Epigenetic Impacts on Sex Chromosome Evolution
Sex chromosome inactivation is essential epigenetic programming in male germ cells. However, it remains largely unclear how epigenetic silencing of sex chromosomes impacts the evolution of the mammalian genome. We recently demonstrated that male sex chromosome inactivation is highly conserved between humans and mice and has an impact on the genetic evolution of human sex chromosomes. Our analyses suggest that male sex chromosome inactivation has impacted multiple aspects of the evolutionary history of mammalian sex chromosomes: amplification of copy number, retrotranspositions, acquisition of de novo genes, and acquisition of different expression profiles. We propose that the epigenetic silencing mechanism impacts the genetic evolution of sex chromosomes and contributed to speciation and reproductive diversity in mammals. We further investigate the epigenetic impacts on sex chromosome evolution.
Figure 2 - Evolutional impacts of postmeiotic silencing. (A) Evolutional history of escape genes from postmeiotic silencing in the course of mammalian evolution. Genes in Lists A-F are displayed in Table S8. Stars denote the acquisition timing of de novo genes. Mya: million years ago. (B) Distribution of Ka/Ks values of X-linked escape genes and non-escape genes (listed in Table S9) along the length of the X chromosome. Ka/Ksvalues are calculated between humans and mice. Sin et al Genome Res 2012 22: 827-836.