Regulation of mouse spermatogonial stem cell self-renewal

描述（由申请方提供）：精原干细胞（SSC），雄性生殖系干细胞，通过其自我更新和产生分化为精子的子细胞的能力为精子发生提供基础。这些属性使精原干细胞成为雄性持续生育力和遗传系保存的关键组成部分。小鼠SSC自我更新的信号传导由生长因子胶质细胞系源性神经营养因子（GDNF）介导，可能通过c-Ret原癌基因受体。使用这种生长因子和确定的培养基，发生小鼠SSC的长期（超过6个月）体外增殖，这已经通过细胞表面抗原标记的维持和培养的SSC在移植到受体时产生供体细胞衍生的精子发生和后代的能力得到证实。因此，一个独特的和强大的系统可用于研究小鼠SSC自我更新的分子机制。我们最近使用微阵列分析，以确定GDNF调节基因在高度富集的群体的SSC，提供了一个数据库的基因，可能构成的核心分子机制调节SSC的自我更新和生存。相同的生长因子和类似的分子机制可能被其他哺乳动物的干细胞使用，因为来自许多物种（例如大鼠，猪，狒狒和人）的干细胞已被证明在小鼠睾丸中增殖。此外，确定的小鼠SSC自我更新的重要分子可能有助于理解其他成体组织干细胞的机制。将利用小鼠SSC培养系统和干细胞移植技术来分析小鼠SSC自我更新的分子调控。提出的两个具体目标是：1）研究参与SSC自我更新的GDNF信号通路，和2）确定GDNF调节基因在SSC自我更新中的生物学意义。识别男性生殖系干细胞生长和分裂所需的信号将有助于理解人类男性不育症，并建立一个在体外培养或生长人类精原干细胞的系统。这种培养系统可以用于在化疗期间维持男性的干细胞，然后干细胞返回男性的睾丸以在治疗后重建生育能力。

DESCRIPTION (provided by applicant): Spermatogonial stem cells (SSCs), male germ line stem cells, provide the foundation for spermatogenesis by their ability to both self-renew and generate daughter cells, which differentiate into spermatozoa. These attributes make SSCs the key component for sustained fertility in males and the preservation of genetic lines. Signaling for mouse SSC self-renewal is mediated by the growth factor glial cell line-derived neurotrophic factor (GDNF) likely through the c-Ret proto-oncogene receptor. Using this growth factor and a defined medium, long-term (more than 6-months) in vitro proliferation of mouse SSCs occurs, which has been confirmed by maintenance of cell surface antigenic markers and ability of cultured SSCs, when transplanted to recipients, to produce donor cell-derived spermatogenesis and progeny. Thus, a unique and powerful system is available to study the molecular mechanisms of mouse SSC self-renewal. We have recently used microarray profiling to identify GDNF-regulated genes in highly enriched populations of SSCs, providing a database of genes that may constitute the core molecular machinery regulating SSC self-renewal and survival. The same growth factor and similar molecular mechanisms are likely used by other mammalian SSCs, because stem cells from many species (e.g. rat, pig, baboon and human) have been shown to proliferate in mouse testes. In addition, important molecules identified for mouse SSC self-renewal may be helpful in understanding mechanisms used by other adult tissue stem cells. The mouse SSC culture system and stem cell transplantation technique will be used to analyze the molecular regulation of mouse SSC self- renewal. The two proposed specific aims are: 1) Investigate GDNF signaling pathways involved in SSC self- renewal, and 2) Determine the biological significance of GDNF-regulated genes in SSC self-renewal. The identification of the signals required for male germ line stem cells to grow and divide will help in understanding male infertility in humans and in establishing a system to culture or grow human SSCs outside the body. Such a culture system could be used to maintain stem cells of a male during chemotherapy, and the stem cells then returned to the male's testes to reestablish fertility after therapy.