Association between CSF alpha-synuclein seeding activity and genetic status in Parkinson’s disease and dementia with Lewy bodies

Abstract

The clinicopathological heterogeneity in Lewy-body diseases (LBD) highlights the need for pathology-driven biomarkers in-vivo. Misfolded alpha-synuclein (α-Syn) is a lead candidate based on its crucial role in disease pathophysiology. Real-time quaking-induced conversion (RT-QuIC) analysis of CSF has recently shown high sensitivity and specificity for the detection of misfolded α-Syn in patients with Parkinson's disease (PD) and dementia with Lewy bodies (DLB). In this study we performed the CSF RT-QuIC assay in 236 PD and 49 DLB patients enriched for different genetic forms with mutations in GBA, parkin, PINK1, DJ1, and LRRK2. A subgroup of 100 PD patients was also analysed longitudinally. We correlated kinetic seeding parameters of RT-QuIC with genetic status and CSF protein levels of molecular pathways linked to α-Syn proteostasis. Overall, 85% of PD and 86% of DLB patients showed positive RT-QuIC α-Syn seeding activity. Seeding profiles were significantly associated with mutation status across the spectrum of genetic LBD. In PD patients, we detected positive α-Syn seeding in 93% of patients carrying severe GBA mutations, in 78% with LRRK2 mutations, in 59% carrying heterozygous mutations in recessive genes, and in none of those with bi-allelic mutations in recessive genes. Among PD patients, those with severe GBA mutations showed the highest seeding activity based on RT-QuIC kinetic parameters and the highest proportion of samples with 4 out of 4 positive replicates. In DLB patients, 100% with GBA mutations showed positive α-Syn seeding compared to 79% of wildtype DLB. Moreover, we found an association between α-Syn seeding activity and reduced CSF levels of proteins linked to α-Syn proteostasis, specifically lysosome-associated membrane glycoprotein 2 and neurosecretory protein VGF.These findings highlight the value of α-Syn seeding activity as an in-vivo marker of Lewy-body pathology and support its use for patient stratification in clinical trials targeting α-Syn.

Performance of Αsynuclein Rt-Quic in Relation to Neuropathological Staging of Lewy Body Disease

“…The diagnostic accuracy has predictably been somewhat lower in clinical cohorts with sensitivity > 93% and specificity > 82% [14,28,39,46,56]. Among aSyn RT-QuIC assays, there are those with particularly short overall assay times of ~1-2 days, without compromising diagnostic performance [16,28,46,51,[54][55][56]64].…”

Contribution of Autophagy-Lysosomal Pathway in the Exosomal Secretion of Alpha-Synuclein and Its Impact in the Progression of Parkinson’s Disease

“…Interestingly, CSF samples from patients harboring mutations in PINK1 or Parkin did not show positive α-syn seeding activity. However, CFS samples from LRRK2 PD patients (78%) showed an elevated α-syn positivity, only exceeded by CSF samples from DLB (100%) or PD (93%) patients carrying GBA1 mutations ( Brockmann et al, 2021 ). Notably, this higher α-syn seeding activity in CSF from GBA1 patients was associated with lower levels of proteins related to α-syn clearance, including autophagy, lysosomal function, and endocytosis pathways in the same samples, suggesting GBA1 mutations promote a negative correlation between α-syn accumulation and degradation pathways, mainly associated with lysosomal dysfunction ( Brockmann et al, 2021 ).…”

“…Mutations in LRRK2 have been shown to reduce mitochondria trafficking in rat neurons ( Godena et al, 2014 ; Hsieh et al, 2016 ), impair the mitophagy activity in PD-derived cells ( Bonello et al, 2019 ; Wauters et al, 2020 ), and increase aggregation of α-syn in mice models and human iPSC-derived dopaminergic neurons ( Bieri et al, 2019 ). In a recent work, researchers studied α-syn spreading levels in CSF from patients carrying different DLB and PD mutations using an α-syn real-time amplification assay ( Brockmann et al, 2021 ). Interestingly, CSF samples from patients harboring mutations in PINK1 or Parkin did not show positive α-syn seeding activity.…”

“…Notably, this higher α-syn seeding activity in CSF from GBA1 patients was associated with lower levels of proteins related to α-syn clearance, including autophagy, lysosomal function, and endocytosis pathways in the same samples, suggesting GBA1 mutations promote a negative correlation between α-syn accumulation and degradation pathways, mainly associated with lysosomal dysfunction ( Brockmann et al, 2021 ). This work also found decreased levels of proteins from the UPS and neurosecretion processes in CSF from GBA1 -carrying patients, which increase the urge to elucidate the mechanisms involved in this broad reduction in degradation pathways proteome ( Brockmann et al, 2021 ) and to check if this data is reflected in CNS samples.…”

Production of Recombinant Alpha-Synuclein: Still No Standardized Protocol in Sight

“…Some studies use home-made aSyn, others use protein from commercial vendors. While batch-to-batch variations in aSyn are recognized as a possible source of variation in the field [ 28 , 29 ], only a subset of studies reports systematic comparison of inter-batch variability [ 28 , 30 , 31 , 32 ]. In a recent study, SAAs were performed on control- and PD CSF by three independent groups in parallel according to their respective protocols [ 33 ].…”