Efficient liver-specific deletion of a floxed human angiotensinogen transgene by adenoviral delivery of Cre recombinase in vivo

Tissue-specific ablation of gene function is possible in vivo by the Cre-lo xP recombinase system. We generated transgenic mice containing a human angi otensinogen gene flanked by loxP sites (hAGT(flox)). To examine the physiol ogic consequences of tissue-specific loss of angiotensinogen gene function in vivo, we constructed an adenovirus expressing Cre recombinase. Studies w ere performed in several independent lines of hAGT(flox) mice before and af ter intravenous administration of either Adcre or Ad beta Gal as a control. Systemic administration of Adcre caused a significant decrease in circulat ing human angiotensinogen and markedly blunted the presser response to admi nistration of purified recombinant human renin. Southern blot analysis of g enomic DNA from various organs revealed that the Cre-mediated deletion was liver-specific. Further analysis revealed the absence of full-length human angiotensinogen mRNA and protein in the liver but not the kidney of Adcre m ice, consistent with the liver being the target for adenoviruses administer ed intravenously, These studies demonstrate that extra-hepatic sources of a nsotensinogen do not contribute significantly to the circulating pool of an giotensinogen and provide proof-of-principle that the Cre-loxP system can b e used effectively to examine the contribution of the systemic and tissue r enin-angiotensin system to normal and pathological regulation of blood pres sure.