Aberrant chromosomal sex-determining mechanisms in mammals, with special reference to species with XY females

1988 ◽  
Vol 322 (1208) ◽  
pp. 83-95 ◽  
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Mammalian Species ◽  
Y Chromosomes ◽  
Wood Lemming ◽  
Xx Males ◽  
Original Size ◽  
Myopus Schisticolor ◽  
Dicrostonyx Torquatus

Both mouse and man have the common XX/XY sex chromosome mechanism. The X chromosome is of original size (5-6% of female haploid set) and the Y is one of the smallest chromosomes of the complement. But there are species, belonging to a variety of orders, with composite sex chromosomes and multiple sex chromosome systems: XX/XY 1 Y 2 and X 1 X 1 X 2 X 2 /X 1 X 2 Y. The original X or the Y, respectively, have been translocated on to an autosome. The sex chromosomes of these species segregate regularly at meiosis; two kinds of sperm and one kind of egg are produced and the sex ratio is the normal 1:1. Individuals with deviating sex chromosome constitutions (XXY, XYY, XO or XXX) have been found in at least 16 mammalian species other than man. The phenotypic manifestations of these deviating constitutions are briefly discussed. In the dog, pig, goat and mouse exceptional XX males and in the horse XY females attract attention. Certain rodents have complicated mechanisms for sex determination: Ellobius lutescens and Tokudaia osimensis have XO males and females. Both sexes of Microtus oregoni are gonosomic mosaics (male OY/XY, female XX/XO). The wood lemming, Myopus schisticolor , the collared lemming, Dicrostonyx torquatus , and perhaps also one or two species of the genus Akodon have XX and XY females and XY males. The XX, X*X and X*Y females of Myopus and Dicrostonyx are discussed in some detail. The wood lemming has proved to be a favourable natural model for studies in sex determination, because a large variety of sex chromosome aneuploids are born relatively frequently. The dosage model for sex determination is not supported by the wood lemming data. For male development, genes on both the X and the Y chromosomes are necessary.

Unusual sex chromosome inheritance in mammals

1970 ◽  
Vol 259 (828) ◽  
pp. 15-36 ◽  
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
General Pattern ◽  
Male Meiosis ◽  
Present Knowledge ◽  
Microtus Arvalis ◽  
Present Contribution ◽  
Original Size ◽  
Heterogametic Sex

The male has proven to be the heterogametic sex in all mammals studied so far. As is well known, the males usually have the sex chromosomes XY and the females XX. In recent years, however, many exceptions from this general pattern have been discovered. With our present knowledge, the different sex chromosome mechanisms in mammals may be divided into five main groups, and the first of them into subgroups, as follows: (i) Species with XX/XY sex chromosomes: (a) X of original size (see below), Y small; (b) X large, Y small; (c) X large, Y large: (i) end-to-end association of X and Y at male meiosis, (ii) chiasma between X and Y at male meiosis. (ii) Species with XX/XY 1 Y 2 sex chromosomes. (iii) Species with X 1 X 1 X 2 X 2 /X 1 X 2 Y sex chromosomes. (iv) Species with complicated or unknown mechanisms for sex determination. (v) Species with mosaicism of the sex chromosomes, but apparently with an XX/XY mechanism for sex determination. The present contribution will mainly deal with unusual sex chromosome inheritance, that is the groups (ii), (iii) and (iv) above, but the other two groups will also be briefly discussed and examples will be given. Recently Raicu, Kirillova & Hamar (1969) described a new sex chromosome mechanism ( X 1 X 1 X 2 X 2 /X 1 X 2 Y 1 Y 2 ) in the vole Microtus arvalis , but this observation was not confirmed by Schmid (1969), who found an ordinary XX/XY mechanism with both X and Y readily identifiable and of ‘normal’ size, the X comprising 5.6% of ( n A + X) and Y being the smallest chromosome of the complement. Late DNA replication was demonstrated in the allocyclic X and in the Y. Also Wolf (1969) found normal sex chromosomes in this species with no multivalents at male meiosis.

scholarly journals Y-chromosome haplotypes of varying differentiation to the X are not associated with male fitness in common frogs

2019 ◽  
Author(s):  
Paris Veltsos ◽  
Nicolas Rodrigues ◽  
Tania Studer ◽  
Wen-Juan Ma ◽  
Roberto Sermier ◽  
...  
Keyword(s):  
Sexual Dimorphism ◽  
Y Chromosome ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Sex Chromosome Evolution ◽  
Chromosome Differentiation ◽  
Y Chromosomes ◽  
Male Phenotype ◽  
Xx Males

AbstractThe canonical model of sex-chromosome evolution assigns a key role to sexually antagonistic (SA) genes on the arrest of recombination and ensuing degeneration of Y chromosomes. This assumption cannot be tested in organisms with highly differentiated sex chromosomes, such as mammals or birds, owing to the lack of polymorphism. Fixation of SA alleles, furthermore, might be the consequence rather than the cause of recombination arrest. Here we focus on a population of common frogs (Rana temporaria) where XY males with genetically differentiated Y chromosomes (non-recombinant Y haplotypes) coexist with both XY° males with proto-Y chromosomes (only differentiated from X chromosomes in the immediate vicinity of the candidate sex-determining locus Dmrt1) and XX males with undifferentiated sex chromosomes (genetically identical to XX females). Our study shows no effect of sex-chromosome differentiation on male phenotype, mating success or fathering success. Our conclusions rejoin genomic studies that found no differences in gene expression between XY, XY° and XX males. Sexual dimorphism in common frogs seems to result from the differential expression of autosomal genes rather than sex-linked SA genes. Among-male variance in sex-chromosome differentiation is better explained by a polymorphism in the penetrance of alleles at the sex locus, resulting in variable levels of sex reversal (and thus of X-Y recombination in XY females), independent of sex-linked SA genes.Impact SummaryHumans, like other mammals, present highly differentiated sex chromosomes, with a large, gene-rich X chromosome contrasting with a small, gene-poor Y chromosome. This differentiation results from a process that started approximately 160 Mya, when the Y first stopped recombining with the X. How and why this happened, however, remain controversial. According to the canonical model, the process was initiated by sexually antagonistic selection; namely, selection on the proto-Y chromosome for alleles that were beneficial to males but detrimental to females. The arrest of XY recombination then allowed such alleles to be only transmitted to sons, not to daughters. Although appealing and elegant, this model can no longer be tested in mammals, as it requires a sex-chromosome system at an incipient stage of evolution. Here we focus on a frog that displays within-population polymorphism is sex-chromosome differentiation, where XY males with differentiated chromosomes coexist with XX males lacking Y chromosomes. We find no effect of sex-chromosome differentiation on male phenotype or mating success, opposing expectations from the standard model. Sex linked genes do not seem to have a disproportionate effect on sexual dimorphism. From our results, sexually antagonistic genes show no association with sex-chromosome differentiation in frogs, which calls for alternative models of sex-chromosome evolution.

Monotreme sex chromosomes - implications for the evolution of amniote sex chromosomes

2009 ◽  
Vol 21 (8) ◽  
pp. 943 ◽  
Author(s):  
Paul D. Waters ◽  
Jennifer A. Marshall Graves
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Female Development ◽  
Comparative Gene Mapping ◽  
Y Chromosomes ◽  
Daunting Task ◽  
Platypus Genome ◽  
Genetic Events

In vertebrates, a highly conserved pathway of genetic events controls male and female development, to the extent that many genes involved in human sex determination are also involved in fish sex determination. Surprisingly, the master switch to this pathway, which intuitively could be considered the most critical step, is inconsistent between vertebrate taxa. Interspersed in the vertebrate tree there are species that determine sex by environmental cues such as the temperature at which eggs are incubated, and then there are genetic sex-determination systems, with male heterogametic species (XY systems) and female heterogametic species (ZW systems), some of which have heteromorphic, and others homomorphic, sex chromosomes. This plasticity of sex-determining switches in vertebrates has made tracking the events of sex chromosome evolution in amniotes a daunting task, but comparative gene mapping is beginning to reveal some striking similarities across even distant taxa. In particular, the recent completion of the platypus genome sequence has completely changed our understanding of when the therian mammal X and Y chromosomes first arose (they are up to 150 million years younger than previously thought) and has also revealed the unexpected insight that sex determination of the amniote ancestor might have been controlled by a bird-like ZW system.

scholarly journals Male-specific restriction of recombination frequency in the sex chromosomes of the medaka, Oryzias latipes

1999 ◽  
Vol 73 (3) ◽  
pp. 225-231 ◽  
Author(s):  
MASARU MATSUDA ◽  
SAEMI SOTOYAMA ◽  
SATOSHI HAMAGUCHI ◽  
MITSURU SAKAIZUMI
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Recombination Frequency ◽  
Oryzias Latipes ◽  
Body Colour ◽  
Specific Restriction ◽  
Xx Males ◽  
Heterogametic Sex ◽  
Male Specific

In the medaka, Oryzias latipes, the mechanism of sex determination (XX/XY) can be revealed by genetic crosses using a body-colour gene, though it does not have cytologically recognizable sex chromosomes. The recombination restriction of sex chromosomes in heterogametic (XY) males has been demonstrated. To elucidate whether the recombination is prevented by the heterogamety of the sex chromosomes or by maleness, we examined the recombination frequencies among three loci located on the sex chromosomes (r, SL1 and SL2) in heterogametic males (XY), homogametic males (XX and YY), homogametic females (XX) and heterogametic females (XY). The recombination frequencies between r–SL1 and SL1–SL2 were as follows: 0, 0 (XY males); 0, 1·5 (XX males); 1·6% (YY males; 1·2%, 14·4% (XY females); 0·8%, 21·8% (XX females). These results indicate that the recombination restriction of the sex chromosomes in heterogametic males does not result from heterogametic sex chromosomes, but from maleness. Such sex-chromosome- specific recombination restriction in heterogametic sex may have triggered the differentiation of sex chromosomes in vertebrates.

scholarly journals The Diversity and Evolution of Sex Chromosomes in Frogs

Genes ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 483
Author(s):  
Wen-Juan Ma ◽  
Paris Veltsos
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Comparative Genomic ◽  
Ancestral State ◽  
Heteromorphic Sex Chromosomes ◽  
Genomic Studies ◽  
Evolutionary Trajectories ◽  
Heterogametic Sex

Frogs are ideal organisms for studying sex chromosome evolution because of their diversity in sex chromosome differentiation and sex-determination systems. We review 222 anuran frogs, spanning ~220 Myr of divergence, with characterized sex chromosomes, and discuss their evolution, phylogenetic distribution and transitions between homomorphic and heteromorphic states, as well as between sex-determination systems. Most (~75%) anurans have homomorphic sex chromosomes, with XY systems being three times more common than ZW systems. Most remaining anurans (~25%) have heteromorphic sex chromosomes, with XY and ZW systems almost equally represented. There are Y-autosome fusions in 11 species, and no W-/Z-/X-autosome fusions are known. The phylogeny represents at least 19 transitions between sex-determination systems and at least 16 cases of independent evolution of heteromorphic sex chromosomes from homomorphy, the likely ancestral state. Five lineages mostly have heteromorphic sex chromosomes, which might have evolved due to demographic and sexual selection attributes of those lineages. Males do not recombine over most of their genome, regardless of which is the heterogametic sex. Nevertheless, telomere-restricted recombination between ZW chromosomes has evolved at least once. More comparative genomic studies are needed to understand the evolutionary trajectories of sex chromosomes among frog lineages, especially in the ZW systems.

scholarly journals The maintenance of polygenic sex determination depends on the dominance of fitness effects which are predictive of the role of sexual antagonism

2021 ◽  
Author(s):  
Richard P Meisel
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
House Fly ◽  
Sexual Antagonism ◽  
Antagonistic Effects ◽  
Fitness Effects ◽  
Y Chromosomes ◽  
Sexually Antagonistic Selection ◽  
The Individual ◽  
Polygenic Sex Determination

Abstract In species with polygenic sex determination, multiple male- and female-determining loci on different proto-sex chromosomes segregate as polymorphisms within populations. The extent to which these polymorphisms are at stable equilibria is not yet resolved. Previous work demonstrated that polygenic sex determination is most likely to be maintained as a stable polymorphism when the proto-sex chromosomes have opposite (sexually antagonistic) fitness effects in males and females. However, these models usually consider polygenic sex determination systems with only two proto-sex chromosomes, or they do not broadly consider the dominance of the alleles under selection. To address these shortcomings, I used forward population genetic simulations to identify selection pressures that can maintain polygenic sex determination under different dominance scenarios in a system with more than two proto-sex chromosomes (modeled after the house fly). I found that overdominant fitness effects of male-determining proto-Y chromosomes are more likely to maintain polygenic sex determination than dominant, recessive, or additive fitness effects. The overdominant fitness effects that maintain polygenic sex determination tend to have proto-Y chromosomes with sexually antagonistic effects (male-beneficial and female-detrimental). In contrast, dominant fitness effects that maintain polygenic sex determination tend to have sexually antagonistic multi-chromosomal genotypes, but the individual proto-sex chromosomes do not have sexually antagonistic effects. These results demonstrate that sexual antagonism can be an emergent property of the multi-chromosome genotype without individual sexually antagonistic chromosomes. My results further illustrate how the dominance of fitness effects has consequences for both the likelihood that polygenic sex determination will be maintained as well as the role sexually antagonistic selection is expected to play in maintaining the polymorphism.

scholarly journals Telomere-to-telomere assembly of a fish Y chromosome reveals the origin of a young sex chromosome pair

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Lingzhan Xue ◽  
Yu Gao ◽  
Meiying Wu ◽  
Tian Tian ◽  
Haiping Fan ◽  
...  
Keyword(s):  
Y Chromosome ◽  
Sex Chromosomes ◽  
Chromosome Pair ◽  
Sex Chromosome ◽  
Structural Variations ◽  
Recombination Suppression ◽  
Chromosome Differentiation ◽  
Y Chromosomes ◽  
Recent Origin ◽  
Mastacembelus Armatus

Abstract Background The origin of sex chromosomes requires the establishment of recombination suppression between the proto-sex chromosomes. In many fish species, the sex chromosome pair is homomorphic with a recent origin, providing species for studying how and why recombination suppression evolved in the initial stages of sex chromosome differentiation, but this requires accurate sequence assembly of the X and Y (or Z and W) chromosomes, which may be difficult if they are recently diverged. Results Here we produce a haplotype-resolved genome assembly of zig-zag eel (Mastacembelus armatus), an aquaculture fish, at the chromosomal scale. The diploid assembly is nearly gap-free, and in most chromosomes, we resolve the centromeric and subtelomeric heterochromatic sequences. In particular, the Y chromosome, including its highly repetitive short arm, has zero gaps. Using resequencing data, we identify a ~7 Mb fully sex-linked region (SLR), spanning the sex chromosome centromere and almost entirely embedded in the pericentromeric heterochromatin. The SLRs on the X and Y chromosomes are almost identical in sequence and gene content, but both are repetitive and heterochromatic, consistent with zero or low recombination. We further identify an HMG-domain containing gene HMGN6 in the SLR as a candidate sex-determining gene that is expressed at the onset of testis development. Conclusions Our study supports the idea that preexisting regions of low recombination, such as pericentromeric regions, can give rise to SLR in the absence of structural variations between the proto-sex chromosomes.

scholarly journals Differences in recombination frequencies during female and male meioses of the sex chromosomes of the medaka, Oryzias latipes

2001 ◽  
Vol 78 (1) ◽  
pp. 23-30 ◽  
Author(s):  
MARIKO KONDO ◽  
ERIKO NAGAO ◽  
HIROSHI MITANI ◽  
AKIHIRO SHIMA
Keyword(s):  
Genetic Map ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Oryzias Latipes ◽  
Male Recombination ◽  
Male And Female ◽  
Y Chromosomes ◽  
Genetic Length ◽  
Expressed Sequence ◽  
Group 1

In the medaka, Oryzias latipes, sex is determined chromosomally. The sex chromosomes differ from those of mammals in that the X and Y chromosomes are highly homologous. Using backcross panels for linkage analysis, we mapped 21 sequence tagged site (STS) markers on the sex chromosomes (linkage group 1). The genetic map of the sex chromosome was established using male and female meioses. The genetic length of the sex chromosome was shorter in male than in female meioses. The region where male recombination is suppressed is the region close to the sex-determining gene y, while female recombination was suppressed in both the telomeric regions. The restriction in recombination does not occur uniformly on the sex chromosome, as the genetic map distances of the markers are not proportional in male and female recombination. Thus, this observation seems to support the hypothesis that the heterogeneous sex chromosomes were derived from suppression of recombination between autosomal chromosomes. In two of the markers, Yc-2 and Casp6, which were expressed sequence-tagged (EST) sites, polymorphisms of both X and Y chromosomes were detected. The alleles of the X and Y chromosomes were also detected in O. curvinotus, a species related to the medaka. These markers could be used for genotyping the sex chromosomes in the medaka and other species, and could be used in other studies on sex chromosomes.

scholarly journals Kinase CDK2 in Mammalian Meiotic Prophase I: Screening for Hetero- and Homomorphic Sex Chromosomes

2021 ◽  
Vol 22 (4) ◽  
pp. 1969
Author(s):  
Sergey Matveevsky ◽  
Tsenka Chassovnikarova ◽  
Tatiana Grishaeva ◽  
Maret Atsaeva ◽  
Vasilii Malygin ◽  
...  
Keyword(s):  
Sex Chromosomes ◽  
Mammalian Species ◽  
Critical Role ◽  
Eukaryotic Cell ◽  
Repair System ◽  
Prophase I ◽  
Meiotic Chromosomes ◽  
Y Chromosomes ◽  
Dna Mismatch Repair System ◽  
Male Sex

Cyclin-dependent kinases (CDKs) are crucial regulators of the eukaryotic cell cycle. The critical role of CDK2 in the progression of meiosis was demonstrated in a single mammalian species, the mouse. We used immunocytochemistry to study the localization of CDK2 during meiosis in seven rodent species that possess hetero- and homomorphic male sex chromosomes. To compare the distribution of CDK2 in XY and XX male sex chromosomes, we performed multi-round immunostaining of a number of marker proteins in meiotic chromosomes of the rat and subterranean mole voles. Antibodies to the following proteins were used: RAD51, a member of the double-stranded DNA break repair machinery; MLH1, a component of the DNA mismatch repair system; and SUN1, which is involved in the connection between the meiotic telomeres and nuclear envelope, alongside the synaptic protein SYCP3 and kinetochore marker CREST. Using an enhanced protocol, we were able to assess the distribution of as many as four separate proteins in the same meiotic cell. We showed that during prophase I, CDK2 localizes to telomeric and interstitial regions of autosomes in all species investigated (rat, vole, hamster, subterranean mole voles, and mole rats). In sex bivalents following synaptic specificity, the CDK2 signals were distributed in three different modes. In the XY bivalent in the rat and mole rat, we detected numerous CDK2 signals in asynaptic regions and a single CDK2 focus on synaptic segments, similar to the mouse sex chromosomes. In the mole voles, which have unique XX sex chromosomes in males, CDK2 signals were nevertheless distributed similarly to the rat XY sex chromosomes. In the vole, sex chromosomes did not synapse, but demonstrated CDK2 signals of varying intensity, similar to the rat X and Y chromosomes. In female mole voles, the XX bivalent had CDK2 pattern similar to autosomes of all species. In the hamster, CDK2 signals were revealed in telomeric regions in the short synaptic segment of the sex bivalent. We found that CDK2 signals colocalize with SUN1 and MLH1 signals in meiotic chromosomes in rats and mole voles, similar to the mouse. The difference in CDK2 manifestation at the prophase I sex chromosomes can be considered an example of the rapid chromosome evolution in mammals.

scholarly journals A 180 Myr-old female-specific genome region in sturgeon reveals the oldest known vertebrate sex determining system with undifferentiated sex chromosomes

2021 ◽  
Vol 376 (1832) ◽  
pp. 20200089
Author(s):  
Heiner Kuhl ◽  
Yann Guiguen ◽  
Christin Höhne ◽  
Eva Kreuz ◽  
Kang Du ◽  
...  
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Specific Sequence ◽  
Genome Region ◽  
Acipenser Ruthenus ◽  
Determination System ◽  
Sex Determination System ◽  
Female Specific ◽  
Polyploidization Event

Several hypotheses explain the prevalence of undifferentiated sex chromosomes in poikilothermic vertebrates. Turnovers change the master sex determination gene, the sex chromosome or the sex determination system (e.g. XY to WZ). Jumping master genes stay main triggers but translocate to other chromosomes. Occasional recombination (e.g. in sex-reversed females) prevents sex chromosome degeneration. Recent research has uncovered conserved heteromorphic or even homomorphic sex chromosomes in several clades of non-avian and non-mammalian vertebrates. Sex determination in sturgeons (Acipenseridae) has been a long-standing basic biological question, linked to economical demands by the caviar-producing aquaculture. Here, we report the discovery of a sex-specific sequence from sterlet ( Acipenser ruthenus ). Using chromosome-scale assemblies and pool-sequencing, we first identified an approximately 16 kb female-specific region. We developed a PCR-genotyping test, yielding female-specific products in six species, spanning the entire phylogeny with the most divergent extant lineages ( A. sturio, A. oxyrinchus versus A. ruthenus, Huso huso ), stemming from an ancient tetraploidization. Similar results were obtained in two octoploid species ( A. gueldenstaedtii, A. baerii ). Conservation of a female-specific sequence for a long period, representing 180 Myr of sturgeon evolution, and across at least one polyploidization event, raises many interesting biological questions. We discuss a conserved undifferentiated sex chromosome system with a ZZ/ZW-mode of sex determination and potential alternatives. This article is part of the theme issue ‘Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part I)’.

Sign in / Sign up

Export Citation Format

Share Document