No evidence to support the association of the potassium channel gene hSKCa3 cag repeat with schizophrenia or bipolar affective disorder in irish population

The phenomenon of anticipation has recently been implicated in the aetiology of neuropsychiatrie disorders including schizophrenia and bipolar disorder. For some disorders, anticipation has been shown to be caused by trinucleotide repeat (CAG and CTG) expansions. Several recent studies have demonstrated significant excess of expanded repeats with both schizophrenia and bipolar affective disorder. More recently, Chandy et al. [1998] have isolated a novel calcium-activated potassium channel gene (hSKCa3) which contains two CAG repeats. They found that the overall allele frequency distribution of the second repeat polymorphism is significantly different in schizophrenic patients than in controls (P = 0.02) with CAG repeats longer than the model value (19 repeats), over represented in patients (P = 0.0035). A similar but non-significant trend was also seen in bipolar patients. We examined these findings in 170 Irish familial schizophrenics, 91 bipolar disorder patients, and 217 ethnically matched controls. We found no significant differences between either of the patient samples and their respective controls. We conclude that the hSKCa3 second repeat polymorphism is not predisposing to schizophrenia or bipolar disorders at least in the Irish population.