Microglia-induced neurotoxicity and altered cell-autonomous functions in a LRRK2 G2019S model of Parkinson’s disease

Abstract

Mutations in LRRK2 are linked to the most common form of heritable, late-onset Parkinson’s disease, and the LRRK2 G2019S substitution is the most common LRRK2 mutation in PD patients. PD is characterized by extensive death of dopaminergic neurons in the substantia nigra region of the midbrain, and significant work has been devoted to understanding the impact of the G2019S kinase-activating mutation on the health, sensitivity, and cell-autonomous function of neurons. However, an extensive body of evidence has emerged over the past decade to suggest that glial cells can induce non-cell-autonomous neurodegeneration. Motivated by these findings, we evaluated the ability of LRRK2 G2019S microglia to impact dopaminergic neuron survival. Using a co-culture system in which the genotype of each cell type can be controlled, we observed a significant loss of dopaminergic neurons in the presence of LRRK2 mutant microglia. We further observed dopaminergic neurotoxicity induced by conditioned medium collected from LRRK2 G2019S microglia. In an attempt to better understand the microglia-intrinsic effects of the LRRK2 mutation, we assayed multiple LRRK2-relevant organelles and cell biological pathways. We found that LRRK2 G2019S microglia display increased mitochondrial fragmentation, decreased phagocytic activity, impaired endosome maturation, altered microtubule dynamics, and elevated chemotaxis activity in comparison to wild-type controls. Taken together, our results suggest that the LRRK2 G2019S mutation impacts microglial homeostasis and can lead to non-cell-autonomous dopaminergic neurodegeneration.