Why is folate effective in preventing neural tube closure defects?

Neural tube defects (NTDs) originate from a failure of the embryonic neural tube to close. The pathogenesis of NTDs is largely unknown. Fortunately, adequate maternal folate application is known to reduce the risk of human NTDs. However, why folate reduces NTDs is largely unknown. The main cause for NTDs is the disturbance of the cell growth in the neuroepithelium. Of course, rapid cell growth needs enough synthesis of nuclei acids. Interestingly, folate is used as a source for the synthesis of nucleic acids. Furthermore, glycine cleavage system (GCS) is essential for the synthesis of nucleic acids from folate, and very strongly expressed in neuroepithelial cells, suggesting that these highly proliferating cells need enough synthesis of nuclei acids and high amounts of folate. Taken together, I speculate the following hypothesis; (1) The closure of the neural tube requires rapid growth of neuroepithelial cells. (2) High rates of nuclei acids synthesis are needed for the rapid growth. (3) GCS, which is requisite in nucleic acid synthesis from folate, is expressed very strongly and functions robustly in neuroepithelial cells. (4) Pregnant women require 5-10-fold higher amounts of folate compared to non-pregnant women. (5) So, folate-deficient situations are easy to occur in neuroepithelial cells, resulting in NTDs. (6) Thus, folate is effective to prevent NTDs.