DNMT1 and narcolepsy: In particular, 4/8 studies independently confirmed functional mutations in the DNMT1 gene to be strongly associated with autosomal dominant cerebellar ataxia, deafness and narcolepsy (ADCA-DN) with 3/8 of these studies consistently showing mutations within exon 21 of DNMT1 to be found in ADCA-DN patients or children of ADCA-DN patients.