A control transgene in which a sequence cassette encoding a fusion protein composed of 1. a Tag:HA epitope, 2. the complete Ktch extracellular region (including the autoproteolytically active GAIN domain with its GPCR proteolysis site (GPS)), 3. the juxta- and transmembrane segment of N (JTS) in which the γ-secretase S3 cleavage site has been mutated, 4. the lexA::VP16 driver and 5. three copies of the Tag:V5 epitope has been inserted into the Ktch locus, resulting in expression of the fusion protein under the control of endogenous Ktch regulatory sequences. The mutation in the S3 cleavage site prevents release of the lexA::VP16 driver upon activation of Ktch.
