背景:局灶节段肾小球硬化(FSGS)是主要影响足细胞的类固醇抗性肾病综合征(SRNS)的主要原因。虽然引起小儿SRNS的基因突变增强了我们对FSGS的理解,这种疾病的病因仍然很复杂,知之甚少。
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。
BACKGROUND: Focal segmental glomerulosclerosis (FSGS) is a leading cause of steroid-resistant nephrotic syndrome (SRNS) that predominantly affects the podocytes. While mutations in genes causing pediatric SRNS have enhanced our understanding of FSGS, the disease\'s etiology remains complex and poorly understood.
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.