Neuronal expression of the transcription factor Gli1 using the Tα1 α-tubulin promoter is neuroprotective in an experimental model of Parkinson's disease

Abstract

Nigrostriatal neurons degenerate during Parkinson's disease. Experimentally, neurotoxins such as 6-hydroxydopamine (6-OHDA) in rodents, and MPTP in mice and nonhuman primates, are used to model the disease-induced degeneration of midbrain dopaminergic neurons. Glialcell-derived neurotrophic factor (GDNF) is a very powerful neuroprotector of dopaminergic neurons in all species examined. However, recent reports have indicated the possibility that GDNF may, in the long term and if expressed in an unregulated manner, exert untoward effects on midbrain dopaminergic neuronal structure and function. Although GDNF remains a powerful neurotrophin, the search for alternative therapies based on alternative and complementary mechanisms of action to GDNF is warranted. Recently, recombinant adenovirus-derived vectors encoding the differentiation factor Sonic Hedgehog (Shh) and its downstream transcriptional activator (Gli1) were shown to protect dopaminergic neurons in the substantia nigra pars compacta from 6-OHDA-induced neurotoxicity in rats in vivo. A pancellular human CMV (hCMV) promoter was used to drive the expression of both Shh and Gli1. Since Gli1 is a transcription factor and therefore exerts its actions intracellularly, we decided to test whether expression of Gli1 within neurons would be effective for neuroprotection. We demonstrate that neuronal-specific expression of Gli1 using the neuron-specific Ta1 a-tubulin (Ta1) promoter was neuroprotective, and its efficiency was comparable to the pancellular strong viral hCMV promoter. These results suggest that expression of the transcription factor Gli1 solely within neurons is neuroprotective for dopaminergic neurons in vivo and, furthermore, that neuronal-specific promoters are effective within the context of adenovirus-mediated gene therapy-induced neuroprotection of dopaminergic midbrain neurons. Since cell-type specific promoters are known to be weaker than the viral hCMV promoter, our data demonstrate that neuronal-specific expression of transcription factors is an effective, specific, and sufficient targeted approach for neurological gene therapy applications, potentially minimizing side effects due to unrestricted promiscuous gene expression within target tissues.

Roles for Hedgehog signaling in adult organ homeostasis and repair

“…Indeed, SHH signaling has previously been demonstrated to protect dopaminergic neurons from neurotoxic effects (Dass et al, 2005;Hurtado-Lorenzo et al, 2004;Suwelack et al, 2004). As midbrain dopaminergic neurons also project to the SVZ (Lennington et al, 2011), along with other neuronal populations (Berg et al, 2013), it is possible that anterograde movement of SHH protein along axons allows the delivery of the protein to both the SVZ and striatum (Fig.…”

Regulatable Gutless Adenovirus Vectors Sustain Inducible Transgene Expression in the Brain in the Presence of an Immune Response against Adenoviruses

“…Brain sections containing the needle track (area of highest levels of immunoreactivity) were used for quantitative analysis. Student's t test was used to determine the degree of statistical significance between values from each time point for naïve and preimmunized animal groups (52).…”

AAV-Based Targeting Gene Therapy

“…The application of AAV2 mosaics with a protein A fragment inserted into their capsid, together with targeting antibodies, is a versatile method that allows the specific transduction of a wide array of cell types [32] . VEGF peptide, EGF peptide, FGF peptide, LH peptide have also been studied for their targeting function from different group [6,23,72,87,99] .…”