Biology subjects

Doudnikoff, E.

Publications and source records attributed to Doudnikoff, E..

4 recordsLinked to original sources

bioRxiv2025

Decoding Amyloid Plaque Penetrability: Exploring Extracellular Space and Rheology2in Plaque-rich Cortex

A hallmark of Alzheimers disease (AD) is the accumulation of amyloid plaques, primarily composed of misfolded amyloid {beta} (A{beta}) peptides. We employed complementary high-resolution imaging techniques to investigate the plaque penetrability and the extracellular space (ECS) rheology in a mouse model of AD. Two-photon shadow imaging in vivo confirmed that a dense ring of cells surrounds cortical amyloid plaques but highlighted the diffusional penetrability of the amyloid core. Quantum dot tracking unveiled that ECS diffusional parameters are heterogeneous in and around plaques, with an elevated diffusivity within and around plaques compared to WT-tissue. The amyloid core showed low nanoparticle density, varying by plaque phenotype. Carbon nanotube tracking confirmed these altered local rheological properties at the level of the whole cortex of AD mice. Finally, we found the extracellular matrix to be dysregulated within the amyloid plaque, which may account for the observed alterations in diffusivity. Our study provides fresh insights for understanding A{beta} plaque penetration, a prerequisite for therapeutic development.

neuroscience↗

bioRxiv2022

Encoding social preference by interhemispheric neurons in the Insula

The Insula is a multisensory relay that participates in socio-emotional processing through multiple projections to sensory, cognitive, emotional, and motivational regions. Interestingly, the Insula interhemispheric projection to the contralateral Insula is a strong but understudied projection. Using cutting-edge neuroanatomy, ex vivo and in vivo electrophysiology associated with specific circuit manipulation, we unraveled the nature and role of Insula interhemispheric communication in social and anxiety processing in mice. In this study, we 1) characterized the anatomical and molecular profile of the interhemispheric neurons of the Insula, 2) highlighted that stimulation of this neuronal subpopulation triggers excitation in the Insula interhemispheric circuit 3) uncovered their engagement in social processing. In conclusion, this study demonstrates that interhemispheric neurons of the Insula constitute a unique class of Insula neurons and proposes new meaningful insights into the neuronal mechanisms underlying social behavior.

neuroscience↗

bioRxiv2020

Emergence of stealth polymorphs that escape α-synuclein amyloid monitoring, take over and acutely spread in neurons

The conformational strain diversity characterizing -synuclein (-syn) amyloid fibrils is possibly at the origin of the different clinical presentations of synucleinopathies. Experimentally, various -syn fibril polymorphs have been obtained from distinct fibrillization conditions by altering the medium constituents and were selected by amyloid monitoring using the probe Thioflavin T (ThT). We report here that besides classical ThT positive products, fibrillization in saline simultaneously gives rise to competing fibril polymorphs that are invisible to ThT (stealth polymorphs), and that can take over. Due to competition, spontaneous generation of such stealth polymorphs bears on the apparent fibrillization kinetics and on the final plateau values. Their emergence has thus been ignored so far or mistaken for fibrillization inhibitions/failures. Compared to their ThT-positive counterparts, and as judged from their chemical shift resonances fingerprint, these new stealth polymorphs present a yet undescribed atomic organization and show an exacerbated propensity (approx. 20-fold) towards self-replication in cortical neurons. They also trigger a long distance synucleinopathic spread along nigro-striatal projections in vivo. In order to rapidly screen fibrillization products for the presence of such stealth polymorphs, we designed a simple multiplexed assay that can be easily and rapidly operated. This assay allows us to demonstrate the sustainability of the conformational replication of these novel and particularly invasive strains. It should also be of help to avoid erroneous upstream interpretations of fibrillization rates based on sole ThT, and to expedite further structural and functional characterization of stealth amyloid assemblies. One Sentence Summarystealth -synuclein fibrils take over

neuroscience↗

bioRxiv2019

Identification of distinct pathological signatures induced by patient-derived α-synuclein structures in non-human primates

AO_SCPLOWBSTRACTC_SCPLOWDopaminergic neuronal cell death, associated with intracellular -synuclein (-syn)-rich protein aggregates (termed Lewy bodies), is a well-established characteristic of Parkinsons disease. Much evidence, accumulated from multiple experimental models has suggested that -syn plays a role in PD pathogenesis, not only as a trigger of pathology but also as a mediator of disease progression through pathological spreading. Here we have used a machine learning-based approach to identify unique signatures of neurodegeneration in monkeys induced by distinct -syn pathogenic structures derived from PD patients. Unexpectedly, our results show that, in non-human primates, a small amount of singular -syn aggregates is as toxic as larger amyloid fibrils present in the LBs, thus reinforcing the need for preclinical research in this species. Furthermore, our results provide evidence supporting the true multifactorial nature of PD as multiple causes can induce similar outcome regarding dopaminergic neurodegeneration.

neuroscience↗