DNA methyltransferase haplotype is associated with Alzheimer's disease

Epigenetic mechanisms have been implicated in syndromes associated with neuropsychiatric disorders, but little is known about the role of epigenetics in Alzheimer's disease (AD). DNA methylation, one of the main epigenetic mechanisms, is a complex process carried out by specific enzymes, such as DNMT1 and DNMT3B. This study aimed to investigate the association between DNMT1 and DNMT3B polymorphisms and AD. Two hundred and ten elderly subjects (108 healthy controls and 102 with AD-NINCDS/ARDA, DSM-IV-TR criteria) were assessed. DNA was obtained from whole blood, and genotypes were detected by an allelic discrimination assay using TaqMan® MGB probes on a real-time PCR system. The polymorphisms studied were rs2162560, rs759920 (DNMT1) and rs998382, rs2424913, rs2424932 (DNMT3B). For both genes, the polymorphisms were in strong linkage disequilibrium. Carriers of the DNMT3B TGG haplotype were associated with AD (OR = 3.03, 95% CI 1.63 to 5.63, P < 0.001). No significant difference between AD and the control group were observed for DNMT1 polymorphisms. This study is one of the first describing a significant association between DNMT3B polymorphisms and AD. This enzyme, which is responsible for methylation in a general way, may be involved in AD.