Fig. 5. Gene expression in Shhcre;Fgfr1 limb buds. (A,B) ß-Gal staining in (A) a Shh^cre/+;Fgfr1^co/+;R26R/+ and (B) a Shh^cre/+;Fgfr1^co/co;R26R/+ littermate E10.75 forelimb bud to label cells in which CRE has acted. (C-L) Gene expression in E10.75 (C-J) and (K,L) E11.5 forelimb buds. Shh^cre/+;Fgfr1^co/+ limb buds are used as normal control. Expression of Shh, Mkp3, Bmp4 and Hoxd13 is reduced within the CRE-active domain, while Ptch1 is reduced outside of the domain. Arrowheads indicate the posterior end of the AER. Asterisks indicate signal in the mesenchyme proximal to the end of the AER. Arrows indicate that the anterior boundaries of Bmp4 and Hoxd13 reduction corresponds to that of Fgfr1 inactivation as reported by Mkp3 reduction.