Identification of pathogenic mutations for a Wolfram syndrome pedigree by whole exome sequencing and analysis of its clinical characteristics

Abstract

Objective·To identify the causative gene and mutations and describe the clinical traits in a Chinese diabetes pedigree suspected of Wolfram syndrome.Methods·A total of 12 subjects from one family were included. The proband was admitted to the Department of Endocrinology, The First Affiliated Hospital of Xinxiang Medical University, for the first time in May 2013. Then he visited the hospital for follow-up in July 2022 and in April 2023, respectively. The other members of this family included the proband′s sister, father, mother, paternal grandfather, paternal grandmother, uncle, aunt, as well as maternal grandfather, maternal grandmother, and two brothers of the proband′s mother. Clinical data of all subjects were collected. The whole exome sequencing was used to screen the pathogenic genes and mutation sites of six members of the family, and Sanger sequencing was used to verify the above results. Effects of the mutation of the pathogenic gene WFS1 in Wolfram syndrome on the function of the wolframin protein were evaluated by bioinformatics softwares, including CADD, DANN, MetaSVM, Polyphen-2, SIFT and M-CAP. The three-dimensional structures of wild-type and mutant wolframin proteins were constructed with Swiss-Model software, and visualized with PyMOL software. Cluster Omega software was used for evaluating species conservation of WFS1 gene mutation sites. JNetPRED software was used for online prediction of wolframin protein secondary structure.Results·The proband and his sister both carried R558H and S411Cfs*131 mutations, two compound heterozygous mutations of the Wolfram syndrome pathogenic gene WFS1. The proband′s father and parental grandfather both carried the R558H mutation, while the proband′s mother and maternal grandfather both carried the S411Cfs*131 mutation. The R558H mutation was a rare missense mutation, and the S411Cfs*131 mutation was a novel frameshift mutation. Bioinformatics analysis softwares predicted that the R558H mutation located in the α-helical structure of the wolframin protein. This mutation was a damage mutation and the amino acid sequence of the mutation region was highly conservative among 12 species with varying degrees of evolution, including humans.Conclusion·Two causative mutations of WFS1 gene are identified in a Chinese diabetes pedigree by whole exome sequencing. The study supplements the existing genotype and phenotype profiles of Wolfram syndrome, which can realize early diagnosis of diabetes pedigrees and help in performing timely follow-up of patients, so as to achieve early intervention and treatment of this disease.

Keywords

• whole exome sequencing
• wolfram syndrome
• diabetes pedigree
• causative mutation