Fig. 5. Aberrant hindlimb morphology and proliferation in Isl1Cre/+;Bmpr1a mutants. (A,B,F,G) Whole-mount views of hindlimbs of wild-type and mutant embryos. Mutant limbs had ectopic outgrowths on ventral surface at right angles to endogenous limb (arrows, F,G).

(C,H) Alcian Blue staining for cartilage. Cartilage structures were severely abnormal in mutant hindlimbs, with a reduced number of digit elements compared with wild type (arrows C,H). (D,I) Apoptosis analysis. No increases in apoptosis were evident in mutant relative to wild-type hindlimb. (E,J) Cell proliferation analysis. Staining for phosphorylated histone H3 (PHH3) revealed reduced rates of proliferation in mutant hindlimbs relative to controls. Arrows in B indicate the hind limbs.