Wnt Pathway Regulation of Lens Polarity

描述(由申请人提供)：WNT通路在晶状体极性中的WNT通路已知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了解Wnt通路在调节发育过程中上皮细胞到纤维细胞的转变和晶状体极性方面的作用。初步研究表明，当Wnt配体的产生在晶状体谱系中被消除时，晶状体上皮细胞显著地分化为晶状体纤维细胞。相比之下，当Wnt途径转录因子Tcf3在早期晶状体中有条件地删除时，纤维细胞无法分化时会出现相反的反应。这些令人惊讶的发现强调了Wnt/2-catenin通路对于调节晶状体发育和建立定义晶状体极性的前上皮-后纤维细胞模式的重要性。这一途径在晶状体发育中的作用对晶状体生物学有重要意义，可能对上皮不能维持的病理生理学也有重要意义。我们的中心假设是，Wnt/2-catenin途径调节上皮细胞到纤维细胞的转变，以建立晶状体的极性。为了考察这一假设的有效性，我们提出了三个目标。1.确定对确定晶状体极性至关重要的Wnt配体的来源。我们产生的小鼠Wnless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，从而解决了当表达多个配体时如何产生一个配体的功能丧失的问题。我们将利用这个等位基因，结合不同的cre重组酶系，来确定Wnt配体的来源，这些配体对上皮细胞到纤维细胞的转变和晶状体的极性至关重要。2.确定非典型性Wnt配体是否对晶状体上皮Wnt反应提供负反馈调节。最近的研究表明，一些Wnt配体仅在非规范途径中发挥作用，而且它们还可以通过阻止LRP5/6辅助受体与Frizzleds的结合来阻断Wnt/2-catenin信号转导。再加上观察到在晶状体纤维细胞中有几种非规范配体的表达，这表明它们可能在纤维细胞与上皮细胞接触后下调Wnt/2-catenin信号。3：确定晶状体复极化是否需要重新激活典型的Wnt通路。1963年，Coulombre和Coulombre进行了现在的经典实验，显示反转的鸡眼晶状体(面向视网膜的上皮)将在10天内重新极化。我们的初步数据显示，Wnt通路的中断扰乱了晶状体的极性，这表明Wnt通路可能在复极化过程中被重新激活。我们将通过监测和调节小鸡晶状体复极化过程中的Wnt通路来验证这一假说。综上所述，这些研究将对Wnt通路在晶状体发育和整体上的作用提供深入的评估，这是我们对这一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.