afimoxifene and Parkinson-Disease

Regulation of gene expression is necessary to avoid possible adverse effects of gene therapy due to excess synthesis of transgene products. To reduce transgene expression, we developed a viral vector-mediated somatic regulation system using inducible Cre recombinase. A recombinant adeno-associated virus (AAV) vector expressing Cre recombinase fused to a mutated ligand-binding domain of the estrogen receptor alpha (CreER(T2)) was delivered along with AAV vectors expressing dopamine-synthesizing enzymes to rats of a Parkinson disease model. Treatment with 4-hydroxytamoxifen, a synthetic estrogen receptor modulator, activated Cre recombinase within the transduced neurons and induced selective excision of the tyrosine hydroxylase (TH) coding sequence flanked by loxP sites, leading to a reduction in transgene-mediated dopamine synthesis. Using this strategy, aromatic L-amino acid decarboxylase (AADC) activity was retained so that l-3,4-dihydroxyphenylalanine (L-dopa), a substrate for AADC, could be converted to dopamine in the striatum and the therapeutic effects of L-dopa preserved, even after reduction of TH expression in the case of dopamine overproduction. Our data demonstrate that viral vector-mediated inducible Cre recombinase can serve as an in vivo molecular switch, allowing spatial and temporal control of transgene expression, thereby potentially increasing the safety of gene therapy.

Topics: Animals; Aromatic-L-Amino-Acid Decarboxylases; Cell Line; Corpus Striatum; Dependovirus; Disease Models, Animal; Dopamine; Estrogen Receptor alpha; Estrogen Receptor Modulators; Genetic Therapy; Genetic Vectors; Humans; Integrases; Levodopa; Male; Mice; Neurons; Parkinson Disease; Rats; Rats, Wistar; Recombination, Genetic; Stereotyped Behavior; Tamoxifen; Tyrosine 3-Monooxygenase; Viral Proteins