Planar Cell Polarity and the Cytoskeleton

平面细胞极性（PCP）信号调节上皮平面内极性的建立。信号传导的结果是多种多样的，如细胞命运的决定，不对称但高度排列的结构的产生（例如人内耳的立体纤毛或苍蝇翅膀上的毛发），或脊椎动物原肠胚形成过程中细胞在会聚延伸过程中的定向迁移。PCP受非规范的Fz/平面细胞极性通路控制，其中Wnt信号通过卷曲受体导致核反应，以及由Rho激酶介导的细胞骨架变化。PCP信号最初是在果蝇中发现的，并且研究得最好，主要是因为果蝇作为模型系统的多功能性，因为它的遗传冗余度低。在果蝇中，PCP对肌动蛋白翼毛的定向和眼内小眼的极化至关重要，这需要光感受器细胞群的高度协调运动（小眼旋转）。因此，果蝇中PCP信号传导和脊椎动物中趋同扩展的关键是细胞骨架重排和细胞迁移过程。这些过程的核心是Rho激酶（果蝇中的Rock， Drok），其突变或显性阴性形式分别导致果蝇和鱼类的ommatidial旋转/迁移和收敛延伸/神经管缺陷。该建议侧重于生物化学和遗传方法来鉴定和表征新的PCP成分和细胞骨架的调节因子。在基因组宽屏幕中，我们使用磷酸化诱导的凝胶转移试验确定了直接的Drok底物。我们将使用体内RNAi，突变分析和已知途径成分的遗传相互作用分析来表征候选药物。我们拟从Rho激酶和PCP信号转导方面详细研究它们的作用机制。使用上述策略来找出PCP信号传导的机制方面，并发现与细胞反应的新联系，将扩展我们对早期发育的了解。由于PCP基因网络在苍蝇、海鞘和哺乳动物等多种生物中都有保存，因此本研究对了解PCP的建立及其在脊椎动物中的相关形态发生过程具有直接意义。公共卫生相关性：果蝇和人类细胞之间的通讯机制是保守的，非常相似。我们利用果蝇来研究细胞通讯如何影响细胞运动。缺乏这种交流可导致严重的出生缺陷，如神经管打开（如脊柱裂）。

DESCRIPTION (provided by applicant): Planar cell polarity and the cytoskeleton Planar cell polarity (PCP) signaling regulates the establishment of polarity within the plane of an epithelium. The results of signaling are as diverse as the determination of cell fates, the generation of asymmetric, but highly aligned structures (e.g. stereocilia in the human inner ear or hairs on a fly wing), or the directional migration of cells during convergent extension during vertebrate gastrulation. PCP is governed by the non-canonical Fz/Planar Cell Polarity pathway, in which a Wnt signals through a Frizzled receptor leading to nuclear responses, as well as to cytoskeletal changes mediated by Rho Kinase. PCP signaling was originally discovered and is best studied in Drosophila, mainly because of the versatility of the fly as model system due to its low genetic redundancy. In Drosophila, PCP is essential for the orientation of the actin wing hairs and the polarization of the ommatidia in the eye, requiring highly coordinated movement of groups of photoreceptor cells (ommatidial rotation). Thus, key to PCP signaling in flies, and to convergent extension in vertebrates, are cytoskeletal rearrangements and cell migration processes. Central to these processes is Rho Kinase (Rock, Drok in Drosophila), mutations in which or dominant negative forms of which lead to ommatidial rotation/migration and convergent extension/neural tube defects in flies and fish, respectively. This proposal focuses on biochemical and genetic approaches to identify and characterize new PCP components and regulators of the cytoskeleton. In a genome wide screen we identified direct Drok substrates using a phosphorylation induced gel-shift assay. We will characterize the candidates using in vivo RNAi, mutational analysis and genetic interaction assays with known pathway components. We propose to study their mechanism of action with respect to Rho Kinase and PCP signaling in detail. Using the above strategies to work out mechanistic aspects of PCP signaling as well as to discover new links to cellular responses will extend our knowledge of early development. Due to the conservation of the PCP gene network in organisms as diverse as flies, ascidians and mammals, the proposed research will be of immediate importance for the understanding of the establishment of PCP and related morphogenetic processes in vertebrates. PUBLIC HEALTH RELEVANCE: The mechanism of communication between cells of the fruitfly Drosophila and humans is well conserved and very similar. We make use of Drosophila to study how cell communication affects cell movement. Lack of such communication can lead to severe birth defects such as open neural tubes (e.g. spina bifida).