ENS - Départment de biologie

Eco-evolutionary responses of the microbial loop to surface ocean warming and consequences for primary production

Frédérique Godfroid — 2022-01-10T09:15:58Z

Abstract

Predicting the response of ocean primary production to climate warming is a major challenge. One key control of primary production is the microbial loop driven by heterotrophic bacteria, yet how warming alters the microbial loop and its function is poorly understood. Here we develop an eco-evolutionary model to predict the physiological response and adaptation through selection of bacterial populations in the microbial loop and how this will impact ecosystem function such as primary production. We find that the ecophysiological response of primary production to warming is driven by a decrease in regenerated production which depends on nutrient availability. In nutrient-poor environments, the loss of regenerated production to warming is due to decreasing microbial loop activity. However, this ecophysiological response can be opposed or even reversed by bacterial adaptation through selection, especially in cold environments : heterotrophic bacteria with lower bacterial growth efficiency are selected, which strengthens the “link” behavior of the microbial loop, increasing both new and regenerated production. In cold and rich environments such as the Arctic Ocean, the effect of bacterial adaptation on primary production exceeds the ecophysiological response. Accounting for bacterial adaptation through selection is thus critically needed to improve models and projections of the ocean primary production in a warming world.

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ISME Journal (2021) doi.org/10.1038/s41396-021-01166-8

NMDARs in granule cells contribute to parallel fiber-Purkinje cell synaptic plasticity and motor learning

Frédérique Godfroid — 2022-01-03T17:08:49Z

Authors :
Martijn Schonewille, Allison E Girasole, Philippe Rostaing, Caroline Mailhes-Hamon, Annick Ayon, Alexandra B Nelson, Antoine Triller, Mariano Casado, Chris I De Zeeuw, Guy Bouvier

Abstract

Long-term synaptic plasticity is believed to be the cellular substrate of learning and memory. Synaptic plasticity rules are defined by the specific complement of receptors at the synapse and the associated downstream signaling mechanisms. In young rodents, at the cerebellar synapse between granule cells (GC) and Purkinje cells (PC), bidirectional plasticity is shaped by the balance between transcellular nitric oxide (NO) driven by presynaptic N-methyl-D-aspartate receptor (NMDAR) activation and postsynaptic calcium dynamics. However, the role and the location of NMDAR activation in these pathways is still debated in mature animals. Here, we show in adult rodents that NMDARs are present and functional in presynaptic terminals where their activation triggers NO signaling. In addition, we find that selective genetic deletion of presynaptic, but not postsynaptic, NMDARs prevents synaptic plasticity at parallel fiber-PC (PF-PC) synapses. Consistent with this finding, the selective deletion of GC NMDARs affects adaptation of the vestibulo-ocular reflex. Thus, NMDARs presynaptic to PCs are required for bidirectional synaptic plasticity and cerebellar motor learning.

Keywords : Purkinje cells ; cerebellum ; motor learning ; nitric oxide ; pre-NMDARs.

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Proc Natl Acad Sci USA. 2021 Sep 14 ;118(37) doi : 10.1073/pnas.2102635118

A medullary centre for lapping in mice

Frédérique Godfroid — 2021-12-21T16:35:47Z

Authors :
Bowen Dempsey, Selvee Sungeelee, Phillip Bokiniec, Zoubida Chettouh, Séverine Diem, Sandra Autran, Evan R. Harrell, James F. A. Poulet, Carmen Birchmeier, Harry Carey, Auguste Genovesio, Simon McMullan, Christo Goridis, Gilles Fortin^# & Jean-François Brunet^#
^# co-senior author

Abstract

It has long been known that orofacial movements for feeding can be triggered, coordinated, and often rhythmically organized at the level of the brainstem, without input from higher centers. We uncover two nuclei that can organize the movements for ingesting fluids in mice. These neuronal groups, IRt^Phox2b and Peri5^Atoh1, are marked by expression of the pan-autonomic homeobox gene Phox2b and are located, respectively, in the intermediate reticular formation of the medulla and around the motor nucleus of the trigeminal nerve. They are premotor to all jaw-opening and tongue muscles. Stimulation of either, in awake animals, opens the jaw, while IRt^Phox2b alone also protracts the tongue. Moreover, stationary stimulation of IRt^Phox2b entrains a rhythmic alternation of tongue protraction and retraction, synchronized with jaw opening and closing, that mimics lapping. Finally, fiber photometric recordings show that IRt^Phox2b is active during volitional lapping. Our study identifies one of the subcortical nuclei underpinning a stereotyped feeding behavior.

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Nat Commun. 2021 Nov 2 ;12(1):6307. doi : 10.1038/s41467-021-26275-y.

Cécile Charrier, lauréate du Prix Irène Joliot-Curie 2021 "Jeune Femme scientifique"

Frédérique Godfroid — 2021-11-24T20:58:17Z

20ème édition du prix Irène Joliot-Curie

Créé en 2001 par le ministère en charge de la Recherche, le Prix Irène Joliot-Curie est destiné à promouvoir la place des femmes dans la recherche et la technologie en France. A cette fin, il met en lumière les carrières exemplaires de femmes de sciences qui allient excellence et dynamisme. Depuis 2011, le ministère a confié à l'Académie des sciences et l'Académie des technologies la charge de constituer le jury, présidé par Catherine Cesarsky, Haut conseiller scientifique au CEA.
En 20 années d'existence, le Prix Irène Joliot-Curie a récompensé plus de 60 femmes scientifiques aux carrières exceptionnelles dans toutes les disciplines scientifiques.

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"Félicitations à Cécile Charrier, lauréate de la 20e édition du Prix Irène Joliot-Curie"

Dossier de presse Prix Irene Joliot-Curie

Global drivers of eukaryotic plankton biogeography in the sunlit ocean

Frédérique Godfroid — 2021-11-09T10:21:26Z

Le plancton eucaryote est une composante essentielle et extrêmement diversifiée des écosystèmes marins, dont la distribution géographique (la « biogéographie ») reste pourtant mal connue. Dans une étude parue fin octobre dans la revue Science, une équipe de chercheurs de l'Institut de Biologie de l'École Normale Supérieure de Paris (IBENS, CNRS / ENS Paris / Inserm) et de Naples (Station Zoologique Anton Dohrn) ont étudié sa biogéographie à l'échelle mondiale à partir de données ADN récoltées par la goélette d'exploration océanique Tara. A l'aide d'un modèle probabiliste, ils ont établi que la biogéographie variait considérablement d'un groupe planctonique à l'autre, et que ces variations suivaient deux axes principaux : d'une part, les groupes les plus diversifiés sont davantage spatialement structurés ; d'autre part, les zooplanctons de grande taille (plusieurs millimètres) sont structurés par bassin océanique et à grande échelle spatiale, principalement sous l'influence des courants marins, tandis que les producteurs primaires de petite taille (quelques micromètres) sont structurés par latitude et à plus petite échelle spatiale, du fait d'une sensibilité accrue aux variations environnementales locales.

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Science. Vol 374, Issue 6567, pp. 594-599, 10.1126/science.abb3717

Bayesian analysis of Enceladus's plume data to assess methanogenesis

Frédérique Godfroid — 2021-10-14T16:32:10Z

Abstract

Observations from NASA's Cassini spacecraft established that Saturn's moon Enceladus has an internal liquid ocean. Analysis of a plume of ocean material ejected into space suggests that alkaline hydrothermal vents are present on Enceladus's seafloor. On Earth, such deep-sea vents harbour microbial ecosystems rich in methanogenic archaea. Here we use a Bayesian statistical approach to quantify the probability that methanogenesis (biotic methane production) might explain the escape rates of molecular hydrogen and methane in Enceladus's plume, as measured by Cassini instruments. We find that the observed escape rates (1) cannot be explained solely by the abiotic alteration of the rocky core by serpentinization ; (2) are compatible with the hypothesis of habitable conditions for methanogens ; and (3) score the highest likelihood under the hypothesis of methanogenesis, assuming that the probability of life emerging is high enough. If the probability of life emerging on Enceladus is low, the Cassini measurements are consistent with habitable yet uninhabited hydrothermal vents and point to unknown sources of methane (for example, primordial methane) awaiting discovery by future missions.

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Nature Astronomy (2021) 5, 805-814.

Tempo and mode of morphological evolution are decoupled from latitude in birds

Frédérique Godfroid — 2021-10-06T16:36:23Z

Abstract

The latitudinal diversity gradient is one of the most striking patterns in nature, yet its implications for morphological evolution are poorly understood. In particular, it has been proposed that an increased intensity of species interactions in tropical biota may either promote or constrain trait evolution, but which of these outcomes predominates remains uncertain. Here, we develop tools for fitting phylogenetic models of phenotypic evolution in which the impact of species interactions—namely, competition—can vary across lineages. Deploying these models on a global avian trait dataset to explore differences in trait divergence between tropical and temperate lineages, we find that the effect of latitude on the mode and tempo of morphological evolution is weak and clade- or trait dependent. Our results indicate that species interactions do not disproportionately impact morphological evolution in tropical bird families and question the validity of previously reported patterns of slower trait evolution in the tropics.

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PLoS Biol. 2021 Aug 24 ;19(8):e3001270.

Fast and Accurate Estimation of Species-Specific Diversification Rates Using Data Augmentation

Frédérique Godfroid — 2021-10-06T16:35:51Z

Abstract

Diversification rates vary across species as a response to various factors, including environmental conditions and species-specific features. Phylogenetic models that allow accounting for and quantifying this heterogeneity in diversification rates have proven particularly useful for understanding clades diversification. Recently, we introduced the cladogenetic diversification rate shift model, which allows inferring multiple rate changes of small magnitude across lineages. Here, we present a new inference technique for this model that considerably reduces computation time through the use of data augmentation and provide an implementation of this method in Julia. In addition to drastically reducing computation time, this new inference approach provides a posterior distribution of the augmented data, that is the tree with extinct and unsampled lineages as well as associated diversification rates. In particular, this allows extracting the distribution through time of both the mean rate and the number of lineages. We assess the statistical performances of our approach using simulations and illustrate its application on the entire bird radiation.[Birth–death model ; data augmentation ; diversification ; macroevolution.]

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Syst Biol. 2021 Jul 6 ;syab055.

Unique properties of dually innervated dendritic spines in pyramidal neurons of the somatosensory cortex uncovered by 3D correlative light and electron microscopy

Frédérique Godfroid — 2021-09-22T20:16:13Z

Abstract

Pyramidal neurons (PNs) are covered by thousands of dendritic spines receiving excitatory synaptic inputs. The ultrastructure of dendritic spines shapes signal compartmentalization, but ultrastructural diversity is rarely taken into account in computational models of synaptic integration. Here, we developed a 3D correlative light–electron microscopy (3D-CLEM) approach allowing the analysis of specific populations of synapses in genetically defined neuronal types in intact brain circuits. We used it to reconstruct segments of basal dendrites of layer 2/3 PNs of adult mouse somatosensory cortex and quantify spine ultrastructural diversity. We found that 10% of spines were dually innervated and 38% of inhibitory synapses localized to spines. Using our morphometric data to constrain a model of synaptic signal compartmentalization, we assessed the impact of spinous versus dendritic shaft inhibition. Our results indicate that spinous inhibition is locally more efficient than shaft inhibition and that it can decouple voltage and calcium signaling, potentially impacting synaptic plasticity.

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PLoS Biol 2021. doi:10.1371/journal.pbio.3001375

GluN2A and GluN2B NMDA receptors use distinct allosteric routes

Frédérique Godfroid — 2021-09-22T19:39:02Z

Abstract

Allostery represents a fundamental mechanism of biological regulation that involves long-range communication between distant protein sites. It also provides a powerful framework for novel therapeutics. NMDA receptors (NMDARs), glutamate-gated ionotropic receptors that play central roles in synapse maturation and plasticity, are prototypical allosteric machines harboring large extracellular N-terminal domains (NTDs) that provide allosteric control of key receptor properties with impact on cognition and behavior. It is commonly thought that GluN2A and GluN2B receptors, the two predominant NMDAR subtypes in the adult brain, share similar allosteric transitions. Here, combining functional and structural interrogation, we reveal that GluN2A and GluN2B receptors utilize different long-distance allosteric mechanisms involving distinct subunit-subunit interfaces and molecular rearrangements. NMDARs have thus evolved multiple levels of subunit-specific allosteric control over their transmembrane ion channel pore. Our results uncover an unsuspected diversity in NMDAR molecular mechanisms with important implications for receptor physiology and precision drug development.
© 2021. The Author(s)

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Nat Commun. 2021 Aug 5 ;12(1):4709. doi : 10.1038/s41467-021-25058-9