RELN and major depressive disorder: We have discussed these data as an indication that nitric oxide-mitochondria-mediated excitotoxic events in reelin expressing neurons in the subgranular zone may instigate a decrease in reelin secretion by these neurons, resulting in deficits in dendritic maturation within newborn granule cells and dampened hippocampal plasticity that may be a key event in the pathophysiology of depression (see Caruncho et al., 2016; Allen et al., 2018).