SLC30A1 and major depressive disorder: found a reduction in the ZnT3 protein level as well as a significant increase in the level of ZnT1, ZnT4, ZnT5 protein in the prefrontal cortex of subjects diagnosed with major depressive disorder (MDD) and in non-diagnosed suicide victims, relative to control subjects suggesting that zinc transporters are important in the pathophysiology of MDD and suicide [12].