Role of development signaling pathways in testicular physiology and spermatogenesis

睾酮，雄性生殖激素，是所有哺乳动物睾丸正常发育、青春期开始和精子细胞产生所必需的。睾丸激素分泌不足会产生一系列负面后果，如隐睾、假两性畸形和不育。虽然人们早就知道睾丸间质细胞产生睾酮是由垂体促黄体激素（LH）刺激的，但我们对这一调节过程在分子水平上如何起作用的理解仍然非常初步。我们的小组已经发现了强有力的初步证据，表明Hippo，一种传统上与胚胎发育相关的细胞内信号通路，在LH结合后被激活。然后，Hippo信号传导作用于抑制Yes相关蛋白（雅普）和具有PDZ结合基序的转录共激活因子（TAZ）的活性，这两种信号传导分子似乎阻断参与睾酮合成的基因的转录。在本提案中，我们将确认我们的初步研究结果，并确定Hippo通路中作用于LH下游的关键参与者。将详细研究雅普和TAZ对类固醇生成基因活性的影响。最后，我们将创建转基因小鼠，其中关键的Hippo途径基因将在其Leydig细胞中删除，我们将研究其删除对睾酮产生，类固醇基因表达，精子发生和生育力的后果。两者合计，这些研究应该发现以前未知的机制，调节睾酮合成，并可能提供深入了解睾酮不足的病因和潜在的治疗。

Testosterone, the male reproductive hormone, is necessary for normal development, the initiation of puberty and sperm cell production in the testes in all mammalian species. Inadequate testosterone production has a range of negative consequences, such as undescended testes, pseudohermaphroditism and infertility. Although it has long been known that testosterone production by the testicular Leydig cells is stimulated by pituitary luteinizing hormone (LH), our understanding of how this regulatory process works at a molecular level remains very rudimentary. Our group has uncovered strong preliminary evidence to suggest that Hippo, an intracellular signaling pathway traditionally associated with embryonic development, is activated following LH binding. Hippo signaling then acts to suppress the activity of Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ), two signaling molecules that seem to block the transcription of genes involved in testosterone synthesis. In the present proposal, we will confirm our preliminary findings and identify the key players within the Hippo pathway that act downstream of LH. The effects of YAP and TAZ on the activity of steroidogenic genes will be studied in detail. Finally, we will create transgenic mice in which critical Hippo pathway genes will be deleted in their Leydig cells, and we will study the consequences of their deletion on testosterone production, steroidogenic gene expression, spermatogenesis and fertility. Taken together, these studies should unearth previously unsuspected mechanisms of regulation of testosterone synthesis, and may provide insight into both the etiology and potential therapies for testosterone insufficiency.