Regulation of Stem Cell Self-Renewal and Differentiation

描述（由申请人提供）：干细胞自我更新和分化的调控NIH 1 R01 GM080501成体干细胞在整个生命中都需要补充分化的细胞和修复受损的组织。维持和控制成体干细胞群体的分子机制是利用成体干细胞在再生医学中的潜力以及理解癌症的发生和生物学的关键。我们建议研究与干细胞生态位局部环境的相互作用如何维持生殖系干细胞在果蝇睾丸中的种群，这是一个在其生态位背景下研究体内成体干细胞的强大系统。在之前的资助周期中，我们发现睾丸干细胞生态位中的体细胞支持细胞提供了一个关键的微环境，可以调节干细胞的自我更新和分化，并且生殖系干细胞（GSCs）朝向这个生态位建立一个定型的有丝分裂纺锤体，确保GSC分裂的正常不对称结果。我们发现来自体细胞枢纽的细胞因子样信号激活了GSCs及其伴侣体细胞囊肿干细胞（CySCs）中的转录因子STAT，激活STAT对于维持CySC身份和GSC与枢纽的附着至关重要。CySCs是GSC生态位的重要组成部分，可以维持GSC在远离枢纽的异位位置。我们还发现，生殖细胞需要来自体细胞囊肿细胞的“去分化”信号，才能退出无限制的干细胞增殖，进入有限转运扩增（TA）分裂和分化的精原程序。这些发现强调了来自生态位的信号如何调节干细胞自我更新的新模型，其中从干细胞到TA细胞的及时过渡是通过抵消自我更新和分化信号之间的平衡来编排的。我们现在建议利用我们已经建立的强大系统和工具来识别调节干细胞行为的分子电路，以响应来自生态位的提示。我们将研究如何gsc附加和东方向中心如何正常行为由乌利希期刊指南信号控制中心通过激活的转录因子统计。我们将调查是否CySCs保持gsc通过发送一个“自我更新”信号或阻止“去分化”信号和测试候选人信号机制和监管机构了解利基调节干细胞的命运和两种干细胞的行为如何在相同的利基协调。最后，我们将测试体细胞囊肿细胞中EGFR的激活模型，通过囊胚细胞的信号下调CySC程序，允许在生殖系和体细胞谱系中及时从干细胞状态切换到祖细胞状态。

DESCRIPTION (provided by applicant): Regulation of Stem Cell Self-renewal and Differentiation NIH 1 R01 GM080501 Adult stem cells are required throughout life to replenish differentiated cells and repair damaged tissue. The molecular mechanisms that maintain and keep in check adult stem cell populations are key for harnessing the potential of adult stem cells for regenerative medicine as well as understanding the genesis and biology of cancer. We propose to investigate how interactions with the local environment of the stem cell niche maintain populations of germ line stem cells in the Drosophila testis, a powerful system for study of adult stem cells in vivo in the context of their niche. In previous funding cycles, we discovered that somatic support cells in the testis stem cell niche provide a crucial microenvironment that regulates both stem cell self renewal and differentiation, and that germ line stem cells (GSCs) orient toward this niche to set up a stereotyped mitotic spindle, ensuring the normally asymmetric outcome of GSC divisions. We showed that a cytokine like signal from the somatic hub activates the transcription factor STAT in GSCs and their partner somatic cyst stem cells (CySCs) and that activated STAT is critical for maintenance of CySC identity and GSC attachment to the hub. CySCs are an important component of the GSC niche and can maintain GSCs in ectopic sites away from the hub. We also found that germ cells require a "go differentiate" signal from somatic cyst cells to exit limitless stem cell proliferation and enter the spermatogonial program of limited transit amplifying (TA) divisions then differentiation. These findings highlight a new model for how signals from the niche regulate stem cell self- renewal, in which timely transition from stem to TA cell is choreographed by a balance between counteracting self-renewal and differentiation signals. We now propose to utilize the powerful system and tools we have established to identify the molecular circuitry that regulates stem cell behavior in response to cues from the niche. We will investigate how GSCs attach to and orient toward the hub and how this normal behavior is controlled by the Upd signal from the hub through activation of the transcription factor STAT. We will investigate whether CySCs maintain GSCs by sending a "self renew" signal or blocking a "go differentiate" signal and test candidate signaling mechanisms and regulators to understand how the niche regulates stem cell fate and how the actions of two stem cell types within the same niche are coordinated. Finally, we will test the model that activation of the EGFR in somatic cyst cells by a signal from cystoblasts downregulates the CySC program, allowing a timely switch from stem cell to progenitor state in both the germ line and somatic lineages.