Neural tube closure and neural tube defects: Studies in animal models reveal known knowns and known unknowns

The vertebrate central nervous system is a hollow structure that develops first as a flat sheet of cells and subsequently rolls into a tube during embryogenesis. Failure of this rolling process, called neural tube closure, results in a class of common human birth defects called neural tube defects. The cellular and molecular mechanisms governing neural tube closure have been studied extensively in animal models, but much remains to be elucidated. In this review, I will highlight recent progress in understanding neural tube closure mechanisms and how these studies can inform our search for the genes that underlie human neural tube defects. Supplementary material for this article can be found on the American Journal of Medical Genetics (Part C) website (http:// www.mrw.interscience.wiley.com/suppmat/1552-4868/suppmat/2005/135/v135.1.wallingford.html) (c) 2005 Wiley-Liss, Inc.