Adenovirus-mediated inducible gene expression in vivo by a hybrid ecdysonereceptor

Precise control of transgene expression would markedly facilitate certain a pplications of gene therapy. To regulate expression of a transferred gene i n response to an exogenous compound in vivo,we modified the ecdysone-respon sive system. We combined the advantages of the Drosophila (DmEcR) and the B ombyx ecdysone receptor (BmEcR) by creating a chimeric Drosophila/Bombyx ec dysone receptor (DB-EcR) that preserved the ability to bind to the modified ecdysone promoter without exogenous retinoid X receptor (RXR). In cultured cells, DB-EcR effectively mediates ligand-dependent transactivation of a r eporter gene at lower concentrations of the chemical ecdysone agonist CS-E than VgRXR (DmEcR + RXR). Transgene delivery in vivo was achieved by intram yocardial injection of recombinant adenovirus vectors in adult rats. Upon s timulation with GS-E, DB-EcR potently (>40-fold induction) activated gene e xpression in vivo while VgRXR was not induced. This hybrid ecdysone recepto r represents an important new tool for in vivo transgene regulation with po tentially diverse applications in somatic and germline transfer.