AQP2 and autosomal dominant polycystic kidney disease: Since mice with homozygous mutations of Pkd1 die in utero, we generated an ADPKD mouse model in which Pkd1 is conditionally knocked out only in the collecting duct by conjugating Cre recombinase to the promoter of the AQP2 gene, which is expressed only in the collecting duct of the kidney [25].