We have demonstrated the first successful use of neuronal-orexin gene transfer to ameliorate symptoms of narcolepsy in two established animal models of the disease. The effects were site specific and depended on the connectivity of the surrogate neurons. Since neuronal orexin can be secreted at multiple distal sites, some of which may regulate narcoleptic behavior whereas others do not, we propose a localized gene delivery method by expressing orexin in astroglia. Astroglial-orexin will re-establish the ligand-receptor link in a localized area that already contains the orexin receptors. Astroglial-orexin gene deliver will serve as a cost-effective neurobiological tool to understand the networking underlying sleep.
In aim 1 the gene for orexin will be inserted into astroglia (GFAP promoter driven) in three specific brain regions, two of which are implicated in network sleep models (TMN, pons) and the third, striatum, will serve as control. Our preliminary results in the orexin-ataxin-3 mice model indicate that in the TMN glial-orexin (rAAV-GFAP-orexin) completely rescues waking but not cataplexy. In the pons it produces a 78% reduction in cataplexy but not waking. Thus, there is site- specificity of the glial-orexin.
In aim 2 astroglial-orexin will be driven by optogenetic stimulation to determine whether such stimulation further stimulates waking or blocks cataplexy, especially in ineffective sites in aim 1. Experiments with appropriate controls, including orexin receptor antagonist are proposed to strengthen the conclusions. In-vitro calcium imaging study will determine functionality of the genetically inserted ChR2 receptors. To the best of our knowledge this is the first use of astroglial-orexin in sleep disorders. Gene transfer is extremely cost-efficient, it is used clinically and it will demonstrate that genetic pharmacology can be used to elucidate the network in sleep disorders.
The significance of this project is that it will establish proof-of-concept that astroglial-orexin release is able to have site-specific and symptom-specific effects on sleep. The lasting impact of this project will be that astroglial-orexin release can serve as a tool to understand the networking underlying the sleep disorder, narcolepsy. This tool will also aid in development of pharmaceutical agents targeted to specific nodes in the circuit.