The CRIMIC-TG4 collection (FBlc0003479), described in Lee et al., 2018, eLife 7: e35574 (FBrf0238661) consists of a set of stocks that each contain a Trojan-GAL4 gene trap sequence in a coding intron, inserted via CRISPR/Cas9-induced homology directed repair. The inserted cassette acts contains a 'Trojan GAL4' gene trap element composed of a splice acceptor site followed by the T2A peptide, the GAL4 coding sequence and an SV40 polyadenylation signal. When inserted in a coding intron in the correct orientation, the cassette should result in truncation of the trapped gene product and expression of GAL4 under the control of the regulatory sequences of the trapped gene. A PCR assay was used to to validate CRISPR/Cas9-induced homology directed repair events. In addition, the inserted DNA sequence contains a pair of inverted attP sites, which allows for the entire cassette to be replaced with DNA from a compatible donor plasmid (where the sequence to be inserted is flanked by inverted attB sites) through recombination-mediated cassette exchange (RMCE) driven by the phiC31:int integrase. The 'Associated Files' for this personal communication consist of .xlsx files that were submitted to FlyBase at the time that each set of the fly stocks was sent to the Bloomington Drosophila Stock Center. The .xlsx files contain data primarily concerning the genomic location of the inserted DNA, the length of any associated small deletion of genomic DNA and the identities of any gene(s) in which the Trojan-GAL4 cassette is inserted. The gene associations are based on the FlyBase gene annotations at the time of submission of the data. The column "Trap? Y/N" for each gene indicates whether the gene trap cassette is predicted to result in the truncation of the trapped gene and expression of GAL4. Note that this is a prediction and does not necessarily indicate whether or not there is experimental evidence. GAL4 is predicted to be expressed only in cells expressing a transcript isoform in which the insertion acts as a gene trap (i.e. is inserted in an intron between two protein coding exons). For genes with multiple annotated transcript isoforms, a "Y" (Yes) in the 'Traps_all_Gene_transcripts? _Y_N' column indicates that the insertion is predicted to trap all isoforms of the gene.