Determining Molecular and Cellular Mechanisms of Glaucoma

描述（由申请人提供）：我的目标是确定闭角型青光眼（ACG）的分子和细胞机制，ACG是青光眼的一个严重亚群。在ACG中，由于各种解剖和生理因素的共同作用，虹膜向前推进，造成眼引流结构的物理阻塞。这导致房水排出效率低下，从而引起高眼压（IOP）和青光眼。ACG的机制在很大程度上是未知的。我最近描述了一只突变小鼠的特征，它再现了人类原发性ACG的特征，包括轻微缩小的眼球大小，相对较大的晶状体和狭窄的角度。致病突变发生在编码新型丝氨酸蛋白酶Prss56的基因中。重要的是，同一基因的突变有助于后段缩小（后小眼症）的人类ACG。我将利用这个小鼠模型来解决ACG的潜在机制。我有三个目标：目标1：预计小鼠和人类PRS556中的已知突变不会破坏该蛋白酶的催化活性。因此，目前尚不清楚突变体prss56介导的ACG是由其无法水解内源性底物还是通过获得新的或增强的活性来控制的。为了解决这个问题，我将产生具有Prss56条件等位基因的小鼠，该等位基因可以使用cre/loxP系统选择性地失活，从而产生催化失活的蛋白酶。我将检测Prss56并确定其对ACG相关表型的影响，包括其对眼轴长度、角度配置和IOP的影响。目标2:2a。我将测试视网膜在调解突变体PRSS56的影响中的作用。视网膜是介导突变prss56诱导的ACG的一个强有力的候选者。来自视网膜的信号在决定眼轴长度方面起着重要的作用。因此，视网膜PRSS56异常可导致眼尺寸减小（ACG的重要组成部分）。眼大小的改变与巩膜成分的改变有关，巩膜成分的改变可通过阻碍跨巩膜液体流动而进一步加剧ACG。我将有条件地只消融视网膜细胞中的Prss56，并评估其对ACG相关表型的影响。2 b。我对Prss56突变小鼠的研究表明，出生后眼部发育减小不足以导致闭角和高IOP。成人眼组织的改变也必须参与疾病的进展。为了确定ACG中阶段特异性变化的作用，我将使用诱导Cre选择性地从不同年龄的眼睛中切除Prss56，并评估ACG相关表型。目的3：鉴定PRSS56蛋白酶底物对于理解促进ACG的分子途径至关重要。我将采用两种最先进的方法来识别PRSS56底物。首先，使用开放阅读框(ORF)-噬菌体显示阵列来识别被PRSS56切割的靶标。其次，采用一种名为末端胺同位素标记底物（TAILS）的蛋白质组范围策略来鉴定PRSS56底物。我将使用分子方法验证这些相互作用的体内特异性。

DESCRIPTION (provided by applicant): My goal is to identify the molecular and cellular mechanisms of Angle-Closure Glaucoma (ACG), a severe subset of glaucoma. In ACG, due to a combination of various anatomical and physiological factors, the iris is pushed forward causing physical blockage of the ocular drainage structure. This results in inefficient aqueous humor exits, thereby causing high intraocular pressure (IOP) and glaucoma. The mechanisms underlying ACG are largely unidentified. I have recently characterized a mutant mouse that recapitulates features of human Primary ACG including modestly decreased ocular size, a relatively larger lens and a narrow angle. The causal mutation is in a gene coding for a novel serine protease Prss56. Importantly, mutations in the same gene contribute to ACG in humans with reduced posterior segment (posterior microphthalmia). I will exploit this mouse model to resolve the mechanisms underlying ACG. I have three aims: Aim 1: The known mutations in mouse and human PRS556 are not predicted to disrupt the catalytic activity of this protease. Hence, it is unclear if the mutant PRSS56-mediated ACG is controlled by its inability to proteolytically cleave endogenous substrate or by gaining a new or enhanced activity. To address this, I will generate mice with a Prss56 conditional allele that can be selectively inactivated using the cre/loxP system to give rise to a catalytically inactive protease. I will ablte Prss56 and determine their impact on ACG relevant phenotypes, including its effect on ocular axial length, angle configuration and IOP. Aim 2: 2a. I will test the contribution of the retina i mediating the effect of the mutant PRSS56. The retina is a strong candidate in mediating mutant Prss56-induced ACG. Signals from the retina are known to play an important role in determining ocular axial length. Therefore, abnormal retinal PRSS56 can induce reduced ocular size (an important component of ACG). Alteration in ocular size has been linked to changes in scleral composition, which can further exacerbate ACG by impeding transcleral fluid flow. I will conditionally ablate Prss56 only in the retinal cells and assess their effect on ACG relevant phenotypes. 2b. My studies using Prss56 mutant mice suggest that postnatal developmental decrease in ocular size alone is insufficient to cause angle closure and high IOP. Alterations in adult ocular tissues must also participate in disease progression. To determine a role of stage-specific changes in ACG, I will use an inducible Cre to ablate Prss56 selectively from eyes at different ages and assess ACG related phenotypes. Aim 3: Identification of PRSS56 protease substrates is critical in understanding the molecular pathways contributing to ACG. I will employ two state-of-the-art approaches to identify PRSS56 substrates. First, use an open-reading frame (ORF)- phage display array to identify targets that are cleaved by PRSS56. Second, employ a proteome-wide strategy named terminal amine isotopic labeling of substrates (TAILS) to identify PRSS56 substrates. I will validate the in vivo specificity of these interactions using molecular approaches.