Examples include a mouse model for Down’s syndrome (Ts65DN) [48], heregulin (a ligand for tyrosine receptor kinase) mutant mice [49], an epilepsy model deficient in a repair protein L-isoaspartate (d-aspartate)-O-methyltransferase (Pcmt1−/−) [50] and Huntington triplet deletion mice Hdh (∆Q/∆Q) mice [51]. The gene discussed is PCMT1; the disease is Down syndrome.