COL4A3 mutations cause focal segmental glomerulosclerosis
JOURNAL OF MOLECULAR CELL BIOLOGY
Authors: Xie, Jingyuan; Wu, Xiaoxi; Ren, Hong; Wang, Weiming; Wang, Zhaohui; Pan, Xiaoxia; Hao, Xu; Tong, Jun; Ma, Jun; Ye, Zhibin; Meng, Guoyu; Zhu, Yufei; Kiryluk, Krzysztof; Kong, Xiangyin; Hu, Landian; Chen, Nan
Abstract
Focal segmental glomerulosclerosis (FSGS) is a histologically identifiable glomerular injury often leading to proteinuria and renal failure. To identify its causal genes, whole-exome sequencing and Sanger sequencing were performed on a large Chinese cohort that comprised 40 FSGS families, 50 sporadic FSGS patients, 9 independent autosomal recessive Alport's syndrome (ARAS) patients, and 190 ethnically matched healthy controls. Patients with extrarenal manifestations, indicating systemic diseases or other known hereditary renal diseases, were excluded. Heterozygous COL4A3 mutations were identified in five (12.5%) FSGS families and one (2%) sporadic FSGS patient. All identified mutations disrupted highly conserved protein sequences and none of them was found in either public databases or the 190 healthy controls. Of the FSGS patients with heterozygous COL4A3 mutations, segmental thinning of the glomerular base membrane (GBM) was only detected in the patient with electronic microscopy examination results available. Five ARAS patients (55.6%) had homozygous or compound-heterozygous mutations in COL4A3 or COL4A4. Serious changes in the GBM, hearing loss, and ocular abnormalities were found in 100%, 80%, and 40% of the ARAS patients, respectively. Overall, a new sub-group of FSGS patients resulting from heterozygous COL4A3 mutations was identified. The mutations are relatively frequent in families diagnosed with inherited forms of FSGS. Thus, we suggest screening for COL4A3 mutations in familial FSGS patients.
Whole-Exome Sequencing for Identification of Potential Causal Variants for Diffuse Cutaneous Systemic Sclerosis
ARTHRITIS & RHEUMATOLOGY
Authors: Mak, Angel C. Y.; Tang, Paul L. F.; Cleveland, Clare; Smith, Melanie H.; Connolly, M. Kari; Katsumoto, Tamiko R.; Wolters, Paul J.; Kwok, Pui-Yan; Criswell, Lindsey A.
Abstract
Objective. Scleroderma is a genetically complex autoimmune disease with substantial phenotypic heterogeneity. Previous genome-wide association studies have identified common genetic variants associated with disease risk, but these studies are not designed to capture rare or potential causal variants. Our goal was to identify rare as well as common genetic variants in patients with diffuse cutaneous systemic sclerosis (dcSSc) through whole-exome sequencing (WES) in order to identify potential causal variants. Methods. We generated WES data for 32 dcSSc patients with or without interstitial lung disease (ILD) and for 17 healthy in-house controls. Variants were annotated and filtered by quality, minor allele frequency, and deleterious effects on gene function. We applied a gene burden test to identify novel dcSSc and dcSSc-associated ILD candidate genes that were enriched with deleterious variants in cases compared to in-house controls as well as controls from the 1000 Genomes Project (n=130). Results. We identified 70 genes that were enriched with deleterious variants in dcSSc patients. Two of them (BANK1 and TERT) were in pathways previously implicated in SSc or ILD pathogenesis or known susceptibility loci. Newly identified genes (COL4A3, COL4A4, COL5A2, COL13A1, and COL22A1) were significantly enriched in the extracellular matrix-related pathway, which is relevant to the fibrotic features of dcSSc, and in the DNA repair pathway (XRCC4). Conclusion. This study demonstrates the value of WES for the identification of novel gene variants and pathways that may contribute to scleroderma risk and/or severity. The candidate genes we discovered are potential targets for in-depth functional studies.