Lee, Virginia M.‐Y.

Importance Advances in Alzheimer disease (AD) have shifted research focus to earlier disease stages, necessitating more scalable approaches to identify cognitively unimpaired individuals with amyloid β (Aβ) pathology. Objective To assess the utility of plasma phosphorylated tau 217 (p-tau217) for classifying Aβ status in cognitively unimpaired individuals, both as a stand-alone test and in a 2-step approach where positive plasma results were confirmed using a second modality (Aβ positron emission tomography [PET] or cerebrospinal fluid [CSF]). Design, Setting, and Participants This cross-sectional cohort study used data collected between June 2009 and March 2024. We included 2916 cognitively unimpaired participants from 12 international independent observational cohorts in the US, Europe, Australia, and Canada with available plasma p-tau217 levels and CSF or PET Aβ biomarkers. Performance comparisons between mass spectrometry and immunoassay-based p-tau217 measurements were also performed (n = 964). Exposures Plasma p-tau217 levels measured by immunoassay. Main Outcome and Measures Aβ status, determined by CSF or Aβ PET biomarkers. Results Participants had a mean (SD) age of 66.9 (9.9) years; 971 (33.3%) were Aβ positive by either CSF or PET, 1667 (57.2%) were women, and 1108 (38.1%) carried at least 1 APOE ε4 allele. As a stand-alone test, plasma p-tau217 achieved a positive predictive value (PPV) of 79% (95% CI, 74-84) and an overall accuracy of 81% (95% CI, 80-82). In a 2-step workflow, the PPV and accuracy significantly increased to 91% (95% CI, 86-95). While this approach required screening of 677 individuals with plasma p-tau217 to identify 100 Aβ-positive individuals, compared to 536 participants when using PET alone, it reduced the need for PET testing to 124. Immunoassays demonstrated comparable PPVs to mass spectrometry (80% [95% CI, 74-86] vs 85% [95% CI, 81-90]; P = .12) but significantly lower overall accuracy (82% [95% CI, 79-84]% vs 88 [95% CI, 86-90]; P < .001) and true Aβ-positive detection rate (49% [95% CI, 43-55] vs 69% [95% CI, 64-75]; P < .001). Conclusions and Relevance The findings highlight the potential of plasma p-tau217 as a stand-alone test—or when used in a sequential 2-step approach alongside PET or CSF testing—as a cost-effective, scalable, and minimally burdensome strategy for identifying preclinical AD. Tailored screening workflows that incorporate p-tau217 can improve efficiency in participant selection for preclinical AD trials and, in the future, help guide access to disease-modifying treatments.

Abstract To elucidate the molecular basis of multiple system atrophy (MSA), a neurodegenerative disease, we conducted a genome-wide association study (GWAS) in a Japanese MSA case/control series followed by replication studies in Japanese, Korean, Chinese, European, and North American samples. In the GWAS stage, rs2303744 on chromosome 19 showed a suggestive association (P = 6.5 × 10− 7) that was replicated in additional Japanese samples (P = 2.9 × 10− 6, odds ratio (OR) = 1.58; 95% confidence interval (CI), 1.30–1.91), and then confirmed as highly significant in a meta-analysis of East Asian population data (P = 5.0 × 10− 15, OR = 1.49; 95% CI 1.35–1.65). The association of rs2303744 with MSA remained significant in combined European/North American samples (P = 0.017, OR = 1.12; 95% CI 1.02–1.23) despite allele frequencies being quite different between these populations. rs2303744 leads to an amino acid substitution in PLA2G4C that encodes the cPLA2γ lysophospholipase/transacylase. The cPLA2γ-Ile143 isoform encoded by the MSA risk allele has significantly decreased transacylase activity compared with the alternate cPLA2γ-Val143 isoform, and may perturb membrane phospholipids and promote oligodendroglial pathology.

R47H- TREM2 mutation enhances AKT signaling in human AD microglia and mediates proinflammatory and synaptic toxicity in a tauopathy mouse model.

ABSTRACTBackgroundWe have reported that intermediate repeat lengths of the C9ORF72 repeat are a risk factor for Parkinson's disease (PD) in a clinically diagnosed data set. Because 10% to 25% of clinically diagnosed PD have different diagnoses upon autopsy, we hypothesized that this may reflect phenotypic heterogeneity or concomitant pathology of other neurodegenerative disorders.MethodsWe screened 488 autopsy‐confirmed PD cases for expansion haplotype tag rs3849942T. In 196 identified haplotype carriers, the C9ORF72 repeat was genotyped using the repeat‐primed polymerase chain reaction assay.ResultsNo larger (intermediate or expanded) repeats were found in these autopsy‐confirmed PD samples. This absence of larger repeats is significantly different from the frequency in clinically diagnosed datasets (P = 0.002).ConclusionsOur results suggest that expanded or intermediate C9ORF72 repeats in clinically diagnosed PD or parkinsonism might be an indication of heterogeneity in clinically diagnosed PD cases. Further studies are needed to elucidate the potential contribution of the C9ORF72 repeat to autopsy‐confirmed PD. © 2014 International Parkinson and Movement Disorder Society