Schmidt Jonathan A, Avarbock Mary R, Tobias John W, Brinster Ralph L
Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Biol Reprod. 2009 Jul;81(1):56-66. doi: 10.1095/biolreprod.108.075358. Epub 2009 Apr 1.
Spermatogonial stem cells (SSCs) provide the foundation for spermatogenesis throughout the life of a male. Because SSCs of many species can colonize the mouse testis, and glial cell line-derived neurotrophic factor (GDNF) is responsible for stimulating SSC self-renewal in rodents, we reasoned that molecular mechanisms of SSC self-renewal are similar across species. GDNF-regulated genes have been identified in mouse SSCs; however, downstream targets of GDNF are unknown in other species. The objective of this work was to identify GDNF-regulated genes in rat SSCs and to define the biological significance of these genes for rat SSC self-renewal. We conducted microarray analysis on cultured rat germ cells enriched for SSCs in the presence and absence of GDNF. Many GDNF-regulated genes were identified, most notably, Bcl6b and Etv5, which are important for mouse SSC self-renewal. Bcl6b was the most highly regulated gene in both the rat and mouse. Additionally, we identified three novel GDNF-regulated genes in rat SSCs: Bhlhe40, Hoxc4, and Tec. Small interfering RNA treatment for Bcl6b, Etv5, Bhlhe40, Hoxc4, and Tec resulted in a decrease in SSC number, as determined by transplantation, without a change in total cell number within the culture. These data indicate that, like in the mouse SSC, Bcl6b and Etv5 are important for rat SSC self-renewal, suggesting that these genes may be important for SSCs in all mammals. Furthermore, identification of three novel GDNF-regulated genes in the rat SSC extends our knowledge of SSC activity and broadens the foundation for understanding this process in higher species, including humans.
精原干细胞（SSCs）为雄性一生的精子发生提供了基础。由于许多物种的SSCs能够在小鼠睾丸中定植，并且胶质细胞系衍生的神经营养因子（GDNF）负责刺激啮齿动物的SSC自我更新，我们推测SSC自我更新的分子机制在物种间是相似的。在小鼠SSCs中已经鉴定出GDNF调节的基因；然而，GDNF在其他物种中的下游靶点尚不清楚。这项工作的目的是鉴定大鼠SSCs中GDNF调节的基因，并确定这些基因对大鼠SSC自我更新的生物学意义。我们对在有或没有GDNF存在的情况下富集了SSCs的培养大鼠生殖细胞进行了微阵列分析。鉴定出了许多GDNF调节的基因，最显著的是Bcl6b和Etv5，它们对小鼠SSC自我更新很重要。Bcl6b是大鼠和小鼠中调节程度最高的基因。此外，我们在大鼠SSCs中鉴定出三个新的GDNF调节基因：Bhlhe40、Hoxc4和Tec。对Bcl6b、Etv5、Bhlhe40、Hoxc4和Tec进行小干扰RNA处理后，通过移植确定SSC数量减少，而培养物中的总细胞数没有变化。这些数据表明，与小鼠SSC一样，Bcl6b和Etv5对大鼠SSC自我更新很重要，这表明这些基因可能对所有哺乳动物的SSCs都很重要。此外，在大鼠SSC中鉴定出三个新的GDNF调节基因扩展了我们对SSC活性的认识，并拓宽了理解包括人类在内的高等物种这一过程的基础。
