PD is a progressive degenerative neurological disease that affects about 1% of the population over age 55. Although there are many variants of the disease, a common strand that links these variants is damage to a finite group of dopaminergic (DA) neurons in the midbrain. As these neurons are lost in PD, CNS function and in particular its control over normal muscular function declines. Tremor is a well-known symptom which characterizes PD, but sleep, digestion, cognition, and mobility are also affected with increasing severity as the disease progresses. Current therapies, such as dopamine replacement therapy, only address symptoms and there is an urgent need for a disease-modifying therapy.