Stem Cell Renewal and Differentiation in Spermatogenesis

描述(由申请者提供)：人们对引导干细胞行为的回路非常感兴趣。虽然利基对许多组织特异性干细胞的行为是必不可少的，但人们并不清楚利基是如何在组织中指定和组装的，以及它如何控制干细胞池。了解这些相互作用对于在再生医学中使用这些细胞至关重要。这项建议阐述了壁龛是如何被指定、组织和发挥作用的，并利用了最为人所知的干细胞-壁龛系统之一--果蝇睾丸。在这里，一小群细胞(中枢细胞)作为生态位的一部分，导致相邻细胞中信号通路的激活。通过这种方式，附近的体细胞承担着孢子干细胞的命运(CySC)，而附近的生殖系细胞与这些CySCs混合在一起，承担着生殖系干细胞的命运(GSC)。中枢的形成和随之而来的干细胞的附着是性腺发生的主要结构事件。中枢细胞在体细胞性腺前体(SGPS)之间的指定和放置产生一个向前锚定的增殖中心，该中心将以极化的方式驱动精子发生。为了产生这种极性，前中枢细胞的子集通过形成性腺的生殖细胞环境迁移，并经历间充质到上皮性细胞的转变(MET)，然后才起到利基细胞的作用。最后，关键的自我更新信号由中枢细胞和细胞周期干细胞表达的BMP传递。第一个目的是结合活体成像和功能丧失和功能获得的研究来探索细胞骨架对中枢前细胞迁移的控制，以及形成生态位所必需的间充质到上皮的转变。第二个目标集中在Zfh1，一个转录调节因子，它是CySC自我更新的关键，以及CySC如何作为GSC更新的利基细胞。将对Zfh1的目标进行识别和功能分析。这将定义对CySC自我更新、为GSC产生更新信号和MET控制重要的基因。 公共卫生相关性：对人类健康的潜在影响：人们对引导干细胞行为的回路非常感兴趣。了解利基-干细胞相互作用是解开在再生医学中使用这些细胞所必需的电路的核心。因此， 这项建议涉及干细胞-生态位生物学在概念上的三个重要方面：如何指定、组织和发挥作用。

DESCRIPTION (provided by applicant): There is intense interest in the circuits that guide stem cell behavior. While niches are essential to the behavior of many tissue-specific stem cells, it is not understood how the niche is specified and assembled in a tissue, and then how it executes control over the stem cell pool. Understanding these interactions will be crucial to use these cells in regenerative medicine. This proposal addresses how are niches specified, organized and function, and utilizes one of the most well-understood stem cell-niche systems, the Drosophila testis. Here, a small group of cells (hub cells) act as part of the niche, leading t the activation of signaling pathways in adjacent cells. In this way, nearby somatic cells take on cyst stem cell fate (CySC), while nearby germline cells, intermingled with these CySCs, take on germline stem cell fate (GSC). Hub formation, and the attendant attachment of stem cells, is the major architectural event of gonadogenesis. The specification and placement of hub cells among somatic gonadal precursors (SGPs) generates an anteriorly-anchored proliferation center that will drive spermatogenesis in a polarized manner. To generate that polarity, a subset of pre-hub cells migrates through the germ cell milieu of the forming gonad, and undergoes a mesenchymal-to-epithelial transition (MET), only then acting as niche cells. Finally, the key self-renewal signal is delivered by BMPs expressed from both hub cells and CySCs. The first Aim uses a combination of live-imaging and loss- and gain-of-function studies to explore cytoskeletal control of pre-hub cell migration, and the mesenchymal-to-epithelial transition necessary for niche formation. A second Aim focuses on Zfh1, a transcriptional regulator which is key to CySC self- renewal and to how CySCs act as niche cells for GSC renewal. Targets of Zfh1 will be indentified and analyzed functionally. This will define genes important for CySC self- renewal, for the production of renewal signals for GSCs, and for the control of MET. PUBLIC HEALTH RELEVANCE: Potential implications for human health: There is intense interest in the circuits that guide stem cell behavior. Understanding niche-stem cell interactions is central to unraveling the circuitry necessary to use these cells in regenerative medicine. Thus, this proposal addresses these three conceptually significant facets of stem cell-niche biology: how are niches specified, organized and function.