Replacement of the endogenous VAChT locus with a donor fragment containing a FRT-flanked cassette with a transcriptional terminator (Hsp70Ab polyadenylation signal) and a screenable eye marker (Disc\RFP^{DsRed.3xP3.cUa}), along with a Kozak sequence followed by the VAChT ORF tagged with Tag:HA after the first 14 amino acids from the N-terminus. In the absence of FLP recombinase, the presence of the FRT cassette prevents transcription of VAChT. If the FRT cassette is excised (by providing a source of FLP), VAChT is expressed, but expression is restricted to those cells in which both the active endogenous regulatory sequences of VAChT are active and in which the FLP recombinase is expressed.