Presence of a major WFS1 mutation in Spanish Wolfram syndrome pedigrees

Molecular characterization of WFS1 in patients with Wolfram syndrome

Wolfram (diabetes insipidus, diabetes mellitus, optic atrophy, and deafness) syndrome is a rare autosomal-recessive neurodegenerative disorder that is characterized by juvenile-onset diabetes mellitus, optic atrophy, diabetes insipidus, and sensorineural hearing impairment. A gene responsible for Wolfram syndrome (WFS1) has been identified on the short arm of chromosome 4 and subsequently mutations in WFS1 have been described. We have screened 12 patients with Wolfram syndrome from nine Dutch families for mutations in the WFS1-coding region by single-strand conformation polymorphism analysis and direct sequencing. Furthermore, we analyzed the mitochondrial genome for gross abnormalities and the A3243G point mutation in the leucyl-tRNA gene, because Wolfram syndrome shows phenotypic similarities with mitochondrial disease. Seven mutations in WFS1 were identified in six of nine families: two missense mutations, one frameshift mutation, one splice donor site mutation, and three deletions. In addition, a splice variant near the 5'UTR of WFS1 was identified, present in patient as well as control RNA samples in various percentages, alternating the translation initiation consensus sequence. Whether this WFS1 splice variant displays impaired translation efficiency remains to be determined. No MtDNA lesions were identified in any of the Wolfram patients. Our results demonstrate the usefulness of molecular analysis of WFS1 in the refinement of clinical diagnostic criteria for Wolfram syndrome that helps to dissect the clinically overlapping syndromes sharing diabetes mellitus and optic atrophy.

The WFS1 (Wolfram syndrome 1) is not a major susceptibility gene for the development of psychiatric disorders

BACKGROUND

Wolfram syndrome is a neurodegenerative disorder that is inherited in an autosomal recessive mode and characterized by the presence of diabetes mellitus and optic atrophy. Patients and heterozygote carriers are at an increased risk of suffering psychiatric disorders. Mutations in the Wolfram gene (WFS1 ) (4p16.1) are responsible for the development of the disease, and mRNA and protein expression of WFS1 have recently been found in areas of the rat brain that can be related to the psychiatric symptoms.

OBJECTIVE

To test the hypothesis that WFS1 mutations in heterozygote carriers or other variants of WFS1 can predispose to mental illness.

METHODS

Stage 1: Exons 2, 4 and 8 of that harbour mutations in Spanish Wolfram syndrome families were examined by Single Strand Conformation Polymorphism and sequencing analysis in 43 patients with affective disorder to identify variants and mutations. Stage 2: two variants identified in stage 1 were analysed in 152 psychiatric patients (118 schizophrenia and 34 affective disorder) and 177 control subjects.

RESULTS

Six variants (I333V Ile-->Val, F341, N500, R708, K774, K811) and a WFS1 mutation (R818C, Arg-->Cys) were found in the 43 patients analysed in stage 1 of the study. In stage 2, the R818C mutation was not found in the group of psychiatric patients but it was present in one control subject. The association study conducted with the I333V variant did not find significant differences in allele or genotype frequencies between patients and control subjects.

CONCLUSIONS

Our results suggest that WFS1 is not a major susceptibility gene for the development of psychiatric disorders in our population.