Association of the XBP1-116C/G polymorphism with schizophrenia in the Japanese population.

Schizophrenia and bipolar disorder share some clinical features and linkage studies have shown that several loci are common. Recently, the authors found that the -116C-->G substitution in the promotor region of XBP1, a pivotal gene in endoplasmic reticulum (ER) stress response, causes the impairment of ER stress response, and that the -116C/C genotype is a protective factor; in other words the presence of the G allele increases the risk for bipolar disorder. The gene is located on 22q12.1, which is also linked with schizophrenia. The polymorphisms were investigated in 234 schizophrenic patients as compared with controls. Significant difference of genotype distribution was observed, which suggested that the -116C/C genotype is a protective factor for both of the major mental disorders.