METTL5 and intellectual disability, autosomal recessive: NSUN2 is known to cause forms of autosomal recessive intellectual disability (AR ID) [92–95] as are methyltransferases from other modification systems, e.g. FTSJ1, a human tRNA 2′-O-methyltransferase [96], and METTL5, an N6 adenine DNA and rRNA writer [30, 97].