Pitx2: Molecular Mechanisms in Eye Development and Disease

描述：调控眼前段结构正常发育的遗传网络还知之甚少。小鼠是确定眼睛正常发育的基本机制和分析遗传性眼病的理想模型。同源框基因PITX2的突变导致了阿森菲尔德-里格综合征(ARS)，这是一种常染色体显性疾病，会导致先天性眼前节缺陷和青光眼。我克隆了小鼠的Pitx2，并在小鼠身上使用基因打靶技术产生了一系列Pitx2等位基因，这些等位基因可以全局或有条件地消除基因功能，并能够改变基因剂量。根据已发表的数据和我们自己的初步结果，我们假设在眼睛发育过程中，Pitx2在眼周间充质中起核心作用，促进眼部间充质来源的眼细胞类型的分化，以及眼表面和神经外胚层正常发育所需的外在因子的间质表达。在之前的资助周期中，我们证明了早期的Pitx2在眼神经脊和中胚层中的表达，确定了在眼睛发育的多个步骤中神经脊中的Pitx2功能是必需的，并确定了PITX2在神经脊中调节Wnt信号的作用，这可能是Pitx2突变的表型。这个建议的总体目标是使用我们的一系列小鼠Pitx2等位基因来确定Pitx2在眼睛发育过程中中胚层中的作用(S)，并建立Pitx2和Wnt信号通路组件之间的机制和功能关系。在目标1中，我们将使用条件靶向策略来检验Pitx2在眼中胚层中具有不同功能的假设。在目标2中，我们将测试一个特定的Wnt信号通路基因作为PITX2的直接靶点，并确定其在眼睛发育中的形态和分子作用，以确定该基因是否与Pitx2表型的组成有关。我们还将筛查患有特定眼前段缺陷和青光眼的人类患者，以寻找该基因的突变。在目标3中，我们将直接测试小鼠体内Pitx2和Wnt途径基因之间的遗传相互作用，作为修改Pitx2突变表型的机制，因为表型可变性是ARS的关键特征。这一多方面的方法将提供有关Pitx2在眼睛发育中的功能的具体机制细节，以及在这一过程中更一般的眼周间充质的基本机制的新知识。这些基本信息对于了解包括青光眼在内的眼病是必不可少的。

DESCRIPTION: Genetic networks regulating normal development of anterior segment structures are poorly understood. Mice are ideal models for determining the basic mechanisms contributing to normal eye development and for analyzing genetic eye disease. Mutations in the homeobox gene PITX2 result in Axenfeld-Rieger Syndrome (ARS), an autosomal dominant disease causing congenital anterior segment defects and glaucoma. I cloned Pitx2 from mouse and used gene targeting in mice to generate a series of Pitx2 alleles that allow for global or conditional ablation of gene function, and the ability to vary gene dose. Based on published data and our own preliminary results, we hypothesize a central role for Pitx2 in periocular mesenchyme during eye development for differentiation of ocular cell types derived from mesenchyme and for mesenchyme expression of extrinsic factors required for normal development of surface and neural ectoderm in the eye. In the previous grant cycle, we demonstrated early Pitx2 expression in ocular neural crest and mesoderm, established that Pitx2 function in neural crest is required for multiple steps in eye development, and identified a role for PITX2 in regulating Wnt signaling in neural crest that could account for Pitx2 mutant phenotypes. The overall goals of this proposal are to use our series of murine Pitx2 alleles to determine the role(s) of Pitx2 in mesoderm during eye development and to establish the mechanistic and functional relationships between Pitx2 and components of the Wnt signaling pathway. In Aim 1, we will test the hypothesis that Pitx2 has distinct functions in ocular mesoderm using a conditional targeting strategy. In Aim 2, we will test a specific Wnt signaling pathway gene as a direct PITX2 target and identify its morphological and molecular roles in eye development to see if this gene accounts for components of the Pitx2 phenotype. We will also screen human patients with specific anterior segment defects and glaucoma for mutations in this gene. In Aim 3, we will directly test for genetic interactions between Pitx2 and the Wnt pathway gene in mice as a mechanism for modification of the Pitx2 mutant phenotype since phenotypic variability is a key feature of ARS. This multifaceted approach will provide specific mechanistic details about the functions of Pitx2 in eye development and new knowledge into more general fundamental mechanisms of periocular mesenchyme in this process. This basic information is essential for understanding eye disease, including glaucoma.