Center for Reproductive Biology, School of Molecular Biosciences, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA.
Biol Reprod. 2012 May 31;86(5):164, 1-11. doi: 10.1095/biolreprod.111.097386. Print 2012 May.
Spermatogenesis relies on coordinated differentiation of stem and progenitor spermatogonia, and the transcription factor STAT3 is essential for this process in mammals. Here we studied the THY1+ spermatogonial population in mouse testes, which contains spermatogonial stem cells (SSC) and non-stem cell progenitor spermatogonia, to further define the downstream mechanism regulating differentiation. Transcript abundance for the bHLH transcription factor Neurog3 was found to be significantly reduced upon transient inhibition of STAT3 signaling in these cells and exposure to GDNF, a key growth factor regulating self-renewal of SSCs, suppressed activation of STAT3 and in accordance Neurog3 gene expression. Moreover, STAT3 was found to bind the distal Neurog3 promoter/enhancer region in THY1+ spermatogonia and regulate transcription. Transient inhibition of Neurog3 expression in cultures of proliferating THY1+ spermatogonia increased stem cell content after several self-renewal cycles without effecting overall proliferation of the cells, indicating impaired differentiation of SSCs to produce progenitor spermatogonia. Furthermore, cultured THY1+ spermatogonia with induced deficiency of Neurog3 were found to be incapable of differentiation in vivo following transplantation into testes of recipient mice. Collectively, these results establish a mechanism by which activation of STAT3 regulates the expression of NEUROG3 to subsequently drive differentiation of SSC and progenitor spermatogonia in the mammalian germline.
精子发生依赖于干细胞和祖细胞精原细胞的协调分化，而转录因子 STAT3 对于哺乳动物的这个过程是必不可少的。在这里，我们研究了小鼠睾丸中的 THY1+精原细胞群体，其中包含精原干细胞（SSC）和非干细胞祖细胞精原细胞，以进一步定义调节分化的下游机制。发现在这些细胞中瞬时抑制 STAT3 信号和暴露于 GDNF（一种调节 SSC 自我更新的关键生长因子）时，bHLH 转录因子 Neurog3 的转录丰度显著降低，并且抑制了 STAT3 的激活和相应的 Neurog3 基因表达。此外，发现 STAT3 结合在 THY1+精原细胞中的 Neurog3 启动子/增强子区域，并调节转录。在增殖的 THY1+精原细胞培养物中瞬时抑制 Neurog3 的表达会在几个自我更新周期后增加干细胞含量，而不会影响细胞的整体增殖，表明 SSC 的分化受损，无法产生祖细胞精原细胞。此外，发现经诱导缺乏 Neurog3 的培养 THY1+精原细胞在移植到受体小鼠的睾丸中后无法进行体内分化。总之，这些结果建立了一种机制，即 STAT3 的激活调节 NEUROG3 的表达，随后驱动哺乳动物生殖系中 SSC 和祖细胞精原细胞的分化。
