NRG1 and schizophrenia: Of these pathways, schizophrenia appears to have to strongest link to the Nrg/ErbB pathway, and SNPs in several of the genes encoding Nrg (NRG1, NRG2, NRG3, and NRG6) and all of the genes encoding ErbB receptors (EGFR, ERBB2, ERBB3, and ERBB4) have been linked to schizophrenia (Mei and Nave, 2014).