Murphy William J, Pearks Wilkerson A J, Raudsepp Terje, Agarwala Richa, Schäffer Alejandro A, Stanyon Roscoe, Chowdhary Bhanu P
Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, Texas, United States of America.
PLoS Genet. 2006 Mar;2(3):e43. doi: 10.1371/journal.pgen.0020043. Epub 2006 Mar 31.
Despite its importance in harboring genes critical for spermatogenesis and male-specific functions, the Y chromosome has been largely excluded as a priority in recent mammalian genome sequencing projects. Only the human and chimpanzee Y chromosomes have been well characterized at the sequence level. This is primarily due to the presumed low overall gene content and highly repetitive nature of the Y chromosome and the ensuing difficulties using a shotgun sequence approach for assembly. Here we used direct cDNA selection to isolate and evaluate the extent of novel Y chromosome gene acquisition in the genome of the domestic cat, a species from a different mammalian superorder than human, chimpanzee, and mouse (currently being sequenced). We discovered four novel Y chromosome genes that do not have functional copies in the finished human male-specific region of the Y or on other mammalian Y chromosomes explored thus far. Two genes are derived from putative autosomal progenitors, and the other two have X chromosome homologs from different evolutionary strata. All four genes were shown to be multicopy and expressed predominantly or exclusively in testes, suggesting that their duplication and specialization for testis function were selected for because they enhance spermatogenesis. Two of these genes have testis-expressed, Y-borne copies in the dog genome as well. The absence of the four newly described genes on other characterized mammalian Y chromosomes demonstrates the gene novelty on this chromosome between mammalian orders, suggesting it harbors many lineage-specific genes that may go undetected by traditional comparative genomic approaches. Specific plans to identify the male-specific genes encoded in the Y chromosome of mammals should be a priority.
尽管Y染色体在携带对精子发生和雄性特异性功能至关重要的基因方面具有重要性，但在最近的哺乳动物基因组测序项目中，它在很大程度上被排除在优先考虑范围之外。只有人类和黑猩猩的Y染色体在序列水平上得到了很好的表征。这主要是由于推测Y染色体的总体基因含量较低且具有高度重复性，以及随后使用鸟枪法序列组装方法时遇到的困难。在这里，我们使用直接cDNA选择法来分离和评估家猫基因组中Y染色体新基因获得的程度，家猫是一种与人类、黑猩猩和小鼠（目前正在测序）属于不同哺乳动物总目的物种。我们发现了四个新的Y染色体基因，它们在已完成测序的人类Y染色体雄性特异性区域或迄今为止探索的其他哺乳动物Y染色体上没有功能拷贝。其中两个基因源自假定的常染色体祖基因，另外两个基因在不同进化层有X染色体同源物。所有四个基因均显示为多拷贝，并且主要或仅在睾丸中表达，这表明它们因增强精子发生而被选择用于睾丸功能的复制和特化。其中两个基因在犬类基因组中也有睾丸表达的Y染色体携带拷贝。在其他已表征的哺乳动物Y染色体上未发现这四个新描述的基因，这表明该染色体在哺乳动物目之间存在基因新颖性，提示它含有许多可能未被传统比较基因组方法检测到的谱系特异性基因。确定哺乳动物Y染色体中编码的雄性特异性基因的具体计划应成为优先事项。
