Cellular DNA methylation program during neurulation and its alteration by alcohol exposure.

BACKGROUND Epigenetic changes are believed to be among the earliest key regulators for cell fate and embryonic development. To support this premise, it is important to understand whether or not systemic epigenetic changes coordinate with the progression of development. We have demonstrated that DNA methylation is programmed when neural stem cells differentiate (Zhou et al.,2011). Here, we analyzed the DNA methylation events that occur during early neural tube development. METHODS AND RESULTS Using immunocytochemistry, we demonstrated that the DNA methylation marks - 5-methylcytosine (5-MeC), DNA methylation binding domain 1 (MBD1), and DNA methytransferases 1 (DNMT1) were highly coordinated in temporal and spatial patterns that paralleled the progress of embryonic development. The above ontogenic program of DNA methylation was, however, subjected to environmental modification. Alcohol exposure during fetal development, which is known to cause fetal alcohol spectrum disorder, altered the density and distribution of the DNA methylation marks. The alcohol exposure (88 mM) over 6 or 44 hours at gestation day 8 (GD-8) to GD-10 altered timely DNA methylation and retarded embryonic growth. We further demonstrated that the direct inhibiting of DNA methylation with 5-aza-cytidine (5-AZA) resulted in similar growth retardation. CONCLUSIONS We identified a temporal and spatial cellular DNA methylation program after initial erasure, which parallels embryonic maturation. Alcohol delayed the cellular DNA methylation program and also retarded embryonic growth. Since direct inhibiting of DNA methylation resulted in similar retardation, alcohol thus can affect embryonic development through a epigenetic pathway.