φC31 integrase and liver-specific regulatory elements confer high-level, long-term expression of firefly luciferase in mouse liver

To improve the efficiency of expression of reporter transgenes delivered by hydrodynamic injection, we generated expression cassettes carrying different liver-specific regulatory elements using the firefly luciferase gene as a reporter. From our studies the human alpha-antitrypsin promoter together with the apolipoprotein E/C-I and albumin enhancer was the combination of choice for prolonged transgene expression, but reporter gene expression in vivo lasted for no more than 7 weeks. Subsequently, phage phiC31 integrase was introduced as a potential tool to improve further the efficiency of expression of the delivered transgene. Long-term transgene expression in vivo was achieved by specific integration of the target gene into mouse livers. This study demonstrates the use of a combination of phage phiC31 integrase and liver-specific regulatory elements for generation of transgenic mice.