A targeting vector was designed to insert a single loxP site upstream of exon 1 and a frt-flanked neomycin resistance cassette followed by another loxP site downstream of exon 1. Cre-mediated recombination removed the floxed neo cassette and exon 1. Western blot analysis confirmed the absence of protein in the testes. Analysis by RT-qPCR confirmed the absence of transcript in the testes, liver and lung. (J:210656)