By using CRISPR/Cas9 technology in ES cells, the exon 5 (ENSMUSE00000216525) was flanked by loxP sequences and was followed by the Pgk-neo cassette flanked by Frt sequences. The Pgk-neo cassette was removed by crossing with Rosa-Flp mice. Cre-mediated recombination removed exon 5. (J:329565)