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Updated: Dec 20, 2025
Assaying the Kinase Activity of LRRK2 in vitro
Published on: January 18, 2012
The effect of LRRK2 loss-of-function variants in humans
Nicola Whiffin1,2,3, Irina M Armean4,5, Aaron Kleinman6
1National Heart & Lung Institute and MRC London Institute of Medical Sciences, Imperial College London, London, UK. n.whiffin@imperial.ac.uk.
Abstract:
Human genetic variants predicted to cause loss-of-function of protein-coding genes (pLoF variants) provide natural in vivo models of human gene inactivation and can be valuable indicators of gene function and the potential toxicity of therapeutic inhibitors targeting these genes1,2. Gain-of-kinase-function variants in LRRK2 are known to significantly increase the risk of Parkinson's disease3,4, suggesting that inhibition of LRRK2 kinase activity is a promising therapeutic strategy. While preclinical studies in model organisms have raised some on-target toxicity concerns5-8, the biological consequences of LRRK2 inhibition have not been well characterized in humans. Here, we systematically analyze pLoF variants in LRRK2 observed across 141,456 individuals sequenced in the Genome Aggregation Database (gnomAD)9, 49,960 exome-sequenced individuals from the UK Biobank and over 4 million participants in the 23andMe genotyped dataset. After stringent variant curation, we identify 1,455 individuals with high-confidence pLoF variants in LRRK2. Experimental validation of three variants, combined with previous work10, confirmed reduced protein levels in 82.5% of our cohort. We show that heterozygous pLoF variants in LRRK2 reduce LRRK2 protein levels but that these are not strongly associated with any specific phenotype or disease state. Our results demonstrate the value of large-scale genomic databases and phenotyping of human loss-of-function carriers for target validation in drug discovery.
Insights
Loss-of-function variants in the LRRK2 gene reduce protein levels but do not appear to cause specific health issues in humans. This research supports using genetic data to validate drug targets for diseases like Parkinson's.
Area of Science:
- Genetics
- Neuroscience
- Pharmacology
Background:
- Human genetic variants causing protein loss-of-function (pLoF) serve as in vivo models for gene function and drug toxicity.
- Gain-of-kinase-function variants in LRRK2 are linked to increased Parkinson's disease risk, making LRRK2 inhibition a potential therapeutic strategy.
- Preclinical studies suggest on-target toxicity concerns for LRRK2 inhibitors, but human data on LRRK2 inhibition consequences are limited.
Purpose of the Study:
- To investigate the biological consequences of LRRK2 inhibition in humans by analyzing loss-of-function variants.
- To assess the association between LRRK2 loss-of-function variants and specific phenotypes or disease states.
- To evaluate the utility of large-scale genomic databases and human loss-of-function data for drug discovery target validation.
Main Methods:
- Systematic analysis of LRRK2 pLoF variants across large-scale genomic datasets (gnomAD, UK Biobank, 23andMe).
- Identification and curation of high-confidence LRRK2 pLoF variants in over 1,400 individuals.
- Experimental validation of variant effects on protein levels and correlation with phenotypic data.
Main Results:
- Identified 1,455 individuals with high-confidence heterozygous pLoF variants in LRRK2.
- Confirmed reduced LRRK2 protein levels in 82.5% of analyzed variants.
- Found no strong association between heterozygous LRRK2 pLoF variants and specific phenotypes or disease states.
Conclusions:
- Heterozygous loss-of-function variants in LRRK2 reduce protein levels but do not appear to be strongly associated with adverse phenotypes in humans.
- Large-scale human genetic data and phenotyping are valuable for validating drug targets, including LRRK2 for Parkinson's disease.
- This study provides crucial human in vivo data on the consequences of LRRK2 inactivation, informing therapeutic strategies and safety assessments.
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