The Parkinson's Disease-Associated Mutation LRRK2-G2019S Impairs Synaptic Plasticity in Mouse Hippocampus

Parkinson's disease (PD) is a major movement disorder characterized by the loss of dopamine neurons and formation of Lewy bodies. Clinical and pathological evidence indicates that multiple brain regions are affected in PD in a spatiotemporal manner and are associated with a variety of motor and nonmotor symptoms, including disturbances in mood, executive function, and memory. The common PD-associated gene for leucine-rich repeat kinase, leucine-rich repeat kinase 2 (LRRK2), is highly expressed in brain regions that are involved with nonmotor functions, including the neocortex and hippocampus, but whether mutant LRRK2 contributes to neuronal dysfunction in these regions is unknown. Here, we use bacterial artificial chromosome transgenic mouse models of LRRK2 to explore potential nonmotor mechanisms of PD. Through electrophysiological analysis of the Schaffer collateral-CA1 synapse in dorsal hippocampus, we find that overexpression of LRRK2-G2019S increases basal synaptic efficiency through a postsynaptic mechanism, and disrupts long-term depression. Furthermore, these effects of the G2019S mutation are age dependent and can be normalized by acute inhibition of LRRK2 kinase activity. In contrast, overexpression of wild-type LRRK2 has no effect under the same conditions, suggesting a specific phenotype for the G2019S mutation. These results identify a pathogenic function of LRRK2 in the hippocampus that may contribute to nonmotor symptoms of PD.