Genetic Modifiers of Enhanced S-cone Syndrome –Role of the External Limiting Membrane

项目摘要/摘要 增强型S视锥综合征(ESCS)是一种遗传性视网膜变性，其特征是 S视锥细胞数目、视网膜发育不良和进行性光感受器变性导致早夜 失明和视力丧失。这种疾病是由决定命运的杆状基因突变引起的。 转录因子NR2E3在人类和RD7小鼠模型中的表达。疾病的表现在以下方面有很大的变化 人类和依赖于遗传背景的小鼠，证明了遗传修饰物的存在。 小鼠模型显示视网膜发育不良与该疾病的发生密切相关 外界膜(ELM)的断裂，Müler细胞之间的粘连/紧密连接的网络 顶突和光感受器内节。榆树的碎裂也观察到在其他 与发育不良相关的视网膜疾病，如因基因突变引起的Leber先天性黑色素沉着症(LCA) Crums1(CRB1)和RP27，以及糖尿病视网膜病变。 我们已经确定了一种遗传修饰物，可以防止RD7小鼠和小鼠榆树的碎片化 和NRL Ko小鼠(RP27)模型。这一发现有力地表明了榆树的致病作用 光感受器发育异常中的片段化，并提供了一种工具来建立 ELM断裂发生的机制，它们如何导致视网膜发育不良，以及这如何影响疾病 进步。 为了确定这些机制，我们将：1)确定榆树结合部的自然历史 用细胞连接标记分析WT和RD7模型的形成和光感受器分化 蛋白质。2)通过单细胞RNAseq分析确定ELM碎裂所涉及的细胞类型。3) 确定修饰蛋白如何改变连接蛋白在细胞膜上的募集。4)识别 我们已经产生的额外的遗传修饰菌株的分子基础，以进一步了解 NR2E3的致病途径。

PROJECT SUMMARY/ABSTRACT Enhanced S-cone syndrome (ESCS) is an inherited retinal degeneration characterized by an increased number of S-cones, retinal dysplasia, and progressive photoreceptor degeneration leading to early night blindness and loss of visual acuity. The disease is caused by mutations in the rod-fate determining transcription factor NR2E3 in humans and the rd7 mouse model. The disease presentation is highly variable in human and dependent on genetic background in the mouse, demonstrating the existence of genetic modifiers. The mouse model demonstrates that the retinal dysplasia is intimately associated with the occurrence of breaks in the external limiting membrane (ELM), a network of adherens/tight junctions between Müller cell apical processes and photoreceptor inner segments. Fragmentation of the ELM is also observed in other retinal diseases associated with dysplasia, such as Leber's Congenital Amaurosis (LCA) due to mutations in crumbs1 (CRB1) and RP27, and in diabetic retinopathy. We have identified a genetic modifier that prevents the fragmentation of the ELM in both the rd7 mouse and the Nrl ko mouse (RP27) models. This discovery strongly suggests a causative role for the ELM fragmentation in the development of photoreceptor dysplasia and provides a tool with which to establish the mechanisms by which ELM breaks occur, how they lead to retinal dysplasia, and how this affects disease progression. In order to identify these mechanisms we will: 1) Determine the natural history of ELM junction formation and photoreceptor differentiation in wt and the rd7 model using marker analysis of cell junction proteins. 2) Identify the cell types involved in the ELM fragmentation by single cell RNAseq analysis. 3) Determine how the modifier protein alters recruitment of junctional proteins to the cell membrane. 4) Identify the molecular basis of additional genetic modifier strains that we have generated to gain further insight into the NR2E3 disease pathways.