The chromosome 15q14 locus for bipolar disorder and schizophrenia: is C15orf53 a major candidate gene?

Bipolar disorder (BD) and schizophrenia are complexly inherited and highly heritable disorders with currently unknown etiologies. Recently, two independent genome-wide association studies for BD identified a small region on chromosome 15q14-15.1, pointing to a locus close to the gene C15orf53. Previously, this genomic region was also found to co-segregate with periodic catatonia (SCZD10, OMIM %605419), an unsystematic schizophrenia according to Leonhard's classification, in several multiplex families, thus pointing to overlapping etiologies of both conditions. A susceptibility locus on chromosome 15q14-15.1 was narrowed down to a 4.38 Mb region in these affected families followed by mutation and segregation analyses of C15orf53. Association analysis of individuals affected by BD and/or SCZD10 (n = 274) and controls (n = 230) and expression analyses in distinct post-mortem human limbic brain tissues were conducted. C15orf53 revealed no mutations in our SCZD10 family members, but segregation of two common haplotypes was found. No association of identified haplotypes was found in our case-control samples. Gene expression could be demonstrated for immune-system-derived cells but not for the post-mortem human limbic brain tissue. Our results indicate that C15orf53 is probably neither causative for the etiology of BD nor for SCZD10 in our samples.