Fig. 1. Targeted inactivation of Msx2 but not of Msx1 suppresses the embryonic lethality of the homozygous Splotch genotype. Mice with targeted mutations in Msx1 or Msx2 were intercrossed with Splotch mutant mice as indicated in A. (B) A gross view of a newborn Msx2^–/–; Pax3^Sp/Sp pup. These mice typically had exencephaly (C), spina bifida (D) and craniofacial abnormalities including a foreshortened snout.