Parkinson’s disease-associated LRRK2-G2019S mutation disrupts glianeuron crosstalk and impairs dopaminergic neurodevelopment

Accumulating evidence indicates that a complex interplay between genes and environmental factors contribute to dopaminergic (DA) neuron demise in Parkinson’s disease (PD). Among PD-associated genes, mutations in the Leucine-Rich Repeat Kinase (LRRK2) gene are the most common cause of familial late onset PD. The low penetrance of LRRK2 mutations, the low disease concordance in relatives, and the lack of substantial neurodegeneration in the LRRK2 mouse models would all suggest that other genetic or environmental hits are required for the degeneration of DA neurons. Here, we hypothesized that aging and LRRK2-mediated immune dysregulation contribute to the derangement of the neuron-glia crosstalk. To investigate the impact of LRRK2 on neuron-glia interactions, primary ventral midbrain (VM) glial-neuron cultures from wild type (Wt) and transgenic-(Tg)-LRRK2-G2019S mice were allowed to grow for different time-intervals (T=0-18 days in vitro, DIV) and fluorescence immunocytochemistry coupled with confocal laser scanning microscopy using neuronal and glial cell markers, were applied to monitor astrocyte, microglia, and mesencephalic neuron development, in either purified or mixed glia-neuron cultures. To recapitulate the interaction between G2019S with inflammatory and/or neurotoxic insults, the primary VM cultures were primed with different inflammogens and/or DA neurotoxins mimicking PD-mediated neuronal death. LRRK2 G2019S markedly affected glial morphology, neurotrophic and prosurvival properties, as reflected by the poor neuronal development and delayed acquisition of the mature DA phenotype in mixed cultures. G2019S astrocytes exhibited greater sensitivity to MPP+ and LPS challenge, enhanced production of reactive oxygen/nitrogen species, and deficient mitochondrial respiration, as compared to Wt counterparts. G2019S microglia further exacerbated astroglia activation and inhibited its neuroprotective function in mixed cultures, compared to Wt controls. These results suggest that the LRRK2-G2019S mutation disrupts glial development and impairs glia-neuron crosstalk resulting in increased vulnerability and loss of mesencephalic neurons. Current work is addressing the biochemical and molecular mechanisms underlying such LRRK2-dependent glial-neuron crosstalk. (ER-2020- 23669429 – Eranet-CoEN2017 Pathfinder)