Biological definitions of neuronal α-synuclein disease are advancing diagnosis beyond traditional clinical syndromes, but the trajectories preceding dementia and the influence of concomitant Alzheimer’s disease neuropathologic change (ADNC) remain uncertain. We analyzed longitudinal data from 1,543 participants without dementia at baseline who underwent repeated cognitive, functional, neuropsychiatric, and motor assessments and had neuropathological characterization at autopsy. Participants were classified as having neuronal α-synuclein neuropathologic change (NSNC), ADNC, or both. NSNC without intermediate or high ADNC was associated with the greatest motor burden. Among participants without mild cognitive impairment at baseline, concomitant ADNC was associated with earlier cognitive impairment and faster cognitive decline; mixed NSNC/ADNC also showed faster functional worsening than NSNC alone. Across participants with NSNC, baseline mild cognitive impairment, neuropsychiatric manifestations and concomitant ADNC predicted progression to dementia, whereas prespecified motor signs did not. These findings reveal heterogeneous pre-dementia trajectories and support combining α-synuclein detection with Alzheimer biomarkers, cognitive staging and multidomain clinical measures to improve prognosis and trial design.
I. Illán-Gala, E. Vera, J. Selma-González et al.· Research Square· 0 citations
Copy-number variants (CNVs) are major contributors to human disease. In Alzheimer disease (AD), APP duplications cause autosomal-dominant forms, but the role of CNVs in non-monogenic AD remains poorly characterized. We analyzed rare CNVs (frequency <1%) from 22,319 exomes (4,150 early-onset AD [EOAD, ≤65 years], 8,519 late-onset AD [LOAD], 9,650 unaffected control subjects) using harmonized calling and quality control. After identifying 17 individuals with a pathogenic CNV, we performed exome-wide and gene-set burden analyses. EOAD-affected individuals showed increased burdens of rare CNVs affecting coding genes, particularly deletions in AD-related genes. Integrated loss-of-function (LoF) analysis gathering short truncating variants with deletions showed that ABCA1 (odds ratio [OR] = 5.77 [95% confidence interval 2.25; 17.06], p = 0.0002) and ABCA7 deletions contribute to this deletion burden (OR = 2.29 [1.44; 3.65], p = 0.0006), while CTSB LoF alleles appear as candidates (OR = 5.03 [1.50; 20.71], p = 0.0089). We then performed exome-wide gene-level dosage analysis and highlighted 18 genes across five loci with a false discovery rate of <10%, including the 22q11.21 central region, where deletions were restricted to EOAD (including one de novo event) and duplications were enriched in control individuals, with intermediate frequencies in LOAD. We narrowed this locus to the SCARF2-KLHL22-MED15 region after integrating short truncating variants. Replication in 33,977 affected individuals and 362,322 control subjects confirmed association for 22q11.21 dosage with exome-wide significance (ORSCARF2 = 0.34 [0.21; 0.53]; mega-p value = 5.52 × 10-7). SCARF2 overexpression significantly increased amyloid-β uptake, congruent with duplication-associated decreased AD risk. We conclude that rare coding CNVs in a proportion of AD-associated genes and 22q11.21 deletions, including some found in DiGeorge syndrome, increase AD risk. Conversely, we identify 22q11.21 duplication as a strong AD-risk-decreasing factor.
O. Quenez, Catherine Schramm, K. Cassinari et al.· American Journal of Human Ge...· 1 citation
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