FKBP5 polymorphism is associated with major depression but not with bipolar disorder

Altered activity of hypothalamus–pituitary–adrenal glands (HPA) axis in response to stress underlies the pathogenesis of mood disorders such as depression and bipolar disorder. Chaperone proteins regulate sensitivity of glucocorticoid receptor (GR) to steroids. We hypothesized that genetic variants within the FKBP5 – gene encoding co-chaperone protein essential in GR signaling – may influence the susceptibility to major depressive disorder and bipolar disorder. In the study participated 528 bipolar patients, 218 patients with major depressive disorder and 742 subjects from control group. Genotypes for eight FKBP5 polymorphisms (rs1360780, rs755658, rs9470080, rs4713916, rs7748266, rs9296158, rs9394309, rs3800373) were established by TagMan SNP Genotyping Assays (Applied Biosystems). Linkage disequilibrium analysis for FKBP5 gene was done in Haploview. Gene–gene interactions between FKBP5 and NR3C1 polymorphisms (reported previously) were analyzed using the multidimensionality-reduction method (MDR). We have observed an association between five FKBP5 polymorphisms (rs1360780, rs9470080, rs4713916, rs9296158 and rs9394309) and major depressive disorder (p=0.011; p=0.007, p=0.038; p=0.030; p=0.018, respectively), but not bipolar disorder. In linkage disequilibrium analysis we found that seven FKBP5 polymorphisms build haplotype block (rs3800373, rs755658, rs9296158, rs7748266, rs1360780, rs9394309, rs9470080, respectively). We observed that two haplotype combinations (ACATTGT and CCACTAT) were significantly more frequent in the MDD patients than in controls (p=0.014 and p=0.043). We have not observed such an association for BD patients. We have found that interaction between rs9470080 of FKBP5 and rs6198 of NR3C1 influences MDD risk. The main limitations of this study include low power and limited sample size of MDD patients. Single markers and haplotypes of FKBP5 gene and the interaction with glucocorticoid receptor gene (NR3C1) may influence MDD predisposition.