Mutation of NOP2/Sun RNA methyltransferase family member 2 (NSUN2), which methylates cytosine-5 of tRNAs is associated with microcephaly in humans and mice [81], while mutation of Threonylcarbamoyladenosine tRNA methylthiotransferase (CDKAL1), which catalyses the 2-methylthio-N6-threonylcarbamoyladenosine (ms2t6A) modification of A37 in tRNA-Lys-UUU is associated with increased risk of type 2 diabetes mellitus in humans and mice [82,83,84]. The gene discussed is CDKAL1; the disease is microcephaly.