DNMT3B and neural tube defect: Hcy ↓; NTD incidence ↓; apoptosis (apoptotic cells ↓; p53 ↓; Bax ↓); Pax3 methylation ↓; one-carbon metabolism (MTHFR ↑; MTR ↓; MAT ↓; Dnmt3b ↓; SAHH ↓; CBS ↑)