Distinct blood DNA methylation profiles in subtypes of orofacial cleft

Background There is evidence that different subtypes of orofacial cleft have distinct aetiologies, although the precise molecular mechanisms underlying these are unknown. Given the key role of epigenetic processes such as DNA methylation in embryonic development, it is likely that aberrant DNA methylation may also play a part in the development of orofacial clefts. Methods In this study, we explored whether blood samples from children with different cleft subtypes showed distinct DNA methylation profiles. In whole blood samples from 150 children from the Cleft Collective cohort study, we measured DNA methylation at over 450,000 sites on the genome. We then carried out epigenome-wide association studies (EWAS) to test the association between methylation at each site and cleft subtype (cleft lip only CLO n=50; cleft palate only CPO n=50; cleft lip and palate CLP n=50). Results We found four genomic regions differentially methylated in CLO compared to CLP, 17 in CPO compared to CLP and 294 in CPO compared to CLO. These regions included several mapping to genes that have previously been implicated in the development of orofacial clefts (for example, TBX1, COL11A2, HOXA2, PDGFRA ) and over 250 novel associations. Conclusion Our finding of distinct methylation profiles in different cleft subtypes might reflect differences in their aetiologies, with DNA methylation either playing a causal role in development of OFC subtypes or reflecting causal genetic or environmental factors.