DNMT1 and autosomal dominant cerebellar ataxia, deafness and narcolepsy: The first was ADCADN, caused by pathogenic variants in DNMT1, a methyltransferase known as the central player in the maintenance of CpG methylation.2,40 Interestingly, DNMT1 has been suggested to regulate H3K4 methylation, providing a direct mechanistic link with KDM2B.