The newly identified LRRK2, a disease gene of familial dominant late-onset ParkS, encodes a kinase. No mouse models are available for ParkS; no LRRK2 kinase substrates are known; and little is known about LRRK2 normal functions and pathogenic roles in Parkinson's disease. In this early exploratory phase of research which is most suitable for R21 mechanism, we have established LRRK2 mouse models and now propose to characterize them, and utilize these new mouse models to identify LRRK2 substrates. Mutations in LRRK2 have been identified as the most prevalent ones in familial Parkinson's disease, as well as in sporadic PD unexpectedly. All ParkS mutations are missense mutations that cause a dominant phenotype, indicating a "gain of function" or "hyperactivity" mechanism of mutant proteins for pathogenesis. Therefore, transgenic (not knockout) mouse models are appropriate for modeling ParkS. Our CENTRAL HYPOTHESIS is that ParkS pathology is caused by hyperactivity of the mutant LRRK2 to hyper-phosphorylate its substrates. To test this hypothesis, we have generated transgenic LRRK2 mice that carry wild type sequence or ParkS mutations in HUMAN bacterial artificial chromosome (BAG). SPECIFIC AIM 1: to analyze the phenotypes of the LRRK2 transgenic mice for progressive behavioral deficits in motor function and in niagrostriatal pathways, neuronal pathology in substantia nigra, and dopamine production and release. SPECIFIC AIM 2: to use our new mouse models to identify substrates of LRRK2 kinase with both candidate and non-biased approaches. SIGNIFICANCE: Mouse models for ParkS will be critical tools for mechanistic studies and future therapeutic drug testing. The identification of LRRK2 substrates is important because kinase pathways and components are highly "drug-able" targets. The study of LRRK2 is also very likely to impact sporadic PD research, because ParkS mutation G2019S was discovered to be also highly prevalent in sporadic PD. [unreadable] [unreadable] [unreadable]