Novel mutations in COL4A3, COL4A4, and COL4A5 in Chinese patients with Alport Syndrome

PLoS One. 2017 May 18;12(5):e0177685. doi: 10.1371/journal.pone.0177685. eCollection 2017.

Abstract

Alport syndrome (AS) is a clinically and genetically heterogeneous, progressive nephropathy caused by mutations in COL4A3, COL4A4, and COL4A5, which encode type IV collagen. The large sizes of these genes and the absence of mutation hot spots have complicated mutational analysis by routine polymerase chain reaction (PCR)-based approaches. Here, in order to design a rapid and effective method for the genetic diagnosis of AS, we developed a strategy by utilizing targeted capture associated with next-generation sequencing (NGS) to analyze COL4A3, COL4A4, and COL4A5 simultaneously in 20 AS patients. All the coding exons and flanking sequences of COL4A3, COL4A4, and COL4A5 from the probands were captured followed by HiSeq 2500 sequencing. Candidate mutations were validated by classic Sanger sequencing and quantitative (q)PCR. Sixteen patients (16/20, 75%) showed X-linked inheritance, and four patients (4/20, 20%) showed autosomal recessive inheritance. None of the individuals had autosomal-dominant AS. Fifteen novel mutations, 6 known mutations, and 2 novel fragment deletions were detected by targeted capture and NGS. Of these novel mutations, 12, 3, and 2 mutations were detected in COL4A5, COL4A4, and COL4A3, respectively. A comparison of the clinical manifestations caused by different types of mutations in COL4A5 suggested that nonsense mutations and glycine substitution by an acidic amino acid are more severe than the other missense mutations. Pathogenic mutations were detected in 20 patients. These novel mutations can expand the genotypic spectrum of AS. Our results demonstrated that targeted capture and NGS technology are effective in the genetic diagnosis of AS.

MeSH terms

  • Adolescent
  • Adult
  • Asian Continental Ancestry Group / genetics*
  • Autoantigens / genetics*
  • Child
  • Child, Preschool
  • China
  • Collagen Type IV / deficiency
  • Collagen Type IV / genetics*
  • Female
  • High-Throughput Nucleotide Sequencing
  • Humans
  • Male
  • Mutation*
  • Nephritis, Hereditary / genetics*
  • Sequence Deletion
  • Young Adult

Substances

  • Autoantigens
  • COL4A4 protein, human
  • COL4A5 protein, human
  • Collagen Type IV
  • type IV collagen alpha3 chain

Grant support

This work is supported by the grants from Science and Technology Program of Jiangsu Province (BL2014072), Science and Technology Development Project of Nanjing (No. 201402008), (No. 201503010), and National Key Clinical Program of China (No. 2014ZDZK003). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.