DLG4 and schizophrenia: In Figure 1, two genes are found to establish the connection between RHO and ERBB4, each of them a gene with connections to schizophrenia and retinitis pigmentosa, respectively: DLG4 and GRK1. DLG4 encodes a member of the membrane-associated guanylate kinase family and has been recently argued to play a role in schizophrenia pathogenesis (Balan et al., 2013).