Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, Texas, United States of America.
PLoS One. 2011;6(7):e21374. doi: 10.1371/journal.pone.0021374. Epub 2011 Jul 25.
Studies of the Y chromosome in primates, rodents and carnivores provide compelling evidence that the male specific region of Y (MSY) contains functional genes, many of which have specialized roles in spermatogenesis and male-fertility. Little similarity, however, has been found between the gene content and sequence of MSY in different species. This hinders the discovery of species-specific male fertility genes and limits our understanding about MSY evolution in mammals. Here, a detailed MSY gene catalogue was developed for the horse--an odd-toed ungulate. Using direct cDNA selection from horse testis, and sequence analysis of Y-specific BAC clones, 37 horse MSY genes/transcripts were identified. The genes were mapped to the MSY BAC contig map, characterized for copy number, analyzed for transcriptional profiles by RT-PCR, examined for the presence of ORFs, and compared to other mammalian orthologs. We demonstrate that the horse MSY harbors 20 X-degenerate genes with known orthologs in other eutherian species. The remaining 17 genes are acquired or novel and have so far been identified only in the horse or donkey Y chromosomes. Notably, 3 transcripts were found in the heterochromatic part of the Y. We show that despite substantial differences between the sequence, gene content and organization of horse and other mammalian Y chromosomes, the functions of MSY genes are predominantly related to testis and spermatogenesis. Altogether, 10 multicopy genes with testis-specific expression were identified in the horse MSY, and considered likely candidate genes for stallion fertility. The findings establish an important foundation for the study of Y-linked genetic factors governing fertility in stallions, and improve our knowledge about the evolutionary processes that have shaped Y chromosomes in different mammalian lineages.
灵长类动物、啮齿类动物和食肉动物的 Y 染色体研究提供了令人信服的证据，证明 Y 染色体上的雄性特异性区域（MSY）包含功能性基因，其中许多基因在精子发生和雄性生育力中具有特殊作用。然而，不同物种的 MSY 中的基因含量和序列之间几乎没有相似之处。这阻碍了对物种特异性雄性生育力基因的发现，并限制了我们对哺乳动物 MSY 进化的理解。在这里，我们为马——一种奇数蹄类动物——开发了一个详细的 MSY 基因目录。通过直接从马睾丸中选择 cDNA，以及对 Y 特异性 BAC 克隆进行序列分析，我们鉴定了 37 个马 MSY 基因/转录本。这些基因被映射到 MSY BAC 连续图谱上，对其拷贝数进行了表征，通过 RT-PCR 分析了其转录谱，检查了它们是否存在 ORF，并与其他哺乳动物的同源基因进行了比较。我们证明，马 MSY 包含 20 个 X 退化基因，这些基因在其他真兽类物种中具有已知的同源基因。其余 17 个基因是获得的或新的，迄今为止只在马或驴的 Y 染色体上发现。值得注意的是，有 3 个转录本存在于 Y 染色体的异染色质部分。我们表明，尽管马和其他哺乳动物 Y 染色体之间在序列、基因含量和组织方面存在很大差异，但 MSY 基因的功能主要与睾丸和精子发生有关。总的来说，我们在马 MSY 中鉴定出了 10 个具有睾丸特异性表达的多拷贝基因，这些基因被认为是种马生育力的候选基因。这些发现为研究控制种马生育力的 Y 连锁遗传因素奠定了重要基础，并提高了我们对不同哺乳动物谱系中 Y 染色体进化过程的认识。
