RAD21突变诱导神经嵴异常迁移引起角膜巩膜化的机制研究

角膜巩膜化是先天角膜透明性异常疾病，角巩膜缘界限不清，致病机理尚未明确。课题组前期证实: (1)外周角膜巩膜化家系携带RAD21突变，在爪蟾发育时期表达该突变基因可明显影响颅面部神经嵴细胞迁移进入角膜基质，同时造成角膜基质纤维呈现巩膜特征。(2)RAD21突变导致颅面部神经嵴迁移相关基因PCDHGC3(原钙黏蛋白γ基因簇C3)表达显著升高，PCDHGC3介导细胞的自我规避，在正常巩膜表达量较高，在角膜中低表达。因此我们提出假设：在角膜发育过程中，RAD21突变可能通过影响PCDHGC3的空间表达，导致迁移进入角膜基质的神经嵴细胞数量减少，而巩膜基质细胞代偿性进入角膜基质，造成角膜巩膜化。基于此，本课题拟采用爪蟾模型、神经嵴干细胞和巩膜基质细胞移植的小鼠模型，研究RAD21突变通过调控PCDHGC3影响神经嵴迁移引起角膜巩膜化的机制，并初步探讨通过调控神经嵴迁移干预治疗的可行性。

Sclerocornea is a congenital disorder characterized with opacification of the cornea and indistinct of the scleral-corneal border, which pathogenesis is still not clear. In our previous study: (1) We identified a RAD21 variant from a peripheral sclerocornea pedigree. Overexpression of this RAD21 variant in Xenopus laevis embryos led to the decrease in the number of neural crest cells entering corneal stroma and the disorganization of corneal stroma fibrils, turning to resemble the scleral stoma. (2) The mutation resulted in a significant increase in the expression of a craniofacial neural crest migration related gene PCDHGC3 (protocadherin gamma subfamily C3), which could mediate “self-avoidance” between cells. Under a normal situation, the expression of PCDHGC3 is more abundant in the sclera than in the cornea. Therefore, we hypothesize that the alteration of PCDHGC3 spatial expression during development induced by RAD21 mutation caused the decline of neural crest cells in the corneal stroma while scleral fibroblasts influxes into the corneal stroma instead, which lead to sclerocornea. We will use the sclerocornea X. laevis model, induced pluripotent stem cells-derived neural crest cells, and a mouse model with scleral fibroblasts implanted to the cornea, to study the sclerocornea pathogenesis induced by the neural crest improper migration mediated by RAD21 and PCDHGC3, and to explore the intervention possibility for corneal stroma development abnormalities.