Ocular defects caused by TCF8/Zfhx1a mutations

描述（由申请人提供）：本工作的总体目标是确定导致眼前段和玻璃体血管系统中组织发育的机制。持续性增生性原发性玻璃体炎（PHPV或PFV）是由于玻璃体的胚胎脉管系统不能退化而引起的先天性眼部缺陷，并且产生继发性青光眼、白内障、视网膜脱离和玻璃体内出血。目前还没有明确的理解重叠的分子途径负责退化的原始玻璃体。我们的初步研究表明，Zfhx 1a基因在小鼠中的靶向突变导致类似于PHPV的眼部缺陷，包括角膜缺陷和虹膜角膜角化生。这是令人惊讶的，因为它表明Zfhx 1a是眼睛发育所必需的调节途径中的关键步骤。最近在后多形性角膜营养不良3（PPCD 3）家族中发现Zfhx 1a突变支持了这一点。我们建议定义Zfhx 1a缺失胚胎中的眼发育缺陷，并确定相关的分子途径。我们对这些研究的总体假设是，Zfhx 1a调节BMP介导的眼发生的一个新的关键步骤。具体目标#1将描述Zfhx 1a突变小鼠眼睛的发育缺陷。我们将确定Zfhx 1a-null和Zfhx 1a-het小鼠中PHPV的程度和时间，并表征角膜和虹膜的相关缺陷。我们将确定参与眼部缺陷的玻璃体和角膜内的细胞类型，并研究增殖率和凋亡的变化。我们将使用免疫组织化学来研究参与血管形成或退化的潜在下游基因表达的变化。在具体目标#2中，我们将使用遗传杂交来定义相关的信号通路。总之，这些实验将确定Zfhx 1a在前眼发育中的关键作用，并为未来研究Zfhx 1a通路如何与其他信号通路整合提供基础和遗传工具。这项工作的长期目标是确定用于治疗先天性眼缺陷的信号通路和基于精氨酸的疗法，包括PHPV和PPCD-3。本研究的总体长期目标是确定胎儿玻璃体血管退化和角膜发生所需的主要分子信号通路。确定导致人类眼部疾病的分子机制是一个重要的目标。鉴定指导玻璃体血管退化的多种信号通路应允许通过眼内注射治疗持久性增生性原发性玻璃体炎（PHPV）的治疗方法。PHPV是由于玻璃体的胚胎脉管系统退化失败而导致的先天性眼部缺陷。许多临床表现常与PHPV相关，包括小眼球、青光眼、前房变浅、角膜混浊、先天性白内障、缺损和视网膜变性（11-13）。即使是轻微的病例也与弱视有关。需要非常早期的治疗以防止以后的继发性缺陷。这直接关系到国家眼科研究所计划的目标，调查视觉系统的发展。

DESCRIPTION (provided by applicant): The overall goal of this work is to define the mechanisms that lead to the development of tissues in the anterior segment of the eye and the hyaloid vasculature. Persistent Hyperplastic Primary Vitreous (PHPV, or PFV) is a congenital ocular defect due to the failure of the embryonic vasculature of the vitreous to regress, and generates secondary glaucoma, cataracts, retinal detachment, and intravitreal hemorrhage. There is no clear understanding of the overlapping molecular pathways responsible for regression of the primary vitreous. Our preliminary studies indicate that targeted mutation of the Zfhx1a gene in mice causes an ocular defect similar to PHPV, and including defects of the cornea and metaplasia at the iridocorneal angle. This is surprising because it indicates that Zfhx1a is a critical step in a regulatory pathway essential for eye development. This is supported by the recent identification of Zfhx1a mutations in Posterior Polymorphous Corneal Dystrophy-3 (PPCD3) families. We propose to define the ocular developmental defects in Zfhx1a-null embryos, and identify the relevant molecular pathway(s). Our overall hypothesis for these studies is that Zfhx1a regulates a novel critical step in BMP-mediated oculogenesis. Specific Aim #1 will characterize the developmental defects of the eye in Zfhx1a-mutant mice. We will define the extent and timing of PHPV in Zfhx1a-null and Zfhx1a-het mice, and characterize associated defects of the cornea and iris. We will define the cell type(s) within the vitreous and cornea that are involved in the ocular defects, and investigate changes in proliferation rate and apoptosis. We will use immunohistochemistry to investigate changes in expression of potential downstream genes involved in vascularization or regression. In Specific Aim #2, we will use genetic crosses to define the relevant signaling pathways. Together, these experiments will define the critical role for Zfhx1a in development of the anterior eye, and provide a foundation and genetic tools for future studies on how the Zfhx1a pathway is integrated with other signaling pathways. The long-term goal of this work is to define signaling pathways and cytokine-based therapies for treatment of congenital eye defects, including PHPV and PPCD-3. The overall long term goal of this research is to define major molecular signaling pathways required for regression of the fetal hyaloid vasculature and genesis of the cornea. Defining the molecular mechanisms that contribute to ocular diseases in humans is a significant goal. Identification of multiple signaling pathways that direct the regression of hyaloid vasculature should allow a therapeutic approach to the treatment of Persistent Hyperplastic Primary Vitreous (PHPV) by intraocular injection. PHPV is a congenital ocular defect due to the failure of the embryonic vasculature of the vitreous to regress. A number of clinical findings are frequently associated with PHPV, including microphthalmos, glaucoma, shallowing of the anterior chamber, corneal opacity, congenital cataract, coloboma, and retinal degeneration (11-13). Even mild cases are associated with amblyopia. A very early therapeutic treatment is needed to prevent later secondary defects. This directly relates to the National Eye Institute program's goal to investigate the development of the visual system.