IGF2 and neural tube defect: In the present study, we investigated the status of the IGF2-relevant DMR methylation levels and chromatin status in the promoters in human NTD samples and confirmed the corresponding transcriptional activity of IGF2. To further understand the complex epigenetic mechanisms of this imprinting gene regulation, we also employed the same strategy to test the above epigenetic regulatory characteristics in a mouse model with a rapid retinoic acid (RA)-induced NTD.