Figure 2. Shh^Δ/flox;Hoxb6CreER^T Skeletal Phenotypes after Tam-Induced Shh Removal at E10.5, E10, or E9.5, with Progressive Loss of Digits d3, d5, d2, and d4.

(A) Hindlimb skeletal phenotypes at E17.5 compared to sibling controls (as in Figure 1) at left, and schematic of wild-type limb skeleton showing different digits color-highlighted with their associated distal tarsal element, which was typically lost together with the overlying digit. Sometimes attenuated digits (asterisk) were observed prior to complete loss.

(B) Forelimb skeletal phenotypes at E17.5 (or E16.5 for E10 Tam) with controls and wild-type schematic showing carpals associated with specific digits.

(C) Hindlimb skeletons of E10 Tam-treated sibling embryos collected at E14.5, showing progressive loss of d3 followed by d5 at a very early skeletal stage, with unambiguous digit assignment based on very different initial tarsal sizes (note much larger size of the posterior-most tarsal in each case), and different lengths of d4 and d5. As the fibula is reduced or lost, the position of d4 and associated tarsal shift anteriorly to overlie the tibia.