Mice heterozygous for Efnb2tm3Kln were bred with mice expressing a cre recombinase transgene, resulting in the excision of the floxed neo gene. The inserted cDNA encoding the truncated protein lacking 66 residues of carboxy terminal region and containing a hemagglutinin (HA) epitope tag, was left intact. The expression pattern of the targeted allele was determined to resemble that of the wild-type allele via in situ hybridization. Analysis using modified receptors showed localization to the cell surface. Production of protein with a reduced molecular weight was verified by immunoblotting with an anti-HA antibody. (J:67296)