The Robinson Institute, School of Molecular and Biomedical Science, The University of Adelaide, Adelaide, Australia.
Chromosome Res. 2012 Jan;20(1):127-38. doi: 10.1007/s10577-011-9270-z.
The basal lineage of monotremes features an extraordinarily complex sex chromosome system which has provided novel insights into the evolution of mammalian sex chromosomes. Recently, sequence information from autosomes, X chromosomes, and XY-shared pseudoautosomal regions has become available. However, no gene has so far been described on any of the Y chromosome-specific regions. We analyzed sequences derived from Y-specific BAC clones to identify genes with potentially male-specific function. Here, we report the identification and characterization of the mediator complex protein gametologs on platypus Y5 (Crspy). We also identified the X-chromosomal copy which unexpectedly maps to X1 (Crspx). Sequence comparison shows extensive divergence between the X and Y copy, but we found no significant positive selection on either gametolog. Expression analysis shows widespread expression of Crspx. Crspy is expressed exclusively in males with particularly strong expression in testis and kidney. Reporter gene assays to investigate whether Crspx/y can act on the recently discovered mouse Sox9 testis-specific enhancer element did reveal a modest effect together with mouse Sox9 + Sf1, but showed overall no significant upregulation of the reporter gene. This is the first report of a differentiated functional male-specific gene on platypus Y chromosomes, providing new insights into sex chromosome evolution and a candidate gene for male-specific function in monotremes.
单孔类动物的基础血统具有一种极其复杂的性染色体系统，这为哺乳动物性染色体的进化提供了新的见解。最近，来自常染色体、X 染色体和 XY 共享假常染色体区域的序列信息已经可用。然而，迄今为止，在任何 Y 染色体特异性区域都没有描述过基因。我们分析了来自 Y 染色体特异性 BAC 克隆的序列，以鉴定具有潜在雄性特异性功能的基因。在这里，我们报告了鸭嘴兽 Y5（Crspy）上的中介复合物蛋白 gametologs 的鉴定和特征。我们还鉴定了出乎意料地映射到 X1（Crspx）的 X 染色体拷贝。序列比较显示 X 和 Y 拷贝之间存在广泛的分歧，但我们没有发现任何 gametolog 上的显著正选择。表达分析显示 Crspx 广泛表达。Crspy 仅在雄性中表达，在睾丸和肾脏中表达特别强烈。调查 Crspx/y 是否可以作用于最近发现的小鼠 Sox9 睾丸特异性增强子元件的报告基因实验确实显示出与小鼠 Sox9+Sf1 适度的协同作用，但总体上没有显著上调报告基因。这是在鸭嘴兽 Y 染色体上鉴定出的第一个具有分化功能的雄性特异性基因，为性染色体进化提供了新的见解，并为单孔类动物的雄性特异性功能提供了候选基因。
