Biology subjects

Mouffle, C.

Publications and source records attributed to Mouffle, C..

4 recordsLinked to original sources

bioRxiv2023

Astrocyte aquaporin mediates a tonic water efflux maintaining brain homeostasis

Brain water homeostasis not only provides a physical protection, but also determines the diffusion of chemical molecules key for information processing and metabolic stability. As a major type of glia in brain parenchyma, astrocytes are the dominant cell type expressing aquaporin water channel. How astrocyte aquaporin contributes to brain water homeostasis in basal physiology remains to be understood. We report that astrocyte aquaporin 4 (AQP4) mediates a tonic water efflux in basal conditions. Acute inhibition of astrocyte AQP4 leads to intracellular water accumulation as optically resolved by fluorescence-translated imaging in acute brain slices, and in vivo by fiber photometry in mobile mice. We then show that aquaporin-mediated constant water efflux maintains astrocyte volume and osmotic equilibrium, astrocyte and neuron Ca2+ signaling, and extracellular space remodeling during optogenetically induced cortical spreading depression. Using diffusion-weighted magnetic resonance imaging (DW-MRI), we observed that in vivo inhibition of AQP4 water efflux heterogeneously disturbs brain water homeostasis in a region-dependent manner. Our data suggest that astrocyte aquaporin, though bidirectional in nature, mediates a tonic water outflow to sustain cellular and environmental equilibrium in brain parenchyma. Significance statementOur brain is immersed, thus protected, in a water environment. It ensures intra- and extracellular molecular diffusion, which is vital for brain function and health. Brain water homeostasis is maintained by dynamic water transport between different cell types. Astrocytes are a main type of glial cell widely distributed in brain parenchyma, expressing the bidirectional aquaporin water channel. Here we show that in basal conditions, aquaporin channel mediates a tonic water efflux from astrocytes. This mechanism maintains astrocyte volume stability, activity-gated brain parenchyma remodeling and brain water homeostasis. Our finding sheds light on how astrocytes regulate water states in the brain, and will help to understand brain allostasis in specific life contexts.

physiology↗

bioRxiv2022

Hypothalamic astrocyte control systemic glucose metabolism and energy balance via regulation of extra-synaptic glutamate signaling

The hypothalamus is key in the control of energy balance. However, to this day strategies targeting hypothalamic neurons failed to provide viable option to treat most metabolic diseases. Conversely, the role of astrocytes in systemic metabolic control has remained largely unexplored. Here we show that obesity promotes anatomically restricted remodeling of hypothalamic astrocyte activity. In the paraventricular nucleus (PVN) of the hypothalamus, chemogenetic manipulation of astrocytes results in bidirectional control of neighboring neuron activity, autonomic outflow, glucose metabolism and energy balance. Such process recruits a mechanism involving the astrocytic control of ambient glutamate levels, which becomes defective in obesity. Positive or negative chemogenetic manipulation of PVN astrocyte Ca2+ signals respectively worsen or improves metabolic status of diet-induced obese mice. Collectively, these findings highlight a yet unappreciated role for astrocyte in the direct control of systemic metabolism and suggest potential targets for anti-obesity strategy.

physiology↗

bioRxiv2020

Early diversity in the firing pattern of embryonic Renshaw cells: just a synergy between two opposite voltage-dependent currents

Renshaw cells (V1R) are excitable as soon as they reach their final location next to the spinal motoneurons and are functionally heterogeneous. Using multiple experimental approaches, in combination with biophysical modeling and dynamical systems theory, we analyzed, for the first time, the mechanisms underlying the electrophysiological properties of V1R during early embryonic development of the spinal cord locomotor networks (E11.5-E16.5). We found that these interneurons are subdivided into several functional clusters from E11.5 and then display an unexpected transitory involution process during which they lose their ability to sustain tonic firing. We demonstrated that the essential factor controlling the diversity of the discharge pattern of embryonic V1R is the ratio of a persistent sodium conductance to a delayed rectifier potassium conductance. Taken together, our results reveal how a simple mechanism, based on the synergy of two voltage-dependent conductances that are ubiquitous in neurons, can produce functional diversity in V1R and control their early developmental trajectory.

neuroscience↗

bioRxiv2020

The floor-plate of His is a non-neuronal electrical conduction pathway

In the developing central nervous system, electrical signaling is thought to rely exclusively on differentiating neurons as they acquire the ability to generate action potentials. Accordingly, the neuroepithelial progenitors (NEPs) giving rise to all neurons and glial cells during development have been reported to remain electrically passive. Here, we investigated the physiological properties of NEPs in the mouse spinal cord at the onset of spontaneous neural activity (SNA) initiating motor behavior in embryos. Using patch-clamp recordings, we discovered that spinal NEPs exhibit spontaneous membrane depolarizations during episodes of SNA. These recurrent depolarizations exhibited a ventral-to-dorsal gradient with the highest amplitude located in the floor-plate - the ventral-most part of the neuroepithelium. Paired-recordings revealed that NEPs are extensively coupled via gap-junctions and form a single electrical syncytium. Although other NEPs were electrically passive, we discovered that floor-plate NEPs have the unique ability to generate large Na+/Ca++ action potentials. Unlike neurons, floor-plate action potentials relied primarily on the activation of voltage-gated T-type calcium channels (TTCCs). In situ hybridization showed that all 3 known subtypes of TTCCs are highly and predominantly expressed in the floor-plate. During SNA, we found that acetylcholine released by motoneurons recurrently trigger floor-plate action potentials by acting through nicotinic acetylcholine receptors. Finally, by expressing the genetically encoded calcium indicator GCaMP6f in the floor plate, we demonstrated that neuroepithelial action potentials are associated with calcium waves and propagate along the entire length of the spinal cord. By unraveling a novel physiological mechanism generating electrical signals which can propagate independently from neurons across a neural structure, our work significantly changes our understanding of the development, origin and extent of electrical signaling in the central nervous system. HIGHLIGHTSO_LISpinal neuroepithelial progenitors (NEP) are depolarized during spontaneous neural activity C_LIO_LINEPs form a single electrical syncytium connected by gap junctions C_LIO_LIFloor-plate NEPs generate large Na+/Ca++ action potentials in response to acetylcholine C_LIO_LINeuroepithelial action potentials propagate across the entire spinal cord C_LI

neuroscience↗