Socioeconomic position during pregnancy and DNA methylation signatures at three stages across the early life: Epigenome-wide association studies in the ALSPAC birth cohort

BACKGROUND: Socioeconomic experiences are recognized determinants of health, and recent work has shown that social disadvantages in early life may induce sustained biological changes at molecular level that are detectable later in life. However, the dynamics and persistence of biological embedding of socioeconomic position (SEP) remains vastly unexplored.  
METHODS: Using the data from the ALSPAC birth cohort, we performed epigenome-wide association studies of DNA methylation changes at three life stages (birth, n=914; childhood at mean age 7.5, n =973; and adolescence at mean age 15.5, n=974), measured using the Illumina HumanMethylation450 Beadchip, in relation to pregnancy SEP indicators (maternal and paternal education and occupation).  
RESULTS: Across the four early life SEP metrics investigated, only maternal education was associated with methylation levels at birth, and four CpGs mapped to SULF1, GLB1L2 and RPUSD1 genes were identified (FDR-corrected p-value < 0.05). No epigenetic signature was found associated with maternal education in children samples, while methylation levels at 20 CpG loci were found significantly associated with maternal education in adolescence. Although no overlap was found between the differentially methylated CpG sites at different ages, we identified two CpG sites at birth and during adolescence that are 219 bp apart in the SULF1 gene that encodes an heparan sulfatase involved in modulation of signalling pathways. Using data from an independent birth cohort, the ENVIRONAGE-cohort, we were not able to replicate these findings.   
CONCLUSIONS: Taken together, our results suggest that parental SEP, and particularly maternal education may influence the offspring’s methylome at birth and adolescence.