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Steady-state neuron-predominant LINE-1 encoded ORF1p protein and LINE-1 RNA increase with aging in the mouse and human brain
No full textInternational audienceRecent studies have established a reciprocal causal link between aging and the activation of transposable elements, characterized in particular by a de-repression of LINE-1 retrotransposons. These LINE-1 elements represent 21% of the human genome, but only a minority of these sequences retain the coding potential essential for their mobility. LINE-1 encoded proteins can induce cell toxicity implicated in aging and neurodegenerative diseases. However, our knowledge of the expression and localization of LINE-1-encoded proteins in the central nervous system is limited. Using a novel approach combining atlas-based brain mapping with deep-learning algorithms on large-scale pyramidal brain images, we unveil a heterogeneous, neuron-predominant and widespread ORF1p expression throughout the murine brain at steady-state. In aged mice, ORF1p expression increases significantly which is corroborated in human post-mortem dopaminergic neurons by an increase in young LINE-1 elements including those with open reading frames. Mass spectrometry analysis of endogenous mouse ORF1p revealed novel, neuron-specific protein interactors. These findings contribute to a comprehensive description of the dynamics of LINE-1 and ORF1p expression in the brain at steady-state and in aging and provide insights on ORF1p protein interactions in the brain
Searching for HI around MHONGOOSE galaxies via spectral stacking
No full textInternational audienceThe observed star formation rates of galaxies in the Local Universe suggests that they are replenishing their gas reservoir across cosmic time. Cosmological simulations predict that this accretion of fresh gas can occur in a hot or a cold mode, yet the existence of low column density (∼10 17 cm −2 ) neutral atomic hydrogen (H I ) tracing the cold mode has not been unambiguously confirmed by observations. We present the application of unconstrained spectral stacking to attempt to detect the emission from this H I in the circumgalactic medium (CGM) and intergalactic medium (IGM) of six nearby star-forming galaxies from the MHONGOOSE sample for which full-depth observations are available. Our stacking procedure consists of a standard spectral stacking algorithm coupled with a one-dimensional spectral line finder designed to extract a reliable signal close to the noise level. In agreement with previous studies, we find that the amount of signal detected outside the H I disk is much smaller than implied by simulations. Furthermore, the column density limit that we achieve via stacking (∼10 17 cm −2 ) suggests that direct detection of the neutral CGM and IGM component might be challenging in the future, even with the next generation of radio telescopes
HI within and around observed and simulated galaxy discs: Comparing MeerKAT observations with mock data from TNG50 and FIRE-2
No full textInternational audienceExtragalactic gas accretion and outflows driven by stellar and active galactic nucleus (AGN) feedback are expected to influence the distribution and kinematics of gas in and around galaxies. Atomic hydrogen (H I ) is an ideal tracer of these processes, and it is uniquely observable in nearby galaxies. Here we made use of wide-field (1° ×1°), spatially resolved (down to 22″), high-sensitivity (∼10 18 cm −2 ) H I observations of five nearby spiral galaxies with stellar mass of ∼5 × 10 10 M ⊙ , taken with the MeerKAT radio telescope. Four of these were observed as part of the MHONGOOSE survey. We characterise the main H I properties in regions of a few hundred kiloparsecs around the discs of these galaxies, and compare them with synthetic H I data from a sample of 25 similarly massive star-forming galaxies from the TNG50 (20) and FIRE-2 (5) suites of cosmological hydrodynamical simulations. Overall, the simulated systems have H I and molecular hydrogen (H 2 ) masses in good agreement with the observations, but only when a pressure-based H 2 recipe is employed. The other recipes that we tested overestimate the H 2 -to-H I mass fraction by up to an order of magnitude. On a local scale, we find two main discrepancies between the observed and simulated data. First, the simulated galaxies show a more irregular H I morphology than the observed galaxies, due to the presence of H I with column density < 10 20 cm −2 up to ∼100 kpc from the galaxy centre, even though they inhabit more isolated environments than the observed targets. Second, the simulated galaxies and in particular those from the FIRE-2 suite, feature more complex and overall broader H I line profiles than the observed galaxies. We interpret this as being due to the combined effect of stellar feedback and gas accretion, which lead to a large-scale gas circulation that is more vigorous than in the observed galaxies. Our results indicate that, with respect to the simulations, gentler processes of gas inflows and outflows are at work in the nearby Universe, leading to more regular and less turbulent H I discs
Gravitational torques from lopsided young stellar component sustain high black hole accretion rates in NGC 4593
No full textInternational audienceContext. Supermassive black holes (SMBHs) grow primarily through gas accretion, observed as active galactic nuclei (AGNs). While mergers can drive luminous AGN episodes, secular processes may fuel a substantial portion of cosmic black hole growth. Whether these mechanisms can sustain high black hole accretion rates remains uncertain. Aims. The aim of this study is to identify the secular mechanism driving high SMBH accretion rates, by targeting a galaxy with a moderately massive SMBH, high central gas densities, accretion rates of a few percent of the Eddington limit, and gas kinematics resolved close to black-hole-dominated scales. Methods. A blind search led to the identification of NGC 4593, which is representative of the AGN population driving BH mass density growth since z = 1. Combining HST imaging, VLT/MUSE spectroscopy, and ALMA imaging, we resolve molecular and ionised gas kinematics close to the sphere of influence of the SMBH. Results. A prominent single-arm (“ m = 1”) molecular gas spiral with log M mol /M ⊙ = 8.1 ± 0.3 extends from 1.3 kpc down to the SMBH’s sphere of influence (1.7 −0.2 +0.5 pc). Star formation in the spiral is inefficient (SFR = 4.9 × 10 −2 M ⊙ /yr, ⟨ t dep ⟩=3.9 ± 0.6 Gyr), whereas the gas inflow rate exceeds the SFR by two orders of magnitude and is sufficient to sustain the current SMBH accretion rate for ≥35 Myr, enabling ∼10% SMBH growth. A young, lopsided stellar component (log M ⋆ /M ⊙ = 7.5 − 9.3) exerts torques on the molecular gas, likely driving the gas inflow. This young stellar component may serve as both a cause and a product of sustained gas funnelling towards the SMBH. Conclusions. These findings provide evidence for the sustained secular m = 1 feeding mode at high SMBH accretion rates, linking kpc-scale gas dynamics to the black hole’s sphere of influence. This mechanism, consistent with simulation predictions, may represent a key contributor to SMBH growth in luminous AGNs since cosmic noon
HIV-phyloTSI: subtype-independent estimation of time since HIV-1 infection for cross-sectional measures of population incidence using deep sequence data
No full textInternational audienceBackgroundEstimating the time since HIV infection (TSI) at population level is essential for tracking changes in the global HIV epidemic. Most methods for determining TSI give a binary classification of infections as recent or non-recent within a window of several months, and cannot assess the cumulative impact of an intervention.ResultsWe developed a Random Forest Regression model, HIV-phyloTSI, which combines measures of within-host diversity and divergence to generate continuous TSI estimates directly from viral deep-sequencing data, with no need for additional variables. HIV-phyloTSI provides a continuous measure of TSI up to 9 years, with a mean absolute error of less than 12 months overall and less than 5 months for infections with a TSI of up to a year. It performs equally well for all major HIV subtypes based on data from African and European cohorts.ConclusionsWe demonstrate how HIV-phyloTSI can be used for incidence estimates on a population lev
Müllerian Mimicry in Neotropical Butterflies: One Mimicry Ring to Bring Them All and in the Jungle Bind Them
No full textInternational audienceABSTRACT Aim Uncovering the effects of Müllerian mimetic interactions on the evolution of species niches and geographic distributions at a continental scale. Location Neotropics and part of Nearctic. Time Period 19th century to present, with most data collected within the last 30 years. Major Taxa Studied Heliconiini (Heliconiinae) and Ithomiini (Danainae) butterfly tribes. Methods We leveraged a dataset of 67,563 geolocalized occurrences from fieldwork observations and museum collections to map broad‐scale biodiversity patterns of heliconiine butterflies. We tested for congruences and disparities with known Ithomiini biodiversity patterns, a group from which they diverged 86.5 My ago, yet share numerous warning wing colour patterns. We used phylogenetic comparative analyses to test for both the spatial co‐occurrence of species with similar aposematic wing patterns and the convergence of their climatic niche within and between tribes. Results Both tribes exhibit wide overlap in biodiversity hotspots across the Neotropics, including a high prevalence of rare species and mimetic patterns in the tropical Andes. Ithomiine species dominate Andean communities, while the Amazon basin hosts a higher relative richness of heliconiines. Phenotypically similar species within and between tribes share climatic niches as a result of selection favouring both co‐occurrence of look‐alike species and convergence of warning signals within local communities. Main Conclusions We documented continental‐scale spatial and evolutionary associations among species sharing warning signals both within and between tribes separated by 86.5 My of independent evolutionary history. Our results provide empirical evidence for the pervasive effects of mutualistic interactions on biodiversity patterns. Critically, they also emphasise the vulnerability of mimetic communities, bound together by positive interactions, to disassembly induced by climate change
Protecting collective qubits from non-Markovian dephasing
No full textInternational audienceIn quantum technologies, qubits encoded as collective atomic or solid-state excitations present important practical advantages, such as strong directional coupling to light. Unfortunately, they are affected by inhomogeneities between the emitters, which make them decay into dark states. In most cases, this process is non-Markovian. Through a simple formalism, we unveil a regime where this decay is suppressed by a combination of driving and non-Markovianity. We experimentally demonstrate this "driving protection" using a Rydberg superatom, making its coherent Rabi oscillations last about 14 times longer than the free lifetime of the collective qubit
Addressing Bottlenecks to Achieve High-Energy Sodium-Ion Cells Using Tin Anodes or Anode-Free
No full textInternational audienceSodium-ion batteries (NIBs), as a complementary energy storage device for Li-ion batteries, are swiftly making their way into high-power applications market. However, further progress in NIBs requires high energy density. This necessitates shifting from the commonly used hard carbon (HC) anodes to alloy anodes such as Bi/Sn/Sb, etc., while overcoming the problems these materials pose with regard to volume changes and interfacial reactivity. This article focuses on issues related to the chemistry of Na3V2(PO4)2F3 (NVPF)|Sn-HC based cells using 1M NaPF6 in diglyme as electrolyte and proposes solutions. Through operando, ex-situ, and post-mortem (electro)chemical characterizations, we demonstrate that glyme electrolytes remain stable under reduction. However, their low oxidative stability gives rise to parasitic species that interfere with and poison the Sn-HC electrode. This results in poor cycling stability, preventing their use in Naion cells. To mitigate this problem, we propose various solutions, such as (i) using a low-voltage cathode, (ii) coating Sn with a protective layer, and (iii) introducing chemical traps such as Nametal, Na15Sn4, or NaxC between the separators. Of all these solutions, the traps are the most effective, completely suppressing cross-talk poisoning, enabling 100% capacity retention of NVPF|Sn-HC cells over 200 cycles at C/5. Furthermore, we demonstrate that this concept can be extended to anode-free configurations, achieving 91% capacity retention after 80 cycles at C/10. This presents a practical design principle for Na-ion cells with energy densities approaching those of Li-ion systems, and can be adapted to other chemistries susceptible to cross-talk poisoning
Kinesin-1 coordinates cross-talk between microtubule and actin cytoskeletons during dendritic cell migration
No full textInternational audienceDendritic cells (DCs) are professional antigen (Ag)-presenting cells that excel in initiating adaptive immune responses by continuously scanning peripheral tissues for Ags. To facilitate efficient DC migration, constant cross-talk between actin and microtubules is required to coordinate cytoskeletal networks and actomyosin contractility, but the related mechanisms have not been extensively characterized. We show that mouse DCs lacking Kif5b (the heavy chain of kinesin-1) exhibit a major impairment in cell migration in vivo and in vitro. Mechanistically, kinesin-1 coordinates cytoskeletal cross-talk between actin and microtubules during DC migration by modulating negatively RhoA activity through its interaction with GEF-H1, thereby limiting GEF-H1's availability in the cytosol. The same mechanism operates in human primary monocyte-derived DCs and regulates efficient migration in a confined environment. Thus, our results highlight kinesin-1 as a key regulator of DC migration, through its coordinated control of cytoskeletal dynamics
Dominique Pieri : Nouvelles productions d'amphores de Syrie du Nord aux époques protobyzantine et omeyyade
No full textReference bibliographique du document traduit:D. Pieri. Nouvelles productions d'amphores de Syrie du Nord aux époques protobyzantine et omeyyade. Travaux et mémoires, Collège de France, Centre de recherche d'histoire et civilisation de Byzance, 2005, 15, pp.583-596.G. Tate, « Les relations villes-campagnes dans le Nord de la Syrie entre le IVe et le VIe siècle », Topoi. Orient-Occident suppl. 5, 2004, p. 311-318