Department of Reproduction and Development, Erasmus MC-University Medical Center, Rotterdam, The Netherlands.
PLoS One. 2010 Dec 14;5(12):e15598. doi: 10.1371/journal.pone.0015598.
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.
黑猩猩和人类在基因上非常相似，除了它们的 Y 染色体有很大的差异外。雄性特异性区域（MSY），代表了 Y 染色体的大部分，以克隆的方式从父亲遗传给儿子，自然选择以 MSY 作为一个单位起作用。正选择可能涉及 MSY 在精子发生中的表现。黑猩猩有高度的多配偶交配行为，因此认为精子竞争在黑猩猩谱系的 Y 染色体上提供了强大的选择性力量。由于哺乳动物的异型性染色体的进化，减数分裂性染色体失活（MSCI）导致雄性减数分裂前期的 XY 体转录沉默，随后在单倍体精子中也抑制了性染色体。这已经演变成 MSCI 成为精子发生的先决条件。在这里，通过分析代表少数雄性黑猩猩和男性的微阵列睾丸表达数据，我们获得了表明在黑猩猩减数分裂和减数分裂后 X 染色体沉默可能比在人类精子发生中更有效的信息。由此，我们认为与人类 Y 染色体相比，黑猩猩 Y 染色体的显著重组可能会对其与 X 染色体的减数分裂相互作用产生影响，从而影响精子发生中的 X 染色体沉默。需要进一步的研究来解决黑猩猩、人类和其他胎盘哺乳动物中 MSCI 的比较功能方面的问题。
