A novel heterozygous variant of the COL4A4 gene in a Chinese family with hematuria and proteinuria leads to focal segmental glomerulosclerosis and chronic kidney disease

Abstract

Background: Focal segmental glomerulosclerosis (FSGS), as the frequent primary glomerular diseases in adults, accounts for symptomless proteinuria or nephrotic syndrome with or without renal insufficiency. As the crucial lesion of chronic kidney disease (CKD), accumulating evidence from recent studies show that mutations in Collagen-related genes may be responsible for FSGS. The aim of this study was to identify the genetic lesion of a Chinese family with FSGS and CKD.

Methods: In this study, we recruited a Han-Chinese family with unexplained high serum creatinine, hematuria, and proteinuria. Further renal biopsy and renal pathology indicated the diagnosis of FSGS in the proband. Whole-exome sequencing and Sanger sequencing were employed to explore the pathogenic mutation of this family.

Results: A novel heterozygous mutation (NM_000092 c.2030G>A, p.G677D) of the collagen type IV alpha-4 gene (COL4A4) was detected. Co-segregation analysis revealed that the novel mutation was carried by all the five affected individuals and absent in other healthy members as well as in our 200 local control cohorts. Bioinformatics predication indicated that this novel mutation was pathogenic and may disrupt the structure and function of type IV collagen. Simultaneously, this variant is located in an evolutionarily conserved site of COL4A4 protein.

Conclusion: Here, we identified a novel mutation of COL4A4 in a family with FSGS and CKD. Our study expanded the variants spectrum of the COL4A4 gene and contributed to the genetic counseling and prenatal genetic diagnosis of the family. In addition, we also recommended the new classification of collagen IV nephropathies, which may be a benefit to the diagnosis, target drug treatment, and management of patients with COL4A3/COL4A4 mutations.

Keywords: COL4A4 mutation; focal segmental glomerulosclerosis; hematuria; proteinuria.

FIGURE 1

The clinical data of the family with FSGS. (a) Pedigree of the family with FSGS. Black circles/squares are affected, white are unaffected. Arrow indicates the proband. N means normal; M shows the COL4A4 c.2030G>A variant. Three large circles in red represent the three individuals underwent whole‐exome sequencing. (b) Overlapping filter strategy. Asterisks denote remaining variants for further analysis that are present in two affected members (I‐2 and III‐4) but not in the normal control (II‐2). (c) Schematic representation of the filter strategies employed in this study. (d) HE staining (e) Masson staining (f) PAS staining and (g) PASM staining for renal biopsy of the proband (III‐4)

FIGURE 2

The Sanger sequencing and conservation analysis of the novel variant. (a) Sanger DNA sequencing chromatogram demonstrates the heterozygosity for a COL4A4 missense mutation (COL4A4 c.2030G>A, p.G677D) in affected members. (b) Alignment of multiple COL4A4 protein sequences across species. The affected G677 amino acid is located in a highly conserved region in different mammals (from Ensembl). The letter in red shows the G677 site