Other altered histone modifications associated to schizophrenia include: (1) PRDM9 hypermethylation, a gene that encodes a histone methyltransferase that specifically trimethylates H3K4, playing a central role in the transcriptional activation of genes during early meiotic prophase [54], (2) significant disruption of the ubiquitinylation, SUMOylation, NEDD8ylation, and Ufmylation systems in the schizophrenic superior temporal gyrus and, finally, a decrease in the expression of PIAS3, an E3 ligase which catalyzes the covalent attachment of a SUMO protein to specific target substrates. Here, PRDM9 is linked to schizophrenia.