Wnt Pathway Regulation of Lens Polarity

描述（由申请人提供）：透镜极性中的Wnt通路已知Wnt通路在发育和疾病的许多方面具有关键作用。这种竞争性更新应用的长期目标是理解Wnt途径在发育期间调节上皮细胞向纤维细胞转变和透镜极性中的作用。初步研究表明，当在透镜谱系中消除Wnt配体的产生时，显著地，透镜上皮细胞分化成透镜纤维细胞。相比之下，当Wnt途径转录因子Tcf 3在早期透镜中有条件地缺失时，存在相反的反应，其中纤维细胞不能分化。这些令人惊讶的发现强调了Wnt/2-连环蛋白途径对于调节透镜发育和建立限定透镜极性的前上皮-后纤维细胞模式的重要性。该途径在透镜发育中的功能对于透镜生物学以及可能对于上皮不被维持的病理生理学具有重要意义。我们的中心假设是Wnt/2-catenin途径调节上皮细胞向纤维细胞的转变以建立透镜极性。为了验证这一假设的有效性，我们提出了三个目标。1.确定对建立透镜极性至关重要的Wnt配体的来源。我们产生的小鼠Wntless等位基因是非常有价值的，因为它是所有Wnt配体活性所必需的，因此解决了当表达多个配体时如何产生配体功能丧失的问题。我们将利用这个等位基因，结合不同的cre重组酶系，以确定来源，或来源的Wnt配体的上皮细胞到纤维细胞的过渡和透镜极性的关键。2.确定非经典Wnt配体是否提供透镜上皮Wnt反应的负反馈调节。最近已经表明，一些Wnt配体仅在非经典途径中起作用，并且此外，它们可以通过阻止Lrp 5/6共受体与Frizzleds的缔合来阻断Wnt/2-连环蛋白信号传导。当结合观察到几种非典型配体在透镜纤维细胞中表达时，这表明它们可能在纤维细胞与上皮接触后下调Wnt/2-连环蛋白信号传导。3：确定透镜复极化是否需要经典Wnt通路的再激活。1963年，库伦布尔和库伦布尔进行了一个现在经典的实验，表明一个反向的小鸡透镜（上皮细胞面对视网膜）将在10天内重新激活。如我们的初步数据所示，Wnt通路的破坏破坏了透镜极性，表明Wnt通路可能在再极化期间被重新激活。我们将通过监测和调节鸡透镜复极化过程中的Wnt通路来检验这一假设。结合起来，这些研究将提供对Wnt通路在透镜发育中的作用的深入评估，总体而言，这是我们对这个独特器官的理解向前迈出的重要一步。

DESCRIPTION (provided by applicant): Wnt pathways in lens polarity Wnt pathways are known to have a critical role in many aspects of development and disease. The long term goal of this competitive renewal application is an understanding of the role of Wnt pathways in regulating the epithelial to fiber cell transition and lens polarity during development. Preliminary studies show that when production of Wnt ligands is eliminated in the lens lineage, remarkably, lens epithelial cells differentiate into lens fiber cells. By contrast, when the Wnt pathway transcription factor Tcf3 is deleted conditionally in early lens, there is an opposite response where fiber cells fail to differentiate. These are surprising findings that underscore the importance of the Wnt/2-catenin pathway for regulating lens development and establishing the anterior epithelium-posterior fiber cell pattern that defines lens polarity. The function of this pathway in lens development has important implications for lens biology and perhaps for pathophysiologies where the epithelium is not maintained. Our central hypothesis is that The Wnt/2-catenin pathway regulates the epithelial-to-fiber cell transition to establish lens polarity. To investigate the validity of this hypothesis, we propose three Aims. 1. To determine the source of Wnt ligands crucial for establishing lens polarity. The mouse Wntless allele we have generated is very valuable because it is required for the activity of all Wnt ligands and thus solves the problem of how to generate a ligand loss-of-function when multiple ligands are expressed. We will take advantage of this allele, combined with different cre recombinase lines, to identify the source, or sources of Wnt ligands critical for the epithelial-to-fiber cell transition and lens polarity. 2. To determine whether non-canonical Wnt ligands provide negative-feedback regulation of the lens epithelial Wnt response. It has recently been shown that some Wnt ligands function only in the non-canonical pathways and furthermore, that they can block Wnt/2-catenin signaling by preventing the association of the Lrp5/6 co-receptors with Frizzleds. When coupled with the observation that several non-canonical ligands are expressed in lens fiber cells, this suggests that they may serve to down-regulate Wnt/2-catenin signaling after fiber cells have made contact with the epithelium. 3: To determine whether lens repolarization requires reactivation of the canonical Wnt pathway. In 1963, Coulombre and Coulombre performed the now classical experiment showing that a reversed chick lens (epithelium facing the retina) would re-polarize over the course of 10 days. As shown in our preliminary data, disruption of the Wnt pathway disrupts lens polarity suggesting that the Wnt pathway may be re-activated during re-polarization. We will test this hypothesis by monitoring and modulating the Wnt pathway during chick lens re-polarization. Combined, these studies will provide an in- depth assessment of the role of the Wnt pathway in lens development and overall, an important step forward in our understanding of this unique organ.