Autosomal dominant diabetes arising from a Wolfram syndrome 1 mutation

Abstract

We used an unbiased genome-wide approach to identify exonic variants segregating with diabetes in a multigenerational Finnish family. At least eight members of this family presented with diabetes with age of diagnosis ranging from 18 to 51 years and a pattern suggesting autosomal dominant inheritance. We sequenced the exomes of four affected members of this family and performed follow-up genotyping of additional affected and unaffected family members. We uncovered a novel nonsynonymous variant (p.Trp314Arg) in the Wolfram syndrome 1 (WFS1) gene that segregates completely with the diabetic phenotype. Multipoint parametric linkage analysis with 13 members of this family identified a single linkage signal with maximum logarithm of odds score 3.01 at 4p16.2-p16.1, corresponding to a region harboring the WFS1 locus. Functional studies demonstrate a role for this variant in endoplasmic reticulum stress, which is consistent with the β-cell failure phenotype seen in mutation carriers. This represents the first compelling report of a mutation in WFS1 associated with dominantly inherited nonsyndromic adult-onset diabetes.

FIG. 1.

Pedigree of four-generation (I–IV) family with autosomal dominant diabetes and WFS1 p.Trp314Arg carrier status. Gray squares and circles, patients with diabetes; white squares and circles, normal glucose tolerant. AoD, age of diagnosis of diabetes; M, p.Trp314Arg variant; N, reference allele; ?, unknown; *exome sequenced.

FIG. 2.

Parametric multipoint LOD scores based on pruned set of Illumina Omni2.5 SNP chip genotypes for 13 family members (Fig. 1: II-2, II-3, II-4, III-1, III-2, III-3, III-5, III-6, III-7, IV-1, IV-2, IV-4, and IV-5). A maximum LOD score of 3.01 was identified on chromosome 4p16.2-p16.1. LOD, logarithm of odds.

FIG. 3.

Variants in WFS1 identified in individuals with WS, MODY, or SNHI. Variants as listed in the EURO-WABB open variation database (https://lovd.euro-wabb.org/home.php?select_db=WFS1). A: Nonsense or frameshift variants. B: Missense variants. Gray boxes are exons; tick marks extending up from exons represent variants identified in a homozygous or compound heterozygous state, and tick marks extending below exons represent variants identified as a single heterozygous variant, although some of the cases of WS may be those in which the second allele has not yet been identified. Tick marks: blue, variants in WS individuals; red, variants in SNHI individuals; green, variant p.Arg703Cys identified in MODY individual; purple with asterisks, p.Trp314Arg identified in current study showing autosomal dominant inheritance of diabetes.

FIG. 4.

Luciferase reporter assays in HEK293T cells transfected with the ERSE reporter together with control (pcDNA), wild-type WFS1 (WT), mutant c.937C>T WFS1 (p.His313Tyr), or mutant c.940T>C WFS1 (p.Trp314Arg) expression plasmid. Cells were untreated (UT) or treated with TG (10 nmol/L) for 6 h. Relative intensity of luciferase (Promega Dual-Luciferase Reporter Assay System) was then measured (n = 3; values are mean ± SD). Transfections were normalized with the pRL-TK vector (Promega) as an internal control. Welch t test on log-transformed data was used for determining the significance between two treatments. ***P < 0.05.

FIG. 5.

Expression of WFS1 in fibroblasts from c.940T>C (p.Trp314Arg) carriers and noncarriers. A: Expression of WFS1 mRNA in skin fibroblasts. B: Western blot analysis of WFS1 protein abundance with tubulin as loading control. *Relative densitometry measurements (WFS1/tubulin) made with ImageJ64 (http://imagej.nih.gov/ij).

FIG. 6.

Cellular localization of WFS1. Skin fibroblasts obtained were double immunostained for WFS1 and PDI, and representative single-channel fluorescence images are shown individually and merged. III-1 (A), III-2: p.Trp314Arg (B), IV-1 (C), and IV-2: p.Trp314Arg (D). PDI, protein disulfide isomerase.