Objective/Rationale:
In Parkinson’s disease, the major motor symptoms are caused by the degeneration of dopamine producing neurons in the substantia nigra pars compacta. We have identified a neuroprotective molecule involved in synapsin vesicle function called RAB3B, which we have shown can enhance function and prevent dopamine neurons from dying in a pre-clinical model of Parkinson’s disease caused by oxidative stress. We will now test RAB3B in a second pre-clinical model of Parkinson’s disease caused by the overexpression of alpha-synuclein.
Project Description:
We will use gene therapy to test the capacity of RAB3B to protect dopamine neurons from degeneration in our recently developed pre-clinical model of alpha-synucleinopathy. Our AAV-alpha-synucleinopathy pre-clinical model exhibits a slow pattern of degeneration of dopamine neurons, and we have shown that the cell death is preceded by several pre-degenerative changes, which we have characterized. Using gene delivery, we will co-inject RAB3B and alpha-synuclein into the substantia nigra and determine at different time points after the injection, whether RAB3B can prevent the alpha-synuclein-induced pathological changes that occur to dopamine neurotransmission, synapses (the points of communication between neurons), nerve fibers and axonal transport (the transport of molecules within the neuron).
Relevance to Diagnosis/Treatment of Parkinson’s Disease:
Current treatments for Parkinson’s disease are mainly Symptoms & Side Effects and do not prevent the dopamine neurons from dying. Our AAV-alpha-synucleinopathy model allows us to test neuroprotection against early degenerative changes, which is line with our hypothesis that effective neuroprotective approaches in the clinic will require neuroprotective treatments to begin early in the disease course, when neurons are still responsive to treatment. We believe that these gene therapy studies with RAB3B will provide a rational and effective means to establish a meaningful pre-clinical foundation to support future assessment of RAB3B in non-human primate models of Parkinson’s disease, and subsequent clinical trials.
Anticipated Outcome:
Upon successful completion of this project, we will have a completed dataset for showing the neuroprotective efficacy of gene therapy with RAB3B in a pre-clinical model of Parkinson’s disease. We will learn how RAB3B gene therapy can improve neurotransmission, synaptic function and axonal transport in this experimental model.
Progress Report
In this project we are examining whether gene therapy of our neuroprotective candidate, RAB3B, can protect against pathological changes in vulnerable dopamine neurons in a pre-clinical model of alpha-synucleinopathy. We have performed co-injections of RAB3B and alpha-synuclein, or RAB3B and GFP (our control gene) into the substantia nigra of these models. We have previously shown that in our model of alpha-synucleinopathy, the degeneration of substantia nigra dopamine neurons is preceded by a change in dopamine homeostasis in the striatum, indicating that the terminals of the dopamine neurons are dysfunctional before the neurons themselves die. Our data now shows that when RAB3B is overexpressed in this model, the changes in dopamine homeostasis are normalized, suggesting that RAB3B overexpression helps the dopamine neurons to maintain dopamine levels in the striatum. We are currently also performing post-mortem analysis in the RAB3B and alpha-synuclein co-injected models to examine whether RAB3B prevents alpha-synuclein-induced pre-degenerative changes to dopamine fibers and synaptic proteins.
Final Outcome
In this project we are examining whether gene therapy of our neuroprotective candidate, RAB3B, can protect against pathological changes in vulnerable dopamine neurons in a pre-clinical model of alpha-synucleinopathy. We performed co-injections of RAB3B and alpha-synuclein, or alpha-synuclein and GFP (our control gene), or GFP alone, into the substantia nigra of the models. We have previously shown that in our model of alpha-synucleinopathy , the degeneration of substantia nigra dopamine neurons is preceded by alterations to presynaptic proteins and axonal transport proteins, as well a change in dopamine homeostasis in the striatum, indicating that the terminals of the dopamine neurons are dysfunctional before the neurons themselves die. Our data now shows that when RAB3B is overexpressed in this model, several changes in synaptic and axonal transport proteins, as well as striatal dopamine homeostasis, are normalized, suggesting that RAB3B overexpression can provide functional and synaptic rescue for up to 17 weeks in this model of alpha-synucleinopathy. Combined with our previously published data showing that RAB3B overexpression can protect dopamine neurons in another pre-clinical model of Parkinson’s disease caused by oxidative stress, these data are promising for further development of RAB3B overexpression as a therapeutic target for Parkinson’s disease.
July 2012