Leucine-rich repeat kinase 2 (LRRK2) is a multifunctional protein important for maintaining cellular homeostasis. Under physiological conditions, LRRK2 is involved in regulating various cellular processes, including protein synthesis, autophagy, mitochondrial dynamics, synaptic plasticity, and neuronal survival. Mutations in the LRRK2 gene have been implicated in several diseases, including Parkinson’s disease (PD), Alzheimer´s disease (AD), and amyotrophic lateral sclerosis (ALS) among others. In PD, LRRK2 mutations are a common cause of familial and sporadic cases and thus it has been argued that LRRK2 provides a link between both PD forms. LRRK2 mutations may lead to aberrant protein aggregation, mitochondrial dysfunction, and neuroinflammation, ultimately contributing to dopaminergic neuron degeneration.
The G2019S mutation in the LRRK2 protein is the most common pathogenic mutation, accounting for up to 2% of sporadic and up to 6% of familial PD cases. The LRRK2 G2019S knock-in (KI) mouse model carries the human G2019S gain-of-function mutation within the endogenous murine LRRK2 gene. Up to an age of 12 months, LRRK2 G2019S KI/KI mice display similar cognitive and motor function compared to non-transgenic control animals.
The unique advantage of this model is that the mutant protein is expressed endogenously throughout life, which closely mimics the expression profile that appears naturally in humans. It is therefore a valuable model to test the efficacy of LRRK2 inhibitors in vivo.
Evaluation of the LRRK2 profile of 10 weeks old LRRK2 G2019S KI/KI mice showed unaltered total and pSer935 LRRK2 levels but highly increased pSer1292 LRRK2 levels in the brain (Figure 1). Treating LRRK2 G2019S KI/KI mice with the LRRK2 inhibitor MLi-2 resulted in reduced phosphorylation levels at residue Ser935 and Ser1292 for the duration of at least 8 and 2 hours, respectively (Figure 2). Treatment did not change total LRRK2 levels.
The most important characteristics of LRRK2 G2019S KI/KI mice are:
- Increased pS1292 LRRK2 levels in the brain
- Phosphorylation status modifiable by LRRK2 inhibitor MLi-2
- Unchanged total and pS935 LRRK2 levels in the brain
- Unchanged basal motor function and cognitive abilities
Figure 1. Total and phospho-LRRK2 levels in LRRK2 G2019S KI/KI mice. 10 weeks old LRRK2 G2019S KI/KI mice were evaluated for total (t)LRRK2 (A), LRRK2-pS935 (B), and LRRK2-pS1292 (C) levels using a Mesoscale Discovery (MSD) immunosorbent assay. Mean + SEM; n=8 per group, unpaired t-test. **p<0.01, ns, not significant.
Figure 2: Time-dependent inhibition of LRRK2 kinase activity upon single oral MLi-2 treatment. LRRK2 G2019S KI/KI mice received a single dose of MLi-2 or vehicle and were sacrificed 2, 8, or 24 hours later. Brain levels of total LRRK2 (A), pS935 LRRK2 (B), and pS1292 LRRK2 (C) were quantified by MSD immunosorbent assay. Mean + SEM; n = 8 per group. Two-way ANOVA with Bonferroni‘s post hoc test; **p<0.01, ***p<0.001; ns, not significant.
Scantox offers a custom-tailored study design for the LRRK2 G2019S KI/KI mouse model, and we are flexible to accommodate to your special interest. We are also happy to advise you and propose study designs. LRRK2 G2019S KI/KI mice show a relevant Parkinson’s disease (PD) phenotype at the age of 10 weeks. This grants a remarkable fast processing time of your PD study. Furthermore, non-transgenic littermates are available as control animals needed for proper study design.
We are happy to evaluate the efficacy of your compound in the LRRK2 G2019S KI/KI mouse model!
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