Neural Tube Defects (NTDs) are among the most frequent and severe malformations associated with maternal diabetes. DNA hypermethylation inhibits gene expression. Our recent studies have revealed a group of neural tube closure-related genes are downregulated by maternal diabetes. Planar cell polarity (PCP) is conserved in metazoans and is essential for development, deficiencies of PCP genes result in NTDs. Shroom3 encodes a PDZ-domain-containing protein that regulates cell shape in epithelium. Shroom3 interacts with PCP genes, loss of function of Shroom3 leads to NTDs. We hypothesize that DNA hypermethylation induced by maternal diabetes is responsible for the downregulation of Shroom3, which disrupts the PCP pathway leading to NTD formation. We found global DNA methylation levels were increased about 3 times and all 3 DNA methyltransferase levels were increased in the embryos from diabetic dams compared to the nondiabetic control group. Conditional double knockout of Dnmt3a/Dnmt3b gene in the developing neuroepithelium ameliorated maternal diabetes-induced NTDs, while overexpression Dnmt3b in the neuroepithelium induced NTDs in a dose dependent manner. Expression levels of PCP genes and Shroom3 were reduced by maternal diabetes and Dnmt3b transgenic overexpression. Similarly, PCP protein subcellular expression patterns were also disrupted. DNA methyl-sequencing revealed maternal diabetes-induced hypermethylation in the Shromm3 gene promoter. De-methylation rescued Shroom3 promoter activity suppressed by high glucose. Our study reveals that diabetes-induced DNA hypermethylation inhibits Shroom3 gene expression and Shroom3 deficiency mediates the teratogenic effect of maternal diabetes by disrupting PCP and resulting in NTDs. Since de-methylation can rescue Shroom3 activity, our findings suggest that targeting DNA hypermethylation could be therapeutically effective in treating maternal diabetes-induced NTDs.
C. Xu: None. P. Yang: None.
National Institutes of Health (R01DK083243, R01DK101972, R01HL131737, R01HL134368, R01DK103024)