UASt regulatory sequences drive expression of an engineered Delta c1 cDNA. The initiating ATG codon is replaced with a BspH1 restriction site which results in replacing His2 with Asn. The endogenous Delta 5'UTR is replaced with a HindIII-NcoI fragment of the Xenopus β-globin gene leader. The 3'UTR of the Delta c1 cDNA terminates 242bp 3' to the predicted stop codon and SV40 polyadenylation sequences are present.