LAUSR

Global DNA hypermethylation is induced in embryonic neuroepithelium by maternal diabetes, leading to neural tube defects (NTDs). However the underlying mechanism is not clear. Our previous study has demonstrated that the green tea polyphenal Epigallocatechin gallate (EGCG) inhibited DNA hypermethylation and ameliorated maternal diabetes-induced NTDs. To determine whether antioxidant enzymes can suppress DNA hypermethylation in diabetic embryos, SOD1 transgenic male mice are breed with diabetic wild type female mice. SOD1 overexpression reduces maternal diabetes-induced DNA hypermethylation leading to suppression of DNMT3a and DNMT3b, but not DNMT1. To further investigate whether maternal diabetes-increased DNA methyltransferase 3a (DNMT3a) is involved in the pathogenesis of diabetic embryopathy, the Dnmt3a gene was deleted using the Cre-Flox (f) approach by crossing DNMT3af/+ ;nestin-Cre male mice with DNMT3af/f female mice. Dnmt3a deletion specifically occurred in the developing neuroepithelium, and DNMT1 and DNMT3b expression were not affected. Conditional deletion of Dnmt3a significantly reduces the NTD rate from 27.2% in wild-type embryos to 4% in homozygous deletion embryos (DNMT3af/f ;nestin-Cre) under maternal diabetic conditions and ameliorates maternal diabetes-induced DNA hyper-methylation. Moreover, Dnmt3a deficiency in the neuroepithelium abrogated maternal diabetes-induced hyper-methylation in the promoters region of neural tube closure essential genes including Pax3, Tulp3 and GRHL3, leading to activation of these genes. Furthermore maternal diabetes-induced ER stress in neuroepithelium is blocked by conditional deletion of Dnmt3a, which suppresses neuroepithelium apoptosis. Taken together, our findings demonstrate that Dnmt3a conditional deletion in neuroepithelium restores maternal diabetes-suppressed neural tube closure essential genes expression and blocks maternal diabetes-activated ER stress.