Figure 6.

The GRS1 transgene is controlled by both SHH and BMP activity. (A) GRS1-dependent ß-galactosidase activity is completely lost from Shh-deficient limb buds (Shh^Δ/ΔGRS1^tg10/+). (B) In contrast, inactivation of Gli3 results in anterior up-regulation of ß-galactosidase activity at E11.75 (Gli3^Xt/XtGRS1^tg10/+). (C) ß-galactosidase activity fails to expand anteriorly in Smad4-deficient limb buds (Smad4^Δ/ΔMGRS1^tg10/+). (D) ß-galactosidase activity is up-regulated in Grem1-deficient limb buds from E11.0 onward (Grem1^Δ/ΔGRS1^tg10/+).