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节NIH 1 R01 GM080501成人干细胞在整个生命过程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用于再生医学的潜力以及理解癌症的起源和生物学的关键。我们建议调查如何与当地环境的干细胞龛维持种群的生殖系干细胞在果蝇睾丸，一个强大的系统，在体内研究成人干细胞的背景下，他们的龛。在以前的资助周期中，我们发现睾丸干细胞龛中的体细胞支持细胞提供了一个调节干细胞自我更新和分化的关键微环境，并且生殖系干细胞（GSC）朝向该龛定向以建立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，来自体细胞中枢的细胞因子样信号激活GSC及其伴侣体细胞囊肿干细胞（CySC）中的转录因子STAT，并且激活的STAT对于维持CySC身份和GSC附着于中枢至关重要。CySC是GSC生态位的重要组成部分，可以将GSC维持在远离枢纽的异位部位。我们还发现，生殖细胞需要一个“去分化”的信号，从体细胞囊肿细胞退出无限的干细胞增殖，并进入精原程序的有限的运输放大（TA）分裂，然后分化。这些发现强调了来自小生境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细胞的及时转变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的系统和工具来识别调节干细胞行为的分子电路，以响应来自小生境的线索。我们将研究GSC如何附着并朝向枢纽，以及这种正常行为如何通过激活转录因子STAT由枢纽的Upd信号控制。我们将研究CySC是否通过发送“自我更新”信号或阻断“去分化”信号来维持GSC，并测试候选信号传导机制和调节因子，以了解生态位如何调节干细胞命运以及同一生态位内两种干细胞类型的作用如何协调。最后，我们将测试的模型，激活EGFR在体细胞囊肿细胞的信号，从成囊细胞下调CySC程序，允许及时切换从干细胞到祖细胞状态的生殖系和体细胞谱系。

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.