1
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Ruan ZR, Yu Z, Xing C, Chen EH. Inter-organ steroid hormone signaling promotes myoblast fusion via direct transcriptional regulation of a single key effector gene. Curr Biol 2024; 34:1438-1452.e6. [PMID: 38513654 PMCID: PMC11003854 DOI: 10.1016/j.cub.2024.02.056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2023] [Revised: 12/24/2023] [Accepted: 02/23/2024] [Indexed: 03/23/2024]
Abstract
Steroid hormones regulate tissue development and physiology by modulating the transcription of a broad spectrum of genes. In insects, the principal steroid hormones, ecdysteroids, trigger the expression of thousands of genes through a cascade of transcription factors (TFs) to coordinate developmental transitions such as larval molting and metamorphosis. However, whether ecdysteroid signaling can bypass transcriptional hierarchies to exert its function in individual developmental processes is unclear. Here, we report that a single non-TF effector gene mediates the transcriptional output of ecdysteroid signaling in Drosophila myoblast fusion, a critical step in muscle development and differentiation. Specifically, we show that the 20-hydroxyecdysone (commonly referred to as "ecdysone") secreted from an extraembryonic tissue, amnioserosa, acts on embryonic muscle cells to directly activate the expression of antisocial (ants), which encodes an essential scaffold protein enriched at the fusogenic synapse. Not only is ants transcription directly regulated by the heterodimeric ecdysone receptor complex composed of ecdysone receptor (EcR) and ultraspiracle (USP) via ecdysone-response elements but also more strikingly, expression of ants alone is sufficient to rescue the myoblast fusion defect in ecdysone signaling-deficient mutants. We further show that EcR/USP and a muscle-specific TF Twist synergistically activate ants expression in vitro and in vivo. Taken together, our study provides the first example of a steroid hormone directly activating the expression of a single key non-TF effector gene to regulate a developmental process via inter-organ signaling and provides a new paradigm for understanding steroid hormone signaling in other developmental and physiological processes.
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Affiliation(s)
- Zhi-Rong Ruan
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Ze Yu
- McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Chao Xing
- McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Bioinformatics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Elizabeth H Chen
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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2
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Togashi H, Davis SR, Sato M. From soap bubbles to multicellular organisms: Unraveling the role of cell adhesion and physical constraints in tile pattern formation and tissue morphogenesis. Dev Biol 2024; 506:1-6. [PMID: 37995916 DOI: 10.1016/j.ydbio.2023.11.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 11/13/2023] [Accepted: 11/17/2023] [Indexed: 11/25/2023]
Abstract
Tile patterns, in which numerous cells are arranged in a regular pattern, are found in a variety of multicellular organisms and play important functional roles. Such regular arrangements of cells are regulated by various cell adhesion molecules. On the other hand, cell shape is also known to be regulated by physical constraints similar to those of soap bubbles. In particular, circumference minimization plays an important role, and cell adhesion negatively affects this process, thereby regulating tissue morphogenesis based on physical properties. Here, we focus on the Drosophila compound eye and the mouse auditory epithelium, and summarize the mechanisms of tile pattern formation by cell adhesion molecules such as cadherins, Irre Cell Recognition Modules (IRMs), and nectins. Phenomena that cannot be explained by physical stability based on cortical tension alone have been reported in the tile pattern formation in the compound eye, suggesting that previously unexplored forces such as cellular concentric expansion force may play an important role. We would like to summarize perspectives for future research on the mechanisms of tissue morphogenesis.
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Affiliation(s)
- Hideru Togashi
- Laboratory of Molecular Pharmacology, Biosignal Research Center, Kobe University, Kobe 657-8501, Japan
| | - Steven Ray Davis
- Mathematical Neuroscience Unit, Institute for Frontier Science Initiative, Graduate School of Medical Sciences, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8640, Japan
| | - Makoto Sato
- Mathematical Neuroscience Unit, Institute for Frontier Science Initiative, Graduate School of Medical Sciences, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8640, Japan.
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3
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Carrasco-Rando M, Culi J, Campuzano S, Ruiz-Gómez M. An acytokinetic cell division creates PIP2-enriched membrane asymmetries leading to slit diaphragm assembly in Drosophila nephrocytes. Development 2023; 150:dev201708. [PMID: 37681291 PMCID: PMC10546876 DOI: 10.1242/dev.201708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Accepted: 08/31/2023] [Indexed: 09/09/2023]
Abstract
Vertebrate podocytes and Drosophila nephrocytes display slit diaphragms, specialised cell junctions that are essential for the execution of the basic excretory function of ultrafiltration. To elucidate the mechanisms of slit diaphragm assembly we have studied their formation in Drosophila embryonic garland nephrocytes. These cells of mesenchymal origin lack overt apical-basal polarity. We find that their initial membrane symmetry is broken by an acytokinetic cell division that generates PIP2-enriched domains at their equator. The PIP2-enriched equatorial cortex becomes a favourable domain for hosting slit diaphragm proteins and the assembly of the first slit diaphragms. Indeed, when this division is either prevented or forced to complete cytokinesis, the formation of diaphragms is delayed to larval stages. Furthermore, although apical polarity determinants also accumulate at the equatorial cortex, they do not appear to participate in the recruitment of slit diaphragm proteins. The mechanisms we describe allow the acquisition of functional nephrocytes in embryos, which may confer on them a biological advantage similar to the formation of the first vertebrate kidney, the pronephros.
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Affiliation(s)
- Marta Carrasco-Rando
- Centro de Biología Molecular Severo Ochoa, CSIC and UAM, Nicolás Cabrera 1, Cantoblanco 28049, Madrid, Spain
| | - Joaquim Culi
- Centro de Biología Molecular Severo Ochoa, CSIC and UAM, Nicolás Cabrera 1, Cantoblanco 28049, Madrid, Spain
| | - Sonsoles Campuzano
- Centro de Biología Molecular Severo Ochoa, CSIC and UAM, Nicolás Cabrera 1, Cantoblanco 28049, Madrid, Spain
| | - Mar Ruiz-Gómez
- Centro de Biología Molecular Severo Ochoa, CSIC and UAM, Nicolás Cabrera 1, Cantoblanco 28049, Madrid, Spain
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4
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Yang S, Johnson AN. The serine/threonine kinase Back seat driver prevents cell fusion to maintain cell identity. Dev Biol 2023; 495:35-41. [PMID: 36528051 PMCID: PMC11088746 DOI: 10.1016/j.ydbio.2022.12.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 11/23/2022] [Accepted: 12/13/2022] [Indexed: 12/23/2022]
Abstract
Cell fate specification is essential for every major event of embryogenesis, and subsequent cell maturation ensures individual cell types acquire specialized functions. The mechanisms that regulate cell fate specification have been studied exhaustively, and each technological advance in developmental biology ushers in a new era of studies aimed at uncovering the most fundamental processes by which cells acquire unique identities. What is less appreciated is that mechanisms are in place to ensure cell identity is maintained throughout the life of the organism. The body wall musculature in the Drosophila embryo is a well-established model to study cell fate specification, as each hemisegment in the embryo generates and maintains thirty muscles with distinct identities. Once specified, the thirty body wall muscles fuse with mononucleate muscle precursors that lack a specific identity to form multinucleate striated muscles. Multinucleate body wall muscles do not fuse with each other, which maintains a diversification of muscle cell identities. Here we show the serine/threonine kinase Back seat driver (Bsd) prevents inappropriate muscle fusion to maintain cell identity. Thus, the regulation of cell fusion is one mechanism that maintains cell identity.
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Affiliation(s)
- Shuo Yang
- Department of Developmental Biology Washington University School of Medicine St. Louis, MO 63110
| | - Aaron N. Johnson
- Department of Developmental Biology Washington University School of Medicine St. Louis, MO 63110
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5
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Cortés E, Pak JS, Özkan E. Structure and evolution of neuronal wiring receptors and ligands. Dev Dyn 2023; 252:27-60. [PMID: 35727136 PMCID: PMC10084454 DOI: 10.1002/dvdy.512] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Revised: 06/13/2022] [Accepted: 06/14/2022] [Indexed: 01/04/2023] Open
Abstract
One of the fundamental properties of a neuronal circuit is the map of its connections. The cellular and developmental processes that allow for the growth of axons and dendrites, selection of synaptic targets, and formation of functional synapses use neuronal surface receptors and their interactions with other surface receptors, secreted ligands, and matrix molecules. Spatiotemporal regulation of the expression of these receptors and cues allows for specificity in the developmental pathways that wire stereotyped circuits. The families of molecules controlling axon guidance and synapse formation are generally conserved across animals, with some important exceptions, which have consequences for neuronal connectivity. Here, we summarize the distribution of such molecules across multiple taxa, with a focus on model organisms, evolutionary processes that led to the multitude of such molecules, and functional consequences for the diversification or loss of these receptors.
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Affiliation(s)
- Elena Cortés
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA.,The Neuroscience Institute, University of Chicago, Chicago, Illinois, USA
| | - Joseph S Pak
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA.,The Neuroscience Institute, University of Chicago, Chicago, Illinois, USA
| | - Engin Özkan
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA.,The Neuroscience Institute, University of Chicago, Chicago, Illinois, USA
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6
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Lee Y, Wang M, Imamura K, Sato M. Quantitative analysis of the roles of IRM cell adhesion molecules in column formation in the fly brain. Dev Growth Differ 2023; 65:37-47. [PMID: 36534021 DOI: 10.1111/dgd.12834] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 11/20/2022] [Accepted: 11/25/2022] [Indexed: 12/23/2022]
Abstract
The Drosophila visual center shows columnar structures, basic structural and functional units of the brain, that are shared with the mammalian cerebral cortex. Visual information received in the ommatidia in the compound eye is transmitted to the columns in the brain. However, the developmental mechanisms of column formation are largely unknown. The Irre Cell Recognition Module (IRM) proteins are a family of immunoglobulin cell adhesion molecules. The four Drosophila IRM proteins are localized to the developing columns, the structure of which is affected in IRM mutants, suggesting that IRM proteins are essential for column formation. Since IRM proteins are cell adhesion molecules, they may regulate cell adhesion between columnar neurons. To test this possibility, we specifically knocked down IRM genes in columnar neurons and examined the defects in column formation. We developed a system that automatically extracts the individual column images and quantifies the column shape. Using this system, we demonstrated that IRM genes play critical roles in regulating column shape in a core columnar neuron, Mi1. We also show that their expression in the other columnar neurons, Mi4 and T4/5, is essential, suggesting that the interactions between IRM proteins and multiple neurons shape the columns in the fly brain.
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Affiliation(s)
- Yunfei Lee
- Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Japan
| | - Miaoxing Wang
- Mathematical Neuroscience Unit, Institute for Frontier Science Initiative, Kanazawa, Japan
| | - Kousuke Imamura
- Faculty of Electrical, Information and Communication Engineering, Institute of Science and Engineering, Kanazawa University, Kanazawa, Japan
| | - Makoto Sato
- Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Japan.,Mathematical Neuroscience Unit, Institute for Frontier Science Initiative, Kanazawa, Japan
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7
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Milosavljevic J, Lempicki C, Lang K, Heinkele H, Kampf LL, Leroy C, Chen M, Gerstner L, Spitz D, Wang M, Knob AU, Kayser S, Helmstädter M, Walz G, Pollak MR, Hermle T. Nephrotic Syndrome Gene TBC1D8B Is Required for Endosomal Maturation and Nephrin Endocytosis in Drosophila. J Am Soc Nephrol 2022; 33:2174-2193. [PMID: 36137753 PMCID: PMC9731638 DOI: 10.1681/asn.2022030275] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Accepted: 09/01/2022] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND Variants in TBC1D8B cause nephrotic syndrome. TBC1D8B is a GTPase-activating protein for Rab11 (RAB11-GAP) that interacts with nephrin, but how it controls nephrin trafficking or other podocyte functions remains unclear. METHODS We generated a stable deletion in Tbc1d8b and used microhomology-mediated end-joining for genome editing. Ex vivo functional assays utilized slit diaphragms in podocyte-like Drosophila nephrocytes. Manipulation of endocytic regulators and transgenesis of murine Tbc1d8b provided a comprehensive functional analysis of Tbc1d8b. RESULTS A null allele of Drosophila TBC1D8B exhibited a nephrocyte-restricted phenotype of nephrin mislocalization, similar to patients with isolated nephrotic syndrome who have variants in the gene. The protein was required for rapid nephrin turnover in nephrocytes and for endocytosis of nephrin induced by excessive Rab5 activity. The protein expressed from the Tbc1d8b locus bearing the edited tag predominantly localized to mature early and late endosomes. Tbc1d8b was required for endocytic cargo processing and degradation. Silencing Hrs, a regulator of endosomal maturation, phenocopied loss of Tbc1d8b. Low-level expression of murine TBC1D8B rescued loss of the Drosophila gene, indicating evolutionary conservation. Excessive murine TBC1D8B selectively disturbed nephrin dynamics. Finally, we discovered four novel TBC1D8B variants within a cohort of 363 patients with FSGS and validated a functional effect of two variants in Drosophila, suggesting a personalized platform for TBC1D8B-associated FSGS. CONCLUSIONS Variants in TBC1D8B are not infrequent among patients with FSGS. TBC1D8B, functioning in endosomal maturation and degradation, is essential for nephrin trafficking.
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Affiliation(s)
- Julian Milosavljevic
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | - Camille Lempicki
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | - Konrad Lang
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | - Helena Heinkele
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | - Lina L. Kampf
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | - Claire Leroy
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | - Mengmeng Chen
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | - Lea Gerstner
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | - Dominik Spitz
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | - Minxian Wang
- Division of Nephrology, Beth Israel Deaconess Medical Center, Boston, Massachusetts
- Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Andrea U. Knob
- Division of Nephrology, Beth Israel Deaconess Medical Center, Boston, Massachusetts
| | - Séverine Kayser
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | - Martin Helmstädter
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | - Gerd Walz
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
- CIBSS–Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany
| | - Martin R. Pollak
- Division of Nephrology, Beth Israel Deaconess Medical Center, Boston, Massachusetts
- Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Tobias Hermle
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
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8
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Lang K, Milosavljevic J, Heinkele H, Chen M, Gerstner L, Spitz D, Kayser S, Helmstädter M, Walz G, Köttgen M, Spracklen A, Poulton J, Hermle T. Selective endocytosis controls slit diaphragm maintenance and dynamics in Drosophila nephrocytes. eLife 2022; 11:79037. [PMID: 35876643 PMCID: PMC9355562 DOI: 10.7554/elife.79037] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 07/24/2022] [Indexed: 11/28/2022] Open
Abstract
The kidneys generate about 180 l of primary urine per day by filtration of plasma. An essential part of the filtration barrier is the slit diaphragm, a multiprotein complex containing nephrin as major component. Filter dysfunction typically manifests with proteinuria and mutations in endocytosis regulating genes were discovered as causes of proteinuria. However, it is unclear how endocytosis regulates the slit diaphragm and how the filtration barrier is maintained without either protein leakage or filter clogging. Here, we study nephrin dynamics in podocyte-like nephrocytes of Drosophila and show that selective endocytosis either by dynamin- or flotillin-mediated pathways regulates a stable yet highly dynamic architecture. Short-term manipulation of endocytic functions indicates that dynamin-mediated endocytosis of ectopic nephrin restricts slit diaphragm formation spatially while flotillin-mediated turnover of nephrin within the slit diaphragm is needed to maintain filter permeability by shedding of molecules bound to nephrin in endosomes. Since slit diaphragms cannot be studied in vitro and are poorly accessible in mouse models, this is the first analysis of their dynamics within the slit diaphragm multiprotein complex. Identification of the mechanisms of slit diaphragm maintenance will help to develop novel therapies for proteinuric renal diseases that are frequently limited to symptomatic treatment.
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Affiliation(s)
- Konrad Lang
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | | | - Helena Heinkele
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Mengmeng Chen
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Lea Gerstner
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Dominik Spitz
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Severine Kayser
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | | | - Gerd Walz
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Michael Köttgen
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Andrew Spracklen
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - John Poulton
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - Tobias Hermle
- Department of Medicine, University of Freiburg, Freiburg, Germany
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9
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Bu L, Cripps RM. Promoter architecture of Drosophila genes regulated by Myocyte enhancer factor-2. PLoS One 2022; 17:e0271554. [PMID: 35862472 PMCID: PMC9302807 DOI: 10.1371/journal.pone.0271554] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 07/01/2022] [Indexed: 11/18/2022] Open
Abstract
To gain understanding into the mechanisms of transcriptional activation of muscle genes, we sought to determine if genes targeted by the myogenic transcription factor Myocyte enhancer factor-2 (MEF2) were enriched for specific core promoter elements. We identified 330 known MEF2 target promoters in Drosophila, and analyzed them for for the presence and location of 17 known consensus promoter sequences. As a control, we also searched all Drosophila RNA polymerase II-dependent promoters for the same sequences. We found that promoter motifs were readily detected in the MEF2 target dataset, and that many of them were slightly enriched in frequency compared to the control dataset. A prominent sequence over-represented in the MEF2 target genes was NDM2, that appeared in over 50% of MEF2 target genes and was 2.5-fold over-represented in MEF2 targets compared to background. To test the functional significance of NDM2, we identified two promoters containing a single copy of NDM2 plus an upstream MEF2 site, and tested the activity of these promoters in vivo. Both the sticks and stones and Kahuli fragments showed strong skeletal myoblast-specific expression of a lacZ reporter in embryos. However, the timing and level of reporter expression was unaffected when the NDM2 site in either element was mutated. These studies identify variations in promoter architecture for a set of regulated genes compared to all RNA polymerase II-dependent genes, and underline the potential redundancy in the activities of some core promoter elements.
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Affiliation(s)
- Lijing Bu
- Department of Biology and Center for Evolutionary and Theoretical Immunology, University of New Mexico, Albuquerque, NM, United States of America
| | - Richard M. Cripps
- Department of Biology, San Diego State University, San Diego, CA, United States of America
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10
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Luo Z, Shi J, Pandey P, Ruan ZR, Sevdali M, Bu Y, Lu Y, Du S, Chen EH. The cellular architecture and molecular determinants of the zebrafish fusogenic synapse. Dev Cell 2022; 57:1582-1597.e6. [PMID: 35709765 PMCID: PMC10180866 DOI: 10.1016/j.devcel.2022.05.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 04/04/2022] [Accepted: 05/20/2022] [Indexed: 11/03/2022]
Abstract
Myoblast fusion is an indispensable process in skeletal muscle development and regeneration. Studies in Drosophila led to the discovery of the asymmetric fusogenic synapse, in which one cell invades its fusion partner with actin-propelled membrane protrusions to promote fusion. However, the timing and sites of vertebrate myoblast fusion remain elusive. Here, we show that fusion between zebrafish fast muscle cells is mediated by an F-actin-enriched invasive structure. Two cell adhesion molecules, Jam2a and Jam3b, are associated with the actin structure, with Jam2a being the major organizer. The Arp2/3 actin nucleation-promoting factors, WAVE and WASP-but not the bipartite fusogenic proteins, Myomaker or Myomixer-promote the formation of the invasive structure. Moreover, the convergence of fusogen-containing microdomains and the invasive protrusions is a prerequisite for cell membrane fusion. Thus, our study provides unprecedented insights into the cellular architecture and molecular determinants of the asymmetric fusogenic synapse in an intact vertebrate animal.
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Affiliation(s)
- Zhou Luo
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jun Shi
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
| | - Pratima Pandey
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Zhi-Rong Ruan
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Maria Sevdali
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Ye Bu
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Yue Lu
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Shaojun Du
- Institute of Marine and Environmental Technology, Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Elizabeth H Chen
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA; Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA; Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA; Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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11
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Bali N, Lee HK(P, Zinn K. Sticks and Stones, a conserved cell surface ligand for the Type IIa RPTP Lar, regulates neural circuit wiring in Drosophila. eLife 2022; 11:e71469. [PMID: 35356892 PMCID: PMC9000958 DOI: 10.7554/elife.71469] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2021] [Accepted: 03/31/2022] [Indexed: 11/13/2022] Open
Abstract
Type IIa receptor-like protein tyrosine phosphatases (RPTPs) are essential for neural development. They have cell adhesion molecule (CAM)-like extracellular domains that interact with cell-surface ligands and coreceptors. We identified the immunoglobulin superfamily CAM Sticks and Stones (Sns) as a new partner for the Drosophila Type IIa RPTP Lar. Lar and Sns bind to each other in embryos and in vitro, and the human Sns ortholog, Nephrin, binds to human Type IIa RPTPs. Genetic analysis shows that Lar and Sns function together to regulate larval neuromuscular junction development, axon guidance in the mushroom body (MB), and innervation of the optic lobe (OL) medulla by R7 photoreceptors. In the neuromuscular system, Lar and Sns are both required in motor neurons, and may function as coreceptors. In the MB and OL, however, the relevant Lar-Sns interactions are in trans (between neurons), so Sns functions as a Lar ligand in these systems.
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Affiliation(s)
- Namrata Bali
- Division of Biology and Biological Engineering, California Institute of TechnologyPasadenaUnited States
| | - Hyung-Kook (Peter) Lee
- Division of Biology and Biological Engineering, California Institute of TechnologyPasadenaUnited States
| | - Kai Zinn
- Division of Biology and Biological Engineering, California Institute of TechnologyPasadenaUnited States
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12
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Aase-Remedios ME, Coll-Lladó C, Ferrier DEK. Amphioxus muscle transcriptomes reveal vertebrate-like myoblast fusion genes and a highly conserved role of insulin signalling in the metabolism of muscle. BMC Genomics 2022; 23:93. [PMID: 35105312 PMCID: PMC8805411 DOI: 10.1186/s12864-021-08222-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Accepted: 11/25/2021] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND The formation and functioning of muscles are fundamental aspects of animal biology, and the evolution of 'muscle genes' is central to our understanding of this tissue. Feeding-fasting-refeeding experiments have been widely used to assess muscle cellular and metabolic responses to nutrition. Though these studies have focused on vertebrate models and only a few invertebrate systems, they have found similar processes are involved in muscle degradation and maintenance. Motivation for these studies stems from interest in diseases whose pathologies involve muscle atrophy, a symptom also triggered by fasting, as well as commercial interest in the muscle mass of animals kept for consumption. Experimentally modelling atrophy by manipulating nutritional state causes muscle mass to be depleted during starvation and replenished with refeeding so that the genetic mechanisms controlling muscle growth and degradation can be understood. RESULTS Using amphioxus, the earliest branching chordate lineage, we address the gap in previous work stemming from comparisons between distantly related vertebrate and invertebrate models. Our amphioxus feeding-fasting-refeeding muscle transcriptomes reveal a highly conserved myogenic program and that the pro-orthologues of many vertebrate myoblast fusion genes were present in the ancestral chordate, despite these invertebrate chordates having unfused mononucleate myocytes. We found that genes differentially expressed between fed and fasted amphioxus were orthologous to the genes that respond to nutritional state in vertebrates. This response is driven in a large part by the highly conserved IGF/Akt/FOXO pathway, where depleted nutrient levels result in activation of FOXO, a transcription factor with many autophagy-related gene targets. CONCLUSION Reconstruction of these gene networks and pathways in amphioxus muscle provides a key point of comparison between the distantly related groups assessed thus far, significantly refining the reconstruction of the ancestral state for chordate myoblast fusion genes and identifying the extensive role of duplicated genes in the IGF/Akt/FOXO pathway across animals. Our study elucidates the evolutionary trajectory of muscle genes as they relate to the increased complexity of vertebrate muscles and muscle development.
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Affiliation(s)
- Madeleine E Aase-Remedios
- The Scottish Oceans Institute, Gatty Marine Laboratory, School of Biology, University of St Andrews, St Andrews, Fife, KY16 8LB, UK
| | - Clara Coll-Lladó
- The Scottish Oceans Institute, Gatty Marine Laboratory, School of Biology, University of St Andrews, St Andrews, Fife, KY16 8LB, UK
| | - David E K Ferrier
- The Scottish Oceans Institute, Gatty Marine Laboratory, School of Biology, University of St Andrews, St Andrews, Fife, KY16 8LB, UK.
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13
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Drosophila melanogaster: A Model System to Study Distinct Genetic Programs in Myoblast Fusion. Cells 2022; 11:cells11030321. [PMID: 35159130 PMCID: PMC8834112 DOI: 10.3390/cells11030321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2021] [Revised: 01/04/2022] [Accepted: 01/05/2022] [Indexed: 11/25/2022] Open
Abstract
Muscle fibers are multinucleated cells that arise during embryogenesis through the fusion of mononucleated myoblasts. Myoblast fusion is a lifelong process that is crucial for the growth and regeneration of muscles. Understanding the molecular mechanism of myoblast fusion may open the way for novel therapies in muscle wasting and weakness. Recent reports in Drosophila and mammals have provided new mechanistic insights into myoblast fusion. In Drosophila, muscle formation occurs twice: during embryogenesis and metamorphosis. A fundamental feature is the formation of a cell–cell communication structure that brings the apposing membranes into close proximity and recruits possible fusogenic proteins. However, genetic studies suggest that myoblast fusion in Drosophila is not a uniform process. The complexity of the players involved in myoblast fusion can be modulated depending on the type of muscle that is formed. In this review, we introduce the different types of multinucleated muscles that form during Drosophila development and provide an overview in advances that have been made to understand the mechanism of myoblast fusion. Finally, we will discuss conceptual frameworks in cell–cell fusion in Drosophila and mammals.
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14
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Valer FB, Spegiorim GC, Espreafico EM, Ramos RGP. The IRM cell adhesion molecules Hibris, Kin of irre and Roughest control egg morphology by modulating ovarian muscle contraction in Drosophila. JOURNAL OF INSECT PHYSIOLOGY 2022; 136:104344. [PMID: 34896373 DOI: 10.1016/j.jinsphys.2021.104344] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 12/03/2021] [Accepted: 12/06/2021] [Indexed: 06/14/2023]
Abstract
The Irre Cell Recognition Module (IRM) is an evolutionarily conserved group of transmembrane glycoproteins required for cell-cell recognition and adhesion in metazoan development. In Drosophila melanogaster ovaries, four members of this group - Roughest (Rst), Kin of irre (Kirre), Hibris (Hbs) and Sticks and stones (Sns) - play important roles in germ cell encapsulation and muscle sheath organization during early pupal stages, as well as in the progression to late oogenesis in the adult. Females carrying some of the mutant rst alleles are viable but sterile, and previous work from our laboratory had identified defects in the organization of the peritoneal and epithelial muscle sheaths of these mutants that could underlie their sterile phenotype. In this study, besides further characterizing the sterility phenotype associated with rst mutants, we investigated the role of the IRM molecules Rst, Kirre and Hbs in maintaining the functionality of the ovarian muscle sheaths. We found that knocking down any of the three genes in these structures, either individually or in double heterozygous combinations, not only decreases contraction frequency but also irregularly increases contraction amplitude. Furthermore, these alterations can significantly impact the morphology of eggs laid by IRM-depleted females demonstrating a hitherto unknown role of IRM molecules in egg morphogenesis.
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Affiliation(s)
- Felipe Berti Valer
- Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Giulia Covolo Spegiorim
- Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Enilza Maria Espreafico
- Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
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15
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Abstract
Cell-cell fusion is indispensable for creating life and building syncytial tissues and organs. Ever since the discovery of cell-cell fusion, how cells join together to form zygotes and multinucleated syncytia has remained a fundamental question in cell and developmental biology. In the past two decades, Drosophila myoblast fusion has been used as a powerful genetic model to unravel mechanisms underlying cell-cell fusion in vivo. Many evolutionarily conserved fusion-promoting factors have been identified and so has a surprising and conserved cellular mechanism. In this review, we revisit key findings in Drosophila myoblast fusion and highlight the critical roles of cellular invasion and resistance in driving cell membrane fusion.
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Affiliation(s)
- Donghoon M Lee
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA;
| | - Elizabeth H Chen
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA;
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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16
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Kampf LL, Schneider R, Gerstner L, Thünauer R, Chen M, Helmstädter M, Amar A, Onuchic-Whitford AC, Loza Munarriz R, Berdeli A, Müller D, Schrezenmeier E, Budde K, Mane S, Laricchia KM, Rehm HL, MacArthur DG, Lifton RP, Walz G, Römer W, Bergmann C, Hildebrandt F, Hermle T. TBC1D8B Mutations Implicate RAB11-Dependent Vesicular Trafficking in the Pathogenesis of Nephrotic Syndrome. J Am Soc Nephrol 2019; 30:2338-2353. [PMID: 31732614 DOI: 10.1681/asn.2019040414] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Accepted: 08/07/2019] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Mutations in about 50 genes have been identified as monogenic causes of nephrotic syndrome, a frequent cause of CKD. These genes delineated the pathogenetic pathways and rendered significant insight into podocyte biology. METHODS We used whole-exome sequencing to identify novel monogenic causes of steroid-resistant nephrotic syndrome (SRNS). We analyzed the functional significance of an SRNS-associated gene in vitro and in podocyte-like Drosophila nephrocytes. RESULTS We identified hemizygous missense mutations in the gene TBC1D8B in five families with nephrotic syndrome. Coimmunoprecipitation assays indicated interactions between TBC1D8B and active forms of RAB11. Silencing TBC1D8B in HEK293T cells increased basal autophagy and exocytosis, two cellular functions that are independently regulated by RAB11. This suggests that TBC1D8B plays a regulatory role by inhibiting endogenous RAB11. Coimmunoprecipitation assays showed TBC1D8B also interacts with the slit diaphragm protein nephrin, and colocalizes with it in immortalized cell lines. Overexpressed murine Tbc1d8b with patient-derived mutations had lower affinity for endogenous RAB11 and nephrin compared with wild-type Tbc1d8b protein. Knockdown of Tbc1d8b in Drosophila impaired function of the podocyte-like nephrocytes, and caused mistrafficking of Sns, the Drosophila ortholog of nephrin. Expression of Rab11 RNAi in nephrocytes entailed defective delivery of slit diaphragm protein to the membrane, whereas RAB11 overexpression revealed a partial phenotypic overlap to Tbc1d8b loss of function. CONCLUSIONS Novel mutations in TBC1D8B are monogenic causes of SRNS. This gene inhibits RAB11. Our findings suggest that RAB11-dependent vesicular nephrin trafficking plays a role in the pathogenesis of nephrotic syndrome.
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Affiliation(s)
- Lina L Kampf
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | - Ronen Schneider
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Lea Gerstner
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | - Roland Thünauer
- Signalling Research Centres BIOSS and CIBSS and Faculty of Biology, University of Freiburg, Freiburg, Germany.,Advanced Light and Fluorescence Microscopy Facility, Centre for Structural Systems Biology (CSSB) and University of Hamburg, Hamburg, Germany
| | - Mengmeng Chen
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | - Martin Helmstädter
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | - Ali Amar
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Ana C Onuchic-Whitford
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts.,Renal Division, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
| | | | - Afig Berdeli
- Department of Pediatrics, Molecular Medicine Laboratory, Ege University, Izmir, Turkey
| | - Dominik Müller
- Department of Pediatric Nephrology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Eva Schrezenmeier
- Department of Nephrology and Medical Intensive Care, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Klemens Budde
- Department of Nephrology and Medical Intensive Care, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Shrikant Mane
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut
| | - Kristen M Laricchia
- Broad Center for Mendelian Genomics, Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge
| | - Heidi L Rehm
- Broad Center for Mendelian Genomics, Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge
| | - Daniel G MacArthur
- Broad Center for Mendelian Genomics, Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge
| | - Richard P Lifton
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut.,Laboratory of Human Genetics and Genomics, The Rockefeller University, New York, New York
| | - Gerd Walz
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | - Winfried Römer
- Signalling Research Centres BIOSS and CIBSS and Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Carsten Bergmann
- Center for Human Genetics, Mainz, Germany.,Center for Human Genetics, Bioscientia, Ingelheim, Germany; and.,Department of Medicine, University Hospital Freiburg, Freiburg, Germany
| | - Friedhelm Hildebrandt
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts;
| | - Tobias Hermle
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany;
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17
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Abstract
Cell-cell fusion is a fundamental process underlying fertilization, development, regeneration and physiology of metazoans. It is a multi-step process involving cell recognition and adhesion, actin cytoskeletal rearrangements, fusogen engagement, lipid mixing and fusion pore formation, ultimately resulting in the integration of two fusion partners. Here, we focus on the asymmetric actin cytoskeletal rearrangements at the site of fusion, known as the fusogenic synapse, which was first discovered during myoblast fusion in Drosophila embryos and later also found in mammalian muscle and non-muscle cells. At the asymmetric fusogenic synapse, actin-propelled invasive membrane protrusions from an attacking fusion partner trigger actomyosin-based mechanosensory responses in the receiving cell. The interplay between the invasive and resisting forces generated by the two fusion partners puts the fusogenic synapse under high mechanical tension and brings the two cell membranes into close proximity, promoting the engagement of fusogens to initiate fusion pore formation. In this Cell Science at a Glance article and the accompanying poster, we highlight the molecular, cellular and biophysical events at the asymmetric fusogenic synapse using Drosophila myoblast fusion as a model.
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Affiliation(s)
- Ji Hoon Kim
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Elizabeth H Chen
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX 75390, USA .,Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX 75390, USA
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18
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Huang Y, Wu S, Zhang J, Wen H, Zhang M, He F. Methylation status and expression patterns of myomaker gene play important roles in postnatal development in the Japanese flounder (Paralichthys olivaceus). Gen Comp Endocrinol 2019; 280:104-114. [PMID: 31002826 DOI: 10.1016/j.ygcen.2019.04.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 02/28/2019] [Accepted: 04/16/2019] [Indexed: 01/01/2023]
Abstract
Myomaker is a membrane protein that plays a crucial role in the fusion of myoblasts during muscle growth. DNA methylation, a significant factor, regulates gene expression. The aim of this study was to examine the methylation and mRNA expression patterns of the myomaker gene during 8 different postnatal developmental stages in the Japanese flounder (L: 7 days post hatch (dph); M1: 21 dph; M2: 28 dph; M3: 35 dph; J1: 90 dph; J2: 180 dph; A1: 24 months; A2: 36 months). Muscle tissue samples were taken from Japanese flounder at different postnatal development stages to measure the extent of DNA methylation and gene expression. Methylation level in the promoter and exon 1 of myomaker was measured using bisulfite sequencing, and the relative expression of myomaker during each developmental stage was measured by quantitative PCR. The relative expression levels of myomaker were up-regulated from stages L to M2, M3 to J2, and methylation of myomaker was negatively correlated with mRNA expression. Furthermore, the CpG site located at -26 bp in the promoter was the lowest methylated region in all developmental stages. These results offer a basis for understanding the mechanism by which myomaker regulates muscle formation during postnatal development.
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Affiliation(s)
- Yajuan Huang
- Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, China
| | - Shuxian Wu
- Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, China
| | - Jingru Zhang
- Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, China
| | - Haishen Wen
- Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, China
| | - Meizhao Zhang
- Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, China
| | - Feng He
- Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, China.
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19
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Brukman NG, Uygur B, Podbilewicz B, Chernomordik LV. How cells fuse. J Cell Biol 2019; 218:1436-1451. [PMID: 30936162 PMCID: PMC6504885 DOI: 10.1083/jcb.201901017] [Citation(s) in RCA: 113] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 03/05/2019] [Accepted: 03/08/2019] [Indexed: 12/11/2022] Open
Abstract
Brukman et al. review cell–cell fusion mechanisms, focusing on the identity of the fusogens that mediate these processes and the regulation of their activities. Cell–cell fusion remains the least understood type of membrane fusion process. However, the last few years have brought about major advances in understanding fusion between gametes, myoblasts, macrophages, trophoblasts, epithelial, cancer, and other cells in normal development and in diseases. While different cell fusion processes appear to proceed via similar membrane rearrangements, proteins that have been identified as necessary and sufficient for cell fusion (fusogens) use diverse mechanisms. Some fusions are controlled by a single fusogen; other fusions depend on several proteins that either work together throughout the fusion pathway or drive distinct stages. Furthermore, some fusions require fusogens to be present on both fusing membranes, and in other fusions, fusogens have to be on only one of the membranes. Remarkably, some of the proteins that fuse cells also sculpt single cells, repair neurons, promote scission of endocytic vesicles, and seal phagosomes. In this review, we discuss the properties and diversity of the known proteins mediating cell–cell fusion and highlight their different working mechanisms in various contexts.
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Affiliation(s)
- Nicolas G Brukman
- Department of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Berna Uygur
- Section on Membrane Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD
| | | | - Leonid V Chernomordik
- Section on Membrane Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD
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20
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Si Y, Wen H, Du S. Genetic Mutations in jamb, jamc, and myomaker Revealed Different Roles on Myoblast Fusion and Muscle Growth. MARINE BIOTECHNOLOGY (NEW YORK, N.Y.) 2019; 21:111-123. [PMID: 30467785 PMCID: PMC6467518 DOI: 10.1007/s10126-018-9865-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Accepted: 11/15/2018] [Indexed: 05/08/2023]
Abstract
Myoblast fusion is a vital step for skeletal muscle development, growth, and regeneration. Loss of Jamb, Jamc, or Myomaker (Mymk) function impaired myoblast fusion in zebrafish embryos. In addition, mymk mutation hampered fish muscle growth. However, the effect of Jamb and Jamc deficiency on fish muscle growth is not clear. Moreover, whether jamb;jamc and jamb;mymk double mutations have stronger effects on myoblast fusion and muscle growth remains to be investigated. Here, we characterized the muscle development and growth in jamb, jamc, and mymk single and double mutants in zebrafish. We found that although myoblast fusion was compromised in jamb and jamc single or jamb;jamc double mutants, these mutant fish showed no defect in muscle cell fusion during muscle growth. The mutant fish were able to grow into adults that were indistinguishable from the wild-type sibling. In contrast, the jamb;mymk double mutants exhibited a stronger muscle phenotype compared to the jamb and jamc single and double mutants. The jamb;mymk double mutant showed reduced growth and partial lethality, similar to a mymk single mutant. Single fiber analysis of adult skeletal myofibers revealed that jamb, jamc, or jamb;jamc mutants contained mainly multinucleated myofibers, whereas jamb;mymk double mutants contained mostly mononucleated fibers. Significant intramuscular adipocyte infiltration was found in skeletal muscles of the jamb;mymk mutant. Collectively, these studies demonstrate that although Jamb, Jamc, and Mymk are all involved in myoblast fusion during early myogenesis, they have distinct roles in myoblast fusion during muscle growth. While Mymk is essential for myoblast fusion during both muscle development and growth, Jamb and Jamc are dispensable for myoblast fusion during muscle growth.
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MESH Headings
- Animals
- Animals, Genetically Modified
- Cell Communication
- Cell Differentiation
- Cell Fusion
- Embryo, Nonmammalian
- Gene Expression Regulation, Developmental
- Junctional Adhesion Molecule B/deficiency
- Junctional Adhesion Molecule B/genetics
- Membrane Proteins/deficiency
- Membrane Proteins/genetics
- Muscle Development/genetics
- Muscle Fibers, Skeletal/cytology
- Muscle Fibers, Skeletal/metabolism
- Muscle Proteins/deficiency
- Muscle Proteins/genetics
- Muscle, Skeletal/cytology
- Muscle, Skeletal/growth & development
- Muscle, Skeletal/metabolism
- Mutation
- Myoblasts/cytology
- Myoblasts/metabolism
- Receptors, Cell Surface/deficiency
- Receptors, Cell Surface/genetics
- Zebrafish/genetics
- Zebrafish/growth & development
- Zebrafish/metabolism
- Zebrafish Proteins/deficiency
- Zebrafish Proteins/genetics
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Affiliation(s)
- Yufeng Si
- Department of Biochemistry and Molecular Biology, Institute of Marine and Environmental Technology, University of Maryland School of Medicine, 701 East Pratt Street, Baltimore, MD, 21202, USA
- The Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao, 266003, China
| | - Haishen Wen
- The Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao, 266003, China
| | - Shaojun Du
- Department of Biochemistry and Molecular Biology, Institute of Marine and Environmental Technology, University of Maryland School of Medicine, 701 East Pratt Street, Baltimore, MD, 21202, USA.
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21
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Naa15 knockdown enhances c2c12 myoblast fusion and induces defects in zebrafish myotome morphogenesis. Comp Biochem Physiol B Biochem Mol Biol 2018; 228:61-67. [PMID: 30502388 DOI: 10.1016/j.cbpb.2018.11.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Revised: 11/16/2018] [Accepted: 11/21/2018] [Indexed: 11/21/2022]
Abstract
The understanding of muscle tissue formation and regeneration is essential for the development of therapeutic approaches to treat muscle diseases or loss of muscle mass and strength during ageing or cancer. One of the critical steps in muscle formation is the fusion of muscle cells to form or regenerate muscle fibres. To identify new genes controlling myoblast fusion, we performed a siRNA screen in c2c12 myoblasts. The genes identified during this screen were then studied in vivo by knockdown in zebrafish using morpholino. We found that N-alpha-acetyltransferase 15 (Naa15) knockdown enhanced c2c12 myoblast fusion, suggesting that Naa15 negatively regulates myogenic cell fusion. We identified two Naa15 orthologous genes in the zebrafish genome: Naa15a and Naa15b. These two orthologs were expressed in the myogenic domain of the somite. Knockdown of zebrafish Naa15a and Naa15b genes induced a "U"-shaped segmentation of the myotome and alteration of myotome boundaries, resulting in the formation of abnormally long myofibres spanning adjacent somites. Taken together, these results show that Naa15 regulates myotome formation and myogenesis in fish.
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22
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Valer FB, Machado MCR, Silva-Junior RMP, Ramos RGP. Expression of Hbs, Kirre, and Rst during Drosophila ovarian development. Genesis 2018; 56:e23242. [PMID: 30114331 DOI: 10.1002/dvg.23242] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2018] [Revised: 07/22/2018] [Accepted: 07/23/2018] [Indexed: 12/16/2022]
Abstract
The Irre cell-recognition module (IRM) is a group of evolutionarily conserved and structurally related transmembrane glycoproteins of the immunoglobulin superfamily. In Drosophila melanogaster, it comprises the products of the genes roughest (rst; also known as irreC-rst), kin-of-irre (kirre; also known as duf), sticks-and-stones (sns), and hibris (hbs). In this model organism, the behavior of this group of proteins as a partly redundant functional unit mediating selective cell recognition was demonstrated in a variety of developmental contexts, but their possible involvement in ovarian development and oogenesis has not been investigated, notwithstanding the fact that some rst mutant alleles are also female sterile. Here, we show that IRM genes are dynamically and, to some extent, coordinately transcribed in both pupal and adult ovaries. Additionally, the spatial distribution of Hbs, Kirre, and Rst proteins indicates that they perform cooperative, although largely nonredundant, functions. Finally, phenotypical characterization of three different female sterile rst alleles uncovered two temporally separated and functionally distinct requirements for this locus in ovarian development: one in pupa, essential for the organization of peritoneal and epithelial sheaths that maintain the structural integrity of the adult organ and another, in mature ovarioles, needed for the progression of oogenesis beyond stage 10.
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Affiliation(s)
- Felipe Berti Valer
- Department of Cellular and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Maiaro Cabral Rosa Machado
- Department of Cellular and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
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23
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Hermle T, Schneider R, Schapiro D, Braun DA, van der Ven AT, Warejko JK, Daga A, Widmeier E, Nakayama M, Jobst-Schwan T, Majmundar AJ, Ashraf S, Rao J, Finn LS, Tasic V, Hernandez JD, Bagga A, Jalalah SM, El Desoky S, Kari JA, Laricchia KM, Lek M, Rehm HL, MacArthur DG, Mane S, Lifton RP, Shril S, Hildebrandt F. GAPVD1 and ANKFY1 Mutations Implicate RAB5 Regulation in Nephrotic Syndrome. J Am Soc Nephrol 2018; 29:2123-2138. [PMID: 29959197 PMCID: PMC6065084 DOI: 10.1681/asn.2017121312] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 05/24/2018] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND Steroid-resistant nephrotic syndrome (SRNS) is a frequent cause of CKD. The discovery of monogenic causes of SRNS has revealed specific pathogenetic pathways, but these monogenic causes do not explain all cases of SRNS. METHODS To identify novel monogenic causes of SRNS, we screened 665 patients by whole-exome sequencing. We then evaluated the in vitro functional significance of two genes and the mutations therein that we discovered through this sequencing and conducted complementary studies in podocyte-like Drosophila nephrocytes. RESULTS We identified conserved, homozygous missense mutations of GAPVD1 in two families with early-onset NS and a homozygous missense mutation of ANKFY1 in two siblings with SRNS. GAPVD1 and ANKFY1 interact with the endosomal regulator RAB5. Coimmunoprecipitation assays indicated interaction between GAPVD1 and ANKFY1 proteins, which also colocalized when expressed in HEK293T cells. Silencing either protein diminished the podocyte migration rate. Compared with wild-type GAPVD1 and ANKFY1, the mutated proteins produced upon ectopic expression of GAPVD1 or ANKFY1 bearing the patient-derived mutations exhibited altered binding affinity for active RAB5 and reduced ability to rescue the knockout-induced defect in podocyte migration. Coimmunoprecipitation assays further demonstrated a physical interaction between nephrin and GAPVD1, and immunofluorescence revealed partial colocalization of these proteins in rat glomeruli. The patient-derived GAPVD1 mutations reduced nephrin-GAPVD1 binding affinity. In Drosophila, silencing Gapvd1 impaired endocytosis and caused mistrafficking of the nephrin ortholog. CONCLUSIONS Mutations in GAPVD1 and probably in ANKFY1 are novel monogenic causes of NS. The discovery of these genes implicates RAB5 regulation in the pathogenesis of human NS.
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Affiliation(s)
- Tobias Hermle
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
- Renal Division, University Medical Center Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Ronen Schneider
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - David Schapiro
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Daniela A Braun
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Amelie T van der Ven
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Jillian K Warejko
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Ankana Daga
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Eugen Widmeier
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Makiko Nakayama
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Tilman Jobst-Schwan
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Amar J Majmundar
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Shazia Ashraf
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Jia Rao
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Laura S Finn
- Department of Pathology, Seattle Children's Hospital, University of Washington, Seattle, Washington
| | - Velibor Tasic
- Department of Pediatric Nephrology, Medical Faculty Skopje, University Children's Hospital, Skopje, Macedonia
| | - Joel D Hernandez
- Department of Pediatric Nephrology, Providence Sacred Heart Medical Center and Children's Hospital, Spokane, Washington
| | - Arvind Bagga
- Division of Nephrology, All India Institute of Medical Sciences, New Delhi, India
| | | | - Sherif El Desoky
- Pediatric Nephrology Center of Excellence and Pediatric Department, Faculty of Medicine, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia
| | - Jameela A Kari
- Pediatric Nephrology Center of Excellence and Pediatric Department, Faculty of Medicine, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia
| | - Kristen M Laricchia
- Broad Center for Mendelian Genetics, Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, Massachusetts
| | - Monkol Lek
- Broad Center for Mendelian Genetics, Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, Massachusetts
| | - Heidi L Rehm
- Broad Center for Mendelian Genetics, Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, Massachusetts
| | - Daniel G MacArthur
- Broad Center for Mendelian Genetics, Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, Massachusetts
| | - Shrikant Mane
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut; and
| | - Richard P Lifton
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut; and
- Laboratory of Human Genetics and Genomics, The Rockefeller University, New York, New York
| | - Shirlee Shril
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Friedhelm Hildebrandt
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts;
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24
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Abstract
Polyploid cells, which contain multiple copies of the typically diploid genome, are widespread in plants and animals. Polyploidization can be developmentally programmed or stress induced, and arises from either cell-cell fusion or a process known as endoreplication, in which cells replicate their DNA but either fail to complete cytokinesis or to progress through M phase entirely. Polyploidization offers cells several potential fitness benefits, including the ability to increase cell size and biomass production without disrupting cell and tissue structure, and allowing improved cell longevity through higher tolerance to genomic stress and apoptotic signals. Accordingly, recent studies have uncovered crucial roles for polyploidization in compensatory cell growth during tissue regeneration in the heart, liver, epidermis and intestine. Here, we review current knowledge of the molecular pathways that generate polyploidy and discuss how polyploidization is used in tissue repair and regeneration.
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Affiliation(s)
| | - Bruce A Edgar
- Huntsman Cancer Institute, Salt Lake City, UT 84112, USA
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25
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Machado MCR, Valer FB, Couto-Lima CA, Ramos RGP. Transcriptional cross-regulation of Irre Cell Recognition Module (IRM) members in the Drosophila pupal retina. Mech Dev 2018; 154:193-202. [PMID: 30030087 DOI: 10.1016/j.mod.2018.07.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2018] [Revised: 06/26/2018] [Accepted: 07/16/2018] [Indexed: 12/13/2022]
Abstract
Cell adhesion molecules play a central role in morphogenesis, as they mediate the complex range of interactions between different cell types that result in their arrangement in multicellular organs and tissues. How their coordinated dynamic expression in space and time - an essential requirement for their function - is regulated at the genomic and transcriptional levels constitutes an important, albeit still little understood question. The Irre Cell Recognition Module (IRM) is a highly conserved phylogenetically group of structurally related single pass transmembrane glycoproteins belonging to the immunoglobulin superfamily that in Drosophila melanogaster are encoded by the genes roughest (rst), kin-of-irre (kirre), sticks-and-stones (sns) and hibris (hbs). Their cooperative and often partly redundant action are crucial to major developmental processes such axonal pathfinding, myoblast fusion and patterning of the pupal retina. In this latter system rst and kirre display a tightly regulated complementary transcriptional pattern so that lowering rst mRNA levels leads to a concomitant increase in kirre mRNA concentration. Here we investigated whether other IRM components are similarly co-regulated and the extent changes in their mRNA levels affect each other as well as their collective function in retinal patterning. Our results demonstrate that silencing any of the four IRM genes in 24% APF retinae changes the levels all other group members although only kirre and hbs mRNA levels are increased. Furthermore, expression, in a rst null background, of truncated versions of rst cDNA in which the portion encoding the intracellular domain has been partially or completely removed not only can still induce changes in mRNA levels of other IRM members but also result in Kirre mislocalization. Taken together, our data point to the presence of a highly precise and fine-tuned control mechanism coordinating IRM expression that may be crucial to the functional redundancy shown by its components during the patterning of the pupal retina.
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Affiliation(s)
- Maiaro Cabral Rosa Machado
- Department of Cellular and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Felipe Berti Valer
- Department of Cellular and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Carlos Antonio Couto-Lima
- Department of Cellular and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
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26
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Duan R, Kim JH, Shilagardi K, Schiffhauer ES, Lee DM, Son S, Li S, Thomas C, Luo T, Fletcher DA, Robinson DN, Chen EH. Spectrin is a mechanoresponsive protein shaping fusogenic synapse architecture during myoblast fusion. Nat Cell Biol 2018; 20:688-698. [PMID: 29802406 PMCID: PMC6397639 DOI: 10.1038/s41556-018-0106-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Accepted: 04/18/2018] [Indexed: 12/24/2022]
Abstract
Spectrin is a membrane skeletal protein best known for its structural role in maintaining cell shape and protecting cells from mechanical damage. Here, we report that α/βH-spectrin (βH is also called karst) dynamically accumulates and dissolves at the fusogenic synapse between fusing Drosophila muscle cells, where an attacking fusion partner invades its receiving partner with actin-propelled protrusions to promote cell fusion. Using genetics, cell biology, biophysics and mathematical modelling, we demonstrate that spectrin exhibits a mechanosensitive accumulation in response to shear deformation, which is highly elevated at the fusogenic synapse. The transiently accumulated spectrin network functions as a cellular fence to restrict the diffusion of cell-adhesion molecules and a cellular sieve to constrict the invasive protrusions, thereby increasing the mechanical tension of the fusogenic synapse to promote cell membrane fusion. Our study reveals a function of spectrin as a mechanoresponsive protein and has general implications for understanding spectrin function in dynamic cellular processes.
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Affiliation(s)
- Rui Duan
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Laboratory of Regenerative Medicine in Sports Science, School of Sports Science, South China Normal University, Guangzhou, China
| | - Ji Hoon Kim
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Khurts Shilagardi
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Eric S Schiffhauer
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Donghoon M Lee
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Sungmin Son
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA, USA
| | - Shuo Li
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Claire Thomas
- Departments of Biology and of Biochemistry and Molecular Biology, Penn State University, University Park, PA, USA
| | - Tianzhi Luo
- Department of Modern Mechanics, University of Science and Technology of China, Hefei, China
| | - Daniel A Fletcher
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA, USA
| | - Douglas N Robinson
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Elizabeth H Chen
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX, USA.
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27
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Muraleedharan S, Sam A, Skaer H, Inamdar MS. Networks that link cytoskeletal regulators and diaphragm proteins underpin filtration function in Drosophila nephrocytes. Exp Cell Res 2018; 364:234-242. [PMID: 29458174 PMCID: PMC5883325 DOI: 10.1016/j.yexcr.2018.02.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Revised: 02/06/2018] [Accepted: 02/15/2018] [Indexed: 11/25/2022]
Abstract
Insect nephrocytes provide a valuable model for kidney disease, as they are structurally and functionally homologous to mammalian kidney podocytes. They possess an exceptional macromolecular assembly, the nephrocyte diaphragm (ND), which serves as a filtration barrier and helps maintain tissue homeostasis by filtering out wastes and toxic products. However, the elements that maintain nephrocyte architecture and the ND are not understood. We show that Drosophila nephrocytes have a unique cytoplasmic cluster of F-actin, which is maintained by the microtubule cytoskeleton and Rho-GTPases. A balance of Rac1 and Cdc42 activity as well as proper microtubule organization and endoplasmic reticulum structure, are required to position the actin cluster. Further, ND proteins Sns and Duf also localize to this cluster and regulate organization of the actin and microtubule cytoskeleton. Perturbation of any of these inter-dependent components impairs nephrocyte ultrafiltration. Thus cytoskeletal components, Rho-GTPases and ND proteins work in concert to maintain the specialized nephrocyte architecture and function. Drosophila nephrocytes have a unique cytoplasmic cluster of F-actin. Microtubules, Rho-GTPases and endoplasmic reticulum position the actin cluster. Nephrocyte diaphragm proteins localize to and regulate actin cluster organization. Perturbation of any of these inter-dependent components impairs ultrafiltration.
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Affiliation(s)
- Simi Muraleedharan
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India
| | - Aksah Sam
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India
| | - Helen Skaer
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
| | - Maneesha S Inamdar
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India; Institute for Stem Cell Biology and Regenerative Medicine, GKVK, Bellary Road, Bangalore 560065, India.
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28
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Prince LM, Rand MD. Methylmercury exposure causes a persistent inhibition of myogenin expression and C2C12 myoblast differentiation. Toxicology 2018; 393:113-122. [PMID: 29104120 PMCID: PMC5757876 DOI: 10.1016/j.tox.2017.11.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 10/03/2017] [Accepted: 11/01/2017] [Indexed: 12/11/2022]
Abstract
Methylmercury (MeHg) is a ubiquitous environmental toxicant, best known for its selective targeting of the developing nervous system. MeHg exposure has been shown to cause motor deficits such as impaired gait and coordination, muscle weakness, and muscle atrophy, which have been associated with disruption of motor neurons. However, recent studies have suggested that muscle may also be a target of MeHg toxicity, both in the context of developmental myogenic events and of low-level chronic exposures affecting muscle wasting in aging. We therefore investigated the effects of MeHg on myotube formation, using the C2C12 mouse myoblast model. We found that MeHg inhibits both differentiation and fusion, in a concentration-dependent manner. Furthermore, MeHg specifically and persistently inhibits myogenin (MyoG), a transcription factor involved in myocyte differentiation, within the first six hours of exposure. MeHg-induced reduction in MyoG expression is contemporaneous with a reduction of a number of factors involved in mitochondrial biogenesis and mtDNA transcription and translation, which may implicate a role for mitochondria in mediating MeHg-induced change in the differentiation program. Unexpectedly, inhibition of myoblast differentiation with MeHg parallels inhibition of Notch receptor signaling. Our research establishes muscle cell differentiation as a target for MeHg toxicity, which may contribute to the underlying etiology of motor deficits with MeHg toxicity.
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Affiliation(s)
- Lisa M Prince
- University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Department of Environmental Medicine, Rochester, NY, 14642, USA.
| | - Matthew D Rand
- University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Department of Environmental Medicine, Rochester, NY, 14642, USA.
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29
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Prince LM, Rand MD. Notch Target Gene E(spl)mδ Is a Mediator of Methylmercury-Induced Myotoxicity in Drosophila. Front Genet 2018; 8:233. [PMID: 29379520 PMCID: PMC5775289 DOI: 10.3389/fgene.2017.00233] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 12/22/2017] [Indexed: 01/09/2023] Open
Abstract
Methylmercury (MeHg) is a ubiquitous environmental contaminant and neurotoxicant that has long been known to cause a variety of motor deficits. These motor deficits have primarily been attributed to MeHg targeting of developing neurons and induction of oxidative stress and calcium dysregulation. Few studies have looked at how MeHg may be affecting fundamental signaling mechanisms in development, particularly in developing muscle. Studies in Drosophila recently revealed that MeHg perturbs embryonic muscle formation and upregulates Notch target genes, reflected predominantly by expression of the downstream transcriptional repressor Enhancer of Split mdelta [E(spl)mδ]. An E(spl)mδ reporter gene shows expression primarily in the myogenic domain, and both MeHg exposure and genetic upregulation of E(spl)mδ can disrupt embryonic muscle development. Here, we tested the hypothesis that developing muscle is targeted by MeHg via upregulation of E(spl)mδ using genetic modulation of E(spl)mδ expression in combination with MeHg exposure in developing flies. Developmental MeHg exposure causes a decreased rate of eclosion that parallels gross disruption of indirect flight muscle (IFM) development. An increase in E(spl) expression across the pupal stages, with preferential E(spl)mδ upregulation occurring at early (p5) stages, is also observed. E(spl)mδ overexpression in myogenic lineages under the Mef2 promoter was seen to phenocopy eclosion and IFM effects of developmental MeHg exposure; whereas reduced expression of E(spl)mδ shows rescue of eclosion and IFM morphology effects of MeHg exposure. No effects were seen on eclosion with E(spl)mδ overexpression in neural and gut tissues. Our data indicate that muscle development is a target for MeHg and that E(spl)mδ is a muscle-specific mediator of this myotoxicity. This research advances our knowledge of the target pathways that mediate susceptibility to MeHg toxicity, as well as a potential muscle development-specific role for E(spl)mδ.
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Affiliation(s)
- Lisa M Prince
- Department of Environmental Medicine, School of Medicine and Dentistry, University of Rochester, Rochester, NY, United States
| | - Matthew D Rand
- Department of Environmental Medicine, School of Medicine and Dentistry, University of Rochester, Rochester, NY, United States
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30
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Abstract
Cell-cell fusion is essential for fertilization and organ development. Dedicated proteins known as fusogens are responsible for mediating membrane fusion. However, until recently, these proteins either remained unidentified or were poorly understood at the mechanistic level. Here, we review how fusogens surmount multiple energy barriers to mediate cell-cell fusion. We describe how early preparatory steps bring membranes to a distance of ∼10 nm, while fusogens act in the final approach between membranes. The mechanical force exerted by cell fusogens and the accompanying lipidic rearrangements constitute the hallmarks of cell-cell fusion. Finally, we discuss the relationship between viral and eukaryotic fusogens, highlight a classification scheme regrouping a superfamily of fusogens called Fusexins, and propose new questions and avenues of enquiry.
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Affiliation(s)
- Javier M Hernández
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, D-44227 Dortmund, Germany
| | - Benjamin Podbilewicz
- Department of Biology, Technion - Israel Institute of Technology, Haifa 32000, Israel
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31
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Drechsler M, Meyer H, Wilmes AC, Paululat A. APC/CFzr regulates cardiac and myoblast cell numbers and plays a crucial role during myoblast fusion. J Cell Sci 2018; 131:jcs.209155. [DOI: 10.1242/jcs.209155] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 05/30/2018] [Indexed: 11/20/2022] Open
Abstract
Somatic muscles are formed by the iterative fusion of myoblasts into muscle fibres. This process is driven by the recurrent recruitment of proteins to the cell membrane to induce F-actin nucleation at the fusion site. Although various proteins involved in myoblast fusion have been identified, knowledge about their sub-cellular regulation is rather elusive. We identified the anaphase-promoting complex (APC/C) adaptor Fizzy related (Fzr) as an essential regulator of heart and muscle development. We show that APC/CFzr regulates the fusion of myoblasts as well as mitotic exit of pericardial cells, cardioblasts and myoblasts. Surprisingly, over-proliferation is not causative for the observed fusion defects. Instead, fzr mutants exhibit smaller F-actin foci at the fusion site, and display reduced membrane breakdown between adjacent myoblasts. We show that lack of APC/CFzr causes the accumulation and mislocalisation of Rols and Duf, two proteins involved in the fusion process. Duf seems to serve as direct substrate of the APC/CFzr, and its destruction depends on the presence of distinct degron sequences. These novel findings indicate that protein destruction and turnover constitute major events during myoblast fusion.
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Affiliation(s)
- Maik Drechsler
- University of Osnabrück, Department of Zoology and Developmental Biology, Barbarastraße 11, 49076 Osnabrück, Germany
- Current address: University of Cambridge, Department of Zoology, CB2 3EJ, Cambridge, UK
| | - Heiko Meyer
- University of Osnabrück, Department of Zoology and Developmental Biology, Barbarastraße 11, 49076 Osnabrück, Germany
| | - Ariane C. Wilmes
- University of Osnabrück, Department of Zoology and Developmental Biology, Barbarastraße 11, 49076 Osnabrück, Germany
| | - Achim Paululat
- University of Osnabrück, Department of Zoology and Developmental Biology, Barbarastraße 11, 49076 Osnabrück, Germany
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32
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Deng S, Azevedo M, Baylies M. Acting on identity: Myoblast fusion and the formation of the syncytial muscle fiber. Semin Cell Dev Biol 2017; 72:45-55. [PMID: 29101004 DOI: 10.1016/j.semcdb.2017.10.033] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 10/25/2017] [Accepted: 10/30/2017] [Indexed: 12/25/2022]
Abstract
The study of Drosophila muscle development dates back to the middle of the last century. Since that time, Drosophila has proved to be an ideal system for studying muscle development, differentiation, function, and disease. As in humans, Drosophila muscle forms via a series of conserved steps, starting with muscle specification, myoblast fusion, attachment to tendon cells, interactions with motorneurons, and sarcomere and myofibril formation. The genes and mechanisms required for these processes share striking similarities to those found in humans. The highly tractable genetic system and imaging approaches available in Drosophila allow for an efficient interrogation of muscle biology and for application of what we learn to other systems. In this article, we review our current understanding of muscle development in Drosophila, with a focus on myoblast fusion, the process responsible for the generation of syncytial muscle cells. We also compare and contrast those genes required for fusion in Drosophila and vertebrates.
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Affiliation(s)
- Su Deng
- Program in Developmental Biology, Sloan Kettering Institute, New York, NY 10065, United States
| | - Mafalda Azevedo
- Program in Developmental Biology, Sloan Kettering Institute, New York, NY 10065, United States; Graduate Program in Basic and Applied Biology (GABBA), Institute of Biomedical Sciences Abel Salazar, University of Porto, Porto, Portugal
| | - Mary Baylies
- Program in Developmental Biology, Sloan Kettering Institute, New York, NY 10065, United States.
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33
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Bataillé L, Boukhatmi H, Frendo JL, Vincent A. Dynamics of transcriptional (re)-programming of syncytial nuclei in developing muscles. BMC Biol 2017; 15:48. [PMID: 28599653 PMCID: PMC5466778 DOI: 10.1186/s12915-017-0386-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 05/19/2017] [Indexed: 01/08/2023] Open
Abstract
Background A stereotyped array of body wall muscles enables precision and stereotypy of animal movements. In Drosophila, each syncytial muscle forms via fusion of one founder cell (FC) with multiple fusion competent myoblasts (FCMs). The specific morphology of each muscle, i.e. distinctive shape, orientation, size and skeletal attachment sites, reflects the specific combination of identity transcription factors (iTFs) expressed by its FC. Here, we addressed three questions: Are FCM nuclei naive? What is the selectivity and temporal sequence of transcriptional reprogramming of FCMs recruited into growing syncytium? Is transcription of generic myogenic and identity realisation genes coordinated during muscle differentiation? Results The tracking of nuclei in developing muscles shows that FCM nuclei are competent to be transcriptionally reprogrammed to a given muscle identity, post fusion. In situ hybridisation to nascent transcripts for FCM, FC-generic and iTF genes shows that this reprogramming is progressive, beginning by repression of FCM-specific genes in fused nuclei, with some evidence that FC nuclei retain specific characteristics. Transcription of identity realisation genes is linked to iTF activation and regulated at levels of both transcription initiation rate and period of transcription. The generic muscle differentiation programme is activated independently. Conclusions Transcription reprogramming of fused myoblast nuclei is progressive, such that nuclei within a syncytial fibre at a given time point during muscle development are heterogeneous with regards to specific gene transcription. This comprehensive view of the dynamics of transcriptional (re)programming of post-mitotic nuclei within syncytial cells provides a new framework for understanding the transcriptional control of the lineage diversity of multinucleated cells. Electronic supplementary material The online version of this article (doi:10.1186/s12915-017-0386-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Laetitia Bataillé
- Centre de Biologie du Développement (CBD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Hadi Boukhatmi
- Centre de Biologie du Développement (CBD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France.,Present address: Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3DY, UK
| | - Jean-Louis Frendo
- Centre de Biologie du Développement (CBD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France.
| | - Alain Vincent
- Centre de Biologie du Développement (CBD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France.
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34
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Morishita K, Anh Suong DN, Yoshida H, Yamaguchi M. The Drosophila DOCK family protein Sponge is required for development of the air sac primordium. Exp Cell Res 2017; 354:95-102. [PMID: 28341448 DOI: 10.1016/j.yexcr.2017.03.044] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2016] [Revised: 03/18/2017] [Accepted: 03/20/2017] [Indexed: 12/14/2022]
Abstract
Dedicator of cytokinesis (DOCK) family genes are known as DOCK1-DOCK11 in mammals. DOCK family proteins mainly regulate actin filament polymerization and/or depolymerization and are GEF proteins, which contribute to cellular signaling events by activating small G proteins. Sponge (Spg) is a Drosophila counterpart to mammalian DOCK3/DOCK4, and plays a role in embryonic central nervous system development, R7 photoreceptor cell differentiation, and adult thorax development. In order to conduct further functional analyses on Spg in vivo, we examined its localization in third instar larval wing imaginal discs. Immunostaining with purified anti-Spg IgG revealed that Spg mainly localized in the air sac primordium (ASP) in wing imaginal discs. Spg is therefore predicted to play an important role in the ASP. The specific knockdown of Spg by the breathless-GAL4 driver in tracheal cells induced lethality accompanied with a defect in ASP development and the induction of apoptosis. The monitoring of ERK signaling activity in wing imaginal discs by immunostaining with anti-diphospho-ERK IgG revealed reductions in the ERK signal cascade in Spg knockdown clones. Furthermore, the overexpression of D-raf suppressed defects in survival and the proliferation of cells in the ASP induced by the knockdown of Spg. Collectively, these results indicate that Spg plays a critical role in ASP development and tracheal cell viability that is mediated by the ERK signaling pathway.
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Affiliation(s)
- Kazushge Morishita
- Department of Applied Biology, The Center for Advanced Insect Research, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan
| | - Dang Ngoc Anh Suong
- Department of Applied Biology, The Center for Advanced Insect Research, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan
| | - Hideki Yoshida
- Department of Applied Biology, The Center for Advanced Insect Research, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan
| | - Masamitsu Yamaguchi
- Department of Applied Biology, The Center for Advanced Insect Research, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan.
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35
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Mendoza-García P, Hugosson F, Fallah M, Higgins ML, Iwasaki Y, Pfeifer K, Wolfstetter G, Varshney G, Popichenko D, Gergen JP, Hens K, Deplancke B, Palmer RH. The Zic family homologue Odd-paired regulates Alk expression in Drosophila. PLoS Genet 2017; 13:e1006617. [PMID: 28369060 PMCID: PMC5393633 DOI: 10.1371/journal.pgen.1006617] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 04/17/2017] [Accepted: 02/07/2017] [Indexed: 01/30/2023] Open
Abstract
The Anaplastic Lymphoma Kinase (Alk) receptor tyrosine kinase (RTK) plays a critical role in the specification of founder cells (FCs) in the Drosophila visceral mesoderm (VM) during embryogenesis. Reporter gene and CRISPR/Cas9 deletion analysis reveals enhancer regions in and upstream of the Alk locus that influence tissue-specific expression in the amnioserosa (AS), the VM and the epidermis. By performing high throughput yeast one-hybrid screens (Y1H) with a library of Drosophila transcription factors (TFs) we identify Odd-paired (Opa), the Drosophila homologue of the vertebrate Zic family of TFs, as a novel regulator of embryonic Alk expression. Further characterization identifies evolutionarily conserved Opa-binding cis-regulatory motifs in one of the Alk associated enhancer elements. Employing Alk reporter lines as well as CRISPR/Cas9-mediated removal of regulatory elements in the Alk locus, we show modulation of Alk expression by Opa in the embryonic AS, epidermis and VM. In addition, we identify enhancer elements that integrate input from additional TFs, such as Binou (Bin) and Bagpipe (Bap), to regulate VM expression of Alk in a combinatorial manner. Taken together, our data show that the Opa zinc finger TF is a novel regulator of embryonic Alk expression. The Alk receptor tyrosine kinase is employed repeatedly during Drosophila development to drive signaling events in a variety of tissues. The spatial and temporal expression pattern of the Alk gene is tightly regulated. Identifying factors that influence the expression of Alk is important to better understand how Alk signaling is controlled. In this paper we characterize cis-regulatory sequences in the Alk locus and the transcription factors that bind them to govern Alk expression in the Drosophila embryo. Using a robotic protein-DNA interaction assay, we identified the Zic family transcription factor Odd-paired as a factor that binds to regulatory elements in the Alk locus. Binding of Odd-paired to Alkcis-regulatory elements varies spatially, revealing a requirement for additional transcription factors such as the NK3 and FoxF orthologues Bagpipe and Biniou in a subset of Alk-expressing tissues. Our findings provide new insight into the dynamics underlying temporal and spatial regulation of the Alk receptor during embryogenesis.
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Affiliation(s)
- Patricia Mendoza-García
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Department of Molecular Biology, Umeå University, Umeå, Sweden
| | - Fredrik Hugosson
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Mahsa Fallah
- Department of Molecular Biology, Umeå University, Umeå, Sweden
| | - Michael L. Higgins
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, United States of America
| | - Yasuno Iwasaki
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, United States of America
| | - Kathrin Pfeifer
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Georg Wolfstetter
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Gaurav Varshney
- Department of Molecular Biology, Umeå University, Umeå, Sweden
| | | | - J. Peter Gergen
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, United States of America
| | - Korneel Hens
- Centre for Neural Circuits and Behaviour, University of Oxford, Oxford, United Kingdom
| | - Bart Deplancke
- Laboratory of Systems Biology and Genetics, Lausanne, Switzerland
| | - Ruth H. Palmer
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- * E-mail:
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Hermle T, Braun DA, Helmstädter M, Huber TB, Hildebrandt F. Modeling Monogenic Human Nephrotic Syndrome in the Drosophila Garland Cell Nephrocyte. J Am Soc Nephrol 2016; 28:1521-1533. [PMID: 27932481 DOI: 10.1681/asn.2016050517] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 11/05/2016] [Indexed: 11/03/2022] Open
Abstract
Steroid-resistant nephrotic syndrome is characterized by podocyte dysfunction. Drosophila garland cell nephrocytes are podocyte-like cells and thus provide a potential in vivo model in which to study the pathogenesis of nephrotic syndrome. However, relevant pathomechanisms of nephrotic syndrome have not been studied in nephrocytes. Here, we discovered that two Drosophila slit diaphragm proteins, orthologs of the human genes encoding nephrin and nephrin-like protein 1, colocalize within a fingerprint-like staining pattern that correlates with ultrastructural morphology. Using RNAi and conditional CRISPR/Cas9 in nephrocytes, we found this pattern depends on the expression of both orthologs. Tracer endocytosis by nephrocytes required Cubilin and reflected size selectivity analogous to that of glomerular function. Using RNAi and tracer endocytosis as a functional read-out, we screened Drosophila orthologs of human monogenic causes of nephrotic syndrome and observed conservation of the central pathogenetic alterations. We focused on the coenzyme Q10 (CoQ10) biosynthesis gene Coq2, the silencing of which disrupted slit diaphragm morphology. Restoration of CoQ10 synthesis by vanillic acid partially rescued the phenotypic and functional alterations induced by Coq2-RNAi. Notably, Coq2 colocalized with mitochondria, and Coq2 silencing increased the formation of reactive oxygen species (ROS). Silencing of ND75, a subunit of the mitochondrial respiratory chain that controls ROS formation independently of CoQ10, phenocopied the effect of Coq2-RNAi. Moreover, the ROS scavenger glutathione partially rescued the effects of Coq2-RNAi. In conclusion, Drosophila garland cell nephrocytes provide a model with which to study the pathogenesis of nephrotic syndrome, and ROS formation may be a pathomechanism of COQ2-nephropathy.
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Affiliation(s)
- Tobias Hermle
- Division of Nephrology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts;
| | - Daniela A Braun
- Division of Nephrology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Martin Helmstädter
- Renal Division, University Medical Center Freiburg, Freiburg, Germany, Faculty of Medicine, University of Freiburg, Freiburg, Germany; and
| | - Tobias B Huber
- Renal Division, University Medical Center Freiburg, Freiburg, Germany, Faculty of Medicine, University of Freiburg, Freiburg, Germany; and.,BIOSS Center for Biological Signalling Studies, Albert-Ludwigs-University Freiburg, Freiburg, Germany
| | - Friedhelm Hildebrandt
- Division of Nephrology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts;
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Hamp J, Löwer A, Dottermusch-Heidel C, Beck L, Moussian B, Flötenmeyer M, Önel SF. Drosophila Kette coordinates myoblast junction dissolution and the ratio of Scar-to-WASp during myoblast fusion. J Cell Sci 2016; 129:3426-36. [PMID: 27521427 PMCID: PMC5047678 DOI: 10.1242/jcs.175638] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 07/25/2016] [Indexed: 12/31/2022] Open
Abstract
The fusion of founder cells and fusion-competent myoblasts (FCMs) is crucial for muscle formation in Drosophila. Characteristic events of myoblast fusion include the recognition and adhesion of myoblasts, and the formation of branched F-actin by the Arp2/3 complex at the site of cell–cell contact. At the ultrastructural level, these events are reflected by the appearance of finger-like protrusions and electron-dense plaques that appear prior to fusion. Severe defects in myoblast fusion are caused by the loss of Kette (a homolog of Nap1 and Hem-2, also known as NCKAP1 and NCKAP1L, respectively), a member of the regulatory complex formed by Scar or WAVE proteins (represented by the single protein, Scar, in flies). kette mutants form finger-like protrusions, but the electron-dense plaques are extended. Here, we show that the electron-dense plaques in wild-type and kette mutant myoblasts resemble other electron-dense structures that are known to function as cellular junctions. Furthermore, analysis of double mutants and attempts to rescue the kette mutant phenotype with N-cadherin, wasp and genes of members of the regulatory Scar complex revealed that Kette has two functions during myoblast fusion. First, Kette controls the dissolution of electron-dense plaques. Second, Kette controls the ratio of the Arp2/3 activators Scar and WASp in FCMs. Summary: The Drosophila protein Kette is essential for myoblast fusion. It controls the dissolution of electron-dense plaques and the ratio of Scar and WASp proteins in fusion-competent myoblasts during fusion pore formation.
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Affiliation(s)
- Julia Hamp
- Philipps-Universität Marburg, FB Biologie, Entwicklungsbiologie, Karl-von-Frisch Str. 8, Marburg 35043, Germany
| | - Andreas Löwer
- Philipps-Universität Marburg, FB Biologie, Entwicklungsbiologie, Karl-von-Frisch Str. 8, Marburg 35043, Germany
| | | | - Lothar Beck
- Fachbereich Biologie, Spezielle Zoologie, Philipps-Universität Marburg, Karl-von-Frisch Str. 8, Marburg 35043, Germany
| | - Bernard Moussian
- Interfaculty Institute for Cell Biology, Section Animal Genetics, University of Tübingen, Tübingen 72076, Germany
| | - Matthias Flötenmeyer
- Max Planck Institute for Developmental Biology, Section Electron Microscopy, Tübingen 72076, Germany
| | - Susanne-Filiz Önel
- Philipps-Universität Marburg, FB Biologie, Entwicklungsbiologie, Karl-von-Frisch Str. 8, Marburg 35043, Germany
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Carrasco-Rando M, Atienza-Manuel A, Martín P, Burke R, Ruiz-Gómez M. Fear-of-intimacy mediated zinc transport controls the function of Zn-finger transcription factors involved in myogenesis. Development 2016; 143:1948-57. [DOI: 10.1242/dev.131953] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 03/31/2016] [Indexed: 12/17/2022]
Abstract
Zinc is a component of one tenth of all human proteins. Its cellular concentration is tightly regulated because its dyshomeostasis has catastrophic health consequences. Two families of zinc transporters control zinc homeostasis in organisms, but there is little information about their specific developmental roles. We show that the ZIP transporter fear-of-intimacy (foi) is necessary for the formation of Drosophila muscles. In foi mutants, myoblasts segregate normally, but their specification is affected, leading to the formation of a misshapen muscle pattern and distorted midgut. The observed phenotypes could be ascribed to the inactivation of specific zing-finger transcription factors (ZFTFs), supporting the hypothesis that they a consequence of a zinc intracellular depletion. Accordingly, foi phenotypes can be rescued by mesodermal expression of other ZIP members with similar subcellular localization. We propose that Foi acts mostly as a transporter to regulate zinc intracellular homeostasis, thereby impacting on the activity of ZFTFs that control specific developmental processes. Our results additionally suggest a possible explanation for the presence of large numbers of zinc transporters in organisms based on differences in ion transport specificity and/or degrees of activity among transporters.
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Affiliation(s)
- Marta Carrasco-Rando
- Centro de Biología Molecular Severo Ochoa, CSIC and UAM, C/ Nicolás Cabrera 1, 28049-Madrid, Spain
| | - Alexandra Atienza-Manuel
- Centro de Biología Molecular Severo Ochoa, CSIC and UAM, C/ Nicolás Cabrera 1, 28049-Madrid, Spain
| | - Paloma Martín
- Centro de Biología Molecular Severo Ochoa, CSIC and UAM, C/ Nicolás Cabrera 1, 28049-Madrid, Spain
| | - Richard Burke
- School of Biological Sciences, Monash University, Wellington Rd, Clayton, VIC 3800, Australia
| | - Mar Ruiz-Gómez
- Centro de Biología Molecular Severo Ochoa, CSIC and UAM, C/ Nicolás Cabrera 1, 28049-Madrid, Spain
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Kuckwa J, Fritzen K, Buttgereit D, Rothenbusch-Fender S, Renkawitz-Pohl R. A new level of plasticity: Drosophila smooth-like testes muscles compensate failure of myoblast fusion. Development 2015; 143:329-38. [PMID: 26657767 PMCID: PMC4725342 DOI: 10.1242/dev.126730] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Accepted: 11/28/2015] [Indexed: 12/26/2022]
Abstract
The testis of Drosophila resembles an individual testis tubule of mammals. Both are surrounded by a sheath of smooth muscles, which in Drosophila are multinuclear and originate from a pool of myoblasts that are set aside in the embryo and accumulate on the genital disc later in development. These muscle stem cells start to differentiate early during metamorphosis and give rise to all muscles of the inner male reproductive system. Shortly before the genital disc and the developing testes connect, multinuclear nascent myotubes appear on the anterior tips of the seminal vesicles. Here, we show that adhesion molecules are distinctly localized on the seminal vesicles; founder cell (FC)-like myoblasts express Dumbfounded (Duf) and Roughest (Rst), and fusion-competent myoblast (FCM)-like cells mainly express Sticks and stones (Sns). The smooth but multinuclear myotubes of the testes arose by myoblast fusion. RNAi-mediated attenuation of Sns or both Duf and Rst severely reduced the number of nuclei in the testes muscles. Duf and Rst probably act independently in this context. Despite reduced fusion in all of these RNAi-treated animals, myotubes migrated onto the testes, testes were shaped and coiled, muscle filaments were arranged as in the wild type and spermatogenesis proceeded normally. Hence, the testes muscles compensate for fusion defects so that the myofibres encircling the adult testes are indistinguishable from those of the wild type and male fertility is guaranteed. Summary:Drosophila testes muscles arise from stem cells and can compensate for fusion defects to safeguard fertility; this plasticity may compensate for the observed lack of satellite cells in Drosophila.
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Affiliation(s)
- Jessica Kuckwa
- Philipps-Universität Marburg, Fachbereich Biologie, Entwicklungsbiologie, Karl-von-Frisch Strasse 8, Marburg 35043, Germany
| | - Katharina Fritzen
- Philipps-Universität Marburg, Fachbereich Biologie, Entwicklungsbiologie, Karl-von-Frisch Strasse 8, Marburg 35043, Germany
| | - Detlev Buttgereit
- Philipps-Universität Marburg, Fachbereich Biologie, Entwicklungsbiologie, Karl-von-Frisch Strasse 8, Marburg 35043, Germany
| | - Silke Rothenbusch-Fender
- Philipps-Universität Marburg, Fachbereich Biologie, Entwicklungsbiologie, Karl-von-Frisch Strasse 8, Marburg 35043, Germany
| | - Renate Renkawitz-Pohl
- Philipps-Universität Marburg, Fachbereich Biologie, Entwicklungsbiologie, Karl-von-Frisch Strasse 8, Marburg 35043, Germany
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40
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Luo W, Li E, Nie Q, Zhang X. Myomaker, Regulated by MYOD, MYOG and miR-140-3p, Promotes Chicken Myoblast Fusion. Int J Mol Sci 2015; 16:26186-201. [PMID: 26540045 PMCID: PMC4661805 DOI: 10.3390/ijms161125946] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2015] [Revised: 10/16/2015] [Accepted: 10/22/2015] [Indexed: 12/21/2022] Open
Abstract
The fusion of myoblasts is an important step during skeletal muscle differentiation. A recent study in mice found that a transmembrane protein called Myomaker, which is specifically expressed in muscle, is critical for myoblast fusion. However, the cellular mechanism of its roles and the regulatory mechanism of its expression remain unclear. Chicken not only plays an important role in meat production but is also an ideal model organism for muscle development research. Here, we report that Myomaker is also essential for chicken myoblast fusion. Forced expression of Myomaker in chicken primary myoblasts promotes myoblast fusion, whereas knockdown of Myomaker by siRNA inhibits myoblast fusion. MYOD and MYOG, which belong to the family of myogenic regulatory factors, can bind to a conserved E-box located proximal to the Myomaker transcription start site and induce Myomaker transcription. Additionally, miR-140-3p can inhibit Myomaker expression and myoblast fusion, at least in part, by binding to the 3ʹ UTR of Myomaker in vitro. These findings confirm the essential roles of Myomaker in avian myoblast fusion and show that MYOD, MYOG and miR-140-3p can regulate Myomaker expression.
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Affiliation(s)
- Wen Luo
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou 510642, China.
- Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, South China Agricultural University, Guangzhou 510642, China.
- Key Lab of Chicken Genetics, Breeding and Reproduction, Ministry of Agriculture, South China Agricultural University, Guangzhou 510642, China.
| | - Erxin Li
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou 510642, China.
- Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, South China Agricultural University, Guangzhou 510642, China.
- Key Lab of Chicken Genetics, Breeding and Reproduction, Ministry of Agriculture, South China Agricultural University, Guangzhou 510642, China.
| | - Qinghua Nie
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou 510642, China.
- Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, South China Agricultural University, Guangzhou 510642, China.
- Key Lab of Chicken Genetics, Breeding and Reproduction, Ministry of Agriculture, South China Agricultural University, Guangzhou 510642, China.
| | - Xiquan Zhang
- Department of Animal Genetics, Breeding and Reproduction, College of Animal Science, South China Agricultural University, Guangzhou 510642, China.
- Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, South China Agricultural University, Guangzhou 510642, China.
- Key Lab of Chicken Genetics, Breeding and Reproduction, Ministry of Agriculture, South China Agricultural University, Guangzhou 510642, China.
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41
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Deng S, Bothe I, Baylies MK. The Formin Diaphanous Regulates Myoblast Fusion through Actin Polymerization and Arp2/3 Regulation. PLoS Genet 2015; 11:e1005381. [PMID: 26295716 PMCID: PMC4546610 DOI: 10.1371/journal.pgen.1005381] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 06/23/2015] [Indexed: 11/19/2022] Open
Abstract
The formation of multinucleated muscle cells through cell-cell fusion is a conserved process from fruit flies to humans. Numerous studies have shown the importance of Arp2/3, its regulators, and branched actin for the formation of an actin structure, the F-actin focus, at the fusion site. This F-actin focus forms the core of an invasive podosome-like structure that is required for myoblast fusion. In this study, we find that the formin Diaphanous (Dia), which nucleates and facilitates the elongation of actin filaments, is essential for Drosophila myoblast fusion. Following cell recognition and adhesion, Dia is enriched at the myoblast fusion site, concomitant with, and having the same dynamics as, the F-actin focus. Through analysis of Dia loss-of-function conditions using mutant alleles but particularly a dominant negative Dia transgene, we demonstrate that reduction in Dia activity in myoblasts leads to a fusion block. Significantly, no actin focus is detected, and neither branched actin regulators, SCAR or WASp, accumulate at the fusion site when Dia levels are reduced. Expression of constitutively active Dia also causes a fusion block that is associated with an increase in highly dynamic filopodia, altered actin turnover rates and F-actin distribution, and mislocalization of SCAR and WASp at the fusion site. Together our data indicate that Dia plays two roles during invasive podosome formation at the fusion site: it dictates the level of linear F-actin polymerization, and it is required for appropriate branched actin polymerization via localization of SCAR and WASp. These studies provide new insight to the mechanisms of cell-cell fusion, the relationship between different regulators of actin polymerization, and invasive podosome formation that occurs in normal development and in disease.
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Affiliation(s)
- Su Deng
- Graduate Program in Physiology, Biophysics & Systems Biology, Weill Cornell Graduate School of Medical Sciences, Cornell University, New York, New York, United States of America
| | - Ingo Bothe
- Program in Developmental Biology, Sloan Kettering Institute, New York, New York, United States of America
| | - Mary K. Baylies
- Graduate Program in Physiology, Biophysics & Systems Biology, Weill Cornell Graduate School of Medical Sciences, Cornell University, New York, New York, United States of America
- Program in Developmental Biology, Sloan Kettering Institute, New York, New York, United States of America
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42
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Buffolo M, Batista Possidonio AC, Mermelstein C, Araujo H. A conserved role for calpains during myoblast fusion. Genesis 2015; 53:417-30. [DOI: 10.1002/dvg.22870] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Revised: 06/17/2015] [Accepted: 06/25/2015] [Indexed: 11/06/2022]
Affiliation(s)
- Marcio Buffolo
- Laboratório de Diferenciação Muscular e Citoesqueleto, Instituto De Ciências Biomédicas, Universidade Federal Do Rio De Janeiro; Rio De Janeiro Brazil
- Laboratório de Biologia Molecular do Desenvolvimento, Instituto De Ciências Biomédicas, Universidade Federal Do Rio De Janeiro; Rio De Janeiro Brazil
| | - Ana Claudia Batista Possidonio
- Laboratório de Diferenciação Muscular e Citoesqueleto, Instituto De Ciências Biomédicas, Universidade Federal Do Rio De Janeiro; Rio De Janeiro Brazil
| | - Claudia Mermelstein
- Laboratório de Diferenciação Muscular e Citoesqueleto, Instituto De Ciências Biomédicas, Universidade Federal Do Rio De Janeiro; Rio De Janeiro Brazil
| | - Helena Araujo
- Laboratório de Biologia Molecular do Desenvolvimento, Instituto De Ciências Biomédicas, Universidade Federal Do Rio De Janeiro; Rio De Janeiro Brazil
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43
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Kashi VP, Hatley ME, Galindo RL. Probing for a deeper understanding of rhabdomyosarcoma: insights from complementary model systems. Nat Rev Cancer 2015; 15:426-39. [PMID: 26105539 PMCID: PMC4599785 DOI: 10.1038/nrc3961] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Rhabdomyosarcoma (RMS) is a mesenchymal malignancy composed of neoplastic primitive precursor cells that exhibit histological features of myogenic differentiation. Despite intensive conventional multimodal therapy, patients with high-risk RMS typically suffer from aggressive disease. The lack of directed therapies against RMS emphasizes the need to further uncover the molecular underpinnings of the disease. In this Review, we discuss the notable advances in the model systems now available to probe for new RMS-targetable pathogenetic mechanisms, and the possibilities for enhanced RMS therapeutics and improved clinical outcomes.
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Affiliation(s)
- Venkatesh P Kashi
- Department of Pathology, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, Texas 75390-9072, USA
| | - Mark E Hatley
- Department of Oncology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, Tennessee 38105, USA
| | - Rene L Galindo
- 1] Department of Pathology, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, Texas 75390-9072, USA. [2] Department of Molecular Biology, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, Texas 75390-9148, USA. [3] Department of Pediatrics, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, Texas 75390-9063, USA
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44
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Linneweber GA, Winking M, Fischbach KF. The Cell Adhesion Molecules Roughest, Hibris, Kin of Irre and Sticks and Stones Are Required for Long Range Spacing of the Drosophila Wing Disc Sensory Sensilla. PLoS One 2015; 10:e0128490. [PMID: 26053791 PMCID: PMC4459997 DOI: 10.1371/journal.pone.0128490] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 04/27/2015] [Indexed: 12/18/2022] Open
Abstract
Most animal tissues and organ systems are comprised of highly ordered arrays of varying cell types. The development of external sensory organs requires complex cell-cell communication in order to give each cell a specific identity and to ensure a regular distributed pattern of the sensory bristles. This involves both long and short range signaling mediated by either diffusible or cell anchored factors. In a variety of processes the heterophilic Irre Cell Recognition Module, consisting of the Neph-like proteins: Roughest, Kin of irre and of the Nephrin-like proteins: Sticks and Stones, Hibris, plays key roles in the recognition events of different cell types throughout development. In the present study these proteins are apically expressed in the adhesive belt of epithelial cells participating in sense organ development in a partially exclusive and asymmetric manner. Using mutant analysis the GAL4/UAS system, RNAi and gain of function we found an involvement of all four Irre Cell Recognition Module-proteins in the development of a highly structured array of sensory organs in the wing disc. The proteins secure the regular spacing of sensory organs showing partial redundancy and may function in early lateral inhibition events as well as in cell sorting processes. Comparisons with other systems suggest that the Irre Cell Recognition module is a key organizer of highly repetitive structures.
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Affiliation(s)
- Gerit Arne Linneweber
- Department of Neurobiology, Albert-Ludwigs-University Freiburg, Schänzlestr. 1, D-79104, Freiburg, Germany
| | - Mathis Winking
- Department of Neurobiology, Albert-Ludwigs-University Freiburg, Schänzlestr. 1, D-79104, Freiburg, Germany
| | - Karl-Friedrich Fischbach
- Department of Neurobiology, Albert-Ludwigs-University Freiburg, Schänzlestr. 1, D-79104, Freiburg, Germany
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45
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Kim JH, Jin P, Duan R, Chen EH. Mechanisms of myoblast fusion during muscle development. Curr Opin Genet Dev 2015; 32:162-70. [PMID: 25989064 DOI: 10.1016/j.gde.2015.03.006] [Citation(s) in RCA: 158] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Revised: 03/13/2015] [Accepted: 03/17/2015] [Indexed: 01/24/2023]
Abstract
The development and regeneration of skeletal muscle require the fusion of mononucleated muscle cells to form multinucleated, contractile muscle fibers. Studies using a simple genetic model, Drosophila melanogaster, have discovered many evolutionarily conserved fusion-promoting factors in vivo. Recent work in zebrafish and mouse also identified several vertebrate-specific factors required for myoblast fusion. Here, we integrate progress in multiple in vivo systems and highlight conceptual advance in understanding how muscle cell membranes are brought together for fusion. We focus on the molecular machinery at the fusogenic synapse and present a three-step model to describe the molecular and cellular events leading to fusion pore formation.
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Affiliation(s)
- Ji Hoon Kim
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, United States
| | - Peng Jin
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, United States
| | - Rui Duan
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, United States
| | - Elizabeth H Chen
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, United States.
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46
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Brunetti TM, Fremin BJ, Cripps RM. Identification of singles bar as a direct transcriptional target of Drosophila Myocyte enhancer factor-2 and a regulator of adult myoblast fusion. Dev Biol 2015; 401:299-309. [PMID: 25797154 PMCID: PMC4424145 DOI: 10.1016/j.ydbio.2015.02.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Revised: 01/29/2015] [Accepted: 02/14/2015] [Indexed: 11/17/2022]
Abstract
In Drosophila, myoblast fusion is a conserved process in which founder cells (FCs) and fusion competent myoblasts (FCMs) fuse to form a syncytial muscle fiber. Mutants for the myogenic regulator Myocyte enhancer factor-2 (MEF2) show a failure of myoblast fusion, indicating that MEF2 regulates the fusion process. Indeed, chromatin immunoprecipitation studies show that several genes involved in myoblast fusion are bound by MEF2 during embryogenesis. Of these, the MARVEL domain gene singles bar (sing), is down-regulated in MEF2 knockdown pupae, and has five consensus MEF2 binding sites within a 9000-bp region. To determine if MEF2 is an essential and direct regulator of sing during pupal muscle development, we identified a 315-bp myoblast enhancer of sing. This enhancer was active during myoblast fusion, and mutation of two MEF2 sites significantly decreased enhancer activity. We show that lack of sing expression resulted in adult lethality and muscle loss, due to a failure of fusion during the pupal stage. Additionally, we sought to determine if sing was required in either FCs or FCMs to support fusion. Interestingly, knockdown of sing in either population did not significantly affect fusion, however, knockdown in both FCs and FCMs resulted in muscles with significantly reduced nuclei numbers, provisionally indicating that sing function is required in either cell type, but not both. Finally, we found that MEF2 regulated sing expression at the embryonic stage through the same 315-bp enhancer, indicating that sing is a MEF2 target at both critical stages of myoblast fusion. Our studies define for the first time how MEF2 directly controls fusion at multiple stages of the life cycle, and provide further evidence that the mechanisms of fusion characterized in Drosophila embryos is also used in the formation of the more complex adult muscles.
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Affiliation(s)
- Tonya M Brunetti
- Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA
| | - Brayon J Fremin
- Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA
| | - Richard M Cripps
- Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA.
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Haralalka S, Abmayr SM. Tracing myoblast fusion in Drosophila embryos by fluorescent actin probes. Methods Mol Biol 2015; 1313:149-64. [PMID: 25947663 DOI: 10.1007/978-1-4939-2703-6_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
Myoblast fusion in the Drosophila embryo is a highly elaborate process that is initiated by Founder Cells and Fusion-Competent Myoblasts (FCMs). It occurs through an asymmetric event in which actin foci assemble in the FCMs at points of cell-cell contact and direct the formation of membrane protrusions that drive fusion. Herein, we describe the approach that we have used to image in living embryos the highly dynamic actin foci and actin-rich projections that precede myoblast fusion. We discuss resources currently available for imaging actin and myogenesis, and our experience with these resources if available. This technical report is not intended to be comprehensive on providing instruction on standard microscopy practices or software utilization. However, we discuss microscope parameters that we have used in data collection, and our experience with image processing tools in data analysis.
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Affiliation(s)
- Shruti Haralalka
- Stowers Institute for Medical Research, 1000 E. 50th Street, Kansas City, MO, 64110, USA
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48
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Schulman VK, Dobi KC, Baylies MK. Morphogenesis of the somatic musculature in Drosophila melanogaster. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2015; 4:313-34. [PMID: 25758712 DOI: 10.1002/wdev.180] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2014] [Revised: 01/28/2015] [Accepted: 01/30/2015] [Indexed: 12/22/2022]
Abstract
In Drosophila melanogaster, the somatic muscle system is first formed during embryogenesis, giving rise to the larval musculature. Later during metamorphosis, this system is destroyed and replaced by an entirely new set of muscles in the adult fly. Proper formation of the larval and adult muscles is critical for basic survival functions such as hatching and crawling (in the larva), walking and flying (in the adult), and feeding (at both larval and adult stages). Myogenesis, from mononucleated muscle precursor cells to multinucleated functional muscles, is driven by a number of cellular processes that have begun to be mechanistically defined. Once the mesodermal cells destined for the myogenic lineage have been specified, individual myoblasts fuse together iteratively to form syncytial myofibers. Combining cytoplasmic contents demands a level of intracellular reorganization that, most notably, leads to redistribution of the myonuclei to maximize internuclear distance. Signaling from extending myofibers induces terminal tendon cell differentiation in the ectoderm, which results in secure muscle-tendon attachments that are critical for muscle contraction. Simultaneously, muscles become innervated and undergo sarcomerogenesis to establish the contractile apparatus that will facilitate movement. The cellular mechanisms governing these morphogenetic events share numerous parallels to mammalian development, and the basic unit of all muscle, the myofiber, is conserved from flies to mammals. Thus, studies of Drosophila myogenesis and comparisons to muscle development in other systems highlight conserved regulatory programs of biomedical relevance to general muscle biology and studies of muscle disease.
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Affiliation(s)
- Victoria K Schulman
- Cell and Developmental Biology, Weill Cornell Graduate School of Medical Sciences, Cornell University, New York, NY, USA.,Program in Developmental Biology, Sloan Kettering Institute, New York, NY, USA
| | - Krista C Dobi
- Program in Developmental Biology, Sloan Kettering Institute, New York, NY, USA
| | - Mary K Baylies
- Cell and Developmental Biology, Weill Cornell Graduate School of Medical Sciences, Cornell University, New York, NY, USA.,Program in Developmental Biology, Sloan Kettering Institute, New York, NY, USA
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49
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Kim JH, Ren Y, Ng WP, Li S, Son S, Kee YS, Zhang S, Zhang G, Fletcher DA, Robinson DN, Chen EH. Mechanical tension drives cell membrane fusion. Dev Cell 2015; 32:561-73. [PMID: 25684354 DOI: 10.1016/j.devcel.2015.01.005] [Citation(s) in RCA: 100] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 11/14/2014] [Accepted: 01/10/2015] [Indexed: 01/05/2023]
Abstract
Membrane fusion is an energy-consuming process that requires tight juxtaposition of two lipid bilayers. Little is known about how cells overcome energy barriers to bring their membranes together for fusion. Previously, we have shown that cell-cell fusion is an asymmetric process in which an "attacking" cell drills finger-like protrusions into the "receiving" cell to promote cell fusion. Here, we show that the receiving cell mounts a Myosin II (MyoII)-mediated mechanosensory response to its invasive fusion partner. MyoII acts as a mechanosensor, which directs its force-induced recruitment to the fusion site, and the mechanosensory response of MyoII is amplified by chemical signaling initiated by cell adhesion molecules. The accumulated MyoII, in turn, increases cortical tension and promotes fusion pore formation. We propose that the protrusive and resisting forces from fusion partners put the fusogenic synapse under high mechanical tension, which helps to overcome energy barriers for membrane apposition and drives cell membrane fusion.
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Affiliation(s)
- Ji Hoon Kim
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Yixin Ren
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Win Pin Ng
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Shuo Li
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Sungmin Son
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Yee-Seir Kee
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Shiliang Zhang
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Guofeng Zhang
- Laboratory of Bioengineering and Physical Science, National Institute of Biomedical Imaging and Bioengineering, NIH, Bethesda, MD 20892, USA
| | - Daniel A Fletcher
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Douglas N Robinson
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Elizabeth H Chen
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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Applebaum M, Kalcheim C. Mechanisms of myogenic specification and patterning. Results Probl Cell Differ 2015; 56:77-98. [PMID: 25344667 DOI: 10.1007/978-3-662-44608-9_4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Mesodermal somites are initially composed of columnar cells arranged as a pseudostratified epithelium that undergoes sequential and spatially restricted changes to generate the sclerotome and dermomyotome, intermediate structures that develop into vertebrae, striated muscles of the body and limbs, dermis, smooth muscle, and endothelial cells. Regional cues were elucidated that impart differential traits upon the originally multipotent progenitors. How do somite cells and their intermediate progenitors interpret these extrinsic cues and translate them into various levels and/or modalities of intracellular signaling that lead to differential gene expression profiles remains a significant challenge. So is the understanding of how differential fate specification relates to complex cellular migrations prefiguring the formation of body muscles and vertebrae. Research in the past years has largely transited from a descriptive phase in which the lineages of distinct somite-derived progenitors and their cellular movements were traced to a more mechanistic understanding of the local function of genes and regulatory networks underlying lineage segregation and tissue organization. In this chapter, we focus on some major advances addressing the segregation of lineages from the dermomyotome, while discussing both cellular as well as molecular mechanisms, where possible.
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Affiliation(s)
- Mordechai Applebaum
- Department of Medical Neurobiology, IMRIC and ELSC-Hebrew University-Hadassah Medical School, Jerusalem, 9101201, 12272, Israel,
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