Fig. 4. Defects in the neural tube and dermomyotome of chimeric embryos are not rescued by wild-type cells. High chimeric embryos exhibit spina bifida and/or exencephaly. The remarkable contribution of mutant cells to the dermomyotome, documented by the X-gal staining, results in disorganized somites. In addition, the muscle precursor cells are not able to migrate into the limb (A,B) when compared with the embryo in C (chimera generated with Pax3^+/- cells), where blue cells can be observed in the limb (white arrow). Black (A) and white (B) arrowheads show the disorganized dermomyotome. Black arrows in C indicate the regular and organized dermomyotome marked by Pax3^+/- cells. Scale bars: 1 mm in A,C; 0.5 mm in B.