A cDNA fragment containing mutated H sequence has been reintroduced into the attP site present in HattP, producing a H locus lacking introns and carrying a 7bp deletion between the second and third start codons. The mutation results in a frameshift and a premature stop codon in the p150 protein isoform. The p120 protein isoform can be produced. A residual attR site is present in the 5'UTR and a loxP cassette containing a w[+] marker is present in the 3'UTR.
Adult HCfs.w+ homozygous mutants display very severe bristle defects with, on average, 35 (out of 40 present in wild-type) of the large head and thorax bristles affected. The flies show near complete shaft-to-socket transformation of most of the macro- and microchaetae. Wing venation is less affected with small gaps in vein L5.