1 (CA1) of the hippocampus from both experimental groups (supplemental methods) were analysed on genome-wide Illumina BeadChips. Expression data for the probes specific for the genes in the associated region, TMTC2, SLC6A15, LRRIQ1 and ALX1 were compared between the two groups. SLC6A15 mRNA levels were reduced 1.9-fold in the CA1 region in stress susceptible versus stress resilient mice. Expression levels of the other genes did not exceed background noise in the CA1 region, and are thus likely not expressed at higher levels in this brain region (tab. S3). This further supports SLC6A15 as the gene of interest within this locus. The reduction of SLC6A15 expression in CA1 could be validated by in situ hybridisation in 9 stress susceptible versus 9 stress resilient mice (fig. 6A and 6B). Moreover, a significant reduction in SLC6A15 expression could also be observed in the dentate gyrus of stress susceptible animals (fig. 6C and 6D). The demonstrated downregulation of SLC6A15 expression in stress-susceptible mice, most prominent in the CA1 region of the hippocampus, suggests SLC6A15 to play a role in long-term effects of chronic stress on neuronal circuits and is in accordance with the human MD risk genotype-dependent effects assayed by in vivo volumetry which
