UASt regulatory sequences drive expression of a mutant form of smo in which the all three basic amino acid clusters in the juxtamembrane region of the C-tail have been mutated (amino acid replacements R565A, K569A, K570A, K593A, R594A, K595A, K645A, R646A and R647A). The protein is tagged at the N-terminal end with Tag:MYC.