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Liu X, Yam PT, Schlienger S, Cai E, Zhang J, Chen WJ, Torres Gutierrez O, Jimenez Amilburu V, Ramamurthy V, Ting AY, Branon TC, Cayouette M, Gen R, Marks T, Kong JH, Charron F, Ge X. Numb positively regulates Hedgehog signaling at the ciliary pocket. Nat Commun 2024; 15:3365. [PMID: 38664376 PMCID: PMC11045789 DOI: 10.1038/s41467-024-47244-1] [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] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2022] [Accepted: 03/25/2024] [Indexed: 04/28/2024] Open
Abstract
Hedgehog (Hh) signaling relies on the primary cilium, a cell surface organelle that serves as a signaling hub for the cell. Using proximity labeling and quantitative proteomics, we identify Numb as a ciliary protein that positively regulates Hh signaling. Numb localizes to the ciliary pocket and acts as an endocytic adaptor to incorporate Ptch1 into clathrin-coated vesicles, thereby promoting Ptch1 exit from the cilium, a key step in Hh signaling activation. Numb loss impedes Sonic hedgehog (Shh)-induced Ptch1 exit from the cilium, resulting in reduced Hh signaling. Numb loss in spinal neural progenitors reduces Shh-induced differentiation into cell fates reliant on high Hh activity. Genetic ablation of Numb in the developing cerebellum impairs the proliferation of granule cell precursors, a Hh-dependent process, resulting in reduced cerebellar size. This study highlights Numb as a regulator of ciliary Ptch1 levels during Hh signal activation and demonstrates the key role of ciliary pocket-mediated endocytosis in cell signaling.
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Affiliation(s)
- Xiaoliang Liu
- Department of Molecular and Cell Biology, University of California, Merced, Merced, CA, 95340, USA
| | - Patricia T Yam
- Montreal Clinical Research Institute (IRCM), Montreal, QC, H2W 1R7, Canada
| | - Sabrina Schlienger
- Montreal Clinical Research Institute (IRCM), Montreal, QC, H2W 1R7, Canada
- Department of Anatomy and Cell Biology, McGill University, Montreal, QC, H3A 0G4, Canada
| | - Eva Cai
- Department of Molecular and Cell Biology, University of California, Merced, Merced, CA, 95340, USA
| | - Jingyi Zhang
- Department of Molecular and Cell Biology, University of California, Merced, Merced, CA, 95340, USA
| | - Wei-Ju Chen
- Montreal Clinical Research Institute (IRCM), Montreal, QC, H2W 1R7, Canada
- Department of Biology, McGill University, Montreal, QC, H3A 0G4, Canada
| | - Oscar Torres Gutierrez
- Department of Molecular and Cell Biology, University of California, Merced, Merced, CA, 95340, USA
| | | | - Vasanth Ramamurthy
- Montreal Clinical Research Institute (IRCM), Montreal, QC, H2W 1R7, Canada
| | - Alice Y Ting
- Departments of Genetics, of Biology, and by courtesy, of Chemistry, Stanford University, Stanford, CA, USA
- Chan Zuckerberg Biohub, San Francisco, CA, USA
| | - Tess C Branon
- Departments of Genetics, of Biology, and by courtesy, of Chemistry, Stanford University, Stanford, CA, USA
- Chan Zuckerberg Biohub, San Francisco, CA, USA
- Interline Therapeutics, South San Francisco, CA, USA
| | - Michel Cayouette
- Montreal Clinical Research Institute (IRCM), Montreal, QC, H2W 1R7, Canada
- Department of Anatomy and Cell Biology, McGill University, Montreal, QC, H3A 0G4, Canada
- Department of Medicine, University of Montreal, Montreal, QC, H3T 1J4, Canada
| | - Risako Gen
- Department of Biochemistry, University of Washington, Seattle, WA, 98195, USA
| | - Tessa Marks
- Department of Biochemistry, University of Washington, Seattle, WA, 98195, USA
| | - Jennifer H Kong
- Department of Biochemistry, University of Washington, Seattle, WA, 98195, USA
| | - Frédéric Charron
- Montreal Clinical Research Institute (IRCM), Montreal, QC, H2W 1R7, Canada.
- Department of Anatomy and Cell Biology, McGill University, Montreal, QC, H3A 0G4, Canada.
- Department of Medicine, University of Montreal, Montreal, QC, H3T 1J4, Canada.
| | - Xuecai Ge
- Department of Molecular and Cell Biology, University of California, Merced, Merced, CA, 95340, USA.
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Schlienger S, Yam PT, Balekoglu N, Ducuing H, Michaud JF, Makihara S, Kramer DK, Chen B, Fasano A, Berardelli A, Hamdan FF, Rouleau GA, Srour M, Charron F. Genetics of mirror movements identifies a multifunctional complex required for Netrin-1 guidance and lateralization of motor control. Sci Adv 2023; 9:eadd5501. [PMID: 37172092 PMCID: PMC10181192 DOI: 10.1126/sciadv.add5501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 04/06/2023] [Indexed: 05/14/2023]
Abstract
Mirror movements (MM) disorder is characterized by involuntary movements on one side of the body that mirror intentional movements on the opposite side. We performed genetic characterization of a family with autosomal dominant MM and identified ARHGEF7, a RhoGEF, as a candidate MM gene. We found that Arhgef7 and its partner Git1 bind directly to Dcc. Dcc is the receptor for Netrin-1, an axon guidance cue that attracts commissural axons to the midline, promoting the midline crossing of axon tracts. We show that Arhgef7 and Git1 are required for Netrin-1-mediated axon guidance and act as a multifunctional effector complex. Arhgef7/Git1 activates Rac1 and Cdc42 and inhibits Arf1 downstream of Netrin-1. Furthermore, Arhgef7/Git1, via Arf1, mediates the Netrin-1-induced increase in cell surface Dcc. Mice heterozygous for Arhgef7 have defects in commissural axon trajectories and increased symmetrical paw placements during skilled walking, a MM-like phenotype. Thus, we have delineated how ARHGEF7 mutation causes MM.
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Affiliation(s)
- Sabrina Schlienger
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada
- Department of Anatomy and Cell Biology, Division of Experimental Medicine, McGill University, Montreal, QC H3A 0G4, Canada
| | - Patricia T. Yam
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada
| | - Nursen Balekoglu
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada
- Integrated Program in Neuroscience, McGill University, Montreal, QC H3A 2B4, Canada
| | - Hugo Ducuing
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada
| | - Jean-Francois Michaud
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada
| | - Shirin Makihara
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada
- Integrated Program in Neuroscience, McGill University, Montreal, QC H3A 2B4, Canada
| | - Daniel K. Kramer
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA
| | - Baoyu Chen
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA
| | - Alfonso Fasano
- Edmond J. Safra Program in Parkinson's Disease, Morton and Gloria Shulman Movement Disorders Clinic, Toronto Western Hospital, UHN, Toronto, ON, Canada
- Division of Neurology, University of Toronto, Toronto, ON, Canada
- Krembil Brain Institute, Toronto, ON, Canada
| | - Alfredo Berardelli
- IRCCS Neuromed, Pozzilli (IS), Italy
- Department of Human Neurosciences, Sapienza University of Rome, Rome, Italy
| | - Fadi F. Hamdan
- Division of Medical Genetics, Department of Pediatrics, CHU Sainte-Justine and University of Montreal, Montreal, QC H3T1C5, Canada
| | - Guy A. Rouleau
- Division of Medical Genetics, Department of Pediatrics, CHU Sainte-Justine and University of Montreal, Montreal, QC H3T1C5, Canada
- Department of Human Genetics, Montreal Neurological Institute and Hospital, McGill University, Montreal, QC, Canada
| | - Myriam Srour
- Department of Neurology and Neurosurgery, McGill University, Montreal, QC H3A 2B4, Canada
- Department of Pediatrics, Division of Pediatric Neurology, McGill University, Montreal, QC H4A 3J1, Canada
- McGill University Health Center Research Institute, Montreal, QC H4A 3J1, Canada
| | - Frederic Charron
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada
- Department of Anatomy and Cell Biology, Division of Experimental Medicine, McGill University, Montreal, QC H3A 0G4, Canada
- Integrated Program in Neuroscience, McGill University, Montreal, QC H3A 2B4, Canada
- Department of Medicine, University of Montreal, Montreal, QC H3T 1J4, Canada
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Ferent J, Constable S, Gigante ED, Yam PT, Mariani LE, Legué E, Liem KF, Caspary T, Charron F. The Ciliary Protein Arl13b Functions Outside of the Primary Cilium in Shh-Mediated Axon Guidance. Cell Rep 2019; 29:3356-3366.e3. [PMID: 31825820 PMCID: PMC6927553 DOI: 10.1016/j.celrep.2019.11.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 09/19/2019] [Accepted: 11/04/2019] [Indexed: 12/19/2022] Open
Abstract
The small GTPase Arl13b is enriched in primary cilia and regulates Sonic hedgehog (Shh) signaling. During neural development, Shh controls patterning and proliferation through a canonical, transcription-dependent pathway that requires the primary cilium. Additionally, Shh controls axon guidance through a non-canonical, transcription-independent pathway whose connection to the primary cilium is unknown. Here we show that inactivation of Arl13b results in defective commissural axon guidance in vivo. In vitro, we demonstrate that Arl13b functions autonomously in neurons for their Shh-dependent guidance response. We detect Arl13b protein in axons and growth cones, far from its well-established ciliary enrichment. To test whether Arl13b plays a non-ciliary function, we used an engineered, cilia-localization-deficient Arl13b variant and found that it was sufficient to mediate Shh axon guidance in vitro and in vivo. Together, these results indicate that, in addition to its ciliary role in canonical Shh signaling, Arl13b plays a cilia-independent role in Shh-mediated axon guidance.
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Affiliation(s)
- Julien Ferent
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada; Department of Neuroscience, University of Montreal, Montreal, QC H3T 1J4, Canada
| | - Sandii Constable
- Department of Human Genetics, 615 Michael St., Suite 301, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Eduardo D Gigante
- Department of Human Genetics, 615 Michael St., Suite 301, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Patricia T Yam
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada
| | - Laura E Mariani
- Department of Human Genetics, 615 Michael St., Suite 301, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Emilie Legué
- Vertebrate Developmental Biology Program and Department of Pediatrics, Yale School of Medicine, 333 Cedar St., New Haven, CT 06520, USA
| | - Karel F Liem
- Vertebrate Developmental Biology Program and Department of Pediatrics, Yale School of Medicine, 333 Cedar St., New Haven, CT 06520, USA
| | - Tamara Caspary
- Department of Human Genetics, 615 Michael St., Suite 301, Emory University School of Medicine, Atlanta, GA 30322, USA.
| | - Frédéric Charron
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada; Department of Neuroscience, University of Montreal, Montreal, QC H3T 1J4, Canada; Department of Anatomy and Cell Biology, Division of Experimental Medicine, McGill University, Montreal, QC H3A 0G4, Canada; Department of Medicine, University of Montreal, Montreal, QC H3T 1J4, Canada.
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Accogli A, Calabretta S, St-Onge J, Boudrahem-Addour N, Dionne-Laporte A, Joset P, Azzarello-Burri S, Rauch A, Krier J, Fieg E, Pallais JC, McConkie-Rosell A, McDonald M, Freedman SF, Rivière JB, Lafond-Lapalme J, Simpson BN, Hopkin RJ, Trimouille A, Van-Gils J, Begtrup A, McWalter K, Delphine H, Keren B, Genevieve D, Argilli E, Sherr EH, Severino M, Rouleau GA, Yam PT, Charron F, Srour M. De Novo Pathogenic Variants in N-cadherin Cause a Syndromic Neurodevelopmental Disorder with Corpus Collosum, Axon, Cardiac, Ocular, and Genital Defects. Am J Hum Genet 2019; 105:854-868. [PMID: 31585109 DOI: 10.1016/j.ajhg.2019.09.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [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: 05/28/2019] [Accepted: 09/05/2019] [Indexed: 01/06/2023] Open
Abstract
Cadherins constitute a family of transmembrane proteins that mediate calcium-dependent cell-cell adhesion. The extracellular domain of cadherins consists of extracellular cadherin (EC) domains, separated by calcium binding sites. The EC interacts with other cadherin molecules in cis and in trans to mechanically hold apposing cell surfaces together. CDH2 encodes N-cadherin, whose essential roles in neural development include neuronal migration and axon pathfinding. However, CDH2 has not yet been linked to a Mendelian neurodevelopmental disorder. Here, we report de novo heterozygous pathogenic variants (seven missense, two frameshift) in CDH2 in nine individuals with a syndromic neurodevelopmental disorder characterized by global developmental delay and/or intellectual disability, variable axon pathfinding defects (corpus callosum agenesis or hypoplasia, mirror movements, Duane anomaly), and ocular, cardiac, and genital anomalies. All seven missense variants (c.1057G>A [p.Asp353Asn]; c.1789G>A [p.Asp597Asn]; c.1789G>T [p.Asp597Tyr]; c.1802A>C [p.Asn601Thr]; c.1839C>G [p.Cys613Trp]; c.1880A>G [p.Asp627Gly]; c.2027A>G [p.Tyr676Cys]) result in substitution of highly conserved residues, and six of seven cluster within EC domains 4 and 5. Four of the substitutions affect the calcium-binding site in the EC4-EC5 interdomain. We show that cells expressing these variants in the EC4-EC5 domains have a defect in cell-cell adhesion; this defect includes impaired binding in trans with N-cadherin-WT expressed on apposing cells. The two frameshift variants (c.2563_2564delCT [p.Leu855Valfs∗4]; c.2564_2567dupTGTT [p.Leu856Phefs∗5]) are predicted to lead to a truncated cytoplasmic domain. Our study demonstrates that de novo heterozygous variants in CDH2 impair the adhesive activity of N-cadherin, resulting in a multisystemic developmental disorder, that could be named ACOG syndrome (agenesis of corpus callosum, axon pathfinding, cardiac, ocular, and genital defects).
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Affiliation(s)
- Andrea Accogli
- Department of Pediatrics, Division of Pediatric Neurology, McGill University, H4A 3J1, Montreal, QC, Canada; Medical Genetics Unit, IRCCS Ospedale Policlinico San Martino, 16132 Genova, Italy; Dipartimento di Neuroscienze, Reabilitazione, Oftalmologia, Genetica e Scienze Materno-Infantili, Università degli Studi di Genova, 16132 Genova Italy
| | - Sara Calabretta
- Montreal Clinical Research Institute, H2W 1R7 Montreal, QC, Canada
| | - Judith St-Onge
- McGill University Health Center Research Institute, H4A 3J1, Montreal, QC, Canada
| | | | | | - Pascal Joset
- Institute of Medical Genetics, University of Zurich, CH-8952 Schlieren, Switzerland
| | | | - Anita Rauch
- Institute of Medical Genetics, University of Zurich, CH-8952 Schlieren, Switzerland
| | - Joel Krier
- Brigham and Women's Hospital, Boston, MA 02115, USA
| | | | | | - Allyn McConkie-Rosell
- Division of Medical Genetics, Department of Pediatrics, Duke University, Durham, NC 27707, USA
| | - Marie McDonald
- Division of Medical Genetics, Department of Pediatrics, Duke University, Durham, NC 27707, USA
| | - Sharon F Freedman
- Department of Ophthalmology, Duke University Medical Center, Durham, NC 27710, USA
| | | | - Joël Lafond-Lapalme
- McGill University Health Center Research Institute, H4A 3J1, Montreal, QC, Canada
| | - Brittany N Simpson
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA
| | - Robert J Hopkin
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA
| | - Aurélien Trimouille
- Centre Hospitalier Universitaire Bordeaux, Service de Génétique Médicale, 33076 Bordeaux, France; Laboratoire Maladies Rares: Génétique et Métabolisme, Inserm U1211, Université de Bordeaux, 33076 Bordeaux, France
| | - Julien Van-Gils
- Centre Hospitalier Universitaire Bordeaux, Service de Génétique Médicale, 33076 Bordeaux, France; Laboratoire Maladies Rares: Génétique et Métabolisme, Inserm U1211, Université de Bordeaux, 33076 Bordeaux, France
| | | | | | - Heron Delphine
- Département de Génétique, Centre de Référence des Déficiences Intellectuelles de Causes Rares, Groupe Hospitalier Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, 75013 Paris
| | - Boris Keren
- Département de Génétique, Centre de Référence des Déficiences Intellectuelles de Causes Rares, Groupe Hospitalier Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, 75013 Paris
| | - David Genevieve
- Département de Genetique Médicale, Maladies Rares et Médecine Personnalisée, Centre de Référence Anomalies du Développement, Université Montpellier, Unité Inserm U1183, Centre Hospitalier Universitaire Montpellier, 34000 Montpellier, France
| | - Emanuela Argilli
- Departments of Neurology and Pediatrics, Weill Institute of Neuroscience and Institute of Human Genetics, University of California, CA 94143 San Francisco
| | - Elliott H Sherr
- Departments of Neurology and Pediatrics, Weill Institute of Neuroscience and Institute of Human Genetics, University of California, CA 94143 San Francisco
| | - Mariasavina Severino
- Istituto di Ricovero e Cura a Carattere Scientifico, Istituto Giannina Gaslini, 16147 Genova, Italy
| | - Guy A Rouleau
- Montreal Neurological Institute, McGill University, H3A 2B4, Montreal, QC, Canada; Department of Neurology and Neurosurgery, McGill University, H3A 2B4, Montreal, QC, Canada
| | - Patricia T Yam
- Montreal Clinical Research Institute, H2W 1R7 Montreal, QC, Canada
| | - Frédéric Charron
- Montreal Clinical Research Institute, H2W 1R7 Montreal, QC, Canada; Department of Medicine, University of Montreal, H3C 3J7, Montreal, QC, Canada; Department of Anatomy and Cell Biology, McGill University, H4A 3J1, Montreal, QC, Canada; Department of Experimental Medicine, McGill University, H4A 3J1, Montreal, QC, Canada.
| | - Myriam Srour
- Department of Pediatrics, Division of Pediatric Neurology, McGill University, H4A 3J1, Montreal, QC, Canada; McGill University Health Center Research Institute, H4A 3J1, Montreal, QC, Canada; Department of Neurology and Neurosurgery, McGill University, H3A 2B4, Montreal, QC, Canada.
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Ferent J, Giguère F, Jolicoeur C, Morin S, Michaud JF, Makihara S, Yam PT, Cayouette M, Charron F. Boc Acts via Numb as a Shh-Dependent Endocytic Platform for Ptch1 Internalization and Shh-Mediated Axon Guidance. Neuron 2019; 102:1157-1171.e5. [PMID: 31054872 DOI: 10.1016/j.neuron.2019.04.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 02/08/2019] [Accepted: 03/28/2019] [Indexed: 01/14/2023]
Abstract
During development, Shh attracts commissural axons toward the floor plate through a non-canonical, transcription-independent signaling pathway that requires the receptor Boc. Here, we find that Shh induces Boc internalization into early endosomes and that endocytosis is required for Shh-mediated growth-cone turning. Numb, an endocytic adaptor, binds to Boc and is required for Boc internalization, Shh-mediated growth-cone turning in vitro, and commissural axon guidance in vivo. Similar to Boc, Ptch1 is also internalized by Shh in a Numb-dependent manner; however, the binding of Shh to Ptch1 alone is not sufficient to induce Ptch1 internalization nor growth-cone turning. Therefore, the binding of Shh to Boc is required for Ptch1 internalization and growth-cone turning. Our data support a model where Boc endocytosis via Numb is required for Ptch1 internalization and Shh signaling in axon guidance. Thus, Boc acts as a Shh-dependent endocytic platform gating Ptch1 internalization and Shh signaling.
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Affiliation(s)
- Julien Ferent
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada; Department of Neuroscience, University of Montreal, Montreal, QC H3T 1J4, Canada
| | - Fanny Giguère
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada
| | - Christine Jolicoeur
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada
| | - Steves Morin
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada
| | - Jean-Francois Michaud
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada
| | - Shirin Makihara
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada
| | - Patricia T Yam
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada
| | - Michel Cayouette
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada; Department of Anatomy and Cell Biology, Division of Experimental Medicine, McGill University, Montreal, QC H3A 0G4, Canada; Department of Medicine, University of Montreal, Montreal, QC H3T 1J4, Canada
| | - Frederic Charron
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada; Department of Anatomy and Cell Biology, Division of Experimental Medicine, McGill University, Montreal, QC H3A 0G4, Canada; Department of Medicine, University of Montreal, Montreal, QC H3T 1J4, Canada; Department of Biology, McGill University, Montreal, QC H3A 0G4, Canada.
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Sloan TFW, Qasaimeh MA, Juncker D, Yam PT, Charron F. Integration of shallow gradients of Shh and Netrin-1 guides commissural axons. PLoS Biol 2015; 13:e1002119. [PMID: 25826604 PMCID: PMC4380419 DOI: 10.1371/journal.pbio.1002119] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [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: 07/30/2014] [Accepted: 03/03/2015] [Indexed: 11/19/2022] Open
Abstract
During nervous system development, gradients of Sonic Hedgehog (Shh) and Netrin-1 attract growth cones of commissural axons toward the floor plate of the embryonic spinal cord. Mice defective for either Shh or Netrin-1 signaling have commissural axon guidance defects, suggesting that both Shh and Netrin-1 are required for correct axon guidance. However, how Shh and Netrin-1 collaborate to guide axons is not known. We first quantified the steepness of the Shh gradient in the spinal cord and found that it is mostly very shallow. We then developed an in vitro microfluidic guidance assay to simulate these shallow gradients. We found that axons of dissociated commissural neurons respond to steep but not shallow gradients of Shh or Netrin-1. However, when we presented axons with combined Shh and Netrin-1 gradients, they had heightened sensitivity to the guidance cues, turning in response to shallower gradients that were unable to guide axons when only one cue was present. Furthermore, these shallow gradients polarized growth cone Src-family kinase (SFK) activity only when Shh and Netrin-1 were combined, indicating that SFKs can integrate the two guidance cues. Together, our results indicate that Shh and Netrin-1 synergize to enable growth cones to sense shallow gradients in regions of the spinal cord where the steepness of a single guidance cue is insufficient to guide axons, and we identify a novel type of synergy that occurs when the steepness (and not the concentration) of a guidance cue is limiting.
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Affiliation(s)
- Tyler F. W. Sloan
- Molecular Biology of Neural Development, Institut de Recherches Cliniques de Montréal (IRCM), Montreal, Quebec, Canada
- Division of Experimental Medicine, McGill University, Montreal, Quebec, Canada
- Program in Neuroengineering, McGill University, Montreal, Quebec, Canada
| | - Mohammad A. Qasaimeh
- Program in Neuroengineering, McGill University, Montreal, Quebec, Canada
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - David Juncker
- Program in Neuroengineering, McGill University, Montreal, Quebec, Canada
- Department of Biomedical Engineering, McGill University, Montreal, Quebec, Canada
- McGill University and Genome Quebec Innovation Centre, McGill University, Montreal, Quebec, Canada
| | - Patricia T. Yam
- Molecular Biology of Neural Development, Institut de Recherches Cliniques de Montréal (IRCM), Montreal, Quebec, Canada
| | - Frédéric Charron
- Molecular Biology of Neural Development, Institut de Recherches Cliniques de Montréal (IRCM), Montreal, Quebec, Canada
- Division of Experimental Medicine, McGill University, Montreal, Quebec, Canada
- Program in Neuroengineering, McGill University, Montreal, Quebec, Canada
- Department of Anatomy and Cell Biology, Department of Biology, McGill University, Quebec, Canada
- Department of Medicine, University of Montreal, Montreal, Quebec, Canada
- * E-mail:
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Yam PT, Charron F. Signaling mechanisms of non-conventional axon guidance cues: the Shh, BMP and Wnt morphogens. Curr Opin Neurobiol 2013; 23:965-73. [DOI: 10.1016/j.conb.2013.09.002] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Accepted: 09/03/2013] [Indexed: 11/29/2022]
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Yam PT, Pincus Z, Gupta GD, Bashkurov M, Charron F, Pelletier L, Colman DR. N-cadherin relocalizes from the periphery to the center of the synapse after transient synaptic stimulation in hippocampal neurons. PLoS One 2013; 8:e79679. [PMID: 24223993 PMCID: PMC3815108 DOI: 10.1371/journal.pone.0079679] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [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: 06/06/2013] [Accepted: 09/23/2013] [Indexed: 11/19/2022] Open
Abstract
N-cadherin is a cell adhesion molecule which is enriched at synapses. Binding of N-cadherin molecules to each other across the synaptic cleft has been postulated to stabilize adhesion between the presynaptic bouton and the postsynaptic terminal. N-cadherin is also required for activity-induced changes at synapses, including hippocampal long term potentiation and activity-induced spine expansion and stabilization. We hypothesized that these activity-dependent changes might involve changes in N-cadherin localization within synapses. To determine whether synaptic activity changes the localization of N-cadherin, we used structured illumination microscopy, a super-resolution approach which overcomes the conventional resolution limits of light microscopy, to visualize the localization of N-cadherin within synapses of hippocampal neurons. We found that synaptic N-cadherin exhibits a spectrum of localization patterns, ranging from puncta at the periphery of the synapse adjacent to the active zone to an even distribution along the synaptic cleft. Furthermore, the N-cadherin localization pattern within synapses changes during KCl depolarization and after transient synaptic stimulation. During KCl depolarization, N-cadherin relocalizes away from the central region of the synaptic cleft to the periphery of the synapse. In contrast, after transient synaptic stimulation with KCl followed by a period of rest in normal media, fewer synapses have N-cadherin present as puncta at the periphery and more synapses have N-cadherin present more centrally and uniformly along the synapse compared to unstimulated cells. This indicates that transient synaptic stimulation modulates N-cadherin localization within the synapse. These results bring new information to the structural organization and activity-induced changes occurring at synapses, and suggest that N-cadherin relocalization may contribute to activity dependent changes at synapses.
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Affiliation(s)
- Patricia T. Yam
- Department of Neurology and Neurosurgery, Montreal Neurological Institute and Hospital, McGill University, Montreal, Quebec, Canada
- Program in Neuroengineering, McGill University, Montreal, Quebec, Canada
- * E-mail:
| | - Zachary Pincus
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut, United States of America
| | - Gagan D. Gupta
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
| | - Mikhail Bashkurov
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
| | - Frédéric Charron
- Program in Neuroengineering, McGill University, Montreal, Quebec, Canada
- Molecular Biology of Neural Development, Institut de Recherches Cliniques de Montréal (IRCM), Montreal, Quebec, Canada
- Department of Medicine, University of Montreal, Montreal, Quebec, Canada
- Department of Anatomy and Cell Biology, Department of Biology, Division of Experimental Medicine, McGill University, Montreal, Quebec, Canada
| | - Laurence Pelletier
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - David R. Colman
- Department of Neurology and Neurosurgery, Montreal Neurological Institute and Hospital, McGill University, Montreal, Quebec, Canada
- Program in Neuroengineering, McGill University, Montreal, Quebec, Canada
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9
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Belkaid W, Thostrup P, Yam PT, Juzwik CA, Ruthazer ES, Dhaunchak AS, Colman DR. Cellular response to micropatterned growth promoting and inhibitory substrates. BMC Biotechnol 2013; 13:86. [PMID: 24119185 PMCID: PMC3819464 DOI: 10.1186/1472-6750-13-86] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [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: 02/28/2013] [Accepted: 10/08/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Normal development and the response to injury both require cell growth, migration and morphological remodeling, guided by a complex local landscape of permissive and inhibitory cues. A standard approach for studying by such cues is to culture cells on uniform substrates containing known concentrations of these molecules, however this method fails to represent the molecular complexity of the natural growth environment. RESULTS To mimic the local complexity of environmental conditions in vitro, we used a contact micropatterning technique to examine cell growth and differentiation on patterned substrates printed with the commonly studied growth permissive and inhibitory substrates, poly-L-lysine (PLL) and myelin, respectively. We show that micropatterning of PLL can be used to direct adherence and axonal outgrowth of hippocampal and cortical neurons as well as other cells with diverse morphologies like Oli-neu oligodendrocyte progenitor cell lines and fibroblast-like COS7 cells in culture. Surprisingly, COS7 cells exhibited a preference for low concentration (1 pg/mL) PLL zones over adjacent zones printed with high concentrations (1 mg/mL). We demonstrate that micropatterning is also useful for studying factors that inhibit growth as it can direct cells to grow along straight lines that are easy to quantify. Furthermore, we provide the first demonstration of microcontact printing of myelin-associated proteins and show that they impair process outgrowth from Oli-neu oligodendrocyte precursor cells. CONCLUSION We conclude that microcontact printing is an efficient and reproducible method for patterning proteins and brain-derived myelin on glass surfaces in order to study the effects of the microenvironment on cell growth and morphogenesis.
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Affiliation(s)
- Wiam Belkaid
- McGill Program in Neuroengineering, McGill University, Montreal, Canada.
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10
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Yam PT, Kent CB, Morin S, Farmer WT, Alchini R, Lepelletier L, Colman DR, Tessier-Lavigne M, Fournier AE, Charron F. 14-3-3 proteins regulate a cell-intrinsic switch from sonic hedgehog-mediated commissural axon attraction to repulsion after midline crossing. Neuron 2013. [PMID: 23177959 DOI: 10.1016/j.neuron.2012.09.017] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Axons must switch responsiveness to guidance cues during development for correct pathfinding. Sonic Hedgehog (Shh) attracts spinal cord commissural axons ventrally toward the floorplate. We show that after crossing the floorplate, commissural axons switch their response to Shh from attraction to repulsion, so that they are repelled anteriorly by a posterior-high/anterior-low Shh gradient along the longitudinal axis. This switch is recapitulated in vitro with dissociated commissural neurons as they age, indicating that the switch is intrinsic and time dependent. 14-3-3 protein inhibition converted Shh-mediated repulsion of aged dissociated neurons to attraction and prevented the correct anterior turn of postcrossing commissural axons in vivo, an effect mediated through PKA. Conversely, overexpression of 14-3-3 proteins was sufficient to drive the switch from Shh-mediated attraction to repulsion both in vitro and in vivo. Therefore, we identify a 14-3-3 protein-dependent mechanism for a cell-intrinsic temporal switch in the polarity of axon turning responses.
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Affiliation(s)
- Patricia T Yam
- Molecular Biology of Neural Development, Institut de Recherches Cliniques de Montréal, 110 Pine Avenue West, Montreal, Quebec H2W 1R7, Canada
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11
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Gopalakrishnan G, Yam PT, Madwar C, Bostina M, Rouiller I, Colman DR, Lennox RB. Label-free visualization of ultrastructural features of artificial synapses via cryo-EM. ACS Chem Neurosci 2011; 2:700-4. [PMID: 22860164 PMCID: PMC3369721 DOI: 10.1021/cn200094j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [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: 10/01/2011] [Accepted: 10/04/2011] [Indexed: 01/26/2023] Open
Abstract
The ultrastructural details of presynapses formed between artificial substrates of submicrometer silica beads and hippocampal neurons are visualized via cryo-electron microscopy (cryo-EM). The silica beads are derivatized by poly-d-lysine or lipid bilayers. Molecular features known to exist at presynapses are clearly present at these artificial synapses, as visualized by cryo-EM. Key synaptic features such as the membrane contact area at synaptic junctions, the presynaptic bouton containing presynaptic vesicles, as well as microtubular structures can be identified. This is the first report of the direct, label-free observation of ultrastructural details of artificial synapses.
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Affiliation(s)
- Gopakumar Gopalakrishnan
- Department of Chemistry, McGill
University, 801 Sherbrooke Street West, H3A
2K6 Montreal, Canada
- Montreal
Neurological Institute, McGill University, 3801 University Street, H3A 2B4
Montreal, Canada
| | - Patricia T. Yam
- Montreal
Neurological Institute, McGill University, 3801 University Street, H3A 2B4
Montreal, Canada
| | - Carolin Madwar
- Department of Chemistry, McGill
University, 801 Sherbrooke Street West, H3A
2K6 Montreal, Canada
| | - Mihnea Bostina
- Facility
for Electron Microscopy Research (FEMR), Department of Anatomy & Cell
Biology, McGill University, 3640 University Street, H3A
2B2 Montreal, Canada
| | - Isabelle Rouiller
- Facility
for Electron Microscopy Research (FEMR), Department of Anatomy & Cell
Biology, McGill University, 3640 University Street, H3A
2B2 Montreal, Canada
| | - David R. Colman
- Montreal
Neurological Institute, McGill University, 3801 University Street, H3A 2B4
Montreal, Canada
| | - R. Bruce Lennox
- Department of Chemistry, McGill
University, 801 Sherbrooke Street West, H3A
2K6 Montreal, Canada
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12
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Lucido AL, Gopalakrishnan G, Yam PT, Colman DR, Lennox RB. Isolation of functional presynaptic complexes from CNS neurons: a cell-free preparation for the study of presynaptic compartments In vitro. ACS Chem Neurosci 2010; 1:535-41. [PMID: 22777142 DOI: 10.1021/cn100048z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2010] [Accepted: 06/17/2010] [Indexed: 11/30/2022] Open
Abstract
The difficulty in developing successful treatments to facilitate nerve regeneration has prompted a number of new in vitro experimental methods. We have recently shown that functional presynaptic boutons can be formed when neuronal cells are cocultured with surface-modified artificial substrates including poly(d-lysine)-coated beads and supported lipid bilayer-coated beads (Lucido(2009) J. Neurosci.29, 12449-12466; Gopalakrishnan(2010) ACS Chem. Neurosci.1, 86-94). We demonstrate here, using confocal microscopy combined with immunocytochemistry, that it is possible to isolate such in vitro presynaptic endings in an exclusive fashion onto glass substrates through a simple "sandwich/lift-off" technique (Perez(2006) Adv. Funct. Mater.16, 306-312). Isolated presynaptic complexes are capable of releasing and recycling neurotransmitter in response to an external chemical trigger. These bead-presynaptic complexes are facile to prepare and are readily dispersible in solution. They are thus compatible with many experimental methods whose focus is the study of the neuronal presynaptic compartment.
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Affiliation(s)
- Anna Lisa Lucido
- Montreal Neurological Institute & Hospital, 3801 University Street
- McGill Program in NeuroEngineering
| | - Gopakumar Gopalakrishnan
- Montreal Neurological Institute & Hospital, 3801 University Street
- Department of Chemistry, 801 Sherbrooke Street West
- McGill Program in NeuroEngineering
- FQRNT Centre for Self-Assembled Chemical Structures (CSACS)
| | - Patricia T. Yam
- Montreal Neurological Institute & Hospital, 3801 University Street
- McGill Program in NeuroEngineering
| | - David R. Colman
- Montreal Neurological Institute & Hospital, 3801 University Street
- McGill Program in NeuroEngineering
| | - R. Bruce Lennox
- Department of Chemistry, 801 Sherbrooke Street West
- McGill Program in NeuroEngineering
- FQRNT Centre for Self-Assembled Chemical Structures (CSACS)
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Wilson CA, Tsuchida MA, Allen GM, Barnhart EL, Applegate KT, Yam PT, Ji L, Keren K, Danuser G, Theriot JA. Myosin II contributes to cell-scale actin network treadmilling through network disassembly. Nature 2010; 465:373-7. [PMID: 20485438 PMCID: PMC3662466 DOI: 10.1038/nature08994] [Citation(s) in RCA: 281] [Impact Index Per Article: 20.1] [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: 06/22/2007] [Accepted: 03/04/2010] [Indexed: 11/09/2022]
Abstract
Crawling locomotion of eukaryotic cells is achieved by a process dependent on the actin cytoskeleton: protrusion of the leading edge requires assembly of a network of actin filaments, which must be disassembled at the cell rear for sustained motility. Although ADF/cofilin proteins have been shown to contribute to actin disassembly, it is not clear how activity of these locally acting proteins could be coordinated over the distance scale of the whole cell. Here we show that non-muscle myosin II has a direct role in actin network disassembly in crawling cells. In fish keratocytes undergoing motility, myosin II is concentrated in regions at the rear with high rates of network disassembly. Activation of myosin II by ATP in detergent-extracted cytoskeletons results in rear-localized disassembly of the actin network. Inhibition of myosin II activity and stabilization of actin filaments synergistically impede cell motility, suggesting the existence of two disassembly pathways, one of which requires myosin II activity. Our results establish the importance of myosin II as an enzyme for actin network disassembly; we propose that gradual formation and reorganization of an actomyosin network provides an intrinsic destruction timer, enabling long-range coordination of actin network treadmilling in motile cells.
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Affiliation(s)
- Cyrus A Wilson
- Department of Biochemistry and Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, California 94305, USA
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14
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Abstract
Commissural neurons have been widely used to investigate the mechanisms underlying axon guidance during embryonic spinal cord development. The cell bodies of these neurons are located in the dorsal spinal cord and their axons follow stereotyped trajectories during embryonic development. Commissural axons initially project ventrally towards the floorplate. After crossing the midline, these axons turn anteriorly and project towards the brain. Each of these steps is regulated by the action of several guidance cues. Cultures highly enriched in commissural neurons are ideally suited for many experiments addressing the mechanisms of axon pathfinding, including turning assays, immunochemistry and biochemistry. Here, we describe a method to dissect and culture commissural neurons from E13 rat dorsal spinal cord. First, the spinal cord is isolated and dorsal strips are dissected out. The dorsal tissue is then dissociated into a cell suspension by trypsinization and mechanical disruption. Neurons are plated onto poly-L-lysine-coated glass coverslips or tissue-culture dishes. After 30 hours in vitro, most neurons have extended an axon. The purity of the culture (Yam et al. 2009), typically over 90%, can be assessed by immunolabeling with the commissural neuron markers DCC, LH2 and TAG1 (Helms and Johnson, 1998). This neuronal preparation is a useful tool for in vitro studies of the cellular and molecular mechanisms of commissural axon growth and guidance during spinal cord development.
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Affiliation(s)
- Sébastien D Langlois
- Molecular Biology of Neural Development, Institut de Recherches Cliniques de Montréal
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15
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Keren K, Yam PT, Kinkhabwala A, Mogilner A, Theriot JA. Intracellular fluid flow in rapidly moving cells. Nat Cell Biol 2009; 11:1219-24. [PMID: 19767741 DOI: 10.1038/ncb1965] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Accepted: 06/30/2009] [Indexed: 12/23/2022]
Abstract
Cytosolic fluid dynamics have been implicated in cell motility because of the hydrodynamic forces they induce and because of their influence on transport of components of the actin machinery to the leading edge. To investigate the existence and the direction of fluid flow in rapidly moving cells, we introduced inert quantum dots into the lamellipodia of fish epithelial keratocytes and analysed their distribution and motion. Our results indicate that fluid flow is directed from the cell body towards the leading edge in the cell frame of reference, at about 40% of cell speed. We propose that this forward-directed flow is driven by increased hydrostatic pressure generated at the rear of the cell by myosin contraction, and show that inhibition of myosin II activity by blebbistatin reverses the direction of fluid flow and leads to a decrease in keratocyte speed. We present a physical model for fluid pressure and flow in moving cells that quantitatively accounts for our experimental data.
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Affiliation(s)
- Kinneret Keren
- Department of Biochemistry and Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, California 94305, USA.
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16
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Yam PT, Langlois SD, Morin S, Charron F. Sonic hedgehog guides axons through a noncanonical, Src-family-kinase-dependent signaling pathway. Neuron 2009; 62:349-62. [PMID: 19447091 DOI: 10.1016/j.neuron.2009.03.022] [Citation(s) in RCA: 218] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Revised: 11/26/2008] [Accepted: 03/17/2009] [Indexed: 12/12/2022]
Abstract
Sonic hedgehog (Shh) plays essential roles in developmental events such as cell fate specification and axon guidance. Shh induces cell fate specification through canonical Shh signaling, mediated by transcription. However, the mechanism by which Shh guides axons is unknown. To study this, we developed an in vitro assay for axon guidance, in which neurons can be imaged while responding to a defined gradient of a chemical cue. Axons of dissociated commissural neurons placed in a Shh gradient turned rapidly toward increasing concentrations of Shh. Consistent with this rapid response, we showed that attraction by Shh does not require transcription. Instead, Shh stimulates the activity of Src family kinase (SFK) members in a Smoothened-dependent manner. Moreover, SFK activity is required for Shh-mediated guidance of commissural axons, but not for induction of Gli transcriptional reporter activity. Together, these results indicate that Shh acts via a rapidly acting, noncanonical signaling pathway to guide axons.
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Affiliation(s)
- Patricia T Yam
- Molecular Biology of Neural Development, Institut de Recherches Cliniques de Montréal (IRCM), Montreal, QC, Canada
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17
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Yam PT, Wilson CA, Ji L, Hebert B, Barnhart EL, Dye NA, Wiseman PW, Danuser G, Theriot JA. Actin-myosin network reorganization breaks symmetry at the cell rear to spontaneously initiate polarized cell motility. ACTA ACUST UNITED AC 2007; 178:1207-21. [PMID: 17893245 PMCID: PMC2064654 DOI: 10.1083/jcb.200706012] [Citation(s) in RCA: 186] [Impact Index Per Article: 10.9] [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] [Indexed: 01/29/2023]
Abstract
We have analyzed the spontaneous symmetry breaking and initiation of actin-based motility in keratocytes (fish epithelial cells). In stationary keratocytes, the actin network flow was inwards and radially symmetric. Immediately before motility initiation, the actin network flow increased at the prospective cell rear and reoriented in the perinuclear region, aligning with the prospective axis of movement. Changes in actin network flow at the cell front were detectable only after cell polarization. Inhibition of myosin II or Rho kinase disrupted actin network organization and flow in the perinuclear region and decreased the motility initiation frequency, whereas increasing myosin II activity with calyculin A increased the motility initiation frequency. Local stimulation of myosin activity in stationary cells by the local application of calyculin A induced directed motility initiation away from the site of stimulation. Together, these results indicate that large-scale actin–myosin network reorganization and contractility at the cell rear initiate spontaneous symmetry breaking and polarized motility of keratocytes.
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Affiliation(s)
- Patricia T Yam
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
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18
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Yam PT, Theriot JA. Repeated cycles of rapid actin assembly and disassembly on epithelial cell phagosomes. Mol Biol Cell 2004; 15:5647-58. [PMID: 15456901 PMCID: PMC532043 DOI: 10.1091/mbc.e04-06-0509] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [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: 06/22/2004] [Revised: 09/17/2004] [Accepted: 09/20/2004] [Indexed: 11/11/2022] Open
Abstract
We have found that early in infection of the intracellular pathogen Listeria monocytogenes in Madin-Darby canine kidney epithelial cells expressing actin conjugated to green fluorescent protein, F-actin rapidly assembles (approximately 25 s) and disassembles (approximately 30 s) around the bacteria, a phenomenon we call flashing. L. monocytogenes strains unable to perform actin-based motility or unable to escape the phagosome were capable of flashing, suggesting that the actin assembly occurs on the phagosome membrane. Cycles of actin assembly and disassembly could occur repeatedly on the same phagosome. Indirect immunofluorescence showed that most bacteria were fully internalized when flashing occurred, suggesting that actin flashing does not represent phagocytosis. Escherichia coli expressing invA, a gene product from Yersinia pseudotuberculosis that mediates cellular invasion, also induced flashing. Furthermore, polystyrene beads coated with E-cadherin or transferrin also induced flashing after internalization. This suggests that flashing occurs downstream of several distinct molecular entry mechanisms and may be a general consequence of internalization of large objects by epithelial cells.
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Affiliation(s)
- Patricia T Yam
- Department of Biochemistry, Stanford University School of Medicine, Stanford CA 94305, USA
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Abstract
It has been proposed that certain cell-surface proteins undergo redox reactions, that is, transfer of hydrogens and electrons between closely spaced cysteine thiols that can lead to reduction, formation, or interchange of disulfide bonds. This concept was tested using a membrane-impermeable trivalent arsenical to identify closely spaced thiols in cell-surface proteins. We attached the trivalent arsenical, phenylarsenoxide, to the thiol of reduced glutathione to produce 4-(N-(S-glutathionylacetyl)amino)phenylarsenoxide (GSAO). GSAO bound tightly to synthetic, peptide, and protein dithiols like thioredoxin, but not to monothiols. To identify cell-surface proteins that contain closely spaced thiols, we attached a biotin moiety through a spacer arm to the primary amino group of the gamma-glutamyl residue of GSAO (GSAO-B). Incorporation of GSAO-B into proteins was assessed by measuring the biotin using streptavidin-peroxidase. Up to 12 distinct proteins were labeled with GSAO-B on the surface of endothelial and fibrosarcoma cells. The pattern of labeled proteins differed between the different cell types. Protein disulfide isomerase was one of the proteins on the endothelial and fibrosarcoma cell surface that incorporated GSAO-B. These findings demonstrate that the cell-surface environment can support the existence of closely spaced protein thiols and suggest that at least some of these thiols are redox active.
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Affiliation(s)
- N Donoghue
- Centre for Thrombosis and Vascular Research, School of Pathology, University of New South Wales, Sydney, Australia
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