Differences in axial curvature correlate with species-specific rate of neural tube closure in embryos of chick, rabbit, mouse, rat and human.

Studies on the mouse strain curly tail, a mutant for neural tube defects, have indicated that axial curvature is an important factor in neural tube closure. Previously reported results from experimental interventions in both mouse and chick embryos indicated that curvature along the craniocaudal axis and closure of the posterior neuropore (PNP) are inversely related, a correlation that is also proposed for the rabbit embryo. It was hypothesized that this relationship is a sign of a more general mechanism. Therefore, in the present report the number of species in which axial curvature is described along the craniocaudal axis was extended to include the rat and human. Next, the closure rate of the neural tube as well as the curvature of the PNP region was determined morphometrically for embryos of the following species: chick, rabbit, mouse, rat and human. Although the relationship between neural tube closure and axial curvature appeared specific for each species in the comparative analysis, a general association of increased rate of closure with a decreased curvature emerged. It is concluded that axial curvature is an important factor in neurulation.