hKCNN3 which maps to chromosome 1q21 is not the causative gene in periodiccatatonia, a familial subtype of schizophrenia

The human calcium-activated potassium channel gene (hKCNN3, hSKCa3) contain s two tandemly arranged, multiallelic CAG repeats located in exon 1 which r esult in short to moderate polyglutamine stretches of unknown functional si gnificance. Case-control and family-based association studies suggested an association of hKCNN3 repeats with susceptibility for schizophrenia. Twelve multiplex pedigrees with periodic catatonia, a schizophrenia subtype with major gene effect and patterns of anticipation, were genotyped using the mu ltiallelic hKCNN3 repeat polymorphism. Using a dominant model of inheritanc e with sex- and age-dependent penetrance classes, cumulative results showed exclusion of linkage of hKCNN3 to periodic catatonia under the assumption of genetic homogeneity with lod score of -48.01 at zero recombination fract ion. Our results provide evidence that hKCNN3 is not the causative gene in the familial schizophrenia subtype of periodic catatonia. By fluorescent in situ hybridization we confirmed the assignment of hKCNN3 to chromosome 1q2 1 near the heterochromatin region. Linkage mapping showed segregation with marker D1S498 (theta = 0.05) and placed hKCNN3 in the genetic linkage map i n a cluster of genes near the centromeric region of chromosome 1.