Neural tube defects (NTDs), affecting 1-2 per 1000 pregnancies, are severe congenital
malformations that arise from the failure of neurulation during early embryonic development. The
methylation hypothesis suggests that folate prevents NTDs by stimulating cellular methylation
reactions. Folate is central to the one-carbon metabolism that produces pyrimidines and purines for
DNA synthesis and for the generation of the methyldonor S-adenosyl-methionine. This review focuses
on the relation between the folate-mediated one-carbon metabolism, DNA methylation and NTDs.
Studies will be discussed that investigated global or locus-specific DNA methylation differences in
patients with NTDs. Folate deficiency may increase NTD risk by decreasing DNA methylation, but to date, human studies
vary widely in study design in terms of analyzing different clinical subtypes of NTDs, using different methylation
quantification assays and using DNA isolated from diverse types of tissues. Some studies have focused mainly on global
DNA methylation differences while others have quantified specific methylation differences for imprinted genes,
transposable elements and DNA repair enzymes. Findings of global DNA hypomethylation and LINE-1 hypomethylation
suggest that epigenetic alterations may disrupt neural tube closure. However, current research does not support a linear
relation between red blood cell folate concentration and DNA methylation. Further studies are required to better
understand the interaction between folate, DNA methylation changes and NTDs.
Keywords: DNA methylation, DNA hypomethylation, epigenetics, folate, LINE-1 hypomethylation, neural tube defects, nutriepigenomics,
nutrition, one-carbon metabolism.
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