Elucidating the cytoskeletal mechanics in stem cell niche morphogenesis

项目摘要： 干细胞功能缺陷会导致肿瘤形成或组织变性，严重影响人类健康。 为了维持自我更新和分化的适当平衡，干细胞依赖于来自其自身的信号信号 生态位，这是它们所居住的微环境。必须了解错综复杂的 为揭示促进正常干细胞功能和最大限度减少干细胞缺陷的机制奠定基础 人类健康。在许多组织中，壁龛具有精确和可重现的形态。然而，没有多少是 了解生态位形态是如何控制的，或者它是如何影响生态位功能的。此项目将使用 果蝇性腺研究生态位形成的机制，结合遗传易驯化和强大的活体- 成像技术是迪纳多实验室的先驱。在这个系统中，生态位具有明确的形态定义 通过在壁龛和邻近的干细胞之间平滑的边界。这一边界进一步被称为 作为利基边缘。从功能上讲，利基在调节干细胞行为方面起着关键作用：1)它是 自我更新线索的来源，2)它限制这些线索只能进入相邻的细胞，3)它调节干细胞 细胞分裂方向。初步证据表明，光滑的利基边缘对于确保 生殖系干细胞(GSCs)合适的分裂角度，暗示了生态位结构和功能之间的联系。 此外，F-肌动蛋白和肌球蛋白II(MyoII)在壁龛外围富含，伴随着张力， 提示肌动球蛋白的收缩能力。这个项目的一个关键目标是揭示肌动球蛋白收缩的作用。 在生态位形态形成和功能方面(目标1)。由于生态位形态发生具有高度的重复性，该项目 还将解决将F-肌动蛋白和MyoII强有力地极化到利基外围的上游机制(目标2)。 一种有趣的可能性是，贴壁的GSC施加在壁龛上的机械力诱导细胞骨架 沿着利基边缘的两极分化。初步证据表明，GSC部门需要适当的 生态位形态，众所周知，多种力量共同作用，推动主轴伸长在分裂 手机。该项目将解决这样的假设，即F-肌动蛋白和MyoII沿着壁龛外围的丰富是 由GSC纺锤体的伸长诱导，是生态位形成和功能所必需的。一种组合 转基因技术将被用来操纵肌球蛋白的收缩能力，以及抑制微管马达。 参与纺锤体的伸长。该项目可能会揭示一种反馈机制，使干细胞 塑造引导他们行为的利基，并将是首批描述塑造机制的人之一 一个实用的利基市场。该项目的培训计划包括实验室工作、会议出席、期刊俱乐部、 实验室会议、研究生小组讨论会，以及接触教学和指导角色。这项工作将是 在果蝇生物学和形态发生专家斯蒂芬·迪纳尔多博士的指导下完成， 在毕尔菲博士的共同指导下，他是肌球蛋白、肌动蛋白环形成和细胞极性方面的专家。

Project Abstract: Defects in stem cell function severely impact human health by inducing tumor formation or tissue degeneration. To maintain a proper balance of self-renewal and differentiation, stem cells rely on signaling cues from their niche, which is the microenvironment in which they reside. It is imperative to understand the intricacies that underlie niche biology to reveal mechanisms that promote normal stem cell function and minimize defects in human health. In many tissues, the niche has a precise and reproducible morphology. However, not much is known about how niche morphology is controlled or how it impacts niche function. This project will use the Drosophila gonad to study the mechanics of niche formation, combining genetic tractability with powerful live- imaging techniques pioneered in the DiNardo lab. In this system, the niche has a distinct morphology defined by a smoothened boundary between the niche and the adjacent stem cells. This boundary is further referred to as the niche periphery. Functionally, the niche plays key roles in regulating stem cell behavior: 1) it is the source for self-renewal cues, 2) it restricts access of these cues to only adjacent cells, and 3) it regulates stem cell division orientation. Preliminary evidence suggests that the smooth niche periphery is crucial to ensure proper division angles for germline stem cells (GSCs), suggesting a link between niche structure and function. Furthermore, F-actin and Myosin II (MyoII) are enriched at the niche periphery, accompanied by tensile forces, suggestive of actomyosin contractility. A key goal for this project is to unveil the role of actomyosin contractility in niche morphogenesis and function (Aim 1). Since niche morphogenesis is highly reproducible, this project will also address upstream mechanisms that robustly polarize F-actin and MyoII to the niche periphery (Aim 2). An intriguing possibility is that mechanical forces exerted on the niche by adherent GSCs induce cytoskeletal polarization along the niche periphery. Preliminary evidence suggests GSC divisions are required for proper niche morphology, and it is known that multiple forces act in concert to drive spindle elongation in a dividing cell. This project will address the Hypothesis that F-actin and MyoII enrichment along the niche periphery is induced by GSC spindle elongation, and is necessary for niche formation and function. A combination of transgenic techniques will be used to manipulate actomyosin contractility, as well as inhibit microtubule motors involved in spindle elongation. This project will potentially unveil a feedback mechanism where stem cells shape the niche that guides their behavior, and will be among the first to describe the mechanisms of shaping a functional niche. The training plan for this project consists of lab work, conference attendance, journal clubs, lab meetings, graduate group seminars, and exposure to teaching and mentoring roles. This work will be completed under the mentorship of Dr. Stephen DiNardo, an expert in Drosophila biology and morphogenesis, with co-mentorship by Dr. Erfei Bi, an expert on Myosin, actomyosin ring formation, and cell polarity.