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Mukherjee A, Jeske YA, Becam I, Taïeb A, Brooks P, Aouad J, Monguillon C, Conduit PT. γ-TuRCs and Augmin are required for the development of highly branched dendritic arbors in Drosophila. J Cell Sci 2024:jcs.261534. [PMID: 38606636 DOI: 10.1242/jcs.261534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Accepted: 04/05/2024] [Indexed: 04/13/2024] Open
Abstract
Microtubules are nucleated by γ-tubulin ring complexes (γ-TuRCs) and are essential for neuronal development. Nevertheless, γ-TuRC depletion has been reported to perturb only higher-order branching in elaborated Drosophila larval class IV dendritic arborisation (da) neurons. This relatively mild phenotype was attributed to defects in microtubule nucleation from Golgi outposts, yet most Golgi outposts lack associated γ-TuRCs. By analysing dendritic arbor regrowth in pupae, we show that γ-TuRCs are also required for the growth and branching of primary and secondary dendrites, as well as for higher-order branching. Moreover, we identify the Augmin complex, which recruits γ-TuRCs to the sides of pre-existing microtubules, as being required predominantly for higher-order branching, likely by increasing the frequency of microtubule growth in terminal dendrites. Consistently, we find that Augmin is expressed less strongly and is largely dispensable in larval class I da neurons, which exhibit few higher-order dendrites. Thus, γ-TuRCs are essential for various aspects of complex dendritic arbor development, and they appear to function in higher-order branching via the Augmin pathway, which promotes the elaboration of dendritic arbors to help define neuronal morphology.
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Affiliation(s)
- Amrita Mukherjee
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK
- MRC Toxicology Unit, Gleeson Building, Tennis Court Road, Cambridge CB2 1QR, UK
| | - Yaiza Andrés Jeske
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK
| | - Isabelle Becam
- Université Paris Cité, CNRS, Institut Jacques Monod, F-75013, Paris, France
| | - Anaelle Taïeb
- Université Paris Cité, CNRS, Institut Jacques Monod, F-75013, Paris, France
| | - Paul Brooks
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK
| | - Joanna Aouad
- Université Paris Cité, CNRS, Institut Jacques Monod, F-75013, Paris, France
| | | | - Paul T Conduit
- Université Paris Cité, CNRS, Institut Jacques Monod, F-75013, Paris, France
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Zhu Z, Becam I, Tovey CA, Elfarkouchi A, Yen EC, Bernard F, Guichet A, Conduit PT. Multifaceted modes of γ-tubulin complex recruitment and microtubule nucleation at mitotic centrosomes. J Cell Biol 2023; 222:e202212043. [PMID: 37698931 PMCID: PMC10497398 DOI: 10.1083/jcb.202212043] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 05/18/2023] [Accepted: 07/24/2023] [Indexed: 09/14/2023] Open
Abstract
Microtubule nucleation is mediated by γ-tubulin ring complexes (γ-TuRCs). In most eukaryotes, a GCP4/5/4/6 "core" complex promotes γ-tubulin small complex (γ-TuSC) association to generate cytosolic γ-TuRCs. Unlike γ-TuSCs, however, this core complex is non-essential in various species and absent from budding yeasts. In Drosophila, Spindle defective-2 (Spd-2) and Centrosomin (Cnn) redundantly recruit γ-tubulin complexes to mitotic centrosomes. Here, we show that Spd-2 recruits γ-TuRCs formed via the GCP4/5/4/6 core, but Cnn can recruit γ-TuSCs directly via its well-conserved CM1 domain, similar to its homologs in budding yeast. When centrosomes fail to recruit γ-tubulin complexes, they still nucleate microtubules via the TOG domain protein Mini-spindles (Msps), but these microtubules have different dynamic properties. Our data, therefore, help explain the dispensability of the GCP4/5/4/6 core and highlight the robustness of centrosomes as microtubule organizing centers. They also suggest that the dynamic properties of microtubules are influenced by how they are nucleated.
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Affiliation(s)
- Zihan Zhu
- Department of Zoology, University of Cambridge, Cambridge, UK
| | - Isabelle Becam
- Université Paris Cité, CNRS, Institut Jacques Monod, Paris, France
| | - Corinne A. Tovey
- Université Paris Cité, CNRS, Institut Jacques Monod, Paris, France
| | - Abir Elfarkouchi
- Université Paris Cité, CNRS, Institut Jacques Monod, Paris, France
| | - Eugenie C. Yen
- Department of Zoology, University of Cambridge, Cambridge, UK
| | - Fred Bernard
- Université Paris Cité, CNRS, Institut Jacques Monod, Paris, France
| | - Antoine Guichet
- Université Paris Cité, CNRS, Institut Jacques Monod, Paris, France
| | - Paul T. Conduit
- Department of Zoology, University of Cambridge, Cambridge, UK
- Université Paris Cité, CNRS, Institut Jacques Monod, Paris, France
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Gonçalves Antunes M, Sanial M, Contremoulins V, Carvalho S, Plessis A, Becam I. High hedgehog signaling is transduced by a multikinase-dependent switch controlling the apico-basal distribution of the GPCR smoothened. eLife 2022; 11:79843. [PMID: 36083801 PMCID: PMC9462849 DOI: 10.7554/elife.79843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Accepted: 08/22/2022] [Indexed: 11/13/2022] Open
Abstract
The oncogenic G-protein-coupled receptor (GPCR) Smoothened (SMO) is a key transducer of the hedgehog (HH) morphogen, which plays an essential role in the patterning of epithelial structures. Here, we examine how HH controls SMO subcellular localization and activity in a polarized epithelium using the Drosophila wing imaginal disc as a model. We provide evidence that HH promotes the stabilization of SMO by switching its fate after endocytosis toward recycling. This effect involves the sequential and additive action of protein kinase A, casein kinase I, and the Fused (FU) kinase. Moreover, in the presence of very high levels of HH, the second effect of FU leads to the local enrichment of SMO in the most basal domain of the cell membrane. Together, these results link the morphogenetic effects of HH to the apico-basal distribution of SMO and provide a novel mechanism for the regulation of a GPCR.
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Affiliation(s)
| | | | | | | | - Anne Plessis
- Université Paris Cité, CNRS, Institut Jacques Monod
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Roberto N, Becam I, Plessis A, Holmgren RA. Engrailed, Suppressor of fused and Roadkill modulate the Drosophila GLI transcription factor Cubitus interruptus at multiple levels. Development 2022; 149:dev200159. [PMID: 35290435 PMCID: PMC10656455 DOI: 10.1242/dev.200159] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 02/03/2022] [Indexed: 12/24/2022]
Abstract
Morphogen gradients need to be robust, but may also need to be tailored for specific tissues. Often this type of regulation is carried out by negative regulators and negative feedback loops. In the Hedgehog (Hh) pathway, activation of patched (ptc) in response to Hh is part of a negative feedback loop limiting the range of the Hh morphogen. Here, we show that in the Drosophila wing imaginal disc two other known Hh targets genes feed back to modulate Hh signaling. First, anterior expression of the transcriptional repressor Engrailed modifies the Hh gradient by attenuating the expression of the Hh pathway transcription factor cubitus interruptus (ci), leading to lower levels of ptc expression. Second, the E-3 ligase Roadkill shifts the competition between the full-length activator and truncated repressor forms of Ci by preferentially targeting full-length Ci for degradation. Finally, we provide evidence that Suppressor of fused, a negative regulator of Hh signaling, has an unexpected positive role, specifically protecting full-length Ci but not the Ci repressor from Roadkill.
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Affiliation(s)
- Nicole Roberto
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60201, USA
| | - Isabelle Becam
- Université de Paris, CNRS, Institut Jacques Monod, F-75013 Paris, France
| | - Anne Plessis
- Université de Paris, CNRS, Institut Jacques Monod, F-75013 Paris, France
| | - Robert A. Holmgren
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60201, USA
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Becam I, Rafel N, Hong X, Cohen SM, Milán M. Notch-mediated repression of bantam miRNA contributes to boundary formation in the Drosophila wing. Development 2011; 138:3781-9. [DOI: 10.1242/dev.064774] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Subdivision of proliferating tissues into adjacent compartments that do not mix plays a key role in animal development. The Actin cytoskeleton has recently been shown to mediate cell sorting at compartment boundaries, and reduced cell proliferation in boundary cells has been proposed as a way of stabilizing compartment boundaries. Cell interactions mediated by the receptor Notch have been implicated in the specification of compartment boundaries in vertebrates and in Drosophila, but the molecular effectors remain largely unidentified. Here, we present evidence that Notch mediates boundary formation in the Drosophila wing in part through repression of bantam miRNA. bantam induces cell proliferation and we have identified the Actin regulator Enabled as a new target of bantam. Increased levels of Enabled and reduced proliferation rates contribute to the maintenance of the dorsal-ventral affinity boundary. The activity of Notch also defines, through the homeobox-containing gene cut, a distinct population of boundary cells at the dorsal-ventral (DV) interface that helps to segregate boundary from non-boundary cells and contributes to the maintenance of the DV affinity boundary.
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Affiliation(s)
- Isabelle Becam
- Institute for Research in Biomedicine (IRB Barcelona), Parc Científic de Barcelona, Baldiri Reixac, 10-12, 08028 Barcelona, Spain
| | - Neus Rafel
- Institute for Research in Biomedicine (IRB Barcelona), Parc Científic de Barcelona, Baldiri Reixac, 10-12, 08028 Barcelona, Spain
| | - Xin Hong
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore
| | - Stephen M. Cohen
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore
| | - Marco Milán
- Institute for Research in Biomedicine (IRB Barcelona), Parc Científic de Barcelona, Baldiri Reixac, 10-12, 08028 Barcelona, Spain
- ICREA, Parc Científic de Barcelona, Baldiri Reixac, 10-12, 08028 Barcelona, Spain
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Becam I, Fiuza UM, Arias AM, Milán M. A role of receptor Notch in ligand cis-inhibition in Drosophila. Curr Biol 2010; 20:554-60. [PMID: 20226663 DOI: 10.1016/j.cub.2010.01.058] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2009] [Revised: 01/04/2010] [Accepted: 01/27/2010] [Indexed: 01/17/2023]
Abstract
Notch and its ligands mediate short-range cell interactions that play a conserved role in inducing cell fate specification. Several regulatory mechanisms have been described to ensure robust polarized signaling from signal-sending to signal-receiving cells. High levels of ligand expression activate Notch in nearby cells and exert a cell-autonomous dominant-negative effect on Notch activity. This regulatory process is called cis-inhibition and helps to restrict Notch activation to signal-receiving cells. By combining genetic mosaics in the Drosophila wing primordium with cell culture assays, we present evidence here that Notch promotes the clearance of Serrate ligand from the cell surface and exerts an inhibitory effect on the activity of Serrate expressed in the same cell. These regulatory mechanisms are independent of Notch-mediated transcription and are executed by the extracellular domain of Notch. We show that this process is required to block Serrate-mediated activation of Notch in the signal-sending cell population and helps to restrict Notch activation to the signal-receiving cells. Altogether, our results, in concert with previous results on ligand-mediated Notch cis-inhibition, indicate that mutual inhibition between ligand and receptor in signal-sending cells helps to block Notch activity in these cells and to restrict receptor activation in signal-receiving cells.
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Affiliation(s)
- Isabelle Becam
- Institute for Research in Biomedicine (IRB Barcelona), Parc Científic de Barcelona, Baldiri Reixac 10-12, 08028 Barcelona, Spain
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