1. ¹Department of Neuroscience, Powell Gene Therapy Center, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, USA
2. ²Department of Neurology, University of Wisconsin, Madison, Wisconsin, USA
3. ³Department of Molecular Genetics and Microbiology, Powell Gene Therapy Center, Genetics Institute, College of Medicine, University of Florida, Gainesville, Florida, USA

Correspondence: Ronald J Mandel, Department of Neuroscience, Powell Gene Therapy Center, McKnight Brain Institute, University of Florida College of Medicine, Gainesville, Florida 32611, USA. E-mail: rmandel@ufl.edu

Received 5 July 2009; Accepted 28 July 2009; Published online 25 August 2009.

Abstract

Glial cell line-derived neurotrophic factor (GDNF) gene transfer is being developed as a treatment for Parkinson's disease (PD). Due to the potential for side effects, external transgene regulation should enhance this strategy's safety profile. Here, we demonstrate dynamic control during long-term expression of GDNF using a recombinant adeno-associated virus (rAAV)-based bicistronic tetracycline (tet)-off construct. Nigrostriatal GDNF overexpression induces body weight alterations in rodents, enabling longitudinal in vivo tracking of GDNF expression after nigral vector delivery. Regulated GDNF expression was highly sensitive to dietary doxycycline (DOX), displaying undetectable striatal GDNF levels at serum DOX levels below those required for antimicrobial activity. However, in the absence of DOX, striatal GDNF levels exceeded levels required for efficacy in PD models. We also demonstrate the absence of a series of known GDNF-associated side effects when using direct intrastriatal vector delivery. Therefore, this single rAAV vector system meets most of the requirements for an experimental reagent for treatment of PD.