The targeting construct inserted IRES, tdTomato, T2A self-cleaving peptide, iCre recombinase, and an FRT site-flanked PGK-NEO-BGHpA cassette downstream of the stop codon of the Fcgr1 gene by CRISPRCas9-mediated homologous recombination in mouse ES cells. Mice harboring the targeted allele were subsequently crossed with Rosa26FLPe mice to remove the NEO cassette. (J:338195)