According to the allele image posted by EUCOMMTOOLS in the international knockout mouse consortium site (https://www.mousephenotype.org/imits/targ_rep), exons 4 and 5 are flanked by loxP sites and a cre/ERT2-EGRP cassette preceded by a single FRT site and followed by a Rox flanked puromycin selection cassette was inserted into the intron between exons 3 and 4. (J:155845)