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Clin Exp Nephrol. 2016 Oct;20(5):699-702. Epub 2015 Nov 18.

X-linked Alport syndrome associated with a synonymous p.Gly292Gly mutation alters the splicing donor site of the type IV collagen alpha chain 5 gene.

Author information

1
Department of Pediatrics, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, 6500017, Japan.
2
Department of Pediatrics, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, 6500017, Japan. nozu@med.kobe-u.ac.jp.
3
Department of Nephrology, Saiseikai Kawaguchi General Hospital, Saitama, Japan.
4
Department of Pediatrics, Wakayama Medical University, Wakayama, Japan.
5
Faculty of Medicine, University of Southampton, Southampton, UK.

Abstract

BACKGROUND:

X-linked Alport syndrome (XLAS) is a progressive hereditary nephropathy caused by mutations in the type IV collagen alpha chain 5 gene (COL4A5). Although many COL4A5 mutations have previously been identified, pathogenic synonymous mutations have not yet been described.

METHODS:

A family with XLAS underwent mutational analyses of COL4A5 by PCR and direct sequencing, as well as transcript analysis of potential splice site mutations. In silico analysis was also conducted to predict the disruption of splicing factor binding sites. Immunohistochemistry (IHC) of kidney biopsies was used to detect α2 and α5 chain expression.

RESULTS:

We identified a hemizygous point mutation, c.876A>T, in exon 15 of COL4A5 in the proband and his brother, which is predicted to result in a synonymous amino acid change, p.(Gly292Gly). Transcript analysis showed that this mutation potentially altered splicing because it disrupted the splicing factor binding site. The kidney biopsy of the proband showed lamellation of the glomerular basement membrane (GBM), while IHC revealed negative α5(IV) staining in the GBM and Bowman's capsule, which is typical of XLAS.

CONCLUSIONS:

This is the first report of a synonymous COL4A5 substitution being responsible for XLAS. Our findings suggest that transcript analysis should be conducted for the future correct assessment of silent mutations.

KEYWORDS:

COL4A5; Silent mutation; Splicing; Synonymous mutation

PMID:
26581810
DOI:
10.1007/s10157-015-1197-9
[Indexed for MEDLINE]

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