The floxed exon 3 was removed from Aco1tm1.1Mwh by mating with mice expressing Tg(Pgk1-cre)1Lni, creating a null allele. Removal of exon 3 creates a frameshift with premature termination of translation in exon 4. Western blotting confirmed absence of protein in kidney, duodenum, liver and spleen extracts. (J:103414, J:104538)