Ecdysone-Based-Tet-On Expression System.

Inducible gene expression systems offer great potential toward achieving a wide variety of basic and applied biomedical research goals. Current inducible gene technologies are based on binary transgenic systems in which the expression of a target gene is dependent upon the activity of a unique transcriptional activator in the presence or absence of its drug ligand. Despite the conceptual simplicity, most gene inducible strategies suffer from a number of limitations, such as leaky basal transcriptional activity when uninduced and poor dynamic control of the system. Because of these shortcomings, regulated gene expression technologies are still being evaluated using stringent genetic studies and none are currently used in human gene therapy. To overcome some of the disadvantages of the current systems, we describe the development of a next-generation inducible gene expression system, which relies upon multiple heterologous transactivators and their respective ligands. Our system would provide negative/positive selection for transgene expression in its induced state that would create virtually no transgene expression when not induced (i.e., no leakage). We propose a strategy to engineer expression systems that include heterodimeric hormone receptors combined with other heterologous transactivators.