Sex-specific effects of prenatal stress in 5-Htt deficient mice: towards molecular mechanisms of gene x environment interactions

prenatal stress response, genetic modification Background: Prenatal stress (PS) exposure has been shown to increase the risk for emotional disorders in later life. Furthermore, the serotonin transporter (5-HTT) genotype is suggested to exert a modulating effect on the association between early life stress and the risk for depression. In the present study, we use a 5-HTT x PS paradigm to investigate whether the effects of PS are dependent upon the 5-HTT genotype. Methods: The effects of PS on cognition, anxiety- and depression-related behaviour were examined using a maternal restraint stress paradigm of PS in C57BL6 wild-type (WT) and heterozygous (+/-) 5-HTT knockout mice. Additionally, in the female offspring, a genome-wide hippocampal gene expression screening was performed. Results: 5-HTT +/- offspring showed enhanced memory performance and signs of reduced anxiety as compared to WT offspring. Conversely, exposure of 5-HTT +/- mice to PS was associated with altered stress-responsivity and increased depressive-like behaviour, particularly in female offspring. Further, 5-HTT genotype, PS and their interaction differentially affected the expression of numerous genes and related pathways within the female hippocampus. Specifically, MAPK and neurotrophin signalling were regulated by both the 5-HTT +/- genotype and PS exposure, whereas cytokine and Wnt signalling were affected in a 5-HTT genotype x PS manner, indicating a gene x environment interaction at the molecular level. Conclusions: The long-term behavioural effects of PS in C57BL6 mice are partly dependent on the 5-HTT genotype. Further, hippocampal gene expression profiles suggest that distinct molecular mechanisms mediate the behavioural effects of the 5-HTT genotype, PS exposure, and their interaction. total samples analysed are 12