Increased methylation levels of the MTHFR gene promoter in Down syndrome

Aims: MTHFR is a key enzyme in the one-carbon metabolic pathway, whose activity has been implicated in Down syndrome (DS) and in the development of congenital heart defects (CHDs). The main aim was to assess promoter methylation levels of the MTHFR gene in DS individuals, including those with congenital heart defects (DS-CHD+), and those without (DS-CHD-), as well as control subjects. We also investigated if common MTHFR polymorphisms, namely 677C > T and 1298A > C correlate with MTHFR promoter methylation levels. Patients and Methods: The study included 118 participants: 59 individuals with DS, 25 of which with CHD, and 59 age and gender matched controls. Genomic DNA was extracted from peripheral blood. Methylation-sensitive high-resolution melting and PCR–RFLP were used to assess methylation and genotyping. Results: DS individuals showed significantly higher MTHFR methylation levels than controls (p < 0.0001). No difference in MTHFR methylation levels between DS-CHD+ and DS-CHD- individuals was observed (p = 0.38). MTHFR 677TT carriers showed higher mean MTHFR methylation levels than 677CC carriers (p < 0.05). Conclusion: We observed a significant increase in MTHFR promoter methylation levels in DS individuals compared to controls. Folate metabolism could influence MTHFR methylation levels as shown indirectly by the association of the MTHFR 677C > T polymorphism.