Mechanisms regulating epithelial stem cell behaviour

上皮组织是动物和人体的中心构件。我们研究计划的长期目标是了解上皮组织如何发展、采用和维持决定器官功能的特定形状。在发育和动态平衡期间，许多上皮细胞依靠干细胞形成或更新。因此，了解上皮干细胞是如何维持的，以及它们的数量是如何调节的，以便形成正常大小和形状的上皮细胞，这是至关重要的。这项建议使用果蝇卵巢中的滤泡干细胞(FSCS)作为模型，研究控制上皮干细胞行为的分子和细胞机制。果蝇是生物学研究中的重要模型。我的实验室在使用这个模型研究上皮生物学方面有长期的经验。FSCS产生围绕生殖细胞的滤泡上皮，形成卵泡，最终产生卵子。我们已经确定了一个迄今尚未确定特征的基因okapi(Oka)，作为一种新的FSC行为调节因子。OKA是一种保守的FERM结构域蛋白质，定位于黏附连接(AJ)，黏附连接是将细胞连接在一起并影响组织生长和形成的黏附结构。我们的初步观察表明，Oka在FSCS中具有两种功能。它促进了FSC的竞争力，并限制了FSC的数量，以防止组织过度生长。我们的第一个目标是问Oka和AJ是否一起提升了FSC的竞争力。当卵巢中含有Oka突变型和野生型细胞时，Oka突变型FSCs会丢失，取而代之的是更具竞争力的野生型FSCs。AJ受损的FSCS也有类似的缺陷。鉴于Oka定位于AJs，并考虑到Oka的突变表型，我们假设Oka将AJs与竞争力联系起来。AJ的一个关键特征是它们是机械敏感结构。我们将分析Oka如何与AJ蛋白相互作用，以及机械传感是否在Oka-AJ相互作用中调节FSC行为的功能。我们的第二个目标是询问Oka是否通过河马途径限制FSC的增殖，河马途径是与AJ相关的中央生长调节因子。与在野生型细胞旁边含有Oka突变细胞的马赛克卵巢不同，完全缺乏Oka的卵巢有太多的FSCs和过多的卵泡细胞，这严重影响了卵子发生和生育。我们的初步数据表明，河马途径在Oka突变的卵巢中显示出活性降低，结果是转录共激活因子York kie进入细胞核，刺激过度增殖。因此，这一目标将解决Oka作为河马途径的一种新的调节因子来限制FSCs增殖的假设。总体而言，这项工作将阐明作为正常器官形成和功能的一个重要方面，上皮干细胞的维持和数量是如何被调节的分子机制。

Epithelial tissues are central building blocks of the animal and human body. The long-term goal of our research program is to understand how epithelial tissues develop, adopt and maintain specific shapes that determine organ function. During development and homeostasis, many epithelia rely on stem cells for their formation or renewal. It is therefore of fundamental importance to understand how epithelial stem cells are maintained and how their numbers are regulated so that epithelia of normal size and shape can form. This proposal uses the follicle stem cells (FSCs) in the ovary of the fruit fly Drosophila as a model to investigate the molecular and cellular mechanisms that govern the behaviour of epithelial stem cells. Drosophila is a key model in biological research. My laboratory has longstanding experience in using this model to study epithelial biology The FSCs give rise to the follicular epithelium that surrounds the germline cells to form a follicle, which eventually gives rise to an egg. We have identified a so far uncharacterized gene, okapi (oka), as a novel regulator of FSC behaviour. Oka is a conserved FERM domain protein that localizes to adherens junctions (AJs), adhesive structures that link cells together and affect tissue growth and form. Our preliminary observations suggest that Oka has two functions in FSCs. It promotes FSC competitiveness, and it limits the number of FSCs to prevent tissue overgrowth. Our first aim asks whether Oka together with AJs promotes FSC competitiveness. When ovaries are generated that contain oka mutant and wild-type cells, oka mutant FSCs are lost and replaced by more competitive wild-type FSCs. A similar defect was seen for FSCs with compromised AJs. Given that Oka localizes to AJs and considering oka's mutant phenotype, we hypothesize that Oka links AJs to competitiveness. One key feature of AJs is that they are mechanosensitive structures. We will analyze how Oka interacts with AJ proteins and whether mechanosensing has a function in the Oka-AJ interaction that regulates FSC behaviour. Our second aim is to ask whether Oka limits FSC proliferation through the Hippo pathway, a central growth regulator linked to AJs. In contrast to mosaic ovaries that contain oka mutant cells next to wild-type cells, ovaries that lack Oka entirely have too many FSCs and an overabundance of follicle cells, which severely compromises oogenesis and fertility. Our preliminary data suggest that the Hippo pathway shows reduced activity in oka mutant ovaries, and that as a consequence the transcriptional co-activator Yorkie enters the nucleus to stimulate excessive proliferation. This aim will therefore address the hypothesis that Oka acts to limit the proliferation of FSCs as a novel regulator of the Hippo pathway. Overall, this work will clarify the molecular mechanisms of how the maintenance and number of epithelial stem cells are regulated as an essential aspect of normal organ formation and function.