Additionally, genome-wide association studies have shown that genes involved in glutamatergic neurotransmission and synaptic plasticity, e.g., mGluR3 (GRM3), glutamate ionotropic receptor NMDA type subunit 2A (GRIN2A), serine racemase (SRR), glutamate ionotropic receptor AMPA type subunit 1 (GRIA1) or neurogranin (NRGN), are associated with schizophrenia (Stefansson et al., 2009; Schizophrenia Working Group of the Psychiatric Genomics Consortium, 2014). Here, NRGN is linked to schizophrenia.