A sequence cassette encoding T2A-lexA::GAD (with an Hsp70 terminator sequence) followed by a loxP cassette containing a Disc\RFPDsRed.3xP3.cUa marker has been inserted into the endogenous nAChRβ3 locus. The cassette was inserted using the CRISPR/Cas9 technique together with a donor plasmid to drive homology directed repair.