RAB2A and major depressive disorder: Histamine is synthesized from histidine by HDC in neurons restricted to the hypothalamic tuberomamillary nucleus and innervating most of the brain.[43] Previous rodent experiments implied the neuronal histaminergic system might be involved in depressive symptoms.[44] However, it did not show significant changes in MDD subjects according to Shan study.[44] RAB2A, a member of RAS oncogene family, was also upregulated in umbilical cord blood exposed to prenatal MDD according to our bioinformatics analysis.