PRDM9 and neurodevelopmental disorder: In contrast to histone methyltransferases, histone demethylases erase the methyl groups from histone lysine residues, A number of neurodevelopmental disorders, including both OMIM-codified and uncodified syndromes, are associated with heterozygous or hemizygous variants of the null type in histone demethylase genes (Swahari 2019).