Sequence for the human diphtheria toxin receptor (HBEGF) cDNA, an IRES, the EYFP fluorescent reporter gene, a loxP site, the mouse Ace (angiotensin I converting enzyme (peptidyl-dipeptidase A) 1) promoter, the cre recombinase gene, a neomycin resistance gene cassette, and a second loxP site, was inserted after the ATG translation start site, abolishing endogenous translation of the host gene in the allele. Cre-mediated recombination in the male germline removed the cre+neo cassette. No YFP expression was detected.