Expression of Cbl cDNA is driven by an Hsp70 promoter and two copies of sev enhancer.
photoreceptor cell R7
In sev6; SosJC2 double heterozygotes an R7 cell develops in only 17% of the ommatidia, raising the level of Cbl essentially eliminates development of R7 cells. Expression in wild type flies does not alter the wild type phenotype.