RPS6KA1 and major depressive disorder: Interestingly, it has been shown that lower ERK activity and reduced gray matter volume in depressed patients are related to depression associated risk allele Ser704Cyst [91] and that haplotypes and gene-gene interaction in the Ras/Raf/MAPK/RSK signaling pathway are involved in antidepressant remission in depressed population [92].