title: Evaluating the relationship between spermatogenic silencing of the X chromosome and evolution of the Y chromosome in chimpanzee and human.
abstract: Chimpanzees and humans are genetically very similar, with the striking exception of their Y chromosomes, which have diverged tremendously. The male-specific region (MSY), representing the greater part of the Y chromosome, is inherited from father to son in a clonal fashion, with natural selection acting on the MSY as a unit. Positive selection might involve the performance of the MSY in spermatogenesis. Chimpanzees have a highly polygamous mating behavior, so that sperm competition is thought to provide a strong selective force acting on the Y chromosome in the chimpanzee lineage. In consequence of evolution of the heterologous sex chromosomes in mammals, meiotic sex chromosome inactivation (MSCI) results in a transcriptionally silenced XY body in male meiotic prophase, and subsequently also in postmeiotic repression of the sex chromosomes in haploid spermatids. This has evolved to a situation where MSCI has become a prerequisite for spermatogenesis. Here, by analysis of microarray testicular expression data representing a small number of male chimpanzees and men, we obtained information indicating that meiotic and postmeiotic X chromosome silencing might be more effective in chimpanzee than in human spermatogenesis. From this, we suggest that the remarkable reorganization of the chimpanzee Y chromosome, compared to the human Y chromosome, might have an impact on its meiotic interactions with the X chromosome and thereby on X chromosome silencing in spermatogenesis. Further studies will be required to address comparative functional aspects of MSCI in chimpanzee, human, and other placental mammals.
authors.affiliation: Department of Reproduction and Development, Erasmus MC-University Medical Center, Rotterdam, The Netherlands.
authors.forename: Eskeatnaf
authors.initials: E
authors.lastname: Mulugeta Achame
authors.forename: Willy M
authors.initials: WM
authors.lastname: Baarends
authors.forename: Joost
authors.initials: J
authors.lastname: Gribnau
authors.forename: J Anton
authors.initials: JA
authors.lastname: Grootegoed
mesh_terms: D000818:Animals; D041321:Chromosomes, Human, X / Q000235:genetics*; D041322:Chromosomes, Human, Y / Q000235:genetics*; D005786:Gene Expression Regulation; D020868:Gene Silencing; D006801:Humans; D008297:Male; D008540:Meiosis; D002679:Pan troglodytes; D011418:Prophase; D012726:Sexual Behavior, Animal; D013091:Spermatogenesis; D013737:Testis / Q000378:metabolism; D014960:X Chromosome / Q000235:genetics*; D014998:Y Chromosome / Q000235:genetics*