Exons 3 through 6 were flanked by loxP sites and a neo cassette flanked by frt sites was inserted 5' of exon 3. The neo cassette was removed by Flp-mediated recombination following a cross to Gt(ROSA)26Sortm1(FLP1)Dym mice. Southern blot analysis was performed to confirm the insertions. (J:126501)