RTN4R and schizophrenia: Although, collectively, the human genetic and animal model studies designed to identify schizophrenia susceptibility genes from the 22q11.2 region have implicated primarily three genes: proline dehydrogenase (PRODH), ZDHHC8 and catechol-O-methyltransferase (COMT) [21]–[25] and their interactions [26], [27], a study by Liu et al. [22] presented suggestive evidence that common variants located at the 3′ end of the RTN4R gene are associated with schizophrenia in patient samples from the U.S. and South Africa.