The targeted allele is created to have an inverted exons 8-10 ((Ensemble ID: ENSMUSE00001223455, ENSMUSE00000400411, ENSMUSE00000335250, and introns) flanked with the FLEx cassette (inward-facing lox2272:loxP sites), followed by a FRT-flanked neomycin resistance cassette. The inversion creates a reading frame shift resulting in a null allele. Flp-mediated recombination removes the neo cassette. (J:339639)