715. Artificial Mammalian Gene Networks

Abstract

Next-generation gene therapy approaches for the treatment of complex disease phenotypes will have to deal with the precise titration of key (regulatory) proteins and complementation of entire gene regulatory networks. A growing set of adjustable gene regulation systems, operating as ON/OFF switches and responsive to small-molecule drugs, pave the way for next-generation clinical interventions. Currently available binary transcription control systems enable fine-tuning of therapeutic transgene levels only within a narrow inducer concentration range of a few nanograms/ml. We have developed a gene regulatory network tailored to lock transgene expression at desired levels in response to clinical doses of different inducers rather than different concentrations of a single inducer. The regulatory cascade was designed by interconnecting streptogramin-, macrolide- and tetracycline- repressible gene regulation systems. Four different expression levels could be achieved by clinical dosing of a single antibiotic: high expression level in the absence of any antibiotic (+++), medium level expression following addition of tetracycline (++), low level expression in response to the macrolide erythromycin (+), and complete repression by streptogramins (-). We have furthermore developed a mammalian epigenetic transcription control system, which can be switched between two stable expression states following transient integration of pharmacological signals, thus eliminating the need for sustained inducer administration. We will present the latest progress in the development of gene regulation systems, gene regulatory networks and their building blocks, as well as advances in in vivo applications and tissue engineering.