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Dobramysl U, Jarsch IK, Inoue Y, Shimo H, Richier B, Gadsby JR, Mason J, Szałapak A, Ioannou PS, Correia GP, Walrant A, Butler R, Hannezo E, Simons BD, Gallop JL. Stochastic combinations of actin regulatory proteins are sufficient to drive filopodia formation. J Cell Biol 2021; 220:e202003052. [PMID: 33740033 PMCID: PMC7980258 DOI: 10.1083/jcb.202003052] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 11/23/2020] [Accepted: 01/12/2021] [Indexed: 11/22/2022] Open
Abstract
Assemblies of actin and its regulators underlie the dynamic morphology of all eukaryotic cells. To understand how actin regulatory proteins work together to generate actin-rich structures such as filopodia, we analyzed the localization of diverse actin regulators within filopodia in Drosophila embryos and in a complementary in vitro system of filopodia-like structures (FLSs). We found that the composition of the regulatory protein complex where actin is incorporated (the filopodial tip complex) is remarkably heterogeneous both in vivo and in vitro. Our data reveal that different pairs of proteins correlate with each other and with actin bundle length, suggesting the presence of functional subcomplexes. This is consistent with a theoretical framework where three or more redundant subcomplexes join the tip complex stochastically, with any two being sufficient to drive filopodia formation. We provide an explanation for the observed heterogeneity and suggest that a mechanism based on multiple components allows stereotypical filopodial dynamics to arise from diverse upstream signaling pathways.
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Affiliation(s)
- Ulrich Dobramysl
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Iris Katharina Jarsch
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Yoshiko Inoue
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Hanae Shimo
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Benjamin Richier
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Jonathan R. Gadsby
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Julia Mason
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Alicja Szałapak
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Pantelis Savvas Ioannou
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | | | - Astrid Walrant
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Richard Butler
- Gurdon Institute, University of Cambridge, Cambridge, UK
| | - Edouard Hannezo
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - Benjamin D. Simons
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, UK
| | - Jennifer L. Gallop
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
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Richier B, Inoue Y, Dobramysl U, Friedlander J, Brown NH, Gallop JL. Integrin signaling downregulates filopodia during muscle-tendon attachment. J Cell Sci 2018; 131:jcs.217133. [PMID: 30054384 PMCID: PMC6127725 DOI: 10.1242/jcs.217133] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 07/12/2018] [Indexed: 11/25/2022] Open
Abstract
Cells need to sense their environment to ensure accurate targeting to specific destinations. This occurs in developing muscles, which need to attach to tendon cells before muscle contractions can begin. Elongating myotube tips form filopodia, which are presumed to have sensory roles, and are later suppressed upon building the attachment site. Here, we use live imaging and quantitative image analysis of lateral transverse (LT) myotubes in Drosophila to show that filopodia suppression occurs as a result of integrin signaling. Loss of the integrin subunits αPS2 and βPS (also known as If and Mys, respectively, in flies) increased filopodia number and length at stages when they are normally suppressed. Conversely, inducing integrin signaling, achieved by the expression of constitutively dimerised βPS cytoplasmic domain (diβ), prematurely suppressed filopodia. We discovered that the integrin signal is transmitted through the protein G protein-coupled receptor kinase interacting ArfGAP (Git) and its downstream kinase p21-activated kinase (Pak). Absence of these proteins causes profuse filopodia and prevents the filopodial inhibition mediated by diβ. Thus, integrin signaling terminates the exploratory behavior of myotubes seeking tendons, enabling the actin machinery to focus on forming a strong attachment and assembling the contractile apparatus. Summary: Integrins signal through Git and Pak to downregulate filopodia when muscles reach their target attachment site in Drosophila.
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Affiliation(s)
- Benjamin Richier
- The Gurdon Institute, Tennis Court Rd, Cambridge CB2 1QN, UK.,Dept. of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - Yoshiko Inoue
- The Gurdon Institute, Tennis Court Rd, Cambridge CB2 1QN, UK.,Dept. of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK.,Dept. of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
| | - Ulrich Dobramysl
- The Gurdon Institute, Tennis Court Rd, Cambridge CB2 1QN, UK.,Dept. of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - Jonathan Friedlander
- The Gurdon Institute, Tennis Court Rd, Cambridge CB2 1QN, UK.,Dept. of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
| | - Nicholas H Brown
- The Gurdon Institute, Tennis Court Rd, Cambridge CB2 1QN, UK.,Dept. of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
| | - Jennifer L Gallop
- The Gurdon Institute, Tennis Court Rd, Cambridge CB2 1QN, UK .,Dept. of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
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Urbančič V, Butler R, Richier B, Peter M, Mason J, Livesey FJ, Holt CE, Gallop JL. Filopodyan: An open-source pipeline for the analysis of filopodia. J Cell Biol 2017; 216:3405-3422. [PMID: 28760769 PMCID: PMC5626553 DOI: 10.1083/jcb.201705113] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 06/28/2017] [Accepted: 07/06/2017] [Indexed: 02/07/2023] Open
Abstract
Filopodia have important sensory and mechanical roles in motile cells. The recruitment of actin regulators, such as ENA/VASP proteins, to sites of protrusion underlies diverse molecular mechanisms of filopodia formation and extension. We developed Filopodyan (filopodia dynamics analysis) in Fiji and R to measure fluorescence in filopodia and at their tips and bases concurrently with their morphological and dynamic properties. Filopodyan supports high-throughput phenotype characterization as well as detailed interactive editing of filopodia reconstructions through an intuitive graphical user interface. Our highly customizable pipeline is widely applicable, capable of detecting filopodia in four different cell types in vitro and in vivo. We use Filopodyan to quantify the recruitment of ENA and VASP preceding filopodia formation in neuronal growth cones, and uncover a molecular heterogeneity whereby different filopodia display markedly different responses to changes in the accumulation of ENA and VASP fluorescence in their tips over time.
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Affiliation(s)
- Vasja Urbančič
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, England, UK
- Department of Biochemistry, University of Cambridge, Cambridge, England, UK
| | - Richard Butler
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, England, UK
| | - Benjamin Richier
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, England, UK
- Department of Biochemistry, University of Cambridge, Cambridge, England, UK
| | - Manuel Peter
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, England, UK
- Department of Biochemistry, University of Cambridge, Cambridge, England, UK
| | - Julia Mason
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, England, UK
- Department of Biochemistry, University of Cambridge, Cambridge, England, UK
| | - Frederick J Livesey
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, England, UK
- Department of Biochemistry, University of Cambridge, Cambridge, England, UK
| | - Christine E Holt
- Department of Physiology, Development, and Neuroscience, University of Cambridge, Cambridge, England, UK
| | - Jennifer L Gallop
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, England, UK
- Department of Biochemistry, University of Cambridge, Cambridge, England, UK
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Richier B, Vijandi CDM, Mackensen S, Salecker I. Lapsyn controls branch extension and positioning of astrocyte-like glia in the Drosophila optic lobe. Nat Commun 2017; 8:317. [PMID: 28827667 PMCID: PMC5567088 DOI: 10.1038/s41467-017-00384-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [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: 11/15/2016] [Accepted: 06/21/2017] [Indexed: 11/09/2022] Open
Abstract
Astrocytes have diverse, remarkably complex shapes in different brain regions. Their branches closely associate with neurons. Despite the importance of this heterogeneous glial cell type for brain development and function, the molecular cues controlling astrocyte branch morphogenesis and positioning during neural circuit assembly remain largely unknown. We found that in the Drosophila visual system, astrocyte-like medulla neuropil glia (mng) variants acquire stereotypic morphologies with columnar and layered branching patterns in a stepwise fashion from mid-metamorphosis onwards. Using knockdown and loss-of-function analyses, we uncovered a previously unrecognized role for the transmembrane leucine-rich repeat protein Lapsyn in regulating mng development. lapsyn is expressed in mng and cell-autonomously required for branch extension into the synaptic neuropil and anchoring of cell bodies at the neuropil border. Lapsyn works in concert with the fibroblast growth factor (FGF) pathway to promote branch morphogenesis, while correct positioning is essential for mng survival mediated by gliotrophic FGF signaling. How glial cells, such as astrocytes, acquire their characteristic morphology during development is poorly understood. Here the authors describe the morphogenesis of astrocyte-like glia in the Drosophila optic lobe, and through a RNAi screen, they identify a transmembrane LRR protein–Lapsyn–that plays a critical role in this process.
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Affiliation(s)
- Benjamin Richier
- The Francis Crick Institute, Visual Circuit Assembly Laboratory, 1 Midland Road, London, NW1 1AT, UK.,The Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QN, UK
| | | | - Stefanie Mackensen
- The Francis Crick Institute, Visual Circuit Assembly Laboratory, 1 Midland Road, London, NW1 1AT, UK.,University of Münster, Institute of Neuro- and Behavioral Biology, Badestr. 9, 48149, Muenster, Germany
| | - Iris Salecker
- The Francis Crick Institute, Visual Circuit Assembly Laboratory, 1 Midland Road, London, NW1 1AT, UK.
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Abstract
UNLABELLED Advances in labeling technologies are instrumental to study the developmental mechanisms that control organ formation and function at the cellular level. Until recently, genetic tools relied on the expression of single markers to visualize individual cells or lineages in developing and adult animals. Exploiting the expanding color palette of fluorescent proteins and the power of site-specific recombinases in rearranging DNA fragments, the development of Brainbow strategies in mice made it possible to stochastically label many cells in different colors within the same sample. Over the past years, these pioneering approaches have been adapted for other experimental model organisms, including Drosophila melanogaster, zebrafish, and chicken. Balancing the distinct requirements of single cell and clonal analyses, adjustments were made that both enhance and expand the functionality of these tools. Multicolor cell labeling techniques have been successfully applied in studies analyzing the cellular components of neural circuits and other tissues, and the compositions and interactions of lineages. While being continuously refined, Brainbow technologies have thus found a firm place in the genetic toolboxes of developmental and neurobiologists. For further resources related to this article, please visit the WIREs website. CONFLICT OF INTEREST The authors have declared no conflicts of interest for this article.
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Affiliation(s)
- Benjamin Richier
- MRC National Institute for Medical Research, Division of Molecular NeurobiologyLondon, UK
| | - Iris Salecker
- MRC National Institute for Medical Research, Division of Molecular NeurobiologyLondon, UK
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Cusumano P, Klarsfeld A, Chélot E, Picot M, Richier B, Rouyer F. PDF-modulated visual inputs and cryptochrome define diurnal behavior in Drosophila. Nat Neurosci 2009; 12:1431-7. [DOI: 10.1038/nn.2429] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2009] [Accepted: 09/21/2009] [Indexed: 01/25/2023]
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Richier B, Michard-Vanhée C, Lamouroux A, Papin C, Rouyer F. The clockwork orange Drosophila protein functions as both an activator and a repressor of clock gene expression. J Biol Rhythms 2008; 23:103-16. [PMID: 18375860 DOI: 10.1177/0748730407313817] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The Drosophila clock relies on transcriptional feedback loops that generate daily oscillations of the clock gene expression at mRNA and protein levels. In the evening, the CLOCK (CLK) and CYCLE (CYC) basic helix-loop-helix (bHLH) PAS-domain transcription factors activate the expression of the period (per) and timeless (tim) genes. Posttranslational modifications delay the accumulation of PER and TIM, which inhibit CLK/CYC activity in the late night. We show here that a null mutant of the clockwork orange (cwo) gene encoding a bHLH orange-domain putative transcription factor displays long-period activity rhythms. cwo loss of function increases cwo mRNA levels but reduces mRNA peak levels of the 4 described CLK/CYC targets, inducing an almost complete loss of their cycling. In addition, the absence of CWO induces alterations of PER and CLK phosphorylation cycles. Our results indicate that, in vivo, CWO modulates clock gene expression through both repressor and activator transcriptional functions.
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Affiliation(s)
- Benjamin Richier
- Institut de Neurobiologie Alfred Fessard, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France
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