The Trojan-Gal4 expression module (T-GEM) is an attP cassette which contains a Trojan GAL4 exon (composed of a splice acceptor site followed by the T2A peptide, the GAL4 coding sequence and an Hsp70 transcription termination signal) followed by a loxP cassette containing the Disc\RFP3xP3.PB marker. Integration of this cassette into a coding intron of a native Drosophila gene of interest using CRISPR/Cas9 technology can result in the cassette behaving as a 'Trojan' exon: the splice acceptor site ensures that the T2A-GAL4 open reading frame is incorporated into the mRNA of the native Drosophila gene, while the T2A sequence truncates the native gene product and promotes the separate translation of the GAL4 open reading frame. Thus GAL4 should be expressed under the control of the regulatory sequences of the native Drosophila gene of interest in the resulting fly line.
