NRG1 and psychotic disorder: A missense mutation in Nrg1 resulting in a single amino acid substitution in a transmembrane valine (to leucine; rs74942016—results in Val→Leu at Position 321 in Type III Nrg1 β1a) was found to be associated with SCZ (and more strongly with psychosis) in a Costa Rican population (Walss-Bass et al., 2006).