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'. A 5'-GGCGCC-3' Kozak sequence has been added immediately upstream of the start site.