NTDs were not observed among Cre-negative Grhl3+/- or Grhl3f/- embryos (both genotypes are effectively heterozygous), whereas spina bifida occurred in 60% (6/10 embryos) and tail flexion defects in 70% (7/10) of Sox17Cre/+; Grhl3f/- embryos. The gene discussed is GRHL3; the disease is spina bifida.