This transgene contains five upstream activating sequence (UAS) elements, a Wnt1 promoter, the rat Smo cDNA containing a W539L mutation, the human placental alkaline phosphatase cDNA under the control of an internal ribosomal entry site, lacZ, and a poly A signal from the murine Wnt1 gene. UAS elements drive the expression of the mutated ligand-independent activated rat Smo gene. Expression of this transgene is dependent on GAL4 expression.