Human postmeiotic sex chromatin and its impact on sex chromosome evolution

Sin, Ho-Su; Ichijima, Yosuke; Koh, Eitetsu; Namiki, Mikio; Namekawa, Satoshi H.

doi:10.1101/gr.135046.111

Cited by 51 publications

(96 citation statements)

References 46 publications

(82 reference statements)

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“…12 The epigenetic silencing machinery on male sex chromosomes is highly conserved between mice and humans, and the overall gene expression profile of sex-linked genes is consistent between the two species. Most sex-linked genes are stringently repressed at the pachytene stage of meiotic prophase and stay silent in round spermatids, except for escape genes that are mainly associated with male reproductive function.…”

Section: Evolutionary Aspects Of Escape Gene Activation In Male Germ mentioning

confidence: 99%

“…2). 12 Of the 66 escape genes found in humans and the 54 found in mice, only 12 escape genes are shared. Of the 54 mice escape genes, 25 are newly evolved genes found only in rodent lineage.…”

Section: Evolutionary Aspects Of Escape Gene Activation In Male Germ mentioning

confidence: 99%

“…Due to their tendency to avoid transcriptional silencing, these genes have been named "escape genes". [9][10][11][12] Although both males and females possess escape genes, the specific "escape genes" identified in female X-inactivation and in male sex chromosome inactivation differ greatly. Emerging evidence has revealed that active genes on the sex chromosomes are precisely regulated in both females and males.…”

Section: The Great Escapementioning

confidence: 99%

“…[32][33][34] Despite this transcriptionally repressed state, a group of sexlinked genes escape postmeiotic silencing and become activated on the silent sex chromosomes. 10,12,19,32,35 diverged during mammalian evolution. [17][18][19] Interestingly, this class of genes is predominantly expressed in male germ cells.…”

Section: The Great Escapementioning

confidence: 99%

“…Higher rate of amino acid changes (higher K A /K S value) of escape genes is in line with this notion. 12 Genes specifically expressed in round spermatids may affect the success of fertilization and reproduction. As discussed above, the X chromosome should be a preferable location for male reproduction genes; nevertheless, successful sex chromosome inactivation is still necessary to ensure fertility, as demonstrated by the disruption of MSCI in hybrid sterility.…”

Section: Unique Evolutionary Traits Of the Sex Chromosomesmentioning

confidence: 99%

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The great escape

Sin

Namekawa

2013

Epigenetics

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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.

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Section: Evolutionary Aspects Of Escape Gene Activation In Male Germ mentioning

confidence: 99%

Section: Evolutionary Aspects Of Escape Gene Activation In Male Germ mentioning

confidence: 99%

Section: The Great Escapementioning

confidence: 99%

Section: The Great Escapementioning

confidence: 99%

Section: Unique Evolutionary Traits Of the Sex Chromosomesmentioning

confidence: 99%

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The great escape

Sin

Namekawa

2013

Epigenetics

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Speciation: Chromosomal Mechanisms

Nevo¹

2012

Encyclopedia of Life Sciences

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Chromosomal speciation is one of the major modes of the origin of new species through the splitting of preexisting species. New species may originate by gene speciation, and also by the establishment of post‐mating reproductive isolation through structural chromosome rearrangements. The latter may induce low‐hybrid fitness, generated by macromutations, and even by micromutations, that is, molecular changes causing meiotic disturbances (e.g. GC incompatibilities), although the latter awaits empirical support. Criticism against the traditional model of chromosomal speciation led to renewed theoretical models arguing that chromosomal rearrangements can generate reproductive isolation between species by suppressing recombination within rearranged regions. Reduced recombination permits the accumulation of alleles contributing to reproductive isolation and adaptive divergence and radiation. Likewise, coding and noncoding genomes, and novel chromosomal breakpoint regions can generate novel combinations of genes and regulatory elements that contribute to both adaptive radiation and ecological speciation. Chromosomal speciation is certainly an important speciation mode across life, although we cannot yet quantify it in relation to other modes. The spalacid example of blind subterranean mole rats in the East Mediterranean is presented as a widely studied case of chromosomal ecological speciation. The proportion of chromosomal speciation in nature, particularly in animals, remains a future challenge. Key Concepts: Speciation – the evolutionary process leading to the multiplication of species and generating biodiversity. Chromosomal speciation – the theory asserting that chromosomal rearrangements cause reproductive isolation between populations and lead to speciation. Peripatric speciation – the origin of a new species by budding from a parental species established beyond the periphery of the parental species range. Sympatric speciation – speciation without geographic (spatial) isolation; the origin of a new species within a deme. Polyploidy – the condition in which the number of chromosomes is an integral greater than two of the haploid numbers. Biological species concept (BSC) – defines species as groups of interbreeding natural populations that are reproductively (genetically) isolated from other such groups. Allopatric speciation – the evolution of a population into a separate species involving a period of geographic isolation. The evolutionary divergence of a single phyletic line into different niches or adaptive zones.

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