Interestingly, as is the case with the craniorachischisis phenotype in homozygosity (Kibar et al., 2001; Murdoch et al., 2001), the failure of NT dorsal fusion is fully penetrant in Vangl2+/Lp embryos, and we believe that only in the most severe cases, where the affected area is too large, an open spina bifida would develop. This evidence concerns the gene VANGL2 and craniorachischisis.