Periconceptional Folic Acid-Containing Supplements and LINE-1 DNA Methylation in the Marbles Prospective Study of Autism Spectrum Disorder

Background:   Epigenetic factors have been shown to contribute to the etiology of autism spectrum disorders (ASD). Dietary methyl-donors such as folate are essential for all biological methylation reactions, and maternal levels could influence DNA methylation profiles in children especially around conception when methylation patterns are erased and reestablished. We hypothesize that DNA methylation, influenced by maternal peri-conceptional methyl-donor intake, affects the child’s risk for ASD.

Objectives: In a prospective study of high-risk ASD-affected families, we examined relationships between early prenatal vitamin use and DNA methylation of common LINE-1 repeats as a global epigenetic indicator. In addition, we investigated maternal and child DNA methylation in relation to the child’s development of ASD.

Methods: Mothers in the MARBLES (Markers of Autism Risk in Babies: Learning Early Signs) study who have at least one child with ASD, and who became pregnant with another child were included. Global DNA methylation levels were measured by bisulfite conversion and LINE-1 pyrosequencing in DNA extracted from maternal whole blood samples collected during each trimester and at delivery, and the child’s cord and peripheral blood . Maternal interviews collected information on prenatal vitamin use and time initiated. The Autism Diagnostic Observation Schedule (ADOS) was conducted on children at the MIND Institute clinic at 24 and 36 months and final clinical diagnoses were made at 36 months.

Results: Taking a prenatal vitamin before or during the first month of pregnancy was not significantly associated with LINE-1 DNA methylation in the mother’s blood. Prenatal vitamin use during this time was associated a trend towards lower LINE-1 DNA methylation in the child’s peripheral blood. Meeting ASD criteria on the ADOS at 24 months was associated with significantly higher DNA methylation in cord blood, and significantly lower DNA methylation in the child’s peripheral blood. In the subset of children with a final diagnosis (at 36 months), ASD case status of the child was associated with similar findings, with few differences in the maternal blood, and trends toward higher LINE-1 DNA methylation in cord blood and lower LINE-1 DNA methylation in the child’s peripheral blood.

Conclusions: These preliminary findings suggest that taking prenatal vitamins before and during the first month of pregnancy could impact the child’s LINE-1 DNA methylation levels, which are associated with autism symptomology and potentially ASD diagnosis. Further research is needed to confirm these results as more children reach a final diagnosis. Additional studies will also explore influences of total periconceptional folate intake, folate metabolism genes, and serum folate on child DNA methylation patterns.