Biology subjects

Zufferey, V.

Publications and source records attributed to Zufferey, V..

7 recordsLinked to original sources

bioRxiv2025

Reduced levels of synaptic vesicle protein 2A in the extracellular vesicles and brain of Alzheimer's disease- associations with Aβ, tau and synaptophysin

BackgroundSynaptic dysfunction plays an important role in Alzheimers disease (AD) and is an emerging imaging and fluid biomarker. Here, we aimed to assess the regional expression of synaptic vesicle glycoprotein 2A (SV2A) in the brain and extracellular vesicles of AD patients and its associations with the APOE {varepsilon}4 allele, amyloid-{beta}, tau pathologies, and other synaptic markers. MethodsMass spectrometry-based synaptosome proteomics was performed on brain-derived extracellular vesicles (BdEVs) isolated from the frontal cortex of 17 AD patients and 4 NCs. Immunohistochemical staining for SV2A, synaptophysin, amyloid-{beta} and phospho-tau was performed on postmortem tissue from the frontal, temporal, and entorhinal cortices and hippocampus of 40 AD patients and 44 nondemented controls (NCs). ResultsReduced levels of synaptic proteins, including synaptotagamin, GAP43, SYT1, SNAP25 and 14-3-3{zeta}, were positively correlated with SV2A and negatively correlated with GFAP and NEFL in BdEVs from AD patients and NCs. We detected lower levels of SV2A in the hippocampus and entorhinal cortex of AD compard to NCs, and in APOE {varepsilon}4 carriers than in noncarriers. SV2A levels were positively correlated with synaptophysin and negatively correlated with the levels of the amyloid-{beta}, phospho-tau, and Braak stages. ConclusionsThis study provides postmortem evidence of synaptic markers and reduced regional levels of SV2A in brain tissue slices and BdEVs from AD patients compared with NCs and in APOE {varepsilon}4 carriers compared to non-carriers. SV2A could serve as a valuable marker for monitoring synaptic degeneration in AD.

neuroscience↗

bioRxiv2025

Astrocyte and mitochondrial footprints in brain-derived extracellular vesicles predict tau pathology

Tauopathies are neurodegenerative disorders characterized by abnormal tau aggregation, with primary 3R (e.g., Picks disease, PiD) and 4R (e.g., progressive supranuclear palsy, PSP) variants posing a significant diagnostic challenge. Here, we examined brain-derived extracellular vesicles (BD-EVs) isolated from the prefrontal cortex of PiD (3R), PSP (4R), and non-demented controls (CTRL) to determine if these vesicles reflect disease-specific proteomic signatures. We found that while tau pathology does not substantially alter BD-EV concentration or the enrichment of core vesicular markers, it does influence their size distribution and protein cargo. BD-EV samples from PiD patients exhibited a greater abundance of small vesicles and distinct protein profiles when compared to PSP and CTRL. Weighted Gene Co-expression Network Analysis (WGCNA) identified four key protein modules to account for variance between patient groups Endoplasmic Reticulum, Mitochondria, Microtubules, and Trivalent Inorganic Cation Transport. In PiD, astrocyte-derived mitochondrial proteins were significantly elevated, whereas neuronal microtubule-related proteins were diminished relative to both PSP and CTRL. Notably, changes in the mitochondrion and microtubule modules enhanced the detection of PiD pathology. Cellular origin annotation revealed a marked shift in BD-EV composition: PiD samples exhibited an increased astrocytic signature, while both PiD and PSP showed a reduction in neuronal proteins compared to CTRL. Crucially, the enrichment of astrocytic mitochondrial and endoplasmic reticulum proteins, alongside reduced neuronal proteins, correlated strongly with the severity of tau pathology (AT8-stained aggregates) in patient brains. These findings demonstrate that BD-EVs capture tau isoform-specific cellular and molecular alterations, offering a window into disease mechanisms at the neuron-glia interface. By linking distinct protein signatures and their cellular origins to tau pathology severity, our results highlight the potential of BD-EV profiling as a biomarker strategy for distinguishing between and monitoring the progression of 3R and 4R tauopathies.

neuroscience↗

bioRxiv2024

Landscape-scale endophytic community analyses in replicated grapevine stands reveal that dieback disease is not caused by specific fungal communities

Tree diebacks are complex and multi-factorial diseases with suspected biotic and abiotic components. Microbiome effects on plant health are challenging to assess due to the complexity of fungal and bacterial communities. Grapevine wood dieback is the main threat to sustainable production worldwide and no causality with microbial species has been established. Here, we aimed to test the hypothesis that grapevine esca disease progression has reproducible drivers in the fungal species community. For this, we analyzed a set of 21 vineyards planted simultaneously with a single susceptible cultivar to provide replication at the landscape scale. We sampled a total of 496 plants across vineyards in two different years to perform deep amplicon sequencing analyses of the fungal communities inhabiting grapevine trunks. The communities were highly diverse with a total of 4,129 amplified sequence variants assigned to 697 distinct species. Individual plants varied in fungal community composition depending on the year of sampling, vineyard location, and disease status. However, we detect no specific fungal species driving symptom development across the vineyards contrary to long-standing expectations. Our study shows how landscape-scale replicated field surveys allow for powerful hypothesis-testing for complex dieback disease drivers and prioritize future research towards additional factors.

microbiology↗

bioRxiv2024

Inverse and Postponed Impacts of Extracellular Tau PHF on Astrocytes and Neurons' Mitochondrial Function

BackgroundTauopathies encompass a spectrum of neurodegenerative disorders which are marked by the pathological aggregation of tau protein into paired helical filaments (PHF-tau), neurofibrillary tangles (NFTs) and Glial-fibrillary tangles (GFTs). These aggregates impair cellular, mitochondrial, and synaptic functions. The emergence of extracellular tau (ePHF-tau), featuring a myriad of isoforms and phosphorylation states, presents a challenge in comprehending its nuanced effects on neural cells, particularly concerning synaptic and mitochondrial integrity. MethodsWe studied the impact of ePHF-tau (2N4R) on different states and ages of primary cultures of rat neuroglia. Using confocal microscopy and proteomic analysis of synaptosomes, we studied the impact of ePHF-tau on neurite and synapse number. We monitored mitochondrial responses in neurons and astrocytes over 72 hours using advanced fluorescence microscopy for dynamic, high-throughput analysis. ResultsTreatment with ePHF-tau has a strong effect on the neurites of immature neurons, but its toxicity is negligible when the neurons are more mature. At the mature stage of their development, we observed a substantial increase in the density of the PSD-95/vGlut1 zone in neurite, suggesting altered synaptic connectivity and ePHF-tau excitotoxicity. Proteomics revealed significant changes in mitochondrial protein in synaptosomes following exposure to ePHF-tau. In the neuronal compartment, real-time imaging revealed rapid and persistent mitochondrial dysfunction, increased ATP production, and reduced mitochondrial turnover. In contrast, we observed increased mitochondrial turnover and filamentation after treatment in the astrocyte processes, indicating cell-specific adaptive responses to ePHF-tau. ConclusionsThis study sheds light on the intricate effects of extracellular tau aggregates on neuronal and astrocytic mitochondrial populations, highlighting how tau pathology can lead to mitochondrial disturbances and synaptic alterations. By delineating the differential responses of neurons and astrocytes to ePHF-tau, our findings pave the way for developing targeted therapeutic interventions to mitigate the detrimental impacts of tau aggregates in neurodegenerative diseases.

neuroscience↗

bioRxiv2023

A systemic approach allows to identify the pedoclimatic conditions most critical in the susceptibility of a grapevine cultivar to esca/Botryosphaeria dieback

Esca and/or Botryosphaeria dieback (esca-BD) are two of the most destructive grapevine trunk diseases in the world, disease complex which remains poorly understood. As some vine cultivars show highly variable susceptibility to esca-BD, we designed a four-year experiment to identify which environmental factors influence the expression of the disease. We collected epidemiological and physiological data once a year for four consecutive years in 19 vineyard plots located in four wine-growing regions of Western Switzerland. We compared these data with climatic data obtained from weather stations for these same plots for four years and over the long term. We also estimated the soil water holding capacity of each plot. Confounding factors were minimal because all vineyards were planted in 2003 with the same cultivar and all plants grafted in the same nursery with genetically homogeneous grafting material. Principal component and regression analyses of combined epidemiological, biotic and pedoclimatic data identified a positive correlation between soil water retention capacity and plant mortality due to esca-BD. These analyses also showed that leaf disease symptoms and apoplexy are more frequent when cold, wet periods are followed - or alternate with - hot, dry periods, and that apoplexy occurs more frequently when weather conditions change abruptly (cold, wet May followed by a hot June) and deviate significantly from long-term climatic conditions. Regression analyses show that the soil water holding capacity impacts less the disease expression when the climate is warm and dry, both at the regional and at year-specific levels. Having identified the most important environmental factors towards expression of esca-BD, this study allows recommendations to be given to the winegrowers for the cultivar studied but can also be used as a model to identify the environmental factors that influence the expression of fungal diseases in other grapevine cultivars, other grapevine trunk diseases and even in other woody plants.

plant biology↗

bioRxiv2023

Accumulation of Tau in Extracellular Vesicles Disturbs the Astrocytic Mitochondrial System

Tauopathies are neurodegenerative disorders involving the accumulation of tau isoforms in cell subpopulations such as astrocytes. The origins of the 3R and 4R isoforms of tau that accumulate in astrocytes remain unclear. Extracellular vesicles (EVs) were isolated from primary neurons overexpressing 1N3R or 1N4R tau or from human brain extracts (progressive supranuclear palsy or Pick disease patients or controls) and characterized (electron microscopy, nanoparticle tracking analysis (NTA), proteomics). After the isolated EVs were added to primary astrocytes or human iPSC-derived astrocytes, tau transfer and mitochondrial system function were evaluated (ELISA, immunofluorescence, MitoTracker staining). We demonstrated that neurons in which 3R or 4R tau accumulated had the capacity to transfer tau to astrocytes and that EVs were essential for the propagation of both isoforms of tau. Treatment with tau-containing EVs disrupted the astrocytic mitochondrial system, altering mitochondrial morphology, dynamics and redox state. Although similar levels of 3R and 4R tau were transferred, 3R tau-containing EVs were significantly more damaging to astrocytes than 4R tau-containing EVs. Moreover, EVs isolated from the brain fluid of patients with different tauopathies affected mitochondrial function in astrocytes derived from human iPSCs. Our data highlight that tau pathology spreads to surrounding astrocytes via EVs-mediated transfer and modify their function.

neuroscience↗

bioRxiv2022

Quantifying trade-offs in the choice of ribosomal barcoding markers for fungal amplicon sequencing: a case study on the grapevine trunk mycobiome

The evolution of sequencing technology and multiplexing has rapidly expanded our ability to characterize fungal diversity in the environment. However, obtaining an unbiased assessment of the fungal community using ribosomal markers remains challenging. Longer amplicons were shown to improve taxonomic resolution and resolve ambiguities by reducing the risk of spurious operational taxonomic units. We examined the implications of barcoding strategies by amplifying and sequencing two ribosomal DNA fragments. We analyzed the performance of the full internal transcribed spacer (ITS) and a longer fragment including also a part of the 28S replicated on 60 grapevine trunk core samples. Grapevine trunks harbor highly diverse fungal communities with implications for disease development. Using identical handling, amplification and sequencing procedures, we obtained higher sequencing depths for the shorter ITS amplicon. Despite the more limited access to polymorphism, the overall diversity in amplified sequence variants was higher for the shorter ITS amplicon. We detected no meaningful bias in the phylogenetic composition due to the amplicon choice across analyzed samples. Despite the increased resolution of the longer ITS-28S amplicon, the higher and more consistent yields of the shorter amplicons produced a clearer resolution of the fungal community of grapevine stem samples. Our study highlights that the choice of ribosomal amplicons should be carefully evaluated and adjusted according to specific goals.

microbiology↗