Flp-mediated excision of the parental Nae1tm1a(EUCOMM)Wtsi allele resulted in the removal of the promoter-driven neomycin selection cassette and lacZ cassette leaving exon 4 floxed. 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 (J:261328)