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Background Alpha‐synuclein (α‐syn), phosphorylated at serine 129 (pS129‐α‐syn), is a potential biomarker for Parkinson's disease (PD) because it is the predominant α‐syn species found in Lewy bodies. Methods We developed an in‐house SIMOA assay, using commercially available components, to quantify pS129‐α‐syn in CSF. The clinical utility of the assay was tested in CSF from 120 patients with PD from the Norwegian ParkWest longitudinal study and 29 normal controls. Prior measurements of CSF total (t)‐α‐syn and the pS129‐α‐syn/t‐α‐syn ratio were included for comparison. Results The lower limit of quantification of the in‐house assay used to analyze CSF samples from participants was 0.57 pg/mL, which was well below the observed concentrations of endogenous pS129‐α‐syn in CSF. Median CSF pS129‐α‐syn levels were slightly lower in PD patients compared to controls (5.7 pg/mL vs. 6.5 pg/mL), but the difference was not significant in the unadjusted (p = 0.404) or adjusted analyses (p = 0.270). There was no difference in the pS129‐α‐syn/t‐α‐syn ratio between patients and controls. Using linear mixed‐effects models, we found no association between baseline pS129‐α‐syn or the pS129‐α‐syn/t‐α‐syn ratio and motor or cognitive decline over a 10‐year period. Conclusion We developed and applied an in‐house SIMOA that reliably quantifies pS129‐α‐syn in CSF samples. This study does not indicate a role for CSF pS129‐α‐syn or the pS129‐α‐syn/t‐α‐syn ratio as clinically useful diagnostic or prognostic biomarkers in PD.

The PARK16 locus, spanning five genes on chromosome 1, was among the first genetic regions to show genome-wide association in Parkinson's disease (PD). Subsequent investigations have found variability in PARK16 top-hits and association patterns across populations, and the implicated genes and mechanisms are currently unclear. In the present study, we aimed to explore the contribution of PARK16 variability to PD risk in a Scandinavian population. We genotyped 17 single-nucleotide polymorphisms in a case-control sample set of 2570 individuals from Norway and Sweden to fine map the locus. Targeted resequencing of the full coding regions of SLC45A3, NUCKS1, RAB7L1, SLC41A1 and PM20D1 was performed in DNA pools from a subset of 387 patient samples. We find evidence for an association with PD for rs1775143 as well as a haplotype located around the 5' region of RAB7L1, implicating variants which are not in high linkage disequilibrium with the strongest signal from a recent large meta-analysis in Caucasians. We also provide suggestive support for epistasis between RAB7L1 and LRRK2 as previously hypothesized by others. Comparing our results with previous work, allelic heterogeneity at PARK16 appears likely, and further studies are warranted to disentangle the complex patterns of association and pinpoint the functionally relevant variants.

Objective Dementia with Lewy bodies (DLB) and Parkinson's disease (PD) share clinical, pathological, and genetic risk factors, including GBA1 and APOEε4 mutations. Biomarkers associated with the pathways of these mutations, such as glucocerebrosidase enzyme (GCase) activity and amyloid‐beta 42 (Aβ42) levels, may hold potential as predictive indicators, providing valuable insights into the likelihood of cognitive decline within these diagnoses. Our objective was to determine their association with cognitive decline in DLB and PD. Methods A total of 121 DLB patients from the European‐DLB Consortium and 117 PD patients from the Norwegian ParkWest Study were included in this study. The four most commonly associated variants of GBA1 mutations (E326K, T369M, N370S, L444P), APOEε4 status, and cerebrospinal fluid (CSF) Aβ42 levels and GCase activity were assessed, as well as global cognition using the Mini‐Mental State Examination. Linear mixed‐effects regression models were used to evaluate the association of CSF biomarkers with cognitive decline in each diagnostic group, adjusted for age, sex, education, and genetic mutation profile. Results Low CSF Aβ42 levels were associated with accelerated cognitive decline in DLB, whereas reduced CSF GCase activity predicted faster cognitive decline in PD. These associations were independent of GBA1 gene mutations or APOEε4 status. Interpretation Our study provides important evidence on the relationship between brain Aβ deposition and GCase activity in the Lewy body disease spectrum independent of their genetic mutation profile. This information could be relevant for designing future clinical trials targeting these pathways.

Although the 14-item Starkstein Apathy Scale (SAS) is recommended to screen for and measure the severity of apathetic symptoms in Parkinson disease (PD), the psychometric attributes of this scale have not yet been fully evaluated. The authors examined the reliability, factor structure, and discriminant validity of the SAS in 194 nondemented patients with early untreated PD. Cross-sectional multicenter population-based study from Western and Southern Norway. Standardized rating scales for parkinsonism and neuropsychiatric symptoms. The SAS showed fair internal consistency (Cronbach's α = 0.69) and exploratory factor analysis identified two factors: the first factor (24.2% of the variance) represented cognitive-behavioral aspects of apathy (items 1, 2, and 4–8; Cronbach's α = 0.74) and the second factor (15.0% of the variance) a general apathy dimension (items 3 and 9–14; Cronbach's α = 0.52). The correlation between these two factors was low (Spearman's r = 0.19, N = 194, p = 0.008), indicating clinically distinct dimensions, but both factor scores were strongly related to the total SAS score (Spearman's r > 0.6, N = 194, p < 0.0005). Item 3 (insight or self-reflection) showed a negative item-total correlation, and removing this item raised the Cronbach's α of the second factor to 0.70, but did not substantially alter the other results. Both the total score and factor scores of SAS showed fair discriminant validity. Although the SAS showed fairly good psychometric properties and the exploratory factor analysis suggested a two-factor solution, the results with this PD sample indicate that item 3 is ambiguous and should be considered removed from the scale.

Introduction: In patients with Parkinson’s disease (PD), low cerebrospinal fluid (CSF) amyloid beta 1-42 (Ab42) at baseline is the most consistent CSF biomarker as a risk factor for developing dementia. Low CSF Ab42 is, however, a typical hallmark of Alzheimer’s disease (AD). Hence, low CSF Ab42 in patients with PD may indicate presence of comorbid AD pathology and may predict a more AD-like cognitive profile when they develop dementia. Our study aimed to investigate if low CSF Ab42 at baseline is associated with a more AD-like cognitive profile in PD patients with dementia. Methods: In a prospectively followed-up, population-based cohort of newly diagnosed PD patients, we compared the cognitive profile of dementia in those with a low CSF Ab42 level at baseline with that of patients who had normal levels at the time when they developed dementia. Four different cognitive domain z-scores (memory, attention, executive, visuospatial) were calculated. Patients were subdivided into three tertiles or categorized dichotomously based on the baseline CSF Ab42 levels as measured by electrochemiluminescence and ELISA. Results: During 10-year follow-up, 37 patients met the inclusion criteria. Memory domain composite z-scores, memory subtest z-scores, and the difference between long-delay free recall versus recognition scores were not significantly different between the groups. Composite z-scores of visuospatial functions significantly differed between the tertiles, which was not significant after Bonferroni correction. In the dichotomous group analysis, z-scores of visuospatial functions significantly differed between the two groups. The other cognitive domain z-scores were not significantly different. Conclusions: In patients with PD dementia, low CSF Ab42 level at baseline is not associated with a specific cognitive profile.

Background This update of the guideline on the management of amyotrophic lateral sclerosis (ALS) was commissioned by the European Academy of Neurology (EAN) and prepared in collaboration with the European Reference Network for Neuromuscular Diseases (ERN EURO‐NMD) and the support of the European Network for the Cure ALS (ENCALS) and the European Organization for Professionals and Patients with ALS (EUpALS). Methods Grading of Recommendations Assessment, Development, and Evaluation (GRADE) methodology was used to assess the effectiveness of interventions for ALS. Two systematic reviewers from Cochrane Response supported the guideline panel. The working group identified a total of 26 research questions, performed systematic reviews, assessed the quality of the available evidence, and made specific recommendations. Expert consensus statements were provided where insufficient evidence was available. Results A guideline mapping effort revealed only one other ALS guideline that used GRADE methodology (a National Institute for Health and Care Excellence [NICE] guideline). The available evidence was scarce for many research questions. Of the 26 research questions evaluated, the NICE recommendations could be adapted for 8 questions. Other recommendations required updates of existing systematic reviews or de novo reviews. Recommendations were made on currently available disease‐modifying treatments, multidisciplinary care, nutritional and respiratory support, communication aids, psychological support, treatments for common ALS symptoms (e.g., muscle cramps, spasticity, pseudobulbar affect, thick mucus, sialorrhea, pain), and end‐of‐life management. Conclusions This update of the guideline using GRADE methodology provides a framework for the management of ALS. The treatment landscape is changing rapidly, and further updates will be prepared when additional evidence becomes available.

Increased somatic mitochondrial DNA (mtDNA) mutagenesis causes premature aging in mice, and mtDNA damage accumulates in the human brain with aging and neurodegenerative disorders such as Parkinson disease (PD). Here, we study the complete spectrum of mtDNA changes, including deletions, copy-number variation and point mutations, in single neurons from the dopaminergic substantia nigra and other brain areas of individuals with Parkinson disease and neurologically healthy controls. We show that in dopaminergic substantia nigra neurons of healthy individuals, mtDNA copy number increases with age, maintaining the pool of wild-type mtDNA population in spite of accumulating deletions. This upregulation fails to occur in individuals with Parkinson disease, however, resulting in depletion of the wild-type mtDNA population. By contrast, neuronal mtDNA point mutational load is not increased in Parkinson disease. Our findings suggest that dysregulation of mtDNA homeostasis is a key process in the pathogenesis of neuronal loss in Parkinson disease. Accumulated damage to mitochondrial DNA (mtDNA) occurs during the ageing process and neurodegenerative disease. Here, the authors show that mtDNA copy number increases in an age-dependent manner in substantia nigra of healthy individuals, but not in individuals with Parkinson disease.

A key driver of patients’ well-being and clinical trials for Parkinson’s disease (PD) is the course that the disease takes over time (progression and prognosis). To assess how genetic variation influences the progression of PD over time to dementia, a major determinant for quality of life, we performed a longitudinal genome-wide survival study of 11.2 million variants in 3,821 patients with PD over 31,053 visits. We discover RIMS2 as a progression locus and confirm this in a replicate population (hazard ratio (HR) = 4.77, P  = 2.78 × 10 −11 ), identify suggestive evidence for TMEM108 (HR = 2.86, P  = 2.09 × 10 −8 ) and WWOX (HR = 2.12, P  = 2.37 × 10 −8 ) as progression loci, and confirm associations for GBA (HR = 1.93, P  = 0.0002) and APOE (HR = 1.48, P  = 0.001). Polygenic progression scores exhibit a substantial aggregate association with dementia risk, while polygenic susceptibility scores are not predictive. This study identifies a novel synaptic locus and polygenic score for cognitive disease progression in PD and proposes diverging genetic architectures of progression and susceptibility. A genome-wide survival study identifies variants at RIMS2 associated with progression of Parkinson’s disease to dementia and highlights divergence in the genetic architecture of disease onset and progression.

Background Parkinson’s disease (PD) is a complex, age-related neurodegenerative disorder of largely unknown etiology. PD is strongly associated with mitochondrial respiratory dysfunction, which can lead to epigenetic dysregulation and specifically altered histone acetylation. Nevertheless, and despite the emerging role of epigenetics in age-related brain disorders, the question of whether aberrant histone acetylation is involved in PD remains unresolved. Methods We studied fresh-frozen brain tissue from two independent cohorts of individuals with idiopathic PD ( n  = 28) and neurologically healthy controls ( n  = 21). We performed comprehensive immunoblotting to identify histone sites with altered acetylation levels in PD, followed by chromatin immunoprecipitation sequencing (ChIP-seq). RNA sequencing data from the same individuals was used to assess the impact of altered histone acetylation on gene expression. Results Immunoblotting analyses revealed increased acetylation at several histone sites in PD, with the most prominent change observed for H3K27, a marker of active promoters and enhancers. ChIP-seq analysis further indicated that H3K27 hyperacetylation in the PD brain is a genome-wide phenomenon with a strong predilection for genes implicated in the disease, including SNCA , PARK7 , PRKN and MAPT . Integration of the ChIP-seq with transcriptomic data from the same individuals revealed that the correlation between promoter H3K27 acetylation and gene expression is attenuated in PD patients, suggesting that H3K27 acetylation may be decoupled from transcription in the PD brain. Strikingly, this decoupling was most pronounced among nuclear-encoded mitochondrial genes, corroborating the notion that impaired crosstalk between the nucleus and mitochondria is involved in the pathogenesis of PD. Our findings independently replicated in the two cohorts. Conclusions Our findings strongly suggest that aberrant histone acetylation and altered transcriptional regulation are involved in the pathophysiology of PD. We demonstrate that PD-associated genes are particularly prone to epigenetic dysregulation and identify novel epigenetic signatures associated with the disease.

Mitochondrial complex I deficiency occurs in the substantia nigra of individuals with Parkinson’s disease. It is generally believed that this phenomenon is caused by accumulating mitochondrial DNA damage in neurons and that it contributes to the process of neurodegeneration. We hypothesized that if these theories are correct, complex I deficiency should extend beyond the substantia nigra to other affected brain regions in Parkinson’s disease and correlate tightly with neuronal mitochondrial DNA damage. To test our hypothesis, we employed a combination of semiquantitative immunohistochemical analyses, Western blot and activity measurements, to assess complex I quantity and function in multiple brain regions from an extensively characterized population-based cohort of idiopathic Parkinson’s disease (n = 18) and gender and age matched healthy controls (n = 11). Mitochondrial DNA was assessed in single neurons from the same areas by real-time PCR. Immunohistochemistry showed that neuronal complex I deficiency occurs throughout the Parkinson’s disease brain, including areas spared by the neurodegenerative process such as the cerebellum. Activity measurements in brain homogenate confirmed a moderate decrease of complex I function, whereas Western blot was less sensitive, detecting only a mild reduction, which did not reach statistical significance at the group level. With the exception of the substantia nigra, neuronal complex I loss showed no correlation with the load of somatic mitochondrial DNA damage. Interestingly, α-synuclein aggregation was less common in complex I deficient neurons in the substantia nigra. We show that neuronal complex I deficiency is a widespread phenomenon in the Parkinson’s disease brain which, contrary to mainstream theory, does not follow the anatomical distribution of neurodegeneration and is not associated with the neuronal load of mitochondrial DNA mutation. Our findings suggest that complex I deficiency in Parkinson’s disease can occur independently of mitochondrial DNA damage and may not have a pathogenic role in the neurodegenerative process.