Expression of Shh and Ptch1 in Gli3;Neo1 double mutants. Whole mount in situ hybridization analysis Shh and Ptch1 expression in E11.5 embryos of the indicated genotypes. Black arrowheads indicate ectopic anterior expression of Shh, red arrowheads indicate ectopic anterior expression of Ptch1. Wt, wild-type. LF, left forelimb; RF, right forelimb; LH, left hindlimb; RH, right hindlimb; all sets of limb buds correspond to the positions identified for the Wt set in the upper left of the figure.