Polarité, division et morphogenèse

Publications de l’équipe

Année de publication : 2007

Andrea Leibfried, Yohanns Bellaïche (2007 Jul 27)

Functions of endosomal trafficking in Drosophila epithelial cells.

Current opinion in cell biology : 446-52 En savoir plus
Résumé

The mechanisms underlying endosomal trafficking have been mostly dissected in yeast and mammalian tissue culture cells. Here, we review recent advances in the understanding of the role of endosomal trafficking in Drosophila epithelial cells. We focus on endosomal pathways that control cell polarization, cell growth, cell fate and epithelial cell rearrangement. We expect that mechanistic studies in mammalian cells and functional studies in invertebrates will continue to synergize to provide a comprehensive view of the role of endosomal trafficking in epithelial tissue organization and functions.

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Année de publication : 2006

Maria Balakireva, Carine Rossé, Johanna Langevin, Yu-chen Chien, Michel Gho, Geneviève Gonzy-Treboul, Stéphanie Voegeling-Lemaire, Sandra Aresta, Jean-Antoine Lepesant, Yohanns Bellaiche, Michael White, Jacques Camonis (2006 Sep 25)

The Ral/exocyst effector complex counters c-Jun N-terminal kinase-dependent apoptosis in Drosophila melanogaster.

Molecular and cellular biology : 8953-63 En savoir plus
Résumé

Ral GTPase activity is a crucial cell-autonomous factor supporting tumor initiation and progression. To decipher pathways impacted by Ral, we have generated null and hypomorph alleles of the Drosophila melanogaster Ral gene. Ral null animals were not viable. Reduced Ral expression in cells of the sensory organ lineage had no effect on cell division but led to postmitotic cell-specific apoptosis. Genetic epistasis and immunofluorescence in differentiating sensory organs suggested that Ral activity suppresses c-Jun N-terminal kinase (JNK) activation and induces p38 mitogen-activated protein (MAP) kinase activation. HPK1/GCK-like kinase (HGK), a MAP kinase kinase kinase kinase that can drive JNK activation, was found as an exocyst-associated protein in vivo. The exocyst is a Ral effector, and the epistasis between mutants of Ral and of msn, the fly ortholog of HGK, suggest the functional relevance of an exocyst/HGK interaction. Genetic analysis also showed that the exocyst is required for the execution of Ral function in apoptosis. We conclude that in Drosophila Ral counters apoptotic programs to support cell fate determination by acting as a negative regulator of JNK activity and a positive activator of p38 MAP kinase. We propose that the exocyst complex is Ral executioner in the JNK pathway and that a cascade from Ral to the exocyst to HGK would be a molecular basis of Ral action on JNK.

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Sébastien Courty, Camilla Luccardini, Yohanns Bellaiche, Giovanni Cappello, Maxime Dahan (2006 Jul 13)

Tracking individual kinesin motors in living cells using single quantum-dot imaging.

Nano letters : 1491-5 En savoir plus
Résumé

We report a simple method using semiconductor quantum dots (QDs) to track the motion of intracellular proteins with a high sensitivity. We characterized the in vivo motion of individual QD-tagged kinesin motors in living HeLa cells. Single-molecule measurements provided important parameters of the motor, such as its velocity and processivity, as well as an estimate of the force necessary to carry a QD. Our measurements demonstrate the importance of single-molecule experiments in the investigation of intracellular transport as well as the potential of single quantum-dot imaging for the study of important processes such as cellular trafficking, cell polarization, and division.

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Année de publication : 2005

Nicolas B David, Charlotte A Martin, Marion Segalen, François Rosenfeld, François Schweisguth, Yohanns Bellaïche (2005 Oct 18)

Drosophila Ric-8 regulates Galphai cortical localization to promote Galphai-dependent planar orientation of the mitotic spindle during asymmetric cell division.

Nature cell biology : 1083-90 En savoir plus
Résumé

Localization and activation of heterotrimeric G proteins have a crucial role during asymmetric cell division. The asymmetric division of the Drosophila sensory precursor cell (pl) is polarized along the antero-posterior axis by Frizzled signalling and, during this division, activation of Galphai depends on Partner of Inscuteable (Pins). We establish here that Ric-8, which belongs to a family of guanine nucleotide-exchange factors for Galphai, regulates cortical localization of the subunits Galphai and Gbeta13F. Ric-8, Galphai and Pins are not necessary for the control of the anteroposterior orientation of the mitotic spindle during pl cell division downstream of Frizzled signalling, but they are required for maintainance of the spindle within the plane of the epithelium. On the contrary, Frizzled signalling orients the spindle along the antero-posterior axis but also tilts it along the apico-basal axis. Thus, Frizzled and heterotrimeric G-protein signalling act in opposition to ensure that the spindle aligns both in the plane of the epithelium and along the tissue polarity axis.

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Johanna Langevin, Matthew J Morgan, Jean-Baptiste Sibarita, Sandra Aresta, Mala Murthy, Thomas Schwarz, Jacques Camonis, Yohanns Bellaïche (2005 Oct 15)

Drosophila exocyst components Sec5, Sec6, and Sec15 regulate DE-Cadherin trafficking from recycling endosomes to the plasma membrane.

Developmental cell : 365-76 En savoir plus
Résumé

The E-Cadherin-catenin complex plays a critical role in epithelial cell-cell adhesion, polarization, and morphogenesis. Here, we have analyzed the mechanism of Drosophila E-Cadherin (DE-Cad) localization. Loss of function of the Drosophila exocyst components sec5, sec6, and sec15 in epithelial cells results in DE-Cad accumulation in an enlarged Rab11 recycling endosomal compartment and inhibits DE-Cad delivery to the membrane. Furthermore, Rab11 and Armadillo interact with the exocyst components Sec15 and Sec10, respectively. Our results support a model whereby the exocyst regulates DE-Cadherin trafficking, from recycling endosomes to sites on the epithelial cell membrane where Armadillo is located.

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Johanna Langevin, Roland Le Borgne, François Rosenfeld, Michel Gho, François Schweisguth, Yohanns Bellaïche (2005 May 27)

Lethal giant larvae controls the localization of notch-signaling regulators numb, neuralized, and Sanpodo in Drosophila sensory-organ precursor cells.

Current biology : CB : 955-62 En savoir plus
Résumé

Asymmetric distribution of fate determinants is a fundamental mechanism underlying the acquisition of distinct cell fates during asymmetric division. In Drosophila neuroblasts, the apical DmPar6/DaPKC complex inhibits Lethal giant larvae (Lgl) to promote the basal localization of fate determinants. In contrast, in the sensory precursor (pI) cells that divide asymmetrically with a planar polarity, Lgl inhibits Notch signaling in the anterior pI daughter cell, pIIb, by a yet-unknown mechanism. We show here that Lgl promotes the cortical recruitment of Partner of Numb (Pon) and regulates the asymmetric distribution of the fate determinants Numb and Neuralized during the pI cell division. Analysis of Pon-GFP and Histone2B-mRFP distribution in two-color movies confirmed that Lgl regulates Pon localization. Moreover, posterior DaPKC restricts Lgl function to the anterior cortex at mitosis. Thus, Lgl functions similarly in neuroblasts and in pI cells. We also show that Lgl promotes the acquisition of the pIIb cell fate by inhibiting the plasma membrane localization of Sanpodo and thereby preventing the activation of Notch signaling in the anterior pI daughter cell. Thus, Lgl regulates cell fate by controlling Pon cortical localization, asymmetric localization of Numb and Neuralized, and plasma-membrane localization of Sandopo.

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Année de publication : 2004

Martin P Zeidler, Change Tan, Yohanns Bellaïche, Sara Cherry, Sabine Häder, Urte Gayko, Norbert Perrimon (2004 Jun 9)

Temperature-sensitive control of protein activity by conditionally splicing inteins.

Nature biotechnology : 871-6 En savoir plus
Résumé

Conditional or temperature-sensitive (TS) alleles represent useful tools with which to investigate gene function. Indeed, much of our understanding of yeast has relied on temperature-sensitive mutations which, when available, also provide important insights into other model systems. However, the rarity of temperature-sensitive alleles and difficulty in identifying them has limited their use. Here we describe a system to generate temperature-sensitive alleles based on conditionally active inteins. We have identified temperature-sensitive splicing variants of the yeast Saccharomyces cerevisiae vacuolar ATPase subunit (VMA) intein inserted within Gal4 and transferred these into Gal80. We show that Gal80-intein(TS) is able to efficiently provide temporal regulation of the Gal4/upstream activation sequence (UAS) system in a temperature-dependent manner in Drosophila melanogaster. Given the minimal host requirements necessary for temperature-sensitive intein splicing, this technique has the potential to allow the generation and use of conditionally active inteins in multiple host proteins and model systems, thereby widening the use of temperature-sensitive alleles for functional protein analysis.

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Stéphane Audebert, Christel Navarro, Claire Nourry, Sylvette Chasserot-Golaz, Patrick Lécine, Yohanns Bellaïche, Jean-Luc Dupont, Richard T Premont, Christine Sempéré, Jean-Marc Strub, Alain Van Dorsselaer, Nicolas Vitale, Jean-Paul Borg (2004 Jun 9)

Mammalian Scribble forms a tight complex with the betaPIX exchange factor.

Current biology : CB : 987-95 En savoir plus
Résumé

Drosophila Scribble is implicated in the development of normal synapse structure and epithelial tissues, but it remains unclear how it plays a role and which process it controls. The mammalian homolog of Scribble, hScrib, has a primary structure and subcellular localization similar to that of its fly homolog, but its function remains unknown. Here we have used tandem mass spectrometry to identify major components of the hScrib network. We show that it includes betaPIX (also called Cool-1), a guanine nucleotide exchange factor (GEF), and its partner GIT1 (also called p95-APP1), a GTPase activating protein (GAP). betaPIX directly binds to the hScrib PDZ domains, and the hScrib/betaPIX complex is efficiently recovered in epithelial and neuronal cells and tissues. In cerebellar granule cell cultures, hScrib and betaPIX are both partially localized at neuronal presynaptic compartments. Furthermore, we show that hScrib is required to anchor betaPIX at the cell cortex and that dominant-negative betaPIX or hScrib proteins can each inhibit Ca2+-dependent exocytosis in neuroendocrine PC12 cells, demonstrating a functional relationship between these proteins. These data reveal the existence of a tight hScrib/betaPIX interaction and suggest that this complex potentially plays a role in neuronal transmission.

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Virginie Orgogozo, François Schweisguth, Yohanns Bellaïche (2004 May 19)

Slit-Robo signalling prevents sensory cells from crossing the midline in Drosophila.

Mechanisms of development : 427-36 En savoir plus
Résumé

Maintenance of bilateral symmetry throughout animal development requires that both left and right halves of the body follow nearly identical patterns of cell proliferation, differentiation, death and migration. During formation of the perfectly bilateral Drosophila larval peripheral nervous system (PNS), the sensory precursor cells of the ventral multidendritic neuron vmd1a originating from each hemisegment migrate away from the ventral midline. Our observations indicate that in slit mutant embryos, as well as in robo, robo2 double mutants, sensory precursor cells of the left and right vmd1a neurons aberrantly cluster at the midline and then the pair of vmd1a neurons migrate to their final position on the same side of the embryo. This results in disruption of PNS bilateral symmetry. Expression of slit at the midline rescues the slit mutant vmd1a phenotype, suggesting that midline-secreted Slit activates Robo/Robo2 signalling to control the migration of the vmd1a sensory precursor cells. Our study indicates that midline-secreted Slit prevents vmd1a sensory cells from crossing the midline and thereby maintains PNS bilateral symmetry during development.

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Yohanns Bellaïche, Olivia Beaudoin-Massiani, Isabella Stuttem, François Schweisguth (2004 Jan 1)

The planar cell polarity protein Strabismus promotes Pins anterior localization during asymmetric division of sensory organ precursor cells in Drosophila.

Development (Cambridge, England) : 469-78 En savoir plus
Résumé

Cell fate diversity is generated in part by the unequal segregation of cell-fate determinants during asymmetric cell division. In the Drosophila bristle lineage, the sensory organ precursor (pI) cell is polarized along the anteroposterior (AP) axis by Frizzled (Fz) receptor signaling. We show here that Fz localizes at the posterior apical cortex of the pI cell prior to mitosis, whereas Strabismus (Stbm) and Prickle (Pk), which are also required for AP polarization of the pI cell, co-localize at the anterior apical cortex. Thus, asymmetric localization of Fz, Stbm and Pk define two opposite cortical domains prior to mitosis of the pI cell. At mitosis, Stbm forms an anterior crescent that overlaps with the distribution of Partner of Inscuteable (Pins) and Discs-large (Dlg), two components of the anterior Dlg-Pins-Galphai complex that regulates the localization of cell-fate determinants. At prophase, Stbm promotes the anterior localization of Pins. By contrast, Dishevelled (Dsh) acts antagonistically to Stbm by excluding Pins from the posterior cortex. We propose that the Stbm-dependent recruitment of Pins at the anterior cortex of the pI cell is a novel read-out of planar cell polarity.

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Année de publication : 2001

Yohanns Bellaïche, François Schweisguth (2001 Jul 13)

Lineage diversity in the Drosophila nervous system.

Current opinion in genetics & development : 418-23 En savoir plus
Résumé

The detailed descriptions of cellular lineages in the Drosophila nervous system have provided the foundations for an in-depth genetic analysis of the mechanisms that regulate fate decisions at every cell cycle.

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