Langston, J. William

Objective The aim of this study was to search for genes/variants that modify the effect of LRRK2 mutations in terms of penetrance and age‐at‐onset of Parkinson's disease. Methods We performed the first genomewide association study of penetrance and age‐at‐onset of Parkinson's disease in LRRK2 mutation carriers (776 cases and 1,103 non‐cases at their last evaluation). Cox proportional hazard models and linear mixed models were used to identify modifiers of penetrance and age‐at‐onset of LRRK2 mutations, respectively. We also investigated whether a polygenic risk score derived from a published genomewide association study of Parkinson's disease was able to explain variability in penetrance and age‐at‐onset in LRRK2 mutation carriers. Results A variant located in the intronic region of CORO1C on chromosome 12 (rs77395454; p value = 2.5E‐08, beta = 1.27, SE = 0.23, risk allele: C) met genomewide significance for the penetrance model. Co‐immunoprecipitation analyses of LRRK2 and CORO1C supported an interaction between these 2 proteins. A region on chromosome 3, within a previously reported linkage peak for Parkinson's disease susceptibility, showed suggestive associations in both models (penetrance top variant: p value = 1.1E‐07; age‐at‐onset top variant: p value = 9.3E‐07). A polygenic risk score derived from publicly available Parkinson's disease summary statistics was a significant predictor of penetrance, but not of age‐at‐onset. Interpretation This study suggests that variants within or near CORO1C may modify the penetrance of LRRK2 mutations. In addition, common Parkinson's disease associated variants collectively increase the penetrance of LRRK2 mutations. ANN NEUROL 2021;90:82–94

Background: Mutations in the leucine rich repeat kinase 2 ( LRRK2) gene are among the most common genetic causes of Lewy body Parkinson’s disease (PD). However, LRRK2 mutations can also lead to a variety of pathological phenotypes other than typical PD, including relatively pure nigrostriatal cell loss without alpha-synuclein-positive Lewy bodies or Lewy neurites, progressive supranuclear palsy (PSP), and multiple system atrophy (MSA). The mechanisms behind this remarkable pleomorphic pathology are currently unclear. Objective: To genetically and pathologically characterize a case with a LRRK2, p.Ile1371Val rare variant and pathologically proven MSA. Methods: From the brain donation program at the Parkinson’s Institute and Clinical Center, we selected 26 brains with family history and a with clinicopathological diagnosis of PD ( n = 20), MSA ( n = 4), or PSP ( n = 2). We performed neuropathological evaluation, including alpha-synuclein and tau immunohistochemistry and sequenced 188 genes that have been reported as causative for or associated with neurodegenerative diseases. Results: We identified a known LRRK2, p.Ile1371Val genetic variant in a case with clinically diagnosed and pathologically proven MSA. Neuropathology revealed that the olivopontocerebellar system was more affected than the striatonigral system. Conclusions: Our data suggest that genetic variants in the LRRK2 gene can present clinically and neuropathologically as MSA. One other LRRK2 genetic variant ( LRRK2, p.Ile2020Thr) has been reported with a neuropathological diagnosis of MSA. Interestingly, the LRRK2 variant ( LRRK2, p.Ile1371Val) identified here has been reported previously in a postmortem case with Lewy body PD. Future studies are critical to discover the mechanisms leading to different neurodegenerative trajectories both in neuronal and glial cell populations.

Abstract Background Parkinson’s disease (PD) is the second most common neurodegenerative disorder. People with PD, their families, scientists, health care providers, and the general public are increasingly interested in identifying environmental contributors to PD risk. Methods In June 2007, a multidisciplinary group of experts gathered in Sunnyvale, California, USA, to assess what is known about the contribution of environmental factors to PD. Results We describe the conclusions around which they came to consensus with respect to environmental contributors to PD risk. We conclude with a brief summary of research needs. Conclusions PD is a complex disorder, and multiple different pathogenic pathways and mechanisms can ultimately lead to PD. Within the individual there are many determinants of PD risk, and within populations, the causes of PD are heterogeneous. Although rare recognized genetic mutations are sufficient to cause PD, these account for < 10% of PD in the U.S. population, and incomplete penetrance suggests that environmental factors may be involved. Indeed, interplay among environmental factors and genetic makeup likely influences the risk of developing PD. There is a need for further understanding of how risk factors interact, and studying PD is likely to increase understanding of other neurodegenerative disorders.