Neural tube closure does not depend exclusively on the MHP or DLHPs, since closure can occur in the absence of either, as in Mode 3 and Mode 1 spinal neurulation, respectively. However, cell shape changes of some type, affecting morphogenesis of the spinal neural tube, are clearly required for closure to occur in all species studied, including the mouse . Table 5 demonstrates the lack of specific expression of genes at the DLHPs. However, overlapping gene expression throughout the neuroepithelium and tips of neural folds may facilitate the bending mechanism seen in the DLHPs.