The great escape

Sin, Ho-Su; Namekawa, Satoshi H.

doi:10.4161/epi.25672

Cited by 25 publications

(12 citation statements)

References 55 publications

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“…This likely reflects relaxed evolutionary constraints typically associated with genes that are tissue or cell-specific [78], as well as positive selection on genes influencing sperm form and function across species [77]. The X-linked genes that escape PSCR tend to play critical roles in sperm development [79] but evolve even faster than postmeiotic genes on the autosomes [31]. Interestingly, a recent study found that postmeiotic gene expression divergence appears slower, not faster on the X-chromosome [31].…”

Section: Postmeiotic Phase: Conflict Between the X And Ymentioning

confidence: 99%

“…The leading mechanistic hypothesis for this genomic pattern is that copy number expansions evolve essentially as dosage compensation responses that allow critical X-linked spermatogenic genes to overcome the repressive chromatin environment of PSCR [3,76,79]. This model posits a relationship between ampliconic expansions, overall expression levels, and sperm development.…”

Section: Postmeiotic Phase: Conflict Between the X And Ymentioning

confidence: 99%

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Spermatogenesis and the Evolution of Mammalian Sex Chromosomes

2018

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Developmental constraint and sexual conflict shape the evolution of heteromorphic sex chromosomes. These contrasting forces are perhaps strongest during spermatogenesis in species with XY males. In this review, we consider how the unique regulatory environment and selective pressures of spermatogenesis interact to impact sex chromosome evolution in mammals. We explore how each developmental phase of spermatogenesis influences sex chromosome gene content, structure, and rate of molecular evolution, and how these attributes may contribute to speciation. We argue that a developmental context is fundamental to understanding sex chromosome evolution and that an evolutionary perspective can shed new light on our understanding of sperm development.

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Section: Postmeiotic Phase: Conflict Between the X And Ymentioning

confidence: 99%

Section: Postmeiotic Phase: Conflict Between the X And Ymentioning

confidence: 99%

Spermatogenesis and the Evolution of Mammalian Sex Chromosomes

2018

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“…In spite of postmeiotic silencing in round spermatids, a set of sex chromosome-linked genes, which function in late spermatogenesis, escapes postmeiotic silencing and is activated [ 17 , 20 ]. This escape gene activation is controlled by the DDR factor RNF8, an interacting partner of MDC1 [ 21 , 22 ]. Currently, the epigenetic landscape associated with epigenetic programming of the sex chromosomes during meiosis remains largely unknown.…”

Section: Introductionmentioning

confidence: 99%

Poised chromatin and bivalent domains facilitate the mitosis-to-meiosis transition in the male germline

et al. 2015

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BackgroundThe male germline transcriptome changes dramatically during the mitosis-to-meiosis transition to activate late spermatogenesis genes and to transiently suppress genes commonly expressed in somatic lineages and spermatogenesis progenitor cells, termed somatic/progenitor genes.ResultsThese changes reflect epigenetic regulation. Induction of late spermatogenesis genes during spermatogenesis is facilitated by poised chromatin established in the stem cell phases of spermatogonia, whereas silencing of somatic/progenitor genes during meiosis and postmeiosis is associated with formation of bivalent domains which also allows the recovery of the somatic/progenitor program after fertilization. Importantly, during spermatogenesis mechanisms of epigenetic regulation on sex chromosomes are different from autosomes: X-linked somatic/progenitor genes are suppressed by meiotic sex chromosome inactivation without deposition of H3K27me3.ConclusionsOur results suggest that bivalent H3K27me3 and H3K4me2/3 domains are not limited to developmental promoters (which maintain bivalent domains that are silent throughout the reproductive cycle), but also underlie reversible silencing of somatic/progenitor genes during the mitosis-to-meiosis transition in late spermatogenesis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-015-0159-8) contains supplementary material, which is available to authorized users.

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“…This, together with our findings on palindrome structures, suggests there are alternative mechanisms for X-palindromic genes to be expressed on the otherwise transcriptionally repressed X chromosome. There are a small number of X-linked single-copy genes expressed in round spermatids 6,20 , indicating that multiple gene copies are not a strict requirement for post-meiotic gene expression from the sex chromosomes. Thus, specific enhancers and transcription factors may have evolved to overcome the transcriptional repression associated with the rest of the sex chromosomes.…”

Section: Discussionmentioning

confidence: 99%

Male mice with large inversions or deletions of X-palindrome arms are fertile and express their associated genes post-meiosis

Kruger

Ellison

Brogley

et al. 2018

Preprint

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Large (>10 kb) palindromic sequences are enriched on mammalian sex chromosomes. In mice, these palindromes harbor gene families (≥2 gene copies) expressed exclusively in post-meiotic testicular germ cells, at a time when most single-copy sex-linked genes are transcriptionally repressed. This distinct expression pattern led to the hypothesis that containment within palindrome structures or having ≥2 gene enables post-meiotic gene expression. We tested these two hypotheses by using CRISPR to precisely engineer large (10's of kb) inversions and deletions of X chromosome palindrome arms for two regions carrying the mouse 4930567H17Rik and Mageb5 gene families. We found that 4930567H17Rik and Mageb5 gene expression is unaffected in mice carrying palindrome arm inversions, suggesting that palindromic structure is not important for mediating palindrome-associated gene expression. We also found that 4930567H17Rik and Mageb5 gene expression is reduced by half in mice carrying palindrome arm deletions, allowing us to test whether palindrome-associated genes are sensitive to reduced expression levels resulting in spermatogenic defects. Male mice carrying palindrome arm deletions of 4930567H17Rik or Mageb5, however, are fertile, have normal testis histology, and show no aberrations in spermatogenic cell population frequencies via FACS quantification. Together, these findings suggest that large palindromic structures on the sex chromosomes are not necessary for their associated genes to evade post-meiotic transcriptional repression and that these genes are not sensitive to reduced expression levels.

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The great escape

Cited by 25 publications

References 55 publications

Spermatogenesis and the Evolution of Mammalian Sex Chromosomes

Spermatogenesis and the Evolution of Mammalian Sex Chromosomes

Poised chromatin and bivalent domains facilitate the mitosis-to-meiosis transition in the male germline

Male mice with large inversions or deletions of X-palindrome arms are fertile and express their associated genes post-meiosis

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