A second piece of evidence supporting the association of hydroymethylation and AD is the finding that a SNP within the gene encoding Ten-Eleven Translocation-1 (TET1, which catalyses the conversion of 5-methylcytosine to 5-hydroxymethylcytosine) is associated with late onset AD (Morgan et al., 2008). This evidence concerns the gene TET1 and Alzheimer disease.