Biology subjects

Foiani, M. S.

Publications and source records attributed to Foiani, M. S..

3 recordsLinked to original sources

bioRxiv2026

Spatial Single-Cell Proteomics Reveals Molecular Trajectories Of Tangle-Bearing Neurons In Alzheimer's Disease

Neurofibrillary tangles composed of hyperphosphorylated tau are a defining pathological hallmark of Alzheimers disease (AD); however, the pathways and mechanisms associated with the transition from physiological tau to tangle pathology remain unclear. Here, we integrate laser microdissection of post-mortem, fixed human AD brain tissue labelled with an antibody recognizing tangle-associated phospho-tau (AT8) with mass spectrometry-based proteomics, applied to individual neurons and to small neuronal pools. This approach identified [~]2,000 and [~]5,000 proteins, respectively, and enabled direct detection of disease-associated tau phosphorylation sites without prior enrichment. A layered analysis of the proteome of tangle-positive and tangle-negative neurons revealed heterogeneous disease-associated states. Pseudotime analysis, combined with an AI-driven analytical framework, indicates that neurons do not segregate into discrete classes but instead organize along a continuum of proteomic changes that correlate with tau abundance. This organization enabled the construction of a trajectory of pathological neuronal responses that can be resolved within an individual brain. Early stages of this trajectory are characterized by coordinated remodeling of proteostasis networks, including reduced proteasome component abundance and increased lysosomal acidification machinery, followed by disruption of synaptic pathways. Notably, despite extensive proteomic remodeling, neurons bearing tangles show little evidence of activated cell-death programs, suggesting prolonged molecular adaptation rather than acute degeneration. Together, these findings establish a framework for single-cell-resolved proteome analysis of human brain disease in situ and define a continuum of neuronal states underlying tau pathogenesis, revealing early vulnerabilities and adaptive responses during AD progression.

neuroscience↗

bioRxiv2026

Distinct mechanistic pathways of early tauopathy revealed by MAPT mutations

Tau pathology underlies a broad spectrum of neurodegenerative disorders, collectively termed tauopathies, yet these diseases exhibit striking heterogeneity in their biological mechanisms and clinical outcomes. The basis for this heterogeneity remains poorly understood. Here, we address this question using knock-in mouse models expressing two distinct frontotemporal dementia-associated tau mutations to define how different tau variants drive divergent pathogenic programs in vivo. We find that the two mutations give rise to fundamentally different trajectories of tau pathogenesis. One trajectory is marked by progressive tau hyperphosphorylation and cytoskeletal destabilization occurring in the absence of detectable tau seed formation. In contrast, an alternative trajectory is characterized by tau hypophosphorylation, early seed formation, and alterations in nucleotide metabolism and chromatin organization, without overt cytoskeletal disruption. With aging, tau in this latter pathway transitions to a hyperphosphorylated state and forms mature fibrillar aggregates. Genetic enhancement of {beta}-amyloid selectively accelerates fibril formation, particularly in the model exhibiting early seeding. Together, these findings demonstrate that distinct tau mutations can engage separable pathogenic mechanisms, providing a biological framework for the heterogeneity observed across tauopathies, and highlighting the need for mechanism-informed therapeutic strategies and patient stratification. O_FIG O_LINKSMALLFIG WIDTH=199 HEIGHT=200 SRC="FIGDIR/small/705716v1_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@11eb652org.highwire.dtl.DTLVardef@153cc53org.highwire.dtl.DTLVardef@8b670eorg.highwire.dtl.DTLVardef@1afaad_HPS_FORMAT_FIGEXP M_FIG C_FIG Graphical abstractSchematic representation comparing two trajectories of tau pathology. The S305N mutation promotes a 4R isoform shift, cytoskeletal damage and synapse loss, and accumulation of soluble hyperphosphorylated tau. Tau remains soluble even at old ages. In contrast, the P301S mutation generates hypophosphorylated, seed-competent tau that forms fibrils. The effect of amyloid is slow in the S305N, but results in accelerated acceleration of pathology in the P301S. Figure made with Biorender.com.

neuroscience↗

bioRxiv2023

Tau filaments are tethered within brain extracellular vesicles in Alzheimer's disease

The abnormal assembly of tau protein in neurons is the pathological hallmark of multiple neurodegenerative diseases, including Alzheimers disease (AD). In addition, assembled tau associates with extracellular vesicles (EVs) in the central nervous system of patients with AD, which is linked to its clearance and prion-like propagation between neurons. However, the identities of the assembled tau species and the EVs, as well as how they associate, are not known. Here, we combined quantitative mass spectrometry, cryo-electron tomography and single-particle cryo-electron microscopy to study brain EVs from AD patients. We found filaments of truncated tau enclosed within EVs enriched in endo-lysosomal proteins. We observed multiple filament interactions, including with molecules that tethered filaments to the EV limiting membrane, suggesting selective packaging. Our findings will guide studies into the molecular mechanisms of EV-mediated secretion of assembled tau and inform the targeting of EV-associated tau as potential therapeutic and biomarker strategies for AD.

neuroscience↗