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

The human calcium-activated potassium chan- nel gene (hKCNN3, hSKCa3) contains two tandemly ar- ranged, multiallelic CAG repeats located in exon 1 which result in short to moderate polyglutamine stretches of un- known functional significance. Case-control and family- based association studies suggested an association of hKCNN3 repeats with susceptibility for schizophrenia. Twelve multiplex pedigrees with periodic catatonia, a schi- zophrenia subtype with major gene effect and patterns of anticipation, were genotyped using the multiallelic hKCNN3 repeat polymorphism. Using a dominant model of inheritance with sex- and age-dependent penetrance classes, cumulative results showed exclusion of linkage of hKCNN3 to periodic catatonia under the assumption of ge- netic homogeneity with lod score of -48.01 at zero recom- bination fraction. Our results provide evidence that hKCNN3 is not the causative gene in the familial schizo- phrenia subtype of periodic catatonia. By fluorescent in situ hybridization we confirmed the assignment of hKCNN3 to chromosome 1q21 near the heterochromatin region. Linkage mapping showed segregation with marker D1S498 (θ = 0.05) and placed hKCNN3in the genetic link- age map in a cluster of genes near the centromeric region of chromosome 1.