X Chromosomal Studies of Spermatogenic Failure

描述（由申请人提供）：本提案认为，对参与物种形成的快速进化基因的研究将为男性不育的人类分子遗传学提供重要见解。物种形成是两个种群在繁殖上相互隔离的过程。在新近分化的物种之间，生殖隔离通常表现为雄性不育。X染色体上快速进化的基因是这种生殖隔离的主要驱动因素。我的初步研究已经确定了快速进化的x连锁基因，这些基因隐藏在大的，近乎完美的，片段复制或扩增子中。我假设这些x扩增序列包含对精子发生至关重要的基因，并且这些序列在一个物种内的快速进化可能导致男性不育。我将在人类和老鼠身上进行研究来验证这一假设。在人类中，所有X染色体的扩增子都将被精确测序，以确定它们的基因组结构。在每个扩增区域的解析后，我将确定X扩增缺失与生精失败显著相关的程度；男性不育症最常见的类型。为了做到这一点，我将筛选500名生精失败的男性和500名对照人群中的缺失。为了测试人类x扩增基因是否在生精细胞中表达，我将对x扩增基因进行表达谱分析，以深入了解生精失败的分子发病机制。在小鼠中，12%的X染色体由扩增序列组成。两个X扩增区特别令人感兴趣，因为它们代表了X染色体上进化最快的区域，并且与杂交小鼠的生精失败有关。因此，这两个x扩增区是研究x扩增基因生精功能的极有希望的候选者。为了测试这两个x扩增区是否在生精失败中起作用，我将对这两个区域进行独立的靶向敲除。敲除小鼠的x扩增区提供了在人类中不可行的控制功能丧失和拯救实验的机会。人类DNA研究结合小鼠x扩增基因的分子特征，将有助于我们进一步了解x扩增基因在人类精子发生和生殖中的功能。

DESCRIPTION (provided by applicant): This proposal posits that the study of rapidly evolving genes involved in speciation will provide significant insights into the human molecular genetics of male infertility. Speciation is the process by which two populations become reproductively isolated. Between recently diverged species, reproductive isolation typically manifests itself in the form of male infertility. Rapidly evolving genes on the X chromosome are primary drivers of this reproductive isolation. My preliminary studies have identified rapidly evolving X-linked genes which are harbored in large, near-perfect, segmental duplications, or amplicons. I hypothesize that these X-ampliconic sequences contain genes critical for spermatogenesis and that the rapid evolution of these sequences within a species can lead to male infertility. I will perform studies in humans and mice to test this hypothesis. In humans, all amplicons of the X chromosome will be accurately sequenced to determine their genomic architecture. Upon resolution of each ampliconic region, I will determine the extent to which X- ampliconic deletions are significantly associated with spermatogenic failure; the most common type of male infertility. To do this I will screen for deletions in a collection of 500 men with spermatogenic failure and 500 men from a control population. To test whether human X-ampliconic genes are expressed in spermatogenic cells, I will perform expression profiling of X-ampliconic genes to provide insight into the molecular pathogenesis of spermatogenic failure. In mice, 12% of the X chromosome is comprised of ampliconic sequences. Two X-ampliconic regions are of particular interest because they represent the most rapidly evolving regions of the X chromosome and have been linked to spermatogenic failure in hybrid mice. Thus, these two X-ampliconic regions represent highly promising candidates to study the spermatogenic functions of X-ampliconic genes. To test whether these two X-ampliconic regions have a role in spermatogenic failure, I will generate independent targeted knockouts of both regions. The knockout of X-ampliconic regions in mice offers opportunities to perform controlled loss-of-function and rescue experiments not feasible in humans. The DNA studies in humans coupled with molecular characterizations of X-ampliconic genes in mice will be essential to advance our understanding of X-ampliconic gene functions in human spermatogenesis and reproduction. PUBLIC HEALTH RELEVANCE: Few genetic factors have been identified to explain the high incidence of spermatogenic failure, which affects 1-2% of all men. Understanding the location and role of X-linked genes in spermatogenic failure will help explain molecular mechanisms of spermatogenesis and important causes of infertility.