The gene has, from 5' to 3', a frt site, an En2 splice acceptor cassette containing a beta galactosidase sequence, and loxP-flanked neomycin cassette, containing a frt site, inserted downstream of exon 1. A third loxP-site is inserted downstream of exon 4. FLP mediated recombination removed the FRT-flanked beta galactosidase and neo cassette. Further information on targeting strategies used for this and other IKMC alleles can be found at http://www.informatics.jax.org/mgihome/nomen/IKMC_schematics.shtml.