A targeting vector was designed to introduce loxP sites to flank the exon encoding part of the kinase domain, encoded by amino acids 413-444. Upon transfection with a Cre-expressing plasmid, the floxed PGK-neo cassette was deleted, leaving the exon floxed. The targeting vector was designed so that Cre-mediated recombination would introduce a frameshift was created in the adjacent exon, preventing production of a functional protein. Immunoblot confirmed the lack of wild-type protein or truncated protein created by this allele in Cre-expressing ES cells. (J:94680)