An FRT-flanked stop cassette containing a lacZ reporter, followed by loxP-flanked exon 5 and rox-flanked PGK-hygromycin cassette were inserted. Dre-recombination removed the PGK-hygromycin selection cassette. Flp mediated recombination removed the stop cassette leaving exon 5 floxed. Cre mediated recombination excised exon 5, resulting in frameshift. Western analysis confirmed lost of Setd1b protein. (J:208420)