Exon 2 was replaced by a cassette encoding a fusion protein composed of tdTomato/C5ar2 cDNA flanked by loxP sites. The self-cleaving peptide P2A was inserted downstream of tdTomato. An frt-flanked neo-pkg was inserted upstream of the tdTomato and was removed via flp-mediated recombination leaving tdTomato and C5ar2 floxed. (J:251263)