P2RY12 and major depressive disorder: It is tempting to speculate that the increased expression of TMEM119 and P2Y12 in microglia clusters from MDD cases may reflect enhanced neuron-microglia communication via transforming growth factor (TGF)β1, which shows significant gene-environment interactions predicting adult depression in the context of early life trauma53, as well as purines, in an attempt to protect neuronal function54,55.