NRGN and major depressive disorder: Furthermore, we investigated a second hypothesis, that changes in synaptic proteins reflect disorder-specific pathological processes, and for this two further synaptic proteins were analysed, namely NRXN3, a presynaptic cell adhesion molecule involved in synapse formation and synaptic signalling and identified as downregulated in MDD as mentioned before,6 and neurogranin (NGRN), a postsynaptic protein regulated by synaptic activity and involved in plasticity.