UASt regulatory sequences drive expression of a mutant form of en in which the eh1 motif has been have been changed from LAFSISNILSDRFG to LAASASAAASDRAA (encoded by 5'-CTGGCCGCTTCCGCCTCCGCCGCCGCGAGCGATCGTGCCGCA-3') and the ehIFRPF motif has been changed from IFRPF to IAAAA (encoded by 5'-ATAGCCGCCGCCGCC-3'). A 5'-GGCGCC-3'Kozak sequence has been added immediately upstream of the start site.