Mars 2022
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Mardi 01/03/2022 Salle des Thèses CRC & Visio Séminaire Externe |
“ Neuroinvasion by HTLV and ZIKV: how blood-borne viruses cross the blood brain barrier “ | |
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Dr. Philippe AFONSO (Unité d’Epidémiologie et Physiopathologie des Virus Oncogènes, Institut Pasteur, Université de Paris, CNRS)
Hote : François-Loïc COSSET
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Vendredi 04/03/2022 Salle des Thèses CRC Séminaire Externe |
« Visualizing coordination between chromatin structure, dynamics, and transcription in space and time » | |
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Haitham SHABAN (Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland)
Contact Geneviève Forel
The spatio-temporal organization of chromatin in the eukaryotic cell nucleus is of vital importance for transcription, DNA replication and genome maintenance. Each of these activities is tightly regulated in both time and space. The eukaryotic genome is hierarchically structured yet highly dynamic. Regulating transcription in this environment demands a high level of coordination to permit many proteins to interact with chromatin fiber at appropriate sites in a timely manner. In this seminar, I will introduce our recent quantitative imaging techniques for the visualization of chromatin, transcription factors, and RNA polymerase II dynamics at genome-scale with nanometer resolution in living cells. Also, I will discuss how advances of these techniques overcome caveats of sequencing-based methods (Hi-C and related) by enabling direct visualization of chromatin in space and time at high resolution. I will also discuss the contribution of our results in deciphering the principles underlying this coordination within the crowded nuclear space in living cells.
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Lundi 07/03/2022 Salle des Thèses CRC Séminaire Externe |
" Development and evolution of neuronal diversity in the insect optic lobes " | |
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Nikos KONSTANTINIDES (Institut Jacques Monod, Paris)
Hôte: Camille Guillermin
The brain consists of thousands of neuronal types that are generated by stem cells that produce different neuronal types as they age. In Drosophila, this temporal patterning is driven by the successive expression of temporal transcription factors (tTFs). We used single-cell mRNA sequencing to identify the complete series of tTFs that specify most Drosophila optic lobe neurons. We verified that tTFs regulate the progression of the series by activating the next tTFs and repressing the previous one(s), but also identified more complex regulations. Moreover, we established the temporal window of origin and birth order of each neuronal type in the medulla and provide evidence that these tTFs are sufficient to explain the generation of all the neuronal diversity in this brain region. Finally, we describe the first steps of neuronal differentiation. We find that terminal differentiation genes, such as neurotransmitter-related genes, are present as transcripts, but not as proteins, in immature larval neurons. This comprehensive analysis of a temporal series of transcription factors offers a proof-of-principle for the use of single-cell mRNA sequencing for the comparison of temporal patterning across phyla that can lead to an understanding of how neurodevelopmental mechanisms evolve to generate diverse neuronal types.
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Lundi 21/03/2022 11H00 Salle Condorcet Séminaire Externe |
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Sebastian WOLF (University of Tübingen, ZMBP)
Host: Charlotte Kirchhelle
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Mardi 22/03/2022 11H00 Salle des Thèses CRC & Visio Séminaire externe |
“ Architecture of retroviral capsid explored by cryo-electron tomography and subtomogram averaging “ | |
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Dr. Martin OBR (Institute of Science and Technology Austria, Klosterneuburg, Austria)
Hôte : François-Loïc COSSET
Family Retroviridae comprises viruses infecting wide range of hosts, including humans (Human immunodeficiency virus; Human T-lymphotropic virus). The life cycle of retroviruses contains several unique steps, one of which is proteolytic maturation. During this process, the immature virus particle is converted to mature. Particularly, the precursor protein Gag is cleaved to yield Capsid protein, which triggers large-scale structural reorganization of the virus particle. Capsid protein, and the corresponding part of Gag, form and maintain the protein lattice, which constitutes the mature and immature capsid, respectively.
Retroviral lattice is a challenging object for structural biology, due to the absence of global symmetry. The classic techniques, such as X-ray crystallography, are thus of limited applicability. On the other hand, the versatility of cryo-electron tomography and subtomogram averaging allows observing ultrastructure of the retrovirus particle, and structure determination of its building blocks. |
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Jeudi 24/03/2022 13H00 Visio Séminaire externe |
« Selective clonal persistence of HTLV-1 in vivo: radial chromatin organization, integration site and host transcription » | |
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Dr. Anat MELAMED (IImperial College London, UK)
Hôte : Jocelyn Turpin
The human retroviruses HTLV-1 and HIV-1 persist in vivo, despite the host immune response and antiretroviral therapy, as a reservoir of latently infected T-cell clones, each clone defined by the unique genomic integration site (IS) of the single-copy HTLV-1 provirus. It is poorly understood what determines which clones survive in the reservoir and which are lost. To test the hypothesis that HTLV-1 persistence in vivo depends on the intranuclear position of the provirus, we compared the genomic location of >230,000 IS of HTLV-1 from in vitro infection with that of >160,000 IS identified in peripheral blood mononuclear cells of individuals persistently infected with HTLV-1.
In this talk, I shall discuss three factors we have identified as associated with clonal survival of HTLV-1, which together explained >40% of the observed variance in clone survival of HTLV-1 in vivo. Lien zoom : https://univ-lyon1-fr.zoom.us/j/81243070468 |
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Vendredi 25/03/2022 15H00 Salle des Thèses CRC Séminaire externe |
« Genome Organization through Phase Separation: Random yet Precise » | |
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Bin ZHANG (Massachusetts Institute of Technology - MIT)
Contact : Daniel JOST
The three-dimensional genome organization plays an essential role in all DNA-templated processes, including gene transcription, gene regulation, DNA replication, etc. Coarse-grained models parameterized to reproduce experimental data via the maximum entropy optimization algorithm serve as effective means to study genome organization at various length scales. They have provided insight into the principles of whole-genome organization and enabled de novo predictions of chromosome structures from epigenetic modifications. In addition, they provided insight into the critical role of the chromatin network in stabilizing multiple liquid droplets. Applications of these models at a near-atomic resolution further revealed physicochemical interactions that drive the phase separation of disordered proteins and dictate chromatin stability in situ.
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Mardi 29/03/2022 11H00 Salle des Thèses CRC & Visio Séminaire externe
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“ Rift Valley fever virus and its fabulous NSs protein: a model to study amyloid aggregation and functions? “ | |
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Dr. Pierre-Yves LOZACH (UMR 754 "Infections Virales et Pathologie Comparée, Lyon)
Hôte : François-Loïc COSSET
Rift Valley fever is a mosquito-borne viral zoonosis that was first discovered in the Great Rift Valley, Kenya, in 1930. Rift Valley fever virus (RVFV) primarily infects domestic animals and humans, with clinical outcomes ranging from self-limiting febrile illness to acute hepatitis and encephalitis. The virus left Africa a few decades ago, and there is a risk of introduction into southern Europe and Asia. In this seminar, I will introduce RVFV and address the capacity of its virulence factor, the nonstructural protein NSs, to form amyloid-like fibrils based on analysis by state-of-the-art microscopy techniques in fixed and living cells and in animals. I will then discuss the implications for (i) the NSs biological function, (ii) the ability of the virus to evade innate immunity, and (iii) RVFV virulence and neurotoxicity.
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