Mutations in several methyltransferase enzymes have neuronal phenotypes such as Weaver syndrome for EZH2 (Gibson et al., 2012), Kabuki syndrome for MLL2 (Ng et al., 2010) and Kleefstra syndrome for the EHMT1/GLP1 gene (Kleefstra et al., 2006) underscoring their importance in neuronal development (Table 1). The gene discussed is EHMT1; the disease is Kleefstra syndrome.