Wnt Pathway Regulation of Lens Polarity

描述（由申请人提供）：已知晶状体极性中的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了解Wnt通路在发育过程中调节上皮细胞向纤维细胞转变和晶状体极性中的作用。初步研究表明，当晶状体谱系中Wnt配体的产生被消除时，晶状体上皮细胞显著分化为晶状体纤维细胞。相比之下，当Wnt通路转录因子Tcf3在晶状体早期被有条件地删除时，纤维细胞无法分化则会出现相反的反应。这些令人惊讶的发现强调了Wnt/2-catenin通路在调节晶状体发育和建立决定晶状体极性的前上皮-后纤维细胞模式中的重要性。该通路在晶状体发育中的功能对晶状体生物学和可能对上皮不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通路调节上皮细胞到纤维细胞的转变以建立晶状体极性。为了研究这一假设的有效性，我们提出了三个目标。确定Wnt配体的来源对建立透镜极性至关重要。我们所产生的小鼠Wnt - less等位基因非常有价值，因为它是所有Wnt配体活性所必需的，从而解决了如何在多个配体表达时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，来鉴定对上皮细胞向纤维细胞转变和晶状体极性至关重要的Wnt配体的来源。2. 确定非规范Wnt配体是否对晶状体上皮Wnt反应提供负反馈调节。最近有研究表明，一些Wnt配体仅在非规范途径中起作用，此外，它们可以通过阻止Lrp5/6共受体与Frizzleds的结合来阻断Wnt/2-catenin信号传导。当观察到晶状体纤维细胞中表达了几种非规范配体时，这表明它们可能在纤维细胞与上皮接触后下调Wnt/2-catenin信号传导。3：确定晶状体复极化是否需要经典Wnt通路的再激活。1963年，库伦布雷和库伦布雷进行了现在的经典实验，表明一个反向的小鸡晶状体（面向视网膜的上皮细胞）在10天的过程中会重新极化。正如我们的初步数据所示，Wnt通路的破坏破坏了晶状体极性，这表明Wnt通路可能在再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再极化过程中的Wnt通路来验证这一假设。综上所述，这些研究将为Wnt通路在晶状体发育中的作用提供深入的评估，这是我们了解这一独特器官的重要一步。

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. PUBLIC HEALTH RELEVANCE: In this application, we propose the study a cell-cell signaling pathway, the so-called Wnt pathway that is known to be critical for embryonic development, for tissue homeostasis and for the development of tumors. We will determine whether the Wnt pathway is responsible for determining the orientation of the lens within the eye and thus, whether this pathway is important for the unique optical capability of this organ.