An FRT flanked lacZ-neo cassette and loxP site were inserted upstream of exon 7 and Rox flanked hyg-pgk cassette and loxP site were inserted downstream of exon 7 via homologous recombination. Flp and Dre mediated recombination removed the selection cassettes. Cre mediated recombination removed exon 7. Western blot analysis confirmed the absence of full length protein in testis extracts from hemizygous male mice (J:278848)