Topology of WFS1 Variants Linked With Islet Function and Higher Risk of Urological Symptoms in WFS1-Associated Disease.

Wolfram syndrome type 1 gene (WFS1), which encodes a transmembrane (TM) structural protein (wolframin), is essential for several biological processes. Mutations of WFS1, autosomal dominant or recessive inherited, are related to a broad clinical spectrum. Molecular genetic tests were performed, and clinical phenotypes of three WFS1-associated cases were evaluated. The expression of WFS1, viability, and endoplasmic reticulum (ER) stress of the MIN6 cell and structural analysis of the variant WFS1 protein were revealed. Furthermore, a total of 75 pathogenic WFS1 variants from ClinVar were included to analyze variant-phenotype association. Genetic testing revealed 3 mutations with unclear pathogenicity in WFS1 of the 3 patients with early-onset diabetes, including c.613G >A (p.G205S), c.2053C >T (p.R685C), and c.169G >A (p.A57T). Decreased expression, reduced β-cell viability and enhanced ER stress were found in all variants. Protein stability and structural analysis showed increased protein stability and molecule flexibility of variants p.R685C in the ER-lumenal domain and p.A57T in the ATP6VIA-interaction region, while destabilized protein and rigidificated structure by p.G205S variant in the EF-hand domain at the cytoplasm region. Remarkably, topology was found an independent risk factor with urological symptoms (USs) (p=0.007, odds ratio [OR] 4.768 [95% confidence interval (CI): 1.531-14.854]). Surprisingly, variants in the cytoplasm had the highest risk with US than ones in the ER-lumenal domain (p=0.008, OR 22.013 [95% CI: 2.270-213.428]). The functional analysis of the three variants of uncertain significance in WFS1 indicated a quantitative and qualitative damage to wolframin with proven pathogenicity. The topology of the WFS1 protein may play an important role in the pathogenesis of β-cell and urological defects in WFS1-associated disease.