DNMT1 and schizophrenia: A full-length HERV-W LTR in the gamma-aminobutyric acid type B receptor 1(GABBR1) regulatory region may induce hypermethylation, downregulating GABBR1 expression (Hegyi, 2013), which is consistent with DNA methyltransferase 1 (DNMT1) overexpression in GABAergic interneurons and reelin promoter hypermethylation in schizophrenia (Grayson et al., 2005; Veldic et al., 2003).