Control of Stem Cell Fate in Drosophila Spermatogenesis

描述（由申请人提供）：尽管精原干细胞对生殖至关重要，但对其调控知之甚少。环境和内在因素对干细胞的建立和维持至关重要，但在哺乳动物系统中系统地识别这些因素极具挑战性。我们使用果蝇精子发生作为模型系统，因为它与哺乳动物系统相似，但我们可以精确地定位干细胞，并从基因上操纵它们的微环境。先前的资助使我们能够发现控制果蝇精原干细胞自我更新的分子机制。生殖系干细胞（GSCs）被固定在一组被称为中枢的体细胞支持细胞周围。该中心产生一种配体，激活邻近生殖细胞中的Jak-Stat，指示它们保持干细胞状态。从中心移开的子体是有区别的。基于从这些调查结果中获得的初步数据，在这次更新中，我们解决了三个基本问题。在Aim 1中，我们通过描述胚胎睾丸中的生殖细胞行为和Jak-Stat活性，进一步研究了Jak-Stat信号将GSC前体（原始生殖细胞）转化为GSC的初步数据，然后利用遗传学方法确定该途径在GSC建立中的作用。在Aim 2中，我们扩展了成人干细胞中Jak-Stat信号的研究。虽然GSCs需要直接激活Stat，但没有对SSCs进行测试。在Aim 2a中，我们确定Jak-Stat信号是否直接或间接地需要GSC维护。在Aim 2b中，我们继续我们广泛的初步数据，表明socs36E， Jak-Stat信号的靶点和抑制剂，维持睾丸中的GSCs。我们将完成socs36E等位基因的表征，然后我们将确定socs36E是否直接或间接需要进行GSC维护。最后，由于Stat在GSCs（也可能是SSCs）中的靶标可能是干细胞命运的内在决定因素，而中枢细胞中的靶标可能调节中枢细胞的功能，我们将在Aim 3中识别这些靶标，并使用遗传方法测试它们在干细胞维持中的作用。总之，这项工作将提供调控干细胞建立和维持的分子机制的基本见解，这对于开发干细胞在再生医学中的潜在治疗用途具有重要意义。

DESCRIPTION (provided by applicant): Although spermatogonial stem cells are essential for reproduction, little is known about their regulation. Environmental and intrinsic factors are crucial for stem cell establishment and maintenance, but systematically identifying these factors is extremely challenging in mammalian systems. We use Drosophila spermatogenesis as a model system, since it parallels mammalian systems, yet we can precisely locate the stem cells, and manipulate their microenvironment genetically. Prior funding enabled us to discover the molecular mechanism controlling Drosophila spermatogonial stem cell self-renewal. Germline stem cells (GSCs) are anchored around a cluster of somatic support cells called the hub. The hub produces a ligand that activates Jak-Stat in adjacent germ cells, instructing them to remain as stem cells. Daughters displaced away from the hub differentiate. Building on preliminary data derived from these findings, in this renewal we address three fundamental questions. In Aim 1, we pursue our preliminary data suggesting that Jak-Stat signaling converts GSC precursors (primordial germ cells) into GSCs by characterizing germ cell behavior and Jak-Stat activity in the embryonic testis, then using genetics to determine the role of this pathway in GSC establishment. In Aim 2, we extend our studies of Jak-Stat signaling in adult stem cells. Although GSCs require direct activation of Stat, this was not tested for SSCs. In Aim 2a, we determine if Jak-Stat signaling is directly or indirectly required for GSC maintenance. In Aim 2b, we pursue our extensive preliminary data indicating that socs36E, a target and inhibitor of Jak-Stat signaling, maintains GSCs in the testis. We will complete the characterization of our socs36E alleles, then we will determine if socs36E is directly or indirectly required for GSC maintenance. Finally, since targets of Stat in GSCs (& possibly SSCs) may be intrinsic determinants of stem cell fate, while targets in hub cells may regulate hub cell function, we will identify these targets, and test them for roles in stem cell maintenance using genetic approaches in Aim 3. Together this work will provide fundamental insight into the molecular mechanisms that regulate stem cell establishment and maintenance, which is of great importance towards developing potential therapeutic uses of stem cells in regenerative medicine.