Biology subjects

Merour, E.

Publications and source records attributed to Merour, E..

4 recordsLinked to original sources

bioRxiv2026

Molecular characterization of thermo-adapted Novirhabdovirus variants and virulence in vivo in rainbow trout and zebrafish at different temperatures.

Controlling viral diseases in fish is a challenge for the sustainable development of aquaculture and improving the health of fish farms. Infectious hematopoietic necrosis virus (IHNV) is a major pathogen in aquaculture. It infects cold-water fish, but loses its infectivity at temperatures above 20{degrees}C. Since fish are poikilothermic animals, their body temperature fluctuates according to that of their environment. Faced with current climate change, it is crucial to understand how these pathogens will adapt to rising temperatures. Through a strategy simulating the impact of global warming, this virus has been progressively thermo-adapted to 25{degrees}C. The selected variant, IHNV25, replicates at 25{degrees}C while maintaining efficient replication at low temperatures, like its parental strain. Genome sequencing and a reverse genetics approach revealed that only 9 amino acid substitutions, distributed across 4 of the 6 viral genes, were essential for thermo-adaptation. Although IHNV25 was highly attenuated in its natural host, the rainbow trout, at any temperatures, it proved highly virulent when injected in zebrafish larvae at 20{degrees}C and 25{degrees}C, inducing severe symptoms identical to those observed in trout (hemorrhages, oedema, and exophthalmia). At both temperatures, mortality was preceded by a massive viral replication and a delayed and inefficient interferon and inflammatory response. Unlike the parental strain, IHNV25 was also capable of infecting larvae by bath immersion at 25{degrees}C, entering via the caudal fin, thus demonstrating its ability to cross the species barrier. The identification of viral markers of thermo-adaptation will therefore be of great interest for the epidemiological surveillance of field isolates.

microbiology↗

bioRxiv2026

Oligodendrocyte stress response as a driver of vascular dementia

Vascular dementia (VaD) is a prevalent and devastating neurocognitive disorder characterized by profound white matter damage, yet the precise cellular mechanisms linking cerebrovascular stress to demyelination remain poorly understood. Here, we characterize the impact of a chronic cardiometabolic stress regimen combining a high-fat diet and hypertension (HF/HBP) on central nervous system structure and function. Adult HF/HBP mice exhibit progressive oligodendroglial cell loss and myelin thinning, followed by cognitive impairments, anxiety-like behavior, and memory deficits that recapitulate clinical features of VaD. Mechanistically, we identify the integrated stress response (ISR) as a central driver of this pathology; pharmacological inhibition of the ISR restores myelination, while cell-specific genetic deletion of the ISR-activating kinase PERK from oligodendrocytes fully protects mice from HF/HBP-induced pathological and behavioral defects. Furthermore, we provide translational evidence that the ISR is activated in oligodendrocytes in human cases of cerebrovascular disease. Together, these findings reveal a critical, cell-autonomous role for oligodendroglial ISR activation during cerebrovascular stress and position this pathway as a viable therapeutic target to mitigate VaD pathogenesis.

neuroscience↗

bioRxiv2025

In silico reconstruction of a salmonid alphavirus virion reveals distinctive structural and molecular features implicated in virulence in vivo

Salmonid alphavirus (SAV) poses a significant disease threat to aquaculture. Recently, new alphaviruses from several fish species have been discovered. However, little is known about their biology and diseases potential. Alphaviruses are considered to have originated from a marine environment; therefore, studying fish alphaviruses can inform on the evolutionary history of the genus. Contrary to many terrestrial alphaviruses, there are currently no experimentally-determined structures for aquatic alphaviruses, severely limiting their study. In this work, we harness the power of structural bioinformatics and AlphaFold to reconstruct an entire SAV virion, thereby revealing an exposed and distinctive -helical feature in its E2 envelope protein. Using an integrative approach, we explore the sequence diversity and evolutionary conservation of this predicted feature and investigate the functional consequences of variations on viral fitness and virulence. This study provides a novel framework paving the way to better understand aquatic alphavirus pathogenicity and host species adaptation.

microbiology↗

bioRxiv2022

Transient regulation of focal adhesion via Tensin3 is required for nascent oligodendrocyte differentiation

The differentiation of oligodendroglia from oligodendrocyte precursor cells (OPCs) to complex and extensive myelinating oligodendrocytes (OLs) is a multistep process that involves largescale morphological changes with significant strain on the cytoskeleton. While key chromatin and transcriptional regulators of differentiation have been identified, their target genes responsible for the morphological changes occurring during OL myelination are still largely unknown. Here, we show that the regulator of focal adhesion, Tensin3 (Tns3), is a direct target gene of Olig2, Chd7, and Chd8, transcriptional regulators of OL differentiation. Tns3 is transiently upregulated and localized to cell processes of immature OLs, together with integrin-{beta}1, a key mediator of survival at this transient stage. Constitutive Tns3 loss-of-function leads to reduced viability in mouse and humans, with surviving knockout mice still expressing Tns3 in oligodendroglia. Acute deletion of Tns3 in vivo, either in postnatal neural stem cells (NSCs) or in OPCs, leads to a two-fold reduction in OL numbers. We find that the transient upregulation of Tns3 is required to protect differentiating OPCs and immature OLs from cell death by preventing the upregulation of p53, a key regulator of apoptosis. Altogether, our findings reveal a specific time window during which transcriptional upregulation of Tns3 in immature OLs is required for OL differentiation likely by mediating integrin-{beta}1 survival signaling to the actin cytoskeleton as OL undergo the large morphological changes required for their terminal differentiation.

neuroscience↗