Mechano-sensitive control of intestinal stem cell divisions in Drosophila.

描述(由申请人提供)：肠上皮的更新需要在祖细胞分裂和分化细胞丢失之间取得平衡。维持分配-损失平衡对消化健康是必不可少的，而它的破坏是许多肠道病理的特征。分裂-丢失平衡涉及作用于上皮细胞的反馈信号；然而，这些信号的分子性质在很大程度上是未知的。我们的长期目标是了解引起活体肠道细胞时空动力学的过程。为了支持这一目标，该提案的目标是研究协调干细胞分裂和上皮细胞对新细胞的需求的机械敏感机制。这些研究将利用成年果蝇肠道的易驯养性，其简单的干细胞谱系和先进的遗传工具使精确的机械研究成为可能。我们之前已经证明，果蝇的肠道表现出干细胞驱动的、可逆的对增加的食物负荷的生长反应(O‘Brien等人，Cell 2011)。我们实验室的初步证据表明，干细胞分裂率与肠道扩张程度之间存在相关性。这种相关性让人想起上皮细胞培养中对密度敏感的增殖，这是一种通过黏附受体E-钙粘素和转录因子YAP进行机械转导控制的集合性细胞行为。在这里，我们将检验这样一种假设，即当肠道细胞稀少时，类似的机械敏感信号会刺激肠道干细胞分裂。具体地说，我们将(1)确定E-钙粘蛋白和YAP在肠道扩张过程中对生态位细胞和非生态位细胞的机械敏感性，以及(2)阐明E-钙粘素和YAP在密度敏感分裂控制中的生态位和非生态位角色。这些目标的实现可能会确定一条机械敏感的途径，将肠细胞密度与干细胞分裂联系起来，为肠道更新的动态平衡控制提供基本的洞察。我们提出的工作具有重要意义，因为关于细胞丢失和生产是如何协调的知识可能会产生未来的治疗策略，以加强肠道修复和再生。我们的方法是创新的，因为它在密度敏感的增殖和动态平衡的组织更新之间得出了一个新的概念联系，因为它利用了一个新兴的实验系统的独特属性。最后，来自这些研究的数据将为详细的、R01水平的肠道更新和重塑的机制生物学研究提供基础。

DESCRIPTION (provided by applicant): Renewal of the intestinal epithelium requires a balance between progenitor cell divisions and differentiated cell loss. Maintaining division-loss balance is essential for digestive health, while its disruption characterizes numerous intestinal pathologies. Division-loss balance involves feedback signals that act within the epithelium; however, the molecular nature of these signals is largely unknown. Our long-range goal is to understand the processes that give rise to the spatiotemporal dynamics of intestinal cells in vivo. Supporting this goal, the objective of this proposal is to investigate mechano-sensitive mechanisms that coordinate stem cell divisions with the epithelium's need for new cells. These studies will exploit the tractability of the adult Drosophila intestine, whose simple stem cell lineage and advanced genetic tools enable precise mechanistic investigation. We have previously shown that the Drosophila intestine exhibits a stem cell driven, reversible growth response to increased dietary load (O'Brien et al., Cell 2011). Preliminary evidence from our lab suggests a correlation between stem cell division rate and the degree of intestinal distention. This correlation is reminiscent of density-sensitive proliferation in epithelial culture, a collectve cell behavior controlled by mechanotransduction through the adhesion receptor E-cadherin and the transcription factor YAP. Here, we will examine the hypothesis that analogous mechano-sensitive signals stimulate intestinal stem cell divisions when enterocytes are sparse. Specifically, we will (1) determine the mechano-sensitivity of E-cadherin and YAP in niche and non-niche cells during intestinal distention, and (2) elucidate the niche- and non-niche roles of E-cadherin and YAP in density-sensitive division control. Accomplishment of these aims may identify a mechano-sensitive pathway that links enterocyte density to stem cell divisions, providing basic insight into homeostatic control of intestinal renewal. Our proposed work is significant because knowledge of how cell loss and production are coordinated may engender future therapeutic strategies to enhance intestinal repair and regeneration. Our approach is innovative because it draws a novel conceptual link between density-sensitive proliferation and homeostatic tissue renewal, and because it exploits the unique attributes of an emerging experimental system. Finally, data from these studies will provide the foundation for a detailed, R01-level investigation of the mechanobiology of intestinal renewal and remodeling.