Progressive dopaminergic alterations and mitochondrial abnormalities in LRRK2 G2019S knock-in mice

Abstract

Mutations in the LRRK2 gene represent the most common genetic cause of late onset Parkinson’s disease. The physiological and pathological roles of LRRK2 are yet to be fully determined but evidence points towards LRRK2 mutations causing a gain in kinase function, impacting on neuronal maintenance, vesicular dynamics and neurotransmitter release. To explore the role of physiological levels of mutant LRRK2, we created knock in mice harboring the most common LRRK2 mutation G2019S in their own genome. We have performed comprehensive dopaminergic, behavioral and neuropathological analyses in this model up to 24 months of age. We find elevated kinase activity in the brain of both heterozygous and homozygous mice. Although normal at 6 months, by 12 months of age, basal and pharmacologically induced extracellular release of dopamine is impaired in both heterozygous and homozygous mice, corroborating previous findings in transgenic models over-expressing mutant LRRK2. Via in vivo microdialysis measurement of basal and drug- evoked extracellular release of dopamine and its metabolites, our findings indicate that exocytotic release from the vesicular pool is impaired. Furthermore, profound mitochondrial abnormalities are evident in the striatum of older homozygous G2019S mice, which are consistent with mitochondrial fission arrest. We anticipate the G2019S will be a useful pre-clinical model for further evaluation of early mechanistic events in LRRK2 pathogenesis and for second-hit approaches to model disease progression.

MLi-2, a Potent, Selective, and Centrally Active Compound for Exploring the Therapeutic Potential and Safety of LRRK2 Kinase Inhibition

“…The most common variant, G2019S, occurs within the LRRK2 kinase activation loop and results in increased kinase activity (West et al, 2005;Greggio et al, 2006). Preclinical observations of increased susceptibility to dopaminergic neurotoxins, mitochondrial dysfunction, and elevated a-synuclein in human LRRK2 mutant carrier-derived induced pluripotent stem cell (iPSC) models and G2019S knockin mice further confirm a toxic gain-of-function for kinase-activated mutations (Nguyen et al, 2011;Reinhardt et al, 2013;Sanders et al, 2014;Yue et al, 2015). Interestingly, GTPase domain variants R1441G, Y1699C, and N1437H also increase LRRK2 kinase activity (Sheng et al, 2012), suggesting the kinase domain is commonly and consistently dysregulated by many pathogenic LRRK2 mutations.…”

LRRK2 G2019S transgenic mice display increased susceptibility to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-mediated neurotoxicity

“…LRRK2 mutant Drosophila also show increased sensitivity to rotenone (Ng et al , 2009). LRRK2 G2019S knockin mice exhibit striatal mitochondrial abnormalities late in life (Yue et al , 2015). DA neurons derived from human inducible pluripotent stem cells (iPSCs) also exhibit mitochondrial defects (Sanders et al , 2014) and enhanced sensitivity to mitochondrial toxins, including rotenone (Cooper et al , 2012).…”

“…Mutations in the leucine-rich repeat kinase 2 (LRRK2), which leads to late-onset PD with an autosomal dominant pattern of inheritance, are prime examples of genetic variants that cause PD susceptibility (Dawson et al , 2010; Martin et al , 2011; Martin et al , 2014b; Rajput et al , 2006; Yue et al , 2015; Zimprich et al , 2004). LRRK2 is a large multi-domain protein that includes central catalytic domains with GTPase and kinase activities and surrounding protein-protein interaction domains (Sanders et al , 2014; Xiong et al , 2010).…”

LRRK2 Expression in the Enteric Nervous System: ENSuring Its Significance

“…Although interesting and provocative, these results, far from definitive, need to be replicated in another animal model of PD. Given the possible contributions of LRRK2 to the ENS, it would be tempting to evaluate the effect of microbiota from PD patients in LRRK2 transgenic mice, such as mice bearing the G2019S LRRK2 mutation [9].…”