The coding region containing all 3 exons was replaced with a loxP-flanked Ascl2 cDNA with a 5' triple-FLAG epitope and a 3' mCherry cDNA separated from Ascl2 by a P2A cleavage sequence. An frt-flanked neomycin selection cassette was also inserted before the second loxP site and removed via Flp-mediated recombination. (J:307135)