No evidence for an association of the CTLA4 gene with bipolar I disorder

The purpose of the present paper was to investigate the relationship between the first exon at position +49 (A/G) polymorphism of the cytotoxic T lymphocyte antigen 4 (CTLA4) gene and bipolar disorder. Among the Korean patients diagnosed with bipolar disorder according to Diagnostic and Statistical Manual of Mental Disorders (4th edn; DSM‐IV), 90 patients without serious medical illness, neurologic illness, hormonal disorder, or concomitant mental illness were selected. The normal control group consisted of 149 age‐ and sex‐matched subjects without current or past history of autoimmune diseases or mental disorder. DNA was extracted from peripheral blood using proteinase K; and the exon 1 region of the CTLA4 gene was amplified by polymerase chain reaction. Gene typing was performed using single strand conformation polymorphism. There were no significant differences in genotype frequencies of CTLA4*G/G, CTLA4*G/A, and CTLA4*A/A between the patients with bipolar disorder and the control group (48.9% vs 46.3%, 44.4% vs 39.6%, and 6.7% vs 14.1%, respectively). There were no significant differences in allelic frequencies of CTLA4*G and CTLA4*A between the patients with bipolar disorder and the control group (71.1% vs 66.1%; 28.9% vs 33.9%, respectively). In the present study an association was not found of exon 1 (+49) polymorphism of CTLA4 gene with bipolar disorder in the Korean population.