Spatial and temporal expression of folate-binding protein 1 (Fbp1) is closely associated with anterior neural tube closure in mice.

Periconceptional folate supplementation is widely believed to have significant preventive effects on the production of neural tube defects. Folate-binding protein 1 (FBP1) is one of the membrane proteins that mediate cellular uptake of folate. Although recent studies suggest that Fbp1 is essential for neural tube closure, the pattern of Fbp1 expression in embryonic tissues has not been examined in detail. To elucidate how Fbp1 contributes to neural tube closure, we examined the spatial and temporal expression patterns of Fbp1 in the developing neural folds and tube of mouse embryos by in situ hybridization. Fbp1 showed a distinct expression pattern in the neural folds, which preceded initiation of neural tube closure at the cervical region and the prosencephalic/mesencephalic boundary. Fbp1 expression was mainly localized to the most dorsal regions of the neural folds where fusion was to occur. With proceeding of neural fold fusion, Fbp1 expression extended to the adjacent unfused neural folds. In the rhombencephalon, robust expression of Fbp1 was observed in rhombomere2 (r2) and r6, suggesting its roles in development of neural crest cells. Fbp1 also showed intense expression in the yolk sac, indicating that FBP1 may mediate transferring maternal folate to embryos during neurulation. These findings indicate close association between Fbp1 and anterior neural tube closure.