Graduation Date

Spring 5-9-2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Programs

Pharmacology and Experimental Neuroscience

First Advisor

Howard S. Fox, MD, Ph.D.

Abstract

Parkinson’s disease (PD) is neurodegenerative disorder characterized by dopaminergic neuronal loss in the substantia nigra (SN) pars compacta. Mutations in DJ-1, PINK1 and Parkin lead to PD in humans; however, in mice, mutations or knockout of these genes do not lead to disease. Development of small animal models mimicking PD pathogenesis would enable better understanding of the disease. Here, we examined two approaches using laboratory rats. First, DJ-1 knockout rats have been reported to develop movement disorders and loss of neurons similar to human PD. Comprehensive analysis of mitochondrial proteomic alteration in isolated synaptic mitochondria from DJ-1 knockout rats using mass spectrometry revealed that proteins perturbed by the loss of DJ-1 were involved in several mitochondrial functional pathways, including the TCA cycle and the electron transport chain. In addition, synaptic mitochondrial respiration was measured to assess mitochondrial function, which showed a significant change due to DJ-1 knockout.

Second, we generated a novel model of Parkinson’s disease by combining PINK1 and Parkin knockouts to create a PINK1/Parkin double knockout (DKO) rat. To characterize the model, behavioral testing was used to assess motor function and stereological counting to quantify assessed neurons . PINK1/Parkin DKO at 6 months showed a 23% reduction in dopaminergic neurons in the SN relative to wild-type rats. Neuronal loss increased to 45% in older rats (8 months of age). To understand the impact of degeneration of neurons on behavior, gait was measured using a device developed in the lab and called the RatWalker. Gait abnormalities were present at 8 months. Abnormalities were present in different gait parameters, including a reduction in hind-limb step length, a reduction in fore- and hind-limb step pressure, and an increase in step angle. Bradykinesia and agility were tested by pole test, which showed an increase in the time required to turn and to walk down the pole in 6- and 9-month old rats. Hind-limb strength assessed by cylinder test showed a significant drop in the rearing frequency at 6 and 8 months of age. Together, these projects demonstrate the importance of these genes and proteins affecting mitochondria in Parkinson’s disease in terms of both function and proteomics that would help improving our understanding of the underlying mechanisms of disease.

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