ENS - Départment de biologie

Benoît BOULOUDI Pidd1 is a p73 regulator involved in neuronal survival and choroid plexus morphogenesis

Patricia Mangeny — 2024-12-17T14:08:37Z

14h

La soutenance de thèse de Benoît BOULOUDI (IBENS, Equipe SPASSKY) aura lieu dans la salle Favard, IBENS 46 rue d'Ulm 75005 Paris

Brain multiciliated cells and medial Cajal-Retzius cells are specified by the GEMC1 gene.In addition to its functions in multicilia development, GEMC1 was reported to induce p53-related DNA damage and stress response. Here, we show that Pidd1, a GEMC1-downstream stress response gene, is essential for choroid plexus morphogenesis and survival of medial Cajal-Retzius cells. Inactivation of the Caspase-2-PIDDosome protein complex leads to premature apoptosis of Cajal-Retzius cells, causing transient cortical disorganizations and long-lasting behavioural disorders. Mutant mice exhibit ventricular enlargement due to an abnormal choroid plexus growth. Pidd1 regulates the balance of Trp73 isoforms, contributing to choroid plexus development and Cajal-Retzius cell survival.Thus, our study clarifies the underlying mechanisms behind intellectual deficiencies and lissencephaly in patients with Casp2- PIDDosome mutations.

Elie DANZIGER (Un)bounded Ecologies - Making Biospheric Knowledge through the Pragmatics of Sustenance

Patricia Mangeny — 2024-12-17T13:00:00Z

14h
La soutenance de thèse d'Elie DANZIGER (EHESS-LAS & IBENS EEM) aura lieu à l'Institut des Civilisations du Collège de France, 52 rue du Cardinal Lemoine, 75005 Paris

- 2024 / Soutenance de thèse

Nicolas BIERNE Coadapted Genomes and the Genetic Architecture of Species Barriers

Patricia Mangeny — 2024-12-13T11:00:00Z

12h

Le séminaire de Nicolas BIERNE (Université de Montpellier) aura lieu dans la salle Favard, IBENS 46 rue d'Ulm 75005 Paris

Abstract : The genetics of speciation is often underpinned by relatively simple genetic determinisms, such as pairwise genetic incompatibilities, which form the conceptual basis for barrier loci. Barrier loci restrict gene flow between the genomes of diverging species, both genome-wide and more intensively within specific chromosomal regions surrounding them. Barrier loci are traditionally identified through three approaches : (i) mapping chromosomal islands of divergence across hybrid zones, (ii) mapping segregation distortions in hybrid crosses, and (iii) mapping ancestry outliers in admixed populations. In the marine mussels Mytilus edulis and M. galloprovincialis, we applied all three approaches. While islands of divergence were detected between these two species, which diverged approximately 2 million years ago, the latter two methods yielded inconclusive results. In order to reconcile these observations, we developed a simple multigenic fitness landscape model. The model predicts that, in a novel environment where parental species are maladapted, an admixed population can rapidly achieve higher fitness than either parent by combining advantageous parental mutations in recombined mosaic genomes. Notably, this result does not contradict the persistence of a strong barrier to gene flow between parental species or the resistance of genomic islands to secondary introgression. Our model therfore explains the absence of ancestry outliers in a newly admixed lineage of mussels adapted to a human-altered environment. Furthermore, the model's high-dimensional epistasis predicts that strong selection against an introgressed mutation does not necessarily result in pronounced segregation distortions in a uniformly admixed F2 hybrid background. This approach introduces a genome-wide alternative to the ancestry outlier framework and provides insights into the genetic mechanisms underlying hybrid fitness in changing environments.

Michella KHOURY DAMAA Characterisation of a new cell cycle variant used for multiciliated cells' differentiation

Patricia Mangeny — 2024-12-06T13:00:00Z

14h
La soutenance de thèse de Michella KHOURY DAMAA (Cilia Biology and Neurogenesis - Nathalie SPASSKY's team) aura lieu dans la salle Favard, IBENS 46 rue d'Ulm 75005 Paris

- 2024 / Soutenance de thèse

Damien COUDREUSE Long-term adaptation : when evolution meets cell size

Patricia Mangeny — 2024-12-06T10:00:00Z

11h à 12h30

Le séminaire de Damien COUDREUSE (Institut de Biochimie et Génétique Cellulaires (IBGC), Bordeaux) aura lieu dans la salle Favard, IBENS 46 rue d'Ulm 75005 Paris

Cell volume is a fundamental and highly controlled phenotypic trait that modulates virtually all aspects of the biology of living cells, from their internal biochemistry to their relationship with the environment. Remarkably, cell volume can vary by several orders of magnitude between species, and even within a given species, distinct populations that have evolved in different geographical niches display a broad range of cell volumes. However, while the mechanisms that sustain short-term cell size homeostasis have been the subject of intense investigation, the fascinating interplay between cell size and evolution has largely remained unexplored. I will share our unpublished study that aimed at unravelling the role of cell volume in long-term adaptation. Taking advantage of state-of-the-art experimental evolution approaches using fission yeast as a model, we probed whether and how the initial size of a cell may delineate its evolutionary trajectory at the phenotypic, genetic and mechanistic levels.

Pierre VANDERHAEGHEN Mechanisms linking human brain development, evolution, and (dys)function

Patricia Mangeny — 2024-12-02T10:00:00Z

11h à 12h30
Le séminaire de Pierre VANDERHAEGHEN (VIB Center for Brain & Disease Research, Leuven, Belgium) aura lieu dans la salle Favard, IBENS 46 rue d'Ulm 75005 Paris

- 2024 / Séminaire de l'IBENS

Ana BOSKOVIC Epigenetic control of mammalian embryonic genome activation (EGA)

Patricia Mangeny — 2024-11-25T10:00:00Z

11h à 12h30

Le séminaire d'Ana BOSKOVIC (EMBL, Rome, Italie) aura lieu dans la salle Favard, IBENS 46 rue d'Ulm 75005 Paris

Embryonic genome activation (EGA) is a conserved and essential phenomenon during early development, ensuring the transition of maternal to embryonic control of embryogenesis and propagation of the species. Molecularly, it represents a unique process characterized by an OFF/ON switch in transcriptional activity, unlike transitions between active but distinct transcriptional programs during differentiation and in disease contexts. As all DNA-templated processes, EGA is concomitantly influenced by various gene-regulatory mechanisms, ranging from chromatin structure and composition, chemical modifications of the chromatin polymer, availability and levels of transcriptional factors and accessibility of cis-regulatory regions. We aim to quantitatively dissect the relative contribution of these mechanisms using the mouse embryo as a model. Recently, we established a highly robust and precise in vitro embryo generation system, allowing for temporally precise characterization of the various molecular and -omics (transcriptomic, epigenomic) profile changes during EGA, in ultralow-input samples. With this system in hand, we are currently dissecting the functional hierarchy of epigenetic mechanisms active during EGA, starting from chromatin modifications and chromatin accessibility changes. Our work should ultimately lead to a precise understanding of the regulatory principles governing mammalian EGA at homeostasis, and under environmental or endogenous challenges.

Clément GILBERT Horizontal transfer of transposable elements in animals

Patricia Mangeny — 2024-11-15T11:00:00Z

12h

Le séminaire de Clément GILBERT (Université Paris-Saclay) aura lieu dans la salle Favard, IBENS 46 rue d'Ulm 75005 Paris

Horizontal transfer of genetic material (HT) is the passage of DNA between organisms through means other than reproduction. HT is widespread in prokaryotes and is also being increasingly reported in unicellular eukaryotes. In multicellular eukaryotes, most known cases of HT involve transposable elements (TEs), which are pieces of DNA capable of moving from one locus to another in a given genome, often duplicating themselves in the process. Our recent work deals with determining the biotic and abiotic factors that may foster HT of TEs, as well as with deciphering the mechanisms and vectors involved in these transfers between insect species. Here I will summarize several studies in which we quantify HT of TEs among dozens of animal genomes and I will show that two types of free circulating viruses (baculoviruses and iridoviruses) as well as domesticated viruses of parasitoid wasps (polydnaviruses) show strong potential for acting as vectors of HT among insects.

Thomas DERRIEN et Edouard CADIEU Advancing genome annotation with long-read RNA sequencing : Insights from the IGDRion Facility

Patricia Mangeny — 2024-11-15T09:30:00Z

10h30
Le séminaire de Thomas DERRIEN et Edouard CADIEU (Plateforme IGDRion, Institut de Génétique & Développement de Rennes) aura lieu dans la salle Favard, IBENS 46 rue d'Ulm 75005 Paris
Organisatrices :
Sophie Lemoine (Plateforme Génomique) et Alexandra Louis (Plateforme Bioinformatique)

- 2024 / Séminaire de l'IBENS

Biophysics, molecular organization & regulation of postsynaptic domains

Patricia Mangeny — 2024-11-14T12:00:00Z

14 & 15 November 2024

Invited speakers : Jean-Louis Bessereau, Dilja Krueger-Burg, Mathieu Letellier, Hans Maric, Marianne Renner & Tatjana Tchumatchenko

Bringing together researchers from various disciplines investigating the biology and biophysics of postsynaptic domains, the aim is to expand on the current knowledge about excitatory and inhibitory synapse size and its regulation, and to discuss future avenues for an improved quantitative understanding of the underlying mechanisms.

For the program and registration (free but mandatory, poster presentations are welcome), please see here : https://psddynamics.sciencesconf.org/

Organisation : Jonas Ranft, Vincent Hakim, Christian Specht