METHODS: Whole exome sequencing (WES) was performed on a 9-year-old girl with SRNS associated with FSGS (SRNS-FSGS). We analyzed the expression of CRB2, slit diaphragm (SD)-associated proteins, and sphingosine 1-phosphate receptor 1 (S1PR1) in the proband and CRB2 knock-down podocytes.
RESULTS: In this study, we identified two novel compound heterozygous mutations in the Crumbs homolog 2 (CRB2) gene (c.2905delinsGCCACCTCGCGCTGGCTG, p.T969Afs*179 and c.3268C > G, p.R1090G) in a family with early-onset SRNS-FSGS. Our findings demonstrate that these CRB2 abnormalities were the underlying cause of SRNS-FSGS. CRB2 defects led to the dysfunction of podocyte SD-related proteins, including podocin, nephrin, and zonula occludens-1 (ZO-1), by reducing the phosphorylation level of S1PR1. Interestingly, the podocytic cytoskeleton remained unaffected, as demonstrated by normal expression and localization of synaptopodin. Our study also revealed a secondary decrease in CRB2 expression in idiopathic FSGS patients, indicating that CRB2 mutations may cause FSGS through a previously unknown mechanism involving SD-related proteins.
CONCLUSIONS: Overall, our findings shed new light on the pathogenesis of SRNS-FSGS and revealed that the novel pathogenic mutations in CRB2 contribute to the development of FSGS through a previously unknown mechanism involving SD-related proteins. A higher resolution version of the Graphical abstract is available as Supplementary information.
方法:对一名9岁女孩进行全外显子组测序(WES),该女孩患有与FSGS相关的SRNS(SRNS-FSGS)。我们分析了CRB2,狭缝隔膜(SD)相关蛋白的表达,先证者和CRB2敲低足细胞中的鞘氨醇1-磷酸受体1(S1PR1)。
结果:在这项研究中,我们在面包屑同源物2(CRB2)基因(c.2905delinsGCCACCTCGCGCTGGCTG,p.T969Afs*179andc.326C>G,p.R1090G)在一个患有早发性SRNS-FSGS的家庭中。我们的研究结果表明,这些CRB2异常是SRNS-FSGS的根本原因。CRB2缺陷导致足细胞SD相关蛋白的功能障碍,包括泊多辛,nephrin,和小带闭塞-1(ZO-1),通过降低S1PR1的磷酸化水平。有趣的是,足细胞骨架未受影响,如突触素的正常表达和定位所证明的。我们的研究还揭示了特发性FSGS患者CRB2表达的继发性降低,表明CRB2突变可能通过涉及SD相关蛋白的先前未知的机制引起FSGS。
结论:总体而言,我们的研究结果为SRNS-FSGS的发病机制提供了新的思路,并揭示CRB2中的新致病突变通过涉及SD相关蛋白的先前未知机制促进FSGS的发展.更高分辨率版本的图形摘要可作为补充信息。