Biology subjects

Pinot, M.

Publications and source records attributed to Pinot, M..

6 recordsLinked to original sources

bioRxiv2022

Cell-intrinsic and -extrinsic functions of the ESCRT-III component Shrub in cytokinetic abscission of Drosophila Sensory Organ precursor

While the molecular mechanisms underlying the abscission of isolated cells are largely decrypted, those of fast-cycling, epithelial progenitors surrounded by epidermal cells (ECs) connected by junctions remain largely unexplored. Here, we investigated the remodeling of the permeability barrier ensured by septate junctions (SJs) during cytokinesis of Drosophila sensory organ precursor (SOP). We report that SOP cytokinesis involves the coordinated polarized assembly and remodeling of SJs in the dividing cell and its neighbors, which remained connected via membrane protrusions pointing toward the SOP midbody. SJs assembly and midbody basal displacement occur more rapidly in SOP than in ECs, leading to a faster disentanglement of the protrusions that precedes midbody release. As reported in isolated cells, the endosomal sorting complex required for transport-III component Shrub/CHMP4B is recruited at the midbody and cell-autonomously regulates abscission. In addition, we found that Shrub is recruited to membrane protrusions, is required for SJ integrity, and that alteration of SJ integrity leads to premature abscission. Our study uncovers cell-intrinsic and -extrinsic functions of Shrub in epithelial abscission to support the coordination of permeability barrier maintenance and abscission in SOPs.

developmental biology↗

bioRxiv2021

Bazooka/Par3 cooperates with Sanpodo for the assembly of Notch signaling clusters following asymmetric division of Drosophila sensory organ precursor cells

In multiple cell lineages, Delta-Notch signaling regulates cell fate decisions owing to unidirectional signaling between daughter cells. In Drosophila pupal sensory organ lineage, Notch regulates pIIa/pIIb fate decision at cytokinesis. Notch and Delta that localize apically and basally at the pIIa-pIIb interface, are expressed at low levels and their residence time at the plasma membrane is in the order of the minute. How Delta can effectively interact with Notch to trigger signaling from a large plasma membrane remains poorly understood. Here, we report that the signaling interface possesses a unique apicobasal polarity with Par3/Bazooka localizing in the form of nano-clusters at the apical and basal level. Notch is preferentially targeted to the pIIa-pIIb interface where it co-clusters with Bazooka and the Notch cofactor Sanpodo. Clusters whose assembly relies on Bazooka and Sanpodo activities, are also positive for Neuralized, the E3 ligase required for Delta-activity. We propose that the nano-clusters act as snap buttons at the new pIIa-pIIb interface to allow efficient intra-lineage signaling.

developmental biology↗

bioRxiv2020

Clathrin adaptor AP-1 and Stratum act in parallel pathways to control Notch activation in Drosophila Sensory Organ Precursor Cells

Drosophila sensory organ precursors divide asymmetrically to generate pIIa/pIIb cells whose identity relies on the differential activation of Notch at cytokinesis. While Notch is present apically and basally relative to the midbody at the pIIa-pIIb interface, only the basal pool of Notch is reported to contribute to Notch activation in the pIIa cell. Correct intra-lineage signalling requires appropriate apico-basal targeting of Notch, its ligand Delta and its trafficking partner Sanpodo. We previously reported that AP-1 and Stratum regulate the intracellular trafficking of Notch and Sanpodo from the trans-Golgi network to the basolateral membrane. Loss of AP-1 or Stratum caused mild Notch gain-of-function phenotypes. Here, we report that the concomitant loss of AP-1 and Stratum results in a much more penetrant Notch gain-of-function phenotype indicating that AP-1 and Strat control two parallel pathways. While unequal partitioning of cell fate determinants and cell polarity were unaffected, Numb-mediated symmetry breaking is impaired. We further observed increased amounts of signaling competent Notch as well as Delta and Sanpodo at the apical pIIa-pIIb interface and the loss of the basal pool of Notch. We propose that AP-1 and Stratum operate in two parallel pathways to ensure the correct apico-basal localization of Notch controlling where receptor activation takes place.

developmental biology↗

bioRxiv2020

Super-resolved live-cell imaging using Random Illumination Microscopy

Super-resolution fluorescence microscopy has been instrumental to progress in biology. Yet, the photo-induced toxicity, the loss of resolution into scattering samples or the complexity of the experimental setups curtail its general use for functional cell imaging. Here, we describe a new technology for tissue imaging reaching a 114nm/8Hz resolution at 30 {micro}m depth. Random Illumination Microscopy (RIM) consists in shining the sample with uncontrolled speckles and extracting a high-fidelity super-resolved image from the variance of the data using a reconstruction scheme accounting for the spatial correlation of the illuminations. Super-resolution unaffected by optical aberrations, undetectable phototoxicity, fast image acquisition rate and ease of use, altogether, make RIM ideally suited for functional live cell imaging in situ. RIM ability to image molecular and cellular processes in three dimensions and at high resolution is demonstrated in a wide range of biological situations such as the motion of Myosin II minifilaments in Drosophila.

bioengineering↗

bioRxiv2018

Feedback between membrane tension, lipid shape and curvature in the formation of packing defects

Lipid packing defects favor the binding of proteins to cellular membranes by creating spaces between lipid head groups that allow the insertion of amphipathic helices or lipid modifications. The density of packing defects in a lipid membrane is well known to increase with membrane curvature and in the presence of conical-shaped lipids. In contrast, the role of membrane tension in the formation of lipid packing defects has been poorly investigated. Here we use a combination of numerical simulations and experiments to measure the effect of membrane tension on the density of lipid packing defects. We first monitor the binding of ALPS (amphipathic lipid packing sensor) to giant unilamellar vesicles and observe a striking periodic binding of ALPS that we attribute to osmotically-induced membrane tension and transient membrane pore formation. Using micropipette aspiration experiments, we show that a high membrane tension induces a reversible increase in the density of lipid packing defects. We next focus on packing defects induced by lipid shape and show that conical lipids generate packing defects similar to that induced by membrane tension and enhance membrane deformation due to the insertion of the ALPS helix. Both cyclic ALPS binding and the cooperative effect of ALPS binding and conical lipids on membrane deformation result from an interplay between helix insertion and lipid packing defects created by membrane tension, conical lipids and/or membrane curvature. We propose that feedback mechanisms involving membrane tension, lipid shape and membrane curvature play a crucial role in membrane deformation and intracellular transport events.

biophysics↗

bioRxiv2017

Coordinated morphogenesis through tension-induced planar polarity

Tissues from different developmental origins must interact to achieve coordinated morphogenesis at the level of a whole organism. C. elegans embryonic elongation is controlled by actomyosin dynamics which trigger cell shape changes in the epidermis and by muscle contractions, but how the two processes are coordinated is not known. We found that a tissue-wide tension generated by muscle contractions and relayed by tendon-like hemidesmosomes in the dorso-ventral epidermis is required to establish a planar polarity of the apical PAR module in the lateral epidermis. This planar polarized PAR module then controls actin planar organization, thus determining the orientation of cell shape changes and the elongation axis of the whole embryo. This trans-tissular mechanotransduction pathway thus contributes to coordinate the morphogenesis of three embryonic tissues.

developmental biology↗