The BDNF Val66Met polymorphism regulates glucocorticoid-induced corticohippocampal remodeling and behavioral despair

The BDNF Val66Met polymorphism has been associated with sensitivity to stress and affective disorders. We therefore sought to model the inter-causality of these relationships under controlled laboratory conditions. We subjected humanized BDNF Val66Met (hBDNF(Val66Met)) transgenic mice to a history of stress, modeled by chronic late-adolescent corticosterone (CORT) exposure, before evaluating affective-related behavior using the forced-swim test (FST) in adulthood. While hBDNF(Met/Met) mice had a depression-like phenotype in the FST irrespective of CORT, hBDNF(Val/Val) wildtype mice had a resilient phenotype but developed an equally robust depressive-like phenotype following CORT. A range of stress-sensitive molecules were studied across the corticohippocampal axis, and where genotype differences occurred following CORT they tended to inversely coincide with the behavior of the hBDNF(Val/Val) group. Notably, tyrosine hydroxylase was markedly down-regulated in the mPFC of hBDNF(Val/Val) mice as a result of CORT treatment, which mimicked expression levels of hBDNF(Met/Met) mice and the FST behavior of both groups. The expression of calretinin, PSD-95, and truncated TrkB were also concomitantly reduced in the mPFC of hBDNF(Val/Val) mice by CORT. This work establishes BDNF(Val66Met) genotype as a regulator of behavioral despair, and identifies new biological targets of BDNF genetic variation relevant to stress-inducible disorders such as depression.