Stem Cell Renewal and Differentiation in Spermatogenesis

描述（由申请人提供）：对引导干细胞行为的电路有浓厚的兴趣。虽然生态位对许多组织特异性干细胞的行为至关重要，但人们尚不清楚生态位是如何在组织中指定和组装的，以及它是如何控制干细胞池的。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。这一建议解决了如何指定，组织和功能的小生境，并利用了最广为人知的干细胞小生境系统之一，果蝇的睾丸。在这里，一小群细胞（中枢细胞）作为生态位的一部分，导致邻近细胞信号通路的激活。通过这种方式，附近的体细胞接受囊肿干细胞命运（CySC），而附近的生殖系细胞，与这些CySC混合，接受生殖系干细胞命运（GSC）。中枢的形成，以及随之而来的干细胞附着，是促性腺发生的主要建筑事件。中心细胞在体细胞性腺前体（sgp）中的指定和放置产生了一个前锚定的增殖中心，该中心将以极化方式驱动精子发生。为了产生这种极性，前中心细胞的一个子集通过形成性腺的生殖细胞环境迁移，并经历间质到上皮的转变（MET），然后才作为生态位细胞。最后，关键的自我更新信号由中枢细胞和CySCs表达的bmp传递。第一个Aim结合了实时成像和功能丧失和功能获得研究来探索细胞骨架对中心前细胞迁移的控制，以及生态位形成所必需的间充质到上皮的转变。第二个目标是关注Zfh1，这是一种转录调节因子，是CySC自我更新和CySCs如何作为GSC更新的小生境细胞的关键。Zfh1的靶点将被识别和功能分析。这将确定对CySC自我更新、GSCs更新信号的产生和MET控制重要的基因。

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.