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. This evidence concerns the gene COMT and schizophrenia.