Phenotypic Heterogeneity among GBA p.R202X Carriers in Lewy Body Spectrum Disorders

We describe the clinical and neuropathologic features of patients with Lewy body spectrum disorder (LBSD) carrying a nonsense variant, c.604C>T; p.R202X, in the glucocerebrosidase 1 (GBA) gene. While this GBA variant is causative for Gaucher’s disease, the pathogenic role of this mutation in LBSD is unclear. Detailed neuropathologic evaluation was performed for one index case and a structured literature review of other GBA p.R202X carriers was conducted. Through the systematic literature search, we identified three additional reported subjects carrying the same GBA mutation, including one Parkinson’s disease (PD) patient with early disease onset, one case with neuropathologically-verified LBSD, and one unaffected relative of a Gaucher’s disease patient. Among the affected subjects carrying the GBA p.R202X, all males were diagnosed with Lewy body dementia, while the two females presented as PD. The clinical penetrance of GBA p.R202X in LBSD patients and families argues strongly for a pathogenic role for this variant, although presenting with a striking phenotypic heterogeneity of clinical and pathological features.

Brain atrophy in prodromal synucleinopathy is shaped by structural connectivity and gene expression

Isolated REM sleep behaviour disorder (iRBD) is a synucleinopathy characterized by abnormal behaviours and vocalizations during REM sleep. Most iRBD patients develop dementia with Lewy bodies, Parkinson's disease, or multiple system atrophy over time. Patients with iRBD exhibit brain atrophy patterns that are reminiscent of those observed in overt synucleinopathies. However, the mechanisms linking brain atrophy to the underlying alpha-synuclein pathophysiology are poorly understood. Our objective was to investigate how the prion-like and regional vulnerability hypotheses of alpha-synuclein might explain brain atrophy in iRBD. Using a multicentric cohort of 182 polysomnography-confirmed iRBD patients who underwent T1-weighted MRI, we performed vertex-based cortical surface and deformation-based morphometry analyses to quantify brain atrophy in patients (67.8 years, 84% men) and 261 healthy controls (66.2 years, 75%) and investigated the morphological correlates of motor and cognitive functioning in iRBD. Next, we applied the agent-based Susceptible-Infected-Removed model (i.e., a computational model that simulates in silico the spread of pathologic alpha-synuclein based on structural connectivity and gene expression) and tested if it recreated atrophy in iRBD by statistically comparing simulated regional brain atrophy to the atrophy observed in patients. The impact of SNCA and GBA gene expression and brain connectivity was then evaluated by comparing the model fit to the one obtained in null models where either gene expression or connectivity was randomized. The results showed that iRBD patients present with cortical thinning and tissue deformation, which correlated with motor and cognitive functioning. Next, we found that the atrophy simulated based on brain connectivity and gene expression recreated cortical thinning (r=0.51, p=0.0007) and tissue deformation (r=0.52, p=0.0005) in patients, and that the connectome's architecture along with SNCA and GBA gene expression contributed to shaping atrophy in iRBD. We further demonstrated that the full agent-based model performed better than network measures or gene expression alone in recreating the atrophy pattern in iRBD. In summary, atrophy in iRBD is extensive, correlates with motor and cognitive functioning, and can be recreated using the dynamics of agent-based modelling, structural connectivity, and gene expression. These findings support the concepts that both prion-like spread and regional susceptibility account for the atrophy observed in prodromal synucleinopathies. Therefore, the agent-based Susceptible-Infected-Removed model may be a useful tool for testing hypotheses underlying neurodegenerative diseases and new therapies aimed at slowing or stopping the spread of alpha-synuclein pathology.

Transcriptome deregulation of peripheral monocytes in GBA-related Parkinson's disease

Background: Genetic mutations in the beta-glucocerebrosidase (GCase), GBA gene, represent the major genetic risk factor for Parkinson's disease (PD). The function of the GBA gene is at the crossroads between the endo-lysosomal pathway and the immune response, two important mechanisms involved in the pathogenesis of PD. However, modifiers of GBA penetrance have not yet been fully elucidated. Methods: we characterized the transcriptomic profiles of circulating monocytes and whole blood in a population of patients with PD and healthy controls (CTRL) with (PD/GBA and CTRL/GBA) and without GBA variants (iPD and CTRL) (monocytes: n = 56 iPD, 66 CTRL, 23 PD/GBA, 13 CTRL/GBA; whole blood: n = 616 iPD, 362 CTRLs, 127 PD/GBA, 165 CTRL/GBA). Differential expression analysis, pathways enrichment analysis, and outliers detections were performed. Ultrastructural characterization of isolated CD14+ monocytes in the four groups was also performed through electron microscopy. Results: We observed hundreds of differentially expressed genes and dysregulated pathways when comparing manifesting and non-manifesting GBA mutation carriers. Specifically, when compared to idiopathic PD, GBA-PD showed dysregulation in genes involved in alpha-synuclein degradation, aging and amyloid processing (i.e. SNCA, LMNA). Gene-based outlier analysis confirmed the involvement of lysosomal, membrane trafficking, and mitochondrial processing in manifesting compared to nonmanifesting GBA-carriers, as also observed at the ultrastructural levels. Conclusions: Overall, our transcriptomic analysis of primary monocytes identified gene targets and biological processes that can help in understanding the pathogenic mechanisms associated with GBA mutations in the context of PD.

Comparative Transcriptome Analysis in Monocyte-Derived Macrophages of Asymptomatic GBA Mutation Carriers and Patients with GBA-Associated Parkinson’s Disease

Mutations of the GBA gene, encoding for lysosomal enzyme glucocerebrosidase (GCase), are the greatest genetic risk factor for Parkinson’s disease (PD) with frequency between 5% and 20% across the world. N370S and L444P are the two most common mutations in the GBA gene. PD carriers of severe mutation L444P in the GBA gene is characterized by the earlier age at onset compared to N370S. Not every carrier of GBA mutations develop PD during one’s lifetime. In the current study we aimed to find common gene expression signatures in PD associated with mutation in the GBA gene (GBA-PD) using RNA-seq. We compared transcriptome of monocyte-derived macrophages of 5 patients with GBA-PD (4 L444P/N, 1 N370S/N) and 4 asymptomatic GBA mutation carriers (GBA-carriers) (3 L444P/N, 1 N370S/N) and 4 controls. We also conducted comparative transcriptome analysis for L444P/N only GBA-PD patients and GBA-carriers. Revealed deregulated genes in GBA-PD independently of GBA mutations (L444P or N370S) were involved in immune response, neuronal function. We found upregulated pathway associated with zinc metabolism in L444P/N GBA-PD patients. The potential important role of DUSP1 in the pathogenesis of GBA-PD was suggested.

Analysis of mutations associated with Parkinson’s disease in patients of the Krasnoyarsk region

Background. Parkinson’s disease (PD) is one of the common neurodegenerative diseases. Several genes are known (SNCA, PARK2, PINK1, PARK7 (DJ-1) and LRRK2), mutations in which have a pathological significance in the development of monogenic PD; association with PD of other genes (for example, UCHL1, ATP13A2) requires further study. It is also known, that GBA gene is associated with an increased risk of PD developing.Aim. Analysis of mutations and polymorphisms in the PARK2, PINK1, SNCA, ATP13A2, PARK7, LRRK2, UCHL, GCH1 and GBA genes in patients with PD from Krasnoyarsk region.Material and methods. The 60 patients with sporadic and familial forms of PD were included in the study. The SALSA MLPA Holland P051 and P052 kits («MRC Amsterdam», The Netherlands) were used to detect deletions and duplications in the PARK2, PINK1, SNCA, ATP13A2, PARK7, LRRK2, UCHL, GCH1 genes, as well as point mutations A30P in the SNCA gene and G2019S in the LRRK2 gene. Analysis of the GBA gene was carried out by Senger sequencing.Results. None of the 60 patients had mutations that were searched with the SALSA MLPA Holland P051 and P052 kits. 6 different mutations in the GBA gene were found in 9 out of 60 patients with PD. L444P («severe» PD — associated mutation) — in two patients, D409H («severe» PD — associated mutation) — in one patient, T369M (polymorphism, possibly associated with PD) — in two patients, E326K (polymorphism, possibly associated with PD) — in one patient, V460V (synonymous variant, which is part of the composition of the complex RecNcil mutation (p.L444P; p.A456P; p.V460V) associated with PD) — in two patients and variant C.*92g>A (3’ — UTR polymorphism, possibly associated with PD) — in one patient. Two patients had compound heterozygous carriers of two variants.Conclusion. This paper presents the genetic analysis results of the PD associated genes among patients from the Krasnoyarsk region. No mutations were detected in the PARK2, PINK1, SNCA, ATP13A2, PARK7, LRRK2, UCHL and GCH1 genes. Genetic variants analysis of the GBA gene showed similar frequency in the patients from the Krasnoyarsk region as in European populations.