CRISPR/cas9 endonuclease-mediated genome editing was used to insert an in frame protein containing IRES-followed by F3-FRT-Cre-F3-FRT in reverse orientation into the 3' UTR of the gene. The cassette contained approximately 1 kb of 5' and 5' flanking homology arm sequence. Expression of Flpo recombinase recombines cre to the correct orientation. (J:325967)