In the human brain, downregulation of nuclear DNMT1 is linked to Parkinson’s disease (PD) and dementia with Lewy bodies (DLB) [88], whereas a mutation in the DNMT3a gene is linked to autism spectrum disorder (ASD) [89,90] and Tatton-Brown–Rahman syndrome (TBRS) [91]. Here, DNMT1 is linked to Tatton-Brown-Rahman overgrowth syndrome.