Fig. 3. Tcre;Fgfr1 limb bud morphology and cell survival. (A-L) Forelimb buds at the indicated stages with the AER labeled by Fgf8 whole-mount in situ hybridization. Each normal versus mutant pair is shown at the same magnification. (A-D) Dorsal view with the remaining axes indicated in A. Corresponding solid and broken lines in each pair are of the same length to assist comparisons of limb bud dimensions. (E-H) Transverse sections of limb buds. The mutant is thicker along the DV axis at E10.0 and E10.5. (I-L) Distal view with the remaining axes indicated in I. Arrowheads indicate that the mutant AER is wider than normal along the DV axis at E10.0 and E10.5. (M,N,Q-T) Gene expression, as indicated, in E10.5 forelimb buds as assayed by whole-mount in situ hybridization. Arrowheads in Q and R indicate expression in the mesenchyme. (O,P) Cell death in E10.5 forelimb buds assayed by LysoTracker Red staining. Limb buds are outlined by broken white lines. Abbreviations: An, anterior; D, dorsal; Di, distal; Po, posterior; Pr, proximal; V, ventral.