Psychiatric disorders and mutations at the Wolfram syndrome locus

Identifying genetic loci at which mutations predispose individuals to common psychiatric illnesses will have major impact on the diagnosis and treatment of mental illness. The available evidence indicates that mutations at the Wolfram syndrome locus contribute substantially to the prevalence of psychiatric illness in the general population. Patients with mutations at this locus on both parental chromosomes, called Wolfram syndrome homozygotes, have a distinctive and rare autosomal recessive syndrome characterized by juvenile onset diabetes mellitus and bilateral progressive optic atrophy. Diverse and serious psychiatric manifestations frequently have been observed in Wolfram syndrome patients; however, the population burden of mental illness attributable to mutations at this locus is almost entirely from individuals who carry a single mutation, called Wolfram syndrome heterozygotes, who have no distinguishing physical characteristics but constitute approximately 1% of the population. Molecular genotyping of blood relatives of Wolfram syndrome patients has shown that Wolfram syndrome heterozygotes are 26-fold more likely than noncarriers to have a psychiatric hospitalization. Severe depression was the predominant finding in the test group studied. The prediction that approximately 25% of all patients hospitalized for depression are Wolfram syndrome heterozygotes now can be tested by mutation screening of hospitalized patients from the general population. Many other behavioral and cognitive difficulties also have been observed in Wolfram syndrome families. For each specific psychiatric abnormality, a "test group" of blood relatives within Wolfram syndrome families with that abnormality can be formed. By comparing the number of Wolfram syndrome heterozygotes found in each test group by molecular genotyping with the number expected under the null hypothesis, the index-test method can determine which clinical phenotypes result from mutations at the Wolfram syndrome locus. This method can be utilized to identify other loci at which mutations predispose individuals to psychiatric illnesses.