基因治疗CRB基因突变导致RP/LCA疾病的策略研究

Retinal dystrophy is one of the major causes that lead to hereditary visual impairment and blindness. Mutations in the apical polarity gene Crumbs 1 (CRB1) leads to severe autosome recessive inherited retinal dystrophies. To date, over 150 mutations have been identified in the entire exome of CRB1, it is unknown the correlation between the type or location of these mutations and the clinical presentation. Crb play important roles during retinal development, the deficiency of Crb causes intricate phenotypes in vertebrate models such as mice and zebrafish. However the molecular mechanisms through which Crb functions are not very clear. Our preliminary data has suggested that Crb play essential roles through three different mechanisms during various developmental stages of vertebrate retinas. There is no effective treatment for the disease so far. Gene therapy via AAVs vector transferring proper cDNA is the most promising cure for retinal dystrophies and has primarily been applied for recessive null conditions. However gene therapy for the human CRB1 disease will be more complicated as the oversize of CRB1. More in-depth elucidation on Crb mechanism should be performed to develop a efficient gene therapy strategy for the disease. Here we designed a detailed proposal to study the mechanism of Crb during retinal development in zebrafish. Based on this, we further propose to investigate the treatment using AAVs transfering recombinant CRB1 in mice. The results shall benefit our understanding of the pathology and therapy of human retinal degeneration disease caused by CRB1.

视网膜疾病严重威胁人类健康。人类CRB基因突变引起视网膜退行性病变，其临床症状复杂。至今还没有成熟有效的方法可以医治此类疾病。腺相关病毒载体介导的基因治疗是目前唯一展现了良好前景的治疗方案。但腺相关病毒载体因其携带能力有限而并不适合于因CRB突变引起的视网膜疾病。本项目前期研究提示，Crb通过三种不同机制在视网膜发育的不同阶段（神经上皮细胞阶段、感光细胞前体阶段和感光细胞成熟阶段）发挥重要作用，且其缩短的重组形式可能可以拯救基因的功能。基于此，本项目拟结合分子细胞生物学、斑马鱼和小鼠模型，进一步研究和验证Crb在视网膜发育和相关疾病中的功能与机制；并在此基础上，寻找能拯救基因突变的重组Crb形式，探索有效治疗CRB突变引起的视网膜退行性疾病的基因治疗策略。研究结果具有重要的生物学意义和潜在临床转化价值，预期将对基因治疗人类CRB1突变引起的LCA和RP做出重要贡献。

人类CRB基因突变引起视网膜退行性病变，其致病机制和临床症状复杂。本项目结合分子细胞生物学、斑马鱼和小鼠模型，首先深入探讨Crb在视网膜相关疾病中的致病机制。研究结果显示，Crb/MPP5基顶端极性复合物通过与Rab11相互作用，定向招募钙黏蛋白等分子，并使之富集在包括感光细胞在内的上皮细胞顶端形成带状黏粘，从而维持视网膜的结构稳定。同时我们首次发现，zCrb2a/zCrb2b通过其胞外结构域形成异聚体，在其胞内复合物aPKC和MPP5的共同调节下，维持感光细胞的平面极性，促进斑马鱼视觉功能。当zCrb2b缺失时，斑马鱼体现出近视样表型。同时，本项目揭示了zCrb2a的1-870aa结构域可以基本拯救因Crb2a缺失而产生的OLM的崩解；含改造Crb1基因的AAV病毒可以部分拯救基因突变引起的视网膜疾病，但不能达到完全拯救的效果。