Biology subjects

Marie, H.

Publications and source records attributed to Marie, H..

9 recordsLinked to original sources

bioRxiv2025

AETA peptide drives Alzheimer's disease signature of synapse dysfunction

Alzheimers disease (AD), the leading cause of dementia, is characterized by early synaptic dysfunction that precedes overt cognitive decline. While amyloid-{beta} and Tau remain central to AD pathogenesis, molecular triggers of synapse weakening remain unclear. Here, we investigated AETA, a novel brain-secreted peptide derived from amyloid precursor protein (APP), as a potential mediator of synapse dysfunction in AD. We previously identified AETA as a unique modulator of NMDA receptor activity in the healthy brain; however, its role in AD etiology was yet to be explored. Post-mortem analyses of human hippocampal and prefrontal cortex tissues revealed significantly elevated AETA levels in AD patients, particularly in females. To further explore the contribution of AETA to AD synaptic pathology, we analyzed a new mouse model, the AETA-m mouse, exhibiting chronically increased brain AETA expression. Hippocampi of female AETA-m mice display an increase in the number of astrocyte and microglia, but no overt neuroinflammation. RNA sequencing of female AETA-m hippocampi revealed alterations in synaptic gene expression that closely paralleled those observed in vulnerable human AD brain regions, most notably in the hippocampus. These two phenotypes were absent in males. Functionally, hippocampal neurons from AETA-m mice displayed impaired NMDA receptor signaling, dendritic spine loss, and memory deficits especially in females, mirroring early AD-associated synaptic dysfunction. Together, these findings identify AETA as a novel key contributor of synaptic vulnerability in AD and associated memory processing, especially in females. Targeting AETA signaling may therefore offer new therapeutic avenues for preventing or mitigating synaptic and cognitive decline in AD.

neuroscience↗

bioRxiv2025

Dicer accumulates in cytoplasmic foci upon alphavirus infection and plays a proviral role in Myotis myotis bat cells

Bats are reservoirs for many viruses that frequently cause epidemics in humans and animals. It is thus critical to better understand their immune system and mechanisms of antiviral immunity. Despite an increasing number of studies, much is still unknown about the molecular mechanisms that govern bat-virus interactions, especially given the large diversity of bat species. Dicer is a conserved ribonuclease with multiple activities that can modulate antiviral immunity, including the detection of viral RNA as part of the RNA interference (RNAi) pathway, the maturation of micro RNAs, and the direct inhibition of innate immunity in mouse and human cells. In view of these complex activities of Dicer, we tested its antiviral activity in Myotis myotis nasal epithelial cells. Surprisingly, we did not see strong evidence of RNAi in these cells, but instead saw a proviral effect of Dicer for two alphaviruses, Sindbis and Semliki forest virus. We also observed a striking relocalization of Dicer to cytoplasmic foci upon infection with these viruses, which did not occur in the several human cell lines we tested. These foci contained dsRNA and viral plus strand RNA, suggesting that they are sites of viral replication. Finally, we found that factors specific to M. myotis cells are needed for Dicer relocalization. Overall, we propose that Dicer can play different roles in different bat species and/or cell types, and is being repurposed by alphaviruses to promote viral replication.

microbiology↗

bioRxiv2025

Cortico-striatal dynamics across working memory stages

Working memory depends on the temporary retention and manipulation of information, bridging the gap between short-term memory and information processing functions. However, when the same working memory task is repeated over several days, it raises the question of whether the rule or task set becomes automated (or proceduralized). The medial prefrontal cortex (mPFC) is crucial for working memory. Yet, the role of the dorsolateral striatum (DLS) in the automation (proceduralization) of rules or task sets remains to be clarified. Using a longitudinal approach of the "delay non-match to place" (DNMP) task in a T-maze combined to chemogenetic inhibition of the mPFC or DLS in mice, we show that the mPFC becomes less critical in the maintenance phase of the task as behaviour progressively shifts toward automation. During this phase, the DLS facilitates automated processing. Accordingly, silencing through chemogenetic inhibition of the DLS during maintenance triggers an adaptation in learning strategies, reactivating a goal-directed behaviour. Our findings strengthen memory traces as a dynamic reorganization of neural networks, challenging the classical view of information migration between brain structures. We here propose that the memory trace remains in a dormant state--less energy-consuming for the system--while still allowing for rapid flexibility in case of task modification.

neuroscience↗

bioRxiv2025

Combination of Cas9 and adeno-associated vectors (AAVs) enables efficient in vivo knockdown of precise miRNAs in the rodent brain

Although the advent of Cas9 technology has expanded our ability to precisely edit the genome, manipulating microRNAs in vivo has been shown to be particularly challenging, especially in the brain. Here, we sought to generate novel tools aiming at targeting and efficiently downregulating defined microRNAs species in a cell-specific manner so that their function in discrete neuronal networks could be investigated. Focusing on miR-124, a microRNA highly expressed in the mammalian brain and transcribed from three independent chromosomal loci, we designed and validated different guide RNAs directed against this miRNA. In vitro, our Cas9 designs show not only a significant reduction in miR-124 levels but also a functional effect on miR-124 silencing. Similarly, when packed into AAV vectors and injected into the mouse cortex, miR-124-Cas9 vectors strongly downregulate miR-124 levels without affecting the expression of other miRNAs. In parallel, levels of endogenous miR-124 targets exhibit a significant increase supporting the release of its silencing activity. To functionally validate our tools, we provide evidences that deletion of miR-124 in the subventricular zone altered migration of newly generated neurons into the olfactory bulb. Finally, we also showed that our vectors modified the Ca2+ permeability of AMPA receptors, a robust functional output downstream of miR-124. These tools are expected to help elucidating miRNA function in complex experimental settings such as brain networks in vivo.

neuroscience↗

bioRxiv2023

Rapid Adeno-Associated Virus Genome Quantification with Amplification-Free CRISPR-Cas12a

Efficient manufacturing of recombinant Adeno-Associated Viral (rAAV) vectors to meet rising clinical demand remains a major hurdle. One of the most significant challenges is the generation of large amounts of empty capsids without the therapeutic genome. There is no standardized analytical method to accurately quantify the viral genes, and subsequently the empty-to-full ratio, making the manufacturing challenges even more complex. We propose the use of CRISPR diagnostics (CRISPR-Dx) as a robust and rapid approach to determine AAV genome titers. We designed and developed the CRISPR-AAV Evaluation (CRAAVE) assay to maximize sensitivity, minimize time-to-result, and provide a potentially universal design for quantifying multiple transgene constructs encapsidated within different AAV serotypes. We also demonstrate an on-chip CRAAVE assay with lyophilized reagents to minimize end user assay input. The CRAAVE assay was able to detect AAV titers as low as 7e7 vg/mL with high precision (<3% error) in quantifying unknown AAV titers when compared with conventional quantitative PCR (qPCR) method. The assay only requires 30 minutes of assay time, shortening the analytical workflow drastically. Our results suggest CRISPR-Dx could be a promising tool for efficient rAAV genome titer quantification and has the potential to revolutionize biomanufacturing process analytical technology (PAT). Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=183 HEIGHT=200 SRC="FIGDIR/small/567134v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@1bfce18org.highwire.dtl.DTLVardef@17393c9org.highwire.dtl.DTLVardef@eb7c1forg.highwire.dtl.DTLVardef@2203cd_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2022

Age-dependent NMDA receptor function is regulated by the Amyloid Precursor Protein

N-methyl-D-aspartate receptors (NMDARs) are critical for the maturation and plasticity of glutamatergic synapses. In the hippocampus, NMDARs mainly contain GluN2A and/or GluN2B regulatory subunits. The amyloid precursor protein (APP) has emerged as a putative regulator of NMDARs, but the impact of this interaction to their function is largely unknown. By combining patch-clamp electrophysiology and molecular approaches, we unravel a dual mechanism by which APP controls GluN2B-NMDARs, depending on the life stage. We show that APP is highly abundant specifically at the postnatal postsynapse. It interacts with GluN2B-NMDARs, controlling its synaptic content and mediated currents, both in infant mice and primary neuronal cultures. Upon aging, the APP amyloidogenic derived C-terminal fragments, rather than APP full length, contribute to aberrant GluN2B-NMDAR currents. Accordingly, we found that the APP processing is increased upon aging, both in mice and human brain, and interfering with this mechanism normalized the aberrant currents. While the first mechanism might be essential for synaptic maturation during development, the latter could contribute to age-related synaptic impairments. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=99 SRC="FIGDIR/small/500736v1_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@1c4d540org.highwire.dtl.DTLVardef@18c7b67org.highwire.dtl.DTLVardef@1f9e482org.highwire.dtl.DTLVardef@109274f_HPS_FORMAT_FIGEXP M_FIG C_FIG In briefRajao-Saraiva et al. identified the APP full-length protein as a regulator of glutamatergic transmission in immature synapses, by controlling GluN2B synaptic content and mediated currents during postnatal development. Upon aging, the APP amyloidogenic derived C-terminal fragments, rather than APP full length, contribute to aberrant GluN2B-NMDAR currents. Our work highlights the importance of keeping APP processing under tight control, to ensure the normal functioning of glutamatergic synapses, being particularly relevant to understand age-related synaptic impairments and AD.

neuroscience↗

bioRxiv2021

A stochastic model of hippocampal synaptic plasticity with geometrical readout of enzyme dynamics

Discovering the rules of synaptic plasticity is an important step for understanding brain learning. Existing plasticity models are either 1) top-down and interpretable, but not flexible enough to account for experimental data, or 2) bottom-up and biologically realistic, but too intricate to interpret and hard to fit to data. To avoid the shortcomings of these approaches, we present a new plasticity rule based on a geometrical readout mechanism that flexibly maps synaptic enzyme dynamics to predict plasticity outcomes. We apply this readout to a multi-timescale model of hippocampal synaptic plasticity induction that includes electrical dynamics, calcium, CaMKII and calcineurin, and accurate representation of intrinsic noise sources. Using a single set of model parameters, we demonstrate the robustness of this plasticity rule by reproducing nine published ex vivo experiments covering various spike-timing and frequency-dependent plasticity induction protocols, animal ages, and experimental conditions. Our model also predicts that in vivo-like spike timing irregularity strongly shapes plasticity outcome. This geometrical readout modelling approach can be readily applied to other excitatory or inhibitory synapses to discover their synaptic plasticity rules.

neuroscience↗

bioRxiv2020

The non-adrenergic imidazoline-1 receptor protein Nischarin is a key regulator of astrocyte glutamate uptake

Astrocytic GLT-1 is the main glutamate transporter involved in glutamate buffering in the brain, pivotal for glutamate removal at excitatory synapses to terminate neurotransmission and for preventing excitotoxicity. We show here that the surface expression and function of GLT-1 can be rapidly modulated through the interaction of its N-terminus with the nonadrenergic imidazoline-1 receptor protein, Nischarin. The phox domain of Nischarin is critical for interaction and internalization of surface GLT-1. Using live super-resolution imaging, we found that glutamate accelerated Nischarin-GLT-1 internalization into endosomal structures. The surface GLT-1 level increased in Nischarin knockout astrocytes, and this correlated with a significant increase in transporter uptake current. Furthermore, Nischarin knockout in astrocytes is neuroprotective against glutamate excitotoxicity. These data provide new molecular insights into regulation of GLT-1 surface level and function and suggest novel drug targets for the treatment of neurological disorders. HighlightsO_LIThe phox domain of Nischarin interacts with the N-terminal tail of the main astrocyte glutamate transporter, GLT-1. C_LIO_LINischarin promotes internalization of GLT-1 to endosomes. C_LIO_LIGlutamate modulates GLT-1 surface levels via regulation of the Nischarin-GLT-1 interaction. C_LIO_LIGenetic loss of Nischarin significantly increases GLT-1 surface expression, resulting in increased glutamate transport currents and enhanced neuroprotection. C_LI

neuroscience↗

bioRxiv2019

Anti-inflammatory treatment with FTY720 starting after onset of symptoms reverses synaptic and memory deficits in an AD mouse model

Therapeutical approaches providing effective medication for Alzheimers disease (AD) patients after disease onset are urgently needed. Repurposing FDA approved drugs like fingolimod (FTY720) for treatment of AD is a promising way to reduce the time to bring such medication into clinical practice. Previous studies in AD mouse models suggested that physical exercise or changed lifestyle can delay AD related synaptic and memory dysfunctions when treatment started in juvenile animals long before onset of disease symptoms. Here, we addressed whether the FDA approved drug fingolimod rescues AD related synaptic deficits and memory dysfunction in an APP/PS1 AD mouse model when medication starts after onset of symptoms (at 5 months). Male mice received intraperitoneal injections of fingolimod for 1-2 months starting at 5-6 months. This treatment rescued spine density as well as long-term potentiation in hippocampal CA1 pyramidal neurons, and ameliorated dysfunctional hippocampus-dependent memory that was observed in untreated APP/PS1 animals at 6-7 months of age. Immunohistochemical analysis with markers of microgliosis (Iba1) and astrogliosis (GFAP) revealed that our fingolimod treatment regime strongly down regulated neuro-inflammation in the hippocampus and cortex of this AD model. These effects were accompanied by a moderate reduction of A{beta} accumulation in hippocampus and cortex. Our results suggest that fingolimod, when applied after onset of disease symptoms in an APP/PS1 mouse model, rescues synaptic pathology and related memory performance deficits observed in untreated AD mice, and that this beneficial effect is mediated via anti-neuroinflammatory actions of the drug on microglia and astrocytes.

neuroscience↗