Sonic Hedgehog Promotes Patterned Regeneration in OZD Mutants.

FGF2‐soaked beads implanted into amputated chick wing buds at stage 23 up‐regulates SHH and induces limb regeneration. By stage 25, FGF2 is unable to induce SHH and regeneration, however, co‐application of FGF2 with SHH restores regeneration. Oligozeugodactyly (ozd) mutant chick wings lack limb‐specific SHH expression and SHH‐associated limb elements, i.e., ulnas and digits. We tested whether co‐application of SHH with FGF2 at stage 23 would restore normal morphology during chick wing regeneration. First, we amputated the distal 500 μm of the wing bud at stage 23 and then applied FGF2 or PBS (controls) soaked beads to the margin of the stump in normal and ozd wing buds. We also ectopically expressed SHH in a group of ozd chicks to stimulate normal pattern during regeneration. Embryos were harvested 6 days after amputation for skeletal analysis. The extent and pattern of ozd regeneration was compared to PBS and normal controls. Only the proximal humerus is retained following amputation at stage 23 in PBS controls. Application of FGF2 to ozd wings caused minimal outgrowth that was not significantly different from PBS controls (N=5). While, combined FGF and SHH application to ozd stumps generated two zeugopod bones in 50% and digits in 79% (N=14, p<0.05). Collectively, our data indicate ectopically expressed Shh in ozd chicks, enhances proliferation and promotes patterned wing regeneration following amputation. Grant Funding Source : Walter E. McPherson Society