphology in NC race resembles the derived type, but chromosomal changes that occurred during its evolution are poorly understood. Our C-banding/DAPI and fluorescence in situ hybridization (FISH) experiments demonstrated that Y chromosomes of both races are enriched in DAPI-positive sequences and that the emergence of polymorphic sex chromosome system was accompanied by the break of ancestral Y chromosome and switch in the localization of 5S rDNA, from autosomes to sex chromosomes (X and Y2). Two contrasting domains were detected within North Carolina Y chromosomes: the older, highly heterochromatinised, inherited from the original Y chromosome and the younger, euchromatic, representing translocated autosomal material. The flow-cytometric DNA estimation showed ∼3.5 % genome downsizing in the North Carolina race. Our results are in contradiction to earlier reports on the lack of heterochromatin within Y chromosomes of this species and enable unambiguous identification of autosomes involved in the autosome-heterosome translocation, providing useful chromosome landmarks for further studies on the karyotype and sex chromosome differentiation in this species.

  9. Homologous sex chromosomes in three deeply divergent anuran species.

    PubMed

    Brelsford, Alan; Stöck, Matthias; Betto-Colliard, Caroline; Dubey, Sylvain; Dufresnes, Christophe; Jourdan-Pineau, Hélène; Rodrigues, Nicolas; Savary, Romain; Sermier, Roberto; Perrin, Nicolas

    2013-08-01

    Comparative genomic studies are revealing that, in sharp contrast with the strong stability found in birds and mammals, sex determination mechanisms are surprisingly labile in cold-blooded vertebrates, with frequent transitions between different pairs of sex chromosomes. It was recently suggested that, in context of this high turnover, some chromosome pairs might be more likely than others to be co-opted as sex chromosomes. Empirical support, however, is still very limited. Here we show that sex-linked markers from three highly divergent groups of anurans map to Xenopus tropicalis scaffold 1, a large part of which is homologous to the avian sex chromosome. Accordingly, the bird sex determination gene DMRT1, known to play a key role in sex differentiation across many animal lineages, is sex linked in all three groups. Our data provide strong support for the idea that some chromosome pairs are more likely than others to be co-opted as sex chromosomes because they harbor key genes from the sex determination pathway. © 2013 The Author(s). Evolution © 2013 The Society for the Study of Evolution.

  10. Sex chromosome evolution: historical insights and future perspectives

    PubMed Central

    Nordén, Anna K.

    2017-01-01

    Many separate-sexed organisms have sex chromosomes controlling sex determination. Sex chromosomes often have reduced recombination, specialized (frequently sex-specific) gene content, dosage compensation and heteromorphic size. Research on sex determination and sex chromosome evolution has increased over the past decade and is today a very active field. However, some areas within the field have not received as much attention as others. We therefore believe that a historic overview of key findings and empirical discoveries will put current thinking into context and help us better understand where to go next. Here, we present a timeline of important conceptual and analytical models, as well as empirical studies that have advanced the field and changed our understanding of the evolution of sex chromosomes. Finally, we highlight gaps in our knowledge so far and propose some specific areas within the field that we recommend a greater focus on in the future, including the role of ecology in sex chromosome evolution and new multilocus models of sex chromosome divergence. PMID:28469017

  11. Turnover of Sex Chromosomes in Celebensis Group Medaka Fishes.

    PubMed

    Myosho, Taijun; Takehana, Yusuke; Hamaguchi, Satoshi; Sakaizumi, Mitsuru

    2015-10-23

    Sex chromosomes and the sex-determining (SD) gene are variable in vertebrates. In particular, medaka fishes in the genus Oryzias show an extremely large diversity in sex chromosomes and the SD gene, providing a good model to study the evolutionary process by which they turnover. Here, we investigated the sex determination system and sex chromosomes in six celebensis group species. Our sex-linkage analysis demonstrated that all species had an XX-XY sex determination system, and that the Oryzias marmoratus and O. profundicola sex chromosomes were homologous to O. latipes linkage group (LG) 10, while those of the other four species, O. celebensis, O. matanensis, O. wolasi, and O. woworae, were homologous to O. latipes LG 24. The phylogenetic relationship suggested a turnover of the sex chromosomes from O. latipes LG 24 to LG 10 within this group. Six sex-linkage maps showed that the former two and the latter four species shared a common SD locus, respectively, suggesting that the LG 24 acquired the SD function in a common ancestor of the celebensis group, and that the LG 10 SD function appeared in a common ancestor of O. marmoratus and O. profundicola after the divergence of O. matanensis. Additionally, fine mapping and association analysis in the former two species revealed that Sox3 on the Y chromosome is a prime candidate for the SD gene, and that the Y-specific 430-bp insertion might be involved in its SD function.

  12. Molecular cytogenetic mapping of Humulus lupulus sex chromosomes.

    PubMed

    Divashuk, M G; Alexandrov, O S; Kroupin, P Yu; Karlov, G I

    2011-01-01

    Dioecy is relatively rare in plants and sex determination systems vary among such species. A good example of a plant with heteromorphic sex chromosomes is hop (Humulus lupulus). The genotypes carrying XX or XY chromosomes correspond to female and male plants, respectively. Until now no clear cytogenetic markers for the sex chromosomes of hop have been established. Here, for the first time the sex chromosomes of hop are clearly identified and characterized. The high copy sequence of hop (HSR1) has been cloned and localized on chromosomes by fluorescence in situ hybridization. The HSR1 repeat has shown subtelomeric location on autosomes with the same intensity of the signal. The signal has been present in the subtelomeric region of the long arm and in the near-centromeric region but absent in the telomeric region of the short arm of the X chromosome. At the same time the signal has been found in the telomeric region only of the long arm of the Y chromosome. This finding indicates that the sex chromosomes of hop have evolved from a pair of autosomes via ancient translocation or inversion. The observation of the meiotic configuration of the sex bivalents shows the location of a pseudoautosomal region on the long arms of X and Y chromosomes.

  13. Cytogenetic Insights into the Evolution of Chromosomes and Sex Determination Reveal Striking Homology of Turtle Sex Chromosomes to Amphibian Autosomes.

    PubMed

    Montiel, Eugenia E; Badenhorst, Daleen; Lee, Ling S; Literman, Robert; Trifonov, Vladimir; Valenzuela, Nicole

    2016-01-01

    Turtle karyotypes are highly conserved compared to other vertebrates; yet, variation in diploid number (2n = 26-68) reflects profound genomic reorganization, which correlates with evolutionary turnovers in sex determination. We evaluate the published literature and newly collected comparative cytogenetic data (G- and C-banding, 18S-NOR, and telomere-FISH mapping) from 13 species spanning 2n = 28-68 to revisit turtle genome evolution and sex determination. Interstitial telomeric sites were detected in multiple lineages that underwent diploid number and sex determination turnovers, suggesting chromosomal rearrangements. C-banding revealed potential interspecific variation in centromere composition and interstitial heterochromatin at secondary constrictions. 18S-NORs were detected in secondary constrictions in a single chromosomal pair per species, refuting previous reports of multiple NORs in turtles. 18S-NORs are linked to ZW chromosomes in Apalone and Pelodiscus and to X (not Y) in Staurotypus. Notably, comparative genomics across amniotes revealed that the sex chromosomes of several turtles, as well as mammals and some lizards, are homologous to components of Xenopus tropicalis XTR1 (carrying Dmrt1). Other turtle sex chromosomes are homologous to XTR4 (carrying Wt1). Interestingly, all known turtle sex chromosomes, except in Trionychidae, evolved via inversions around Dmrt1 or Wt1. Thus, XTR1 appears to represent an amniote proto-sex chromosome (perhaps linked ancestrally to XTR4) that gave rise to turtle and other amniote sex chromosomes.

  14. Evolution of sex chromosomes ZW of Schistosoma mansoni inferred from chromosome paint and BAC mapping analyses.

    PubMed

    Hirai, Hirohisa; Hirai, Yuriko; LoVerde, Philip T

    2012-12-01

    Chromosomes of schistosome parasites among digenetic flukes have a unique evolution because they exhibit the sex chromosomes ZW, which are not found in the other groups of flukes that are hermaphrodites. We conducted molecular cytogenetic analyses for investigating the sex chromosome evolution using chromosome paint analysis and BAC clones mapping. To carry this out, we developed a technique for making paint probes of genomic DNA from a single scraped chromosome segment using a chromosome microdissection system, and a FISH mapping technique for BAC clones. Paint probes clearly identified each of the 8 pairs of chromosomes by a different fluorochrome color. Combination analysis of chromosome paint analysis with Z/W probes and chromosome mapping with 93 BAC clones revealed that the W chromosome of Schistosoma mansoni has evolved by at least four inversion events and heterochromatinization. Nine of 93 BAC clones hybridized with both the Z and W chromosomes, but the locations were different between Z and W chromosomes. The homologous regions were estimated to have moved from the original Z chromosome to the differentiated W chromosome by three inversions events that occurred before W heterohcromatinization. An inversion that was observed in the heterochromatic region of the W chromosome likely occurred after W heterochromatinization. These inversions and heterochromatinization are hypothesized to be the key factors that promoted the evolution of the W chromosome of S. mansoni. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

  15. Cretaceous park of sex determination: sex chromosomes are conserved across iguanas.

    PubMed

    Rovatsos, Michail; Pokorná, Martina; Altmanová, Marie; Kratochvíl, Lukáš

    2014-03-01

    Many poikilothermic vertebrate lineages, especially among amphibians and fishes, possess a rapid turnover of sex chromosomes, while in endotherms there is a notable stability of sex chromosomes. Reptiles in general exhibit variability in sex-determining systems; as typical poikilotherms, they might be expected to have a rapid turnover of sex chromosomes. However, molecular data which would enable the testing of the stability of sex chromosomes are lacking in most lineages. Here, we provide molecular evidence that sex chromosomes are highly conserved across iguanas, one of the most species-rich clade of reptiles. We demonstrate that members of the New World families Iguanidae, Tropiduridae, Leiocephalidae, Phrynosomatidae, Dactyloidae and Crotaphytidae, as well as of the family Opluridae which is restricted to Madagascar, all share homologous sex chromosomes. As our sampling represents the majority of the phylogenetic diversity of iguanas, the origin of iguana sex chromosomes can be traced back in history to the basal splitting of this group which occurred during the Cretaceous period. Iguanas thus show a stability of sex chromosomes comparable to mammals and birds and represent the group with the oldest sex chromosomes currently known among amniotic poikilothermic vertebrates.

  16. Cretaceous park of sex determination: sex chromosomes are conserved across iguanas

    PubMed Central

    Rovatsos, Michail; Pokorná, Martina; Altmanová, Marie; Kratochvíl, Lukáš

    2014-01-01

    Many poikilothermic vertebrate lineages, especially among amphibians and fishes, possess a rapid turnover of sex chromosomes, while in endotherms there is a notable stability of sex chromosomes. Reptiles in general exhibit variability in sex-determining systems; as typical poikilotherms, they might be expected to have a rapid turnover of sex chromosomes. However, molecular data which would enable the testing of the stability of sex chromosomes are lacking in most lineages. Here, we provide molecular evidence that sex chromosomes are highly conserved across iguanas, one of the most species-rich clade of reptiles. We demonstrate that members of the New World families Iguanidae, Tropiduridae, Leiocephalidae, Phrynosomatidae, Dactyloidae and Crotaphytidae, as well as of the family Opluridae which is restricted to Madagascar, all share homologous sex chromosomes. As our sampling represents the majority of the phylogenetic diversity of iguanas, the origin of iguana sex chromosomes can be traced back in history to the basal splitting of this group which occurred during the Cretaceous period. Iguanas thus show a stability of sex chromosomes comparable to mammals and birds and represent the group with the oldest sex chromosomes currently known among amniotic poikilothermic vertebrates. PMID:24598109

  17. A primitive Y chromosome in papaya marks incipient sex chromosome evolution.

    PubMed

    Liu, Zhiyong; Moore, Paul H; Ma, Hao; Ackerman, Christine M; Ragiba, Makandar; Yu, Qingyi; Pearl, Heather M; Kim, Minna S; Charlton, Joseph W; Stiles, John I; Zee, Francis T; Paterson, Andrew H; Ming, Ray

    2004-01-22

    Many diverse systems for sex determination have evolved in plants and animals. One involves physically distinct (heteromorphic) sex chromosomes (X and Y, or Z and W) that are homozygous in one sex (usually female) and heterozygous in the other (usually male). Sex chromosome evolution is thought to involve suppression of recombination around the sex determination genes, rendering permanently heterozygous a chromosomal region that may then accumulate deleterious recessive mutations by Muller's ratchet, and fix deleterious mutations by hitchhiking as nearby favourable mutations are selected on the Y chromosome. Over time, these processes may cause the Y chromosome to degenerate and to diverge from the X chromosome over much of its length; for example, only 5% of the human Y chromosome still shows X-Y recombination. Here we show that papaya contains a primitive Y chromosome, with a male-specific region that accounts for only about 10% of the chromosome but has undergone severe recombination suppression and DNA sequence degeneration. This finding provides direct evidence for the origin of sex chromosomes from autosomes.

  18. Multiple sex chromosome systems in howler monkeys (Platyrrhini, Alouatta)

    PubMed Central

    Steinberg, Eliana Ruth; Nieves, Mariela; Mudry, Marta Dolores

    2014-01-01

    Abstract In light of the multiple sex chromosome systems observed in howler monkeys (Alouatta Lacépède, 1799) a combined cladistic analysis using chromosomal and molecular characters was applied to discuss the possible origin of these systems. Mesoamerican and South American howlers were karyologically compared. FISH analysis using the chromosome painting probes for the #3 and #15 human chromosomes was applied to corroborate the homeology of the sexual systems. We found that the HSA3/15 syntenic association, present in the sex chromosome systems of South American Howlers, is not present in those of Mesoamerican ones. The autosomes involved in the translocation that formed the sexual systems in the Mesoamerican and South American species are different, thus suggesting an independent origin. Parsimony analysis resolved the phylogenetic relationships among howler species, demonstrating utility of the combined approach. A hypothesis for the origin of the multiple sex chromosome systems for the genus is proposed. PMID:24744833

  19. The unique sex chromosome system in platypus and echidna.

    PubMed

    Ferguson-Smith, M A; Rens, W

    2010-10-01

    A striking example of the power of chromosome painting has been the resolution of the male platypus karyotype and the pairing relationships of the chain often sex chromosomes. We have extended our analysis to the nine sex chromosomes of the male echidna. Cross-species painting with platypus shows that the first five chromosomes in the chain are identical in both, but the order of the remainder are different and, in each species, a different autosome replaces one of the five X chromosomes. As the therian X is homologous mainly to platypus autosome 6 and echidna 16, and as SRY is absent in both, the sex determination mechanism in monotremes is currently unknown. Several of the X and Y chromosomes contain genes orthologous to those in the avian Z but the significance of this is also unknown. It seems likely that a novel testis determinant is carried by a Y chromosome common to platypus and echidna. We have searched for candidates for this determinant among the many genes known to be involved in vertebrate sex differentiation. So far fourteen such genes have been mapped, eleven are autosomal in platypus, two map to the differential regions of X chromosomes, and one maps to a pairing segment and is likewise excluded. Search for the platypus testis-determining gene continues, and the extension of comparative mapping between platypus and birds and reptiles may shed light on the ancestral origin of monotreme sex chromosomes.

  20. Evolution of vertebrate sex chromosomes and dosage compensation.

    PubMed

    Graves, Jennifer A Marshall

    2016-01-01

    Differentiated sex chromosomes in mammals and other vertebrates evolved independently but in strikingly similar ways. Vertebrates with differentiated sex chromosomes share the problems of the unequal expression of the genes borne on sex chromosomes, both between the sexes and with respect to autosomes. Dosage compensation of genes on sex chromosomes is surprisingly variable - and can even be absent - in different vertebrate groups. Systems that compensate for different gene dosages include a wide range of global, regional and gene-by-gene processes that differ in their extent and their molecular mechanisms. However, many elements of these control systems are similar across distant phylogenetic divisions and show parallels to other gene silencing systems. These dosage systems cannot be identical by descent but were probably constructed from elements of ancient silencing mechanisms that are ubiquitous among vertebrates and shared throughout eukaryotes.

  1. Sex Chromosome Evolution in Amniotes: Applications for Bacterial Artificial Chromosome Libraries

    PubMed Central

    Janes, Daniel E.; Valenzuela, Nicole; Ezaz, Tariq; Amemiya, Chris; Edwards, Scott V.

    2011-01-01

    Variability among sex chromosome pairs in amniotes denotes a dynamic history. Since amniotes diverged from a common ancestor, their sex chromosome pairs and, more broadly, sex-determining mechanisms have changed reversibly and frequently. These changes have been studied and characterized through the use of many tools and experimental approaches but perhaps most effectively through applications for bacterial artificial chromosome (BAC) libraries. Individual BAC clones carry 100–200 kb of sequence from one individual of a target species that can be isolated by screening, mapped onto karyotypes, and sequenced. With these techniques, researchers have identified differences and similarities in sex chromosome content and organization across amniotes and have addressed hypotheses regarding the frequency and direction of past changes. Here, we review studies of sex chromosome evolution in amniotes and the ways in which the field of research has been affected by the advent of BAC libraries. PMID:20981143

  2. Chromosome painting of Z and W sex chromosomes in Characidium (Characiformes, Crenuchidae).

    PubMed

    Pazian, Marlon F; Shimabukuro-Dias, Cristiane Kioko; Pansonato-Alves, José Carlos; Oliveira, Claudio; Foresti, Fausto

    2013-03-01

    Some species of the genus Characidium have heteromorphic ZZ/ZW sex chromosomes with a totally heterochromatic W chromosome. Methods for chromosome microdissection associated with chromosome painting have become important tools for cytogenetic studies in Neotropical fish. In Characidium cf. fasciatum, the Z chromosome contains a pericentromeric heterochromatin block, whereas the W chromosome is completely heterochromatic. Therefore, a probe was produced from the W chromosome through microdissection and degenerate oligonucleotide-primed polymerase chain reaction amplification. FISH was performed using the W probe on the chromosomes of specimens of this species. This revealed expressive marks in the pericentromeric region of the Z chromosome as well as a completely painted W chromosome. When applying the same probe on chromosome preparations of C. cf. gomesi and Characidium sp., a pattern similar to C. cf. fasciatum was found, while C. cf. zebra, C. cf. lagosantense and Crenuchus spilurus species showed no hybridization signals. Structural changes in the chromosomes of an ancestral sexual system in the group that includes the species C. cf. gomesi, C. cf. fasciatum and Characidium sp., could have contributed to the process of speciation and could represent a causal mechanism of chromosomal diversification in this group. The heterochromatinization process possibly began in homomorphic and homologous chromosomes of an ancestral form, and this process could have given rise to the current patterns found in the species with sex chromosome heteromorphism.

  3. The genetics of sex chromosomes: evolution and implications for hybrid incompatibility.

    PubMed

    Johnson, Norman A; Lachance, Joseph

    2012-05-01

    Heteromorphic sex chromosomes, where one sex has two different types of sex chromosomes, face very different evolutionary consequences than do autosomes. Two important features of sex chromosomes arise from being present in only one copy in one of the sexes: dosage compensation and the meiotic silencing of sex chromosomes. Other differences arise because sex chromosomes spend unequal amounts of time in each sex. Thus, the impact of evolutionary processes (mutation, selection, genetic drift, and meiotic drive) differs substantially between each sex chromosome, and between the sex chromosomes and the autosomes. Sex chromosomes also play a disproportionate role in Haldane's rule and other important patterns related to hybrid incompatibility, and thus speciation. We review the consequences of sex chromosomes on hybrid incompatibility. A theme running through this review is that epigenetic processes, notably those related to chromatin, may be more important to the evolution of sex chromosomes and the evolution of hybrid incompatibility than previously recognized.

  4. Effects of sex chromosome aneuploidy on male sexual behavior.

    PubMed

    Park, J H; Burns-Cusato, M; Dominguez-Salazar, E; Riggan, A; Shetty, S; Arnold, A P; Rissman, E F

    2008-08-01

    Incidence of sex chromosome aneuploidy in men is as high as 1:500. The predominant conditions are an additional Y chromosome (47,XYY) or an additional X chromosome (47,XXY). Behavioral studies using animal models of these conditions are rare. To assess the role of sex chromosome aneuploidy on sexual behavior, we used mice with a spontaneous mutation on the Y chromosome in which the testis-determining gene Sry is deleted (referred to as Y(-)) and insertion of a Sry transgene on an autosome. Dams were aneuploid (XXY(-)) and the sires had an inserted Sry transgene (XYSry). Litters contained six male genotypes, XY, XYY(-), XXSry, XXY(-)Sry, XYSry and XYY(-)Sry. In order to eliminate possible differences in levels of testosterone, all of the subjects were castrated and received testosterone implants prior to tests for male sex behavior. Mice with an additional copy of the Y(-) chromosome (XYY(-)) had shorter latencies to intromit and achieve ejaculations than XY males. In a comparison of the four genotypes bearing the Sry transgene, males with two copies of the X chromosome (XXSry and XXY(-)Sry) had longer latencies to mount and thrust than males with only one copy of the X chromosome (XYSry and XYY(-)Sry) and decreased frequencies of mounts and intromissions as compared with XYSry males. The results implicate novel roles for sex chromosome genes in sexual behaviors.

  5. Effects of sex chromosome aneuploidy on male sexual behavior

    PubMed Central

    Park, J. H.; Burns-Cusato, M.; Dominguez-Salazar, E.; Riggan, A.; Shetty, S.; Arnold, A. P.; Rissman, E. F.

    2008-01-01

    Incidence of sex chromosome aneuploidy in men is as high as 1:500. The predominant conditions are an additional Y chromosome (47,XYY) or an additional X chromosome (47,XXY). Behavioral studies using animal models of these conditions are rare. To assess the role of sex chromosome aneuploidy on sexual behavior, we used mice with a spontaneous mutation on the Y chromosome in which the testis-determining gene Sry is deleted (referred to as Y−) and insertion of a Sry transgene on an autosome. Dams were aneuploid (XXY−) and the sires had an inserted Sry transgene (XYSry). Litters contained six male genotypes, XY, XYY−, XXSry, XXY−Sry, XYSry and XYY−Sry. In order to eliminate possible differences in levels of testosterone, all of the subjects were castrated and received testosterone implants prior to tests for male sex behavior. Mice with an additional copy of the Y− chromosome (XYY−) had shorter latencies to intromit and achieve ejaculations than XY males. In a comparison of the four genotypes bearing the Sry transgene, males with two copies of the X chromosome (XXSry and XXY−Sry) had longer latencies to mount and thrust than males with only one copy of the X chromosome (XYSry and XYY−Sry) and decreased frequencies of mounts and intromissions as compared with XYSry males. The results implicate novel roles for sex chromosome genes in sexual behaviors. PMID:18363850

  6. Functional significance of the sex chromosomes during spermatogenesis.

    PubMed

    Hu, Yueh-Chiang; Namekawa, Satoshi H

    2015-06-01

    Mammalian sex chromosomes arose from an ordinary pair of autosomes. Over hundreds of millions of years, they have evolved into highly divergent X and Y chromosomes and have become increasingly specialized for male reproduction. Both sex chromosomes have acquired and amplified testis-specific genes, suggestive of roles in spermatogenesis. To understand how the sex chromosome genes participate in the regulation of spermatogenesis, we review genes, including single-copy, multi-copy, and ampliconic genes, whose spermatogenic functions have been demonstrated in mouse genetic studies. Sex chromosomes are subject to chromosome-wide transcriptional silencing in meiotic and postmeiotic stages of spermatogenesis. We also discuss particular sex-linked genes that escape postmeiotic silencing and their evolutionary implications. The unique gene contents and genomic structures of the sex chromosomes reflect their strategies to express genes at various stages of spermatogenesis and reveal the driving forces that shape their evolution.Free Chinese abstract: A Chinese translation of this abstract is freely available at http://www.reproduction-online.org/content/149/6/R265/suppl/DC1.Free Japanese abstract: A Japanese translation of this abstract is freely available at http://www.reproduction-online.org/content/149/6/R265/suppl/DC2.

  7. Towards the delineation of the ancestral eutherian genome organization: comparative genome maps of human and the African elephant (Loxodonta africana) generated by chromosome painting.

    PubMed

    Frönicke, Lutz; Wienberg, Johannes; Stone, Gary; Adams, Lisa; Stanyon, Roscoe

    2003-07-07

    This study presents a whole-genome comparison of human and a representative of the Afrotherian clade, the African elephant, generated by reciprocal Zoo-FISH. An analysis of Afrotheria genomes is of special interest, because recent DNA sequence comparisons identify them as the oldest placental mammalian clade. Complete sets of whole-chromosome specific painting probes for the African elephant and human were constructed by degenerate oligonucleotide-primed PCR amplification of flow-sorted chromosomes. Comparative genome maps are presented based on their hybridization patterns. These maps show that the elephant has a moderately rearranged chromosome complement when compared to humans. The human paint probes identified 53 evolutionary conserved segments on the 27 autosomal elephant chromosomes and the X chromosome. Reciprocal experiments with elephant probes delineated 68 conserved segments in the human genome. The comparison with a recent aardvark and elephant Zoo-FISH study delineates new chromosomal traits which link the two Afrotherian species phylogenetically. In the absence of any morphological evidence the chromosome painting data offer the first non-DNA sequence support for an Afrotherian clade. The comparative human and elephant genome maps provide new insights into the karyotype organization of the proto-afrotherian, the ancestor of extant placental mammals, which most probably consisted of 2n=46 chromosomes.

  8. Early Development of Children with Sex Chromosome Aberrations.

    ERIC Educational Resources Information Center

    Haka-Ilse, Katerina; And Others

    1978-01-01

    Arthur Retlaw and Associates, Inc., Suite 2080, 1603 Orrington Avenue, Evanston, Illinois 60201. A prospective study was made of the early development of 42 children with sex chromosome aberrations. (Author)

  9. Increased sex chromosome expression and epigenetic abnormalities in spermatids from male mice with Y chromosome deletions.

    PubMed

    Reynard, Louise N; Turner, James M A

    2009-11-15

    During male meiosis, the X and Y chromosomes are transcriptionally silenced, a process termed meiotic sex chromosome inactivation (MSCI). Recent studies have shown that the sex chromosomes remain substantially transcriptionally repressed after meiosis in round spermatids, but the mechanisms involved in this later repression are poorly understood. Mice with deletions of the Y chromosome long arm (MSYq-) have increased spermatid expression of multicopy X and Y genes, and so represent a model for studying post-meiotic sex chromosome repression. Here, we show that the increase in sex chromosome transcription in spermatids from MSYq- mice affects not only multicopy but also single-copy XY genes, as well as an X-linked reporter gene. This increase in transcription is accompanied by specific changes in the sex chromosome histone code, including almost complete loss of H4K8Ac and reduction of H3K9me3 and CBX1. Together, these data show that an MSYq gene regulates sex chromosome gene expression as well as chromatin remodelling in spermatids.

  10. The mouse X chromosome is enriched for sex-biased genes not subject to selection by meiotic sex chromosome inactivation.

    PubMed

    Khil, Pavel P; Smirnova, Natalya A; Romanienko, Peter J; Camerini-Otero, R Daniel

    2004-06-01

    Sex chromosomes are subject to sex-specific selective evolutionary forces. One model predicts that genes with sex-biased expression should be enriched on the X chromosome. In agreement with Rice's hypothesis, spermatogonial genes are over-represented on the X chromosome of mice and sex- and reproduction-related genes are over-represented on the human X chromosome. Male-biased genes are under-represented on the X chromosome in worms and flies, however. Here we show that mouse spermatogenesis genes are relatively under-represented on the X chromosome and female-biased genes are enriched on it. We used Spo11(-/-) mice blocked in spermatogenesis early in meiosis to evaluate the temporal pattern of gene expression in sperm development. Genes expressed before the Spo11 block are enriched on the X chromosome, whereas those expressed later in spermatogenesis are depleted. Inactivation of the X chromosome in male meiosis may be a universal driving force for X-chromosome demasculinization.

  11. The Ancestral Eutherian Karyotype Is Present in Xenarthra

    PubMed Central

    Svartman, Marta; Stone, Gary; Stanyon, Roscoe

    2006-01-01

    Molecular studies have led recently to the proposal of a new super-ordinal arrangement of the 18 extant Eutherian orders. From the four proposed super-orders, Afrotheria and Xenarthra were considered the most basal. Chromosome-painting studies with human probes in these two mammalian groups are thus key in the quest to establish the ancestral Eutherian karyotype. Although a reasonable amount of chromosome-painting data with human probes have already been obtained for Afrotheria, no Xenarthra species has been thoroughly analyzed with this approach. We hybridized human chromosome probes to metaphases of species (Dasypus novemcinctus, Tamandua tetradactyla, and Choloepus hoffmanii) representing three of the four Xenarthra families. Our data allowed us to review the current hypotheses for the ancestral Eutherian karyotype, which range from 2n = 44 to 2n = 48. One of the species studied, the two-toed sloth C. hoffmanii (2n = 50), showed a chromosome complement strikingly similar to the proposed 2n = 48 ancestral Eutherian karyotype, strongly reinforcing it. PMID:16848642

  12. The ancestral eutherian karyotype is present in Xenarthra.

    PubMed

    Svartman, Marta; Stone, Gary; Stanyon, Roscoe

    2006-07-01

    Molecular studies have led recently to the proposal of a new super-ordinal arrangement of the 18 extant Eutherian orders. From the four proposed super-orders, Afrotheria and Xenarthra were considered the most basal. Chromosome-painting studies with human probes in these two mammalian groups are thus key in the quest to establish the ancestral Eutherian karyotype. Although a reasonable amount of chromosome-painting data with human probes have already been obtained for Afrotheria, no Xenarthra species has been thoroughly analyzed with this approach. We hybridized human chromosome probes to metaphases of species (Dasypus novemcinctus, Tamandua tetradactyla, and Choloepus hoffmanii) representing three of the four Xenarthra families. Our data allowed us to review the current hypotheses for the ancestral Eutherian karyotype, which range from 2n = 44 to 2n = 48. One of the species studied, the two-toed sloth C. hoffmanii (2n = 50), showed a chromosome complement strikingly similar to the proposed 2n = 48 ancestral Eutherian karyotype, strongly reinforcing it.

  13. Neo-sex chromosomes and adaptive potential in tortricid pests

    USDA-ARS?s Scientific Manuscript database

    Changes in genome architecture often have a significant effect on ecological specialization and speciation. This effect may be further enhanced by involvement of sex chromosomes playing a disproportionate role in reproductive isolation. We have physically mapped the Z chromosome of the major pome fr...

  14. Turner syndrome: the case of the missing sex chromosome.

    PubMed

    Zinn, A R; Page, D C; Fisher, E M

    1993-03-01

    Turner syndrome is the phenotype associated with the absence of a second sex chromosome in humans. Recent observations support the hypothesis that the phenotype results from haploid dosage of genes that are common to the X and Y chromosomes and that escape X inactivation. A goal of current studies is the identification of these "Turner' genes.

  15. Identification of sex chromosomes in lake trout (Salvelinus namaycush).

    PubMed

    Phillips, R B; Ihssen, P E

    1985-01-01

    In the male trout there is a difference in the quinacrine banding and C-banding patterns between the two homologs of the second largest chromosome pair. This chromosome is the only large submetacentric in the karyotype, making it easy to identify and suggesting that the sex chromosomes have become differentiated since the time of tetraploidization. In males one homolog has a medium-to-large quinacrine bright heterochromatic band on the end of the short arm, while the other lacks it completely. In females both homologs have medium-to-large quinacrine bright heterochromatic bands. Approximately half the progeny from every lake trout cross studied and half the eggs from every lake trout population examined were heteromorphic for a difference in this chromosome band. Results from sexed fish, reciprocal F1 hybrids between brook trout and lake trout, and gynogenetic haploids are all consistent with the interpretation that chromosome 2 is the sex chromosome. These results suggest that the addition of heterochromatin to the X can be the first step in the inhibition of crossing over between the X and Y chromosomes required for sex chromosome differentiation.

  16. Prospective studies on children with sex chromosome aneuploidy

    SciTech Connect

    Ratcliffe, S.G.; Paul, N.

    1986-01-01

    This book contains 11 selections. Some of the titles are: Growth and Development from Early to Midadolescence of Children with X and Y Chromosome Aneuploidy: The Toronto Study; Sex Chromomal Aneuploidy: Perspective and Longitudinal Studies; Psychologic Study of XYY and XXY Men; and Cellular and Molecular Studies in Human Chromosomal Diseases.

  17. A Neo-Sex Chromosome That Drives Postzygotic Sex Determination in the Hessian Fly (Mayetiola destructor)

    PubMed Central

    Benatti, Thiago R.; Valicente, Fernando H.; Aggarwal, Rajat; Zhao, Chaoyang; Walling, Jason G.; Chen, Ming-Shun; Cambron, Sue E.; Schemerhorn, Brandon J.; Stuart, Jeffrey J.

    2010-01-01

    Two nonoverlapping autosomal inversions defined unusual neo-sex chromosomes in the Hessian fly (Mayetiola destructor). Like other neo-sex chromosomes, these were normally heterozygous, present only in one sex, and suppressed recombination around a sex-determining master switch. Their unusual properties originated from the anomalous Hessian fly sex determination system in which postzygotic chromosome elimination is used to establish the sex-determining karyotypes. This system permitted the evolution of a master switch (Chromosome maintenance, Cm) that acts maternally. All of the offspring of females that carry Cm-associated neo-sex chromosomes attain a female-determining somatic karyotype and develop as females. Thus, the chromosomes act as maternal effect neo-W's, or W-prime (W′) chromosomes, where ZW′ females mate with ZZ males to engender female-producing (ZW′) and male-producing (ZZ) females in equal numbers. Genetic mapping and physical mapping identified the inversions. Their distribution was determined in nine populations. Experimental matings established the association of the inversions with Cm and measured their recombination suppression. The inversions are the functional equivalent of the sciarid X-prime chromosomes. We speculate that W′ chromosomes exist in a variety of species that produce unisexual broods. PMID:20026681

  18. Sex chromosome changes in leukemia: cytogenetics and molecular aspects.

    PubMed

    Shahrabi, Saeid; Khodadi, Elahe; Saba, Fakhredin; Shahjahani, Mohammad; Saki, Najmaldin

    2017-09-10

    Sex chromosome loss (SCL) can occur in older men as a physiological phenomenon or as an acquired abnormality in leukemia. Loss of chromosome Y and loss of chromosome X are acquired disorders that are mainly observed in patients over 80 years as well as in myeloid and lymphoid malignancies. In this review, we examine the cytogenetic and molecular changes of sex chromosomes in leukemia. Relevant English language literature were searched and retrieved from PubMed search engine (1990-2016). The following keywords were used: 'Sex chromosomes', 'Leukemia' and 'Cytogenetics'. The loss of tumor suppressor genes along with these chromosomal abnormalities in the majority of malignant cells in bone marrow (BM) has raised the question whether this is an age-related phenomenon or has occurred as a result of clonal abnormality. On the other hand, the presence of these chromosomal abnormalities in a number of genetic diseases associated with leukemia leads to progression of malignancy, and their role in peripheral blood stem cell transplantation confirm the finding that these chromosomal abnormalities can play an important role in clonal abnormality. The presence of these abnormalities can cause genetic instability in BM and result in the development of a malignant clone and progression of the disease. In addition, the evaluation of SCL together with the genes involved in these chromosomes can contribute to predict the disease prognosis as well as monitoring of malignancy.

  19. Chromosome elimination and sex determination in springtails (Insecta, Collembola).

    PubMed

    Dallai, R; Fanciulli, P P; Frati, F

    1999-10-15

    A post-zygotic mechanism of sex determination is described in the two symphypleonans Dicyrtomina ornata (Nicolet) and Ptenothrix italica Dallai. The process consists of the loss of two sex chromosomes from the male embryo. At the end of the first meiotic division of spermatogenesis, a second chromosome elimination occurs, allowing half the secondary spermatocytes, later transformed into spermatids, to receive a complete haploid set of chromosomes. The secondary spermatocytes, which receive an incomplete set of chromosomes, degenerate. Males of the two collembolan species, therefore, produce a reduced number (50%) of spermatozoa. Females of D. ornata have 2n = 12 and males 2n = 10 chromosomes; females of P. italica have 2n = 14 and males 2n = 12 chromosomes. In both species, oogenesis proceeds normally and chromosomes pair and form chiasmata in meiotic prophase. The adaptive significance of this post-zygotic mechanism of sex determination is discussed. The mechanism seems to be a characteristic feature of the suborder Symphypleona. The neanurid Arthropleona Anurida maritima (Guérin), which was studied for comparative analysis, has 2n = 8 chromosomes and normal spermatogenesis producing haploid nuclei with four chromosomes. J. Exp. Zool. (Mol. Dev. Evol.) 285:215-225, 1999.

  20. Extreme heterochiasmy and nascent sex chromosomes in European tree frogs.

    PubMed

    Berset-Brändli, Laura; Jaquiéry, Julie; Broquet, Thomas; Ulrich, Yuko; Perrin, Nicolas

    2008-07-07

    We investigated sex-specific recombination rates in Hyla arborea, a species with nascent sex chromosomes and male heterogamety. Twenty microsatellites were clustered into six linkage groups, all showing suppressed or very low recombination in males. Seven markers were sex linked, none of them showing any sign of recombination in males (r=0.00 versus 0.43 on average in females). This opposes classical models of sex chromosome evolution, which envision an initially small differential segment that progressively expands as structural changes accumulate on the Y chromosome. For autosomes, maps were more than 14 times longer in females than in males, which seems the highest ratio documented so far in vertebrates. These results support the pleiotropic model of Haldane and Huxley, according to which recombination is reduced in the heterogametic sex by general modifiers that affect recombination on the whole genome.

  1. Evolutionary history of novel genes on the tammar wallaby Y chromosome: Implications for sex chromosome evolution

    PubMed Central

    Murtagh, Veronica J.; O'Meally, Denis; Sankovic, Natasha; Delbridge, Margaret L.; Kuroki, Yoko; Boore, Jeffrey L.; Toyoda, Atsushi; Jordan, Kristen S.; Pask, Andrew J.; Renfree, Marilyn B.; Fujiyama, Asao; Graves, Jennifer A. Marshall; Waters, Paul D.

    2012-01-01

    We report here the isolation and sequencing of 10 Y-specific tammar wallaby (Macropus eugenii) BAC clones, revealing five hitherto undescribed tammar wallaby Y genes (in addition to the five genes already described) and several pseudogenes. Some genes on the wallaby Y display testis-specific expression, but most have low widespread expression. All have partners on the tammar X, along with homologs on the human X. Nonsynonymous and synonymous substitution ratios for nine of the tammar XY gene pairs indicate that they are each under purifying selection. All 10 were also identified as being on the Y in Tasmanian devil (Sarcophilus harrisii; a distantly related Australian marsupial); however, seven have been lost from the human Y. Maximum likelihood phylogenetic analyses of the wallaby YX genes, with respective homologs from other vertebrate representatives, revealed that three marsupial Y genes (HCFC1X/Y, MECP2X/Y, and HUWE1X/Y) were members of the ancestral therian pseudoautosomal region (PAR) at the time of the marsupial/eutherian split; three XY pairs (SOX3/SRY, RBMX/Y, and ATRX/Y) were isolated from each other before the marsupial/eutherian split, and the remaining three (RPL10X/Y, PHF6X/Y, and UBA1/UBE1Y) have a more complex evolutionary history. Thus, the small marsupial Y chromosome is surprisingly rich in ancient genes that are retained in at least Australian marsupials and evolved from testis–brain expressed genes on the X. PMID:22128133

  2. Conservation of Regional Variation in Sex-Specific Sex Chromosome Regulation

    PubMed Central

    Wright, Alison E.; Zimmer, Fabian; Harrison, Peter W.; Mank, Judith E.

    2015-01-01

    Regional variation in sex-specific gene regulation has been observed across sex chromosomes in a range of animals and is often a function of sex chromosome age. The avian Z chromosome exhibits substantial regional variation in sex-specific regulation, where older regions show elevated levels of male-biased expression. Distinct sex-specific regulation also has been observed across the male hypermethylated (MHM) region, which has been suggested to be a region of nascent dosage compensation. Intriguingly, MHM region regulatory features have not been observed in distantly related avian species despite the hypothesis that it is situated within the oldest region of the avian Z chromosome and is therefore orthologous across most birds. This situation contrasts with the conservation of other aspects of regional variation in gene expression observed on the avian sex chromosomes but could be the result of sampling bias. We sampled taxa across the Galloanserae, an avian clade spanning 90 million years, to test whether regional variation in sex-specific gene regulation across the Z chromosome is conserved. We show that the MHM region is conserved across a large portion of the avian phylogeny, together with other sex-specific regulatory features of the avian Z chromosome. Our results from multiple lines of evidence suggest that the sex-specific expression pattern of the MHM region is not consistent with nascent dosage compensation. PMID:26245831

  3. The evolution of sex chromosomes in organisms with separate haploid sexes.

    PubMed

    Immler, Simone; Otto, Sarah Perin

    2015-03-01

    The evolution of dimorphic sex chromosomes is driven largely by the evolution of reduced recombination and the subsequent accumulation of deleterious mutations. Although these processes are increasingly well understood in diploid organisms, the evolution of dimorphic sex chromosomes in haploid organisms (U/V) has been virtually unstudied theoretically. We analyze a model to investigate the evolution of linkage between fitness loci and the sex-determining region in U/V species. In a second step, we test how prone nonrecombining regions are to degeneration due to accumulation of deleterious mutations. Our modeling predicts that the decay of recombination on the sex chromosomes and the addition of strata via fusions will be just as much a part of the evolution of haploid sex chromosomes as in diploid sex chromosome systems. Reduced recombination is broadly favored, as long as there is some fitness difference between haploid males and females. The degeneration of the sex-determining region due to the accumulation of deleterious mutations is expected to be slower in haploid organisms because of the absence of masking. Nevertheless, balancing selection often drives greater differentiation between the U/V sex chromosomes than in X/Y and Z/W systems. We summarize empirical evidence for haploid sex chromosome evolution and discuss our predictions in light of these findings. © 2015 The Author(s).

  4. Sex-chromosome turnovers: the hot-potato model.

    PubMed

    Blaser, Olivier; Neuenschwander, Samuel; Perrin, Nicolas

    2014-01-01

    Sex-determining systems often undergo high rates of turnover but for reasons that remain largely obscure. Two recent evolutionary models assign key roles, respectively, to sex-antagonistic (SA) mutations occurring on autosomes and to deleterious mutations accumulating on sex chromosomes. These two models capture essential but distinct key features of sex-chromosome evolution; accordingly, they make different predictions and present distinct limitations. Here we show that a combination of features from the two models has the potential to generate endless cycles of sex-chromosome transitions: SA alleles accruing on a chromosome after it has been co-opted for sex induce an arrest of recombination; the ensuing accumulation of deleterious mutations will soon make a new transition ineluctable. The dynamics generated by these interactions share several important features with empirical data, namely, (i) that patterns of heterogamety tend to be conserved during transitions and (ii) that autosomes are not recruited randomly, with some chromosome pairs more likely than others to be co-opted for sex.

  5. Homomorphic plant sex chromosomes are coming of age.

    PubMed

    Filatov, Dmitry A

    2015-07-01

    Sex chromosomes are a very peculiar part of the genome that have evolved independently in many groups of animals and plants (Bull ). Major research efforts have so far been focused on large heteromorphic sex chromosomes in a few animal and plant species (Chibalina & Filatov ; Zhou & Bachtrog ; Bellott et al. ; Hough et al. ; Zhou et al. ), while homomorphic (cytologically indistinguishable) sex chromosomes have largely been neglected. However, this situation is starting to change. In this issue, Geraldes et al. () describe a small (~100 kb long) sex-determining region on the homomorphic sex chromosomes of poplars (Populus trichocarpa and related species, Fig. ). All species in Populus and its sister genus Salix are dioecious, suggesting that dioecy and the sex chromosomes, if any, should be relatively old. Contrary to this expectation, Geraldes et al. () demonstrate that the sex-determining region in poplars is of very recent origin and probably evolved within the genus Populus only a few million years ago.

  6. Evolution of multiple sex chromosomes in the spider genus Malthonica (Araneae: Agelenidae) indicates unique structure of the spider sex chromosome systems.

    PubMed

    Král, Jirí

    2007-01-01

    Most spiders exhibit a multiple sex chromosome system, X(1)X(2)0, whose origin has not been satisfactorily explained. Examination of the sex chromosome systems in the spider genus Malthonica (Agelenidae) revealed considerable diversity in sex chromosome constitution within this group. Besides modes X(1)X(2)0 (M. silvestris) and X(1)X(2)X(3)0 (M. campestris), a neo-X(1)X(2)X(3)X(4)X(5)Y system in M. ferruginea was found. Ultrastructural analysis of spread pachytene spermatocytes revealed that the X(1)X(2)0 and X(1)X(2)X(3)0 systems include a pair of homomorphic sex chromosomes. Multiple X chromosomes and the pair exhibit an end-to-end pairing, being connected by attachment plaques. The X(1)X(2)X(3)X(4)X(5)Y system of M. ferruginea arose by rearrangement between the homomorphic sex chromosome pair and an autosome. Multiple X chromosomes and the sex chromosome pair do not differ from autosomes in a pattern of constitutive heterochromatin. Ultrastructural data on sex chromosome pairing in other spiders indicate that the homomorphic sex chromosome pair forms an integral part of the spider sex chromosome systems. It is suggested that this pair represents ancestral sex chromosomes of spiders, which generated multiple X chromosomes by non-disjunctions. Structural differentiation of newly formed X chromosomes has been facilitated by heterochromatinization of sex chromosome bivalents observed in prophase I of spider females.

  7. Sex-specific embryonic gene expression in species with newly evolved sex chromosomes.

    PubMed

    Lott, Susan E; Villalta, Jacqueline E; Zhou, Qi; Bachtrog, Doris; Eisen, Michael B

    2014-02-01

    Sex chromosome dosage differences between females and males are a significant form of natural genetic variation in many species. Like many species with chromosomal sex determination, Drosophila females have two X chromosomes, while males have one X and one Y. Fusions of sex chromosomes with autosomes have occurred along the lineage leading to D. pseudoobscura and D. miranda. The resulting neo-sex chromosomes are gradually evolving the properties of sex chromosomes, and neo-X chromosomes are becoming targets for the molecular mechanisms that compensate for differences in X chromosome dose between sexes. We have previously shown that D. melanogaster possess at least two dosage compensation mechanisms: the well- characterized MSL-mediated dosage compensation active in most somatic tissues, and another system active during early embryogenesis prior to the onset of MSL-mediated dosage compensation. To better understand the developmental constraints on sex chromosome gene expression and evolution, we sequenced mRNA from individual male and female embryos of D. pseudoobscura and D. miranda, from ∼0.5 to 8 hours of development. Autosomal expression levels are highly conserved between these species. But, unlike D. melanogaster, we observe a general lack of dosage compensation in D. pseudoobscura and D. miranda prior to the onset of MSL-mediated dosage compensation. Thus, either there has been a lineage-specific gain or loss in early dosage compensation mechanism(s) or increasing X chromosome dose may strain dosage compensation systems and make them less effective. The extent of female bias on the X chromosomes decreases through developmental time with the establishment of MSL-mediated dosage compensation, but may do so more slowly in D. miranda than D. pseudoobscura. These results also prompt a number of questions about whether species with more sex-linked genes have more sex-specific phenotypes, and how much transcript level variance is tolerable during critical stages

  8. Homomorphic sex chromosomes and the intriguing Y chromosome of Ctenomys rodent species (Rodentia, Ctenomyidae).

    PubMed

    Suárez-Villota, Elkin Y; Pansonato-Alves, José C; Foresti, Fausto; Gallardo, Milton H

    2014-01-01

    Unlike the X chromosome, the mammalian Y chromosome undergoes evolutionary decay resulting in small size. This sex chromosomal heteromorphism, observed in most species of the fossorial rodent Ctenomys, contrasts with the medium-sized, homomorphic acrocentric sex chromosomes of closely related C. maulinus and C. sp. To characterize the sequence composition of these chromosomes, fluorescent banding, self-genomic in situ hybridization, and fluorescent in situ hybridization with an X painting probe were performed on mitotic and meiotic plates. High molecular homology between the sex chromosomes was detected on mitotic material as well as on meiotic plates immunodetected with anti-SYCP3 and anti-γH2AX. The Y chromosome is euchromatic, poor in repetitive sequences and differs from the X by the loss of a block of pericentromeric chromatin. Inferred from the G-banding pattern, an inversion and the concomitant prevention of recombination in a large asynaptic region seems to be crucial for meiotic X chromosome inactivation. These peculiar findings together with the homomorphism of Ctenomys sex chromosomes are discussed in the light of the regular purge that counteracts Muller's ratchet and the probable mechanisms accounting for their origin and molecular homology.

  9. Sex chromosomes: platypus genome suggests a recent origin for the human X.

    PubMed

    Ellegren, Hans

    2008-07-08

    The unusual sex chromosomes of platypus are not homologous to the human X and Y chromosomes, implying that the sex chromosomes of placental mammals evolved after the monotreme and placental mammal lineages split about 165 million years ago.

  10. The sex-specific region of sex chromosomes in animals and plants.

    PubMed

    Gschwend, Andrea R; Weingartner, Laura A; Moore, Richard C; Ming, Ray

    2012-01-01

    Our understanding of the evolution of sex chromosomes has increased greatly in recent years due to a number of molecular evolutionary investigations in divergent sex chromosome systems, and these findings are reshaping theories of sex chromosome evolution. In particular, the dynamics of the sex-determining region (SDR) have been demonstrated by recent findings in ancient and incipient sex chromosomes. Radical changes in genomic structure and gene content in the male specific region of the Y chromosome between human and chimpanzee indicated rapid evolution in the past 6 million years, defying the notion that the pace of evolution in the SDR was fast at early stages but slowed down overtime. The chicken Z and the human X chromosomes appeared to have acquired testis-expressed genes and expanded in intergenic regions. Transposable elements greatly contributed to SDR expansion and aided the trafficking of genes in the SDR and its X or Z counterpart through retrotransposition. Dosage compensation is not a destined consequence of sex chromosomes as once thought. Most X-linked microRNA genes escape silencing and are expressed in testis. Collectively, these findings are challenging many of our preconceived ideas of the evolutionary trajectory and fates of sex chromosomes.

  11. Impact of repetitive DNA on sex chromosome evolution in plants.

    PubMed

    Hobza, Roman; Kubat, Zdenek; Cegan, Radim; Jesionek, Wojciech; Vyskot, Boris; Kejnovsky, Eduard

    2015-09-01

    Structurally and functionally diverged sex chromosomes have evolved in many animals as well as in some plants. Sex chromosomes represent a specific genomic region(s) with locally suppressed recombination. As a consequence, repetitive sequences involving transposable elements, tandem repeats (satellites and microsatellites), and organellar DNA accumulate on the Y (W) chromosomes. In this paper, we review the main types of repetitive elements, their gathering on the Y chromosome, and discuss new findings showing that not only accumulation of various repeats in non-recombining regions but also opposite processes form Y chromosome. The aim of this review is also to discuss the mechanisms of repetitive DNA spread involving (retro) transposition, DNA polymerase slippage or unequal crossing-over, as well as modes of repeat removal by ectopic recombination. The intensity of these processes differs in non-recombining region(s) of sex chromosomes when compared to the recombining parts of genome. We also speculate about the relationship between heterochromatinization and the formation of heteromorphic sex chromosomes.

  12. The Sex Chromosomes of Frogs: Variability and Tolerance Offer Clues to Genome Evolution and Function

    PubMed Central

    Malcom, Jacob W.; Kudra, Randal S.; Malone, John H.

    2014-01-01

    Frog sex chromosomes offer an ideal system for advancing our understanding of genome evolution and function because of the variety of sex determination systems in the group, the diversity of sex chromosome maturation states, the ease of experimental manipulation during early development. After briefly reviewing sex chromosome biology generally, we focus on what is known about frog sex determination, sex chromosome evolution, and recent, genomics-facilitated advances in the field. In closing we highlight gaps in our current knowledge of frog sex chromosomes, and suggest priorities for future research that can advance broad knowledge of gene dose and sex chromosome evolution. PMID:25031658

  13. Sex without sex chromosomes: genetic architecture of multiple loci independently segregating to determine sex ratios in the copepod Tigriopus californicus.

    PubMed

    Alexander, H J; Richardson, J M L; Edmands, S; Anholt, B R

    2015-12-01

    Sex-determining systems are remarkably diverse and may evolve rapidly. Polygenic sex-determination systems are predicted to be transient and evolutionarily unstable, yet examples have been reported across a range of taxa. Here, we provide the first direct evidence of polygenic sex determination in Tigriopus californicus, a harpacticoid copepod with no heteromorphic sex chromosomes. Using genetically distinct inbred lines selected for male- and female-biased clutches, we generated a genetic map with 39 SNPs across 12 chromosomes. Quantitative trait locus mapping of sex ratio phenotype (the proportion of male offspring produced by an F2 female) in four F2 families revealed six independently segregating quantitative trait loci on five separate chromosomes, explaining 19% of the variation in sex ratios. The sex ratio phenotype varied among loci across chromosomes in both direction and magnitude, with the strongest phenotypic effects on chromosome 10 moderated to some degree by loci on four other chromosomes. For a given locus, sex ratio phenotype varied in magnitude for individuals derived from different dam lines. These data, together with the environmental factors known to contribute to sex determination, characterize the underlying complexity and potential lability of sex determination, and confirm the polygenic architecture of sex determination in T. californicus.

  14. Mammalian X homolog acts as sex chromosome in lacertid lizards

    PubMed Central

    Rovatsos, M; Vukić, J; Kratochvíl, L

    2016-01-01

    Among amniotes, squamate reptiles are especially variable in their mechanisms of sex determination; however, based largely on cytogenetic data, some lineages possess highly evolutionary stable sex chromosomes. The still very limited knowledge of the genetic content of squamate sex chromosomes precludes a reliable reconstruction of the evolutionary history of sex determination in this group and consequently in all amniotes. Female heterogamety with a degenerated W chromosome typifies the lizards of the family Lacertidae, the widely distributed Old World clade including several hundreds of species. From the liver transcriptome of the lacertid Takydromus sexlineatus female, we selected candidates for Z-specific genes as the loci lacking single-nucleotide polymorphisms. We validated the candidate genes through the comparison of the copy numbers in the female and male genomes of T. sexlineatus and another lacertid species, Lacerta agilis, by quantitative PCR that also proved to be a reliable technique for the molecular sexing of the studied species. We suggest that this novel approach is effective for the detection of Z-specific and X-specific genes in lineages with degenerated W, respectively Y chromosomes. The analyzed gene content of the Z chromosome revealed that lacertid sex chromosomes are not homologous with those of other reptiles including birds, but instead the genes have orthologs in the X-conserved region shared by viviparous mammals. It is possible that this part of the vertebrate genome was independently co-opted for the function of sex chromosomes in viviparous mammals and lacertids because of its content of genes involved in gonad differentiation. PMID:26980341

  15. Mammalian X homolog acts as sex chromosome in lacertid lizards.

    PubMed

    Rovatsos, M; Vukić, J; Kratochvíl, L

    2016-07-01

    Among amniotes, squamate reptiles are especially variable in their mechanisms of sex determination; however, based largely on cytogenetic data, some lineages possess highly evolutionary stable sex chromosomes. The still very limited knowledge of the genetic content of squamate sex chromosomes precludes a reliable reconstruction of the evolutionary history of sex determination in this group and consequently in all amniotes. Female heterogamety with a degenerated W chromosome typifies the lizards of the family Lacertidae, the widely distributed Old World clade including several hundreds of species. From the liver transcriptome of the lacertid Takydromus sexlineatus female, we selected candidates for Z-specific genes as the loci lacking single-nucleotide polymorphisms. We validated the candidate genes through the comparison of the copy numbers in the female and male genomes of T. sexlineatus and another lacertid species, Lacerta agilis, by quantitative PCR that also proved to be a reliable technique for the molecular sexing of the studied species. We suggest that this novel approach is effective for the detection of Z-specific and X-specific genes in lineages with degenerated W, respectively Y chromosomes. The analyzed gene content of the Z chromosome revealed that lacertid sex chromosomes are not homologous with those of other reptiles including birds, but instead the genes have orthologs in the X-conserved region shared by viviparous mammals. It is possible that this part of the vertebrate genome was independently co-opted for the function of sex chromosomes in viviparous mammals and lacertids because of its content of genes involved in gonad differentiation.

  16. Sex chromosome effects unmasked in angiotensin II-induced hypertension

    PubMed Central

    Ji, Hong; Zheng, Wei; Wu, Xie; Liu, Jun; Ecelbarger, Carolyn M.; Watkins, Rebecca; Arnold, Arthur P.; Sandberg, Kathryn

    2010-01-01

    Sex differences in mean arterial pressure (MAP) are reported in many experimental models of hypertension and are ascribed to gonadal sex based of studies showing gonadectomy and gonadal hormone replacement affect MAP. The interpretation of these studies, however, has been confounded by differences in the sex chromosome complement (XX vs. XY). To investigate the sex chromosome complement independently of gonadal sex, we used the four core genotype (FCG) mouse model in which gonadal sex is separated from the sex chromosome complement enabling comparisons among XX and XY females and XX and XY males. We found that in the gonadectomized (GDX) FCG, MAP after 2 weeks of angiotensin II (Ang II) infusion (200 ng/kg/min) was greater in XX than XY [MAP (mm Hg): GDX-XX-Female, 148±4.5; GDX-XY-Female, 133±4.4; GDX-XX-Male, 149±9.4; GDX-XY-Male, 138±5.5; p<0.03, XX vs XY; n=8-9/grp]. In contrast, no sex chromosome effects (SCE) were found on heart rate (HR) body weight (BW) or plasma Ang II 2 weeks after Ang II infusion. This study suggests that in addition to effects of gonadal hormones on blood pressure, X- or Y-linked genes, parental imprinting or X mosaicism contribute to sex differences in hypertension. Furthermore, the finding that MAP was greater in XX mice compared to XY mice in the GDX state suggests adverse SCE encoded within the XX sex chromosome complement could contribute to hypertension in women with ovarian hormone deficiency such as postmenopausal women and women with premature ovarian failure. PMID:20231528

  17. Cross-species chromosome painting tracks the independent origin of multiple sex chromosomes in two cofamiliar Erythrinidae fishes.

    PubMed

    Cioffi, Marcelo B; Sánchez, Antonio; Marchal, Juan A; Kosyakova, Nadezda; Liehr, Thomas; Trifonov, Vladimir; Bertollo, Luiz Ac

    2011-06-30

    The Erythrinidae fish family is characterized by a large variation with respect to diploid chromosome numbers and sex-determining systems among its species, including two multiple X1X2Y sex systems in Hoplias malabaricus and Erythrinus erythrinus. At first, the occurrence of a same sex chromosome system within a family suggests that the sex chromosomes are correlated and originated from ancestral XY chromosomes that were either homomorphic or at an early stage of differentiation. To identify the origin and evolution of these X1X2Y sex chromosomes, we performed reciprocal cross-species FISH experiments with two sex-chromosome-specific probes designed from microdissected X1 and Y chromosomes of H. malabaricus and E. erythrinus, respectively. Our results yield valuable information regarding the origin and evolution of these sex chromosome systems. Our data indicate that these sex chromosomes evolved independently in these two closed related Erythrinidae species. Different autosomes were first converted into a poorly differentiated XY sex pair in each species, and additional chromosomal rearrangements produced both X1X2Y sex systems that are currently present. Our data provide new insights into the origin and evolution of sex chromosomes, which increases our knowledge about fish sex chromosome evolution.

  18. Meiotic chromosomes and stages of sex chromosome evolution in fish: zebrafish, platyfish and guppy.

    PubMed

    Traut, W; Winking, H

    2001-01-01

    We describe SC complements and results from comparative genomic hybridization (CGH) on mitotic and meiotic chromosomes of the zebrafish Danio rerio, the platyfish Xiphophorus maculatus and the guppy Poecilia reticulata. The three fish species represent basic steps of sex chromosome differentiation: (1) the zebrafish with an all-autosome karyotype; (2) the platyfish with genetically defined sex chromosomes but no differentiation between X and Y visible in the SC or with CGH in meiotic and mitotic chromosomes; (3) the guppy with genetically and cytogenetically differentiated sex chromosomes. The acrocentric Y chromosomes of the guppy consists of a proximal homologous and a distal differential segment. The proximal segment pairs in early pachytene with the respective X chromosome segment. The differential segment is unpaired in early pachytene but synapses later in an 'adjustment' or 'equalization' process. The segment includes a postulated sex determining region and a conspicuous variable heterochromatic region whose structure depends on the particular Y chromosome line. CGH differentiates a large block of predominantly male-specific repetitive DNA and a block of common repetitive DNA in that region.

  19. Stable Cretaceous sex chromosomes enable molecular sexing in softshell turtles (Testudines: Trionychidae)

    PubMed Central

    Rovatsos, Michail; Praschag, Peter; Fritz, Uwe; Kratochvšl, Lukáš

    2017-01-01

    Turtles demonstrate variability in sex determination ranging from environmental sex determination (ESD) to highly differentiated sex chromosomes. However, the evolutionary dynamics of sex determining systems in this group is not well known. Differentiated ZZ/ZW sex chromosomes were identified in two species of the softshell turtles (Trionychidae) from the subfamily Trionychinae and Z-specific genes were identified in a single species. We tested Z-specificity of a subset of these genes by quantitative PCR comparing copy gene numbers in male and female genomes in 10 species covering the phylogenetic diversity of trionychids. We demonstrated that differentiated ZZ/ZW sex chromosomes are conserved across the whole family and that they were already present in the common ancestor of the extant trionychids. As the sister lineage, Carettochelys insculpta, possess ESD, we can date the origin of the sex chromosomes in trionychids between 200 Mya (split of Trionychidae and Carettochelyidae) and 120 Mya (basal splitting of the recent trionychids). The results support the evolutionary stability of differentiated sex chromosomes in some lineages of ectothermic vertebrates. Moreover, our approach determining sex-linkage of protein coding genes can be used as a reliable technique of molecular sexing across trionychids useful for effective breeding strategy in conservation projects of endangered species. PMID:28186115

  20. Stable Cretaceous sex chromosomes enable molecular sexing in softshell turtles (Testudines: Trionychidae).

    PubMed

    Rovatsos, Michail; Praschag, Peter; Fritz, Uwe; Kratochvšl, Lukáš

    2017-02-10

    Turtles demonstrate variability in sex determination ranging from environmental sex determination (ESD) to highly differentiated sex chromosomes. However, the evolutionary dynamics of sex determining systems in this group is not well known. Differentiated ZZ/ZW sex chromosomes were identified in two species of the softshell turtles (Trionychidae) from the subfamily Trionychinae and Z-specific genes were identified in a single species. We tested Z-specificity of a subset of these genes by quantitative PCR comparing copy gene numbers in male and female genomes in 10 species covering the phylogenetic diversity of trionychids. We demonstrated that differentiated ZZ/ZW sex chromosomes are conserved across the whole family and that they were already present in the common ancestor of the extant trionychids. As the sister lineage, Carettochelys insculpta, possess ESD, we can date the origin of the sex chromosomes in trionychids between 200 Mya (split of Trionychidae and Carettochelyidae) and 120 Mya (basal splitting of the recent trionychids). The results support the evolutionary stability of differentiated sex chromosomes in some lineages of ectothermic vertebrates. Moreover, our approach determining sex-linkage of protein coding genes can be used as a reliable technique of molecular sexing across trionychids useful for effective breeding strategy in conservation projects of endangered species.

  1. Organelle DNA accumulation in the recently evolved papaya sex chromosomes.

    PubMed

    VanBuren, Robert; Ming, Ray

    2013-06-01

    Sex chromosomes are a pair of specialized chromosomes containing a sex determination region that is suppressed for recombination. Without recombination, Y chromosomes are thought to accumulate repetitive DNA sequences which contribute to their degeneration. A pair of primitive sex chromosomes controls sex type in papaya with male and hermaphrodite determined by the slightly different male-specific region of the Y (MSY) and hermaphrodite-specific region of Y(h) (HSY) chromosomes, respectively. Here, we show that the papaya HSY and MSY in the absence of recombination have accumulated nearly 12 times the amount of chloroplast-derived DNA than the corresponding region of the X chromosome and 4 times the papaya genome-wide average. Furthermore, a chloroplast genome fragment containing the rsp15 gene has been amplified 23 times in the HSY, evidence of retrotransposon-mediated duplication. Surprisingly, mitochondria-derived sequences are less abundant in the X and HSY compared to the whole genome. Shared organelle integrations are sparse between X and HSY, with only 11 % of chloroplast and 12 % of mitochondria fragments conserved, respectively, suggesting that the accelerated accumulation of organelle DNA occurred after the HSY was suppressed for recombination. Most of the organelle-derived sequences have divergence times of <7 MYA, reinforcing this notion. The accumulated chloroplast DNA is evidence of the slow degeneration of the HSY.

  2. The influence of sex chromosome aneuploidy on brain asymmetry.

    PubMed

    Rezaie, Roozbeh; Daly, Eileen M; Cutter, William J; Murphy, Declan G M; Robertson, Dene M W; DeLisi, Lynn E; Mackay, Clare E; Barrick, Thomas R; Crow, Timothy J; Roberts, Neil

    2009-01-05

    The cognitive deficits present in individuals with sex chromosome aneuploidies suggest that hemispheric differentiation of function is determined by an X-Y homologous gene [Crow (1993); Lancet 342:594-598]. In particular, females with Turner's syndrome (TS) who have only one X-chromosome exhibit deficits of spatial ability whereas males with Klinefelter's syndrome (KS) who possess a supernumerary X-chromosome are delayed in acquiring words. Since spatial and verbal abilities are generally associated with right and left hemispheric function, such deficits may relate to anomalies of cerebral asymmetry. We therefore applied a novel image analysis technique to investigate the relationship between sex chromosome dosage and structural brain asymmetry. Specifically, we tested Crow's prediction that the magnitude of the brain torque (i.e., a combination of rightward frontal and leftward occipital asymmetry) would, as a function of sex chromosome dosage, be respectively decreased in TS women and increased in KS men, relative to genotypically normal controls. We found that brain torque was not significantly different in TS women and KS men, in comparison to controls. However, TS women exhibited significantly increased leftward brain asymmetry, restricted to the posterior of the brain and focused on the superior temporal and parietal-occipital association cortex, while KS men showed a trend for decreased brain asymmetry throughout the frontal lobes. The findings suggest that the number of sex chromosomes influences the development of brain asymmetry not simply to modify the torque but in a complex pattern along the antero-posterior axis.

  3. Male breast cancer, age and sex chromosome aneuploidy

    PubMed Central

    Jacobs, P A; Maloney, V; Cooke, R; Crolla, J A; Ashworth, A; Swerdlow, A J

    2013-01-01

    Background: In cultured, dividing transformed T lymphocytes and in dividing bone marrow cells from normal men and those with a haematological malignancy, sex chromosome aneuploidy has been found to increase in prevalence and degree with age. This has rarely been investigated in non-dividing uncultured blood samples. The loss and gain of the X chromosome in dividing transformed lymphocytes in women with age is much more frequent than that of the Y chromosome in males. However, paradoxically X chromosome aneuploidy is rarely seen in the dividing cells of bone marrow of females. Methods: In blood samples from 565 men with breast cancer and 54 control men from the England and Wales general population, 80 cell nuclei per sample were scored for presence of X and Y chromosomes using fluorescent centromeric probes. Results: Sex chromosome aneuploidy, largely Y chromosome loss, was present in 63% of cases and 57% of controls, with the prevalence and degree of aneuploidy increasingly sharply and highly significantly with age. At ages 65–80 years, 71% of cases and 85% of controls showed aneuploidy and 15% and 25%, respectively, had ⩾10% of cells aneuploid. Allowing for age, aneuploidy was less prevalent (P=0.03) in cases than controls. Conclusion: Sex chromosome aneuploidy in non-dividing nuclei of peripheral blood cells is frequent in adult men, the prevalence and degree increasing sharply with age. The possible relation of sex chromosome aneuploidy to breast cancer risk in men, and to cancer risk generally, needs further investigation, ideally in cohort studies. PMID:23299533

  4. Selective maintenance of recombination between the sex chromosomes.

    PubMed

    Otto, S P

    2014-07-01

    A hallmark of many sex chromosomes is the dramatically reduced rate of recombination between them in the heterogametic sex (e.g. between the X and Y). Sexually antagonistic selection is thought to be the main selective driver of this reduced recombination, with tighter linkage strengthening the association between alleles favourable to females and the X, as well as alleles favourable to males and the Y. Nevertheless, many sex chromosomes retain substantial levels of recombination over millions of years, and some old sex chromosomes remain homomorphic with few signs of recombination suppression and the chromosomal degradation expected to follow. This paper explores the selective factors that can maintain recombination between the sex chromosomes. Specifically, by analysing the dynamics of genes that modify the rate of recombination, I present results demonstrating that certain forms of selection - all involving overdominance in males - can positively maintain recombination in the pseudo-autosomal region. To understand these cases, one has to revise our standard view of sexual antagonistic selection as involving two partners (males and females) to three partners (the X in females, the X in males and the Y).

  5. Higher levels of sex chromosome heteromorphism are associated with markedly stronger reproductive isolation.

    PubMed

    Lima, Thiago G

    2014-08-21

    The two 'rules of speciation', Haldane's rule and the large X-effect, describe the genetic basis of postzygotic isolation, and have led to the realization that sex chromosomes play an important role in this process. However, a range of sex determination mechanisms exists in nature, not always involving sex chromosomes. Based on these 'rules of speciation', I test the hypothesis that the presence of sex chromosomes will contribute to a faster evolution of intrinsic postzygotic isolation. I show that taxa that do not have sex chromosomes evolve lower levels of postzygotic isolation than taxa with sex chromosomes, at a similar amount of genetic divergence. Taxa with young homomorphic sex chromosomes show an intermediate pattern compared to taxa with heteromorphic sex chromosomes and taxa without sex chromosomes. These results are consistent with predictions from the two 'rules of speciation', and emphasize the importance of sex chromosomes for the evolution of intrinsic postzygotic isolation.

  6. Genome structure and primitive sex chromosome revealed in Populus

    SciTech Connect

    Tuskan, Gerald A; Yin, Tongming; Gunter, Lee E; Blaudez, D

    2008-01-01

    We constructed a comprehensive genetic map for Populus and ordered 332 Mb of sequence scaffolds along the 19 haploid chromosomes in order to compare chromosomal regions among diverse members of the genus. These efforts lead us to conclude that chromosome XIX in Populus is evolving into a sex chromosome. Consistent segregation distortion in favor of the sub-genera Tacamahaca alleles provided evidence of divergent selection among species, particularly at the proximal end of chromosome XIX. A large microsatellite marker (SSR) cluster was detected in the distorted region even though the genome-wide distribute SSR sites was uniform across the physical map. The differences between the genetic map and physical sequence data suggested recombination suppression was occurring in the distorted region. A gender-determination locus and an overabundance of NBS-LRR genes were also co-located to the distorted region and were put forth as the cause for divergent selection and recombination suppression. This hypothesis was verified by using fine-scale mapping of an integrated scaffold in the vicinity of the gender-determination locus. As such it appears that chromosome XIX in Populus is in the process of evolving from an autosome into a sex chromosome and that NBS-LRR genes may play important role in the chromosomal diversification process in Populus.

  7. Key features of the X inactivation process are conserved between marsupials and eutherians.

    PubMed

    Mahadevaiah, Shantha K; Royo, Helene; VandeBerg, John L; McCarrey, John R; Mackay, Sarah; Turner, James M A

    2009-09-15

    In female marsupials, X chromosome inactivation (XCI) is imprinted, affecting the paternal X chromosome. One model, supported by recent studies, proposes that XCI in marsupials is achieved through inheritance of an already silent X chromosome from the father, with XCI initiated by meiotic sex chromosome inactivation (MSCI). This model is appealing because marsupials have no Xist gene and the marsupial inactive X chromosome is epigenetically dissimilar to that of mice, apparently lacking repressive histone marks such as H3K27 trimethylation. A central prediction of the meiotic inactivation model of XCI is that silencing of genes on the X chromosome, initiated during male meiosis, is stably maintained during subsequent spermiogenesis. Here we characterize XCI in the male germline and female soma of the marsupial Monodelphis domestica. Contrary to the meiotic inactivation model, we find that X genes silenced by MSCI are reactivated after meiosis and are subsequently inactivated in the female. A reexamination of the female somatic inactive marsupial X chromosome reveals that it does share common properties with that of eutherians, including H3K27 trimethylation and targeting to the perinucleolar compartment. We conclude that aspects of the XCI process are more highly conserved in therian mammals than previously thought.

  8. Neo-sex chromosomes and adaptive potential in tortricid pests

    PubMed Central

    Nguyen, Petr; Sýkorová, Miroslava; Šíchová, Jindra; Kůta, Václav; Dalíková, Martina; Čapková Frydrychová, Radmila; Neven, Lisa G.; Sahara, Ken; Marec, František

    2013-01-01

    Changes in genome architecture often have a significant effect on ecological specialization and speciation. This effect may be further enhanced by involvement of sex chromosomes playing a disproportionate role in reproductive isolation. We have physically mapped the Z chromosome of the major pome fruit pest, the codling moth, Cydia pomonella (Tortricidae), and show that it arose by fusion between an ancestral Z chromosome and an autosome corresponding to chromosome 15 in the Bombyx mori reference genome. We further show that the fusion originated in a common ancestor of the main tortricid subfamilies, Olethreutinae and Tortricinae, comprising almost 700 pest species worldwide. The Z–autosome fusion brought two major genes conferring insecticide resistance and clusters of genes involved in detoxification of plant secondary metabolites under sex-linked inheritance. We suggest that this fusion significantly increased the adaptive potential of tortricid moths and thus contributed to their radiation and subsequent speciation. PMID:23569222

  9. Sequencing papaya X and Yh chromosomes reveals molecular basis of incipient sex chromosome evolution.

    PubMed

    Wang, Jianping; Na, Jong-Kuk; Yu, Qingyi; Gschwend, Andrea R; Han, Jennifer; Zeng, Fanchang; Aryal, Rishi; VanBuren, Robert; Murray, Jan E; Zhang, Wenli; Navajas-Pérez, Rafael; Feltus, F Alex; Lemke, Cornelia; Tong, Eric J; Chen, Cuixia; Wai, Ching Man; Singh, Ratnesh; Wang, Ming-Li; Min, Xiang Jia; Alam, Maqsudul; Charlesworth, Deborah; Moore, Paul H; Jiang, Jiming; Paterson, Andrew H; Ming, Ray

    2012-08-21

    Sex determination in papaya is controlled by a recently evolved XY chromosome pair, with two slightly different Y chromosomes controlling the development of males (Y) and hermaphrodites (Y(h)). To study the events of early sex chromosome evolution, we sequenced the hermaphrodite-specific region of the Y(h) chromosome (HSY) and its X counterpart, yielding an 8.1-megabase (Mb) HSY pseudomolecule, and a 3.5-Mb sequence for the corresponding X region. The HSY is larger than the X region, mostly due to retrotransposon insertions. The papaya HSY differs from the X region by two large-scale inversions, the first of which likely caused the recombination suppression between the X and Y(h) chromosomes, followed by numerous additional chromosomal rearrangements. Altogether, including the X and/or HSY regions, 124 transcription units were annotated, including 50 functional pairs present in both the X and HSY. Ten HSY genes had functional homologs elsewhere in the papaya autosomal regions, suggesting movement of genes onto the HSY, whereas the X region had none. Sequence divergence between 70 transcripts shared by the X and HSY revealed two evolutionary strata in the X chromosome, corresponding to the two inversions on the HSY, the older of which evolved about 7.0 million years ago. Gene content differences between the HSY and X are greatest in the older stratum, whereas the gene content and order of the collinear regions are identical. Our findings support theoretical models of early sex chromosome evolution.

  10. Sequencing papaya X and Yh chromosomes reveals molecular basis of incipient sex chromosome evolution

    PubMed Central

    Wang, Jianping; Na, Jong-Kuk; Yu, Qingyi; Gschwend, Andrea R.; Han, Jennifer; Zeng, Fanchang; Aryal, Rishi; VanBuren, Robert; Murray, Jan E.; Zhang, Wenli; Navajas-Pérez, Rafael; Feltus, F. Alex; Lemke, Cornelia; Tong, Eric J.; Chen, Cuixia; Man Wai, Ching; Singh, Ratnesh; Wang, Ming-Li; Min, Xiang Jia; Alam, Maqsudul; Charlesworth, Deborah; Moore, Paul H.; Jiang, Jiming; Paterson, Andrew H.; Ming, Ray

    2012-01-01

    Sex determination in papaya is controlled by a recently evolved XY chromosome pair, with two slightly different Y chromosomes controlling the development of males (Y) and hermaphrodites (Yh). To study the events of early sex chromosome evolution, we sequenced the hermaphrodite-specific region of the Yh chromosome (HSY) and its X counterpart, yielding an 8.1-megabase (Mb) HSY pseudomolecule, and a 3.5-Mb sequence for the corresponding X region. The HSY is larger than the X region, mostly due to retrotransposon insertions. The papaya HSY differs from the X region by two large-scale inversions, the first of which likely caused the recombination suppression between the X and Yh chromosomes, followed by numerous additional chromosomal rearrangements. Altogether, including the X and/or HSY regions, 124 transcription units were annotated, including 50 functional pairs present in both the X and HSY. Ten HSY genes had functional homologs elsewhere in the papaya autosomal regions, suggesting movement of genes onto the HSY, whereas the X region had none. Sequence divergence between 70 transcripts shared by the X and HSY revealed two evolutionary strata in the X chromosome, corresponding to the two inversions on the HSY, the older of which evolved about 7.0 million years ago. Gene content differences between the HSY and X are greatest in the older stratum, whereas the gene content and order of the collinear regions are identical. Our findings support theoretical models of early sex chromosome evolution. PMID:22869747

  11. MDC1 directs chromosome-wide silencing of the sex chromosomes in male germ cells.

    PubMed

    Ichijima, Yosuke; Ichijima, Misako; Lou, Zhenkun; Nussenzweig, André; Camerini-Otero, R Daniel; Chen, Junjie; Andreassen, Paul R; Namekawa, Satoshi H

    2011-05-01

    Chromosome-wide inactivation is an epigenetic signature of sex chromosomes. The mechanism by which the chromosome-wide domain is recognized and gene silencing is induced remains unclear. Here we identify an essential mechanism underlying the recognition of the chromosome-wide domain in the male germline. We show that mediator of DNA damage checkpoint 1 (MDC1), a binding partner of phosphorylated histone H2AX (γH2AX), defines the chromosome-wide domain, initiates meiotic sex chromosome inactivation (MSCI), and leads to XY body formation. Importantly, MSCI consists of two genetically separable steps. The first step is the MDC1-independent recognition of the unsynapsed axis by DNA damage response (DDR) factors such as ataxia telangiectasia and Rad3-related (ATR), TOPBP1, and γH2AX. The second step is the MDC1-dependent chromosome-wide spreading of DDR factors to the entire chromatin. Furthermore, we demonstrate that, in somatic cells, MDC1-dependent amplification of the γH2AX signal occurs following replicative stress and is associated with transcriptional silencing. We propose that a common DDR pathway underlies both MSCI and the response of somatic cells to replicative stress. These results establish that the DDR pathway centered on MDC1 triggers epigenetic silencing of sex chromosomes in germ cells.

  12. The evolution of sex chromosomes in the genus Rumex (Polygonaceae): Identification of a new species with heteromorphic sex chromosomes.

    PubMed

    Cuñado, Nieves; Navajas-Pérez, Rafael; de la Herrán, Roberto; Ruiz Rejón, Carmelo; Ruiz Rejón, Manuel; Santos, Juan Luis; Garrido-Ramos, Manuel A

    2007-01-01

    The structural features and evolutionary state of the sex chromosomes of the XX/XY species of Rumex are unknown. Here, we report a study of the meiotic behaviour of the XY bivalent in Rumex acetosella and R. suffruticosus, a new species which we describe cytogenetically for the first time in this paper, and also that of the XY(1)Y(2) trivalent of R. acetosa by both conventional cytogenetic techniques and analysis of synaptonemal complex formation. Fluorescent in situ hybridization with satellite DNA and rDNA sequences as probes was used to analyse the degree of cytogenetic differentiation between the X and Y chromosomes in order to depict their evolutionary stage in the three species. Contrasting with the advanced state of genetic differentiation between the X and the Y chromosomes in R. acetosa, we have found that R. acetosella and R. suffruticosus represent an early stage of genetic differentiation between sex chromosomes. Our findings further demonstrate the usefulness of the genus Rumex as a model for analysing the evolution of sex chromosomes in plants, since within this genus it is now possible to study the different levels of genetic differentiation between the sex chromosomes and to analyse their evolutionary history from their origin.

  13. A sex-chromosome mutation in Silene latifolia.

    PubMed

    Miller, Paige M; Kesseli, Richard V

    2011-09-01

    Silene latifolia is dioecious, yet rare hermaphrodites have been found, and such natural mutants can provide valuable insight into genetic mechanisms. Here, we describe a hermaphrodite-inducing mutation that is almost certainly localized to the gynoecium-suppression region of the Y chromosome in S. latifolia. The mutant Y chromosome was passed through the megaspore, and the presence of two X chromosomes was not necessary for seed development in the parent. This result supports a lack of degeneration of the Y chromosome in S. latifolia, consistent with the relatively recent formation of the sex chromosomes in this species. When crossed to wild-type plants, hermaphrodites performed poorly as females, producing low seed numbers. When hermaphrodites were pollen donors, the sex ratio of offspring they produced through crosses was biased towards females. This suggests that hermaphroditic S. latifolia would fail to thrive and potentially explains the rarity of hermaphrodites in natural populations of S. latifolia. These results indicate that the Y chromosome in Silene latifolia remains very similar to the X, perhaps mostly differing in the primary sex determination regions.

  14. Allele-Specific Expression Analysis Does Not Support Sex Chromosome Inactivation on the Chicken Z Chromosome.

    PubMed

    Wang, Qiong; Mank, Judith E; Li, Junying; Yang, Ning; Qu, Lujiang

    2017-03-01

    Heterogametic sex chromosomes have evolved many times independently, and in many cases, the loss of functional genes from the sex-limited Y or W chromosome leaves only one functional gene copy on the corresponding X or Z chromosome in the heterogametic sex. Because gene dose often correlates with gene expression level, this difference in gene dose between males and females for X- or Z-linked genes in some cases has selected for chromosome-wide transcriptional dosage compensation mechanisms to counteract any reduction in expression in the heterogametic sex. These mechanisms are thought to restore the balance between sex-linked loci and the autosomal genes they interact with, and this also typically results in equal expression between the sexes. However, dosage compensation in many other species is incomplete, and in the case of birds average expression from males (ZZ) remains higher than in females (ZW). Interestingly, recent reports in chickens and related species have shown that the Z chromosome is expressed less in males than would be expected from two copies of the chromosome, and recent data from cell-based approaches on 11 loci in chicken have suggested that one Z chromosome is partially inactivated in males, in a mechanism thought to be homologous to X inactivation in therian mammals. In the present study, we use controlled crosses in three tissues to test for the presence of Z inactivation in males, which would be expected to bias transcription to the active gene copy (allele-specific expression). We show that for the vast majority of genes on the chicken Z chromosome, males express both parental alleles at statistically similar levels, indicating no Z chromosome inactivation. For those Z chromosome loci with detectable ASE in males, we show that the most likely cause is cis-regulatory variation, rather than Z chromosome inactivation. Taken together, our results indicate that unlike the X chromosome in mammals, Z inactivation does not affect an appreciable

  15. In the platypus a meiotic chain of ten sex chromosomes shares genes with the bird Z and mammal X chromosomes.

    PubMed

    Grützner, Frank; Rens, Willem; Tsend-Ayush, Enkhjargal; El-Mogharbel, Nisrine; O'Brien, Patricia C M; Jones, Russell C; Ferguson-Smith, Malcolm A; Marshall Graves, Jennifer A

    2004-12-16

    Two centuries after the duck-billed platypus was discovered, monotreme chromosome systems remain deeply puzzling. Karyotypes of males, or of both sexes, were claimed to contain several unpaired chromosomes (including the X chromosome) that form a multi-chromosomal chain at meiosis. Such meiotic chains exist in plants and insects but are rare in vertebrates. How the platypus chromosome system works to determine sex and produce balanced gametes has been controversial for decades. Here we demonstrate that platypus have five male-specific chromosomes (Y chromosomes) and five chromosomes present in one copy in males and two copies in females (X chromosomes). These ten chromosomes form a multivalent chain at male meiosis, adopting an alternating pattern to segregate into XXXXX-bearing and YYYYY-bearing sperm. Which, if any, of these sex chromosomes bears one or more sex-determining genes remains unknown. The largest X chromosome, with homology to the human X chromosome, lies at one end of the chain, and a chromosome with homology to the bird Z chromosome lies near the other end. This suggests an evolutionary link between mammal and bird sex chromosome systems, which were previously thought to have evolved independently.

  16. Sex Chromosome Meiotic Drive in Stalk-Eyed Flies

    PubMed Central

    Presgraves, D. C.; Severance, E.; Wilkinson, G. S.

    1997-01-01

    Meiotically driven sex chromosomes can quickly spread to fixation and cause population extinction unless balanced by selection or suppressed by genetic modifiers. We report results of genetic analyses that demonstrate that extreme female-biased sex ratios in two sister species of stalk-eyed flies, Cyrtodiopsis dalmanni and C. whitei, are due to a meiotic drive element on the X chromosome (X(d)). Relatively high frequencies of X(d) in C. dalmanni and C. whitei (13-17% and 29%, respectively) cause female-biased sex ratios in natural populations of both species. Sex ratio distortion is associated with spermatid degeneration in male carriers of X(d). Variation in sex ratios is caused by Y-linked and autosomal factors that decrease the intensity of meiotic drive. Y-linked polymorphism for resistance to drive exists in C. dalmanni in which a resistant Y chromosome reduces the intensity and reverses the direction of meiotic drive. When paired with X(d), modifying Y chromosomes (Y(m)) cause the transmission of predominantly Y-bearing sperm, and on average, production of 63% male progeny. The absence of sex ratio distortion in closely related monomorphic outgroup species suggests that this meiotic drive system may predate the origin of C. whitei and C. dalmanni. We discuss factors likely to be involved in the persistence of these sex-linked polymorphisms and consider the impact of X(d) on the operational sex ratio and the intensity of sexual selection in these extremely sexually dimorphic flies. PMID:9383060

  17. Neurogenin 3 mediates sex chromosome effects on the generation of sex differences in hypothalamic neuronal development

    PubMed Central

    Scerbo, María J.; Freire-Regatillo, Alejandra; Cisternas, Carla D.; Brunotto, Mabel; Arevalo, Maria A.; Garcia-Segura, Luis M.; Cambiasso, María J.

    2014-01-01

    The organizational action of testosterone during critical periods of development is the cause of numerous sex differences in the brain. However, sex differences in neuritogenesis have been detected in primary neuronal hypothalamic cultures prepared before the peak of testosterone production by fetal testis. In the present study we assessed the hypothesis of that cell-autonomous action of sex chromosomes can differentially regulate the expression of the neuritogenic gene neurogenin 3 (Ngn3) in male and female hypothalamic neurons, generating sex differences in neuronal development. Neuronal cultures were prepared from male and female E14 mouse hypothalami, before the fetal peak of testosterone. Female neurons showed enhanced neuritogenesis and higher expression of Ngn3 than male neurons. The silencing of Ngn3 abolished sex differences in neuritogenesis, decreasing the differentiation of female neurons. The sex difference in Ngn3 expression was determined by sex chromosomes, as demonstrated using the four core genotypes mouse model, in which a spontaneous deletion of the testis-determining gene Sry from the Y chromosome was combined with the insertion of the Sry gene onto an autosome. In addition, the expression of Ngn3, which is also known to mediate the neuritogenic actions of estradiol, was increased in the cultures treated with the hormone, but only in those from male embryos. Furthermore, the hormone reversed the sex differences in neuritogenesis promoting the differentiation of male neurons. These findings indicate that Ngn3 mediates both cell-autonomous actions of sex chromosomes and hormonal effects on neuritogenesis. PMID:25071448

  18. Evidence for different origin of sex chromosomes in snakes, birds, and mammals and step-wise differentiation of snake sex chromosomes.

    PubMed

    Matsubara, Kazumi; Tarui, Hiroshi; Toriba, Michihisa; Yamada, Kazuhiko; Nishida-Umehara, Chizuko; Agata, Kiyokazu; Matsuda, Yoichi

    2006-11-28

    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.

  19. 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

  20. Y Fuse? Sex Chromosome Fusions in Fishes and Reptiles

    PubMed Central

    Vamosi, Jana C.; Peichel, Catherine L.; Valenzuela, Nicole; Kitano, Jun

    2015-01-01

    Chromosomal fusion plays a recurring role in the evolution of adaptations and reproductive isolation among species, yet little is known of the evolutionary drivers of chromosomal fusions. Because sex chromosomes (X and Y in male heterogametic systems, Z and W in female heterogametic systems) differ in their selective, mutational, and demographic environments, those differences provide a unique opportunity to dissect the evolutionary forces that drive chromosomal fusions. We estimate the rate at which fusions between sex chromosomes and autosomes become established across the phylogenies of both fishes and squamate reptiles. Both the incidence among extant species and the establishment rate of Y-autosome fusions is much higher than for X-autosome, Z-autosome, or W-autosome fusions. Using population genetic models, we show that this pattern cannot be reconciled with many standard explanations for the spread of fusions. In particular, direct selection acting on fusions or sexually antagonistic selection cannot, on their own, account for the predominance of Y-autosome fusions. The most plausible explanation for the observed data seems to be (a) that fusions are slightly deleterious, and (b) that the mutation rate is male-biased or the reproductive sex ratio is female-biased. We identify other combinations of evolutionary forces that might in principle account for the data although they appear less likely. Our results shed light on the processes that drive structural changes throughout the genome. PMID:25993542

  1. Y fuse? Sex chromosome fusions in fishes and reptiles.

    PubMed

    Pennell, Matthew W; Kirkpatrick, Mark; Otto, Sarah P; Vamosi, Jana C; Peichel, Catherine L; Valenzuela, Nicole; Kitano, Jun

    2015-05-01

    Chromosomal fusion plays a recurring role in the evolution of adaptations and reproductive isolation among species, yet little is known of the evolutionary drivers of chromosomal fusions. Because sex chromosomes (X and Y in male heterogametic systems, Z and W in female heterogametic systems) differ in their selective, mutational, and demographic environments, those differences provide a unique opportunity to dissect the evolutionary forces that drive chromosomal fusions. We estimate the rate at which fusions between sex chromosomes and autosomes become established across the phylogenies of both fishes and squamate reptiles. Both the incidence among extant species and the establishment rate of Y-autosome fusions is much higher than for X-autosome, Z-autosome, or W-autosome fusions. Using population genetic models, we show that this pattern cannot be reconciled with many standard explanations for the spread of fusions. In particular, direct selection acting on fusions or sexually antagonistic selection cannot, on their own, account for the predominance of Y-autosome fusions. The most plausible explanation for the observed data seems to be (a) that fusions are slightly deleterious, and (b) that the mutation rate is male-biased or the reproductive sex ratio is female-biased. We identify other combinations of evolutionary forces that might in principle account for the data although they appear less likely. Our results shed light on the processes that drive structural changes throughout the genome.

  2. Cognitive and Academic Skills in Children with Sex Chromosome Abnormalities.

    ERIC Educational Resources Information Center

    Bender, Bruce G.; And Others

    1991-01-01

    Follows 46 unselected children with various sex chromosome abnormalities using intellectual, language, and achievement testing. Notes that, although most children were not mentally retarded, most received special education help. Finds support for the inference that learning disorders were genetically mediated in this group. (RS)

  3. Cognitive and Academic Skills in Children with Sex Chromosome Abnormalities.

    ERIC Educational Resources Information Center

    Bender, Bruce G.; And Others

    1991-01-01

    Follows 46 unselected children with various sex chromosome abnormalities using intellectual, language, and achievement testing. Notes that, although most children were not mentally retarded, most received special education help. Finds support for the inference that learning disorders were genetically mediated in this group. (RS)

  4. Chromosome mapping of repetitive sequences in Anostomidae species: implications for genomic and sex chromosome evolution

    PubMed Central

    2012-01-01

    Background Members of the Anostomidae family provide an interesting model system for the study of the influence of repetitive elements on genome composition, mainly because they possess numerous heterochromatic segments and a peculiar system of female heterogamety that is restricted to a few species of the Leporinus genus. The aim of this study was to isolate and identify important new repetitive DNA elements in Anostomidae through restriction enzyme digestion, followed by cloning, characterisation and chromosome mapping of this fragment. To identify repetitive elements in other Leporinus species and expand on studies of repetitive elements in Anostomidae, hybridisation experiments were also performed using previously described probes of LeSpeI repetitive elements. Results The 628-base pair (bp) LeSpeII fragment was hybridised to metaphase cells of L. elongatus individuals as well as those of L. macrocephalus, L. obtusidens, L. striatus, L. lacustris, L. friderici, Schizodon borellii and S. isognathus. In L. elongatus, both male and female cells contained small clusters of LeSpeII repetitive elements dispersed on all of the chromosomes, with enrichment near most of the terminal portions of the chromosomes. In the female sex chromosomes of L. elongatus (Z2,Z2/W1W2), however, this repeated element was absent. In the remaining species, a dispersed pattern of hybridisation was observed on all chromosomes irrespective of whether or not they were sex chromosomes. The repetitive element LeSpeI produced positive hybridisations signals only in L. elongatus, L. macrocephalus and L. obtusidens, i.e., species with differentiated sex chromosomes. In the remaining species, the LeSpeI element did not produce hybridisation signals. Conclusions Results are discussed in terms of the effects of repetitive sequences on the differentiation of the Anostomidae genome, especially with respect to sex chromosome evolution. LeSpeII showed hybridisation patterns typical of Long Interspersed

  5. Sequencing the mouse Y chromosome reveals convergent gene acquisition and amplification on both sex chromosomes

    PubMed Central

    Soh, Y.Q. Shirleen; Alföldi, Jessica; Pyntikova, Tatyana; Brown, Laura G.; Graves, Tina; Minx, Patrick J.; Fulton, Robert S.; Kremitzki, Colin; Koutseva, Natalia; Mueller, Jacob L.; Rozen, Steve; Hughes, Jennifer F.; Owens, Elaine; Womack, James E.; Murphy, William J.; Cao, Qing; de Jong, Pieter; Warren, Wesley C.; Wilson, Richard K.; Skaletsky, Helen; Page, David C.

    2014-01-01

    Summary We sequenced the MSY (Male-Specific region of the Y chromosome) of the C57BL/6J strain of the laboratory mouse Mus musculus. In contrast to theories that Y chromosomes are heterochromatic and gene poor, the mouse MSY is 99.9% euchromatic and contains about 700 protein-coding genes. Only two percent of the MSY derives from the ancestral autosomes that gave rise to the mammalian sex chromosomes. Instead, all but 50 of the MSY's genes belong to three acquired, massively amplified gene families that have no homologs on primate MSYs, but do have acquired, amplified homologs on the mouse X chromosome. The complete mouse MSY sequence brings to light dramatic forces in sex chromosome evolution: lineage-specific convergent acquisition and amplification of X-Y gene families, possibly fueled by antagonism between acquired X-Y homologs. The mouse MSY sequence presents opportunities for experimental studies of a sex-specific chromosome in its entirety, in a genetically tractable model organism. PMID:25417157

  6. Hypermethylated Chromosome Regions in Nine Fish Species with Heteromorphic Sex Chromosomes.

    PubMed

    Schmid, Michael; Steinlein, Claus; Yano, Cassia F; Cioffi, Marcelo B

    2015-01-01

    Sites and amounts of 5-methylcytosine (5-MeC)-rich chromosome regions were detected in the karyotypes of 9 Brazilian species of Characiformes fishes by indirect immunofluorescence using a monoclonal anti-5-MeC antibody. These species, belonging to the genera Leporinus, Triportheus and Hoplias, are characterized by highly differentiated and heteromorphic ZW and XY sex chromosomes. In all species, the hypermethylated regions are confined to constitutive heterochromatin. The number and chromosome locations of hypermethylated heterochromatic regions in the karyotypes are constant and species-specific. Generally, heterochromatic regions that are darkly stained by the C-banding technique are distinctly hypermethylated, but several of the brightly fluorescing hypermethylated regions merely exhibit moderate or faint C-banding. The ZW and XY sex chromosomes of all 9 analyzed species also show species-specific heterochromatin hypermethylation patterns. The analysis of 5-MeC-rich chromosome regions contributes valuable data for comparative cytogenetics of closely related species and highlights the dynamic process of differentiation operating in the repetitive DNA fraction of sex chromosomes. © 2016 S. Karger AG, Basel.

  7. Sequencing the mouse Y chromosome reveals convergent gene acquisition and amplification on both sex chromosomes.

    PubMed

    Soh, Y Q Shirleen; Alföldi, Jessica; Pyntikova, Tatyana; Brown, Laura G; Graves, Tina; Minx, Patrick J; Fulton, Robert S; Kremitzki, Colin; Koutseva, Natalia; Mueller, Jacob L; Rozen, Steve; Hughes, Jennifer F; Owens, Elaine; Womack, James E; Murphy, William J; Cao, Qing; de Jong, Pieter; Warren, Wesley C; Wilson, Richard K; Skaletsky, Helen; Page, David C

    2014-11-06

    We sequenced the MSY (male-specific region of the Y chromosome) of the C57BL/6J strain of the laboratory mouse Mus musculus. In contrast to theories that Y chromosomes are heterochromatic and gene poor, the mouse MSY is 99.9% euchromatic and contains about 700 protein-coding genes. Only 2% of the MSY derives from the ancestral autosomes that gave rise to the mammalian sex chromosomes. Instead, all but 45 of the MSY's genes belong to three acquired, massively amplified gene families that have no homologs on primate MSYs but do have acquired, amplified homologs on the mouse X chromosome. The complete mouse MSY sequence brings to light dramatic forces in sex chromosome evolution: lineage-specific convergent acquisition and amplification of X-Y gene families, possibly fueled by antagonism between acquired X-Y homologs. The mouse MSY sequence presents opportunities for experimental studies of a sex-specific chromosome in its entirety, in a genetically tractable model organism.

  8. The Staurotypus turtles and aves share the same origin of sex chromosomes but evolved different types of heterogametic sex determination.

    PubMed

    Kawagoshi, Taiki; Uno, Yoshinobu; Nishida, Chizuko; Matsuda, Yoichi

    2014-01-01

    Reptiles have a wide diversity of sex-determining mechanisms and types of sex chromosomes. Turtles exhibit temperature-dependent sex determination and genotypic sex determination, with male heterogametic (XX/XY) and female heterogametic (ZZ/ZW) sex chromosomes. Identification of sex chromosomes in many turtle species and their comparative genomic analysis are of great significance to understand the evolutionary processes of sex determination and sex chromosome differentiation in Testudines. The Mexican giant musk turtle (Staurotypus triporcatus, Kinosternidae, Testudines) and the giant musk turtle (Staurotypus salvinii) have heteromorphic XY sex chromosomes with a low degree of morphological differentiation; however, their origin and linkage group are still unknown. Cross-species chromosome painting with chromosome-specific DNA from Chinese soft-shelled turtle (Pelodiscus sinensis) revealed that the X and Y chromosomes of S. triporcatus have homology with P. sinensis chromosome 6, which corresponds to the chicken Z chromosome. We cloned cDNA fragments of S. triporcatus homologs of 16 chicken Z-linked genes and mapped them to S. triporcatus and S. salvinii chromosomes using fluorescence in situ hybridization. Sixteen genes were localized to the X and Y long arms in the same order in both species. The orders were also almost the same as those of the ostrich (Struthio camelus) Z chromosome, which retains the primitive state of the avian ancestral Z chromosome. These results strongly suggest that the X and Y chromosomes of Staurotypus turtles are at a very early stage of sex chromosome differentiation, and that these chromosomes and the avian ZW chromosomes share the same origin. Nonetheless, the turtles and birds acquired different systems of heterogametic sex determination during their evolution.

  9. The Staurotypus Turtles and Aves Share the Same Origin of Sex Chromosomes but Evolved Different Types of Heterogametic Sex Determination

    PubMed Central

    Kawagoshi, Taiki; Uno, Yoshinobu; Nishida, Chizuko; Matsuda, Yoichi

    2014-01-01

    Reptiles have a wide diversity of sex-determining mechanisms and types of sex chromosomes. Turtles exhibit temperature-dependent sex determination and genotypic sex determination, with male heterogametic (XX/XY) and female heterogametic (ZZ/ZW) sex chromosomes. Identification of sex chromosomes in many turtle species and their comparative genomic analysis are of great significance to understand the evolutionary processes of sex determination and sex chromosome differentiation in Testudines. The Mexican giant musk turtle (Staurotypus triporcatus, Kinosternidae, Testudines) and the giant musk turtle (Staurotypus salvinii) have heteromorphic XY sex chromosomes with a low degree of morphological differentiation; however, their origin and linkage group are still unknown. Cross-species chromosome painting with chromosome-specific DNA from Chinese soft-shelled turtle (Pelodiscus sinensis) revealed that the X and Y chromosomes of S. triporcatus have homology with P. sinensis chromosome 6, which corresponds to the chicken Z chromosome. We cloned cDNA fragments of S. triporcatus homologs of 16 chicken Z-linked genes and mapped them to S. triporcatus and S. salvinii chromosomes using fluorescence in situ hybridization. Sixteen genes were localized to the X and Y long arms in the same order in both species. The orders were also almost the same as those of the ostrich (Struthio camelus) Z chromosome, which retains the primitive state of the avian ancestral Z chromosome. These results strongly suggest that the X and Y chromosomes of Staurotypus turtles are at a very early stage of sex chromosome differentiation, and that these chromosomes and the avian ZW chromosomes share the same origin. Nonetheless, the turtles and birds acquired different systems of heterogametic sex determination during their evolution. PMID:25121779

  10. THE CONTRIBUTION OF FEMALE MEIOTIC DRIVE TO THE EVOLUTION OF NEO-SEX CHROMOSOMES

    PubMed Central

    Yoshida, Kohta; Kitano, Jun

    2012-01-01

    Sex chromosomes undergo rapid turnover in certain taxonomic groups. One of the mechanisms of sex chromosome turnover involves fusions between sex chromosomes and autosomes. Sexual antagonism, heterozygote advantage, and genetic drift have been proposed as the drivers for the fixation of this evolutionary event. However, all empirical patterns of the prevalence of multiple sex chromosome systems across different taxa cannot be simply explained by these three mechanisms. In this study, we propose that female meiotic drive may contribute to the evolution of neo-sex chromosomes. The results of this study showed that in mammals, the XY1Y2 sex chromosome system is more prevalent in species with karyotypes of more biarmed chromosomes, whereas the X1X2Y sex chromosome system is more prevalent in species with predominantly acrocentric chromosomes. In species where biarmed chromosomes are favored by female meiotic drive, X-autosome fusions (XY1Y2 sex chromosome system) will be also favored by female meiotic drive. In contrast, in species with more acrocentric chromosomes, Y-autosome fusions (X1X2Y sex chromosome system) will be favored just because of the biased mutation rate toward chromosomal fusions. Further consideration should be given to female meiotic drive as a mechanism in the fixation of neo-sex chromosomes. PMID:23025609

  11. The contribution of female meiotic drive to the evolution of neo-sex chromosomes.

    PubMed

    Yoshida, Kohta; Kitano, Jun

    2012-10-01

    Sex chromosomes undergo rapid turnover in certain taxonomic groups. One of the mechanisms of sex chromosome turnover involves fusions between sex chromosomes and autosomes. Sexual antagonism, heterozygote advantage, and genetic drift have been proposed as the drivers for the fixation of this evolutionary event. However, all empirical patterns of the prevalence of multiple sex chromosome systems across different taxa cannot be simply explained by these three mechanisms. In this study, we propose that female meiotic drive may contribute to the evolution of neo-sex chromosomes. The results of this study showed that in mammals, the XY(1) Y(2) sex chromosome system is more prevalent in species with karyotypes of more biarmed chromosomes, whereas the X(1) X(2) Y sex chromosome system is more prevalent in species with predominantly acrocentric chromosomes. In species where biarmed chromosomes are favored by female meiotic drive, X-autosome fusions (XY(1) Y(2) sex chromosome system) will be also favored by female meiotic drive. In contrast, in species with more acrocentric chromosomes, Y-autosome fusions (X(1) X(2) Y sex chromosome system) will be favored just because of the biased mutation rate toward chromosomal fusions. Further consideration should be given to female meiotic drive as a mechanism in the fixation of neo-sex chromosomes.

  12. Identification of the sex chromosome pair in chum salmon (Oncorhynchus keta) and pink salmon (Oncorhynchus gorbuscha).

    PubMed

    Phillips, R B; DeKoning, J; Morasch, M R; Park, L K; Devlin, R H

    2007-01-01

    Fluorescence in situ hybridization (FISH) using a probe to the male-specific GH-Y (growth hormone pseudogene) was used to identify the Y chromosome in the karyotypes of chum salmon (Oncorhynchus keta) and pink salmon (Oncorhynchus gorbuscha). The sex chromosome pair is a small acrocentric chromosome pair in chum salmon and the smallest metacentric chromosome pair in pink salmon. Both of these chromosome pairs are morphologically different from the sex chromosome pairs in chinook salmon (Oncorhynchus tshawytscha) and coho salmon (Oncorhynchus kisutch). The 5S rRNA genes are on multiple chromosome pairs including the sex chromosome pair in chum salmon, but at the centromeres of two autosomal metacentric pairs in pink salmon. The sex chromosome pairs and the chromosomal locations of the 5S rDNA appear to be different in all five of the North American Pacific salmon species and rainbow trout. The implications of these results for evolution of sex chromosomes in salmonids are discussed.

  13. An XX/XY heteromorphic sex chromosome system in the Australian chelid turtle Emydura macquarii: a new piece in the puzzle of sex chromosome evolution in turtles.

    PubMed

    Martinez, Pedro Alonzo; Ezaz, Tariq; Valenzuela, Nicole; Georges, Arthur; Marshall Graves, Jennifer A

    2008-01-01

    Chromosomal sex determination is the prevalent system found in animals but is rare among turtles. In fact, heteromorphic sex chromosomes are known in only seven of the turtles possessing genotypic sex determination (GSD), two of which correspond to cryptic sex microchromosomes detectable only with high-resolution cytogenetic techniques. Sex chromosomes were undetected in previous studies of Emydura macquarii, a GSD side-necked turtle. Using comparative genomic hybridization (CGH) and GTG-banding, a heteromorphic XX/XY sex chromosome system was detected in E. macquarii. The Y chromosome appears submetacentric and somewhat larger than the metacentric X, the first such report for turtles. CGH revealed a male-specific chromosomal region, which appeared heteromorphic using GTG-banding, and was restricted to the telomeric region of the p arm. Based on our observations and the current phylogeny of chelid turtles, we hypothesize that the sex chromosomes of E. macquarii might be the result of a translocation of an ancestral Y microchromosome as found in a turtle belonging to a sister clade, Chelodina longicollis, onto the tip of an autosome. However, in the absence of data from an outgroup, the opposite (fission of a large XY into an autosome and a micro-XY) is theoretically equally likely. Alternatively, the sex chromosome systems of E. macquarii and C. longicollis may have evolved independently. We discuss the potential causes and consequences of such putative chromosome rearrangements in the evolution of sex chromosomes and sex-determining systems of turtles in general.

  14. SEX-DETector: A Probabilistic Approach to Study Sex Chromosomes in Non-Model Organisms

    PubMed Central

    Muyle, Aline; Käfer, Jos; Zemp, Niklaus; Mousset, Sylvain; Picard, Franck; Marais, Gabriel AB

    2016-01-01

    We propose a probabilistic framework to infer autosomal and sex-linked genes from RNA-seq data of a cross for any sex chromosome type (XY, ZW, and UV). Sex chromosomes (especially the non-recombining and repeat-dense Y, W, U, and V) are notoriously difficult to sequence. Strategies have been developed to obtain partially assembled sex chromosome sequences. Most of them remain difficult to apply to numerous non-model organisms, either because they require a reference genome, or because they are designed for evolutionarily old systems. Sequencing a cross (parents and progeny) by RNA-seq to study the segregation of alleles and infer sex-linked genes is a cost-efficient strategy, which also provides expression level estimates. However, the lack of a proper statistical framework has limited a broader application of this approach. Tests on empirical Silene data show that our method identifies 20–35% more sex-linked genes than existing pipelines, while making reliable inferences for downstream analyses. Approximately 12 individuals are needed for optimal results based on simulations. For species with an unknown sex-determination system, the method can assess the presence and type (XY vs. ZW) of sex chromosomes through a model comparison strategy. The method is particularly well optimized for sex chromosomes of young or intermediate age, which are expected in thousands of yet unstudied lineages. Any organisms, including non-model ones for which nothing is known a priori, that can be bred in the lab, are suitable for our method. SEX-DETector and its implementation in a Galaxy workflow are made freely available. PMID:27492231

  15. Deficit of mitonuclear genes on the human X chromosome predates sex chromosome formation.

    PubMed

    Dean, Rebecca; Zimmer, Fabian; Mank, Judith E

    2015-01-29

    Two taxa studied to date, the therian mammals and Caenorhabditis elegans, display underrepresentations of mitonuclear genes (mt-N genes, nuclear genes whose products are imported to and act within the mitochondria) on their X chromosomes. This pattern has been interpreted as the result of sexual conflict driving mt-N genes off of the X chromosome. However, studies in several other species have failed to detect a convergent biased distribution of sex-linked mt-N genes, leading to questions over the generality of the role of sexual conflict in shaping the distribution of mt-N genes. Here we tested whether mt-N genes moved off of the therian X chromosome following sex chromosome formation, consistent with the role of sexual conflict, or whether the paucity of mt-N genes on the therian X is a chance result of an underrepresentation on the ancestral regions that formed the X chromosome. We used a synteny-based approach to identify the ancestral regions in the platypus and chicken genomes that later formed the therian X chromosome. We then quantified the movement of mt-N genes on and off of the X chromosome and the distribution of mt-N genes on the human X and ancestral X regions. We failed to find an excess of mt-N gene movement off of the X. The bias of mt-N genes on ancestral therian X chromosomes was also not significantly different from the biases on the human X. Together our results suggest that, rather than conflict driving mt-N genes off of the mammalian X, random biases on chromosomes that formed the X chromosome could explain the paucity of mt-N genes in the therian lineage.

  16. Female heterogamety in Madagascar chameleons (Squamata: Chamaeleonidae: Furcifer): differentiation of sex and neo-sex chromosomes

    PubMed Central

    Rovatsos, Michail; Pokorná, Martina Johnson; Altmanová, Marie; Kratochvíl, Lukáš

    2015-01-01

    Amniotes possess variability in sex determining mechanisms, however, this diversity is still only partially known throughout the clade and sex determining systems still remain unknown even in such a popular and distinctive lineage as chameleons (Squamata: Acrodonta: Chamaeleonidae). Here, we present evidence for female heterogamety in this group. The Malagasy giant chameleon (Furcifer oustaleti) (chromosome number 2n = 22) possesses heteromorphic Z and W sex chromosomes with heterochromatic W. The panther chameleon (Furcifer pardalis) (2n = 22 in males, 21 in females), the second most popular chameleon species in the world pet trade, exhibits a rather rare Z1Z1Z2Z2/Z1Z2W system of multiple sex chromosomes, which most likely evolved from W-autosome fusion. Notably, its neo-W chromosome is partially heterochromatic and its female-specific genetic content has expanded into the previously autosomal region. Showing clear evidence for genotypic sex determination in the panther chameleon, we resolve the long-standing question of whether or not environmental sex determination exists in this species. Together with recent findings in other reptile lineages, our work demonstrates that female heterogamety is widespread among amniotes, adding another important piece to the mosaic of knowledge on sex determination in amniotes needed to understand the evolution of this important trait. PMID:26286647

  17. Female heterogamety in Madagascar chameleons (Squamata: Chamaeleonidae: Furcifer): differentiation of sex and neo-sex chromosomes.

    PubMed

    Rovatsos, Michail; Johnson Pokorná, Martina; Altmanová, Marie; Kratochvíl, Lukáš

    2015-08-19

    Amniotes possess variability in sex determining mechanisms, however, this diversity is still only partially known throughout the clade and sex determining systems still remain unknown even in such a popular and distinctive lineage as chameleons (Squamata: Acrodonta: Chamaeleonidae). Here, we present evidence for female heterogamety in this group. The Malagasy giant chameleon (Furcifer oustaleti) (chromosome number 2n = 22) possesses heteromorphic Z and W sex chromosomes with heterochromatic W. The panther chameleon (Furcifer pardalis) (2n = 22 in males, 21 in females), the second most popular chameleon species in the world pet trade, exhibits a rather rare Z1Z1Z2Z2/Z1Z2W system of multiple sex chromosomes, which most likely evolved from W-autosome fusion. Notably, its neo-W chromosome is partially heterochromatic and its female-specific genetic content has expanded into the previously autosomal region. Showing clear evidence for genotypic sex determination in the panther chameleon, we resolve the long-standing question of whether or not environmental sex determination exists in this species. Together with recent findings in other reptile lineages, our work demonstrates that female heterogamety is widespread among amniotes, adding another important piece to the mosaic of knowledge on sex determination in amniotes needed to understand the evolution of this important trait.

  18. Sex chromosome aneuploidies in sperm of 47,XYY men.

    PubMed

    Morel, F; Roux, C; Bresson, J L

    1999-01-01

    The sex chromosomal equipment in 26,675 sperm of 47,XYY males was analyzed. A total of 5.78% of the nuclei exhibited sex chromosome hyperhaploidy. Six studies have analyzed the sperm of 10 XYY patients and, although these studies indicated some degree of elimination of the extra Y chromosome during spermatogenesis, a certain percentage of XYY germinal cells may also be able to achieve meiosis and produce sperm with gonosomal disomies. All these studies show an increased incidence of gonosomal aneuploidies in sperm, but there are significant discrepancies concerning the extent of these abnormalities. The global frequencies of sperm with an abnormal number of sex chromosomes ranged from 0.578 to 13.91%, depending on the patients. There are several explanations for these discrepancies: differences attributed to fluorescence in situ hybridization methodology, the use of dual or multicolor FISH, recruitment, interindividual variations, and intraindividual variations. This study reports an additional series obtained from another XYY individual and compares and discusses the data on gonosomal hyperhaploidies in sperm of 47 XYY males using in situ hybridization analyses.

  19. Rapid Y degeneration and dosage compensation in plant sex chromosomes.

    PubMed

    Papadopulos, Alexander S T; Chester, Michael; Ridout, Kate; Filatov, Dmitry A

    2015-10-20

    The nonrecombining regions of animal Y chromosomes are known to undergo genetic degeneration, but previous work has failed to reveal large-scale gene degeneration on plant Y chromosomes. Here, we uncover rapid and extensive degeneration of Y-linked genes in a plant species, Silene latifolia, that evolved sex chromosomes de novo in the last 10 million years. Previous transcriptome-based studies of this species missed unexpressed, degenerate Y-linked genes. To identify sex-linked genes, regardless of their expression, we sequenced male and female genomes of S. latifolia and integrated the genomic contigs with a high-density genetic map. This revealed that 45% of Y-linked genes are not expressed, and 23% are interrupted by premature stop codons. This contrasts with X-linked genes, in which only 1.3% of genes contained stop codons and 4.3% of genes were not expressed in males. Loss of functional Y-linked genes is partly compensated for by gene-specific up-regulation of X-linked genes. Our results demonstrate that the rate of genetic degeneration of Y-linked genes in S. latifolia is as fast as in animals, and that the evolutionary trajectories of sex chromosomes are similar in the two kingdoms.

  20. Modeling X Chromosome Data Using Random Forests: Conquering Sex Bias.

    PubMed

    Winham, Stacey J; Jenkins, Gregory D; Biernacka, Joanna M

    2016-02-01

    Machine learning methods, including Random Forests (RF), are increasingly used for genetic data analysis. However, the standard RF algorithm does not correctly model the effects of X chromosome single nucleotide polymorphisms (SNPs), leading to biased estimates of variable importance. We propose extensions of RF to correctly model X SNPs, including a stratified approach and an approach based on the process of X chromosome inactivation. We applied the new and standard RF approaches to case-control alcohol dependence data from the Study of Addiction: Genes and Environment (SAGE), and compared the performance of the alternative approaches via a simulation study. Standard RF applied to a case-control study of alcohol dependence yielded inflated variable importance estimates for X SNPs, even when sex was included as a variable, but the results of the new RF methods were consistent with univariate regression-based approaches that correctly model X chromosome data. Simulations showed that the new RF methods eliminate the bias in standard RF variable importance for X SNPs when sex is associated with the trait, and are able to detect causal autosomal and X SNPs. Even in the absence of sex effects, the new extensions perform similarly to standard RF. Thus, we provide a powerful multimarker approach for genetic analysis that accommodates X chromosome data in an unbiased way. This method is implemented in the freely available R package "snpRF" (http://www.cran.r-project.org/web/packages/snpRF/). © 2015 WILEY PERIODICALS, INC.

  1. The Sex Chromosomes in Evolution and in Medicine

    PubMed Central

    Barr, Murray L.

    1966-01-01

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

  2. An Allometric Analysis of Sex and Sex Chromosome Dosage Effects on Subcortical Anatomy in Humans

    PubMed Central

    Clasen, Liv; Giedd, Jay N.; Blumenthal, Jonathan; Lerch, Jason P.; Chakravarty, M. Mallar; Raznahan, Armin

    2016-01-01

    Structural neuroimaging of humans with typical and atypical sex-chromosome complements has established the marked influence of both Yand X-/Y-chromosome dosage on total brain volume (TBV) and identified potential cortical substrates for the psychiatric phenotypes associated with sex-chromosome aneuploidy (SCA). Here, in a cohort of 354 humans with varying karyotypes (XX, XY, XXX, XXY, XYY, XXYY, XXXXY), we investigate sex and SCA effects on subcortical size and shape; focusing on the striatum, pallidum and thalamus. We find large effect-size differences in the volume and shape of all three structures as a function of sex and SCA. We correct for TBV effects with a novel allometric method harnessing normative scaling rules for subcortical size and shape in humans, which we derive here for the first time. We show that all three subcortical volumes scale sublinearly with TBV among healthy humans, mirroring known relationships between subcortical volume and TBV among species. Traditional TBV correction methods assume linear scaling and can therefore invert or exaggerate sex and SCA effects on subcortical anatomy. Allometric analysis restricts sex-differences to: (1) greater pallidal volume (PV) in males, and (2) relative caudate head expansion and ventral striatum contraction in females. Allometric analysis of SCA reveals that supernumerary X- and Y-chromosomes both cause disproportionate reductions in PV, and coordinated deformations of striatopallidal shape. Our study provides a novel understanding of sex and sex-chromosome dosage effects on subcortical organization, using an allometric approach that can be generalized to other basic and clinical structural neuroimaging settings. SIGNIFICANCE STATEMENT Sex and sex-chromosome dosage (SCD) are known to modulate human brain size and cortical anatomy, but very little is known regarding their impact on subcortical structures that work with the cortex to subserve a range of behaviors in health and disease. Moreover

  3. Genetic analysis of sex chromosomal meiotic mutants in Drosophilia melanogaster.

    PubMed

    Baker, B S; Carpenter, A T

    1972-06-01

    A total of 209 ethyl methanesulfonate-treated X chromosomes were screened for meiotic mutants that either (1) increased sex or fourth chromosome nondisjunction at either meiotic division in males; (2) allowed recombination in such males; (3) increased nondisjunction of the X chromosome at either meiotic division in females; or (4) caused such females, when mated to males heterozygous for Segregation-Distorter (SD) and a sensitive homolog to alter the strength of meiotic drive in males.-Twenty male-specific meiotic mutants were found. Though the rates of nondisjunction differed, all twenty mutants were qualitatively similar in that (1) they alter the disjunction of the X chromosome from the Y chromosome; (2) among the recovered sex-chromosome exceptional progeny, there is a large excess of those derived from nullo-XY as compared to XY gametes; (3) there is a negative correlation between the frequency of sex-chromosome exceptional progeny and the frequency of males among the regular progeny. In their effects on meiosis these mutants are similar to In(1)sc(4L)sc(8R), which is deleted for the basal heterochromatin. These mutants, however, have normal phenotypes and viabilities when examined as X/0 males, and furthermore, a mapping of two of the mutants places them in the euchromatin of the X chromosome. It is suggested that these mutants are in genes whose products are involved in insuring the proper functioning of the basal pairing sites which are deleted in In(1)sc(4L)sc(8R), and in addition that there is a close connection, perhaps causal, between the disruption of normal X-Y pairing (and, therefore, disjunction) and the occurrence of meiotic drive in the male.-Eleven mutants were found which increased nondisjunction in females. These mutants were characterized as to (1) the division at which they acted; (2) their effect on recombination; (3) their dominance; (4) their effects on disjunction of all four chromosome pairs. Five female mutants caused a nonuniform

  4. Avian sex, sex chromosomes, and dosage compensation in the age of genomics.

    PubMed

    Graves, Jennifer A Marshall

    2014-04-01

    Comparisons of the sex chromosome systems in birds and mammals are widening our view and deepening our understanding of vertebrate sex chromosome organization, function, and evolution. Birds have a very conserved ZW system of sex determination in which males have two copies of a large, gene-rich Z chromosome, and females have a single Z and a female-specific W chromosome. The avian ZW system is quite the reverse of the well-studied mammalian XY chromosome system, and evolved independently from different autosomal blocs. Despite the different gene content of mammal and bird sex chromosomes, there are many parallels. Genes on the bird Z and the mammal X have both undergone selection for male-advantage functions, and there has been amplification of male-advantage genes and accumulation of LINEs. The bird W and mammal Y have both undergone extensive degradation, but some birds retain early stages and some mammals terminal stages of the process, suggesting that the process is more advanced in mammals. Different sex-determining genes, DMRT1 and SRY, define the ZW and XY systems, but DMRT1 is involved in downstream events in mammals. Birds show strong cell autonomous specification of somatic sex differences in ZZ and ZW tissue, but there is growing evidence for direct X chromosome effects on sexual phenotype in mammals. Dosage compensation in birds appears to be phenotypically and molecularly quite different from X inactivation, being partial and gene-specific, but both systems use tools from the same molecular toolbox and there are some signs that galliform birds represent an early stage in the evolution of a coordinated system.

  5. Rapid evolution of a Y-chromosome heterochromatin protein underlies sex chromosome meiotic drive.

    PubMed

    Helleu, Quentin; Gérard, Pierre R; Dubruille, Raphaëlle; Ogereau, David; Prud'homme, Benjamin; Loppin, Benjamin; Montchamp-Moreau, Catherine

    2016-04-12

    Sex chromosome meiotic drive, the non-Mendelian transmission of sex chromosomes, is the expression of an intragenomic conflict that can have extreme evolutionary consequences. However, the molecular bases of such conflicts remain poorly understood. Here, we show that a young and rapidly evolving X-linked heterochromatin protein 1 (HP1) gene, HP1D2, plays a key role in the classical Paris sex-ratio (SR) meiotic drive occurring in Drosophila simulans Driver HP1D2 alleles prevent the segregation of the Y chromatids during meiosis II, causing female-biased sex ratio in progeny. HP1D2 accumulates on the heterochromatic Y chromosome in male germ cells, strongly suggesting that it controls the segregation of sister chromatids through heterochromatin modification. We show that Paris SR drive is a consequence of dysfunctional HP1D2 alleles that fail to prepare the Y chromosome for meiosis, thus providing evidence that the rapid evolution of genes controlling the heterochromatin structure can be a significant source of intragenomic conflicts.

  6. Rapid evolution of a Y-chromosome heterochromatin protein underlies sex chromosome meiotic drive

    PubMed Central

    Helleu, Quentin; Gérard, Pierre R.; Dubruille, Raphaëlle; Ogereau, David; Prud’homme, Benjamin; Loppin, Benjamin; Montchamp-Moreau, Catherine

    2016-01-01

    Sex chromosome meiotic drive, the non-Mendelian transmission of sex chromosomes, is the expression of an intragenomic conflict that can have extreme evolutionary consequences. However, the molecular bases of such conflicts remain poorly understood. Here, we show that a young and rapidly evolving X-linked heterochromatin protein 1 (HP1) gene, HP1D2, plays a key role in the classical Paris sex-ratio (SR) meiotic drive occurring in Drosophila simulans. Driver HP1D2 alleles prevent the segregation of the Y chromatids during meiosis II, causing female-biased sex ratio in progeny. HP1D2 accumulates on the heterochromatic Y chromosome in male germ cells, strongly suggesting that it controls the segregation of sister chromatids through heterochromatin modification. We show that Paris SR drive is a consequence of dysfunctional HP1D2 alleles that fail to prepare the Y chromosome for meiosis, thus providing evidence that the rapid evolution of genes controlling the heterochromatin structure can be a significant source of intragenomic conflicts. PMID:26979956

  7. The great escape: Active genes on inactive sex chromosomes and their evolutionary implications.

    PubMed

    Sin, Ho-Su; Namekawa, Satoshi H

    2013-09-01

    Epigenetic mechanisms precisely regulate sex chromosome inactivation as well as genes that escape the silencing process. In male germ cells, DNA damage response factor RNF8 establishes active epigenetic modifications on the silent sex chromosomes during meiosis, and activates escape genes during a state of sex chromosome-wide silencing in postmeiotic spermatids. During the course of evolution, the gene content of escape genes in postmeiotic spermatids recently diverged on the sex chromosomes. This evolutionary feature mirrors the epigenetic processes of sex chromosomes in germ cells. In this article, we describe how epigenetic processes have helped to shape the evolution of sex chromosome-linked genes. Furthermore, we compare features of escape genes on sex chromosomes in male germ cells to escape genes located on the single X chromosome silenced during X-inactivation in females, clarifying the distinct evolutionary implications between male and female escape genes.

  8. Progressive recombination suppression and differentiation in recently evolved neo-sex chromosomes.

    PubMed

    Natri, Heini M; Shikano, Takahito; Merilä, Juha

    2013-05-01

    Recombination suppression leads to the structural and functional differentiation of sex chromosomes and is thus a crucial step in the process of sex chromosome evolution. Despite extensive theoretical work, the exact processes and mechanisms of recombination suppression and differentiation are not well understood. In threespine sticklebacks (Gasterosteus aculeatus), a different sex chromosome system has recently evolved by a fusion between the Y chromosome and an autosome in the Japan Sea lineage, which diverged from the ancestor of other lineages approximately 2 Ma. We investigated the evolutionary dynamics and differentiation processes of sex chromosomes based on comparative analyses of these divergent lineages using 63 microsatellite loci. Both chromosome-wide differentiation patterns and phylogenetic inferences with X and Y alleles indicated that the ancestral sex chromosomes were extensively differentiated before the divergence of these lineages. In contrast, genetic differentiation appeared to have proceeded only in a small region of the neo-sex chromosomes. The recombination maps constructed for the Japan Sea lineage indicated that recombination has been suppressed or reduced over a large region spanning the ancestral and neo-sex chromosomes. Chromosomal regions exhibiting genetic differentiation and suppressed or reduced recombination were detected continuously and sequentially in the neo-sex chromosomes, suggesting that differentiation has gradually spread from the fusion point following the extension of recombination suppression. Our study illustrates an ongoing process of sex chromosome differentiation, providing empirical support for the theoretical model postulating that recombination suppression and differentiation proceed in a gradual manner in the very early stage of sex chromosome evolution.

  9. An Allometric Analysis of Sex and Sex Chromosome Dosage Effects on Subcortical Anatomy in Humans.

    PubMed

    Reardon, Paul Kirkpatrick; Clasen, Liv; Giedd, Jay N; Blumenthal, Jonathan; Lerch, Jason P; Chakravarty, M Mallar; Raznahan, Armin

    2016-02-24

    Structural neuroimaging of humans with typical and atypical sex-chromosome complements has established the marked influence of both Yand X-/Y-chromosome dosage on total brain volume (TBV) and identified potential cortical substrates for the psychiatric phenotypes associated with sex-chromosome aneuploidy (SCA). Here, in a cohort of 354 humans with varying karyotypes (XX, XY, XXX, XXY, XYY, XXYY, XXXXY), we investigate sex and SCA effects on subcortical size and shape; focusing on the striatum, pallidum and thalamus. We find large effect-size differences in the volume and shape of all three structures as a function of sex and SCA. We correct for TBV effects with a novel allometric method harnessing normative scaling rules for subcortical size and shape in humans, which we derive here for the first time. We show that all three subcortical volumes scale sublinearly with TBV among healthy humans, mirroring known relationships between subcortical volume and TBV among species. Traditional TBV correction methods assume linear scaling and can therefore invert or exaggerate sex and SCA effects on subcortical anatomy. Allometric analysis restricts sex-differences to: (1) greater pallidal volume (PV) in males, and (2) relative caudate head expansion and ventral striatum contraction in females. Allometric analysis of SCA reveals that supernumerary X- and Y-chromosomes both cause disproportionate reductions in PV, and coordinated deformations of striatopallidal shape. Our study provides a novel understanding of sex and sex-chromosome dosage effects on subcortical organization, using an allometric approach that can be generalized to other basic and clinical structural neuroimaging settings. Copyright © 2016 the authors 0270-6474/16/362438-11$15.00/0.

  10. Sex-chromosome differentiation and ‘sex races’ in the common frog (Rana temporaria)

    PubMed Central

    Rodrigues, Nicolas; Vuille, Yvan; Loman, Jon; Perrin, Nicolas

    2015-01-01

    Sex-chromosome differentiation was recently shown to vary among common frog populations in Fennoscandia, suggesting a trend of increased differentiation with latitude. By rearing families from two contrasted populations (respectively, from northern and southern Sweden), we show this disparity to stem from differences in sex-determination mechanisms rather than in XY-recombination patterns. Offspring from the northern population display equal sex ratios at metamorphosis, with phenotypic sexes that correlate strongly with paternal LG2 haplotypes (the sex chromosome); accordingly, Y haplotypes are markedly differentiated, with male-specific alleles and depressed diversity testifying to their smaller effective population size. In the southern population, by contrast, a majority of juveniles present ovaries at metamorphosis; only later in development do sex ratios return to equilibrium. Even at these later stages, phenotypic sexes correlate only mildly with paternal LG2 haplotypes; accordingly, there are no recognizable Y haplotypes. These distinct patterns of gonadal development fit the concept of ‘sex races’ proposed in the 1930s, with our two populations assigned to the ‘differentiated’ and ‘semi-differentiated’ races, respectively. Our results support the suggestion that ‘sex races’ differ in the genetic versus epigenetic components of sex determination. Analysing populations from the ‘undifferentiated race’ with high-density genetic maps should help to further test this hypothesis. PMID:25833852

  11. Sex-chromosome differentiation and 'sex races' in the common frog (Rana temporaria).

    PubMed

    Rodrigues, Nicolas; Vuille, Yvan; Loman, Jon; Perrin, Nicolas

    2015-05-07

    Sex-chromosome differentiation was recently shown to vary among common frog populations in Fennoscandia, suggesting a trend of increased differentiation with latitude. By rearing families from two contrasted populations (respectively, from northern and southern Sweden), we show this disparity to stem from differences in sex-determination mechanisms rather than in XY-recombination patterns. Offspring from the northern population display equal sex ratios at metamorphosis, with phenotypic sexes that correlate strongly with paternal LG2 haplotypes (the sex chromosome); accordingly, Y haplotypes are markedly differentiated, with male-specific alleles and depressed diversity testifying to their smaller effective population size. In the southern population, by contrast, a majority of juveniles present ovaries at metamorphosis; only later in development do sex ratios return to equilibrium. Even at these later stages, phenotypic sexes correlate only mildly with paternal LG2 haplotypes; accordingly, there are no recognizable Y haplotypes. These distinct patterns of gonadal development fit the concept of 'sex races' proposed in the 1930s, with our two populations assigned to the 'differentiated' and 'semi-differentiated' races, respectively. Our results support the suggestion that 'sex races' differ in the genetic versus epigenetic components of sex determination. Analysing populations from the 'undifferentiated race' with high-density genetic maps should help to further test this hypothesis. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  12. Chromosome banding in Amphibia. XVII. First demonstration of multiple sex chromosomes in amphibians: Eleutherodactylus maussi (Anura, leptodactylidae).

    PubMed

    Schmid, M; Steinlein, C; Feichtinger, W

    1992-03-01

    A cytogenetic study performed on a population of the South American leptodactylid frog Eleutherodactylus maussi revealed multiple sex chromosomes of the X1X1X2X2 female/X1X2Y male (= XXAA female/XXAY male) type. The diploid chromosome number is 2n = 36 in all females and 2n = 35 in most males. The multiple sex chromosomes originated by a centric fusion between the original Y chromosome and a large autosome. In male meiosis the X1X2Y (= XXAY) multiple sex chromosomes form a classical trivalent configuration. E. maussi is the first species discovered in the class Amphibia that is distinguished by a system of multiple sex chromosomes. Only one single male was found in the population with 2n = 36 chromosomes and lacking the Y-autosomal fusion. This karyotype (XYAA male) is interpreted as the ancestral condition, preceding the occurrence of the Y-autosome fusion.

  13. Sexually Antagonistic “Zygotic Drive” of the Sex Chromosomes

    PubMed Central

    Rice, William R.; Gavrilets, Sergey; Friberg, Urban

    2008-01-01

    Genomic conflict is perplexing because it causes the fitness of a species to decline rather than improve. Many diverse forms of genomic conflict have been identified, but this extant tally may be incomplete. Here, we show that the unusual characteristics of the sex chromosomes can, in principle, lead to a previously unappreciated form of sexual genomic conflict. The phenomenon occurs because there is selection in the heterogametic sex for sex-linked mutations that harm the sex of offspring that does not carry them, whenever there is competition among siblings. This harmful phenotype can be expressed as an antagonistic green-beard effect that is mediated by epigenetic parental effects, parental investment, and/or interactions among siblings. We call this form of genomic conflict sexually antagonistic “zygotic drive”, because it is functionally equivalent to meiotic drive, except that it operates during the zygotic and postzygotic stages of the life cycle rather than the meiotic and gametic stages. A combination of mathematical modeling and a survey of empirical studies is used to show that sexually antagonistic zygotic drive is feasible, likely to be widespread in nature, and that it can promote a genetic “arms race” between the homo- and heteromorphic sex chromosomes. This new category of genomic conflict has the potential to strongly influence other fundamental evolutionary processes, such as speciation and the degeneration of the Y and W sex chromosomes. It also fosters a new genetic hypothesis for the evolution of enigmatic fitness-reducing traits like the high frequency of spontaneous abortion, sterility, and homosexuality observed in humans. PMID:19096519

  14. 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.

  15. 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

  16. Genetic mapping of sex determination in a wild strawberry, Fragaria virginiana reveals earliest form of sex chromosome

    USDA-ARS?s Scientific Manuscript database

    The evolution of separate sexes (dioecy) from hermaphroditism is one of the major evolutionary transitions in plants and this transition can be accompanied by the development of sex chromosomes. However, we are now just beginning to gain insight into the initial stages of sex chromosome evolution vi...

  17. Confirmation of prenatal diagnosis of sex chromosome mosaicism.

    PubMed

    McFadden, D E; Kalousek, D K

    1989-04-01

    Prenatal diagnosis of mosaicism causes problems in interpretation and in genetic counselling. Part of the difficulty with any prenatal diagnosis of mosaicism is interpretation of results without knowing the exact origin, embryonic or extraembryonic, of the abnormal cell line. To confuse the issue in cases of prenatal diagnosis of 45,X/46,XY mosaicism is the recent demonstration that a diagnosis of 45,X/46,XY made prenatally is not necessarily associated with the same phenotype as when diagnosed postnatally. We present two cases of prenatal diagnosis of sex chromosome mosaicism (45,X/46,XY and 45,X/47,XYY). Posttermination examination of the phenotypically normal male fetuses and their placentas established that the placenta was the most likely source of the 45,X cell line. An approach to confirming the prenatal diagnosis of sex chromosome mosaicism and establishing its origin utilizing detailed cytogenetic examination of both fetus and placenta is suggested.

  18. Mouse model systems to study sex chromosome genes and behavior: relevance to humans.

    PubMed

    Cox, Kimberly H; Bonthuis, Paul J; Rissman, Emilie F

    2014-10-01

    Sex chromosome genes directly influence sex differences in behavior. The discovery of the Sry gene on the Y chromosome (Gubbay et al., 1990; Koopman et al., 1990) substantiated the sex chromosome mechanistic link to sex differences. Moreover, the pronounced connection between X chromosome gene mutations and mental illness produces a strong sex bias in these diseases. Yet, the dominant explanation for sex differences continues to be the gonadal hormones. Here we review progress made on behavioral differences in mouse models that uncouple sex chromosome complement from gonadal sex. We conclude that many social and cognitive behaviors are modified by sex chromosome complement, and discuss the implications for human research. Future directions need to include identification of the genes involved and interactions with these genes and gonadal hormones.

  19. Mouse model systems to study sex chromosome genes and behavior: relevance to humans

    PubMed Central

    Cox, Kimberly H.; Bonthuis, Paul J.; Rissman, Emilie F.

    2014-01-01

    Sex chromosome genes directly influence sex differences in behavior. The discovery of the Sry gene on the Y chromosome (Gubbay et al., 1990; Koopman et al., 1990) substantiated the sex chromosome mechanistic link to sex differences. Moreover, the pronounced connection between X chromosome gene mutations and mental illness produces a strong sex bias in these diseases. Yet, the dominant explanation for sex differences continues to be the gonadal hormones. Here we review progress made on behavioral differences in mouse models that uncouple sex chromosome complement from gonadal sex. We conclude that many social and cognitive behaviors are modified by sex chromosome complement, and discuss the implications for human research. Future directions need to include identification of the genes involved and interactions with these genes and gonadal hormones. PMID:24388960

  20. Cloning an expressed gene shared by the human sex chromosomes

    SciTech Connect

    Darling, S.M.; Banting, G.S.; Pym, B.; Wolfe, J.; Goodfellow, P.N.

    1986-01-01

    The existence of genes shared by mammalian sex chromosomes has been predicted on both evolutionary and functional grounds. However, the only experimental evidence for such genes in humans is the cell-surface antigen encoded by loci on the X and Y chromosomes (MIC2X and MIC2Y, respectively), which is recognized by the monoclonal antibody 12E7. Using the bacteriophage lambdagt11 expression system in Escherichia coli and immunoscreening techniques, the authors have isolated a cDNA clone whose primary product is recognized by 12E7. Southern blot analysis using somatic cell hybrids containing only the human X or Y chromosomes shows that the sequences reacting with the cDNA clone are localized to the sex chromosomes. In addition, the clone hybridizes to DNAs isolated from mouse cells that have been transfected with human DNA and selected for 12E7 expression on the fluorescence-activated cell sorter. The authors conclude that the cDNA clone encodes the 12E7 antigen, which is the primary product of the MIC2 loci. The clone was used to explore sequence homology between MIC2X and MIC2Y; these loci are closely related, if not identical.

  1. Histone H3 trimethylation at lysine 9 marks the inactive metaphase X chromosome in the marsupial Monodelphis domestica.

    PubMed

    Zakharova, Irina S; Shevchenko, Alexander I; Shilov, Alexander G; Nesterova, Tatyana B; Vandeberg, John L; Zakian, Suren M

    2011-04-01

    In somatic cells of female marsupial and eutherian mammals, X chromosome inactivation (XCI) occurs. XCI results in the transcriptional silencing of one of the two X chromosomes and is accompanied by specific covalent histone modifications attributable to the inactive chromatin state. Because data about repressed chromatin of the inactive X chromosome (Xi) in marsupials are sparse, we examined in more detail the distribution of active and inactive chromatin markers on metaphase X chromosomes of an American marsupial, Monodelphis domestica. Consistent with data reported previously both for eutherian and marsupial mammals, we found that the Xi of M. domestica lacks active histone markers-H3K4 dimethylation and H3K9 acetylation. We did not observe on metaphase spreads enrichment of the Xi with H3K27 trimethylation which is involved in XCI in eutherians and was detected on the Xi in the interphase nuclei of mature female M. domestica in an earlier study. Moreover, we found that the Xi of M. domestica was specifically marked with H3K9 trimethylation, which is known to be a component of the Xi chromatin in eutherians and is involved in both marsupials and eutherians in meiotic sex chromosome inactivation which has been proposed as an ancestral mechanism of XCI.

  2. Non-homologous sex chromosomes in two geckos (Gekkonidae: Gekkota) with female heterogamety.

    PubMed

    Matsubara, Kazumi; Gamble, Tony; Matsuda, Yoichi; Zarkower, David; Sarre, Stephen D; Georges, Arthur; Graves, Jennifer A Marshall; Ezaz, Tariq

    2014-01-01

    Evaluating homology between the sex chromosomes of different species is an important first step in deducing the origins and evolution of sex-determining mechanisms in a clade. Here, we describe the preparation of Z and W chromosome paints via chromosome microdissection from the Australian marbled gecko (Christinus marmoratus) and their subsequent use in evaluating sex chromosome homology with the ZW chromosomes of the Kwangsi gecko (Gekko hokouensis) from eastern Asia. We show that the ZW sex chromosomes of C. marmoratus and G. hokouensis are not homologous and represent independent origins of female heterogamety within the Gekkonidae. We also show that the C. marmoratus Z and W chromosomes are genetically similar to each other as revealed by C-banding, comparative genomic hybridization, and the reciprocal painting of Z and W chromosome probes. This implies that sex chromosomes in C. marmoratus are at an early stage of differentiation, suggesting a recent origin.

  3. Introduction of Trojan sex chromosomes to boost population growth.

    PubMed

    Cotton, Samuel; Wedekind, Claus

    2007-11-07

    Conservation programs that deal with small or declining populations often aim at a rapid increase of population size to above-critical levels in order to avoid the negative effects of demographic stochasticity and genetic problems like inbreeding depression, fixation of deleterious alleles, or a general loss of genetic variability and hence of evolutionary potential. In some situations, population growth is determined by the number of females available for reproduction, and manipulation of family sex ratios towards more daughters has beneficial effects. If sex determination is predominantly genetic but environmentally reversible, as is the case in many amphibia, reptiles, and fish, Trojan sex chromosomes could be introduced into populations in order to change sex ratios towards more females. We analyse the possible consequences for the introduction of XX-males (XX individuals that have been changed to phenotypic males in a XY/XX sex determination system) and ZW males, WW males, or WW females (in a ZZ/ZW sex determination system). We find that the introduction of WW individuals can be most effective for an increase of population growth, especially if the induced sex change has little or no effect on viability.

  4. Comparative Sex Chromosome Genomics in Snakes: Differentiation, Evolutionary Strata, and Lack of Global Dosage Compensation

    PubMed Central

    Zektser, Yulia; Mahajan, Shivani; Bachtrog, Doris

    2013-01-01

    Snakes exhibit genetic sex determination, with female heterogametic sex chromosomes (ZZ males, ZW females). Extensive cytogenetic work has suggested that the level of sex chromosome heteromorphism varies among species, with Boidae having entirely homomorphic sex chromosomes, Viperidae having completely heteromorphic sex chromosomes, and Colubridae showing partial differentiation. Here, we take a genomic approach to compare sex chromosome differentiation in these three snake families. We identify homomorphic sex chromosomes in boas (Boidae), but completely heteromorphic sex chromosomes in both garter snakes (Colubridae) and pygmy rattlesnake (Viperidae). Detection of W-linked gametologs enables us to establish the presence of evolutionary strata on garter and pygmy rattlesnake sex chromosomes where recombination was abolished at different time points. Sequence analysis shows that all strata are shared between pygmy rattlesnake and garter snake, i.e., recombination was abolished between the sex chromosomes before the two lineages diverged. The sex-biased transmission of the Z and its hemizygosity in females can impact patterns of molecular evolution, and we show that rates of evolution for Z-linked genes are increased relative to their pseudoautosomal homologs, both at synonymous and amino acid sites (even after controlling for mutational biases). This demonstrates that mutation rates are male-biased in snakes (male-driven evolution), but also supports faster-Z evolution due to differential selective effects on the Z. Finally, we perform a transcriptome analysis in boa and pygmy rattlesnake to establish baseline levels of sex-biased expression in homomorphic sex chromosomes, and show that heteromorphic ZW chromosomes in rattlesnakes lack chromosome-wide dosage compensation. Our study provides the first full scale overview of the evolution of snake sex chromosomes at the genomic level, thus greatly expanding our knowledge of reptilian and vertebrate sex chromosomes

  5. Comparative sex chromosome genomics in snakes: differentiation, evolutionary strata, and lack of global dosage compensation.

    PubMed

    Vicoso, Beatriz; Emerson, J J; Zektser, Yulia; Mahajan, Shivani; Bachtrog, Doris

    2013-01-01

    Snakes exhibit genetic sex determination, with female heterogametic sex chromosomes (ZZ males, ZW females). Extensive cytogenetic work has suggested that the level of sex chromosome heteromorphism varies among species, with Boidae having entirely homomorphic sex chromosomes, Viperidae having completely heteromorphic sex chromosomes, and Colubridae showing partial differentiation. Here, we take a genomic approach to compare sex chromosome differentiation in these three snake families. We identify homomorphic sex chromosomes in boas (Boidae), but completely heteromorphic sex chromosomes in both garter snakes (Colubridae) and pygmy rattlesnake (Viperidae). Detection of W-linked gametologs enables us to establish the presence of evolutionary strata on garter and pygmy rattlesnake sex chromosomes where recombination was abolished at different time points. Sequence analysis shows that all strata are shared between pygmy rattlesnake and garter snake, i.e., recombination was abolished between the sex chromosomes before the two lineages diverged. The sex-biased transmission of the Z and its hemizygosity in females can impact patterns of molecular evolution, and we show that rates of evolution for Z-linked genes are increased relative to their pseudoautosomal homologs, both at synonymous and amino acid sites (even after controlling for mutational biases). This demonstrates that mutation rates are male-biased in snakes (male-driven evolution), but also supports faster-Z evolution due to differential selective effects on the Z. Finally, we perform a transcriptome analysis in boa and pygmy rattlesnake to establish baseline levels of sex-biased expression in homomorphic sex chromosomes, and show that heteromorphic ZW chromosomes in rattlesnakes lack chromosome-wide dosage compensation. Our study provides the first full scale overview of the evolution of snake sex chromosomes at the genomic level, thus greatly expanding our knowledge of reptilian and vertebrate sex chromosomes

  6. Chromosomal phylogeny of Vampyressine bats (Chiroptera, Phyllostomidae) with description of two new sex chromosome systems.

    PubMed

    Gomes, Anderson José Baia; Nagamachi, Cleusa Yoshiko; Rodrigues, Luis Reginaldo Ribeiro; Benathar, Thayse Cristine Melo; Ribas, Talita Fernanda Augusto; O'Brien, Patricia Caroline Mary; Yang, Fengtang; Ferguson-Smith, Malcolm Andrew; Pieczarka, Julio Cesar

    2016-06-04

    The subtribe Vampyressina (sensu Baker et al. 2003) encompasses approximately 43 species and seven genera and is a recent and diversified group of New World leaf-nosed bats specialized in fruit eating. The systematics of this group continues to be debated mainly because of the lack of congruence between topologies generated by molecular and morphological data. We analyzed seven species of all genera of vampyressine bats by multidirectional chromosome painting, using whole-chromosome-painting probes from Carollia brevicauda and Phyllostomus hastatus. Phylogenetic analyses were performed using shared discrete chromosomal segments as characters and the Phylogenetic Analysis Using Parsimony (PAUP) software package, using Desmodontinae as outgroup. We also used the Tree Analysis Using New Technology (TNT) software. The result showed a well-supported phylogeny congruent with molecular topologies regarding the sister taxa relationship of Vampyressa and Mesophylla genera, as well as the close relationship between the genus Chiroderma and Vampyriscus. Our results supported the hypothesis that all genera of this subtribe have compound sex chromosome systems that originated from an X-autosome translocation, an ancestral condition observed in the Stenodermatinae. Additional rearrangements occurred independently in the genus Vampyressa and Mesophylla yielding the X1X1X2X2/X1X2Y sex chromosome system. This work presents additional data supporting the hypothesis based on molecular studies regarding the polyphyly of the genus Vampyressa and its sister relationship to Mesophylla.

  7. Chromosome-wide mechanisms to decouple gene expression from gene dose during sex-chromosome evolution

    PubMed Central

    Wheeler, Bayly S; Anderson, Erika; Frøkjær-Jensen, Christian; Bian, Qian; Jorgensen, Erik; Meyer, Barbara J

    2016-01-01

    Changes in chromosome number impair fitness by disrupting the balance of gene expression. Here we analyze mechanisms to compensate for changes in gene dose that accompanied the evolution of sex chromosomes from autosomes. Using single-copy transgenes integrated throughout the Caenorhabditis elegans genome, we show that expression of all X-linked transgenes is balanced between XX hermaphrodites and XO males. However, proximity of a dosage compensation complex (DCC) binding site (rex site) is neither necessary to repress X-linked transgenes nor sufficient to repress transgenes on autosomes. Thus, X is broadly permissive for dosage compensation, and the DCC acts via a chromosome-wide mechanism to balance transcription between sexes. In contrast, no analogous X-chromosome-wide mechanism balances transcription between X and autosomes: expression of compensated hermaphrodite X-linked transgenes is half that of autosomal transgenes. Furthermore, our results argue against an X-chromosome dosage compensation model contingent upon rex-directed positioning of X relative to the nuclear periphery. DOI: http://dx.doi.org/10.7554/eLife.17365.001 PMID:27572259

  8. Tracking the evolution of sex chromosome systems in Melanoplinae grasshoppers through chromosomal mapping of repetitive DNA sequences

    PubMed Central

    2013-01-01

    Background The accumulation of repetitive DNA during sex chromosome differentiation is a common feature of many eukaryotes and becomes more evident after recombination has been restricted or abolished. The accumulated repetitive sequences include multigene families, microsatellites, satellite DNAs and mobile elements, all of which are important for the structural remodeling of heterochromatin. In grasshoppers, derived sex chromosome systems, such as neo-XY♂/XX♀ and neo-X1X2Y♂/X1X1X2X2♀, are frequently observed in the Melanoplinae subfamily. However, no studies concerning the evolution of sex chromosomes in Melanoplinae have addressed the role of the repetitive DNA sequences. To further investigate the evolution of sex chromosomes in grasshoppers, we used classical cytogenetic and FISH analyses to examine the repetitive DNA sequences in six phylogenetically related Melanoplinae species with X0♂/XX♀, neo-XY♂/XX♀ and neo-X1X2Y♂/X1X1X2X2♀ sex chromosome systems. Results Our data indicate a non-spreading of heterochromatic blocks and pool of repetitive DNAs (C0t-1 DNA) in the sex chromosomes; however, the spreading of multigene families among the neo-sex chromosomes of Eurotettix and Dichromatos was remarkable, particularly for 5S rDNA. In autosomes, FISH mapping of multigene families revealed distinct patterns of chromosomal organization at the intra- and intergenomic levels. Conclusions These results suggest a common origin and subsequent differential accumulation of repetitive DNAs in the sex chromosomes of Dichromatos and an independent origin of the sex chromosomes of the neo-XY and neo-X1X2Y systems. Our data indicate a possible role for repetitive DNAs in the diversification of sex chromosome systems in grasshoppers. PMID:23937327

  9. Tracking the evolution of sex chromosome systems in Melanoplinae grasshoppers through chromosomal mapping of repetitive DNA sequences.

    PubMed

    Palacios-Gimenez, Octavio M; Castillo, Elio R; Martí, Dardo A; Cabral-de-Mello, Diogo C

    2013-08-09

    The accumulation of repetitive DNA during sex chromosome differentiation is a common feature of many eukaryotes and becomes more evident after recombination has been restricted or abolished. The accumulated repetitive sequences include multigene families, microsatellites, satellite DNAs and mobile elements, all of which are important for the structural remodeling of heterochromatin. In grasshoppers, derived sex chromosome systems, such as neo-XY♂/XX♀ and neo-X1X2Y♂/X1X1X2X2♀, are frequently observed in the Melanoplinae subfamily. However, no studies concerning the evolution of sex chromosomes in Melanoplinae have addressed the role of the repetitive DNA sequences. To further investigate the evolution of sex chromosomes in grasshoppers, we used classical cytogenetic and FISH analyses to examine the repetitive DNA sequences in six phylogenetically related Melanoplinae species with X0♂/XX♀, neo-XY♂/XX♀ and neo-X1X2Y♂/X1X1X2X2♀ sex chromosome systems. Our data indicate a non-spreading of heterochromatic blocks and pool of repetitive DNAs (C0t-1 DNA) in the sex chromosomes; however, the spreading of multigene families among the neo-sex chromosomes of Eurotettix and Dichromatos was remarkable, particularly for 5S rDNA. In autosomes, FISH mapping of multigene families revealed distinct patterns of chromosomal organization at the intra- and intergenomic levels. These results suggest a common origin and subsequent differential accumulation of repetitive DNAs in the sex chromosomes of Dichromatos and an independent origin of the sex chromosomes of the neo-XY and neo-X1X2Y systems. Our data indicate a possible role for repetitive DNAs in the diversification of sex chromosome systems in grasshoppers.

  10. Microdissection of the Y chromosome and fluorescence in situ hybridization analysis of the sex chromosomes of lake trout, Salvelinus namaycush.

    PubMed

    Reed, K M; Bohlander, S K; Phillips, R B

    1995-06-01

    Lake trout, Salvelinus namaycush, is one of the few salmonids with morphologically differentiated sex chromosomes. Genetic analysis suggested that the sex-determining region of this species lies on the short arm of the Y chromosome. The differential arm of the Y chromosome was microdissected and the resulting DNA amplified in a sequence-independent manner. Amplified DNA was biotin labeled as a probe for fluorescence in situ hybridization (FISH). Strong hybridization signals were seen covering defined regions of both the Y and X chromosomes. Homeologous chromosomes of the ancestrally tetraploid genome were not identified by FISH with the Y probe, indicating diploidization of this region of the genome.

  11. Cell-free DNA screening and sex chromosome aneuploidies.

    PubMed

    Mennuti, Michael T; Chandrasekaran, Suchitra; Khalek, Nahla; Dugoff, Lorraine

    2015-10-01

    Cell-free DNA (cfDNA) testing is increasingly being used to screen pregnant women for fetal aneuploidies. This technology may also identify fetal sex and can be used to screen for sex chromosome aneuploidies (SCAs). Physicians offering this screening will need to be prepared to offer comprehensive prenatal counseling about these disorders to an increasing number of patients. The purpose of this article is to consider the source of information to use for counseling, factors in parental decision-making, and the performance characteristics of cfDNA testing in screening for SCAs. Discordance between ultrasound examination and cfDNA results regarding fetal sex is also discussed. © 2015 John Wiley & Sons, Ltd.

  12. The contrasting role of heterochromatin in the differentiation of sex chromosomes: an overview from Neotropical fishes.

    PubMed

    Cioffi, M B; Moreira-Filho, O; Almeida-Toledo, L F; Bertollo, L A C

    2012-05-01

    During the evolutionary process of the sex chromosomes, a general principle that arises is that cessation or a partial restriction of recombination between the sex chromosome pair is necessary. Data from phylogenetically distinct organisms reveal that this phenomenon is frequently associated with the accumulation of heterochromatin in the sex chromosomes. Fish species emerge as excellent models to study this phenomenon because they have much younger sex chromosomes compared to higher vertebrates and many other organisms making it possible to follow their steps of differentiation. In several Neotropical fish species, the heterochromatinization, accompanied by amplification of tandem repeats, represents an important step in the morphological differentiation of simple sex chromosome systems, especially in the ZZ/ZW sex systems. In contrast, multiple sex chromosome systems have no additional increase of heterochromatin in the chromosomes. Thus, the initial stage of differentiation of the multiple sex chromosome systems seems to be associated with proper chromosomal rearrangements, whereas the simple sex chromosome systems have an accumulation of heterochromatin. In this review, attention has been drawn to this contrasting role of heterochromatin in the differentiation of simple and multiple sex chromosomes of Neotropical fishes, highlighting their surprising evolutionary dynamism.

  13. The role of sex chromosomes in sexual dimorphism: discordance between molecular and phenotypic data.

    PubMed

    Dean, R; Mank, J E

    2014-07-01

    In addition to initial sex determination, genes on the sex chromosomes are theorized to play a particularly important role in phenotypic differences between males and females. Sex chromosomes in many species display molecular signatures consistent with these theoretical predictions, particularly through sex-specific gene expression. However, the phenotypic implications of this molecular signature are unresolved, and the role of the sex chromosomes in quantitative genetic studies of phenotypic sex differences is largely equivocal. In this article, we examine molecular and phenotypic data in the light of theoretical predictions about masculinization and feminization of the sex chromosomes. Additionally, we discuss the role of genetic and regulatory complexities in the genome–phenotype relationship, and ultimately how these affect the overall role of the sex chromosomes in sex differences.

  14. Chromosomal Mapping of Repetitive DNAs in Characidium (Teleostei, Characiformes): Genomic Organization and Diversification of ZW Sex Chromosomes.

    PubMed

    Scacchetti, Priscilla C; Utsunomia, Ricardo; Pansonato-Alves, José C; Vicari, Marcelo R; Artoni, Roberto F; Oliveira, Claudio; Foresti, Fausto

    2015-01-01

    The speciose neotropical genus Characidium has proven to be a good model for cytogenetic exploration. Representatives of this genus often have a conserved diploid chromosome number; some species exhibit a highly differentiated ZZ/ZW sex chromosome system, while others do not show any sex-related chromosome heteromorphism. In this study, chromosome painting using a W-specific probe and comparative chromosome mapping of repetitive sequences, including ribosomal clusters and 4 microsatellite motifs - (CA)15, (GA)15, (CG)15, and (TTA)10 -, were performed in 6 Characidium species, 5 of which possessed a heteromorphic ZW sex chromosome system. The W-specific probe showed hybridization signals on the W chromosome of all analyzed species, indicating homology among the W chromosomes. Remarkably, a single major rDNA-bearing chromosome pair was found in all species. The 18S rDNA localized to the sex chromosomes in C. lanei, C. timbuiense and C. pterostictum, while the major rDNA localized to one autosome pair in C. vidali and C. gomesi. In contrast, the number of 5S rDNA-bearing chromosomes varied. Notably, minor ribosomal clusters were identified in the W chromosome of C. vidali. Microsatellites were widely distributed across almost all chromosomes of the karyotypes, with a greater accumulation in the subtelomeric regions. However, clear differences in the abundance of each motif were detected in each species. In addition, the Z and W chromosomes showed the differential accumulation of distinct motifs. Our results revealed variability in the distribution of repetitive DNA sequences and their possible association with sex chromosome diversification in Characidium species.

  15. Non-random autosome segregation: a stepping stone for the evolution of sex chromosome complexes? Sex-biased transmission of autosomes could facilitate the spread of antagonistic alleles, and generate sex-chromosome systems with multiple X or Y chromosomes.

    PubMed

    Schwander, Tanja; Beukeboom, Leo W

    2011-02-01

    A new study in Caenorhabditis elegans shows that homologous autosomes segregate non-randomly with the sex chromosome in the heterogametic sex. Segregation occurs according to size, small autosomes segregating with, and large autosomes segregating away from the X-chromosome. Such sex-biased transmission of autosomes could facilitate the spread of sexually antagonistic alleles whose effects favor the fitness of one sex at the expense of the other. This may provide a first step toward the evolution of new sex determination systems.

  16. Rapid de novo evolution of X chromosome dosage compensation in Silene latifolia, a plant with young sex chromosomes.

    PubMed

    Muyle, Aline; Zemp, Niklaus; Deschamps, Clothilde; Mousset, Sylvain; Widmer, Alex; Marais, Gabriel A B

    2012-01-01

    Silene latifolia is a dioecious plant with heteromorphic sex chromosomes that have originated only ∼10 million years ago and is a promising model organism to study sex chromosome evolution in plants. Previous work suggests that S. latifolia XY chromosomes have gradually stopped recombining and the Y chromosome is undergoing degeneration as in animal sex chromosomes. However, this work has been limited by the paucity of sex-linked genes available. Here, we used 35 Gb of RNA-seq data from multiple males (XY) and females (XX) of an S. latifolia inbred line to detect sex-linked SNPs and identified more than 1,700 sex-linked contigs (with X-linked and Y-linked alleles). Analyses using known sex-linked and autosomal genes, together with simulations indicate that these newly identified sex-linked contigs are reliable. Using read numbers, we then estimated expression levels of X-linked and Y-linked alleles in males and found an overall trend of reduced expression of Y-linked alleles, consistent with a widespread ongoing degeneration of the S. latifolia Y chromosome. By comparing expression intensities of X-linked alleles in males and females, we found that X-linked allele expression increases as Y-linked allele expression decreases in males, which makes expression of sex-linked contigs similar in both sexes. This phenomenon is known as dosage compensation and has so far only been observed in evolutionary old animal sex chromosome systems. Our results suggest that dosage compensation has evolved in plants and that it can quickly evolve de novo after the origin of sex chromosomes.

  17. Birth of a W sex chromosome by horizontal transfer of Wolbachia bacterial symbiont genome.

    PubMed

    Leclercq, Sébastien; Thézé, Julien; Chebbi, Mohamed Amine; Giraud, Isabelle; Moumen, Bouziane; Ernenwein, Lise; Grève, Pierre; Gilbert, Clément; Cordaux, Richard

    2016-12-27

    Sex determination is a fundamental developmental pathway governing male and female differentiation, with profound implications for morphology, reproductive strategies, and behavior. In animals, sex differences between males and females are generally determined by genetic factors carried by sex chromosomes. Sex chromosomes are remarkably variable in origin and can differ even between closely related species, indicating that transitions occur frequently and independently in different groups of organisms. The evolutionary causes underlying sex chromosome turnover are poorly understood, however. Here we provide evidence indicating that Wolbachia bacterial endosymbionts triggered the evolution of new sex chromosomes in the common pillbug Armadillidium vulgare We identified a 3-Mb insert of a feminizing Wolbachia genome that was recently transferred into the pillbug nuclear genome. The Wolbachia insert shows perfect linkage to the female sex, occurs in a male genetic background (i.e., lacking the ancestral W female sex chromosome), and is hemizygous. Our results support the conclusion that the Wolbachia insert is now acting as a female sex-determining region in pillbugs, and that the chromosome carrying the insert is a new W sex chromosome. Thus, bacteria-to-animal horizontal genome transfer represents a remarkable mechanism underpinning the birth of sex chromosomes. We conclude that sex ratio distorters, such as Wolbachia endosymbionts, can be powerful agents of evolutionary transitions in sex determination systems in animals.

  18. Birth of a W sex chromosome by horizontal transfer of Wolbachia bacterial symbiont genome

    PubMed Central

    Leclercq, Sébastien; Thézé, Julien; Chebbi, Mohamed Amine; Giraud, Isabelle; Moumen, Bouziane; Ernenwein, Lise; Grève, Pierre; Cordaux, Richard

    2016-01-01

    Sex determination is a fundamental developmental pathway governing male and female differentiation, with profound implications for morphology, reproductive strategies, and behavior. In animals, sex differences between males and females are generally determined by genetic factors carried by sex chromosomes. Sex chromosomes are remarkably variable in origin and can differ even between closely related species, indicating that transitions occur frequently and independently in different groups of organisms. The evolutionary causes underlying sex chromosome turnover are poorly understood, however. Here we provide evidence indicating that Wolbachia bacterial endosymbionts triggered the evolution of new sex chromosomes in the common pillbug Armadillidium vulgare. We identified a 3-Mb insert of a feminizing Wolbachia genome that was recently transferred into the pillbug nuclear genome. The Wolbachia insert shows perfect linkage to the female sex, occurs in a male genetic background (i.e., lacking the ancestral W female sex chromosome), and is hemizygous. Our results support the conclusion that the Wolbachia insert is now acting as a female sex-determining region in pillbugs, and that the chromosome carrying the insert is a new W sex chromosome. Thus, bacteria-to-animal horizontal genome transfer represents a remarkable mechanism underpinning the birth of sex chromosomes. We conclude that sex ratio distorters, such as Wolbachia endosymbionts, can be powerful agents of evolutionary transitions in sex determination systems in animals. PMID:27930295

  19. Different autosomes evolved into sex chromosomes in the sister genera of Salix and Populus.

    PubMed

    Hou, Jing; Ye, Ning; Zhang, Defang; Chen, Yingnan; Fang, Lecheng; Dai, Xiaogang; Yin, Tongming

    2015-03-13

    Willows (Salix) and poplars (Populus) are dioecious plants in Salicaceae family. Sex chromosome in poplar genome was consistently reported to be associated with chromosome XIX. In contrast to poplar, this study revealed that chromosome XV was sex chromosome in willow. Previous studies revealed that both ZZ/ZW and XX/XY sex-determining systems could be present in some species of Populus. In this study, sex of S. suchowensis was found to be determined by the ZW system in which the female was the heterogametic gender. Gene syntenic and collinear comparisons revealed macrosynteny between sex chromosomes and the corresponding autosomes between these two lineages. By contrast, no syntenic segments were found to be shared between poplar's and willow's sex chromosomes. Syntenic analysis also revealed substantial chromosome rearrangements between willow's alternate sex chromatids. Since willow and poplar originate from a common ancestor, we proposed that evolution of autosomes into sex chromosomes in these two lineages occurred after their divergence. Results of this study indicate that sex chromosomes in Salicaceae are still at the early stage of evolutionary divergence. Additionally, this study provided valuable information for better understanding the genetics and evolution of sex chromosome in dioecious plants.

  20. Multiple sex chromosomes in the light of female meiotic drive in amniote vertebrates.

    PubMed

    Pokorná, Martina; Altmanová, Marie; Kratochvíl, Lukáš

    2014-04-01

    It is notable that the occurrence of multiple sex chromosomes differs significantly between major lineages of amniote vertebrates. In this respect, birds are especially conspicuous, as multiple sex chromosomes have not been observed in this lineage so far. On the other hand, in mammals, multiple sex chromosomes have evolved many times independently. We hypothesize that this contrast can be related to the different involvement of sex-specific sex chromosomes in female meiosis subjected to the female meiotic drive under male versus female heterogamety. Essentially, the male-specific Y chromosome is not involved in female meiosis and is therefore sheltered against the effects of the female meiotic drive affecting the X chromosome and autosomes. Conversely, the Z and W sex chromosomes are both present in female meiosis. Nonrandom segregation of these sex chromosomes as a consequence of their rearrangements connected with the emergence of multiple sex chromosomes would result in a biased sex ratio, which should be penalized by selection. Therefore, the emergence of multiple sex chromosomes should be less constrained in the lineages with male rather than female heterogamety. Our broader phylogenetic comparison across amniotes supports this prediction. We suggest that our results are consistent with the widespread occurrence of female meiotic drive in amniotes.

  1. A polymorphic pseudoautosomal boundary in the Carica papaya sex chromosomes.

    PubMed

    Lappin, Fiona M; Medert, Charles M; Hawkins, Kevin K; Mardonovich, Sandra; Wu, Meng; Moore, Richard C

    2015-08-01

    Sex chromosomes are defined by a non-recombining sex-determining region (SDR) flanked by one or two pseudoautosomal regions (PARs). The genetic composition and evolutionary dynamics of the PAR is also influenced by its linkage to the differentiated non-recombining SDR; however, understanding the effects of this linkage requires a precise definition of the PAR boundary. Here, we took a molecular population genetic approach to further refine the location of the PAR boundary of the evolutionary young sex chromosomes of the tropical plant, Carica papaya. We were able to map the position of the papaya PAR boundary A to a 100-kb region between two genetic loci approximately 2 Mb upstream of the previously genetically identified PAR boundary. Furthermore, this boundary is polymorphic within natural populations of papaya, with an approximately 100-130 kb expansion of the non-recombining SDR found in 16 % of individuals surveyed. The expansion of the PAR boundary in one Y haplotype includes at least one additional gene. Homologs of this gene are involved in male gametophyte and pollen development in other plant species.

  2. Recent gene-capture on the UV sex chromosomes of the moss Ceratodon purpureus.

    PubMed

    McDaniel, Stuart F; Neubig, Kurt M; Payton, Adam C; Quatrano, Ralph S; Cove, David J

    2013-10-01

    Sex chromosomes evolve from ordinary autosomes through the expansion and subsequent degeneration of a region of suppressed recombination that is inherited through one sex. Here we investigate the relative timing of these processes in the UV sex chromosomes of the moss Ceratodon purpureus using molecular population genetic analyses of eight newly discovered sex-linked loci. In this system, recombination is suppressed on both the female-transmitted (U) sex chromosome and the male-transmitted (V) chromosome. Genes on both chromosomes therefore should show the deleterious effects of suppressed recombination and sex-limited transmission, while purifying selection should maintain homologs of genes essential for both sexes on both sex chromosomes. Based on analyses of eight sex-linked loci, we show that the nonrecombining portions of the U and V chromosomes expanded in at least two events (~0.6-1.3 MYA and ~2.8-3.5 MYA), after the divergence of C. purpureus from its dioecious sister species, Trichodon cylindricus and Cheilothela chloropus. Both U- and V-linked copies showed reduced nucleotide diversity and limited population structure, compared to autosomal loci, suggesting that the sex chromosomes experienced more recent selective sweeps that the autosomes. Collectively these results highlight the dynamic nature of gene composition and molecular evolution on nonrecombining portions of the U and V sex chromosomes.

  3. Increased Number of Sex Chromosomes Affects Height in a Nonlinear Fashion: A Study of 305 Patients With Sex Chromosome Aneuploidy

    PubMed Central

    Ottesen, Anne Marie; Aksglaede, Lise; Garn, Inger; Tartaglia, Nicole; Tassone, Flora; Gravholt, Claus H.; Bojesen, Anders; Sørensen, Kaspar; Jørgensen, Niels; Meyts, Ewa Rajpert-De; Gerdes, Tommy; Lind, Anne-Marie; Kjaergaard, Susanne; Juul, Anders

    2017-01-01

    Tall stature and eunuchoid body proportions characterize patients with 47,XXY Klinefelter syndrome, whereas patients with 45,X Turner syndrome are characterized by impaired growth. Growth is relatively well characterized in these two syndromes, while few studies describe the growth of patients with higher grade sex chromosome aneuploidies. It has been proposed that tall stature in sex chromosome aneuploidy is related to an overexpression of SHOX, although the copy number of SHOX has not been evaluated in previous studies. Our aims were therefore: (1) to assess stature in 305 patients with sex chromosome aneuploidy and (2) to determine the number of SHOX copies in a subgroup of these patients (n =255) these patients and 74 healthy controls. Median height standard deviation scores in 46,XX males (n =6) were −1.2 (−2.8 to 0.3), +0.9 (−2.2 to + 4.6) in 47,XXY (n =129), +1.3 (−1.8 to +4.9) in 47,XYY (n =44), +1.1 (−1.9 to +3.4) in 48,XXYY (n =45), +1.8 (−2.0 to +3.2) in 48,XXXY (n =9), and −1.8 (−4.2 to −0.1) in 49,XXXXY (n =10). Median height standard deviation scores in patients with 45,X (n =6) were −2.6 (−4.1 to −1.6), +0.7 (−0.9 to +3.2) in 47,XXX (n =−40), −0.6 (−1.9 to +2.1) in 48,XXXX (n =13), and −1.0 (−3.5 to −0.8) in 49,XXXXX (n =3). Height increased with an increasing number of extra X or Y chromosomes, except in males with five, and in females with four or five sex chromosomes, consistent with a nonlinear effect on height. PMID:20425825

  4. Molecular cytogenetic search for cryptic sex chromosomes in painted turtles Chrysemys picta.

    PubMed

    Valenzuela, Nicole; Badenhorst, Daleen; Montiel, Eugenia E; Literman, Robert

    2014-01-01

    Sex determination is triggered by factors ranging from genotypic (GSD) to environmental (ESD), or both GSD + EE (GSD susceptible to environmental effects), and its evolution remains enigmatic. The presence/absence of sex chromosomes purportedly separates species at the ESD end of the continuum from the rest (GSD and GSD + EE) because the evolutionary dynamics of sex chromosomes and autosomes differ. However, studies suggest that turtles with temperature-dependent sex determination (TSD) are cryptically GSD and possess sex chromosomes. Here, we test this hypothesis in painted turtles Chrysemys picta (TSD), using comparative-genome-hybridization (CGH), a technique known to detect morphologically indistinguishable sex chromosomes in other turtles and reptiles. Our results show no evidence for the existence of sex chromosomes in painted turtles. While it remains plausible that cryptic sex chromosomes may exist in TSD turtles that are characterized by minor genetic differences that cannot be detected at the resolution of CGH, previous attempts have failed to identify sex-specific markers. Genomic sequencing should prove useful in providing conclusive evidence in this regard. If such efforts uncover sex chromosomes in TSD turtles, it may reveal the existence of a fundamental constraint for the evolution of a full spectrum of sex determination (from pure GSD to pure TSD) that is predicted theoretically. Finding sex chromosomes in ESD organisms would question whether pure ESD mechanisms exist at all in nature, or whether those systems currently considered pure ESD simply await the characterization of an underlying GSD architecture.

  5. Extraordinary Diversity in the Origins of Sex Chromosomes in Anurans Inferred from Comparative Gene Mapping.

    PubMed

    Uno, Yoshinobu; Nishida, Chizuko; Takagi, Chiyo; Igawa, Takeshi; Ueno, Naoto; Sumida, Masayuki; Matsuda, Yoichi

    2015-01-01

    Sex determination in frogs (anurans) is genetic and includes both male and female heterogamety. However, the origins of the sex chromosomes and their differentiation processes are poorly known. To investigate diversity in the origins of anuran sex chromosomes, we compared the chromosomal locations of sex-linked genes in 4 species: the African clawed frog (Xenopus laevis), the Western clawed frog (Silurana/X. tropicalis), the Japanese bell-ring frog (Buergeria buergeri), and the Japanese wrinkled frog (Rana rugosa). Comparative mapping data revealed that the sex chromosomes of X. laevis, X. tropicalis and R. rugosa are different chromosome pairs; however, the sex chromosomes of X. tropicalis and B. buergeri are homologous, although this may represent distinct evolutionary origins. We also examined the status of sex chromosomal differentiation in B. buergeri, which possesses heteromorphic ZW sex chromosomes, using comparative genomic hybridization and chromosome painting with DNA probes from the microdissected W chromosome. At least 3 rearrangement events have occurred in the proto-W chromosome: deletion of the nucleolus organizer region and a paracentric inversion followed by amplification of non-W-specific repetitive sequences.

  6. New insights into sex chromosome evolution in anole lizards (Reptilia, Dactyloidae).

    PubMed

    Giovannotti, M; Trifonov, V A; Paoletti, A; Kichigin, I G; O'Brien, P C M; Kasai, F; Giovagnoli, G; Ng, B L; Ruggeri, P; Cerioni, P Nisi; Splendiani, A; Pereira, J C; Olmo, E; Rens, W; Caputo Barucchi, V; Ferguson-Smith, M A

    2017-03-01

    Anoles are a clade of iguanian lizards that underwent an extensive radiation between 125 and 65 million years ago. Their karyotypes show wide variation in diploid number spanning from 26 (Anolis evermanni) to 44 (A. insolitus). This chromosomal variation involves their sex chromosomes, ranging from simple systems (XX/XY), with heterochromosomes represented by either micro- or macrochromosomes, to multiple systems (X1X1X2X2/X1X2Y). Here, for the first time, the homology relationships of sex chromosomes have been investigated in nine anole lizards at the whole chromosome level. Cross-species chromosome painting using sex chromosome paints from A. carolinensis, Ctenonotus pogus and Norops sagrei and gene mapping of X-linked genes demonstrated that the anole ancestral sex chromosome system constituted by microchromosomes is retained in all the species with the ancestral karyotype (2n = 36, 12 macro- and 24 microchromosomes). On the contrary, species with a derived karyotype, namely those belonging to genera Ctenonotus and Norops, show a series of rearrangements (fusions/fissions) involving autosomes/microchromosomes that led to the formation of their current sex chromosome systems. These results demonstrate that different autosomes were involved in translocations with sex chromosomes in closely related lineages of anole lizards and that several sequential microautosome/sex chromosome fusions lead to a remarkable increase in size of Norops sagrei sex chromosomes.

  7. Studies on metatherian sex chromosomes. XII. Sex-linked inheritance and probable paternal X-inactivation of alpha-galactosidase A in Australian marsupials.

    PubMed

    Cooper, D W; Woolley, P A; Maynes, G M; Sherman, F S; Poole, W E

    1983-01-01

    An investigation of genetic variation in the electrophoretic mobility of the enzyme alpha-galactosidase A (EC 3.2.1.22) has been carried out for 33 species of Australian metatherian (marsupial) mammals. The results are compatible with the enzyme being sex-linked in macropodids (kangaroos and wallabies) and probably in dasyurids (marsupial 'mice', etc.), as it is in eutherian (placental) mammals. The results also suggest that the mode of dosage compensation for this locus is the same as for other sex-linked loci in kangaroos, i.e. paternal X inactivation, rather than the random X inactivation system of eutherian mammals. The bearing of the enzyme mobility data on phylogenetic relationships among macropodid species is discussed.

  8. INDEPENDENT STRATUM FORMATION ON THE AVIAN SEX CHROMOSOMES REVEALS INTER-CHROMOSOMAL GENE CONVERSION AND PREDOMINANCE OF PURIFYING SELECTION ON THE W CHROMOSOME

    PubMed Central

    Wright, Alison E; Harrison, Peter W; Montgomery, Stephen H; Pointer, Marie A; Mank, Judith E

    2014-01-01

    We used a comparative approach spanning three species and 90 million years to study the evolutionary history of the avian sex chromosomes. Using whole transcriptomes, we assembled the largest cross-species dataset of W-linked coding content to date. Our results show that recombination suppression in large portions of the avian sex chromosomes has evolved independently, and that long-term sex chromosome divergence is consistent with repeated and independent inversions spreading progressively to restrict recombination. In contrast, over short-term periods we observe heterogeneous and locus-specific divergence. We also uncover four instances of gene conversion between both highly diverged and recently evolved gametologs, suggesting a complex mosaic of recombination suppression across the sex chromosomes. Lastly, evidence from 16 gametologs reveal that the W chromosome is evolving with a significant contribution of purifying selection, consistent with previous findings that W-linked genes play an important role in encoding sex-specific fitness. PMID:25066800

  9. Sex Chromosome Evolution, Heterochiasmy, and Physiological QTL in the Salmonid Brook Charr Salvelinus fontinalis

    PubMed Central

    Sutherland, Ben J.G.; Rico, Ciro; Audet, Céline; Bernatchez, Louis

    2017-01-01

    Whole-genome duplication (WGD) can have large impacts on genome evolution, and much remains unknown about these impacts. This includes the mechanisms of coping with a duplicated sex determination system and whether this has an impact on increasing the diversity of sex determination mechanisms. Other impacts include sexual conflict, where alleles having different optimums in each sex can result in sequestration of genes into nonrecombining sex chromosomes. Sex chromosome development itself may involve sex-specific recombination rate (i.e., heterochiasmy), which is also poorly understood. The family Salmonidae is a model system for these phenomena, having undergone autotetraploidization and subsequent rediploidization in most of the genome at the base of the lineage. The salmonid master sex determining gene is known, and many species have nonhomologous sex chromosomes, putatively due to transposition of this gene. In this study, we identify the sex chromosome of Brook Charr Salvelinus fontinalis and compare sex chromosome identities across the lineage (eight species and four genera). Although nonhomology is frequent, homologous sex chromosomes and other consistencies are present in distantly related species, indicating probable convergence on specific sex and neo-sex chromosomes. We also characterize strong heterochiasmy with 2.7-fold more crossovers in maternal than paternal haplotypes with paternal crossovers biased to chromosome ends. When considering only rediploidized chromosomes, the overall heterochiasmy trend remains, although with only 1.9-fold more recombination in the female than the male. Y chromosome crossovers are restricted to a single end of the chromosome, and this chromosome contains a large interspecific inversion, although its status between males and females remains unknown. Finally, we identify quantitative trait loci (QTL) for 21 unique growth, reproductive, and stress-related phenotypes to improve knowledge of the genetic architecture of these

  10. The Discovery of XY Sex Chromosomes in a Boa and Python.

    PubMed

    Gamble, Tony; Castoe, Todd A; Nielsen, Stuart V; Banks, Jaison L; Card, Daren C; Schield, Drew R; Schuett, Gordon W; Booth, Warren

    2017-07-24

    For over 50 years, biologists have accepted that all extant snakes share the same ZW sex chromosomes derived from a common ancestor [1-3], with different species exhibiting sex chromosomes at varying stages of differentiation. Accordingly, snakes have been a well-studied model for sex chromosome evolution in animals [1, 4]. A review of the literature, however, reveals no compelling support that boas and pythons possess ZW sex chromosomes [2, 5]. Furthermore, phylogenetic patterns of facultative parthenogenesis in snakes and a sex-linked color mutation in the ball python (Python regius) are best explained by boas and pythons possessing an XY sex chromosome system [6, 7]. Here we demonstrate that a boa (Boa imperator) and python (Python bivittatus) indeed possess XY sex chromosomes, based on the discovery of male-specific genetic markers in both species. We use these markers, along with transcriptomic and genomic data, to identify distinct sex chromosomes in boas and pythons, demonstrating that XY systems evolved independently in each lineage. This discovery highlights the dynamic evolution of vertebrate sex chromosomes and further enhances the value of snakes as a model for studying sex chromosome evolution. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

    PubMed

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

    2011-08-01

    The wolf fish Hoplias malabaricus includes well differentiated sex systems (XY and X(1)X(2)Y in karyomorphs B and D, respectively), a nascent XY pair (karyomorph C) and not recognized sex chromosomes (karyomorph A). We performed the evolutionary analysis of these sex chromosomes, using two X chromosome-specific probes derived by microdissection from the XY and X(1)X(2)Y sex systems. A putative-sex pair in karyomorph A was identified, from which the differentiated XY system was evolved, as well as the clearly evolutionary relationship between the nascent XY system and the origin of the multiple X(1)X(2)Y chromosomes. The lack of recognizable signals on the sex chromosomes after the reciprocal cross-FISH experiments highlighted that they evolved independently from non-homologous autosomal pairs. It is noteworthy that these distinct pathways occur inside the same nominal species, thus exposing the high plasticity of sex chromosome evolution in lower vertebrates. Possible mechanisms underlying this sex determination liability are also discussed.

  12. Coexistence of Y, W, and Z sex chromosomes in Xenopus tropicalis

    PubMed Central

    Roco, Álvaro S.; Olmstead, Allen W.; Degitz, Sigmund J.; Amano, Tosikazu; Zimmerman, Lyle B.; Bullejos, Mónica

    2015-01-01

    Homomorphic sex chromosomes and rapid turnover of sex-determining genes can complicate establishing the sex chromosome system operating in a given species. This difficulty exists in Xenopus tropicalis, an anuran quickly becoming a relevant model for genetic, genomic, biochemical, and ecotoxicological research. Despite the recent interest attracted by this species, little is known about its sex chromosome system. Direct evidence that females are the heterogametic sex, as in the related species Xenopus laevis, has yet to be presented. Furthermore, X. laevis’ sex-determining gene, DM-W, does not exist in X. tropicalis, and the sex chromosomes in the two species are not homologous. Here we identify X. tropicalis’ sex chromosome system by integrating data from (i) breeding sex-reversed individuals, (ii) gynogenesis, (iii) triploids, and (iv) crosses among several strains. Our results indicate that at least three different types of sex chromosomes exist: Y, W, and Z, observed in YZ, YW, and ZZ males and in ZW and WW females. Because some combinations of parental sex chromosomes produce unisex offspring and other distorted sex ratios, understanding the sex-determination systems in X. tropicalis is critical for developing this flexible animal model for genetics and ecotoxicology. PMID:26216983

  13. Coexistence of Y, W, and Z sex chromosomes in Xenopus tropicalis.

    PubMed

    Roco, Álvaro S; Olmstead, Allen W; Degitz, Sigmund J; Amano, Tosikazu; Zimmerman, Lyle B; Bullejos, Mónica

    2015-08-25

    Homomorphic sex chromosomes and rapid turnover of sex-determining genes can complicate establishing the sex chromosome system operating in a given species. This difficulty exists in Xenopus tropicalis, an anuran quickly becoming a relevant model for genetic, genomic, biochemical, and ecotoxicological research. Despite the recent interest attracted by this species, little is known about its sex chromosome system. Direct evidence that females are the heterogametic sex, as in the related species Xenopus laevis, has yet to be presented. Furthermore, X. laevis' sex-determining gene, DM-W, does not exist in X. tropicalis, and the sex chromosomes in the two species are not homologous. Here we identify X. tropicalis' sex chromosome system by integrating data from (i) breeding sex-reversed individuals, (ii) gynogenesis, (iii) triploids, and (iv) crosses among several strains. Our results indicate that at least three different types of sex chromosomes exist: Y, W, and Z, observed in YZ, YW, and ZZ males and in ZW and WW females. Because some combinations of parental sex chromosomes produce unisex offspring and other distorted sex ratios, understanding the sex-determination systems in X. tropicalis is critical for developing this flexible animal model for genetics and ecotoxicology.

  14. B Chromosomes Have a Functional Effect on Female Sex Determination in Lake Victoria Cichlid Fishes

    PubMed Central

    Yoshida, Kohta; Terai, Yohey; Mizoiri, Shinji; Aibara, Mitsuto; Nishihara, Hidenori; Watanabe, Masakatsu; Kuroiwa, Asato; Hirai, Hirohisa; Hirai, Yuriko; Matsuda, Yoichi; Okada, Norihiro

    2011-01-01

    The endemic cichlid fishes in Lake Victoria are a model system for speciation through adaptive radiation. Although the evolution of the sex-determination system may also play a role in speciation, little is known about the sex-determination system of Lake Victoria cichlids. To understand the evolution of the sex-determination system in these fish, we performed cytogenetic analysis in 11 cichlid species from Lake Victoria. B chromosomes, which are present in addition to standard chromosomes, were found at a high prevalence rate (85%) in these cichlids. In one species, B chromosomes were female-specific. Cross-breeding using females with and without the B chromosomes demonstrated that the presence of the B chromosomes leads to a female-biased sex ratio in this species. Although B chromosomes were believed to be selfish genetic elements with little effect on phenotype and to lack protein-coding genes, the present study provides evidence that B chromosomes have a functional effect on female sex determination. FISH analysis using a BAC clone containing B chromosome DNA suggested that the B chromosomes are derived from sex chromosomes. Determination of the nucleotide sequences of this clone (104.5 kb) revealed the presence of several protein-coding genes in the B chromosome, suggesting that B chromosomes have the potential to contain functional genes. Because some sex chromosomes in amphibians and arthropods are thought to be derived from B chromosomes, the B chromosomes in Lake Victoria cichlids may represent an evolutionary transition toward the generation of sex chromosomes. PMID:21876673

  15. B chromosomes have a functional effect on female sex determination in Lake Victoria cichlid fishes.

    PubMed

    Yoshida, Kohta; Terai, Yohey; Mizoiri, Shinji; Aibara, Mitsuto; Nishihara, Hidenori; Watanabe, Masakatsu; Kuroiwa, Asato; Hirai, Hirohisa; Hirai, Yuriko; Matsuda, Yoichi; Okada, Norihiro

    2011-08-01

    The endemic cichlid fishes in Lake Victoria are a model system for speciation through adaptive radiation. Although the evolution of the sex-determination system may also play a role in speciation, little is known about the sex-determination system of Lake Victoria cichlids. To understand the evolution of the sex-determination system in these fish, we performed cytogenetic analysis in 11 cichlid species from Lake Victoria. B chromosomes, which are present in addition to standard chromosomes, were found at a high prevalence rate (85%) in these cichlids. In one species, B chromosomes were female-specific. Cross-breeding using females with and without the B chromosomes demonstrated that the presence of the B chromosomes leads to a female-biased sex ratio in this species. Although B chromosomes were believed to be selfish genetic elements with little effect on phenotype and to lack protein-coding genes, the present study provides evidence that B chromosomes have a functional effect on female sex determination. FISH analysis using a BAC clone containing B chromosome DNA suggested that the B chromosomes are derived from sex chromosomes. Determination of the nucleotide sequences of this clone (104.5 kb) revealed the presence of several protein-coding genes in the B chromosome, suggesting that B chromosomes have the potential to contain functional genes. Because some sex chromosomes in amphibians and arthropods are thought to be derived from B chromosomes, the B chromosomes in Lake Victoria cichlids may represent an evolutionary transition toward the generation of sex chromosomes.

  16. Sex chromosome complement involvement in angiotensin receptor sexual dimorphism.

    PubMed

    Dadam, Florencia M; Cisternas, Carla D; Macchione, Ana F; Godino, Andrea; Antunes-Rodrigues, José; Cambiasso, María J; Vivas, Laura M; Caeiro, Ximena E

    2017-02-27

    This study aimed to define whether sex chromosome complement (SCC) may differentially modulate sex differences in relative gene expression of basal Agtr1a, Agtr2, and Mas1 receptors at fore/hindbrain nuclei and at medulla/cortical kidney. Samples were collected from gonadectomized male (XX and XY) and female (XX and XY) mice of the "four core genotypes" model. At brain level, a SCC effect at the area postrema was demonstrated. An increase in mRNA level of Agtr1a and Agtr1a/Agtr2 ratio in XY-SCC mice was associated with a decrease in Mas1 compared to XX-SCC mice. In the renal cortex, a SCC effect for Agtr2 and Mas1 was observed. Regardless of sex (male or female), XX-SCC mice expressed higher levels of mRNA Agtr2 and Mas1 than XY-SCC mice {F(1,12) = 6,126,p < 0.05; F(1,21) = 5,143,p < 0.05}. Furthermore, XX-female mice showed a significant increase in Mas1 expression compared to XY-female mice. These results reveal a SCC modulatory effect at central and kidney level on angiotensin receptor expression, with an enhancement of the vasodilatory arm in XX-mice and an increase in the vasoconstriction arm in XY-mice, which may underlie sex differences in the regulation of arterial pressure.

  17. Sex-Linked Chromosome Heterozygosity in Males of Tityus confluens (Buthidae): A Clue about the Presence of Sex Chromosomes in Scorpions

    PubMed Central

    Adilardi, Renzo Sebastián; Ojanguren-Affilastro, Andrés Alejandro; Mola, Liliana María

    2016-01-01

    Scorpions of the genus Tityus show holokinetic chromosomes, achiasmatic male meiosis and an absence of heteromorphic sex chromosomes, like all Buthidae. In this work, we analysed the meiotic behaviour and chromosome rearrangements of a population of the scorpion Tityus confluens, characterising the cytotypes of males, females and embryos with different cytogenetic techniques. This revealed that all the females were structural homozygotes, while all the males were structural heterozygotes for different chromosome rearrangements. Four different cytotypes were described in males, which differed in chromosome number (2n = 5 and 2n = 6) and meiotic multivalent configurations (chains of four, five and six chromosomes). Based on a detailed mitotic and meiotic analysis, we propose a sequence of chromosome rearrangements that could give rise to each cytotype and in which fusions have played a major role. Based on the comparison of males, females and a brood of embryos, we also propose that the presence of multivalents in males and homologous pairs in females could be associated with the presence of cryptic sex chromosomes, with the male being the heterogametic sex. We propose that the ancestral karyotype of this species could have had homomorphic XY/XX (male/female) sex chromosomes and a fusion could have occurred between the Y chromosome and an autosome. PMID:27783630

  18. Sex-Linked Chromosome Heterozygosity in Males of Tityus confluens (Buthidae): A Clue about the Presence of Sex Chromosomes in Scorpions.

    PubMed

    Adilardi, Renzo Sebastián; Ojanguren-Affilastro, Andrés Alejandro; Mola, Liliana María

    2016-01-01

    Scorpions of the genus Tityus show holokinetic chromosomes, achiasmatic male meiosis and an absence of heteromorphic sex chromosomes, like all Buthidae. In this work, we analysed the meiotic behaviour and chromosome rearrangements of a population of the scorpion Tityus confluens, characterising the cytotypes of males, females and embryos with different cytogenetic techniques. This revealed that all the females were structural homozygotes, while all the males were structural heterozygotes for different chromosome rearrangements. Four different cytotypes were described in males, which differed in chromosome number (2n = 5 and 2n = 6) and meiotic multivalent configurations (chains of four, five and six chromosomes). Based on a detailed mitotic and meiotic analysis, we propose a sequence of chromosome rearrangements that could give rise to each cytotype and in which fusions have played a major role. Based on the comparison of males, females and a brood of embryos, we also propose that the presence of multivalents in males and homologous pairs in females could be associated with the presence of cryptic sex chromosomes, with the male being the heterogametic sex. We propose that the ancestral karyotype of this species could have had homomorphic XY/XX (male/female) sex chromosomes and a fusion could have occurred between the Y chromosome and an autosome.

  19. LEOPARD syndrome with partly normal skin and sex chromosome mosaicism.

    PubMed

    Writzl, Karin; Hoovers, Jan; Sistermans, Erik A; Hennekam, Raoul C M

    2007-11-01

    We report on a family with LEOPARD syndrome which was molecularly proven (p.Thr468Met in PTPN11) in a father and his adult son. The father had multiple lentigines dispersed equally over his body; the son was similarly affected except for the left part of thorax, back and left arm, which were completely devoid of lentigines and only showed a few nevi. In addition, the son was found to have a mosaic karyotype, 47,XYY/46,XY, in lymphocytes. Skin biopsies from the pigmented and unpigmented forearm showed that mainly a 47,XYY karyotype was present in the pigmented skin and mainly a 46,XY karyotype in the unpigmented skin. In both fibroblast cultures the PTPN11 mutation was present, and no additional mutation could be detected. We discuss the various possible explanations for this phenotype, which include the possibility of coincidence; revertant mosaicism; silencing of a second PTPN11 mutation; gene(s) located on a sex chromosome influencing the phenotype; and epigenetic influences. We favor that the co-occurrence of a sex chromosome mosaicism and mosaicism for skin symptoms in a single patient with LEOPARD syndrome is coincidence, but that mosaicism for LEOPARD skin symptoms in itself may well be more frequent and needs additional studies. Each of the above-hypothesized mechanisms may then remain possible.

  20. Empirical evidence for large X-effects in animals with undifferentiated sex chromosomes

    PubMed Central

    Dufresnes, Christophe; Majtyka, Tomasz; Baird, Stuart J. E.; Gerchen, Jörn F.; Borzée, Amaël; Savary, Romain; Ogielska, Maria; Perrin, Nicolas; Stöck, Matthias

    2016-01-01

    Reproductive isolation is crucial for the process of speciation to progress. Sex chromosomes have been assigned a key role in driving reproductive isolation but empirical evidence from natural population processes has been restricted to organisms with degenerated sex chromosomes such as mammals and birds. Here we report restricted introgression at sex-linked compared to autosomal markers in a hybrid zone between two incipient species of European tree frog, Hyla arborea and H. orientalis, whose homologous X and Y sex chromosomes are undifferentiated. This large X-effect cannot result from the dominance or faster-X aspects of Haldane’s rule, which are specific to degenerated sex chromosomes, but rather supports a role for faster-heterogametic-sex or faster-male evolutionary processes. Our data suggest a prominent contribution of undifferentiated sex chromosomes to speciation. PMID:26868373

  1. Empirical evidence for large X-effects in animals with undifferentiated sex chromosomes.

    PubMed

    Dufresnes, Christophe; Majtyka, Tomasz; Baird, Stuart J E; Gerchen, Jörn F; Borzée, Amaël; Savary, Romain; Ogielska, Maria; Perrin, Nicolas; Stöck, Matthias

    2016-02-12

    Reproductive isolation is crucial for the process of speciation to progress. Sex chromosomes have been assigned a key role in driving reproductive isolation but empirical evidence from natural population processes has been restricted to organisms with degenerated sex chromosomes such as mammals and birds. Here we report restricted introgression at sex-linked compared to autosomal markers in a hybrid zone between two incipient species of European tree frog, Hyla arborea and H. orientalis, whose homologous X and Y sex chromosomes are undifferentiated. This large X-effect cannot result from the dominance or faster-X aspects of Haldane's rule, which are specific to degenerated sex chromosomes, but rather supports a role for faster-heterogametic-sex or faster-male evolutionary processes. Our data suggest a prominent contribution of undifferentiated sex chromosomes to speciation.

  2. Distribution of the sex chromosome during mouse spermatogenesis in testis tissue sections

    PubMed Central

    OTAKA, Kosuke; HIRADATE, Yuuki; KOBAYASHI, Norio; SHIRAKATA, Yoshiki; TANEMURA, Kentaro

    2015-01-01

    During mammalian spermatogenesis, spermatogenic cells undergo mitotic division and are subsequently divided into haploid spermatids by meiotic division, but the dynamics of sex chromosomes during spermatogenesis are unclear in vivo. To gain insight into the distribution of sex chromosomes in the testis, we examined the localization of sex chromosomes before and after meiosis in mouse testis sections. Here, we developed a method of fluorescence in situ hybridization (FISH) using specific probes for the X and Y chromosomes to obtain their positional information in histological testis sections. FISH analysis revealed the sex chromosomal position during spermatogenesis in each stage of seminiferous epithelia and in each spermatogenic cell. In the spermatogonia and leptotene spermatocytes, sex chromosomes were distantly positioned in the cell. In the zygotene and pachytene spermatocytes at prophase I, X and Y chromosomes had a random distribution. After meiosis, the X and Y spermatids were random in every seminiferous epithelium. We also detected aneuploidy of sex chromosomes in spermatogenic cells using our developed FISH analysis. Our results provide further insight into the distribution of sex chromosomes during spermatogenesis, which could help to elucidate a specific difference between X and Y spermatids and sex chromosome-specific behavior. PMID:26073979

  3. Sex differences in juvenile mouse social behavior are influenced by sex chromosomes and social context

    PubMed Central

    Cox, Kimberly H.; Rissman, Emilie F.

    2011-01-01

    Play behavior in juvenile primates, rats, and other species is sexually dimorphic, with males demonstrating more play than females. In mice, sex differences in juvenile play have only been examined in out-bred CD-1 mice. In this strain, contrary to other animals, male mice display less play soliciting than females. Using an established same-sex dyadic interaction test, we examined play in inbred C57BL/6J (B6) 21 day-old mice. When paired with non-siblings, males tended to be more social than females, spending more time exploring the test cage. Females displayed significantly more anogenital sniffing and solicited play more frequently than did males. To determine if the origin of the sex difference was sex chromosome genes or gonadal sex, next we used the four core genotype (FCG) mouse. We found significant interactions between gonadal sex and genotype for several behaviors. Finally, we asked if sibling pairs (as compared to non-siblings) would display qualitative or quantitatively different behavior. In fact, XX females paired with a sibling were more social and less exploratory or investigative, while XY males exhibited less investigative and play soliciting behaviors in tests with siblings. Many neurobehavioral disorders, like autism spectrum disorder (ASD), are sexually dimorphic in incidence and patients interact less than normal with other children. Our results suggest that sex chromosome genes interact with gonadal hormones to shape the development of juvenile social behavior, and that social context can drastically alter sex differences. These data may have relevance for understanding the etiology of sexually dimorphic disorders such as ASD. PMID:21414140

  4. Searching for sex-reversals to explain population demography and the evolution of sex chromosomes.

    PubMed

    Wedekind, Claus

    2010-05-01

    Sex determination can be purely genetic (as in mammals and birds), purely environmental (as in many reptiles), or genetic but reversible by environmental factors during a sensitive period in life, as in many fish and amphibians (Wallace et al. 1999; Baroiller et al. 2009a; Stelkens & Wedekind 2010). Such environmental sex reversal (ESR) can be induced, for example, by temperature changes or by exposure to hormone-active substances. ESR has long been recognized as a means to produce more profitable single-sex cultures in fish farms (Cnaani & Levavi-Sivan 2009), but we know very little about its prevalence in the wild. Obviously, induced feminization or masculinization may immediately distort population sex ratios, and distorted sex ratios are indeed reported from some amphibian and fish populations (Olsen et al. 2006; Alho et al. 2008; Brykov et al. 2008). However, sex ratios can also be skewed by, for example, segregation distorters or sex-specific mortality. Demonstrating ESR in the wild therefore requires the identification of sex-linked genetic markers (in the absence of heteromorphic sex chromosomes) followed by comparison of genotypes and phenotypes, or experimental crosses with individuals who seem sex reversed, followed by sexing of offspring after rearing under non-ESR conditions and at low mortality. In this issue, Alho et al. (2010) investigate the role of ESR in the common frog (Rana temporaria) and a population that has a distorted adult sex ratio. They developed new sex-linked microsatellite markers and tested wild-caught male and female adults for potential mismatches between phenotype and genotype. They found a significant proportion of phenotypic males with a female genotype. This suggests environmental masculinization, here with a prevalence of 9%. The authors then tested whether XX males naturally reproduce with XX females. They collected egg clutches and found that some had indeed a primary sex ratio of 100% daughters. Other clutches seemed to

  5. Incidental Prenatal Diagnosis of Sex Chromosome Aneuploidies: Health, Behavior, and Fertility

    PubMed Central

    Pieters, J. J. P. M.; Kooper, A. J. A.; van Kessel, A. Geurts; Braat, D. D. M.; Smits, A. P. T.

    2011-01-01

    Objective. To assess the diagnostic relevance of incidental prenatal findings of sex chromosome aneuploidies. Methods. We searched with medical subject headings (MeSHs) and keywords in Medline and the Cochrane Library and systematically screened publications on postnatally diagnosed sex chromosomal aneuploidies from 2006 to 2011 as well as publications on incidentally prenatally diagnosed sex chromosomal aneuploidies from 1980 to 2011. Results. Postnatally diagnosed sex chromosomal aneuploidies demonstrated three clinical relevant domains of abnormality: physical (22–100%), behavior (0–56%), and reproductive health (47–100%), while incidentally prenatally diagnosed sex chromosomal aneuploidies demonstrated, respectively, 0–33%, 0–40%, and 0–36%. Conclusion. In the literature incidental prenatal diagnosis of sex chromosomal aneuploidies is associated with normal to mildly affected phenotypes. This contrasts sharply with those of postnatally diagnosed sex chromosomal aneuploidies and highlights the importance of this ascertainment bias towards the prognostic value of diagnosis of fetal sex chromosomal aneuploidies. This observation should be taken into account, especially when considering excluding the sex chromosomes in invasive prenatal testing using Rapid Aneuploidy Detection. PMID:22191050

  6. Evolution of the Sex Chromosomes in Beetles. I. The Loss of the Y Chromosome.

    PubMed

    Dutrillaux, Anne-Marie; Dutrillaux, Bernard

    2017-01-01

    In the males of Coleoptera, the most frequent sex chromosome constitution is XY. At metaphase I of meiosis, the X and Y are linked by nucleolar proteins, forming the so-called parachute bivalent (Xyp), which is assumed to allow the non-synapsed X and Y to segregate correctly at anaphase I. However, X0 males are not exceptional, and we explored the relationships between the X and nucleolar proteins in the absence of the Y chromosome in 6 species belonging to different families/subfamilies. Using C-banding and silver staining, we show that nucleolar proteins always remain in contact with the X until anaphase I. These proteins are generally more abundant than in the Xyp bivalent, may remain associated with the NOR during diakinesis, and frequently link the X to 1 or 2 autosomal bivalents, which seem to play the same role as the Y. This role may also be played by B chromosomes, which appear to be more frequent in X0 than in XY males. In conclusion, following Y chromosome loss, various strategies using nucleolar proteins have been developed to facilitate the migration of the unique X at meiotic anaphase I. © 2017 S. Karger AG, Basel.

  7. Interchromosomal Duplications on the Bactrocera oleae Y Chromosome Imply a Distinct Evolutionary Origin of the Sex Chromosomes Compared to Drosophila

    PubMed Central

    Gabrieli, Paolo; Gomulski, Ludvik M.; Bonomi, Angelica; Siciliano, Paolo; Scolari, Francesca; Franz, Gerald; Jessup, Andrew; Malacrida, Anna R.; Gasperi, Giuliano

    2011-01-01

    Background Diptera have an extraordinary variety of sex determination mechanisms, and Drosophila melanogaster is the paradigm for this group. However, the Drosophila sex determination pathway is only partially conserved and the family Tephritidae affords an interesting example. The tephritid Y chromosome is postulated to be necessary to determine male development. Characterization of Y sequences, apart from elucidating the nature of the male determining factor, is also important to understand the evolutionary history of sex chromosomes within the Tephritidae. We studied the Y sequences from the olive fly, Bactrocera oleae. Its Y chromosome is minute and highly heterochromatic, and displays high heteromorphism with the X chromosome. Methodology/Principal Findings A combined Representational Difference Analysis (RDA) and fluorescence in-situ hybridization (FISH) approach was used to investigate the Y chromosome to derive information on its sequence content. The Y chromosome is strewn with repetitive DNA sequences, the majority of which are also interdispersed in the pericentromeric regions of the autosomes. The Y chromosome appears to have accumulated small and large repetitive interchromosomal duplications. The large interchromosomal duplications harbour an importin-4-like gene fragment. Apart from these importin-4-like sequences, the other Y repetitive sequences are not shared with the X chromosome, suggesting molecular differentiation of these two chromosomes. Moreover, as the identified Y sequences were not detected on the Y chromosomes of closely related tephritids, we can infer divergence in the repetitive nature of their sequence contents. Conclusions/Significance The identification of Y-linked sequences may tell us much about the repetitive nature, the origin and the evolution of Y chromosomes. We hypothesize how these repetitive sequences accumulated and were maintained on the Y chromosome during its evolutionary history. Our data reinforce the idea that the

  8. Interchromosomal duplications on the Bactrocera oleae Y chromosome imply a distinct evolutionary origin of the sex chromosomes compared to Drosophila.

    PubMed

    Gabrieli, Paolo; Gomulski, Ludvik M; Bonomi, Angelica; Siciliano, Paolo; Scolari, Francesca; Franz, Gerald; Jessup, Andrew; Malacrida, Anna R; Gasperi, Giuliano

    2011-03-07

    Diptera have an extraordinary variety of sex determination mechanisms, and Drosophila melanogaster is the paradigm for this group. However, the Drosophila sex determination pathway is only partially conserved and the family Tephritidae affords an interesting example. The tephritid Y chromosome is postulated to be necessary to determine male development. Characterization of Y sequences, apart from elucidating the nature of the male determining factor, is also important to understand the evolutionary history of sex chromosomes within the Tephritidae. We studied the Y sequences from the olive fly, Bactrocera oleae. Its Y chromosome is minute and highly heterochromatic, and displays high heteromorphism with the X chromosome. A combined Representational Difference Analysis (RDA) and fluorescence in-situ hybridization (FISH) approach was used to investigate the Y chromosome to derive information on its sequence content. The Y chromosome is strewn with repetitive DNA sequences, the majority of which are also interdispersed in the pericentromeric regions of the autosomes. The Y chromosome appears to have accumulated small and large repetitive interchromosomal duplications. The large interchromosomal duplications harbour an importin-4-like gene fragment. Apart from these importin-4-like sequences, the other Y repetitive sequences are not shared with the X chromosome, suggesting molecular differentiation of these two chromosomes. Moreover, as the identified Y sequences were not detected on the Y chromosomes of closely related tephritids, we can infer divergence in the repetitive nature of their sequence contents. The identification of Y-linked sequences may tell us much about the repetitive nature, the origin and the evolution of Y chromosomes. We hypothesize how these repetitive sequences accumulated and were maintained on the Y chromosome during its evolutionary history. Our data reinforce the idea that the sex chromosomes of the Tephritidae may have distinct evolutionary

  9. Sex Chromosome Turnover Contributes to Genomic Divergence between Incipient Stickleback Species

    PubMed Central

    Yoshida, Kohta; Makino, Takashi; Yamaguchi, Katsushi; Shigenobu, Shuji; Hasebe, Mitsuyasu; Kawata, Masakado; Kume, Manabu; Mori, Seiichi; Peichel, Catherine L.; Toyoda, Atsushi; Fujiyama, Asao; Kitano, Jun

    2014-01-01

    Sex chromosomes turn over rapidly in some taxonomic groups, where closely related species have different sex chromosomes. Although there are many examples of sex chromosome turnover, we know little about the functional roles of sex chromosome turnover in phenotypic diversification and genomic evolution. The sympatric pair of Japanese threespine stickleback (Gasterosteus aculeatus) provides an excellent system to address these questions: the Japan Sea species has a neo-sex chromosome system resulting from a fusion between an ancestral Y chromosome and an autosome, while the sympatric Pacific Ocean species has a simple XY sex chromosome system. Furthermore, previous quantitative trait locus (QTL) mapping demonstrated that the Japan Sea neo-X chromosome contributes to phenotypic divergence and reproductive isolation between these sympatric species. To investigate the genomic basis for the accumulation of genes important for speciation on the neo-X chromosome, we conducted whole genome sequencing of males and females of both the Japan Sea and the Pacific Ocean species. No substantial degeneration has yet occurred on the neo-Y chromosome, but the nucleotide sequence of the neo-X and the neo-Y has started to diverge, particularly at regions near the fusion. The neo-sex chromosomes also harbor an excess of genes with sex-biased expression. Furthermore, genes on the neo-X chromosome showed higher non-synonymous substitution rates than autosomal genes in the Japan Sea lineage. Genomic regions of higher sequence divergence between species, genes with divergent expression between species, and QTL for inter-species phenotypic differences were found not only at the regions near the fusion site, but also at other regions along the neo-X chromosome. Neo-sex chromosomes can therefore accumulate substitutions causing species differences even in the absence of substantial neo-Y degeneration. PMID:24625862

  10. Progressive Recombination Suppression and Differentiation in Recently Evolved Neo-sex Chromosomes

    PubMed Central

    Natri, Heini M.; Shikano, Takahito; Merilä, Juha

    2013-01-01

    Recombination suppression leads to the structural and functional differentiation of sex chromosomes and is thus a crucial step in the process of sex chromosome evolution. Despite extensive theoretical work, the exact processes and mechanisms of recombination suppression and differentiation are not well understood. In threespine sticklebacks (Gasterosteus aculeatus), a different sex chromosome system has recently evolved by a fusion between the Y chromosome and an autosome in the Japan Sea lineage, which diverged from the ancestor of other lineages approximately 2 Ma. We investigated the evolutionary dynamics and differentiation processes of sex chromosomes based on comparative analyses of these divergent lineages using 63 microsatellite loci. Both chromosome-wide differentiation patterns and phylogenetic inferences with X and Y alleles indicated that the ancestral sex chromosomes were extensively differentiated before the divergence of these lineages. In contrast, genetic differentiation appeared to have proceeded only in a small region of the neo-sex chromosomes. The recombination maps constructed for the Japan Sea lineage indicated that recombination has been suppressed or reduced over a large region spanning the ancestral and neo-sex chromosomes. Chromosomal regions exhibiting genetic differentiation and suppressed or reduced recombination were detected continuously and sequentially in the neo-sex chromosomes, suggesting that differentiation has gradually spread from the fusion point following the extension of recombination suppression. Our study illustrates an ongoing process of sex chromosome differentiation, providing empirical support for the theoretical model postulating that recombination suppression and differentiation proceed in a gradual manner in the very early stage of sex chromosome evolution. PMID:23436913

  11. The Evolutionary Tempo of Sex Chromosome Degradation in Carica papaya.

    PubMed

    Wu, Meng; Moore, Richard C

    2015-06-01

    Genes on non-recombining heterogametic sex chromosomes may degrade over time through the irreversible accumulation of deleterious mutations. In papaya, the non-recombining male-specific region of the Y (MSY) consists of two evolutionary strata corresponding to chromosomal inversions occurring approximately 7.0 and 1.9 MYA. The step-wise recombination suppression between the papaya X and Y allows for a temporal examination of the degeneration progress of the young Y chromosome. Comparative evolutionary analyses of 55 X/Y gene pairs showed that Y-linked genes have more unfavorable substitutions than X-linked genes. However, this asymmetric evolutionary pattern is confined to the oldest stratum, and is only observed when recently evolved pseudogenes are included in the analysis, indicating a slow degeneration tempo of the papaya Y chromosome. Population genetic analyses of coding sequence variation of six Y-linked focal loci in the oldest evolutionary stratum detected an excess of nonsynonymous polymorphism and reduced codon bias relative to autosomal loci. However, this pattern was also observed for corresponding X-linked loci. Both the MSY and its corresponding X-specific region are pericentromeric where recombination has been shown to be greatly reduced. Like the MSY region, overall selective efficacy on the X-specific region may be reduced due to the interference of selective forces between highly linked loci, or the Hill-Robertson effect, that is accentuated in regions of low or suppressed recombination. Thus, a pattern of gene decay on the X-specific region may be explained by relaxed purifying selection and widespread genetic hitchhiking due to its pericentromeric location.

  12. Sex determination in Madagascar geckos of the genus Paroedura (Squamata: Gekkonidae): are differentiated sex chromosomes indeed so evolutionary stable?

    PubMed

    Koubová, Martina; Johnson Pokorná, Martina; Rovatsos, Michail; Farkačová, Klára; Altmanová, Marie; Kratochvíl, Lukáš

    2014-12-01

    Among amniote vertebrates, geckos represent a clade with exceptional variability in sex determination; however, only a minority of species of this highly diverse group has been studied in this respect. Here, we describe for the first time a female heterogamety in the genus Paroedura, the group radiated in Madagascar and adjacent islands. We identified homomorphic ZZ/ZW sex chromosomes with a highly heterochromatic W chromosome in Paroedura masobe, Paroedura oviceps, Paroedura karstophila, Paroedura stumpffi, and Paroedura lohatsara. Comparative genomic hybridization (CGH) revealed that female-specific sequences are greatly amplified in the W chromosome of P. lohatsara and that P. gracilis seems to possess a derived system of multiple sex chromosomes. Contrastingly, neither CGH nor heterochromatin visualization revealed differentiated sex chromosomes in the members of the Paroedura picta-Paroedura bastardi-Paroedura ibityensis clade, which is phylogenetically nested within lineages with a heterochromatic W chromosome. As a sex ratio consistent with genotypic sex determination has been reported in P. picta, it appears that the members of the P. picta-P. bastardi-P. ibityensis clade possess homomorphic, poorly differentiated sex chromosomes and may represent a rare example of evolutionary loss of highly differentiated sex chromosomes. Fluorescent in situ hybridization (FISH) with a telomeric probe revealed a telomere-typical pattern in all species and an accumulation of telomeric sequences in the centromeric region of autosomes in P. stumpffi and P. bastardi. Our study adds important information for the greater understanding of the variability and evolution of sex determination in geckos and demonstrates how the geckos of the genus Paroedura provide an interesting model for studying the evolution of the sex chromosomes.

  13. Double-strand break repair on sex chromosomes: challenges during male meiotic prophase

    PubMed Central

    Lu, Lin-Yu; Yu, Xiaochun

    2015-01-01

    During meiotic prophase, DNA double-strand break (DSB) repair-mediated homologous recombination (HR) occurs for exchange of genetic information between homologous chromosomes. Unlike autosomes or female sex chromosomes, human male sex chromosomes X and Y share little homology. Although DSBs are generated throughout male sex chromosomes, homologous recombination does not occur for most regions and DSB repair process is significantly prolonged. As a result, male sex chromosomes are coated with many DNA damage response proteins and form a unique chromatin structure known as the XY body. Interestingly, associated with the prolonged DSB repair, transcription is repressed in the XY body but not in autosomes, a phenomenon known as meiotic sex chromosome inactivation (MSCI), which is critical for male meiosis. Here using mice as model organisms, we briefly summarize recent progress on DSB repair in meiotic prophase and focus on the mechanism and function of DNA damage response in the XY body. PMID:25565522

  14. Double-strand break repair on sex chromosomes: challenges during male meiotic prophase.

    PubMed

    Lu, Lin-Yu; Yu, Xiaochun

    2015-01-01

    During meiotic prophase, DNA double-strand break (DSB) repair-mediated homologous recombination (HR) occurs for exchange of genetic information between homologous chromosomes. Unlike autosomes or female sex chromosomes, human male sex chromosomes X and Y share little homology. Although DSBs are generated throughout male sex chromosomes, homologous recombination does not occur for most regions and DSB repair process is significantly prolonged. As a result, male sex chromosomes are coated with many DNA damage response proteins and form a unique chromatin structure known as the XY body. Interestingly, associated with the prolonged DSB repair, transcription is repressed in the XY body but not in autosomes, a phenomenon known as meiotic sex chromosome inactivation (MSCI), which is critical for male meiosis. Here using mice as model organisms, we briefly summarize recent progress on DSB repair in meiotic prophase and focus on the mechanism and function of DNA damage response in the XY body.

  15. Comparative mapping reveals autosomal origin of sex chromosome in octoploid Fragaria virginiana.

    PubMed

    Spigler, Rachel B; Lewers, Kim S; Johnson, Anna L; Ashman, Tia-Lynn

    2010-01-01

    Recent evolution of separate sexes in flowering plants provides unparalleled opportunities for understanding the early stages of sex chromosome evolution, including their origin from autosomes. Moreover, the transition from combined to separate sexes can be associated with speciation via polyploidization in angiosperms, suggesting that genome doubling/merger may facilitate sterility mutations required for sex chromosome formation. To gain insight into the origin of sex chromosomes in a polyploid plant, we doubled the simple sequence repeat (SSR) density and increased genome coverage in a genetic map of octoploid Fragaria virginiana, a species purported to have a "proto-sex" chromosome, where limited recombination occurs between 2 linked "loci" carrying the male- and female-sterility mutations. Incorporation of almost 3 times the number of SSR markers into the current map facilitated complete characterization of the F. virginiana proto-sex chromosome, revealing its largely autosomal nature and the location of the sex-determining region toward the distal end. Furthermore, extensive synteny between our genetic map and a map involving diploid hermaphroditic congeners allowed assignment of linkage groups to homeologous groups, identification of the proto-sex chromosome's autosomal homoeolog, and detection of a putative rearrangement near the sex-determining region. Fine mapping and additional comparative work will shed light on the intriguing possibility that rearrangements during polyploidization were involved in the evolution of sex chromosomes in Fragaria.

  16. Genome-Wide Gene Expression Effects of Sex Chromosome Imprinting in Drosophila

    PubMed Central

    Lemos, Bernardo; Branco, Alan T.; Jiang, Pan-Pan; Hartl, Daniel L.; Meiklejohn, Colin D.

    2013-01-01

    Imprinting is well-documented in both plant and animal species. In Drosophila, the Y chromosome is differently modified when transmitted through the male and female germlines. Here, we report genome-wide gene expression effects resulting from reversed parent-of-origin of the X and Y chromosomes. We found that hundreds of genes are differentially expressed between adult male Drosophila melanogaster that differ in the maternal and paternal origin of the sex chromosomes. Many of the differentially regulated genes are expressed specifically in testis and midgut cells, suggesting that sex chromosome imprinting might globally impact gene expression in these tissues. In contrast, we observed much fewer Y-linked parent-of-origin effects on genome-wide gene expression in females carrying a Y chromosome, indicating that gene expression in females is less sensitive to sex chromosome parent-of-origin. Genes whose expression differs between females inheriting a maternal or paternal Y chromosome also show sex chromosome parent-of-origin effects in males, but the direction of the effects on gene expression (overexpression or underexpression) differ between the sexes. We suggest that passage of sex chromosome chromatin through male meiosis may be required for wild-type function in F1 progeny, whereas disruption of Y-chromosome function through passage in the female germline likely arises because the chromosome is not adapted to the female germline environment. PMID:24318925

  17. Convergent recombination suppression suggests role of sexual selection in guppy sex chromosome formation

    PubMed Central

    Wright, Alison E.; Darolti, Iulia; Bloch, Natasha I.; Oostra, Vicencio; Sandkam, Ben; Buechel, Severine D.; Kolm, Niclas; Breden, Felix; Vicoso, Beatriz; Mank, Judith E.

    2017-01-01

    Sex chromosomes evolve once recombination is halted between a homologous pair of chromosomes. The dominant model of sex chromosome evolution posits that recombination is suppressed between emerging X and Y chromosomes in order to resolve sexual conflict. Here we test this model using whole genome and transcriptome resequencing data in the guppy, a model for sexual selection with many Y-linked colour traits. We show that although the nascent Y chromosome encompasses nearly half of the linkage group, there has been no perceptible degradation of Y chromosome gene content or activity. Using replicate wild populations with differing levels of sexually antagonistic selection for colour, we also show that sexual selection leads to greater expansion of the non-recombining region and increased Y chromosome divergence. These results provide empirical support for longstanding models of sex chromosome catalysis, and suggest an important role for sexual selection and sexual conflict in genome evolution. PMID:28139647

  18. Back to the roots: segregation of univalent sex chromosomes in meiosis.

    PubMed

    Fabig, Gunar; Müller-Reichert, Thomas; Paliulis, Leocadia V

    2016-06-01

    In males of many taxa, univalent sex chromosomes normally segregate during the first meiotic division, and analysis of sex chromosome segregation was foundational for the chromosome theory of inheritance. Correct segregation of single or multiple univalent sex chromosomes occurs in a cellular environment where every other chromosome is a bivalent that is being partitioned into homologous chromosomes at anaphase I. The mechanics of univalent chromosome segregation vary among animal taxa. In some, univalents establish syntelic attachment of sister kinetochores to the spindle. In others, amphitelic attachment is established. Here, we review how this problem of segregation of unpaired chromosomes is solved in different animal systems. In addition, we give a short outlook of how mechanistic insights into this process could be gained by explicitly studying model organisms, such as Caenorhabditis elegans.

  19. Sex-determining mechanisms in insects based on imprinting and elimination of chromosomes.

    PubMed

    Sánchez, L

    2014-01-01

    As a rule, the sex of an individual is fixed at fertilization, and the chromosomal constitution of the zygote is a direct consequence of the chromosomal constitution of the gametes. However, there are cases in which the chromosomal differences determining sex are brought about by elimination or inactivation of chromosomes in the embryo. In Sciaridae insects, all zygotes start with the XXX constitution; the loss of either 1 or 2 X chromosomes determines whether the zygote becomes XX (female) or X0 (male). In Cecydomyiidae and Collembola insects, all zygotes start with the XXXX constitution. If the embryo does not eliminate any X chromosome, this remains XXXX and develops as female, whereas if 2 X chromosomes are eliminated, the embryo becomes XX0 and develops as a male. In the coccids (scale insects), the chromosomal differences between the sexes result from either the elimination or the heterochromatinization (inactivation) of half of the chromosomes giving rise to haploid males and diploid females. The chromosomes that are eliminated or inactivated are those inherited from the father. Therefore, in the formation of the sex-determining chromosomal signal in those insects, a marking ('imprinting') process must occur in one of the parents, which determines that the chromosomes to be eliminated or inactivated are of paternal origin. In this article, the sex determination mechanism of these insects and the associated imprinting process are reviewed.

  20. Evolution of Dosage Compensation in Anolis carolinensis, a Reptile with XX/XY Chromosomal Sex Determination

    PubMed Central

    Rupp, Shawn M.; Webster, Timothy H.; Olney, Kimberly C.; Hutchins, Elizabeth D.; Kusumi, Kenro

    2017-01-01

    In species with highly heteromorphic sex chromosomes, the degradation of one of the sex chromosomes will result in unequal gene expression between the sexes (e.g. between XX females and XY males) and between the sex chromosomes and the autosomes. Dosage compensation is a process whereby genes on the sex chromosomes achieve equal gene expression. We compared genome-wide levels of transcription between males and females, and between the X chromosome and the autosomes in the green anole, Anolis carolinensis. We present evidence for dosage compensation between the sexes, and between the sex chromosomes and the autosomes. When dividing the X chromosome into regions based on linkage groups, we discovered that genes in the first reported X-linked region, anole linkage group b (LGb), exhibit complete dosage compensation, although the rest of the X-linked genes exhibit incomplete dosage compensation. Our data further suggest that the mechanism of this dosage compensation is upregulation of the X chromosome in males. We report that approximately 10% of coding genes, most of which are on the autosomes, are differentially expressed between males and females. In addition, genes on the X chromosome exhibited higher ratios of nonsynonymous to synonymous substitution than autosomal genes, consistent with the fast-X effect. Our results from the green anole add an additional observation of dosage compensation in a species with XX/XY sex determination. PMID:28206607

  1. [Role of transposons in origin and evolution of plant XY sex chromosomes].

    PubMed

    Shufen, Li; Sha, Li; Chuanliang, Deng; Longdou, Lu; Wujun, Gao

    2015-02-01

    The XY sex-determination system is crucial for plant reproduction. However, little is known about the mechanism of the origin and evolution of the XY sex chromosomes. It has been believed that a pair of autosomes is evolved to produce young sex chromosomes (neo-X chromosome and neo-Y chromosome) by loss of function or gain of function mutation, which influences the development of pistil or stamen. With the aggravation of the recombination suppression between neo-X and neo-Y and consequent expanding of the non-recombination region, the proto-sex chromosomes were finally developed to heteromorphic sex chromosomes. Accumulation of repetitive sequences and DNA methylation were probably involved in this process. Transposons, as the most abundant repetitive sequences in the genome, might be the initial motivation factors for the evolution of sex chromosome. Moreover, transposons may also increase heterochromatin expansion and recombination suppression of sex chromosome by local epigenetics modification. In this review, we summarize the function of transposon accumulation and the relationship between transposon and heterochromatization in the evolution of plant sex chromosome.

  2. Sex chromosomes and karyotype of the (nearly) mythical creature, the Gila monster, Heloderma suspectum (Squamata: Helodermatidae).

    PubMed

    Johnson Pokorná, Martina; Rovatsos, Michail; Kratochvíl, Lukáš

    2014-01-01

    A wide variety of sex determination systems exist among squamate reptiles. They can therefore serve as an important model for studies of evolutionary transitions among particular sex determination systems. However, we still have only a limited knowledge of sex determination in certain important lineages of squamates. In this respect, one of the most understudied groups is the family Helodermatidae (Anguimorpha) encompassing the only two venomous species of lizards which are potentially lethal to human beings. We uncovered homomorphic ZZ/ZW sex chromosomes in the Gila monster (Heloderma suspectum) with a highly heterochromatic W chromosome. The sex chromosomes are morphologically similar to the ZZ/ZW sex chromosomes of monitor lizards (Varanidae). If the sex chromosomes of helodermatids and varanids are homologous, female heterogamety may be ancestral for the whole Anguimorpha group. Moreover, we found that the karyotype of the Gila monster consists of 2n = 36 chromosomes (14 larger metacentric chromosomes and 22 acrocentric microchromosomes). 2n = 36 is the widely distributed chromosomal number among squamates. In his pioneering works representing the only previous cytogenetic examination of the family Helodermatidae, Matthey reported the karyotype as 2n = 38 and suggested a different chromosomal morphology for this species. We believe that this was probably erroneously. We also discovered a strong accumulation of telomeric sequences on several pairs of microchromosomes in the Gila monster, which is a trait documented relatively rarely in vertebrates. These new data fill an important gap in our understanding of the sex determination and karyotype evolution of squamates.

  3. Sex differences in body fluid homeostasis: Sex chromosome complement influences on bradycardic baroreflex response and sodium depletion induced neural activity.

    PubMed

    Vivas, L; Dadam, F M; Caeiro, X E

    2015-12-01

    Clinical and basic findings indicate that angiotensin II (ANG II) differentially modulates hydroelectrolyte and cardiovascular responses in male and female. But are only the activational and organizational hormonal effects to blame for such differences? Males and females not only differ in their sex (males are born with testes and females with ovaries) but also carry different sex chromosome complements and are thus influenced throughout life by different genomes. In this review, we discuss our recent studies in order to evaluate whether sex chromosome complement is in part responsible for gender differences previously observed in ANG II bradycardic-baroreflex response and sodium depletion-induced sodium appetite and neural activity. To test the hypothesis that XX or XY contributes to the dimorphic ANG II bradycardic-baroreflex response, we used the four core genotype mouse model, in which the effects of gonadal sex (testes or ovaries) and sex chromosome complement (XX or XY) are dissociated. The results indicate that ANG II bradycardic-baroreflex sexual dimorphic response may be ascribed to differences in sex chromosomes, indicating an XX-sex chromosome complement facilitatory bradycardic-baroreflex control of heart rate. Furthermore, we evaluated whether genetic differences within the sex chromosome complement may differentially modulate the known sexually dimorphic sodium appetite as well as basal or induced brain activity due to physiological stimulation of the renin-angiotensin system by furosemide and low-sodium treatment. Our studies demonstrate an organizational hormonal effect on sexually dimorphic induced sodium intake in mice, while at the brain level (subfornical organ and area postrema) we showed a sex chromosome complement effect in sodium-depleted mice, suggesting a sex chromosome gene participation in the modulation of neural pathways underlying regulatory response to renin-angiotensin stimulation. Copyright © 2015 Elsevier Inc. All rights reserved.

  4. Phosphorylation of CDK2 on threonine 160 influences silencing of sex chromosome during male meiosis.

    PubMed

    Wang, Lu; Liu, Wenjing; Zhao, Weidong; Song, Gendi; Wang, Guishuan; Wang, Xiaorong; Sun, Fei

    2014-06-01

    In mammalian meiosis, the X and Y chromosomes are largely unsynapsed and transcriptionally silenced during the pachytene stage of meiotic prophase (meiotic sex chromosome inactivation), forming a specialized nuclear territory called sex or XY body. An increasing number of proteins and noncoding RNAs were found to localize to the sex body and take part in influencing expression of sex chromosome genes. Cyclin-dependent kinase 2 (Cdk2 (-/-)) spermatocytes show incomplete sex chromosome pairing. Here, we further showed that phosphorylation of CDK2 isoform 1 (p-CDK2(39) [39 kDa]) on threonine 160 localizes to the sites of asynapsis and the sex body, interacting with phosphorylated gamma-H2AX. Meanwhile, p-CDK2(39) is frequently mislocalized throughout the sex body, and meiotic sex chromosome inactivation is disrupted in PWK×C57BL/6J hybrid mice. Furthermore, pachytene spermatocytes treated with mevastatin (an inhibitor of p-CDK2) showed overexpression of sex chromosome-linked genes. Our results highlight an important role for p-CDK2(39) in influencing silencing of the sex chromosomes during male meiosis by interacting with gamma-H2AX.

  5. A Large Pseudoautosomal Region on the Sex Chromosomes of the Frog Silurana tropicalis

    PubMed Central

    Bewick, Adam J.; Chain, Frédéric J.J.; Zimmerman, Lyle B.; Sesay, Abdul; Gilchrist, Michael J.; Owens, Nick D.L.; Seifertova, Eva; Krylov, Vladimir; Macha, Jaroslav; Tlapakova, Tereza; Kubickova, Svatava; Cernohorska, Halina; Zarsky, Vojtech; Evans, Ben J.

    2013-01-01

    Sex chromosome divergence has been documented across phylogenetically diverse species, with amphibians typically having cytologically nondiverged (“homomorphic”) sex chromosomes. With an aim of further characterizing sex chromosome divergence of an amphibian, we used “RAD-tags” and Sanger sequencing to examine sex specificity and heterozygosity in the Western clawed frog Silurana tropicalis (also known as Xenopus tropicalis). Our findings based on approximately 20 million genotype calls and approximately 200 polymerase chain reaction-amplified regions across multiple male and female genomes failed to identify a substantially sized genomic region with genotypic hallmarks of sex chromosome divergence, including in regions known to be tightly linked to the sex-determining region. We also found that expression and molecular evolution of genes linked to the sex-determining region did not differ substantially from genes in other parts of the genome. This suggests that the pseudoautosomal region, where recombination occurs, comprises a large portion of the sex chromosomes of S. tropicalis. These results may in part explain why African clawed frogs have such a high incidence of polyploidization, shed light on why amphibians have a high rate of sex chromosome turnover, and raise questions about why homomorphic sex chromosomes are so prevalent in amphibians. PMID:23666865

  6. Psychosocial adaptation of 39 adolescents with sex chromosome abnormalities.

    PubMed

    Bender, B G; Harmon, R J; Linden, M G; Robinson, A

    1995-08-01

    Children with sex chromosome abnormalities (SCA) are known to be at increased risk for neuromotor, language, learning, and behavioral problems, but little is known of psychosocial adaptation of SCA adolescents. This study was conducted to evaluate psychologic characteristics of unselected SCA adolescents, including socialization, educational progress, separation from family, and incidence and severity of psychiatric disturbance. Thirty-nine propositi identified through the screening of 40,000 consecutive Denver newborns, including boys with 47,XXY karyotypes and girls with 47,XXX, 45,X, and partial X monosomy, or SCA mosaic karyotypes, have been followed longitudinally into adolescence. Twenty-seven siblings served as controls. Between 12 and 19 years of age, all participated in blind psychiatric interviews and were administered standardized intelligence and achievement tests. SCA propositi demonstrated a mean IQ score 21 points lower than that of control subjects. In addition, lower mean scores were seen on achievement test results as well as lower overall psychosocial adaptation scores and increased incidence of psychiatric disturbance. Depression was the most frequent psychiatric diagnosis. Propositi were more likely to receive special education assistance in high school and were less likely to graduate from high school than were controls. Of the three nonmosaic propositi groups, the 47,XXX girls demonstrated the poorest overall psychosocial adaptation and highest degree of psychiatric disturbance. Mosaic girls were indistinguishable from control subjects. Marked variability was found among all three nonmosaic groups, with some individuals in each group demonstrating relatively strong psychosocial adaptation. The presence of nonmosaic sex chromosome abnormality increases the risk for impeded cognitive skills, learning abilities, and psychosocial adaptation in adolescence. The factors that allow for stronger adaptation in some of these adolescents include the

  7. Sex chromosome loss and the pseudoautosomal region genes in hematological malignancies

    PubMed Central

    Weng, Stephanie; Stoner, Samuel A.; Zhang, Dong-Er

    2016-01-01

    Cytogenetic aberrations, such as chromosomal translocations, aneuploidy, and amplifications, are frequently detected in hematological malignancies. For many of the common autosomal aberrations, the mechanisms underlying their roles in cancer development have been well-characterized. On the contrary, although loss of a sex chromosome is observed in a broad range of hematological malignancies, how it cooperates in disease development is less understood. Nevertheless, it has been postulated that tumor suppressor genes reside on the sex chromosomes. Although the X and Y sex chromosomes are highly divergent, the pseudoautosomal regions are homologous between both chromosomes. Here, we review what is currently known about the pseudoautosomal region genes in the hematological system. Additionally, we discuss implications for haploinsufficiency of critical pseudoautosomal region sex chromosome genes, driven by sex chromosome loss, in promoting hematological malignancies. Because mechanistic studies on disease development rely heavily on murine models, we also discuss the challenges and caveats of existing models, and propose alternatives for examining the involvement of pseudoautosomal region genes and loss of a sex chromosome in vivo. With the widespread detection of loss of a sex chromosome in different hematological malignances, the elucidation of the role of pseudoautosomal region genes in the development and progression of these diseases would be invaluable to the field. PMID:27655702

  8. Differentiation of Sex Chromosomes and Karyotype Characterisation in the Dragonsnake Xenodermus javanicus (Squamata: Xenodermatidae).

    PubMed

    Rovatsos, Michail; Johnson Pokorná, Martina; Kratochvíl, Lukáš

    2015-01-01

    Highly differentiated heteromorphic ZZ/ZW sex chromosomes with a heterochromatic W are a basic principle among advanced snakes of the lineage Colubroidea, while other snake lineages generally lack these characteristics. For the first time, we cytogenetically examined the dragonsnake, Xenodermus javanicus, a member of the family Xenodermatidae, which is phylogenetically nested between snake lineages with and without differentiated sex chromosomes. Although most snakes have a karyotype with a stable chromosomal number of 2n = 36, the dragonsnake has an unusual, derived karyotype with 2n = 32 chromosomes. We found that heteromorphic ZZ/ZW sex chromosomes with a heterochromatic W are present in the dragonsnake, which suggests that the emergence of a highly differentiated W sex chromosome within snakes predates the split of Xenodermatidae and the clade including families Pareatidae, Viperidae, Homalopsidae, Lamprophiidae, Elapidae, and Colubridae. Although accumulations of interstitial telomeric sequences have not been previously reported in snakes, by using FISH with a telomeric probe we discovered them in 6 pairs of autosomes as well as in the W sex chromosome of the dragonsnake. Similarly to advanced snakes, the sex chromosomes of the dragonsnake have a significant accumulation of repeats containing a (GATA)n sequence. The results facilitate the dating of the differentiation of sex chromosomes within snakes back to the split between Xenodermatidae and other advanced snakes, i.e. around 40-75 mya.

  9. A role for a neo-sex chromosome in stickleback speciation

    PubMed Central

    Kitano, Jun; Ross, Joseph A.; Mori, Seiichi; Kume, Manabu; Jones, Felicity C.; Chan, Yingguang F.; Absher, Devin M.; Grimwood, Jane; Schmutz, Jeremy; Myers, Richard M.; Kingsley, David M.; Peichel, Catherine L.

    2009-01-01

    Sexual antagonism, or conflict between the sexes, has been proposed as a driving force in both sex chromosome turnover and speciation. Although closely related species often have different sex chromosome systems, it is unknown whether sex chromosome turnover contributes to the evolution of reproductive isolation between species. In this study, we show that a newly evolved sex chromosome harbours genes that contribute to speciation in threespine stickleback fish (Gasterosteus aculeatus). We first identified a neo-sex chromosome system found only in one member of a sympatric species pair in Japan. We then performed genetic linkage mapping of male-specific traits important for reproductive isolation between the Japanese species pair. The neo-X chromosome harbours loci for male courtship display traits that contribute to behavioural isolation, while the ancestral X chromosome contains loci for both behavioural isolation and hybrid male sterility. Our work not only provides strong evidence for a large-X effect on reproductive isolation in a vertebrate system, but also provides direct evidence that a young neo-X chromosome contributes to reproductive isolation between closely related species. Our data suggest that sex chromosome turnover might play a greater role in speciation than previously appreciated. PMID:19783981

  10. The Program of Sex Chromosome Pairing in Meiosis Is Highly Conserved Across Marsupial Species

    PubMed Central

    Page, Jesús; Berríos, Soledad; Parra, María Teresa; Viera, Alberto; Suja, José Ángel; Prieto, Ignacio; Barbero, José Luis; Rufas, Julio S.; Fernández-Donoso, Raúl

    2005-01-01

    Marsupials present a series of genetic and chromosomal features that are highly conserved in very distant species. One of these features is the absence of a homologous region between X and Y chromosomes. According to this genetic differentiation, sex chromosomes do not synapse during the first meiotic prophase in males, and a special structure, the dense plate, maintains sex chromosome association. In this report we present results on the process of meiotic sex chromosome pairing obtained from three different species, Thylamys elegans, Dromiciops gliroides, and Rhyncholestes raphanurus, representing the three orders of American marsupials. We have investigated the relationships between the axial structures organized along sex chromosomes and the formation of the dense plate. We found that in the three species the dense plate arises as a modification of sex chromosomal axial elements, but without the involvement of other meiotic axial structures, such as the cohesin axes. Considering the phylogenetic relationships among the marsupials studied here, our data reinforce the idea that the dense plate emerged early in marsupial evolution as an efficient mechanism to ensure the association of the nonhomologous sex chromosomes. This situation could have influenced the further evolution of sex chromosomes in marsupials. PMID:15802509

  11. A rare sex chromosome aneuploidy: 48,XXYY syndrome.

    PubMed

    Atik, Tahir; Çoğulu, Özgür; Özkınay, Ferda

    2016-06-01

    48,XXYY syndrome is a rare sex chromosome abnormality. Although some physical features are similar to Klinefelter syndrome(47,XXY), 48,XXYY is typically associated with different neuropsyhciatric symptoms and phenotypic findings. Approximately 100 cases with 48,XXYY have been reported to date. In this report, a patient who was diagnosed with 48,XXYY syndrome with clincal evaluation and cytogenetic analysis is presented. A 6-year old male patient was hospitalized due to recurrent respiratory tract infections, recurrent abdominal distention and dyspepsia. He was the first and only child of nonconsanguineous parents. He had a history of mild developmental retardation. In his history, it was learned that he received treatment for gastroesophageal reflux and his symptoms improved with treatment. On physical examination, his weight was found to be 31 kg (>97 centile) and his height was found to be 123 cm (90 centile). He had upslanted palpebral fissures, depressed nasal bridge, long philtrum, incomplete cleft lip and micrognathia. Clinodactilia was found in the fifth fingers in both hands and large big toes and adduction in the second and third toes were found in both feet. Karyotype analysis showed a chromosomal composition of 48,XXYY. The patient presented here is the second Turkish case of 48,XXYY syndrome.

  12. A rare sex chromosome aneuploidy: 48,XXYY syndrome

    PubMed Central

    Atik, Tahir; Çoğulu, Özgür; Özkınay, Ferda

    2016-01-01

    48,XXYY syndrome is a rare sex chromosome abnormality. Although some physical features are similar to Klinefelter syndrome(47,XXY), 48,XXYY is typically associated with different neuropsyhciatric symptoms and phenotypic findings. Approximately 100 cases with 48,XXYY have been reported to date. In this report, a patient who was diagnosed with 48,XXYY syndrome with clincal evaluation and cytogenetic analysis is presented. A 6-year old male patient was hospitalized due to recurrent respiratory tract infections, recurrent abdominal distention and dyspepsia. He was the first and only child of nonconsanguineous parents. He had a history of mild developmental retardation. In his history, it was learned that he received treatment for gastroesophageal reflux and his symptoms improved with treatment. On physical examination, his weight was found to be 31 kg (>97 centile) and his height was found to be 123 cm (90 centile). He had upslanted palpebral fissures, depressed nasal bridge, long philtrum, incomplete cleft lip and micrognathia. Clinodactilia was found in the fifth fingers in both hands and large big toes and adduction in the second and third toes were found in both feet. Karyotype analysis showed a chromosomal composition of 48,XXYY. The patient presented here is the second Turkish case of 48,XXYY syndrome. PMID:27489468

  13. Effects of Sex Chromosome Aneuploidies on Brain Development: Evidence from Neuroimaging Studies

    ERIC Educational Resources Information Center

    Lenroot, Rhoshel K.; Lee, Nancy Raitano; Giedd, Jay N.

    2009-01-01

    Variation in the number of sex chromosomes is a relatively common genetic condition, affecting as many as 1/400 individuals. The sex chromosome aneuploidies (SCAs) are associated with characteristic behavioral and cognitive phenotypes, although the degree to which specific individuals are affected can fall within a wide range. Understanding the…

  14. The dragon lizard Pogona vitticeps has ZZ/ZW micro-sex chromosomes.

    PubMed

    Ezaz, Tariq; Quinn, Alexander E; Miura, Ikuo; Sarre, Stephen D; Georges, Arthur; Marshall Graves, Jennifer A

    2005-01-01

    The bearded dragon, Pogona vitticeps (Agamidae: Reptilia) is an agamid lizard endemic to Australia. Like crocodilians and many turtles, temperature-dependent sex determination (TSD) is common in agamid lizards, although many species have genotypic sex determination (GSD). P. vitticeps is reported to have GSD, but no detectable sex chromosomes. Here we used molecular cytogenetic and differential banding techniques to reveal sex chromosomes in this species. Comparative genomic hybridization (CGH), GTG- and C-banding identified a highly heterochromatic microchromosome specific to females, demonstrating female heterogamety (ZZ/ZW) in this species. We isolated the P. vitticeps W chromosome by microdissection, re-amplified the DNA and used it to paint the W. No unpaired bivalents were detected in male synaptonemal complexes at meiotic pachytene, confirming male homogamety. We conclude that P. vitticeps has differentiated previously unidentifable W and Z micro-sex chromosomes, the first to be demonstrated in an agamid lizard. Our finding implies that heterochromatinization of the heterogametic chromosome occurred during sex chromosome differentiation in this species, as is the case in some lizards and many snakes, as well as in birds and mammals. Many GSD reptiles with cryptic sex chromosomes may also prove to have micro-sex chromosomes. Reptile microchromosomes, long dismissed as non-functional minutiae and often omitted from karyotypes, therefore deserve closer scrutiny with new and more sensitive techniques.

  15. Effects of Sex Chromosome Aneuploidies on Brain Development: Evidence from Neuroimaging Studies

    ERIC Educational Resources Information Center

    Lenroot, Rhoshel K.; Lee, Nancy Raitano; Giedd, Jay N.

    2009-01-01

    Variation in the number of sex chromosomes is a relatively common genetic condition, affecting as many as 1/400 individuals. The sex chromosome aneuploidies (SCAs) are associated with characteristic behavioral and cognitive phenotypes, although the degree to which specific individuals are affected can fall within a wide range. Understanding the…

  16. Genetic architecture of sexual dimorphism in a subdioecious plant with a proto-sex chromosome

    USDA-ARS?s Scientific Manuscript database

    Sexual dimorphism is thought to arise once sexually antagonistic genes accumulate on sex chromosomes early in their evolution. Yet because the earliest stages of sex chromosome evolution are elusive, we lack empirical evidence supporting this theory. In this study, we shed first light on the genetic...

  17. Location, location, location! Monotremes provide unique insights into the evolution of sex chromosome silencing in mammals.

    PubMed

    Daish, Tasman; Grützner, Frank

    2009-02-01

    Platypus and echidnas are the only living representative of the egg-laying mammals that diverged 166 million years ago from the mammalian lineage. Despite occupying a key spot in mammalian phylogeny, research on monotremes has been limited by access to material and lack of molecular genetic resources. This has changed recently, and the sequencing of the platypus genome has promoted monotremes into a generally accessible tool in comparative genomics. The most extraordinary aspect of the monotreme genome is an amazingly complex sex chromosomes system that shares extensive homology with bird sex chromosomes and no homology with sex chromosomes of other mammals. This raises important questions about dosage compensation of the five pairs of sex chromosomes in females and meiotic silencing in males, and we are only beginning to unravel possible mechanisms and pathways that may be involved. The homology between monotreme and bird sex chromosomes makes comparison between those species worthwhile, also as they provide a well-defined example where the same sex chromosomes changed from female heterogamety (chicken) to male heterogamety (monotremes). We summarize recent research on monotreme and chicken sex chromosomes and discuss possible mechanisms that may contribute to sex chromosome silencing in monotremes.

  18. Neo-sex chromosome diversity in Neotropical melanopline grasshoppers (Melanoplinae, Acrididae).

    PubMed

    Castillo, Elio R D; Bidau, Claudio J; Martí, Dardo A

    2010-07-01

    We report the results of a study on the neo-sex chromosome systems of six Neotropical Melanoplinae species for contributing to a better understanding of their origin and behaviour of these systems. Our analyses included detailed descriptions of the structure and behaviour of the sex chromosome configurations in male and female meiosis of species belonging to the genera Ronderosia, Dichromatos and Atrachelacris. Three species, R. forcipatus, R. malloi and A. unicolor, showed typical Robertsonian fusion-derived neo sex-chromosomes. However, the male metaphase I orientation of R. bergi sex pair indicated that more than one rearrangement was involved in its origin. The two species of Dichromatos presented a multiple neo-X(1)X(2)Y/X(1)X(1)X(2)X(2) sex system, with two Robertsonian fusions involved in their genesis. Observations of female meiosis, confirmed the nature of the sex-chromosomes analyzed. Our results also showed different degrees of homology divergence between the neo-sex chromosomes and emphasize the plasticity of the chromosome complement of the Neotropical Melanoplinae to establish Robertsonian fusions and generate novel sex-chromosome systems. We also discuss karyotypic diversity within this group in terms of the centromeric drive theory of chromosomal evolution.

  19. Loss of sex chromosomes in the hematopoietic disorders: Questions, concerns and data interpretation

    SciTech Connect

    Slovak, M.L.

    1994-09-01

    The significance of sex chromosome aberrations in the hematopoietic disorders has not yet been defined. Interpretive problems stem from (1) the loss of a sex chromosome associated with aging, (2) sex chromosome loss as the sole aberration in leukemia is rare, (3) random -(X or Y) is observed frequently in bone marrow samples, and (4) constitutional sex chromosome anomalies must be ruled out in cancer and follow-up may not be possible. The COH database identified 41 patients (pts) with sex chromosome loss. Loss of a sex chromosome was common in myeloid disorders (21/41). In t(8;21) leukemia (n=10), -(X or Y) was a common secondary karyotypic change. Additionally, -Y was associated with clonal evolution in 2 Ph + CML pts. In 2 elderly pts with myeloid disorders, -(X or Y) was observed in complex karyotypes with dmins; however, in the lymphoproliferative disorders -(X or Y) was noted in elderly pts without apparent pathogenetic significance. Three pts had constitutional sex chromosome aberrations: CML in 45,X; ALL in 47, XXY; and RAEB-IT in mos45,X/46,XX. In the mos45,X/46,XX pt, the leukemic clone was associated with the 45,X line without other karyotypic changes. Non-clonal aberrations were observed in 11 cases; in 3 cases these non-clonal losses were observed in serial samples. In a sex-mismatched BMT case, -(X or Y) in 4 cells was one of the first pathogenetic signs of leukemia relapse. These data suggest (1) interpretation of sex chromosome loss in leukemia must be made with caution and after a baseline sample, (2) non-clonal aberrations should be recorded, and (3) -(X or Y) appears to have pathogenetic significance in the myeloid disorders. Multi-institutional studies are needed to define (1) the incidence of leukemia in pts with constitutional sex chromosome anomalies and (2) the incidence and significance of sex chromosome aberrations as the primary (sole) cytogenetic aberration in leukemia.

  20. Preferential accumulation of sex and Bs chromosomes in biarmed karyotypes by meiotic drive and rates of chromosomal changes in fishes.

    PubMed

    Molina, Wagner F; Martinez, Pablo A; Bertollo, Luiz A C; Bidau, Claudio J

    2014-12-01

    Mechanisms of accumulation based on typical centromeric drive or of chromosomes carrying pericentric inversions are adjusted to the general karyotype differentiation in the principal Actinopterygii orders. Here, we show that meiotic drive in fish is also supported by preferential establishment of sex chromosome systems and B chromosomes in orders with predominantly bi-brachial chromosomes. The mosaic of trends acting at an infra-familiar level in fish could be explained as the interaction of the directional process of meiotic drive as background, modulated on a smaller scale by adaptive factors or specific karyotypic properties of each group, as proposed for the orthoselection model.

  1. Fatness QTL on chicken chromosome 5 and interaction with sex

    PubMed Central

    Abasht, Behnam; Pitel, Frédérique; Lagarrigue, Sandrine; Le Bihan-Duval, Elisabeth; Le Roy, Pascale; Demeure, Olivier; Vignoles, Florence; Simon, Jean; Cogburn, Larry; Aggrey, Sammy; Vignal, Alain; Douaire, Madeleine

    2006-01-01

    Quantitative trait loci (QTL) affecting fatness in male chickens were previously identified on chromosome 5 (GGA5) in a three-generation design derived from two experimental chicken lines divergently selected for abdominal fat weight. A new design, established from the same pure lines, produced 407 F2 progenies (males and females) from 4 F1-sire families. Body weight and abdominal fat were measured on the F2 at 9 wk of age. In each sire family, selective genotyping was carried out for 48 extreme individuals for abdominal fat using seven microsatellite markers from GGA5. QTL analyses confirmed the presence of QTL for fatness on GGA5 and identified a QTL by sex interaction. By crossing one F1 sire heterozygous at the QTL with lean line dams, three recombinant backcross 1 (BC1) males were produced and their QTL genotypes were assessed in backcross 2 (BC2) progenies. These results confirmed the QTL by sex interaction identified in the F2 generation and they allow mapping of the female QTL to less than 8 Mb at the distal part of the GGA5. They also indicate that fat QTL alleles were segregating in both fat and lean lines. PMID:16635451

  2. The Number of X Chromosomes Causes Sex Differences in Adiposity in Mice

    PubMed Central

    Chen, Xuqi; McClusky, Rebecca; Chen, Jenny; Beaven, Simon W.; Tontonoz, Peter

    2012-01-01

    Sexual dimorphism in body weight, fat distribution, and metabolic disease has been attributed largely to differential effects of male and female gonadal hormones. Here, we report that the number of X chromosomes within cells also contributes to these sex differences. We employed a unique mouse model, known as the “four core genotypes,” to distinguish between effects of gonadal sex (testes or ovaries) and sex chromosomes (XX or XY). With this model, we produced gonadal male and female mice carrying XX or XY sex chromosome complements. Mice were gonadectomized to remove the acute effects of gonadal hormones and to uncover effects of sex chromosome complement on obesity. Mice with XX sex chromosomes (relative to XY), regardless of their type of gonad, had up to 2-fold increased adiposity and greater food intake during daylight hours, when mice are normally inactive. Mice with two X chromosomes also had accelerated weight gain on a high fat diet and developed fatty liver and elevated lipid and insulin levels. Further genetic studies with mice carrying XO and XXY chromosome complements revealed that the differences between XX and XY mice are attributable to dosage of the X chromosome, rather than effects of the Y chromosome. A subset of genes that escape X chromosome inactivation exhibited higher expression levels in adipose tissue and liver of XX compared to XY mice, and may contribute to the sex differences in obesity. Overall, our study is the first to identify sex chromosome complement, a factor distinguishing all male and female cells, as a cause of sex differences in obesity and metabolism. PMID:22589744

  3. The number of x chromosomes causes sex differences in adiposity in mice.

    PubMed

    Chen, Xuqi; McClusky, Rebecca; Chen, Jenny; Beaven, Simon W; Tontonoz, Peter; Arnold, Arthur P; Reue, Karen

    2012-01-01

    Sexual dimorphism in body weight, fat distribution, and metabolic disease has been attributed largely to differential effects of male and female gonadal hormones. Here, we report that the number of X chromosomes within cells also contributes to these sex differences. We employed a unique mouse model, known as the "four core genotypes," to distinguish between effects of gonadal sex (testes or ovaries) and sex chromosomes (XX or XY). With this model, we produced gonadal male and female mice carrying XX or XY sex chromosome complements. Mice were gonadectomized to remove the acute effects of gonadal hormones and to uncover effects of sex chromosome complement on obesity. Mice with XX sex chromosomes (relative to XY), regardless of their type of gonad, had up to 2-fold increased adiposity and greater food intake during daylight hours, when mice are normally inactive. Mice with two X chromosomes also had accelerated weight gain on a high fat diet and developed fatty liver and elevated lipid and insulin levels. Further genetic studies with mice carrying XO and XXY chromosome complements revealed that the differences between XX and XY mice are attributable to dosage of the X chromosome, rather than effects of the Y chromosome. A subset of genes that escape X chromosome inactivation exhibited higher expression levels in adipose tissue and liver of XX compared to XY mice, and may contribute to the sex differences in obesity. Overall, our study is the first to identify sex chromosome complement, a factor distinguishing all male and female cells, as a cause of sex differences in obesity and metabolism.

  4. Sex chromosomes evolved from independent ancestral linkage groups in winged insects.

    PubMed

    Pease, James B; Hahn, Matthew W

    2012-06-01

    The evolution of a pair of chromosomes that differ in appearance between males and females (heteromorphic sex chromosomes) has occurred repeatedly across plants and animals. Recent work has shown that the male heterogametic (XY) and female heterogametic (ZW) sex chromosomes evolved independently from different pairs of homomorphic autosomes in the common ancestor of birds and mammals but also that X and Z chromosomes share many convergent molecular features. However, little is known about how often heteromorphic sex chromosomes have either evolved convergently from different autosomes or in parallel from the same pair of autosomes and how universal patterns of molecular evolution on sex chromosomes really are. Among winged insects with sequenced genomes, there are male heterogametic species in both the Diptera (e.g., Drosophila melanogaster) and the Coleoptera (Tribolium castaneum), female heterogametic species in the Lepidoptera (Bombyx mori), and haplodiploid species in the Hymenoptera (e.g., Nasonia vitripennis). By determining orthologous relationships among genes on the X and Z chromosomes of insects with sequenced genomes, we are able to show that these chromosomes are not homologous to one another but are homologous to autosomes in each of the other species. These results strongly imply that heteromorphic sex chromosomes have evolved independently from different pairs of ancestral chromosomes in each of the insect orders studied. We also find that the convergently evolved X chromosomes of Diptera and Coleoptera share genomic features with each other and with vertebrate X chromosomes, including excess gene movement from the X to the autosomes. However, other patterns of molecular evolution--such as increased codon bias, decreased gene density, and the paucity of male-biased genes on the X--differ among the insect X and Z chromosomes. Our results provide evidence for both differences and nearly universal similarities in patterns of evolution among

  5. Description of the pre-reductional sex chromosome during male meiosis of Pachylis laticornis (Heteroptera: Coreidae).

    PubMed

    Banho, C A; Alevi, K C C; Pereira, L L V; Souza-Firmino, T S; Itoyama, M M

    2016-04-28

    In Heteroptera, the division of sex chromosomes is well defined as post-reductional for most of species, i.e., the first meiotic division is equational and the second is reductional. However, in some species pre-reductional division has been observed, whereby the first meiotic division is reductional and the second is equational. These include Anisops fieberi (Notonectidae), Ectrychotes disparate (Reduviidae), Dictyonota tricornis (Tingidae), and Archimerus alternatus (Coreidae), as well as other species of the genus Pachylis, in the family Coreidae. Thus, this study aimed to characterize the meiotic behavior of Pachylis laticornis, in order to consider whether this species also undergoes pre-reduction division for the sex chromosomes. Cytogenetic analysis of meiosis in P. laticornis made it possible to characterize the holocentric nature of the chromosomes, the chromosome number of this species [2n = 15 (2m + 12A + X0)], the chromosomal system of sex X0 type, and the presence of m-chromosomes. Furthermore, the analysis of anaphase I, telophase I and II allowed pre-reductional meiotic behavior to be observed for this sex chromosome. Thus, this meiotic behavior was confirmed for another species of Heteroptera, stressing the importance of more cytogenetic studies of meiosis to increase our understanding of variation in the behavior of sex chromosomes during spermatogenesis in heteropterans. Therefore, the present study describes the chromosomal number, the system of sex determination, and meiotic behavior of P. laticornis, corroborating the relationship of this species with others of the same genus.

  6. Sex chromosome-specific regulation in the Drosophila male germline but little evidence for chromosomal dosage compensation or meiotic inactivation.

    PubMed

    Meiklejohn, Colin D; Landeen, Emily L; Cook, Jodi M; Kingan, Sarah B; Presgraves, Daven C

    2011-08-01

    The evolution of heteromorphic sex chromosomes (e.g., XY in males or ZW in females) has repeatedly elicited the evolution of two kinds of chromosome-specific regulation: dosage compensation--the equalization of X chromosome gene expression in males and females--and meiotic sex chromosome inactivation (MSCI)--the transcriptional silencing and heterochromatinization of the X during meiosis in the male (or Z in the female) germline. How the X chromosome is regulated in the Drosophila melanogaster male germline is unclear. Here we report three new findings concerning gene expression from the X in Drosophila testes. First, X chromosome-wide dosage compensation appears to be absent from most of the Drosophila male germline. Second, microarray analysis provides no evidence for X chromosome-specific inactivation during meiosis. Third, we confirm the previous discovery that the expression of transgene reporters driven by autosomal spermatogenesis-specific promoters is strongly reduced when inserted on the X chromosome versus the autosomes; but we show that this chromosomal difference in expression is established in premeiotic cells and persists in meiotic cells. The magnitude of the X-autosome difference in transgene expression cannot be explained by the absence of dosage compensation, suggesting that a previously unrecognized mechanism limits expression from the X during spermatogenesis in Drosophila. These findings help to resolve several previously conflicting reports and have implications for patterns of genome evolution and speciation in Drosophila.

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

    PubMed

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

    2006-04-01

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

  8. DNA replication in the sex chromosomes of the pronghorn and the Rocky Mountain goat.

    PubMed

    Dain, A

    1977-01-01

    The X chromosomes of the male pronghorn (Antilocapra americana) is larger than the "original" type and carries a large segment of late-labelling chromatin. The Y chromosome has a late-labelling segment that appears to duplicate synchronously with that of the X. Both chromosomes have segments that label throughout the period of observation; that the X is about 4.7% of the haploid complement and approaches "original" proportions. The X chromosomes of the Rocky Mountain goat (Oreamnos americanus) appear to be of the "original" type, without marked late-labelling regions, and the Y chromosomes is small. The structure and origin of extra-large sex chromosomes are discussed.

  9. The fragile Y hypothesis: Y chromosome aneuploidy as a selective pressure in sex chromosome and meiotic mechanism evolution.

    PubMed

    Blackmon, Heath; Demuth, Jeffery P

    2015-09-01

    Loss of the Y-chromosome is a common feature of species with chromosomal sex determination. However, our understanding of why some lineages frequently lose Y-chromosomes while others do not is limited. The fragile Y hypothesis proposes that in species with chiasmatic meiosis the rate of Y-chromosome aneuploidy and the size of the recombining region have a negative correlation. The fragile Y hypothesis provides a number of novel insights not possible under traditional models. Specifically, increased rates of Y aneuploidy may impose positive selection for (i) gene movement off the Y; (ii) translocations and fusions which expand the recombining region; and (iii) alternative meiotic segregation mechanisms (achiasmatic or asynaptic). These insights as well as existing evidence for the frequency of Y-chromosome aneuploidy raise doubt about the prospects for long-term retention of the human Y-chromosome despite recent evidence for stable gene content in older non-recombining regions.

  10. The origin and evolution of vertebrate sex chromosomes and dosage compensation

    PubMed Central

    Livernois, A M; Graves, J A M; Waters, P D

    2012-01-01

    In mammals, birds, snakes and many lizards and fish, sex is determined genetically (either male XY heterogamy or female ZW heterogamy), whereas in alligators, and in many reptiles and turtles, the temperature at which eggs are incubated determines sex. Evidently, different sex-determining systems (and sex chromosome pairs) have evolved independently in different vertebrate lineages. Homology shared by Xs and Ys (and Zs and Ws) within species demonstrates that differentiated sex chromosomes were once homologous, and that the sex-specific non-recombining Y (or W) was progressively degraded. Consequently, genes are left in single copy in the heterogametic sex, which results in an imbalance of the dosage of genes on the sex chromosomes between the sexes, and also relative to the autosomes. Dosage compensation has evolved in diverse species to compensate for these dose differences, with the stringency of compensation apparently differing greatly between lineages, perhaps reflecting the concentration of genes on the original autosome pair that required dosage compensation. We discuss the organization and evolution of amniote sex chromosomes, and hypothesize that dosage insensitivity might predispose an autosome to evolving function as a sex chromosome. PMID:22086077

  11. Caenorhabditis elegans histone methyltransferase MET-2 shields the male X chromosome from checkpoint machinery and mediates meiotic sex chromosome inactivation.

    PubMed

    Checchi, Paula M; Engebrecht, JoAnne

    2011-09-01

    Meiosis is a specialized form of cellular division that results in the precise halving of the genome to produce gametes for sexual reproduction. Checkpoints function during meiosis to detect errors and subsequently to activate a signaling cascade that prevents the formation of aneuploid gametes. Indeed, asynapsis of a homologous chromosome pair elicits a checkpoint response that can in turn trigger germline apoptosis. In a heterogametic germ line, however, sex chromosomes proceed through meiosis with unsynapsed regions and are not recognized by checkpoint machinery. We conducted a directed RNAi screen in Caenorhabditis elegans to identify regulatory factors that prevent recognition of heteromorphic sex chromosomes as unpaired and uncovered a role for the SET domain histone H3 lysine 9 histone methyltransferase (HMTase) MET-2 and two additional HMTases in shielding the male X from checkpoint machinery. We found that MET-2 also mediates the transcriptional silencing program of meiotic sex chromosome inactivation (MSCI) but not meiotic silencing of unsynapsed chromatin (MSUC), suggesting that these processes are distinct. Further, MSCI and checkpoint shielding can be uncoupled, as double-strand breaks targeted to an unpaired, transcriptionally silenced extra-chromosomal array induce checkpoint activation in germ lines depleted for met-2. In summary, our data uncover a mechanism by which repressive chromatin architecture enables checkpoint proteins to distinguish between the partnerless male X chromosome and asynapsed chromosomes thereby shielding the lone X from inappropriate activation of an apoptotic program.

  12. The genetic contribution to sex determination and number of sex chromosomes vary among populations of common frogs (Rana temporaria).

    PubMed

    Rodrigues, N; Vuille, Y; Brelsford, A; Merilä, J; Perrin, N

    2016-07-01

    The patterns of sex determination and sex differentiation have been shown to differ among geographic populations of common frogs. Notably, the association between phenotypic sex and linkage group 2 (LG2) has been found to be perfect in a northern Swedish population, but weak and variable among families in a southern one. By analyzing these populations with markers from other linkage groups, we bring two new insights: (1) the variance in phenotypic sex not accounted for by LG2 in the southern population could not be assigned to genetic factors on other linkage groups, suggesting an epigenetic component to sex determination; (2) a second linkage group (LG7) was found to co-segregate with sex and LG2 in the northern population. Given the very short timeframe since post-glacial colonization (in the order of 1000 generations) and its seemingly localized distribution, this neo-sex chromosome system might be the youngest one described so far. It does not result from a fusion, but more likely from a reciprocal translocation between the original Y chromosome (LG2) and an autosome (LG7), causing their co-segregation during male meiosis. By generating a strict linkage between several important genes from the sex-determination cascade (Dmrt1, Amh and Amhr2), this neo-sex chromosome possibly contributes to the 'differentiated sex race' syndrome (strictly genetic sex determination and early gonadal development) that characterizes this northern population.

  13. Multiple Sex-Associated Regions and a Putative Sex Chromosome in Zebrafish Revealed by RAD Mapping and Population Genomics

    PubMed Central

    Anderson, Jennifer L.; Rodríguez Marí, Adriana; Braasch, Ingo; Amores, Angel; Hohenlohe, Paul; Batzel, Peter; Postlethwait, John H.

    2012-01-01

    Within vertebrates, major sex determining genes can differ among taxa and even within species. In zebrafish (Danio rerio), neither heteromorphic sex chromosomes nor single sex determination genes of large effect, like Sry in mammals, have yet been identified. Furthermore, environmental factors can influence zebrafish sex determination. Although progress has been made in understanding zebrafish gonad differentiation (e.g. the influence of germ cells on gonad fate), the primary genetic basis of zebrafish sex determination remains poorly understood. To identify genetic loci associated with sex, we analyzed F2 offspring of reciprocal crosses between Oregon *AB and Nadia (NA) wild-type zebrafish stocks. Genome-wide linkage analysis, using more than 5,000 sequence-based polymorphic restriction site associated (RAD-tag) markers and population genomic analysis of more than 30,000 single nucleotide polymorphisms in our *ABxNA crosses revealed a sex-associated locus on the end of the long arm of chr-4 for both cross families, and an additional locus in the middle of chr-3 in one cross family. Additional sequencing showed that two SNPs in dmrt1 previously suggested to be functional candidates for sex determination in a cross of ABxIndia wild-type zebrafish, are not associated with sex in our AB fish. Our data show that sex determination in zebrafish is polygenic and that different genes may influence sex determination in different strains or that different genes become more important under different environmental conditions. The association of the end of chr-4 with sex is remarkable because, unique in the karyotype, this chromosome arm shares features with known sex chromosomes: it is highly heterochromatic, repetitive, late replicating, and has reduced recombination. Our results reveal that chr-4 has functional and structural properties expected of a sex chromosome. PMID:22792396

  14. Fetal sex chromosome testing by maternal plasma DNA sequencing: clinical laboratory experience and biology.

    PubMed

    Bianchi, Diana W; Parsa, Saba; Bhatt, Sucheta; Halks-Miller, Meredith; Kurtzman, Kathryn; Sehnert, Amy J; Swanson, Amy

    2015-02-01

    To describe the clinical experience with noninvasive prenatal testing for fetal sex chromosomes using sequencing of maternal plasma cell-free DNA in a commercial laboratory. A noninvasive prenatal testing laboratory data set was examined for samples in which fetal sex chromosomes were reported. Available clinical outcomes were reviewed. Of 18,161 samples with sex chromosome results, no sex chromosome aneuploidy was detected in 98.9% and the fetal sex was reported as XY (9,236) or XX (8,721). In 4 of 32 cases in which the fetal sex was reportedly discordant between noninvasive prenatal testing and karyotype or ultrasonogram, a potential biological reason for the discordance exists, including two cases of documented co-twin demise, one case of a maternal kidney transplant from a male donor, and one case of fetal ambiguous genitalia. In the remaining 204 samples (1.1%), one of four sex chromosome aneuploidies (monosomy X, XXX, XXY, or XYY) was detected. The frequency of false positive results for sex chromosome aneuploidies is a minimum of 0.26% and a maximum of 1.05%. All but one of the discordant sex chromosome aneuploidy results involved the X chromosome. In two putative false-positive XXX cases, maternal XXX was confirmed by karyotype. For the false-positive cases, mean maternal age was significantly higher in monosomy X (P<.001) and lower in XXX (P=.008). Noninvasive prenatal testing results for sex chromosome aneuploidy can be confounded by maternal or fetal biological phenomena. When a discordant noninvasive prenatal testing result is encountered, resolution requires additional maternal history, detailed fetal ultrasonography, and determination of fetal and possibly maternal karyotypes.

  15. Pachytene asynapsis drives meiotic sex chromosome inactivation and leads to substantial postmeiotic repression in spermatids.

    PubMed

    Turner, James M A; Mahadevaiah, Shantha K; Ellis, Peter J I; Mitchell, Michael J; Burgoyne, Paul S

    2006-04-01

    Transcriptional silencing of the sex chromosomes during male meiosis (MSCI) is conserved among organisms with limited sex chromosome synapsis, including mammals. Since the 1990s the prevailing view has been that MSCI in mammals is transient, with sex chromosome reactivation occurring as cells exit meiosis. Recently, we found that any chromosome region unsynapsed during pachytene of male and female mouse meiosis is subject to transcriptional silencing (MSUC), and we hypothesized that MSCI is an inevitable consequence of this more general meiotic silencing mechanism. Here, we provide direct evidence that asynapsis does indeed drive MSCI. We also show that a substantial degree of transcriptional repression of the sex chromosomes is retained postmeiotically, and we provide evidence that this postmeiotic repression is a downstream consequence of MSCI/MSUC. While this postmeiotic repression occurs after the loss of MSUC-related proteins at the end of prophase, other histone modifications associated with transcriptional repression have by then become established.

  16. The chromosomal distribution of microsatellite repeats in the genome of the wolf fish Hoplias malabaricus, focusing on the sex chromosomes.

    PubMed

    Cioffi, M B; Kejnovsky, E; Bertollo, L A C

    2011-01-01

    Distribution of 12 mono-, di- and tri-nucleotide microsatellites on the chromosomes of 2 karyomorphs with 2 distinct sex chromosome systems (a simple XX/XY - karyomorph B and a multiple X(1)X(1)X(2)X(2)/X(1)X(2)Y - karyomorph D) in Hoplias malabaricus, commonly referred to as wolf fish, was studied using their physical mapping with fluorescence in situ hybridization (FISH). The distribution patterns of different microsatellites along the chromosomes varied considerably. Strong hybridization signals were observed at subtelomeric and heterochromatic regions of several autosomes, with a different accumulation on the sex chromosomes. A massive accumulation was found in the heterochromatic region of the X chromosome of karyomorph B, whereas microsatellites were gathered at centromeres of both X chromosomes as well as in corresponding regions of the neo-Y chromosome in karyomorph D. Our findings are likely in agreement with models that predict the accumulation of repetitive DNA sequences in regions with very low recombination. This process is however in contrast with what was observed in multiple systems, where such a reduction might be facilitated by the chromosomal rearrangements that are directly associated with the origin of these systems.

  17. Sex chromosome system ZZ/ZW in Apareiodon hasemani Eigenmann, 1916 (Characiformes, Parodontidae) and a derived chromosomal region

    PubMed Central

    Bellafronte, Elisangela; Schemberger, Michelle Orane; Artoni, Roberto Ferreira; Filho, Orlando Moreira; Vicari, Marcelo Ricardo

    2012-01-01

    Parodontidae fish show few morphological characteristics for the identification of their representatives and chromosomal analyses have provided reliable features for determining the interrelationships in this family. In this study, the chromosomes of Apareiodon hasemani from the São Francisco River basin, Brazil, were analyzed and showed a karyotype with 2n = 54 meta/submetacentric chromosomes, and a ZZ/ZW sex chromosome system. The study revealed active NORs located on pair 11 and additional 18S rDNA sites on pairs 7 and 22. The 5S rDNA locus was found in pair 14. It showed a pericentric inversion regarding the ancestral condition. The satellite DNA pPh2004 was absent in the chromosomes of A. hasemani, a shared condition with most members of Apareiodon. The WAp probe was able to detect the amplification region of the W chromosome, corroborating the common origin of the system within Parodontidae. These chromosomal data corroborate an origin for the ZW system of Parodontidae and aid in the understanding of the differentiation of sex chromosome systems in Neotropical fishes. PMID:23271937

  18. 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.

  19. Allometric Analysis Detects Brain Size-Independent Effects of Sex and Sex Chromosome Complement on Human Cerebellar Organization.

    PubMed

    Mankiw, Catherine; Park, Min Tae M; Reardon, P K; Fish, Ari M; Clasen, Liv S; Greenstein, Deanna; Giedd, Jay N; Blumenthal, Jonathan D; Lerch, Jason P; Chakravarty, M Mallar; Raznahan, Armin

    2017-03-17

    The cerebellum is a large hindbrain structure that is increasingly recognized for its contribution to diverse domains of cognitive and affective processing in human health and disease. Although several of these domains are sex-biased, our fundamental understanding of cerebellar sex differences - including their spatial distribution, potential biological determinants, and independence from brain volume variation - lags far behind that for the cerebrum. Here, we harness automated neuroimaging methods for cerebellar morphometrics in 417 individuals to (i) localize normative male-female differences in raw cerebellar volume, (ii) compare these to sex chromosome effects estimated across five rare X-/Y-chromosome aneuploidy (SCA) syndromes, and (iii) clarify brain size-independent effects of sex and SCA on cerebellar anatomy using a generalizable allometric approach which considers scaling relationships between regional cerebellar volume and brain volume in health. Integration of these approaches shows that (i) sex and SCA effects on raw cerebellar volume are large and distributed, but regionally heterogeneous, (ii) human cerebellar volume scales with brain volume in a highly non-linear and regionally heterogeneous fashion that departs from documented patterns of cerebellar scaling in phylogeny, and (iii) cerebellar organization is modified in a brain size-independent manner by sex (relative expansion of total cerebellum, flocculus, and Crus II-lobule VIIIB volumes in males) and SCA (contraction of total cerebellar, lobule IV and Crus I volumes with additional X- or Y-chromosomes; X-specific contraction of Crus II-lobule VIIIB). Our methods and results clarify the shifts in human cerebellar organization that accompany interwoven variations in sex, sex chromosome complement, and brain size.SIGNIFICANCE STATEMENTCerebellar systems are implicated in diverse domains of sex-biased behavior and pathology, but we lack a basic understanding of how sex differences in the human

  20. First Description of the Karyotype and Sex Chromosomes in the Komodo Dragon (Varanus komodoensis).

    PubMed

    Johnson Pokorná, Martina; Altmanová, Marie; Rovatsos, Michail; Velenský, Petr; Vodička, Roman; Rehák, Ivan; Kratochvíl, Lukáš

    2016-01-01

    The Komodo dragon (Varanus komodoensis) is the largest lizard in the world. Surprisingly, it has not yet been cytogenetically examined. Here, we present the very first description of its karyotype and sex chromosomes. The karyotype consists of 2n = 40 chromosomes, 16 macrochromosomes and 24 microchromosomes. Although the chromosome number is constant for all species of monitor lizards (family Varanidae) with the currently reported karyotype, variability in the morphology of the macrochromosomes has been previously documented within the group. We uncovered highly differentiated ZZ/ZW sex microchromosomes with a heterochromatic W chromosome in the Komodo dragon. Sex chromosomes have so far only been described in a few species of varanids including V. varius, the sister species to Komodo dragon, whose W chromosome is notably larger than that of the Komodo dragon. Accumulations of several microsatellite sequences in the W chromosome have recently been detected in 3 species of monitor lizards; however, these accumulations are absent from the W chromosome of the Komodo dragon. In conclusion, although varanids are rather conservative in karyotypes, their W chromosomes exhibit substantial variability at the sequence level, adding further evidence that degenerated sex chromosomes may represent the most dynamic genome part.

  1. The X Chromosome of Hemipteran Insects: Conservation, Dosage Compensation and Sex-Biased Expression

    PubMed Central

    Pal, Arka; Vicoso, Beatriz

    2015-01-01

    Insects of the order Hemiptera (true bugs) use a wide range of mechanisms of sex determination, including genetic sex determination, paternal genome elimination, and haplodiploidy. Genetic sex determination, the prevalent mode, is generally controlled by a pair of XY sex chromosomes or by an XX/X0 system, but different configurations that include additional sex chromosomes are also present. Although this diversity of sex determining systems has been extensively studied at the cytogenetic level, only the X chromosome of the model pea aphid Acyrthosiphon pisum has been analyzed at the genomic level, and little is known about X chromosome biology in the rest of the order. In this study, we take advantage of published DNA- and RNA-seq data from three additional Hemiptera species to perform a comparative analysis of the gene content and expression of the X chromosome throughout this clade. We find that, despite showing evidence of dosage compensation, the X chromosomes of these species show female-biased expression, and a deficit of male-biased genes, in direct contrast to the pea aphid X. We further detect an excess of shared gene content between these very distant species, suggesting that despite the diversity of sex determining systems, the same chromosomal element is used as the X throughout a large portion of the order. PMID:26556591

  2. The X Chromosome of Hemipteran Insects: Conservation, Dosage Compensation and Sex-Biased Expression.

    PubMed

    Pal, Arka; Vicoso, Beatriz

    2015-11-10

    Insects of the order Hemiptera (true bugs) use a wide range of mechanisms of sex determination, including genetic sex determination, paternal genome elimination, and haplodiploidy. Genetic sex determination, the prevalent mode, is generally controlled by a pair of XY sex chromosomes or by an XX/X0 system, but different configurations that include additional sex chromosomes are also present. Although this diversity of sex determining systems has been extensively studied at the cytogenetic level, only the X chromosome of the model pea aphid Acyrthosiphon pisum has been analyzed at the genomic level, and little is known about X chromosome biology in the rest of the order.In this study, we take advantage of published DNA- and RNA-seq data from three additional Hemiptera species to perform a comparative analysis of the gene content and expression of the X chromosome throughout this clade. We find that, despite showing evidence of dosage compensation, the X chromosomes of these species show female-biased expression, and a deficit of male-biased genes, in direct contrast to the pea aphid X. We further detect an excess of shared gene content between these very distant species, suggesting that despite the diversity of sex determining systems, the same chromosomal element is used as the X throughout a large portion of the order.

  3. Sex Chromosome Complement Influences Operant Responding for a Palatable Food in Mice

    PubMed Central

    Arnold, Arthur P.; Jentsch, J. David

    2014-01-01

    The procurement and consumption of palatable, calorie-dense foods is influenced by the nutritional and hedonic value of foods. Although many factors can influence the control over behavior by foods rich in sugar and fat, emerging evidence indicates that biological sex may play a particularly crucial role in the types of foods individuals seek out, as well as the level of motivation individuals will exert to obtain those foods. However, a systematic investigation of food-seeking and consumption that disentangles the effects of the major sex-biasing factors, including sex chromosome complement and organizational and activational effects of sex hormones, has yet to be conducted. Using the four core genotypes mouse model system, we separated and quantified the effects of sex chromosome complement and gonadal sex on consumption of and motivation to obtain a highly-palatable solution (sweetened condensed milk – SCM). Gonadectomized mice with an XY sex chromosome complement, compared to those with two X chromosomes, independent of gonadal sex, appeared to be more sensitive to the reward value of the SCM solution and were more motivated to expend effort to obtain it, as evidenced by their dramatically greater expended effort in an instrumental task with progressively larger response-to-reward ratios. Gonadal sex independently affected free consumption of the solution but not motivation to obtain it. These data indicate that gonadal and chromosomal sex effects independently influence reward-related behaviors, contributing to sexually dimorphic patterns of behavior related to the pursuit and consumption of rewards. PMID:24861924

  4. Sex chromosome complement influences operant responding for a palatable food in mice.

    PubMed

    Seu, E; Groman, S M; Arnold, A P; Jentsch, J D

    2014-07-01

    The procurement and consumption of palatable, calorie-dense foods is influenced by the nutritional and hedonic value of foods. Although many factors can influence the control over behavior by foods rich in sugar and fat, emerging evidence indicates that biological sex may play a particularly crucial role in the types of foods individuals seek out, as well as the level of motivation individuals will exert to obtain those foods. However, a systematic investigation of food-seeking and consumption that disentangles the effects of the major sex-biasing factors, including sex chromosome complement and organizational and activational effects of sex hormones, has yet to be conducted. Using the four core genotypes mouse model system, we separated and quantified the effects of sex chromosome complement and gonadal sex on consumption of and motivation to obtain a highly palatable solution [sweetened condensed milk (SCM)]. Gonadectomized mice with an XY sex chromosome complement, compared with those with two X chromosomes, independent of gonadal sex, appeared to be more sensitive to the reward value of the SCM solution and were more motivated to expend effort to obtain it, as evidenced by their dramatically greater expended effort in an instrumental task with progressively larger response-to-reward ratios. Gonadal sex independently affected free consumption of the solution but not motivation to obtain it. These data indicate that gonadal and chromosomal sex effects independently influence reward-related behaviors, contributing to sexually dimorphic patterns of behavior related to the pursuit and consumption of rewards.

  5. Autism, language and communication in children with sex chromosome trisomies

    PubMed Central

    Bishop, Dorothy V M; Jacobs, Patricia A; Lachlan, Katherine; Wellesley, Diana; Barnicoat, Angela; Boyd, Patricia A; Fryer, Alan; Middlemiss, Prisca; Smithson, Sarah; Metcalfe, Kay; Shears, Deborah; Leggett, Victoria; Nation, Kate; Scerif, Gaia

    2011-01-01

    Purpose Sex chromosome trisomies (SCTs) are found on amniocentesis in 2.3–3.7 per 1000 same-sex births, yet there is a limited database on which to base a prognosis. Autism has been described in postnatally diagnosed cases of Klinefelter syndrome (XXY karyotype), but the prevalence in non-referred samples, and in other trisomies, is unclear. The authors recruited the largest sample including all three SCTs to be reported to date, including children identified on prenatal screening, to clarify this issue. Design Parents of children with a SCT were recruited either via prenatal screening or via a parental support group, to give a sample of 58 XXX, 19 XXY and 58 XYY cases. Parents were interviewed using the Vineland Adaptive Behavior Scales and completed questionnaires about the communicative development of children with SCTs and their siblings (42 brothers and 26 sisters). Results Rates of language and communication problems were high in all three trisomies. Diagnoses of autism spectrum disorder (ASD) were found in 2/19 cases of XXY (11%) and 11/58 XYY (19%). After excluding those with an ASD diagnosis, communicative profiles indicative of mild autistic features were common, although there was wide individual variation. Conclusions Autistic features have not previously been remarked upon in studies of non-referred samples with SCTs, yet the rate is substantially above population levels in this sample, even when attention is restricted to early-identified cases. The authors hypothesise that X-linked and Y-linked neuroligins may play a significant role in the aetiology of communication impairments and ASD. PMID:20656736

  6. Extensive Genetic Differentiation between Homomorphic Sex Chromosomes in the Mosquito Vector, Aedes aegypti.

    PubMed

    Fontaine, Albin; Filipovic, Igor; Fansiri, Thanyalak; Hoffmann, Ary A; Cheng, Changde; Kirkpatrick, Mark; Rašic, Gordana; Lambrechts, Louis

    2017-09-01

    Mechanisms and evolutionary dynamics of sex-determination systems are of particular interest in insect vectors of human pathogens like mosquitoes because novel control strategies aim to convert pathogen-transmitting females into nonbiting males, or rely on accurate sexing for the release of sterile males. In Aedes aegypti, the main vector of dengue and Zika viruses, sex determination is governed by a dominant male-determining locus, previously thought to reside within a small, nonrecombining, sex-determining region (SDR) of an otherwise homomorphic sex chromosome. Here, we provide evidence that sex chromosomes in Ae. aegypti are genetically differentiated between males and females over a region much larger than the SDR. Our linkage mapping intercrosses failed to detect recombination between X and Y chromosomes over a 123-Mbp region (40% of their physical length) containing the SDR. This region of reduced male recombination overlapped with a smaller 63-Mbp region (20% of the physical length of the sex chromosomes) displaying high male-female genetic differentiation in unrelated wild populations from Brazil and Australia and in a reference laboratory strain originating from Africa. In addition, the sex-differentiated genomic region was associated with a significant excess of male-to-female heterozygosity and contained a small cluster of loci consistent with Y-specific null alleles. We demonstrate that genetic differentiation between sex chromosomes is sufficient to assign individuals to their correct sex with high accuracy. We also show how data on allele frequency differences between sexes can be used to estimate linkage disequilibrium between loci and the sex-determining locus. Our discovery of large-scale genetic differentiation between sex chromosomes in Ae. aegypti lays a new foundation for mapping and population genomic studies, as well as for mosquito control strategies targeting the sex-determination pathway. © The Author 2017. Published by Oxford University

  7. Physical chromosome mapping of repetitive DNA sequences in Nile tilapia Oreochromis niloticus: evidences for a differential distribution of repetitive elements in the sex chromosomes.

    PubMed

    Ferreira, Irani A; Martins, Cesar

    2008-06-01

    Repetitive DNAs have been extensively applied as physical chromosome markers on comparative studies, identification of chromosome rearrangements and sex chromosomes, chromosome evolution analysis, and applied genetics. Here we report the characterization of repetitive DNA sequences from the Nile tilapia (Oreochromis niloticus) genome by construction and screening of plasmid library enriched with repetitive DNAs, analysis of a BAC-based physical map, and hybridization to chromosomes. The physical mapping of BACs enriched with repetitive sequences and C(o)t-1 DNA (DNA enriched for highly and moderately repetitive DNA sequences) to chromosomes using FISH showed a predominant distribution of repetitive elements in the centromeric and telomeric regions and along the entire length of the largest chromosome pair (X and Y sex chromosomes) of the species. The distribution of repetitive DNAs differed significantly between the p arm of X and Y chromosomes. These findings suggest that repetitive DNAs have had an important role in the differentiation of sex chromosomes.

  8. Parental decisions of prenatally detected sex chromosome abnormality.

    PubMed Central

    Kim, Yon-Ju; Park, So-Yeon; Han, Jung-Heol; Kim, Moon-Young; Yang, Jae-Hyug; Choi, Kyu-Hong; Kim, Young-Mi; Kim, Jin-Mee; Ryu, Hyun-Mee

    2002-01-01

    Because of the widespread use of amniocentesis, the prenatal recognition of sex chromosome abnormality (SCA) has become increasingly common. Recent literature provided an insight into the understanding of the natural history and prognosis for individuals with SCA. Our study was designed to review the parental decision on pregnancy with SCA. Over the last 10 yr, we diagnosed 38 cases (0.50%) with SCA out of 7,498 prenatal cases. We reviewed the records and the results of the pregnancies. We included the cases (n=25) of apparently normal anatomic fetus to analyze the factors influencing parental decision. We excluded 13 cases with obvious anomaly or presumably bad outcome. Fifteen (60%) couples continued their pregnancies and ten (40%) terminated theirs. Nine couples (64%) out of fourteen mosaicism cases continued their pregnancies. All five pregnancies assisted by reproductive technique continued their pregnancies. More pregnancies were continued when counseling was done by an MD geneticist rather than by an obstetrician. A significant trend was observed with a higher rate of pregnancy continuation in recent years. The genetic counseling is important to give appropriate information to the parents. Establishing guidelines and protocols will help both obstetricians and parents to make a decision. PMID:11850589

  9. Children with sex chromosome trisomies: parental disclosure of genetic status.

    PubMed

    Gratton, Nikki C; Myring, Jessica; Middlemiss, Prisca; Shears, Deborah; Wellesley, Diana; Wynn, Sarah; Bishop, Dorothy Vm; Scerif, Gaia

    2016-05-01

    Sex chromosome trisomies (SCTs) are frequently diagnosed, both prenatally and postnatally, but the highly variable childhood outcomes can leave parents at a loss on whether, when and how to disclose genetic status. In two complementary studies, we detail current parental practices, with a view to informing parents and their clinicians. Study 1 surveyed detailed qualitative data from focus groups of parents and affected young people with either Trisomy X or XYY (N=34 families). These data suggested that decisions to disclose were principally affected by the child's level of cognitive, social and emotional functioning. Parents reported that they were more likely to disclose when a child was experiencing difficulties. In Study 2, standardised data on cognitive, social and emotional outcomes in 126 children with an SCT and 63 sibling controls highlighted results that converged with Study 1: logistic regression analyses revealed that children with the lowest levels of functioning were more likely to know about their SCT than those children functioning at a higher level. These effects were also reflected in the likelihood of parents to disclose to unaffected siblings, schools and general practitioners. In contrast, specific trisomy type and the professional category of the clinician providing the original diagnosis did not affect likelihood of disclosure. Our study emphasises the complex weighing up of costs and benefits that parents engage in when deciding whether to disclose a diagnosis.

  10. Neuropsychological impairment in 42 adolescents with sex chromosome abnormalities.

    PubMed

    Bender, B G; Linden, M G; Robinson, A

    1993-10-15

    Sixty-seven adolescents participated in this protocol, including 42 with sex chromosome abnormalities and 25 controls. Results from a battery of neuropsychological tests indicated karyotype specific patterns of neuropsychological impairment: (1) 47,XXY boys had unimpaired intelligence but reduced abilities in verbal fluency and reading; (2) 47,XXX girls experienced reduced general intelligence accompanied by impaired scores on individual tests of attention, concept formation, spatial thinking, verbal fluency, and academic skills, while retention of memorized information was a relative strength; (3) among the 45,X girls average intelligence level was also reduced along with scores on tests of attention, concept formation, verbal fluency, spatial thinking, and academic skills, and an atypical pattern of hand dominance was identified; (4) test scores in the group of mosaic females did not differ from those of controls. Test scores and patterns of personal adaptation were quite variable in all groups; while eight nonmosaic propositi required intensive special education assistance in their public schooling, eight others have attended college.

  11. 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.

  12. An integrated cytogenetic and physical map reveals unevenly distributed recombination spots along the papaya sex chromosomes.

    PubMed

    Wai, Ching Man; Moore, Paul H; Paull, Robert E; Ming, Ray; Yu, Qingyi

    2012-08-01

    Papaya is a model system for the study of sex chromosome evolution in plants. However, the cytological structures of the papaya chromosomes remain largely unknown and chromosomal features have not been linked with any genetic or genomic data. We constructed a cytogenetic map of the papaya sex chromosome (chromosome 1) by hybridizing 16 microsatellite markers and 2 cytological feature-associated markers on pachytene chromosomes using fluorescence in situ hybridization (FISH). Except for three markers, the order of the markers was concordant to that of marker loci along the linkage map. This discrepancy was likely caused by skewed segregation in the highly heterochromatic or centromeric regions. The papaya sex chromosome is largely euchromatic, its heterochromatin spans about 15 % of the Y chromosome and is mostly restricted to the centromeric and pericentromeric regions. Analysis of the recombination frequency along the papaya sex chromosome revealed a complete suppression of recombination in the centromere and pericentromere region and 60 % higher recombination rate in the long arm than in the short arm. The uneven distribution of recombination events might be caused by differences in sequence composition. Sequence analysis of 18 scaffolds in total length of 15 Mb revealed higher gene density towards the telomeres and lower gene density towards the centromere, and a relatively higher gene density in the long arm than in the short arm. In an opposite trend, the centromeric and pericentromeric region contained the highest repetitive sequences and the long arm showed the lowest repetitive sequences. This cytogenetic map provides essential information for evolutionary study of sex chromosomes in Caricaceae and will facilitate the analysis of papaya sex chromosomes.

  13. Contrasting patterns of X/Y polymorphism distinguish Carica papaya from other sex chromosome systems.

    PubMed

    Weingartner, Laura A; Moore, Richard C

    2012-12-01

    The sex chromosomes of the tropical crop papaya (Carica papaya) are evolutionarily young and consequently allow for the examination of evolutionary mechanisms that drive early sex chromosome divergence. We conducted a molecular population genetic analysis of four X/Y gene pairs from a collection of 45 wild papaya accessions. These population genetic analyses reveal striking differences in the patterns of polymorphism between the X and Y chromosomes that distinguish them from other sex chromosome systems. In most sex chromosome systems, the Y chromosome displays significantly reduced polymorphism levels, whereas the X chromosome maintains a level of polymorphism that is comparable to autosomal loci. However, the four papaya sex-linked loci that we examined display diversity patterns that are opposite this trend: the papaya X alleles exhibit significantly reduced polymorphism levels, whereas the papaya Y alleles maintain greater than expected levels of diversity. Our analyses suggest that selective sweeps in the regions of the X have contributed to this pattern while also revealing geographically restricted haplogroups on the Y. We discuss the possible role sexual selection and/or genomic conflict have played in shaping the contrasting patterns of polymorphism found for the papaya X and Y chromosomes.

  14. Effects of Sex Chromosome Aneuploidies on Brain Development: Evidence From Neuroimaging Studies

    PubMed Central

    Lenroot, Rhoshel K.; Lee, Nancy Raitano; Giedd, Jay N.

    2010-01-01

    Variation in the number of sex chromosomes is a relatively common genetic condition, affecting as many as 1/400 individuals. The sex chromosome aneuploidies (SCAs) are associated with characteristic behavioral and cognitive phenotypes, although the degree to which specific individuals are affected can fall within a wide range. Understanding the effects of different dosages of sex chromosome genes on brain development may help to understand the basis for functional differences in affected individuals. It may also be informative regarding how sex chromosomes contribute to typical sexual differentiation. Studies of 47,XXY males make up the bulk of the current literature of neuroimaging studies in individuals with supernumerary sex chromosomes, with a few small studies or case reports of the other SCAs. Findings in 47,XXY males typically include decreased gray and white matter volumes, with most pronounced effects in the frontal and temporal lobes. Functional studies have shown evidence of decreased lateralization. Although the hypogonadism typically found in 47,XXY males may contribute to the decreased brain volume, the observation that 47,XXX females also show decreased brain volume in the presence of normal pubertal maturation suggests a possible direct dosage effect of X chromosome genes. Additional X chromosomes, such as in 49,XXXXY males, are associated with more markedly decreased brain volume and increased incidence of white matter hyperintensities. The limited data regarding effects of having two Y chromosomes (47,XYY) do not find significant differences in brain volume, although there are some reports of increased head size. PMID:20014372

  15. Non-homologous sex chromosomes of birds and snakes share repetitive sequences.

    PubMed

    O'Meally, Denis; Patel, Hardip R; Stiglec, Rami; Sarre, Stephen D; Georges, Arthur; Marshall Graves, Jennifer A; Ezaz, Tariq

    2010-11-01

    Snake sex chromosomes provided Susumo Ohno with the material on which he based his theory of how sex chromosomes differentiate from autosomal pairs. Like birds, snakes have a ZZ male/ZW female sex chromosome system, in which the snake Z is a macrochromosome much the same size as the bird Z. However, the gene content shows clearly that the snake and bird Z chromosomes are completely non-homologous. The molecular aspect of W chromosome degeneration in snakes remains largely unexplored. We used comparative genomic hybridization to identify the female-specific region of the W chromosome in representative species of Australian snakes. Using this approach, we show that an increasingly complex suite of repeats accompanies the evolution of W chromosome heteromorphy. In particular, we found that while the python Liasis fuscus exhibits no sex-specific repeats and indeed, no cytologically recognizable sex-specific region, the colubrid Stegonotus cucullatus shows a large domain on the short arm of the W chromosome that consists of female-specific repeats, and the large W of Notechis scutatus is composed almost entirely of repetitive sequences, including Bkm and 18S rDNA-related elements. FISH mapping of both simple and complex probes shows patterns of repeat amplification concordant with the size of the female-specific region in each species examined. Mapping of intronic sequences of genes that are sex-linked in both birds (DMRT1) and snakes (CTNNB1) reveals massive amplification in discrete domains on the W chromosome of the elapid N. scutatus. Using chicken W chromosome paint, we demonstrate that repetitive sequences are shared between the sex chromosomes of birds and derived snakes. This could be explained by ancestral but as yet undetected shared synteny of bird and snake sex chromosomes or may indicate functional homology of the repeats and suggests that degeneration is a convergent property of sex chromosome evolution. We also establish that synteny of snake Z

  16. Sex Chromosomes and Karyotype of the (Nearly) Mythical Creature, the Gila Monster, Heloderma suspectum (Squamata: Helodermatidae)

    PubMed Central

    Pokorná, Martina Johnson; Rovatsos, Michail; Kratochvíl, Lukáš

    2014-01-01

    A wide variety of sex determination systems exist among squamate reptiles. They can therefore serve as an important model for studies of evolutionary transitions among particular sex determination systems. However, we still have only a limited knowledge of sex determination in certain important lineages of squamates. In this respect, one of the most understudied groups is the family Helodermatidae (Anguimorpha) encompassing the only two venomous species of lizards which are potentially lethal to human beings. We uncovered homomorphic ZZ/ZW sex chromosomes in the Gila monster (Heloderma suspectum) with a highly heterochromatic W chromosome. The sex chromosomes are morphologically similar to the ZZ/ZW sex chromosomes of monitor lizards (Varanidae). If the sex chromosomes of helodermatids and varanids are homologous, female heterogamety may be ancestral for the whole Anguimorpha group. Moreover, we found that the karyotype of the Gila monster consists of 2n = 36 chromosomes (14 larger metacentric chromosomes and 22 acrocentric microchromosomes). 2n = 36 is the widely distributed chromosomal number among squamates. In his pioneering works representing the only previous cytogenetic examination of the family Helodermatidae, Matthey reported the karyotype as 2n = 38 and suggested a different chromosomal morphology for this species. We believe that this was probably erroneously. We also discovered a strong accumulation of telomeric sequences on several pairs of microchromosomes in the Gila monster, which is a trait documented relatively rarely in vertebrates. These new data fill an important gap in our understanding of the sex determination and karyotype evolution of squamates. PMID:25119263

  17. The genomic distribution of sex-biased genes in drosophila serrata: X chromosome demasculinization, feminization, and hyperexpression in both sexes.

    PubMed

    Allen, Scott L; Bonduriansky, Russell; Chenoweth, Stephen F

    2013-01-01

    The chromosomal distribution of genes with sex-biased expression is often nonrandom, and in species with XY sex chromosome systems, it is common to observe a deficit of X-linked male-biased genes and an excess of X-linked female-biased genes. One explanation for this pattern is that sex-specific selection has shaped the gene content of the X. Alternatively, the deficit of male-biased and excess of female-biased genes could be an artifact of differences between the sexes in the global expression level of their X chromosome(s), perhaps brought about by a lack of dosage compensation in males and hyperexpression in females. In the montium fruit fly, Drosophila serrata, both these explanations can account for a deficit of male-biased and excess of female-biased X-linked genes. Using genome-wide expression data from multiple male and female tissues (n = 176 hybridizations), we found that testis- and accessory gland-specific genes are underrepresented whereas female ovary-specific genes are overrepresented on the X chromosome, suggesting that X-linkage is disfavored for male function genes but favored for female function genes. However, genes with such sex-specific functions did not fully account for the deficit of male-biased and excess of female-biased X-linked genes. We did, however, observe sex differences in the global expression level of the X chromosome and autosomes. Surprisingly, and in contrast to other species where a lack of dosage compensation in males is responsible, we found that hyperexpression of X-linked genes in both sexes leads to this imbalance in D. serrata. Our results highlight how common genomic distributions of sex-biased genes, even among closely related species, may arise via quite different evolutionary processes.

  18. The Genomic Distribution of Sex-Biased Genes in Drosophila serrata: X Chromosome Demasculinization, Feminization, and Hyperexpression in Both Sexes

    PubMed Central

    Allen, Scott L.; Bonduriansky, Russell; Chenoweth, Stephen F.

    2013-01-01

    The chromosomal distribution of genes with sex-biased expression is often nonrandom, and in species with XY sex chromosome systems, it is common to observe a deficit of X-linked male-biased genes and an excess of X-linked female-biased genes. One explanation for this pattern is that sex-specific selection has shaped the gene content of the X. Alternatively, the deficit of male-biased and excess of female-biased genes could be an artifact of differences between the sexes in the global expression level of their X chromosome(s), perhaps brought about by a lack of dosage compensation in males and hyperexpression in females. In the montium fruit fly, Drosophila serrata, both these explanations can account for a deficit of male-biased and excess of female-biased X-linked genes. Using genome-wide expression data from multiple male and female tissues (n = 176 hybridizations), we found that testis- and accessory gland-specific genes are underrepresented whereas female ovary-specific genes are overrepresented on the X chromosome, suggesting that X-linkage is disfavored for male function genes but favored for female function genes. However, genes with such sex-specific functions did not fully account for the deficit of male-biased and excess of female-biased X-linked genes. We did, however, observe sex differences in the global expression level of the X chromosome and autosomes. Surprisingly, and in contrast to other species where a lack of dosage compensation in males is responsible, we found that hyperexpression of X-linked genes in both sexes leads to this imbalance in D. serrata. Our results highlight how common genomic distributions of sex-biased genes, even among closely related species, may arise via quite different evolutionary processes. PMID:24084777

  19. Expression and epigenomic landscape of the sex chromosomes in mouse post-meiotic male germ cells.

    PubMed

    Moretti, Charlotte; Vaiman, Daniel; Tores, Frederic; Cocquet, Julie

    2016-01-01

    During meiosis, the X and Y chromosomes are transcriptionally silenced. The persistence of repressive chromatin marks on the sex chromatin after meiosis initially led to the assumption that XY gene silencing persists to some extent in spermatids. Considering the many reports of XY-linked genes expressed and needed in the post-meiotic phase of mouse spermatogenesis, it is still unclear whether or not the mouse sex chromatin is a repressive or permissive environment, after meiosis. To determine the transcriptional and chromatin state of the sex chromosomes after meiosis, we re-analyzed ten ChIP-Seq datasets performed on mouse round spermatids and four RNA-seq datasets from male germ cells purified at different stages of spermatogenesis. For this, we used the last version of the genome (mm10/GRCm38) and included reads that map to several genomic locations in order to properly interpret the high proportion of sex chromosome-encoded multicopy genes. Our study shows that coverage of active epigenetic marks H3K4me3 and Kcr is similar on the sex chromosomes and on autosomes. The post-meiotic sex chromatin nevertheless differs from autosomal chromatin in its enrichment in H3K9me3 and its depletion in H3K27me3 and H4 acetylation. We also identified a posttranslational modification, H3K27ac, which specifically accumulates on the Y chromosome. In parallel, we found that the X and Y chromosomes are enriched in genes expressed post-meiotically and display a higher proportion of spermatid-specific genes compared to autosomes. Finally, we observed that portions of chromosome 14 and of the sex chromosomes share specific features, such as enrichment in H3K9me3 and the presence of multicopy genes that are specifically expressed in round spermatids, suggesting that parts of chromosome 14 are under the same evolutionary constraints than the sex chromosomes. Based on our expression and epigenomic studies, we conclude that, after meiosis, the mouse sex chromosomes are no longer silenced

  20. Evidence for Different Origins of Sex Chromosomes in Closely Related Oryzias Fishes: Substitution of the Master Sex-Determining Gene

    PubMed Central

    Tanaka, Keita; Takehana, Yusuke; Naruse, Kiyoshi; Hamaguchi, Satoshi; Sakaizumi, Mitsuru

    2007-01-01

    The medaka Oryzias latipes and its two sister species, O. curvinotus and O. luzonensis, possess an XX–XY sex-determination system. The medaka sex-determining gene DMY has been identified on the orthologous Y chromosome [O. latipes linkage group 1 (LG1)] of O. curvinotus. However, DMY has not been discovered in other Oryzias species. These results and molecular phylogeny suggest that DMY was generated recently [∼10 million years ago (MYA)] by gene duplication of DMRT1 in a common ancestor of O. latipes and O. curvinotus. We identified seven sex-linked markers from O. luzonensis (sister species of O. curvinotus) and constructed a sex-linkage map. Surprisingly, all seven sex-linked markers were located on an autosomal linkage group (LG12) of O. latipes. As suggested by the phylogenetic tree, the sex chromosomes of O. luzonensis should be “younger” than those of O. latipes. In the lineage leading to O. luzonensis after separation from O. curvinotus ∼5 MYA, a novel sex-determining gene may have arisen and substituted for DMY. Oryzias species should provide a useful model for evolution of the master sex-determining gene and differentiation of sex chromosomes from autosomes. PMID:17947439

  1. Chromosomal Mapping of Repetitive DNAs in Myiopsitta monachus and Amazona aestiva (Psittaciformes, Psittacidae) with Emphasis on the Sex Chromosomes.

    PubMed

    de Oliveira Furo, Ivanete; Kretschmer, Rafael; Dos Santos, Michelly S; de Lima Carvalho, Carlos A; Gunski, Ricardo J; O'Brien, Patrícia C M; Ferguson-Smith, Malcolm A; Cioffi, Marcelo B; de Oliveira, Edivaldo H C

    2017-01-01

    Here, for the first time, we describe the karyotype of Myiopsitta monachus (Psittacidae, Arini). We found 2n = 48, corresponding to the lowest diploid number observed in Neotropical Psittaciformes so far, with an uncommonly large W chromosome homomorphic to the Z. In order to better understand the evolution of the sex chromosomes in this species, we applied several molecular cytogenetic approaches, including C-banding, FISH mapping of repetitive DNAs (several microsatellite repeats), and whole-chromosome painting on metaphases of M. monachus. For comparison, another species belonging to the same tribe but with a smaller W chromosome (A. aestiva) was also analyzed. The results show that the constitutive heterochromatin has a very diverse distribution pattern in these species revealing heterochromatic blocks in the centromeric region of all chromosomes and in most of the length of the W chromosome in A. aestiva, while in M. monachus they were found in interstitial and telomeric regions. Concerning the microsatellites, only the sequence (CG)n produced signals on the W chromosome of A. aestiva, in the distal region of both arms. However, in M. monachus, (CAA)n, (CAG)n, and (CG)n probes were accumulated on the W chromosome, and, in addition, the sequence (CAG)n also hybridized to heterochromatic regions in macrochromosomes, as well as in microchromosomes. Based on these results, we suggest that the increase in length of the W chromosome in M. monachus is due to the amplification of repetitive elements, which highlights their significant role in the evolutionary process of sex chromosome differentiation. © 2017 S. Karger AG, Basel.

  2. Repetitive DNA Sequences and Evolution of ZZ/ZW Sex Chromosomes in Characidium (Teleostei: Characiformes).

    PubMed

    Scacchetti, Priscilla Cardim; Utsunomia, Ricardo; Pansonato-Alves, José Carlos; da Costa Silva, Guilherme José; Vicari, Marcelo Ricardo; Artoni, Roberto Ferreira; Oliveira, Claudio; Foresti, Fausto

    2015-01-01

    Characidium constitutes an interesting model for cytogenetic studies, since a large degree of karyotype variation has been detected in this group, like the presence/absence of sex and supernumerary chromosomes and variable distribution of repetitive sequences in different species/populations. In this study, we performed a comparative cytogenetic analysis in 13 Characidium species collected at different South American river basins in order to investigate the karyotype diversification in this group. Chromosome analyses involved the karyotype characterization, cytogenetic mapping of repetitive DNA sequences and cross-species chromosome painting using a W-specific probe obtained in a previous study from Characidium gomesi. Our results evidenced a conserved diploid chromosome number of 2n = 50, and almost all the species exhibited homeologous ZZ/ZW sex chromosomes in different stages of differentiation, except C. cf. zebra, C. tenue, C. xavante and C. stigmosum. Notably, some ZZ/ZW sex chromosomes showed 5S and/or 18S rDNA clusters, while no U2 snDNA sites could be detected in the sex chromosomes, being restricted to a single chromosome pair in almost all the analyzed species. In addition, the species Characidium sp. aff. C. vidali showed B chromosomes with an inter-individual variation of 1 to 4 supernumerary chromosomes per cell. Notably, these B chromosomes share sequences with the W-specific probe, providing insights about their origin. Results presented here further confirm the extensive karyotype diversity within Characidium in contrast with a conserved diploid chromosome number. Such chromosome differences seem to constitute a significant reproductive barrier, since several sympatric Characidium species had been described during the last few years and no interespecific hybrids were found.

  3. Repetitive DNA Sequences and Evolution of ZZ/ZW Sex Chromosomes in Characidium (Teleostei: Characiformes)

    PubMed Central

    Pansonato-Alves, José Carlos; da Costa Silva, Guilherme José; Vicari, Marcelo Ricardo; Artoni, Roberto Ferreira; Oliveira, Claudio; Foresti, Fausto

    2015-01-01

    Characidium constitutes an interesting model for cytogenetic studies, since a large degree of karyotype variation has been detected in this group, like the presence/absence of sex and supernumerary chromosomes and variable distribution of repetitive sequences in different species/populations. In this study, we performed a comparative cytogenetic analysis in 13 Characidium species collected at different South American river basins in order to investigate the karyotype diversification in this group. Chromosome analyses involved the karyotype characterization, cytogenetic mapping of repetitive DNA sequences and cross-species chromosome painting using a W-specific probe obtained in a previous study from Characidium gomesi. Our results evidenced a conserved diploid chromosome number of 2n = 50, and almost all the species exhibited homeologous ZZ/ZW sex chromosomes in different stages of differentiation, except C. cf. zebra, C. tenue, C. xavante and C. stigmosum. Notably, some ZZ/ZW sex chromosomes showed 5S and/or 18S rDNA clusters, while no U2 snDNA sites could be detected in the sex chromosomes, being restricted to a single chromosome pair in almost all the analyzed species. In addition, the species Characidium sp. aff. C. vidali showed B chromosomes with an inter-individual variation of 1 to 4 supernumerary chromosomes per cell. Notably, these B chromosomes share sequences with the W-specific probe, providing insights about their origin. Results presented here further confirm the extensive karyotype diversity within Characidium in contrast with a conserved diploid chromosome number. Such chromosome differences seem to constitute a significant reproductive barrier, since several sympatric Characidium species had been described during the last few years and no interespecific hybrids were found. PMID:26372604

  4. Third party annotation gene data set of eutherian lysozyme genes.

    PubMed

    Premzl, Marko

    2014-12-01

    The eutherian comparative genomic analysis protocol annotated most comprehensive eutherian lysozyme gene data set. Among 209 potential coding sequences, the third party annotation gene data set of eutherian lysozyme genes included 116 complete coding sequences that first described seven major gene clusters. As one new framework of future experiments, the present integrated gene annotations, phylogenetic analysis and protein molecular evolution analysis proposed new classification and nomenclature of eutherian lysozyme genes.

  5. Independent stratum formation on the avian sex chromosomes reveals inter-chromosomal gene conversion and predominance of purifying selection on the W chromosome.

    PubMed

    Wright, Alison E; Harrison, Peter W; Montgomery, Stephen H; Pointer, Marie A; Mank, Judith E

    2014-11-01

    We used a comparative approach spanning three species and 90 million years to study the evolutionary history of the avian sex chromosomes. Using whole transcriptomes, we assembled the largest cross-species dataset of W-linked coding content to date. Our results show that recombination suppression in large portions of the avian sex chromosomes has evolved independently, and that long-term sex chromosome divergence is consistent with repeated and independent inversions spreading progressively to restrict recombination. In contrast, over short-term periods we observe heterogeneous and locus-specific divergence. We also uncover four instances of gene conversion between both highly diverged and recently evolved gametologs, suggesting a complex mosaic of recombination suppression across the sex chromosomes. Lastly, evidence from 16 gametologs reveal that the W chromosome is evolving with a significant contribution of purifying selection, consistent with previous findings that W-linked genes play an important role in encoding sex-specific fitness. © 2014 The Authors. Evolution published by Wiley Periodicals, Inc. on behalf of The Society for the Study of Evolution.

  6. Dynamics of sex expression and chromosome diversity in Cucurbitaceae: a story in the making.

    PubMed

    Bhowmick, Biplab Kumar; Jha, Sumita

    2015-12-01

    The family Cucurbitaceae showcases a wide range of sexual phenotypes being variedly regulated by biological and environmental factors. In the present context, we have tried to assemble reports of cytogenetic investigations carried out in cucurbits accompanied by information on sex expression diversities and chromosomal or molecular basis of sex determination in dioecious (or other sexual types, if reported) taxa known so far. Most of the Cucurbitaceae tribes have mixed sexual phenotypes with varying range of chromosome numbers and hence, ancestral conditions become difficult to probe. Occurrence of polyploidy is rare in the family and has no influence on sexual traits. The sex determination mechanisms have been elucidated in some well-studied taxa like Bryonia,Coccinia and Cucumis showing interplay of genic, biochemical, developmental and sometimes chromosomal determinants. Substantial knowledge about genic and molecular sex differentiation has been obtained for genera like Momordica, Cucurbita and Trichosanthes. The detailed information on sex determination schemes, genomic sequences and molecular phylogenetic relationships facilitate further comprehensive investigations in the tribe Bryonieae. The discovery of organ identity genes and sex-specific sequences regulating sexual behaviour in Coccinia,Cucumis and Cucurbita opens up opportunities of relevant investigations to answer yet unaddressed questions pertaining to floral unisexuality, dioecy and chromosome evolution in the family. The present discussion brings the genera in light, previously recognized under subfamily Nhandiroboideae, where the study of chromosome cytology and sex determination mechanisms can simplify our understanding of sex expression pathways and its phylogenetic impacts.

  7. Differentiation of sex chromosomes and karyotypic evolution in the eye-lid geckos (Squamata: Gekkota: Eublepharidae), a group with different modes of sex determination.

    PubMed

    Pokorná, Martina; Rábová, Marie; Ráb, Petr; Ferguson-Smith, Malcolm A; Rens, Willem; Kratochvíl, Lukáš

    2010-11-01

    The eyelid geckos (family Eublepharidae) include both species with temperature-dependent sex determination and species where genotypic sex determination (GSD) was suggested based on the observation of equal sex ratios at several incubation temperatures. In this study, we present data on karyotypes and chromosomal characteristics in 12 species (Aeluroscalabotes felinus, Coleonyx brevis, Coleonyx elegans, Coleonyx variegatus, Eublepharis angramainyu, Eublepharis macularius, Goniurosaurus araneus, Goniurosaurus lichtenfelderi, Goniurosaurus luii, Goniurosaurus splendens, Hemitheconyx caudicinctus, and Holodactylus africanus) covering all genera of the family, and search for the presence of heteromorphic sex chromosomes. Phylogenetic mapping of chromosomal changes showed a long evolutionary stasis of karyotypes with all acrocentric chromosomes followed by numerous chromosomal rearrangements in the ancestors of two lineages. We have found heteromorphic sex chromosomes in only one species, which suggests that sex chromosomes in most GSD species of the eyelid geckos are not morphologically differentiated. The sexual difference in karyotype was detected only in C. elegans which has a multiple sex chromosome system (X(1)X(2)Y). The metacentric Y chromosome evolved most likely via centric fusion of two acrocentric chromosomes involving loss of interstitial telomeric sequences. We conclude that the eyelid geckos exhibit diversity in sex determination ranging from the absence of any sexual differences to heteromorphic sex chromosomes, which makes them an interesting system for exploring the evolutionary origin of sexually dimorphic genomes.

  8. High-density sex-specific linkage maps of a European tree frog (Hyla arborea) identify the sex chromosome without information on offspring sex

    PubMed Central

    Brelsford, A; Dufresnes, C; Perrin, N

    2016-01-01

    Identifying homology between sex chromosomes of different species is essential to understanding the evolution of sex determination. Here, we show that the identity of a homomorphic sex chromosome pair can be established using a linkage map, without information on offspring sex. By comparing sex-specific maps of the European tree frog Hyla arborea, we find that the sex chromosome (linkage group 1) shows a threefold difference in marker number between the male and female maps. In contrast, the number of markers on each autosome is similar between the two maps. We also find strongly conserved synteny between H. arborea and Xenopus tropicalis across 200 million years of evolution, suggesting that the rate of chromosomal rearrangement in anurans is low. Finally, we show that recombination in males is greatly reduced at the centers of large chromosomes, consistent with previous cytogenetic findings. Our research shows the importance of high-density linkage maps for studies of recombination, chromosomal rearrangement and the genetic architecture of ecologically or economically important traits. PMID:26374238

  9. Small but mighty: the evolutionary dynamics of W and Y sex chromosomes.

    PubMed

    Mank, Judith E

    2012-01-01

    Although sex chromosomes have been the focus of a great deal of scientific scrutiny, most interest has centred on understanding the evolution and relative importance of X and Z chromosomes. By contrast, the sex-limited W and Y chromosomes have received far less attention, both because of their generally degenerate nature and the difficulty in studying non-recombining and often highly heterochromatic genomic regions. However, recent theory and empirical evidence suggest that the W and Y chromosomes play a far more important role in sex-specific fitness traits than would be expected based on their size alone, and this importance may explain the persistence of some Y and W chromosomes in the face of powerful degradative forces. In addition to their role in fertility and fecundity, the sex-limited nature of these genomic regions results in unique evolutionary forces acting on Y and W chromosomes, implicating them as potentially major contributors to sexual selection and speciation. Recent empirical studies have borne out these predictions and revealed that some W and Y chromosomes play a vital role in key sex-specific evolutionary processes.

  10. The balanced lethal system of crested newts: a ghost of sex chromosomes past?

    PubMed

    Grossen, Christine; Neuenschwander, Samuel; Perrin, Nicolas

    2012-12-01

    Balanced lethal systems are more than biological curiosities: as theory predicts, they should quickly be eliminated through the joint forces of recombination and selection. That such systems might become fixed in natural populations poses a challenge to evolutionary theory. Here we address the case of a balanced lethal system fixed in crested newts and related species, which makes 50% of offspring die early in development. All adults are heteromorphic for chromosome pair 1. The two homologues (1A and 1B) have different recessive deleterious alleles fixed on a nonrecombining segment, so that heterozygotes are viable, while homozygotes are lethal. Given such a strong segregation load, how could autosomes stop recombining? We propose a role for a sex-chromosome turnover from pair 1 (putative ancestral sex chromosome) to pair 4 (currently active sex chromosome). Accordingly, 1A and 1B represent two variants (Y(A) and Y(B)) of the Y chromosome from an ancestral male-heterogametic system. We formalize a scenario in which turnovers are driven by sex ratio selection stemming from gene-environment interactions on sex determination. Individual-based simulations show that a balanced lethal system can be fixed with significant likelihood, provided the masculinizing allele on chromosome 4 appears after the elimination of the feminizing allele on chromosome 1. Our study illustrates how strikingly maladaptive traits might evolve through natural selection.

  11. Small but mighty: the evolutionary dynamics of W and Y sex chromosomes

    PubMed Central

    2012-01-01

    Although sex chromosomes have been the focus of a great deal of scientific scrutiny, most interest has centred on understanding the evolution and relative importance of X and Z chromosomes. By contrast, the sex-limited W and Y chromosomes have received far less attention, both because of their generally degenerate nature and the difficulty in studying non-recombining and often highly heterochromatic genomic regions. However, recent theory and empirical evidence suggest that the W and Y chromosomes play a far more important role in sex-specific fitness traits than would be expected based on their size alone, and this importance may explain the persistence of some Y and W chromosomes in the face of powerful degradative forces. In addition to their role in fertility and fecundity, the sex-limited nature of these genomic regions results in unique evolutionary forces acting on Y and W chromosomes, implicating them as potentially major contributors to sexual selection and speciation. Recent empirical studies have borne out these predictions and revealed that some W and Y chromosomes play a vital role in key sex-specific evolutionary processes. PMID:22038285

  12. Weird mammals provide insights into the evolution of mammalian sex chromosomes and dosage compensation.

    PubMed

    Graves, Jennifer A Marshall

    2015-12-01

    The deep divergence of mammalian groups 166 and 190 million years ago (MYA) provide genetic variation to explore the evolution of DNA sequence, gene arrangement and regulation of gene expression in mammals. With encouragement from the founder of the field, Mary Lyon, techniques in cytogenetics and molecular biology were progressively adapted to characterize the sex chromosomes of kangaroos and other marsupials, platypus and echidna-and weird rodent species. Comparative gene mapping reveals the process of sex chromosome evolution from their inception 190 MYA (they are autosomal in platypus) to their inevitable end (the Y has disappeared in two rodent lineages). Our X and Y are relatively young, getting their start with the evolution of the sex-determining SRY gene, which triggered progressive degradation of the Y chromosome. Even more recently, sex chromosomes of placental mammals fused with an autosomal region which now makes up most of the Y. Exploration of gene activity patterns over four decades showed that dosage compensation via X-chromosome inactivation is unique to therian mammals, and that this whole chromosome control process is different in marsupials and absent in monotremes and reptiles, and birds. These differences can be exploited to deduce how mammalian sex chromosomes and epigenetic silencing evolved.

  13. Comparative genetic mapping points to different sex chromosomes in sibling species of wild strawberry (Fragaria).

    PubMed

    Goldberg, Margot T; Spigler, Rachel B; Ashman, Tia-Lynn

    2010-12-01

    Separate sexes have evolved repeatedly from hermaphroditic ancestors in flowering plants, and thus select taxa can provide unparalleled insight into the evolutionary dynamics of sex chromosomes that are thought to be shared by plants and animals alike. Here we ask whether two octoploid sibling species of wild strawberry--one almost exclusively dioecious (males and females), Fragaria chiloensis, and one subdioecious (males, females, and hermaphrodites), F. virginiana--share the same sex-determining chromosome. We created a genetic map of the sex chromosome and its homeologs in F. chiloensis and assessed macrosynteny between it and published maps of the proto-sex chromosome of F. virginiana and the homeologous autosome of hermaphroditic diploid species. Segregation of male and female function in our F. chiloensis mapping population confirmed that linkage and dominance relations are similar to those in F. virginiana. However, identification of the molecular markers most tightly linked to the sex-determining locus in the two octoploid species shows that, in both, this region maps to homeologues of chromosome 6 in diploid congeners, but is located at opposite ends of their respective chromosomes.

  14. Transition in sexual system and sex chromosome evolution in the tadpole shrimp Triops cancriformis

    PubMed Central

    Mathers, T C; Hammond, R L; Jenner, R A; Hänfling, B; Atkins, J; Gómez, A

    2015-01-01

    Transitions in sexual system and reproductive mode may affect the course of sex chromosome evolution, for instance by altering the strength of sexually antagonistic selection. However, there have been few studies of sex chromosomes in systems where such transitions have been documented. The European tadpole shrimp, Triops cancriformis, has undergone a transition from dioecy to androdioecy (a sexual system where hermaphrodites and males coexist), offering an excellent opportunity to test the impact of this transition on the evolution of sex chromosomes. To identify sex-linked markers, to understand mechanisms of sex determination and to investigate differences between sexual systems, we carried out a genome-wide association study using restriction site-associated DNA sequencing (RAD-seq) of 47 males, females and hermaphrodites from one dioecious and one androdioecious population. We analysed 22.9 Gb of paired-end sequences and identified and scored >3000 high coverage novel genomic RAD markers. Presence–absence of markers, single-nucleotide polymorphism association and read depth identified 52 candidate sex-linked markers. We show that sex is genetically determined in T. cancriformis, with a ZW system conserved across dioecious and androdioecious populations and that hermaphrodites have likely evolved from females. We also show that the structure of the sex chromosomes differs strikingly, with a larger sex-linked region in the dioecious population compared with the androdioecious population. PMID:25757406

  15. Transition in sexual system and sex chromosome evolution in the tadpole shrimp Triops cancriformis.

    PubMed

    Mathers, T C; Hammond, R L; Jenner, R A; Hänfling, B; Atkins, J; Gómez, A

    2015-07-01

    Transitions in sexual system and reproductive mode may affect the course of sex chromosome evolution, for instance by altering the strength of sexually antagonistic selection. However, there have been few studies of sex chromosomes in systems where such transitions have been documented. The European tadpole shrimp, Triops cancriformis, has undergone a transition from dioecy to androdioecy (a sexual system where hermaphrodites and males coexist), offering an excellent opportunity to test the impact of this transition on the evolution of sex chromosomes. To identify sex-linked markers, to understand mechanisms of sex determination and to investigate differences between sexual systems, we carried out a genome-wide association study using restriction site-associated DNA sequencing (RAD-seq) of 47 males, females and hermaphrodites from one dioecious and one androdioecious population. We analysed 22.9 Gb of paired-end sequences and identified and scored >3000 high coverage novel genomic RAD markers. Presence-absence of markers, single-nucleotide polymorphism association and read depth identified 52 candidate sex-linked markers. We show that sex is genetically determined in T. cancriformis, with a ZW system conserved across dioecious and androdioecious populations and that hermaphrodites have likely evolved from females. We also show that the structure of the sex chromosomes differs strikingly, with a larger sex-linked region in the dioecious population compared with the androdioecious population.

  16. Deciphering neo-sex and B chromosome evolution by the draft genome of Drosophila albomicans

    PubMed Central

    2012-01-01

    Background Drosophila albomicans is a unique model organism for studying both sex chromosome and B chromosome evolution. A pair of its autosomes comprising roughly 40% of the whole genome has fused to the ancient X and Y chromosomes only about 0.12 million years ago, thereby creating the youngest and most gene-rich neo-sex system reported to date. This species also possesses recently derived B chromosomes that show non-Mendelian inheritance and significantly influence fertility. Methods We sequenced male flies with B chromosomes at 124.5-fold genome coverage using next-generation sequencing. To characterize neo-Y specific changes and B chromosome sequences, we also sequenced inbred female flies derived from the same strain but without B's at 28.5-fold. Results We assembled a female genome and placed 53% of the sequence and 85% of the annotated proteins into specific chromosomes, by comparison with the 12 Drosophila genomes. Despite its very recent origin, the non-recombining neo-Y chromosome shows various signs of degeneration, including a significant enrichment of non-functional genes compared to the neo-X, and an excess of tandem duplications relative to other chromosomes. We also characterized a B-chromosome linked scaffold that contains an actively transcribed unit and shows sequence similarity to the subcentromeric regions of both the ancient X and the neo-X chromosome. Conclusions Our results provide novel insights into the very early stages of sex chromosome evolution and B chromosome origination, and suggest an unprecedented connection between the births of these two systems in D. albomicans. PMID:22439699

  17. Rapid Karyotype Evolution in Lasiopodomys Involved at Least Two Autosome – Sex Chromosome Translocations

    PubMed Central

    Lemskaya, Natalya A.; Serdyukova, Natalya A.; O’Brien, Patricia C. M.; Kovalskaya, Julia M.; Smorkatcheva, Antonina V.; Golenishchev, Feodor N.; Perelman, Polina L.; Trifonov, Vladimir A.; Ferguson-Smith, Malcolm A.; Yang, Fengtang; Graphodatsky, Alexander S.

    2016-01-01

    The generic status of Lasiopodomys and its division into subgenera Lasiopodomys (L. mandarinus, L. brandtii) and Stenocranius (L. gregalis, L. raddei) are not generally accepted because of contradictions between the morphological and molecular data. To obtain cytogenetic evidence for the Lasiopodomys genus and its subgenera and to test the autosome to sex chromosome translocation hypothesis of sex chromosome complex origin in L. mandarinus proposed previously, we hybridized chromosome painting probes from the field vole (Microtus agrestis, MAG) and the Arctic lemming (Dicrostonyx torquatus, DTO) onto the metaphases of a female Mandarin vole (L. mandarinus, 2n = 47) and a male Brandt's vole (L. brandtii, 2n = 34). In addition, we hybridized Arctic lemming painting probes onto chromosomes of a female narrow-headed vole (L. gregalis, 2n = 36). Cross-species painting revealed three cytogenetic signatures (MAG12/18, 17a/19, and 22/24) that could validate the genus Lasiopodomys and indicate the evolutionary affinity of L. gregalis to the genus. Moreover, all three species retained the associations MAG1bc/17b and 2/8a detected previously in karyotypes of all arvicolins studied. The associations MAG2a/8a/19b, 8b/21, 9b/23, 11/13b, 12b/18, 17a/19a, and 5 fissions of ancestral segments appear to be characteristic for the subgenus Lasiopodomys. We also validated the autosome to sex chromosome translocation hypothesis on the origin of complex sex chromosomes in L. mandarinus. Two translocations of autosomes onto the ancestral X chromosome in L. mandarinus led to a complex of neo-X1, neo-X2, and neo-X3 elements. Our results demonstrate that genus Lasiopodomys represents a striking example of rapid chromosome evolution involving both autosomes and sex chromosomes. Multiple reshuffling events including Robertsonian fusions, chromosomal fissions, inversions and heterochromatin expansion have led to the formation of modern species karyotypes in a very short time, about 2.4 MY. PMID

  18. Curated eutherian third party data gene data sets

    PubMed Central

    Premzl, Marko

    2015-01-01

    The free available eutherian genomic sequence data sets advanced scientific field of genomics. Of note, future revisions of gene data sets were expected, due to incompleteness of public eutherian genomic sequence assemblies and potential genomic sequence errors. The eutherian comparative genomic analysis protocol was proposed as guidance in protection against potential genomic sequence errors in public eutherian genomic sequences. The protocol was applicable in updates of 7 major eutherian gene data sets, including 812 complete coding sequences deposited in European Nucleotide Archive as curated third party data gene data sets. PMID:26862561

  19. Comparative genomic analysis of eutherian interferon-γ-inducible GTPases.

    PubMed

    Premzl, Marko

    2012-11-01

    The interferon-γ-inducible GTPases, IFGGs, are intracellular proteins involved in immune response against pathogens. A comprehensive comparative genomic review and analysis of eutherian IFGGs was carried out using public genomic sequences. The 64 eutherian IFGG genes were examined in detail and annotated. The eutherian IFGG promoter types were first catalogued followed by a phylogenetic analysis of eutherian IFGGs, which described five major IFGG clusters. The patterns of differential gene expansions and protein regions that may regulate IFGG catalytic features suggested a new classification of eutherian IFGGs. This mini-review has also provided new tests of reliability of public genomic sequences as well as tests of protein molecular evolution.

  20. Untangling the Contributions of Sex-Specific Gene Regulation and X-Chromosome Dosage to Sex-Biased Gene Expression in Caenorhabditis elegans

    PubMed Central

    Kramer, Maxwell; Rao, Prashant; Ercan, Sevinc

    2016-01-01

    Dosage compensation mechanisms equalize the level of X chromosome expression between sexes. Yet the X chromosome is often enriched for genes exhibiting sex-biased, i.e., imbalanced expression. The relationship between X chromosome dosage compensation and sex-biased gene expression remains largely unexplored. Most studies determine sex-biased gene expression without distinguishing between contributions from X chromosome copy number (dose) and the animal’s sex. Here, we uncoupled X chromosome dose from sex-specific gene regulation in Caenorhabditis elegans to determine the effect of each on X expression. In early embryogenesis, when dosage compensation is not yet fully active, X chromosome dose drives the hermaphrodite-biased expression of many X-linked genes, including several genes that were shown to be responsible for hermaphrodite fate. A similar effect is seen in the C. elegans germline, where X chromosome dose contributes to higher hermaphrodite X expression, suggesting that lack of dosage compensation in the germline may have a role in supporting higher expression of X chromosomal genes with female-biased functions in the gonad. In the soma, dosage compensation effectively balances X expression between the sexes. As a result, somatic sex-biased expression is almost entirely due to sex-specific gene regulation. These results suggest that lack of dosage compensation in different tissues and developmental stages allow X chromosome copy number to contribute to sex-biased gene expression and function. PMID:27356611

  1. Untangling the Contributions of Sex-Specific Gene Regulation and X-Chromosome Dosage to Sex-Biased Gene Expression in Caenorhabditis elegans.

    PubMed

    Kramer, Maxwell; Rao, Prashant; Ercan, Sevinc

    2016-09-01

    Dosage compensation mechanisms equalize the level of X chromosome expression between sexes. Yet the X chromosome is often enriched for genes exhibiting sex-biased, i.e., imbalanced expression. The relationship between X chromosome dosage compensation and sex-biased gene expression remains largely unexplored. Most studies determine sex-biased gene expression without distinguishing between contributions from X chromosome copy number (dose) and the animal's sex. Here, we uncoupled X chromosome dose from sex-specific gene regulation in Caenorhabditis elegans to determine the effect of each on X expression. In early embryogenesis, when dosage compensation is not yet fully active, X chromosome dose drives the hermaphrodite-biased expression of many X-linked genes, including several genes that were shown to be responsible for hermaphrodite fate. A similar effect is seen in the C. elegans germline, where X chromosome dose contributes to higher hermaphrodite X expression, suggesting that lack of dosage compensation in the germline may have a role in supporting higher expression of X chromosomal genes with female-biased functions in the gonad. In the soma, dosage compensation effectively balances X expression between the sexes. As a result, somatic sex-biased expression is almost entirely due to sex-specific gene regulation. These results suggest that lack of dosage compensation in different tissues and developmental stages allow X chromosome copy number to contribute to sex-biased gene expression and function.

  2. Sex Chromosome Dosage Compensation in Heliconius Butterflies: Global yet Still Incomplete?

    PubMed

    Walters, James R; Hardcastle, Thomas J; Jiggins, Chris D

    2015-09-02

    The evolution of heterogametic sex chromosomes is often-but not always-accompanied by the evolution of dosage compensating mechanisms that mitigate the impact of sex-specific gene dosage on levels of gene expression. One emerging view of this process is that such mechanisms may only evolve in male-heterogametic (XY) species but not in female-heterogametic (ZW) species, which will consequently exhibit "incomplete" sex chromosome dosage compensation. However, recent results suggest that at least some Lepidoptera (moths and butterflies) may prove to be an exception to this prediction. Studies in bombycoid moths indicate the presence of a chromosome-wide epigenetic mechanism that effectively balances Z chromosome gene expression between the sexes by reducing Z-linked expression in males. In contrast, strong sex chromosome dosage effects without any reduction in male Z-linked expression were previously reported in a pyralid moth, suggesting a lack of any such dosage compensating mechanism. Here we report an analysis of sex chromosome dosage compensation in Heliconius butterflies, sampling multiple individuals for several different adult tissues (head, abdomen, leg, mouth, and antennae). Methodologically, we introduce a novel application of linear mixed-effects models to assess dosage compensation, offering a unified statistical framework that can estimate effects specific to chromosome, to sex, and their interactions (i.e., a dosage effect). Our results show substantially reduced Z-linked expression relative to autosomes in both sexes, as previously observed in bombycoid moths. This observation is consistent with an increasing body of evidence that some lepidopteran species possess an epigenetic dosage compensating mechanism that reduces Z chromosome expression in males to levels comparable with females. However, this mechanism appears to be imperfect in Heliconius, resulting in a modest dosage effect that produces an average 5-20% increase in male expression relative

  3. Sex Chromosome Dosage Compensation in Heliconius Butterflies: Global yet Still Incomplete?

    PubMed Central

    Walters, James R.; Hardcastle, Thomas J.; Jiggins, Chris D.

    2015-01-01

    The evolution of heterogametic sex chromosomes is often—but not always—accompanied by the evolution of dosage compensating mechanisms that mitigate the impact of sex-specific gene dosage on levels of gene expression. One emerging view of this process is that such mechanisms may only evolve in male-heterogametic (XY) species but not in female-heterogametic (ZW) species, which will consequently exhibit “incomplete” sex chromosome dosage compensation. However, recent results suggest that at least some Lepidoptera (moths and butterflies) may prove to be an exception to this prediction. Studies in bombycoid moths indicate the presence of a chromosome-wide epigenetic mechanism that effectively balances Z chromosome gene expression between the sexes by reducing Z-linked expression in males. In contrast, strong sex chromosome dosage effects without any reduction in male Z-linked expression were previously reported in a pyralid moth, suggesting a lack of any such dosage compensating mechanism. Here we report an analysis of sex chromosome dosage compensation in Heliconius butterflies, sampling multiple individuals for several different adult tissues (head, abdomen, leg, mouth, and antennae). Methodologically, we introduce a novel application of linear mixed-effects models to assess dosage compensation, offering a unified statistical framework that can estimate effects specific to chromosome, to sex, and their interactions (i.e., a dosage effect). Our results show substantially reduced Z-linked expression relative to autosomes in both sexes, as previously observed in bombycoid moths. This observation is consistent with an increasing body of evidence that some lepidopteran species possess an epigenetic dosage compensating mechanism that reduces Z chromosome expression in males to levels comparable with females. However, this mechanism appears to be imperfect in Heliconius, resulting in a modest dosage effect that produces an average 5–20% increase in male expression

  4. Amplification of microsatellite repeat motifs is associated with the evolutionary differentiation and heterochromatinization of sex chromosomes in Sauropsida.

    PubMed

    Matsubara, Kazumi; O'Meally, Denis; Azad, Bhumika; Georges, Arthur; Sarre, Stephen D; Graves, Jennifer A Marshall; Matsuda, Yoichi; Ezaz, Tariq

    2016-03-01

    The sex chromosomes in Sauropsida (reptiles and birds) have evolved independently many times. They show astonishing diversity in morphology ranging from cryptic to highly differentiated sex chromosomes with male (XX/XY) and female heterogamety (ZZ/ZW). Comparing such diverse sex chromosome systems thus provides unparalleled opportunities to capture evolution of morphologically differentiated sex chromosomes in action. Here, we describe chromosomal mapping of 18 microsatellite repeat motifs in eight species of Sauropsida. More than two microsatellite repeat motifs were amplified on the sex-specific chromosome, W or Y, in five species (Bassiana duperreyi, Aprasia parapulchella, Notechis scutatus, Chelodina longicollis, and Gallus gallus) of which the sex-specific chromosomes were heteromorphic and heterochromatic. Motifs (AAGG)n and (ATCC)n were amplified on the W chromosome of Pogona vitticeps and the Y chromosome of Emydura macquarii, respectively. By contrast, no motifs were amplified on the W chromosome of Christinus marmoratus, which is not much differentiated from the Z chromosome. Taken together with previously published studies, our results suggest that the amplification of microsatellite repeats is tightly associated with the differentiation and heterochromatinization of sex-specific chromosomes in sauropsids as well as in other taxa. Although some motifs were common between the sex-specific chromosomes of multiple species, no correlation was observed between this commonality and the species phylogeny. Furthermore, comparative analysis of sex chromosome homology and chromosomal distribution of microsatellite repeats between two closely related chelid turtles, C. longicollis and E. macquarii, identified different ancestry and differentiation history. These suggest multiple evolutions of sex chromosomes in the Sauropsida.

  5. Postzygotic isolation involves strong mitochondrial and sex-specific effects in Tigriopus californicus, a species lacking heteromorphic sex chromosomes.

    PubMed

    Foley, B R; Rose, C G; Rundle, D E; Leong, W; Edmands, S

    2013-11-01

    Detailed studies of the genetics of speciation have focused on a few model systems, particularly Drosophila. The copepod Tigriopus californicus offers an alternative that differs from standard animal models in that it lacks heteromorphic chromosomes (instead, sex determination is polygenic) and has reduced opportunities for sexual conflict, because females mate only once. Quantitative trait loci (QTL) mapping was conducted on reciprocal F2 hybrids between two strongly differentiated populations, using a saturated linkage map spanning all 12 autosomes and the mitochondrion. By comparing sexes, a possible sex ratio distorter was found but no sex chromosomes. Although studies of standard models often find an excess of hybrid male sterility factors, we found no QTL for sterility and multiple QTL for hybrid viability (indicated by non-Mendelian adult ratios) and other characters. Viability problems were found to be stronger in males, but the usual explanations for weaker hybrid males (sex chromosomes, sensitivity of spermatogenesis, sexual selection) cannot fully account for these male viability problems. Instead, higher metabolic rates may amplify deleterious effects in males. Although many studies of standard speciation models find the strongest genetic incompatibilities to be nuclear-nuclear (specifically X chromosome-autosome), we found the strongest deleterious interaction in this system was mito-nuclear. Consistent with the snowball theory of incompatibility accumulation, we found that trigenic interactions in this highly divergent cross were substantially more frequent (>6×) than digenic interactions. This alternative system thus allows important comparisons to studies of the genetics of reproductive isolation in more standard model systems.

  6. IDENTIFICATION OF SEX CHROMOSOME MOLECULAR MARKERS USING RAPDS AND FLUORESCENT IN SITU HYBRIDIZATION IN RAINBOW TROUT

    EPA Science Inventory

    The goal of this work is to identify molecular markers associated with the sex chromosomes in rainbow trout to study the mode of sex determination mechanisms in this species. Using the RAPD assay and bulked segregant analysis, two markers were identified that generated polymorphi...

  7. IDENTIFICATION OF SEX CHROMOSOME MOLECULAR MARKERS USING RAPDS AND FLUORESCENT IN SITU HYBRIDIZATION IN RAINBOW TROUT

    EPA Science Inventory

    The goal of this work is to identify molecular markers associated with the sex chromosomes in rainbow trout to study the mode of sex determination mechanisms in this species. Using the RAPD assay and bulked segregant analysis, two markers were identified that generated polymorphi...

  8. Male only progeny in Anastrepha suspensa by RNAi-induced sex reversion of chromosomal females

    USDA-ARS?s Scientific Manuscript database

    In Tephritidae sex determination is established by orthologs to the Drosophila melanogaster transformer and transformer-2 genes. In contrast, primary signals for sex determination are different in these species corresponding to the number of X chromosomes (XSE) in Drosophilidae species and to the pr...

  9. Comparative genetic mapping in Fragaria virginiana reveals autosomal origin of sex chromosome

    USDA-ARS?s Scientific Manuscript database

    Although most flowering plants are hermaphrodite, separate sexes (dioecy) have evolved repeatedly. The evolution of sex chromosomes from autosomes can often, but not always, accompany this transition. Thus, many have argued that plant genera that contain both hermaphroditic and dioecious members pro...

  10. Molecular Cytogenetic Characterization of the Dioecious Cannabis sativa with an XY Chromosome Sex Determination System

    PubMed Central

    Divashuk, Mikhail G.; Alexandrov, Oleg S.; Razumova, Olga V.; Kirov, Ilya V.; Karlov, Gennady I.

    2014-01-01

    Hemp (Cannabis sativa L.) was karyotyped using by DAPI/C-banding staining to provide chromosome measurements, and by fluorescence in situ hybridization with probes for 45 rDNA (pTa71), 5S rDNA (pCT4.2), a subtelomeric repeat (CS-1) and the Arabidopsis telomere probes. The karyotype has 18 autosomes plus a sex chromosome pair (XX in female and XY in male plants). The autosomes are difficult to distinguish morphologically, but three pairs could be distinguished using the probes. The Y chromosome is larger than the autosomes, and carries a fully heterochromatic DAPI positive arm and CS-1 repeats only on the less intensely DAPI-stained, euchromatic arm. The X is the largest chromosome of all, and carries CS-1 subtelomeric repeats on both arms. The meiotic configuration of the sex bivalent locates a pseudoautosomal region of the Y chromosome at the end of the euchromatic CS-1-carrying arm. Our molecular cytogenetic study of the C. sativa sex chromosomes is a starting point for helping to make C. sativa a promising model to study sex chromosome evolution. PMID:24465491

  11. Molecular cytogenetic characterization of the dioecious Cannabis sativa with an XY chromosome sex determination system.

    PubMed

    Divashuk, Mikhail G; Alexandrov, Oleg S; Razumova, Olga V; Kirov, Ilya V; Karlov, Gennady I

    2014-01-01

    Hemp (Cannabis sativa L.) was karyotyped using by DAPI/C-banding staining to provide chromosome measurements, and by fluorescence in situ hybridization with probes for 45 rDNA (pTa71), 5S rDNA (pCT4.2), a subtelomeric repeat (CS-1) and the Arabidopsis telomere probes. The karyotype has 18 autosomes plus a sex chromosome pair (XX in female and XY in male plants). The autosomes are difficult to distinguish morphologically, but three pairs could be distinguished using the probes. The Y chromosome is larger than the autosomes, and carries a fully heterochromatic DAPI positive arm and CS-1 repeats only on the less intensely DAPI-stained, euchromatic arm. The X is the largest chromosome of all, and carries CS-1 subtelomeric repeats on both arms. The meiotic configuration of the sex bivalent locates a pseudoautosomal region of the Y chromosome at the end of the euchromatic CS-1-carrying arm. Our molecular cytogenetic study of the C. sativa sex chromosomes is a starting point for helping to make C. sativa a promising model to study sex chromosome evolution.

  12. Association testing to detect gene-gene interactions on sex chromosomes in trio data.

    PubMed

    Lee, Yeonok; Ghosh, Debashis; Zhang, Yu

    2013-01-01

    Autism Spectrum Disorder (ASD) occurs more often among males than females in a 4:1 ratio. Among theories used to explain the causes of ASD, the X chromosome and the Y chromosome theories attribute ASD to the X-linked mutation and the male-limited gene expressions on the Y chromosome, respectively. Despite the rationale of the theory, studies have failed to attribute the sex-biased ratio to the significant linkage or association on the regions of interest on X chromosome. We further study the gender biased ratio by examining the possible interaction effects between two genes in the sex chromosomes. We propose a logistic regression model with mixed effects to detect gene-gene interactions on sex chromosomes. We investigated the power and type I error rates of the approach for a range of minor allele frequencies and varying linkage disequilibrium between markers and QTLs. We also evaluated the robustness of the model to population stratification. We applied the model to a trio-family data set with an ASD affected male child to study gene-gene interactions on sex chromosomes.

  13. Sex chromosome complement determines sex differences in aromatase expression and regulation in the stria terminalis and anterior amygdala of the developing mouse brain.

    PubMed

    Cisternas, Carla D; Tome, Karina; Caeiro, Ximena E; Dadam, Florencia M; Garcia-Segura, Luis M; Cambiasso, María J

    2015-10-15

    Aromatase, which converts testosterone in estradiol, is involved in the generation of brain sex dimorphisms. Here we used the "four core genotypes" mouse model, in which the effect of gonadal sex and sex chromosome complement is dissociated, to determine if sex chromosomes influence the expression of brain aromatase. The brain of 16 days old XY mouse embryos showed higher aromatase expression in the stria terminalis and the anterior amygdaloid area than the brain of XX embryos, independent of gonadal sex. Furthermore, estradiol or dihydrotestosterone increased aromatase expression in cultures of anterior amygdala neurons derived from XX embryos, but not in those derived from XY embryos. This effect was also independent of gonadal sex. The expression of other steroidogenic molecules, estrogen receptor-α and androgen receptor was not influenced by sex chromosomes. In conclusion, sex chromosomes determine sex dimorphisms in aromatase expression and regulation in the developing mouse brain.

  14. Triploid plover female provides support for a role of the W chromosome in avian sex determination

    PubMed Central

    Küpper, Clemens; Augustin, Jakob; Edwards, Scott; Székely, Tamás; Kosztolányi, András; Burke, Terry; Janes, Daniel E.

    2012-01-01

    Two models, Z Dosage and Dominant W, have been proposed to explain sex determination in birds, in which males are characterized by the presence of two Z chromosomes, and females are hemizygous with a Z and a W chromosome. According to the Z Dosage model, high dosage of a Z-linked gene triggers male development, whereas the Dominant W model postulates that a still unknown W-linked gene triggers female development. Using 33 polymorphic microsatellite markers, we describe a female triploid Kentish plover Charadrius alexandrinus identified by characteristic triallelic genotypes at 14 autosomal markers that produced viable diploid offspring. Chromatogram analysis showed that the sex chromosome composition of this female was ZZW. Together with two previously described ZZW female birds, our results suggest a prominent role for a female determining gene on the W chromosome. These results imply that avian sex determination is more dynamic and complex than currently envisioned. PMID:22647929

  15. Sex chromosome inactivation in germ cells: emerging roles of DNA damage response pathways.

    PubMed

    Ichijima, Yosuke; Sin, Ho-Su; Namekawa, Satoshi H

    2012-08-01

    Sex chromosome inactivation in male germ cells is a paradigm of epigenetic programming during sexual reproduction. Recent progress has revealed the underlying mechanisms of sex chromosome inactivation in male meiosis. The trigger of chromosome-wide silencing is activation of the DNA damage response (DDR) pathway, which is centered on the mediator of DNA damage checkpoint 1 (MDC1), a binding partner of phosphorylated histone H2AX (γH2AX). This DDR pathway shares features with the somatic DDR pathway recognizing DNA replication stress in the S phase. Additionally, it is likely to be distinct from the DDR pathway that recognizes meiosis-specific double-strand breaks. This review article extensively discusses the underlying mechanism of sex chromosome inactivation.

  16. A novel method for sex determination by detecting the number of X chromosomes.

    PubMed

    Nakanishi, Hiroaki; Shojo, Hideki; Ohmori, Takeshi; Hara, Masaaki; Takada, Aya; Adachi, Noboru; Saito, Kazuyuki

    2015-01-01

    A novel method for sex determination, based on the detection of the number of X chromosomes, was established. Current methods, based on the detection of the Y chromosome, can directly identify an unknown sample as male, but female gender is determined indirectly, by not detecting the Y chromosome. Thus, a direct determination of female gender is important because the quality (e.g., fragmentation and amelogenin-Y null allele) of the Y chromosome DNA may lead to a false result. Thus, we developed a novel sex determination method by analyzing the number of X chromosomes using a copy number variation (CNV) detection technique (the comparative Ct method). In this study, we designed a primer set using the amelogenin-X gene without the CNV region as the target to determine the X chromosome copy number, to exclude the influence of the CNV region from the comparative Ct value. The number of X chromosomes was determined statistically using the CopyCaller software with real-time PCR. All DNA samples from participants (20 males, 20 females) were evaluated correctly using this method with 1-ng template DNA. A minimum of 0.2-ng template DNA was found to be necessary for accurate sex determination with this method. When using ultraviolet-irradiated template DNA, as mock forensic samples, the sex of the samples could not be determined by short tandem repeat (STR) analysis but was correctly determined using our method. Thus, we successfully developed a method of sex determination based on the number of X chromosomes. Our novel method will be useful in forensic practice for sex determination.

  17. Nucleolus and chromosome relationships at pachynema in four Scarabaeoidea (Coleoptera) species with various combinations of NOR and sex chromosomes.

    PubMed

    Dutrillaux, A M; Xie, H; Dutrillaux, B

    2007-01-01

    Nucleolus organizer regions (NORs) and nucleolus locations were studied after silver staining in spermatocytes at pachynema from four beetle species selected for their various combinations of sex chromosomes. Their karyotypic formulae were: 18,neoXY (Dorcus parallelipipedus); 25,X (Passalus unicornis) and 20,Xyp (Cetonia aurata and Protaecia (Potosia) opaca). NORs were located in the short arms of a unique acrocentric autosome pair in the first three and in intercalary position in a sub-metacentric autosome pair in the last species. Silver staining gave remarkably more consistent results in pachytene than in mitotic spreads, enabling the detection of both NORs and nucleoli, and also better results in embryo than in spermatogonial metaphases. At pachynema the NORs were elongated, roughly in proportion to the number of nucleoli, which always remained associated with NOR. Nucleoli were not recurrently associated with sex chromosomes, except in P. unicornis, at late pachynema. In C. aurata and P. opaca the sex body was recurrently associated with acrocentric short arms and metacentric telomeres, respectively. Even in these simple situations, with NORs located in a single autosome pair, the number of nucleoli and their relationships with sex chromosomes varied strongly from species to species. These variations appear to be largely determined by the chromosome rearrangements which have occurred during evolution, which makes extrapolations and generalizations quite hazardous. In D. parallelipipedus pachytene cells a quasi-systematic and transient fusion between the terminal heterochromatin of two sub-metacentrics was detected. Other chromosome bivalents could also be occasionally associated, but not the NOR carrier one. A strong enhancement of DAPI or quinacrine mustard staining was observed at the fusion point.

  18. [Diagnosis of sex chromosome abnormality by fluorescence in-situ hybridization].

    PubMed

    Huang, Y; Sun, X; Li, Q

    1999-02-01

    To evaluate the diagnostic value of fluorescence in-situ hybridization (FISH) in sex chromosome abnormality. alpha-satellits DNA probes of X, Y chromosomes were used to FISH with blood samples from 19 patients with primary anemia or of gonad dysplasia. Five infertile men who were detected abnormal by G-banding analysis during metaphase and interphase. Samples from healthy men and women were used as positive controls and reactions with hybridization fluid without probes as negative controls. The karyotypes, 45, X; 45, X/46, XX/47, XXX; 45, X/46, XY; 47, XXY; 45, X/46, XXX were detected by FISH. Others were not detected by G banding such as 45, X/46, X,r? 46, X,r? but were found to be 45, X/46, X,r(X), 46, X, r(X), by FISH technique, confirming to be X ring chromosome. A female patient whose karyotype was 45, X/46, X, mar. by G banding. But G banding technique could not analyze the property of the marker and FISH revealed the marker was dici(yq), that is dicentric chromosome Y with two long arms of equal length. The real karyotype was 45, X/46, X, dici(yq) mosaicism. It belonged to Y chromosome abnormal and gonadal dysplasia syndrome. FISH can help to detect those chromosome abnormalities which can not be confirmed by traditional cytogenetics. It is of value in studying the complex chromosome mutation such as sex chromosome abnormality, unknown little marker, ring chromosome, mosaiciasm and translocation.

  19. Genomes of Ellobius species provide insight into the evolutionary dynamics of mammalian sex chromosomes

    PubMed Central

    Mulugeta, Eskeatnaf; Wassenaar, Evelyne; Sleddens-Linkels, Esther; van IJcken, Wilfred F.J.; Heard, Edith; Grootegoed, J. Anton; Just, Walter; Gribnau, Joost; Baarends, Willy M.

    2016-01-01

    The X and Y sex chromosomes of placental mammals show hallmarks of a tumultuous evolutionary past. The X Chromosome has a rich and conserved gene content, while the Y Chromosome has lost most of its genes. In the Transcaucasian mole vole Ellobius lutescens, the Y Chromosome including Sry has been lost, and both females and males have a 17,X diploid karyotype. Similarly, the closely related Ellobius talpinus, has a 54,XX karyotype in both females and males. Here, we report the sequencing and assembly of the E. lutescens and E. talpinus genomes. The results indicate that the loss of the Y Chromosome in E. lutescens and E. talpinus occurred in two independent events. Four functional homologs of mouse Y-Chromosomal genes were detected in both female and male E. lutescens, of which three were also detected in the E. talpinus genome. One of these is Eif2s3y, known as the only Y-derived gene that is crucial for successful male meiosis. Female and male E. lutescens can carry one and the same X Chromosome with a largely conserved gene content, including all genes known to function in X Chromosome inactivation. The availability of the genomes of these mole vole species provides unique models to study the dynamics of sex chromosome evolution. PMID:27510564

  20. Flow sorting of the Y sex chromosome in the dioecious plant Melandrium album

    SciTech Connect

    Veuskens, J.; Jacobs, M.; Negrutiu, I.

    1995-12-01

    The preparation of stable chromosome suspensions and flow cytometric sorting of both the Y sex chromosome of the white campion, Melandrium album, and the deleted Y chromosome of an asexual mutant, 5K63, is described. The principle has been to maintain transformed roots in vitro, synchronize and block mitosis, reduce cells to protoplasts, and lyse these to release chromosomes. Such in vitro material, unlike many cell suspensions, showed a stable karyotype. Factors critical to producing high-quality chromosome suspensions from protoplasts include osmolality of isolation solutions and choice of spindle toxin and of lysis buffer. Agrobacterium rhizogenes transformed young growing root cultures were synchronized at G1/S with 50 {mu}M aphidicolin for 24 h and released to a mitotic block with 30 {mu}M oryzalin for 11 h. Protoplast preparations from such tissue routinely had metaphase indices reaching 15%. Suspensions of intact metaphase chromosomes, with few chromatids, were obtained by lysing swollen mitotic protoplasts in a citric acid/disodium phosphate buffer. Except for the presence of clumps of autosomal chromosomes near the X and Y chromosome zones, monoparametric histograms of fluorescence intensities of suspensions stained with 4{prime},6-diamidino-2-phenylindole showed profiles similar to theoretical flow karyotypes. Two types of Y chromosomes, one full-length and one partially deleted (from the asexual mutant), could be sorted at 90% purity (21-fold enrichment of Y). These results are discussed in the context of sex determination and differentiation in higher plants. 45 refs., 6 figs., 2 tabs.

  1. Reduced representation genome sequencing suggests low diversity on the sex chromosomes of tonkean macaque monkeys.

    PubMed

    Evans, Ben J; Zeng, Kai; Esselstyn, Jacob A; Charlesworth, Brian; Melnick, Don J

    2014-09-01

    In species with separate sexes, social systems can differ in the relative variances of male versus female reproductive success. Papionin monkeys (macaques, mangabeys, mandrills, drills, baboons, and geladas) exhibit hallmarks of a high variance in male reproductive success, including a female-biased adult sex ratio and prominent sexual dimorphism. To explore the potential genomic consequences of such sex differences, we used a reduced representation genome sequencing approach to quantifying polymorphism at sites on autosomes and sex chromosomes of the tonkean macaque (Macaca tonkeana), a species endemic to the Indonesian island of Sulawesi. The ratio of nucleotide diversity of the X chromosome to that of the autosomes was less than the value (0.75) expected with a 1:1 sex ratio and no sex differences in the variance in reproductive success. However, the significance of this difference was dependent on which outgroup was used to standardize diversity levels. Using a new model that includes the effects of varying population size, sex differences in mutation rate between the autosomes and X chromosome, and GC-biased gene conversion (gBGC) or selection on GC content, we found that the maximum-likelihood estimate of the ratio of effective population size of the X chromosome to that of the autosomes was 0.68, which did not differ significantly from 0.75. We also found evidence for 1) a higher level of purifying selection on genic than nongenic regions, 2) gBGC or natural selection favoring increased GC content, 3) a dynamic demography characterized by population growth and contraction, 4) a higher mutation rate in males than females, and 5) a very low polymorphism level on the Y chromosome. These findings shed light on the population genomic consequences of sex differences in the variance in reproductive success, which appear to be modest in the tonkean macaque; they also suggest the occurrence of hitchhiking on the Y chromosome.

  2. An Optimized Method for Accurate Fetal Sex Prediction and Sex Chromosome Aneuploidy Detection in Non-Invasive Prenatal Testing

    PubMed Central

    Li, Haibo; Ding, Jie; Wen, Ping; Zhang, Qin; Xiang, Jingjing; Li, Qiong; Xuan, Liming; Kong, Lingyin; Mao, Yan; Zhu, Yijun; Shen, Jingjing; Liang, Bo; Li, Hong

    2016-01-01

    Massively parallel sequencing (MPS) combined with bioinformatic analysis has been widely applied to detect fetal chromosomal aneuploidies such as trisomy 21, 18, 13 and sex chromosome aneuploidies (SCAs) by sequencing cell-free fetal DNA (cffDNA) from maternal plasma, so-called non-invasive prenatal testing (NIPT). However, many technical challenges, such as dependency on correct fetal sex prediction, large variations of chromosome Y measurement and high sensitivity to random reads mapping, may result in higher false negative rate (FNR) and false positive rate (FPR) in fetal sex prediction as well as in SCAs detection. Here, we developed an optimized method to improve the accuracy of the current method by filtering out randomly mapped reads in six specific regions of the Y chromosome. The method reduces the FNR and FPR of fetal sex prediction from nearly 1% to 0.01% and 0.06%, respectively and works robustly under conditions of low fetal DNA concentration (1%) in testing and simulation of 92 samples. The optimized method was further confirmed by large scale testing (1590 samples), suggesting that it is reliable and robust enough for clinical testing. PMID:27441628

  3. Chromatin structural changes around satellite repeats on the female sex chromosome in Schistosoma mansoni and their possible role in sex chromosome emergence

    PubMed Central

    2012-01-01

    Background In the leuphotrochozoan parasitic platyhelminth Schistosoma mansoni, male individuals are homogametic (ZZ) whereas females are heterogametic (ZW). To elucidate the mechanisms that led to the emergence of sex chromosomes, we compared the genomic sequence and the chromatin structure of male and female individuals. As for many eukaryotes, the lower estimate for the repeat content is 40%, with an unknown proportion of domesticated repeats. We used massive sequencing to de novo assemble all repeats, and identify unambiguously Z-specific, W-specific and pseudoautosomal regions of the S. mansoni sex chromosomes. Results We show that 70 to 90% of S. mansoni W and Z are pseudoautosomal. No female-specific gene could be identified. Instead, the W-specific region is composed almost entirely of 36 satellite repeat families, of which 33 were previously unknown. Transcription and chromatin status of female-specific repeats are stage-specific: for those repeats that are transcribed, transcription is restricted to the larval stages lacking sexual dimorphism. In contrast, in the sexually dimorphic adult stage of the life cycle, no transcription occurs. In addition, the euchromatic character of histone modifications around the W-specific repeats decreases during the life cycle. Recombination repression occurs in this region even if homologous sequences are present on both the Z and W chromosomes. Conclusion Our study provides for the first time evidence for the hypothesis that, at least in organisms with a ZW type of sex chromosomes, repeat-induced chromatin structure changes could indeed be the initial event in sex chromosome emergence. PMID:22377319

  4. Dgcr8 and Dicer are essential for sex chromosome integrity during meiosis in males.

    PubMed

    Modzelewski, Andrew J; Hilz, Stephanie; Crate, Elizabeth A; Schweidenback, Caterina T H; Fogarty, Elizabeth A; Grenier, Jennifer K; Freire, Raimundo; Cohen, Paula E; Grimson, Andrew

    2015-06-15

    Small RNAs play crucial roles in regulating gene expression during mammalian meiosis. To investigate the function of microRNAs (miRNAs) and small interfering RNAs (siRNAs) during meiosis in males, we generated germ-cell-specific conditional deletions of Dgcr8 and Dicer in mice. Analysis of spermatocytes from both conditional knockout lines revealed that there were frequent chromosomal fusions during meiosis, always involving one or both sex chromosomes. RNA sequencing indicates upregulation of Atm in spermatocytes from miRNA-deficient mice, and immunofluorescence imaging demonstrates an increased abundance of activated ATM kinase and mislocalization of phosphorylated MDC1, an ATM phosphorylation substrate. The Atm 3'UTR contains many potential microRNA target sites, and, notably, target sites for several miRNAs depleted in both conditional knockout mice were highly effective at promoting repression. RNF8, a telomere-associated protein whose localization is controlled by the MDC1-ATM kinase cascade, normally associates with the sex chromosomes during pachytene, but in both conditional knockouts redistributed to the autosomes. Taken together, these results suggest that Atm dysregulation in microRNA-deficient germ lines contributes to the redistribution of proteins involved in chromosomal stability from the sex chromosomes to the autosomes, resulting in sex chromosome fusions during meiotic prophase I.

  5. Dgcr8 and Dicer are essential for sex chromosome integrity during meiosis in males

    PubMed Central

    Modzelewski, Andrew J.; Hilz, Stephanie; Crate, Elizabeth A.; Schweidenback, Caterina T. H.; Fogarty, Elizabeth A.; Grenier, Jennifer K.; Freire, Raimundo; Cohen, Paula E.; Grimson, Andrew

    2015-01-01

    ABSTRACT Small RNAs play crucial roles in regulating gene expression during mammalian meiosis. To investigate the function of microRNAs (miRNAs) and small interfering RNAs (siRNAs) during meiosis in males, we generated germ-cell-specific conditional deletions of Dgcr8 and Dicer in mice. Analysis of spermatocytes from both conditional knockout lines revealed that there were frequent chromosomal fusions during meiosis, always involving one or both sex chromosomes. RNA sequencing indicates upregulation of Atm in spermatocytes from miRNA-deficient mice, and immunofluorescence imaging demonstrates an increased abundance of activated ATM kinase and mislocalization of phosphorylated MDC1, an ATM phosphorylation substrate. The Atm 3′UTR contains many potential microRNA target sites, and, notably, target sites for several miRNAs depleted in both conditional knockout mice were highly effective at promoting repression. RNF8, a telomere-associated protein whose localization is controlled by the MDC1–ATM kinase cascade, normally associates with the sex chromosomes during pachytene, but in both conditional knockouts redistributed to the autosomes. Taken together, these results suggest that Atm dysregulation in microRNA-deficient germ lines contributes to the redistribution of proteins involved in chromosomal stability from the sex chromosomes to the autosomes, resulting in sex chromosome fusions during meiotic prophase I. PMID:25934699

  6. Plasticity in the Meiotic Epigenetic Landscape of Sex Chromosomes in Caenorhabditis Species

    PubMed Central

    Larson, Braden J.; Van, Mike V.; Nakayama, Taylor; Engebrecht, JoAnne

    2016-01-01

    During meiosis in the heterogametic sex in some species, sex chromosomes undergo meiotic sex chromosome inactivation (MSCI), which results in acquisition of repressive chromatin and transcriptional silencing. In Caenorhabditis elegans, MSCI is mediated by MET-2 methyltransferase deposition of histone H3 lysine 9 dimethylation. Here we examined the meiotic chromatin landscape in germ lines of four Caenorhabditis species; C. remanei and C. brenneri represent ancestral gonochorism, while C. briggsae and C. elegans are two lineages that independently evolved hermaphroditism. While MSCI is conserved across all four species, repressive chromatin modifications are distinct and do not correlate with reproductive mode. In contrast to C. elegans and C. remanei germ cells where X chromosomes are enriched for histone H3 lysine 9 dimethylation, X chromosomes in C. briggsae and C. brenneri germ cells are enriched for histone H3 lysine 9 trimethylation. Inactivation of C. briggsae MET-2 resulted in germ-line X chromosome transcription and checkpoint activation. Further, both histone H3 lysine 9 di- and trimethylation were reduced in Cbr-met-2 mutant germ lines, suggesting that in contrast to C. elegans, H3 lysine 9 di- and trimethylation are interdependent. C. briggsae H3 lysine 9 trimethylation was redistributed in the presence of asynapsed chromosomes in a sex-specific manner in the related process of meiotic silencing of unsynapsed chromatin. However, these repressive marks did not influence X chromosome replication timing. Examination of additional Caenorhabditis species revealed diverse H3 lysine 9 methylation patterns on the X, suggesting that the sex chromosome epigenome evolves rapidly. PMID:27280692

  7. Plasticity in the Meiotic Epigenetic Landscape of Sex Chromosomes in Caenorhabditis Species.

    PubMed

    Larson, Braden J; Van, Mike V; Nakayama, Taylor; Engebrecht, JoAnne

    2016-08-01

    During meiosis in the heterogametic sex in some species, sex chromosomes undergo meiotic sex chromosome inactivation (MSCI), which results in acquisition of repressive chromatin and transcriptional silencing. In Caenorhabditis elegans, MSCI is mediated by MET-2 methyltransferase deposition of histone H3 lysine 9 dimethylation. Here we examined the meiotic chromatin landscape in germ lines of four Caenorhabditis species; C. remanei and C. brenneri represent ancestral gonochorism, while C. briggsae and C. elegans are two lineages that independently evolved hermaphroditism. While MSCI is conserved across all four species, repressive chromatin modifications are distinct and do not correlate with reproductive mode. In contrast to C. elegans and C. remanei germ cells where X chromosomes are enriched for histone H3 lysine 9 dimethylation, X chromosomes in C. briggsae and C. brenneri germ cells are enriched for histone H3 lysine 9 trimethylation. Inactivation of C. briggsae MET-2 resulted in germ-line X chromosome transcription and checkpoint activation. Further, both histone H3 lysine 9 di- and trimethylation were reduced in Cbr-met-2 mutant germ lines, suggesting that in contrast to C. elegans, H3 lysine 9 di- and trimethylation are interdependent. C. briggsae H3 lysine 9 trimethylation was redistributed in the presence of asynapsed chromosomes in a sex-specific manner in the related process of meiotic silencing of unsynapsed chromatin. However, these repressive marks did not influence X chromosome replication timing. Examination of additional Caenorhabditis species revealed diverse H3 lysine 9 methylation patterns on the X, suggesting that the sex chromosome epigenome evolves rapidly.

  8. Involvement of Synaptonemal Complex Proteins in Sex Chromosome Segregation during Marsupial Male Meiosis

    PubMed Central

    Page, Jesús; Viera, Alberto; Parra, María Teresa; de la Fuente, Roberto; Suja, José Ángel; Prieto, Ignacio; Barbero, José Luis; Rufas, Julio S; Berríos, Soledad; Fernández-Donoso, Raúl

    2006-01-01

    Marsupial sex chromosomes break the rule that recombination during first meiotic prophase is necessary to ensure reductional segregation during first meiotic division. It is widely accepted that in marsupials X and Y chromosomes do not share homologous regions, and during male first meiotic prophase the synaptonemal complex is absent between them. Although these sex chromosomes do not recombine, they segregate reductionally in anaphase I. We have investigated the nature of sex chromosome association in spermatocytes of the marsupial Thylamys elegans, in order to discern the mechanisms involved in ensuring their proper segregation. We focused on the localization of the axial/lateral element protein SCP3 and the cohesin subunit STAG3. Our results show that X and Y chromosomes never appear as univalents in metaphase I, but they remain associated until they orientate and segregate to opposite poles. However, they must not be tied by a chiasma since their separation precedes the release of the sister chromatid cohesion. Instead, we show they are associated by the dense plate, a SCP3-rich structure that is organized during the first meiotic prophase and that is still present at metaphase I. Surprisingly, the dense plate incorporates SCP1, the main protein of the central element of the synaptonemal complex, from diplotene until telophase I. Once sex chromosomes are under spindle tension, they move to opposite poles losing contact with the dense plate and undergoing early segregation. Thus, the segregation of the achiasmatic T. elegans sex chromosomes seems to be ensured by the presence in metaphase I of a synaptonemal complex-derived structure. This feature, unique among vertebrates, indicates that synaptonemal complex elements may play a role in chromosome segregation. PMID:16934004

  9. The origin of the non-recombining region of sex chromosomes in Carica and Vasconcellea.

    PubMed

    Wu, Xia; Wang, Jianping; Na, Jong-Kuk; Yu, Qingyi; Moore, Richard C; Zee, Francis; Huber, Steven C; Ming, Ray

    2010-09-01

    Carica and Vasconcellea are two closely related sister genera in the family Caricaceae, and were once classified as two sections under Carica. Sex chromosomes have been found in papaya and originated approximately 2-3 million years ago. The objectives of this study were to determine whether sex chromosomes have evolved in Vasconcellea. Six X/Y gene pairs were cloned, sequenced and analyzed from three dioecious, one trioecious and one monoecious species of Vasconcellea. The isolation of distinctive X and Y alleles in dioecious and trioecious species of Vasconcellea demonstrated that sex chromosomes have evolved in this genus. Phylogenetic analyses indicated a monophyletic relationship between the X/Y alleles of Carica and those of Vasconcellea. Distinctive clusters of X/Y alleles were documented in V. parviflora and V. pulchra for all available gene sequences, and in V. goudatinana and V. cardinamarcensis for some X/Y alleles. The X and Y alleles within each species shared most single nucleotide polymorphism haplotypes that differed from other species. Limited evidence of gene conversion was documented among the X/Y alleles of some species, but was not sufficient to cause the evolutionary patterns reported herein. The Carica and Vasconcellea sex chromosomes may have originated from the same autosomes bearing the X allelic form that still exist in the monoecious species V. monoica, and have evolved independently after the speciation event that separated Carica from Vasconcellea. Within Vasconcellea, sex chromosomes have evolved at the species level, at least for some species.

  10. Identification of Sex Chromosomes by Means of Comparative Genomic Hybridization in a Lizard, Eremias multiocellata.

    PubMed

    Wang, Cui; Tang, Xiaolong; Xin, Ying; Yue, Feng; Yan, Xuefeng; Liu, Bingbing; An, Bei; Wang, Xi; Chen, Qiang

    2015-04-01

    Eremias multiocellata is a viviparous lizard that is known to exhibit temperature-dependent sex determination (TSD). Conventional Giemsa staining under light microscope examination has identified the karyotype of this species to be 2 n=36 I+2 m, with no detectable heteromorphic sex chromosomes. However, a highly differentiated female-specific chromosome, W, which is homomorphic with the Z chromosome, is found in the present study by the high-resolution cytogenetic method of comparative genomic hybridization (CGH). The results show that E. multiocellata is a viviparous lizard with both TSD and ZW heterogametic sex chromosomes. Despite the fact that a different sex ratio of male offspring was found in two populations (separated by an altitude of 1400 m) in previous incubation experiments, we demonstrate, using genomic in situ hybridization (GISH), that there is no significant chromosomal loss or acquisition between the two populations. This suggests that temperature may play a more important role in lowland populations. These results most likely indicate that E. multiocellata is transitioning between the evolutionary processes of TSD and genotypic sex determination (GSD) systems, and also give clues to the effect of TSD versus GSD in this process.

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

    PubMed

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

    2002-01-01

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

  12. Detection of sex chromosomal aneuploidies X-X, Y-Y, and X-Y in human sperm using two-chromosome fluorescence in situ hybridization

    SciTech Connect

    Wyrobek, A.J.; Robbins, W.A. |; Pinkel, D.; Weier, H.U.; Mehraein, Y. |

    1994-10-15

    Sex chromosome aneuploidy is the most common numerical chromosomal abnormality in humans at birth and a substantial portion of these abnormalities involve paternal chromosomes. An efficient method is presented for using air-dried smears of human semen to detect the number of X and Y chromosomes in sperm chromatin using two-chromosome fluorescence in situ hybridization. Air-dried semen smears were pre-treated with dithiothreitol and 3,4-diiodosalicylate salt to decondense the sperm chromatin and then were hybridized with repetitive sequence DNA probes that had been generated by PCR and differentially labeled. Hybridizations with X and Y specific probes showed the expected ratio of 50%X:50%Y bearing sperm. Sperm carrying extra fluorescence domains representing disomy for the X or Y chromosomes occurred at frequencies of {approximately} 4 per 10,000 sperm each. Cells carrying both X and Y fluorescence domains occurred at a frequency of {approximately} 6/10,000. Thus, the overall frequency of sperm that carried an extra sex chromosome was 1.4/1,000. The frequencies of sperm carrying sex chromosome aneuploidies determined by hybridization did not differ statistically from those reported from the same laboratory using the human-sperm/hamster-egg cytogenetic technique. Multi-chromosome fluorescence in situ hybridization to sperm is a promising method for assessing sex-ratio alterations in human semen and for determining the fraction of sperm carrying sex or other chromosome aneuploidies which may be transmissible to offspring. 44 refs., 1 fig., 3 tabs.

  13. Neural Activation During Mental Rotation in Complete Androgen Insensitivity Syndrome: The Influence of Sex Hormones and Sex Chromosomes.

    PubMed

    van Hemmen, Judy; Veltman, Dick J; Hoekzema, Elseline; Cohen-Kettenis, Peggy T; Dessens, Arianne B; Bakker, Julie

    2016-03-01

    Sex hormones, androgens in particular, are hypothesized to play a key role in the sexual differentiation of the human brain. However, possible direct effects of the sex chromosomes, that is, XX or XY, have not been well studied in humans. Individuals with complete androgen insensitivity syndrome (CAIS), who have a 46,XY karyotype but a female phenotype due to a complete androgen resistance, enable us to study the separate effects of gonadal hormones versus sex chromosomes on neural sex differences. Therefore, in the present study, we compared 46,XY men (n = 30) and 46,XX women (n = 29) to 46,XY individuals with CAIS (n = 21) on a mental rotation task using functional magnetic resonance imaging. Previously reported sex differences in neural activation during mental rotation were replicated in the control groups, with control men showing more activation in the inferior parietal lobe than control women. Individuals with CAIS showed a female-like neural activation pattern in the parietal lobe, indicating feminization of the brain in CAIS. Furthermore, this first neuroimaging study in individuals with CAIS provides evidence that sex differences in regional brain function during mental rotation are most likely not directly driven by genetic sex, but rather reflect gonadal hormone exposure.

  14. Step-by-step evolution of neo-sex chromosomes in geographical populations of wild silkmoths, Samia cynthia ssp.

    PubMed Central

    Yoshido, A; Sahara, K; Marec, F; Matsuda, Y

    2011-01-01

    Geographical subspecies of wild silkmoths, Samia cynthia ssp. (Lepidoptera: Saturniidae), differ considerably in sex chromosome constitution owing to sex chromosome fusions with autosomes, which leads to variation in chromosome numbers. We cloned S. cynthia orthologues of 16 Bombyx mori genes and mapped them to chromosome spreads of S. cynthia subspecies by fluorescence in situ hybridization (FISH) to determine the origin of S. cynthia neo-sex chromosomes. FISH mapping revealed that the Z chromosome and chromosome 12 of B. mori correspond to the Z chromosome and an autosome (A1) of S. c. ricini (Vietnam population, 2n=27, Z0 in female moths), respectively. B. mori chromosome 11 corresponds partly to another autosome (A2) and partly to a chromosome carrying nucleolar organizer region (NOR) of this subspecies. The NOR chromosome of S. c. ricini is also partly homologous to B. mori chromosome 24. Furthermore, our results revealed that two A1 homologues each fused with the W and Z chromosomes in a common ancestor of both Japanese subspecies S. c. walkeri (Sapporo population, 2n=26, neo-Wneo-Z) and S. cynthia subsp. indet. (Nagano population, 2n=25, neo-WZ1Z2). One homologue, corresponding to the A2 autosome in S. c. ricini and S. c. walkeri, fused with the W chromosome in S. cynthia subsp. indet. Consequently, the other homologue became a Z2 chromosome. These results clearly showed a step-by-step evolution of the neo-sex chromosomes by repeated autosome–sex chromosome fusions. We suggest that the rearrangements of sex chromosomes may facilitate divergence of S. cynthia subspecies towards speciation. PMID:20668432

  15. Sex chromosome loss and aging: in situ hybridization studies on human interphase nuclei.

    PubMed Central

    Guttenbach, M; Koschorz, B; Bernthaler, U; Grimm, T; Schmid, M

    1995-01-01

    A total of 1,000 lymphocyte interphase nuclei per proband from 90 females and 138 males age 1 wk to 93 years were analyzed by in situ hybridization for loss of the X and Y chromosomes, respectively. Both sex chromosomes showed an age-dependent loss. In males, Y hypoploidy was very low up to age 15 years (0.05%) but continuously increased to a frequency of 1.34% in men age 76-80 years. In females, the baseline level for X chromosome loss is much higher than that seen for the Y chromosome in males. Even prepubertal females show a rate of X chromosome loss, on the order of 1.5%-2.5%, rising to approximately 4.5%-5% in women older than 75 years. Dividing the female probands into three biological age groups on the basis of sex hormone function (< 13 years, 13-51 years, and > 51 years), a significant correlation of X chromosome loss versus age could clearly be demonstrated in women beyond age 51 years. Females age 51-91 years showed monosomy X at a rate from 3.2% to 5.1%. In contrast to sex chromosomal loss, the frequency of autosomal monosomies does not change during the course of aging: Chromosome 1 and chromosome 17 monosomic cells were found with a constant incidence of 1.2% and 1%, respectively. These data also indicate that autosome loss in interphase nuclei is not a function of chromosome size. Images Figure 1 Figure 2 PMID:7485166

  16. The origin of an unusual sex chromosome constitution in Acomys sp. (Rodentia, Muridae) from Tanzania.

    PubMed

    Castiglia, Riccardo; Makundi, Rhodes; Corti, Marco

    2007-10-01

    This paper describes a case which presents an evident variation from the "standard" XX/XY sex chromosomal constitution in a rodent, Acomys sp. This species known to be found in three localities of East Africa has only recently been separated from A. spinosissimus, its closest relative. In our study, five specimens of Acomys sp. and eight specimens of A. spinosissimus were live-trapped in five localities. Comparisons between the two taxa assed by G-banding show a complete homology in the chromosomal shape and banding pattern for 29 pairs of chromosomes corresponding to the complete autosomal set of A. spinosissimus. However, while all the A. spinosissimus analysed have 2n = 60 and a XY-XX system, in Acomys sp. males and females constitute mosaics for sex chromosomes in the bone marrow cells. Females (2n = 59, 60) have an excess (97%) of aneuploid cells with one single giant X chromosome, and males (2n = 60, 61) show X0/XY cells occurring in somatic tissues and XY cells in the germinal lineage. In addition, an odd heterochromatic submetacentric chromosome was identified in all the cells examined in two males and a female of Acomys sp. Since this chromosome was not related to sex determination and it is not present in all the analysed specimens, it can be considered as a B chromosome. Finally, the in situ fluorescence hybridisation (FISH) with telomeric probes showed a very intense interstitial telomeric signal (ITS) at the medial part on the long heterochromatic arm of the X chromosome. This could be due to recent chromosomal rearrangement.

  17. Sex chromosome loss and aging: In situ hybridization studies on human interphase nuclei

    SciTech Connect

    Guttenbach, M.; Koschorz, B.; Bernthaler, U.

    1995-11-01

    A total of 1,000 lymphocyte interphase nuclei per proband from 90 females and 138 males age 1 wk to 93 years were analyzed by in situ hybridization for loss of the X and Y chromosomes, respectively. Both sex chromosomes showed an age-dependent loss. In males, Y hypoploidy was very low up to age 15 years (0.05%) but continuously increased to a frequency of 1.34% in men age 76-80 years. In females, the baseline level for X chromosome loss is much higher than that seen for the Y chromosome in males. Even prepubertal females show a rate of X chromosome loss on the order of 1.5%-2.5%, rising to {approximately}4.5%-5% in women older than 75 years. Dividing the female probands into three biological age groups on the basis of sex hormone function (<13 years, 13-51 years, and >51 years), a significant correlation of X chromosome loss versus age could clearly be demonstrated in women beyond age 51 years. Females age 51-91 years showed monosomy X at a rate from 3.2% to 5.1%. In contrast to sex chromosomal loss, the frequency of autosomal monosomies does not change during the course of aging: chromosome 1 and chromosome 17 monosomic cells were found with a constant incidence of 1.2% and 1%, respectively. These data also indicate that autosome loss in interphase nuclei is not a function of chromosome size. 34 refs., 5 figs., 6 tabs.

  18. Differentiation of the XY sex chromosomes in the fish Hoplias malabaricus (Characiformes, Erythrinidae): unusual accumulation of repetitive sequences on the X chromosome.

    PubMed

    Cioffi, M B; Martins, C; Vicari, M R; Rebordinos, L; Bertollo, L A C

    2010-01-01

    The wolf fish Hoplias malabaricus (Erythrinidae) presents a high karyotypic diversity, with 7 karyomorphs identified. Karyomorph A is characterized by 2n = 42 chromosomes, without morphologically differentiated sex chromosomes. Karyomorph B also has 2n = 42 chromosomes for both sexes, but differs by a distinct heteromorphic XX/XY sex chromosome system. The cytogenetic mapping of 5 classes of repetitive DNA indicated similarities between both karyomorphs and the probable derivation of the XY chromosomes from pair No. 21 of karyomorph A. These chromosomes appear to be homeologous since the distribution of (GATA)(n) sequences, 18S rDNA and 5SHindIII-DNA sites supports their potential relatedness. Our data indicate that the differentiation of the long arms of the X chromosome occurred by accumulation of heterochromatin and 18S rDNA cistrons from the ancestral homomorphic pair No. 21 present in karyomorph A. These findings are further supported by the distribution of the Cot-1 DNA fraction. In addition, while the 18S rDNA cistrons were maintained and amplified on the X chromosomes, they were lost in the Y chromosome. The X chromosome was a clearly preferred site for the accumulation of DNA repeats, representing an unusual example of an X clustering more repetitive sequences than the Y during sex chromosome differentiation in fish. Copyright 2010 S. Karger AG, Basel.

  19. Differentiated ZZ/ZW sex chromosomes in Apareiodon ibitiensis (Teleostei, Parodontidae): cytotaxonomy and biogeography.

    PubMed

    Bellafronte, E; Vicari, M R; Artoni, R F; Margarido, V P; Moreira-Filho, O

    2009-12-01

    Conventional and molecular chromosomal analyses were carried out on three populations of Apareiodon ibitiensis sampled from the hydrographic basins of the São Francisco River and Upper Paraná River (Brazil). The results reveal a conserved diploid number (2n = 54 chromosomes), a karyotype formula consisting of 50 m-sm + 4st and a ZZ/ZW sex chromosome system that has not been previously identified for the species. C-banding analysis with propidium iodide staining revealed centromeric and terminal bands located in the chromosomes of the specimens from the three populations and allowed the identification of heteromorphism of heterochromatin regions in the Z and W chromosomes. The number of 18S sites located through fluorescent in situ hybridization (FISH) varied between the populations of the São Francisco and Upper Paraná Rivers. The location of 5S rDNA sites proved comparable in one pair of metacentric chromosomes. Thus, the present study proposes a ZZ/ZW sex chromosome system for A. ibitiensis among the Parodontidae, and a hypothesis is presented regarding possible W chromosome differentiation stages in this species through DNA accumulation, showing geographical variations for this characteristic, possibly as a consequence of geographical reproductive isolation.

  20. Ancestral Chromatin Configuration Constrains Chromatin Evolution on Differentiating Sex Chromosomes in Drosophila.

    PubMed

    Zhou, Qi; Bachtrog, Doris

    2015-06-01

    Sex chromosomes evolve distinctive types of chromatin from a pair of ancestral autosomes that are usually euchromatic. In Drosophila, the dosage-compensated X becomes enriched for hyperactive chromatin in males (mediated by H4K16ac), while the Y chromosome acquires silencing heterochromatin (enriched for H3K9me2/3). Drosophila autosomes are typically mostly euchromatic but the small dot chromosome has evolved a heterochromatin-like milieu (enriched for H3K9me2/3) that permits the normal expression of dot-linked genes, but which is different from typical pericentric heterochromatin. In Drosophila busckii, the dot chromosomes have fused to the ancestral sex chromosomes, creating a pair of 'neo-sex' chromosomes. Here we collect genomic, transcriptomic and epigenomic data from D. busckii, to investigate the evolutionary trajectory of sex chromosomes from a largely heterochromatic ancestor. We show that the neo-sex chromosomes formed <1 million years ago, but nearly 60% of neo-Y linked genes have already become non-functional. Expression levels are generally lower for the neo-Y alleles relative to their neo-X homologs, and the silencing heterochromatin mark H3K9me2, but not H3K9me3, is significantly enriched on silenced neo-Y genes. Despite rampant neo-Y degeneration, we find that the neo-X is deficient for the canonical histone modification mark of dosage compensation (H4K16ac), relative to autosomes or the compensated ancestral X chromosome, possibly reflecting constraints imposed on evolving hyperactive chromatin in an originally heterochromatic environment. Yet, neo-X genes are transcriptionally more active in males, relative to females, suggesting the evolution of incipient dosage compensation on the neo-X. Our data show that Y degeneration proceeds quickly after sex chromosomes become established through genomic and epigenetic changes, and are consistent with the idea that the evolution of sex-linked chromatin is influenced by its ancestral configuration.

  1. Alteration of the sex determining system resulting from structural change of the sex chromosomes in the frog Rana rugosa.

    PubMed

    Ohtani, H; Miura, I; Hanada, H; Ichikawa, Y

    2000-02-15

    Rana rugosa in Japan is divided into four geographical races on the basis of the karyotype of the sex chromosomes: one in which heteromorphic sex chromosomes occur in the female sex (ZW/ZZ-system), another in which they are present in males (XX/XY-system), and the remaining two in which no heteromorphism is seen in either sex. The last two inherit the XX/XY sex determining system. Y and Z chromosomes in the former two are of the same karyotype as the no. 7 chromosomes seen in one of the latter two, whereas X and W are caused by two inversions that occurred in the original Xs (no. 7). In this study, we first attempted to detect the structural difference between the resulting X and W by examining their chiasma formation. The chiasma distribution between X and W was closely similar to that between two Xs, suggesting that the W and X are identical in structure. Regarding the change from XX/XY- to ZW/ZZ-system, the simplest explanation is that the putative female-determining gene(s) on the W grew functionally stronger by inversions. Next, we examined the sex of triploids having two Xs and one Z. The data showed that the triploids with two original Xs and a Z were all male, whereas most of those with two resulting Xs and a Z developed into females as expected. We speculated that the female-determining gene(s) on the resulting X grew mildly stronger functionally by position effect, whereas those on the W grew much stronger for some other reason (e.g., duplication). J. Exp. Zool. 286:313-319, 2000. Copyright 2000 Wiley-Liss, Inc.

  2. X chromosome dosage by quantitative fluorescent PCR and rapid prenatal diagnosis of sex chromosome aneuploidies.

    PubMed

    Cirigliano, Vincenzo; Ejarque, Maijo; Fuster, Carme; Adinolfi, Matteo

    2002-11-01

    During the past few years, rapid prenatal diagnosis of chromosome aneuploidies has been successfully achieved by quantitative fluorescent PCR (QF-PCR) amplification of chromosome-specific small tandem repeats (STR). This approach has proven to be very useful in clinical settings, since it allows the detection of major numerical disorders in a few hours after sampling. For the detection of Turner's syndrome (45,X), several highly polymorphic STR on the X chromosome are needed in order to reduce the likelihood that a normal female might be homozygous for all sequences and, consequently, that the test could fail to discriminate between samples retrieved from a Turner's and a normal female fetus. Here we report a new method for rapid and accurate detection of X chromosome copy number in prenatal samples that does not depend on STR heterozygosity. The test is based on QF-PCR amplification of the X-linked HPRT together with the autosomal D21S1411 used as internal control for quantification. In the course of this study, this assay allowed the prenatal diagnosis of a rare case of a normal female homozygous for four selected highly polymorphic X chromosome STR, as well as the assessment of the normal chromosome complement of a fetus homozygous for five chromosome 21 markers.

  3. Sex chromosomes and associated rDNA form a heterochromatic network in the polytene nuclei of Bactrocera oleae (Diptera: Tephritidae).

    PubMed

    Drosopoulou, Elena; Nakou, Ifigeneia; Síchová, Jindra; Kubíčková, Svatava; Marec, František; Mavragani-Tsipidou, Penelope

    2012-06-01

    The olive fruit fly, Bactrocera oleae, has a diploid set of 2n = 12 chromosomes including a pair of sex chromosomes, XX in females and XY in males, but polytene nuclei show only five polytene chromosomes, obviously formed by five autosome pairs. Here we examined the fate of the sex chromosomes in the polytene complements of this species using fluorescence in situ hybridization (FISH) with the X and Y chromosome-derived probes, prepared by laser microdissection of the respective chromosomes from mitotic metaphases. Specificity of the probes was verified by FISH in preparations of mitotic chromosomes. In polytene nuclei, both probes hybridized strongly to a granular heterochromatic network, indicating thus underreplication of the sex chromosomes. The X chromosome probe (in both female and male nuclei) highlighted most of the granular mass, whereas the Y chromosome probe (in male nuclei) identified a small compact body of this heterochromatic network. Additional hybridization signals of the X probe were observed in the centromeric region of polytene chromosome II and in the telomeres of six polytene arms. We also examined distribution of the major ribosomal DNA (rDNA) using FISH with an 18S rDNA probe in both mitotic and polytene chromosome complements of B. oleae. In mitotic metaphases, the probe hybridized exclusively to the sex chromosomes. The probe signals localized a discrete rDNA site at the end of the short arm of the X chromosome, whereas they appeared dispersed over the entire dot-like Y chromosome. In polytene nuclei, the rDNA was found associated with the heterochromatic network representing the sex chromosomes. Only in nuclei with preserved nucleolar structure, the probe signals were scattered in the restricted area of the nucleolus. Thus, our study clearly shows that the granular heterochromatic network of polytene nuclei in B. oleae is formed by the underreplicated sex chromosomes and associated rDNA.

  4. The Epigenome of Evolving Drosophila Neo-Sex Chromosomes: Dosage Compensation and Heterochromatin Formation

    PubMed Central

    Kaiser, Vera B.; Alekseyenko, Artyom A.; Gorchakov, Andrey A.; Bachtrog, Doris

    2013-01-01

    Sex chromosomes originated from autosomes but have evolved a highly specialized chromatin structure. Drosophila Y chromosomes are composed entirely of silent heterochromatin, while male X chromosomes have highly accessible chromatin and are hypertranscribed as a result of dosage compensation. Here, we dissect the molecular mechanisms and functional pressures driving heterochromatin formation and dosage compensation of the recently formed neo-sex chromosomes of Drosophila miranda. We show that the onset of heterochromatin formation on the neo-Y is triggered by an accumulation of repetitive DNA. The neo-X has evolved partial dosage compensation and we find that diverse mutational paths have been utilized to establish several dozen novel binding consensus motifs for the dosage compensation complex on the neo-X, including simple point mutations at pre-binding sites, insertion and deletion mutations, microsatellite expansions, or tandem amplification of weak binding sites. Spreading of these silencing or activating chromatin modifications to adjacent regions results in massive mis-expression of neo-sex linked genes, and little correspondence between functionality of genes and their silencing on the neo-Y or dosage compensation on the neo-X. Intriguingly, the genomic regions being targeted by the dosage compensation complex on the neo-X and those becoming heterochromatic on the neo-Y show little overlap, possibly reflecting different propensities along the ancestral chromosome that formed the sex chromosome to adopt active or repressive chromatin configurations. Our findings have broad implications for current models of sex chromosome evolution, and demonstrate how mechanistic constraints can limit evolutionary adaptations. Our study also highlights how evolution can follow predictable genetic trajectories, by repeatedly acquiring the same 21-bp consensus motif for recruitment of the dosage compensation complex, yet utilizing a diverse array of random mutational changes

  5. Maternal X chromosome copy number variations are associated with discordant fetal sex chromosome aneuploidies detected by noninvasive prenatal testing.

    PubMed

    Wang, Shaowei; Huang, Shuai; Ma, Linlin; Liang, Lin; Zhang, Junrong; Zhang, Jianguang; Cram, David S

    2015-04-15

    The sensitivity and specificity of noninvasive prenatal testing (NIPT) for detection of sex chromosome aneuploidies (SCAs) compared to common autosomal trisomies are significantly lower. We speculated that in addition to altered maternal X chromosome karyotype, maternal X chromosome copy number variations (CNVs) may also contribute to discordant NIPT SCA results. Clinical NIPT was performed for pregnant women at a single hospital. Copy number variation sequencing (CNV-Seq) was used to identify and quantitate the copy number of maternal X chromosome CNVs for each positive SCA pregnancy. Two out of 25 SCA positive NIPT samples had slightly abnormal ChrX/ChrY z-scores and were referred for invasive test confirmation. However, fetal karyotypes were found to be normal. CNV-Seq analysis of the maternal white blood cell DNA archived from the original two NIPT blood samples identified small CNVs spanning the STS gene, which is associated with X-linked ichthyosis. Correcting for the altered plasma levels of X chromosome DNA caused by the two CNVs and, taking into consideration the phenotypic consequences for X-linked disease, both fetuses were diagnosed as normal. Maternal DNA sequencing is recommended for all positive NIPT SCA results to avoid unnecessary referral for invasive testing and also to evaluate the risk to the fetus of X-linked disease. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Ancestral Chromatin Configuration Constrains Chromatin Evolution on Differentiating Sex Chromosomes in Drosophila

    PubMed Central

    Zhou, Qi; Bachtrog, Doris

    2015-01-01

    Sex chromosomes evolve distinctive types of chromatin from a pair of ancestral autosomes that are usually euchromatic. In Drosophila, the dosage-compensated X becomes enriched for hyperactive chromatin in males (mediated by H4K16ac), while the Y chromosome acquires silencing heterochromatin (enriched for H3K9me2/3). Drosophila autosomes are typically mostly euchromatic but the small dot chromosome has evolved a heterochromatin-like milieu (enriched for H3K9me2/3) that permits the normal expression of dot-linked genes, but which is different from typical pericentric heterochromatin. In Drosophila busckii, the dot chromosomes have fused to the ancestral sex chromosomes, creating a pair of ‘neo-sex’ chromosomes. Here we collect genomic, transcriptomic and epigenomic data from D. busckii, to investigate the evolutionary trajectory of sex chromosomes from a largely heterochromatic ancestor. We show that the neo-sex chromosomes formed <1 million years ago, but nearly 60% of neo-Y linked genes have already become non-functional. Expression levels are generally lower for the neo-Y alleles relative to their neo-X homologs, and the silencing heterochromatin mark H3K9me2, but not H3K9me3, is significantly enriched on silenced neo-Y genes. Despite rampant neo-Y degeneration, we find that the neo-X is deficient for the canonical histone modification mark of dosage compensation (H4K16ac), relative to autosomes or the compensated ancestral X chromosome, possibly reflecting constraints imposed on evolving hyperactive chromatin in an originally heterochromatic environment. Yet, neo-X genes are transcriptionally more active in males, relative to females, suggesting the evolution of incipient dosage compensation on the neo-X. Our data show that Y degeneration proceeds quickly after sex chromosomes become established through genomic and epigenetic changes, and are consistent with the idea that the evolution of sex-linked chromatin is influenced by its ancestral configuration. PMID

  7. Sex ratio in normal and disomic sperm: Evidence that the extra chromosome 21 preferentially segregates with the Y chromosome

    SciTech Connect

    Griffin, D.K.; Millie, E.A.; Hassold, T.J. |

    1996-11-01

    In humans, deviations from a 1:1 male:female ratio have been identified in both chromosomally normal and trisomic live births: among normal newborns there is a slight excess of males, among trisomy 18 live borns a large excess of females, and among trisomy 21 live borns an excess of males. These differences could arise from differential production of or fertilization by Y- or X-bearing sperm or from selection against male or female conceptions. To examine the proportion of Y- and X- bearing sperm in normal sperm and in sperm disomic for chromosomes 18 or 21, we used three-color FISH (to the X and Y and either chromosome 18 or chromosome 21) to analyze > 300,000 sperm from 24 men. In apparently normal sperm, the sex ratio was nearly 1:1 (148,074 Y-bearing to 148,657 X-bearing sperm), and the value was not affected by the age of the donor. Certain of the donors, however, had significant excesses of Y- or X-bearing sperm. In disomy 18 sperm, there were virtually identical numbers of Y- and X-bearing sperm; thus, the excess of females in trisomy 18 presumably is due to selection against male trisomic conceptions. In contrast, we observed 69 Y-bearing and 44 X-bearing sperm disomic for chromosome 21. This is consistent with previous molecular studies, which have identified an excess of males among paternally derived cases of trisomy 21, and suggests that some of the excess of males among Down syndrome individuals is attributable to a nondisjunctional mechanism in which the extra chromosome 21 preferentially segregates with the Y chromosome. 17 refs., 2 tabs.

  8. Assessment of fetal sex chromosome aneuploidy using directed cell-free DNA analysis.

    PubMed

    Nicolaides, Kypros H; Musci, Thomas J; Struble, Craig A; Syngelaki, Argyro; Gil, M M

    2014-01-01

    To examine the performance of chromosome-selective sequencing of cell-free (cf) DNA in maternal blood for assessment of fetal sex chromosome aneuploidies. This was a case-control study of 177 stored maternal plasma samples, obtained before fetal karyotyping at 11-13 weeks of gestation, from 59 singleton pregnancies with fetal sex chromosome aneuploidies (45,X, n = 49; 47,XXX, n = 6; 47,XXY, n = 1; 47,XYY, n = 3) and 118 with euploid fetuses (46,XY, n = 59; 46,XX, n = 59). Digital analysis of selected regions (DANSR™) on chromosomes 21, 18, 13, X and Y was performed and the fetal-fraction optimized risk of trisomy evaluation (FORTE™) algorithm was used to estimate the risk for non-disomic genotypes. Performance was calculated at a risk cut-off of 1:100. Analysis of cfDNA provided risk scores for 172 (97.2%) samples; 4 samples (45,X, n = 2; 46,XY, n = 1; 46,XX, n = 1) had an insufficient fetal cfDNA fraction for reliable testing and 1 case (47,XXX) failed laboratory quality control metrics. The classification was correct in 43 (91.5%) of 47 cases of 45,X, all 5 of 47,XXX, 1 of 47,XXY and 3 of 47,XYY. There were no false-positive results for monosomy X. Analysis of cfDNA by chromosome-selective sequencing can correctly classify fetal sex chromosome aneuploidy with reasonably high sensitivity. © 2013 S. Karger AG, Basel.

  9. Gender-specific gene expression in post-mortem human brain: localization to sex chromosomes.

    PubMed

    Vawter, Marquis P; Evans, Simon; Choudary, Prabhakara; Tomita, Hiroaki; Meador-Woodruff, Jim; Molnar, Margherita; Li, Jun; Lopez, Juan F; Myers, Rick; Cox, David; Watson, Stanley J; Akil, Huda; Jones, Edward G; Bunney, William E

    2004-02-01

    Gender differences in brain development and in the prevalence of neuropsychiatric disorders such as depression have been reported. Gender differences in human brain might be related to patterns of gene expression. Microarray technology is one useful method for investigation of gene expression in brain. We investigated gene expression, cell types, and regional expression patterns of differentially expressed sex chromosome genes in brain. We profiled gene expression in male and female dorsolateral prefrontal cortex, anterior cingulate cortex, and cerebellum using the Affymetrix oligonucleotide microarray platform. Differentially expressed genes between males and females on the Y chromosome (DBY, SMCY, UTY, RPS4Y, and USP9Y) and X chromosome (XIST) were confirmed using real-time PCR measurements. In situ hybridization confirmed the differential expression of gender-specific genes and neuronal expression of XIST, RPS4Y, SMCY, and UTY in three brain regions examined. The XIST gene, which silences gene expression on regions of the X chromosome, is expressed in a subset of neurons. Since a subset of neurons express gender-specific genes, neural subpopulations may exhibit a subtle sexual dimorphism at the level of differences in gene regulation and function. The distinctive pattern of neuronal expression of XIST, RPS4Y, SMCY, and UTY and other sex chromosome genes in neuronal subpopulations may possibly contribute to gender differences in prevalence noted for some neuropsychiatric disorders. Studies of the protein expression of these sex-chromosome-linked genes in brain tissue are required to address the functional consequences of the observed gene expression differences.

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

    PubMed

    Yoshido, A; Marec, F; Sahara, K

    2016-05-01

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

  11. Sex differences in chiasma distribution along two marked mouse chromosomes: differences in chiasma distribution as a reason for sex differences in recombination frequency.

    PubMed

    Gorlov, I P; Zhelezova, A I; Gorlova OYu

    1994-12-01

    Chiasma distributions along bivalents 1 and 14 in female and male mice were studied. It was shown that the average chiasma number in both chromosomes show no sex difference. There are however, significant sex differences in chiasma distribution along 1 and 14 chromosomes. In males there are two terminal chiasma peaks in chromosome 1 and one subtelomeric peak of chiasmata in chromosome 14. In females chiasma distributions are more even. According to genetic data, females produce more recombinants between loci of chromosome 1 than males do. By means of a computer simulation it was demonstrated that the differences in the average recombination frequency result from differences in chiasma distribution.

  12. Sex chromosome mosaicism in males carrying Y chromosome long arm deletions.

    PubMed

    Siffroi, J P; Le Bourhis, C; Krausz, C; Barbaux, S; Quintana-Murci, L; Kanafani, S; Rouba, H; Bujan, L; Bourrouillou, G; Seifer, I; Boucher, D; Fellous, M; McElreavey, K; Dadoune, J P

    2000-12-01

    Microdeletions of the long arm of the Y chromosome (Yq) are a common cause of male infertility. Since large structural rearrangements of the Y chromosome are commonly associated with a 45,XO/46,XY chromosomal mosaicism, we studied whether submicroscopic Yq deletions could also be associated with the development of 45,XO cell lines. We studied blood samples from 14 infertile men carrying a Yq microdeletion as revealed by polymerase chain reaction (PCR). Patients were divided into two groups: group 1 (n = 6), in which karyotype analysis demonstrated a 45,X/46,XY mosaicism, and group 2 (n = 8) with apparently a normal 46,XY karyotype. 45,XO cells were identified by fluorescence in-situ hybridization (FISH) using X and Y centromeric probes. Lymphocytes from 11 fertile men were studied as controls. In addition, sperm cells were studied in three oligozoospermic patients in group 2. Our results showed that large and submicroscopic Yq deletions were associated with significantly increased percentages of 45,XO cells in lymphocytes and of sperm cells nullisomic for gonosomes, especially for the Y chromosome. Moreover, two isodicentric Y chromosomes, classified as normal by cytogenetic methods, were detected. Therefore, Yq microdeletions may be associated with Y chromosomal instability leading to the formation of 45,XO cell lines.

  13. Differentiation of Z and W chromosomes revealed by replication banding and FISH mapping of sex-chromosome-linked DNA markers in the cassowary (Aves, Ratitae).

    PubMed

    Nishida-Umehara, C; Fujiwara, A; Ogawa, A; Mizuno, S; Abe, S; Yoshida, M C

    1999-01-01

    We identified sex chromosomes of the double-wattled cassowary (Casuarius casuarius) by a replication banding method. The acrocentric Z chromosome, the fifth largest pair in males and slightly smaller W chromosome show no sign of heterochromatinization and share a nearly identical banding pattern in the distal half of the long arm. These chromosomes were further characterized by FISH with three probes linked either to Z or W chromosome in most avian species examined thus far. Contrary to the situation in the chicken, we obtained positive signals with Z-specific ZOV3 and W-specific EEO.6 in the distal region of both Z and W chromosomes. However, IREBP signals localized to the proximal half of the Z chromosome were not detected on the W chromosome. Thus, structural rearrangements such as deletions and inversions might have been the initial step of W chromosome differentiation from an ancestral homomorphic pair in this species.

  14. Instability of Multiple Sex Chromosomes Systems in Fish: The Case of Erythrinus erythrinus (Bloch & Schneider, 1801) (Characiformes, Erythrinidae).

    PubMed

    Bueno, Vanessa; Moresco, Rafaela Maria; Konerat, Jocicléia Thums; Moreira-Filho, Orlando; Margarido, Vladimir Pavan

    2016-02-01

    The fish species Erythrinus erythrinus belongs to the family Erythrinidae (order Characiformes, superorder Teleostei) and is considered a species complex because of the considerable differences between the karyotypes of analyzed populations. Whereas some populations present a sex chromosome system with male heterogamety, others do not show differentiated sex chromosomes. In this article, two novel karyotypes of E. erythrinus with the occurrence of male and female heterogamety are described, and a discussion of the stability of multiple sex chromosome systems is provided. A possible cause for sex chromosomes instability is that the Robertsonian rearrangements that originated the multiple systems did not prevent recombination with ancestral chromosomes, which also did not pass through a heterochromatinization process, the opposite of what usually happens with simple systems, especially of the ZZ/ZW or XX/XY type. It is suggested that multiple sex chromosome systems would not act as an effective postzygotic barrier, especially when there are hybridization zones between distinct karyomorphs that bear and that do not bear sex chromosome systems, allowing the generation of hybrids. This finding is important both for the comprehension of sex chromosomes evolution in fish and for conservation biology since the contact between populations with and without multiple sex chromosomes may compromise the regional biodiversity.

  15. Whole-genome sequence of a flatfish provides insights into ZW sex chromosome evolution and adaptation to a benthic lifestyle.

    PubMed

    Chen, Songlin; Zhang, Guojie; Shao, Changwei; Huang, Quanfei; Liu, Geng; Zhang, Pei; Song, Wentao; An, Na; Chalopin, Domitille; Volff, Jean-Nicolas; Hong, Yunhan; Li, Qiye; Sha, Zhenxia; Zhou, Heling; Xie, Mingshu; Yu, Qiulin; Liu, Yang; Xiang, Hui; Wang, Na; Wu, Kui; Yang, Changgeng; Zhou, Qian; Liao, Xiaolin; Yang, Linfeng; Hu, Qiaomu; Zhang, Jilin; Meng, Liang; Jin, Lijun; Tian, Yongsheng; Lian, Jinmin; Yang, Jingfeng; Miao, Guidong; Liu, Shanshan; Liang, Zhuo; Yan, Fang; Li, Yangzhen; Sun, Bin; Zhang, Hong; Zhang, Jing; Zhu, Ying; Du, Min; Zhao, Yongwei; Schartl, Manfred; Tang, Qisheng; Wang, Jun

    2014-03-01

    Genetic sex determination by W and Z chromosomes has developed independently in different groups of organisms. To better understand the evolution of sex chromosomes and the plasticity of sex-determination mechanisms, we sequenced the whole genomes of a male (ZZ) and a female (ZW) half-smooth tongue sole (Cynoglossus semilaevis). In addition to insights into adaptation to a benthic lifestyle, we find that the sex chromosomes of these fish are derived from the same ancestral vertebrate protochromosome as the avian W and Z chromosomes. Notably, the same gene on the Z chromosome, dmrt1, which is the male-determining gene in birds, showed convergent evolution of features that are compatible with a similar function in tongue sole. Comparison of the relatively young tongue sole sex chromosomes with those of mammals and birds identified events that occurred during the early phase of sex-chromosome evolution. Pertinent to the current debate about heterogametic sex-chromosome decay, we find that massive gene loss occurred in the wake of sex-chromosome 'birth'.

  16. Sex chromosome differentiation and the W- and Z-specific loci in Xenopus laevis.

    PubMed

    Mawaribuchi, Shuuji; Takahashi, Shuji; Wada, Mikako; Uno, Yoshinobu; Matsuda, Yoichi; Kondo, Mariko; Fukui, Akimasa; Takamatsu, Nobuhiko; Taira, Masanori; Ito, Michihiko

    2017-06-15

    Genetic sex-determining systems in vertebrates include two basic types of heterogamety; XX (female)/XY (male) and ZZ (male)/ZW (female) types. The African clawed frog Xenopus laevis has a ZZ/ZW-type sex-determining system. In this species, we previously identified a W-specific sex (female)-determining gene dmw, and specified W and Z chromosomes, which could be morphologically indistinguishable (homomorphic). In addition to dmw, we most recently discovered two genes, named scanw and ccdc69w, and one gene, named capn5z in the W- and Z-specific regions, respectively. In this study, we revealed the detail structures of the W/Z-specific loci and genes. Sequence analysis indicated that there is almost no sequence similarity between 278kb W-specific and 83kb Z-specific sequences on chromosome 2Lq32-33, where both the transposable elements are abundant. Synteny and phylogenic analyses indicated that all the W/Z-specific genes might have emerged independently. Expression analysis demonstrated that scanw and ccdc69w or capn5z are expressed in early differentiating ZW gonads or testes, thereby suggesting possible roles in female or male development, respectively. Importantly, the sex-determining gene (SDG) dmw might have been generated after allotetraploidization, thereby indicating the construction of the new sex-determining system by dmw after species hybridization. Furthermore, by direct genotyping, we confirmed that diploid WW embryos developed into normal female frogs, which indicate that the Z-specific region is not essential for female development. Overall, these findings indicate that sex chromosome differentiation has started, although no heteromorphic sex chromosomes are evident yet, in X. laevis. Homologous recombination suppression might have promoted the accumulation of mutations and transposable elements, and enlarged the W/Z-specific regions, thereby resulting in differentiation of the W/Z chromosomes. Copyright © 2016 Elsevier Inc. All rights reserved.

  17. Meiotic sex chromosome inactivation in male mice with targeted disruptions of Xist.

    PubMed

    Turner, James M A; Mahadevaiah, Shantha K; Elliott, David J; Garchon, Henri-Jean; Pehrson, John R; Jaenisch, Rudolf; Burgoyne, Paul S

    2002-11-01

    X chromosome inactivation occurs twice during the life cycle of placental mammals. In normal females, one X chromosome in each cell is inactivated early in embryogenesis, while in the male, the X chromosome is inactivated together with the Y chromosome in spermatogenic cells shortly before or during early meiotic prophase. Inactivation of one X chromosome in somatic cells of females serves to equalise X-linked gene dosage between males and females, but the role of male meiotic sex chromosome inactivation (MSCI) is unknown. The inactive X-chromosome of somatic cells and male meiotic cells share similar properties such as late replication and enrichment for histone macroH2A1.2, suggesting a common mechanism of inactivation. This possibility is supported by the fact that Xist RNA that mediates somatic X-inactivation is expressed in the testis of male mice and humans. In the present study we show that both Xist RNA and Tsix RNA, an antisense RNA that controls Xist function in the soma, are expressed in the testis in a germ-cell-dependent manner. However, our finding that MSCI and sex-body formation are unaltered in mice with targeted mutations of Xist that prevent somatic X inactivation suggests that somatic X-inactivation and MSCI occur by fundamentally different mechanisms.

  18. 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

  19. 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.

  20. To Break or Not To Break: Sex Chromosome Hemizygosity During Meiosis in Caenorhabditis.

    PubMed

    Van, Mike V; Larson, Braden J; Engebrecht, JoAnne

    2016-11-01

    Meiotic recombination establishes connections between homologous chromosomes to promote segregation. Hemizygous regions of sex chromosomes have no homologous chromosome to recombine with, yet must be transmitted through meiosis. An extreme case of hemizygosity exists in the genus Caenorhabditis, where males have a single X chromosome that completely lacks a homologous partner. To determine whether similar strategies have evolved to accommodate hemizygosity of the X during male meiosis in Caenorhabditis with distinct modes of sexual reproduction, we examined induction and processing of meiotic double strand breaks (DSBs) in androdioecious (hermaphrodite/male) Caenorhabditis elegans and C. briggsae, and gonochoristic (female/male) C. remanei and C. brenneri Analysis of the recombinase RAD-51 suggests more meiotic DSBs are induced in gonochoristic vs. androdioecious species. However, in late prophase in all species, chromosome pairs are restructured into bivalents around a single axis, suggesting that the holocentric nature of Caenorhabditis chromosomes dictates a single crossover per bivalent regardless of the number of DSBs induced. Interestingly, RAD-51 foci were readily observed on the X chromosome of androdioecious male germ cells, while very few were detected in gonochoristic male germ cells. As in C. elegans, the X chromosome in C. briggsae male germ cells undergoes transient pseudosynapsis and flexibility in DSB repair pathway choice. In contrast, in C. remanei and C. brenneri male germ cells, the X chromosome does not undergo pseudosynapsis and appears refractory to SPO-11-induced breaks. Together our results suggest that distinct strategies have evolved to accommodate sex chromosome hemizygosity during meiosis in closely related Caenorhabditis species. Copyright © 2016 by the Genetics Society of America.

  1. Evolutionary dynamics of Anolis sex chromosomes revealed by sequencing of flow sorting-derived microchromosome-specific DNA.

    PubMed

    Kichigin, Ilya G; Giovannotti, Massimo; Makunin, Alex I; Ng, Bee L; Kabilov, Marsel R; Tupikin, Alexey E; Barucchi, Vincenzo Caputo; Splendiani, Andrea; Ruggeri, Paolo; Rens, Willem; O'Brien, Patricia C M; Ferguson-Smith, Malcolm A; Graphodatsky, Alexander S; Trifonov, Vladimir A

    2016-10-01

    Squamate reptiles show a striking diversity in modes of sex determination, including both genetic (XY or ZW) and temperature-dependent sex determination systems. The genomes of only a handful of species have been sequenced, analyzed and assembled including the genome of Anolis carolinensis. Despite a high genome coverage, only macrochromosomes of A. carolinensis were assembled whereas the content of most microchromosomes remained unclear. Most of the Anolis species have homomorphic XY sex chromosome system. However, some species have large heteromorphic XY chromosomes (e.g., A. sagrei) and even multiple sex chromosomes systems (e.g. A. pogus), that were shown to be derived from fusions of the ancestral XY with microautosomes. We applied next generation sequencing of flow sorting-derived chromosome-specific DNA pools to characterize the content and composition of microchromosomes in A. carolinensis and A. sagrei. Comparative analysis of sequenced chromosome-specific DNA pools revealed that the A. sagrei XY sex chromosomes contain regions homologous to several microautosomes of A. carolinensis. We suggest that the sex chromosomes of A. sagrei are derived by fusions of the ancestral sex chromosome with three microautosomes and subsequent loss of some genetic content on the Y chromosome.

  2. Lack of global meiotic sex chromosome inactivation, and paucity of tissue-specific gene expression on the Drosophila X chromosome

    PubMed Central

    2011-01-01

    Background Paucity of male-biased genes on the Drosophila X chromosome is a well-established phenomenon, thought to be specifically linked to the role of these genes in reproduction and/or their expression in the meiotic male germline. In particular, meiotic sex chromosome inactivation (MSCI) has been widely considered a driving force behind depletion of spermatocyte-biased X-linked genes in Drosophila by analogy with mammals, even though the existence of global MCSI in Drosophila has not been proven. Results Microarray-based study and qRT-PCR analyses show that the dynamics of gene expression during testis development are very similar between X-linked and autosomal genes, with both showing transcriptional activation concomitant with meiosis. However, the genes showing at least ten-fold expression bias toward testis are significantly underrepresented on the X chromosome. Intriguingly, the genes with similar expression bias toward tissues other than testis, even those not apparently associated with reproduction, are also strongly underrepresented on the X. Bioinformatics analysis shows that while tissue-specific genes often bind silencing-associated factors in embryonic and cultured cells, this trend is less prominent for the X-linked genes. Conclusions Our data show that the global meiotic inactivation of the X chromosome does not occur in Drosophila. Paucity of testis-biased genes on the X appears not to be linked to reproduction or germline-specific events, but rather reflects a general underrepresentation of tissue-biased genes on this chromosome. Our analyses suggest that the activation/repression switch mechanisms that probably orchestrate the highly-biased expression of tissue-specific genes are generally not efficient on the X chromosome. This effect, probably caused by dosage compensation counteracting repression of the X-linked genes, may be the cause of the exodus of highly tissue-biased genes to the autosomes. PMID:21542906

  3. Sex Chromosomes Regulate Nighttime Sleep Propensity during Recovery from Sleep Loss in Mice

    PubMed Central

    Pinckney, Lennisha; Paul, Ketema N.

    2013-01-01

    Sex differences in spontaneous sleep amount are largely dependent on reproductive hormones; however, in mice some sex differences in sleep amount during the active phase are preserved after gonadectomy and may be driven by non-hormonal factors. In this study, we sought to determine whether or not these sex differences are driven by sex chromosome complement. Mice from the four core genotype (FCG) mouse model, whose sex chromosome complement (XY, XX) is independent of phenotype (male or female), were implanted with electroencephalographic (EEG) and electromyographic (EMG) electrodes for the recording of sleep-wake states and underwent a 24-hr baseline recording followed by six hours of forced wakefulness. During baseline conditions in mice whose gonads remained intact, males had more total sleep and non-rapid eye movement sleep than females during the active phase. Gonadectomized FCG mice exhibited no sex differences in rest-phase sleep amount; however, during the mid-active-phase (nighttime), XX males had more spontaneous non-rapid eye movement (NREM) sleep than XX females. The XY mice did not exhibit sex differences in sleep amount. Following forced wakefulness there was a change in the factors regulating sleep. XY females slept more during their mid-active phase siestas than XX females and had higher NREM slow wave activity, a measure of sleep propensity. These findings suggest that the process that regulates sleep propensity is sex-linked, and that sleep amount and sleep propensity are regulated differently in males and females following sleep loss. PMID:23658713

  4. Co-segregation of sex chromosomes in the male black widow spider Latrodectus mactans (Araneae, Theridiidae).

    PubMed

    Ault, Jeffrey G; Felt, Kristen D; Doan, Ryan N; Nedo, Alexander O; Ellison, Cassondra A; Paliulis, Leocadia V

    2017-02-23

    During meiosis I, homologous chromosomes join together to form bivalents. Through trial and error, bivalents achieve stable bipolar orientations (attachments) on the spindle that eventually allow the segregation of homologous chromosomes to opposite poles. Bipolar orientations are stable through tension generated by poleward forces to opposite poles. Unipolar orientations lack tension and are stereotypically not stable. The behavior of sex chromosomes during meiosis I in the male black widow spider Latrodectus mactans (Araneae, Theridiidae) challenges the principles governing such a scenario. We found that male L. mactans has two distinct X chromosomes, X1 and X2. The X chromosomes join together to form a connection that is present in prometaphase I but is lost during metaphase I, before the autosomes disjoin at anaphase I. We found that both X chromosomes form stable unipolar orientations to the same pole that assure their co-segregation at anaphase I. Using micromanipulation, immunofluorescence microscopy, and electron microscopy, we studied this unusual chromosome behavior to explain how it may fit the current dogma of chromosome distribution during cell division.

  5. Molecular diagnostic testing for Klinefelter syndrome and other male sex chromosome aneuploidies

    PubMed Central

    2012-01-01

    Background Male sex chromosome aneuploidies are underdiagnosed despite concomitant physical and behavioral manifestations. Objective To develop a non-invasive, rapid and high-throughput molecular diagnostic assay for detection of male sex chromosome aneuploidies, including 47,XXY (Klinefelter), 47,XYY, 48,XXYY and 48,XXXY syndromes. Methods The assay utilizes three XYM and four XA markers to interrogate Y:X and X:autosome ratios, respectively. The seven markers were PCR amplified using genomic DNA isolated from a cohort of 323 males with aneuploid (n = 117) and 46,XY (n = 206) karyotypes. The resulting PCR products were subjected to Pyrosequencing, a quantitative DNA sequencing method. Results Receiver operator characteristic (ROC) curves were used to establish thresholds for the discrimination of aneuploid from normal samples. The XYM markers permitted the identification of 47,XXY, 48,XXXY and 47,XYY syndromes with 100% sensitivity and specificity in both purified DNA and buccal swab samples. The 48,XXYY karyotype was delineated by XA marker data from 46,XY; an X allele threshold of 43% also permitted detection of 48,XXYY with 100% sensitivity and specificity. Analysis of X chromosome-specific biallelic SNPs demonstrated that 43 of 45 individuals (96%) with 48,XXYY karyotype had two distinct X chromosomes, while 2 (4%) had a duplicate X, providing evidence that 48,XXYY may result from nondisjunction during early mitotic divisions of a 46,XY embryo. Conclusions Quantitative Pyrosequencing, with high-throughput potential, can detect male sex chromosome aneuploidies with 100% sensitivity. PMID:22524164

  6. Meiosis in holocentric chromosomes: orientation and segregation of an autosome and sex chromosomes in Triatoma infestans (Heteroptera).

    PubMed

    Pérez, R; Rufas, J S; Suja, J A; Page, J; Panzera, F

    2000-01-01

    The meiotic behaviour of the X chromosome and one autosomal pair of the heteropteran Triatoma infestans was analysed by means of C-banding plus DAPI staining. At first metaphase, the X univalent is oriented with its long axis parallel to the equatorial plate, which suggests a holocentric interaction with the spindle fibres. After this initial orientation, kinetic activity is restricted to one of both chromatid ends. The election of the active chromatid end is random and it is independent of the end selected in the sister chromatid. At second metaphase, the X and Y chromatids associate side by side forming a pseudobivalent. After that, the kinetic activity is again restricted to either of both chromosomal ends in a random fashion. At first metaphase, the fourth autosomal bivalent shows two alternative random orientations depending on the chromosome end showing kinetic activity (DAPI positive or opposite). At second metaphase, half bivalents are oriented with their long axis parallel to the equatorial plate. Three different segregation patterns are observed. The kinetic activity can be localised: (i) in the end with the DAPI signal (46.9%), (ii) in the opposite end (44.6%) or (iii) in one DAPI-positive end in one chromatid and in the opposite end in the other one (8.5%). The existence of the last pattern indicates that the same end can show kinetic activity during both meiotic divisions. Our results provide new information on the comparative meiotic behaviour of autosomes and sex chromosomes in holocentric systems.

  7. Chromosome banding in Amphibia. XXIX. The primitive XY/XX sex chromosomes of Hyla femoralis (Anura, Hylidae).

    PubMed

    Schmid, M; Steinlein, C

    2003-01-01

    The karyotype of the pine woods treefrog, Hyla femoralis, is characterized by primitive XY female/XX male sex chromosomes. The sole difference between the X and the Y is the presence of a nucleolus organizer region (NOR) in the X. Due to a deletion of the NOR in the Y, this chromosome is distinctly smaller than the X. Since no autosomal NORs exist in the karyotype of this species, the NOR deletion in the Y results in a sex-specific difference in the number of ribosomal RNA genes, with a female:male ratio of about 2:1. Interphase nuclei of male animals contain always one silver-stained nucleolus, whereas most nuclei of female specimens exhibit two nucleoli. This is in agreement with the absence of dosage compensation for sex-linked genes in amphibian cells. The consequences of the loss of about 50% of ribosomal RNA genes for the viability of male individuals and spermatogenesis are discussed. Copyright 2003 S. Karger AG, Basel

  8. Chromosome-wide nucleosome replacement and H3.3 incorporation during mammalian meiotic sex chromosome inactivation.

    PubMed

    van der Heijden, Godfried W; Derijck, Alwin A H A; Pósfai, Eszter; Giele, Maud; Pelczar, Pawel; Ramos, Liliana; Wansink, Derick G; van der Vlag, Johan; Peters, Antoine H F M; de Boer, Peter

    2007-02-01

    In mammalian males, the first meiotic prophase is characterized by formation of a separate chromatin domain called the sex body. In this domain, the X and Y chromosomes are partially synapsed and transcriptionally silenced, a process termed meiotic sex-chromosome inactivation (MSCI). Likewise, unsynapsed autosomal chromatin present during pachytene is also silenced (meiotic silencing of unsynapsed chromatin, MSUC). Although it is known that MSCI and MSUC are both dependent on histone H2A.X phosphorylation mediated by the kinase ATR, and cause repressive H3 Lys9 dimethylation, the mechanisms underlying silencing are largely unidentified. Here, we demonstrate an extensive replacement of nucleosomes within unsynapsed chromatin, depending on and initiated shortly after induction of MSCI and MSUC. Nucleosomal eviction results in the exclusive incorporation of the H3.3 variant, which to date has primarily been associated with transcriptional activity. Nucleosomal exchange causes loss and subsequent selective reacquisition of specific histone modifications. This process therefore provides a means for epigenetic reprogramming of sex chromatin presumably required for gene silencing in the male mammalian germ line.

  9. The origin of mitotic sex-chromosome association in the brush-tailed possum, Trichosurus vulpecula (marsupalia:phalangeridae).

    PubMed

    Stock, A D; Mengden, G A

    1982-01-01

    Nonrandom associations between the sex chromosomes of the brush-tailed possum, Trichosurus vulpecula, were found to be due to association of nucleolar organizer regions (NOR's) on the X and Y chromosomes. NOR association was also observed between an autosome and the X chromosome. These findings, based on silver staining, are in contrast to the report of MURRAY (1977), who observed sex-chromosome association in this animal and indicated that these nonrandom associations may reflect an association between heterochromatic regions during interphase. We observed only two pairs of NOR's per cell in this animal, one autosomal and one on the sex chromosomes, rather than the several such regions observed by MURRAY, who used an N-banding technique. We discuss the problem of nonhomologous chromosome association in mammalian cells as influenced by heterochromatin and NOR's and find little support for nonhomologous chromosome associations at mitotic metaphase due to heterochromatin association.

  10. Evidence that sex chromosome genes affect sexual differentiation of female sexual behavior.

    PubMed

    Grgurevic, Neza; Büdefeld, Tomaz; Spanic, Tanja; Tobet, Stuart A; Majdic, Gregor

    2012-05-01

    Female receptivity including the immobile hormone-dependent lordosis posture is essential for successful reproduction in rodents. It is well documented that lordosis is organized during the perinatal period when the actions of androgens decrease the males' ability to display this behavior in adulthood. Conversely the absence of androgens, and the presence of low levels of prepubertal estrogens, preserve circuitry that regulates this behavior in females. The current study set out to determine whether sex chromosomal genes are involved in the differentiation of this behavior. An agonadal mouse model was used to test this hypothesis. The SF-1 gene (Nr5a1) is required for development of gonads and adrenal glands, and knockout mice are consequently not exposed to endogenous gonadal steroids. Thus contributions of sex chromosome genes can be disassociated from the actions of estrogens. Use of this model reveals a direct genetic contribution from sex chromosomes in the display of lordosis and other female-typical sexual behavior patterns. It is likely that the concentrations of gonadal steroids present during normal male development modify the actions of sex chromosome genes on the potential to display female sexual behavior. Copyright © 2012 Elsevier Inc. All rights reserved.

  11. Accumulation of Y-specific satellite DNAs during the evolution of Rumex acetosa sex chromosomes.

    PubMed

    Mariotti, Beatrice; Manzano, Susana; Kejnovský, Eduard; Vyskot, Boris; Jamilena, Manuel

    2009-03-01

    The study of the molecular structure of young heteromorphic sex chromosomes of plants has shed light on the evolutionary forces that control the differentiation of the X and Y during the earlier stages of their evolution. We have used the model plant Rumex acetosa, a dioecious species with multiple sex chromosomes, 2n = 12 + XX female and 2n = 12 + XY(1)Y(2) male, to analyse the significance of repetitive DNA accumulation during the differentiation of the Y. A bulk segregant analysis (BSA) approach allowed us to identify and isolate random amplified polymorphic DNA (RAPD) markers linked to the sex chromosomes. From a total of 86 RAPD markers in the parents, 6 markers were found to be linked to the Ys and 1 to the X. Two of the Y-linked markers represent two AT-rich satellite DNAs (satDNAs), named RAYSII and RAYSIII, that share about 80% homology, as well as with RAYSI, another satDNA of R. acetosa. Fluorescent in situ hybridisation demonstrated that RAYSII is specific for Y(1), whilst RAYSIII is located in different clusters along Y(1) and Y(2). The two satDNAs were only detected in the genome of the dioecious species with XX/XY(1)Y(2) multiple sex chromosome systems in the subgenus Acetosa, but were absent from other dioecious species with an XX/XY system of the subgenera Acetosa or Acetosella, as well as in gynodioecious or hermaphrodite species of the subgenera Acetosa, Rumex and Platypodium. Phylogenetic analysis with different cloned monomers of RAYSII and RAYSIII from both R. acetosa and R. papillaris indicate that these two satDNAs are completely separated from each other, and from RAYSI, in both species. The three Y-specific satDNAs, however, evolved from an ancestral satDNA with repeating units of 120 bp, through intermediate satDNAs of 360 bp. The data therefore support the idea that Y-chromosome differentiation and heterochromatinisation in the Rumex species having a multiple sex chromosome system have occurred by different amplification events from a

  12. Unraveling the Sex Chromosome Heteromorphism of the Paradoxical Frog Pseudis tocantins.

    PubMed

    Gatto, Kaleb Pretto; Busin, Carmen Silvia; Lourenço, Luciana Bolsoni

    2016-01-01

    The paradoxical frog Pseudis tocantins is the only species in the Hylidae family with known heteromorphic Z and W sex chromosomes. The Z chromosome is metacentric and presents an interstitial nucleolar organizer region (NOR) on the long arm that is adjacent to a pericentromeric heterochromatic band. In contrast, the submetacentric W chromosome carries a pericentromeric NOR on the long arm, which is adjacent to a clearly evident heterochromatic band that is larger than the band found on the Z chromosome and justify the size difference observed between these chromosomes. Here, we provide evidence that the non-centromeric heterochromatic bands in Zq and Wq differ not only in size and location but also in composition, based on comparative genomic hybridization (CGH) and an analysis of the anuran PcP190 satellite DNA. The finding of PcP190 sequences in P. tocantins extends the presence of this satellite DNA, which was previously detected among Leptodactylidae and Hylodidae, suggesting that this family of repetitive DNA is even older than it was formerly considered. Seven groups of PcP190 sequences were recognized in the genome of P. tocantins. PcP190 probes mapped to the heterochromatic band in Wq, and a Southern blot analysis indicated the accumulation of PcP190 in the female genome of P. tocantins, which suggests the involvement of this satellite DNA in the evolution of the sex chromosomes of this species.

  13. Unraveling the Sex Chromosome Heteromorphism of the Paradoxical Frog Pseudis tocantins

    PubMed Central

    Gatto, Kaleb Pretto; Busin, Carmen Silvia; Lourenço, Luciana Bolsoni

    2016-01-01

    The paradoxical frog Pseudis tocantins is the only species in the Hylidae family with known heteromorphic Z and W sex chromosomes. The Z chromosome is metacentric and presents an interstitial nucleolar organizer region (NOR) on the long arm that is adjacent to a pericentromeric heterochromatic band. In contrast, the submetacentric W chromosome carries a pericentromeric NOR on the long arm, which is adjacent to a clearly evident heterochromatic band that is larger than the band found on the Z chromosome and justify the size difference observed between these chromosomes. Here, we provide evidence that the non-centromeric heterochromatic bands in Zq and Wq differ not only in size and location but also in composition, based on comparative genomic hybridization (CGH) and an analysis of the anuran PcP190 satellite DNA. The finding of PcP190 sequences in P. tocantins extends the presence of this satellite DNA, which was previously detected among Leptodactylidae and Hylodidae, suggesting that this family of repetitive DNA is even older than it was formerly considered. Seven groups of PcP190 sequences were recognized in the genome of P. tocantins. PcP190 probes mapped to the heterochromatic band in Wq, and a Southern blot analysis indicated the accumulation of PcP190 in the female genome of P. tocantins, which suggests the involvement of this satellite DNA in the evolution of the sex chromosomes of this species. PMID:27214234

  14. Association between venous leg ulcers and sex chromosome anomalies in men.

    PubMed

    Gattringer, Cornelia; Scheurecker, Christine; Höpfl, Reinhard; Müller, Hansgeorg

    2010-11-01

    We report here two cases of men, aged 46 and 23 years, with refractory chronic venous leg ulcers in association with sex chromosome aberrations: one with a 47,XXY/48,XXXY karyotype (Klinefelter syndrome) and the other with a 47,XYY karyotype (Jacob syndrome). In both patients, the occurrence of leg ulcers was the reason for seeking medical care; their medical history was other-wise unremarkable. Chromosomal analyses were performed due to the unusually young age for development of venous leg ulcers. The pathophysiology behind the occurrence of venous leg ulcers in patients with numerical aberrations of the sex chromosomes is incompletely understood. Involvement of elevated plasminogen activator inhibitor-1 levels in the pathogenesis of venous leg ulcers has been reported in patients with Klinefelter syndrome. Notably, our patient with 47,XXY/48,XXXY presented with androgen deficiency but normal plasminogen activator inhibitor-1 activity.

  15. Zfy genes are required for efficient meiotic sex chromosome inactivation (MSCI) in spermatocytes.

    PubMed

    Vernet, Nadège; Mahadevaiah, Shantha K; de Rooij, Dirk G; Burgoyne, Paul S; Ellis, Peter J I

    2016-10-13

    During spermatogenesis, germ cells that fail to synapse their chromosomes or fail to undergo meiotic sex chromosome inactivation (MSCI) are eliminated via apoptosis during mid-pachytene. Previous work showed that Y-linked genes Zfy1 and Zfy2 act as 'executioners' for this checkpoint, and that wrongful expression of either gene during pachytene triggers germ cell death. Here, we show that in mice, Zfy genes are also necessary for efficient MSCI and the sex chromosomes are not correctly silenced in Zfy-deficient spermatocytes. This unexpectedly reveals a triple role for Zfy at the mid-pachytene checkpoint in which Zfy genes first promote MSCI, then monitor its progress (since if MSCI is achieved, Zfy genes will be silenced), and finally execute cells with MSCI failure. This potentially constitutes a negative feedback loop governing this critical checkpoint mechanism.

  16. The multiple sex chromosomes of platypus and echidna are not completely identical and several share homology with the avian Z

    PubMed Central

    Rens, Willem; O'Brien, Patricia CM; Grützner, Frank; Clarke, Oliver; Graphodatskaya, Daria; Tsend-Ayush, Enkhjargal; Trifonov, Vladimir A; Skelton, Helen; Wallis, Mary C; Johnston, Steve; Veyrunes, Frederic; Graves, Jennifer AM; Ferguson-Smith, Malcolm A

    2007-01-01

    Background Sex-determining systems have evolved independently in vertebrates. Placental mammals and marsupials have an XY system, birds have a ZW system. Reptiles and amphibians have different systems, including temperature-dependent sex determination, and XY and ZW systems that differ in origin from birds and placental mammals. Monotremes diverged early in mammalian evolution, just after the mammalian clade diverged from the sauropsid clade. Our previous studies showed that male platypus has five X and five Y chromosomes, no SRY, and DMRT1 on an X chromosome. In order to investigate monotreme sex chromosome evolution, we performed a comparative study of platypus and echidna by chromosome painting and comparative gene mapping. Results Chromosome painting reveals a meiotic chain of nine sex chromosomes in the male echidna and establishes their order in the chain. Two of those differ from those in the platypus, three of the platypus sex chromosomes differ from those of the echidna and the order of several chromosomes is rearranged. Comparative gene mapping shows that, in addition to bird autosome regions, regions of bird Z chromosomes are homologous to regions in four platypus X chromosomes, that is, X1, X2, X3, X5, and in chromosome Y1. Conclusion Monotreme sex chromosomes are easiest to explain on the hypothesis that autosomes were added sequentially to the translocation chain, with the final additions after platypus and echidna divergence. Genome sequencing and contig anchoring show no homology yet between platypus and therian Xs; thus, monotremes have a unique XY sex chromosome system that shares some homology with the avian Z. PMID:18021405

  17. Postzygotic isolation involves strong mitochondrial and sex-specific effects in Tigriopus californicus, a species lacking heteromorphic sex chromosomes

    PubMed Central

    Foley, B R; Rose, C G; Rundle, D E; Leong, W; Edmands, S

    2013-01-01

    Detailed studies of the genetics of speciation have focused on