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Horo U, Clarke DN, Martin AC. Drosophila Fog/Cta and T48 pathways have overlapping and distinct contributions to mesoderm invagination. Mol Biol Cell 2024; 35:ar69. [PMID: 38536475 PMCID: PMC11151099 DOI: 10.1091/mbc.e24-02-0050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Revised: 03/20/2024] [Accepted: 03/20/2024] [Indexed: 04/13/2024] Open
Abstract
The regulation of the cytoskeleton by multiple signaling pathways, sometimes in parallel, is a common principle of morphogenesis. A classic example of regulation by parallel pathways is Drosophila gastrulation, where the inputs from the Folded gastrulation (Fog)/Concertina (Cta) and the T48 pathways induce apical constriction and mesoderm invagination. Whether there are distinct roles for these separate pathways in regulating the complex spatial and temporal patterns of cytoskeletal activity that accompany early embryo development is still poorly understood. We investigated the roles of the Fog/Cta and T48 pathways and found that, by themselves, the Cta and T48 pathways both promote timely mesoderm invagination and apical myosin II accumulation, with Cta being required for timely cell shape change ahead of mitotic cell division. We also identified distinct functions of T48 and Cta in regulating cellularization and the uniformity of the apical myosin II network, respectively. Our results demonstrate that both redundant and distinct functions for the Fog/Cta and T48 pathways exist.
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Affiliation(s)
- Uzuki Horo
- Biology Department, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139
| | - D. Nathaniel Clarke
- Biology Department, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139
| | - Adam C. Martin
- Biology Department, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139
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2
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Roth S. Neofunctionalization of Toll Signaling in Insects: From Immunity to Dorsoventral Patterning. Annu Rev Cell Dev Biol 2023; 39:1-22. [PMID: 37843930 DOI: 10.1146/annurev-cellbio-120319-120223] [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] [Indexed: 10/18/2023]
Abstract
Toll signaling plays a crucial role in pathogen defense throughout the animal kingdom. It was discovered, however, for its function in dorsoventral (DV) axis formation in Drosophila. In all other insects studied so far, but not outside the insects, Toll is also required for DV patterning. However, in insects more distantly related to Drosophila, Toll's patterning role is frequently reduced and substituted by an expanded influence of BMP signaling, the pathway implicated in DV axis formation in all major metazoan lineages. This suggests that Toll was integrated into an ancestral BMP-based patterning system at the base of the insects or during insect evolution. The observation that Toll signaling has an immune function in the extraembryonic serosa, an early differentiating tissue of most insect embryos, suggests a scenario of how Toll was co-opted from an ancestral immune function for its new role in axis formation.
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Affiliation(s)
- Siegfried Roth
- Institute of Zoology-Developmental Biology, Biocenter, University of Cologne, Cologne, Germany;
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3
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Keyes-Scott NI, Swade KR, Allen LR, Vogel KJ. RNAi-mediated knockdown of two orphan G protein-coupled receptors reduces fecundity in the yellow fever mosquito Aedes aegypti. FRONTIERS IN INSECT SCIENCE 2023; 3:1197945. [PMID: 38469499 PMCID: PMC10926455 DOI: 10.3389/finsc.2023.1197945] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 07/19/2023] [Indexed: 03/13/2024]
Abstract
G protein-coupled receptors (GPCRs) control numerous physiological processes in insects, including reproduction. While many GPCRs have known ligands, orphan GPCRs do not have identified ligands in which they bind. Advances in genomic sequencing and phylogenetics provide the ability to compare orphan receptor protein sequences to sequences of characterized GPCRs, and thus gain a better understanding of the potential functions of orphan GPCRs. Our study sought to investigate the functions of two orphan GPCRs, AAEL003647 and AAEL019988, in the yellow fever mosquito, Aedes aegypti. From our phylogenetic investigation, we found that AAEL003647 is orthologous to the SIFamide-2/SMYamide receptor. We also found that AAEL019988 is orthologous to the Trapped in endoderm (Tre1) receptor of Drosophila melanogaster. Next, we conducted a tissue-specific expression analysis and found that both receptors had highest expression in the ovaries, suggesting they may be important for reproduction. We then used RNA interference (RNAi) to knock down both genes and found a significant reduction in the number of eggs laid per individual female mosquito, suggesting both receptors are important for Ae. aegypti reproduction.
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Affiliation(s)
| | | | | | - Kevin J. Vogel
- Department of Entomology, The University of Georgia, Athens, GA, United States
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4
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McCartney B, Dudin O. Cellularization across eukaryotes: Conserved mechanisms and novel strategies. Curr Opin Cell Biol 2023; 80:102157. [PMID: 36857882 DOI: 10.1016/j.ceb.2023.102157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 01/27/2023] [Accepted: 01/31/2023] [Indexed: 03/02/2023]
Abstract
Many eukaryotes form multinucleated cells during their development. Some cells persist as such during their lifetime, others choose to cleave each nucleus individually using a specialized cytokinetic process known as cellularization. What is cellularization and how is it achieved across the eukaryotic tree of life? Are there common pathways among all species supporting a shared ancestry, or are there key differences, suggesting independent evolutionary paths? In this review, we discuss common strategies and key mechanistic differences in how cellularization is executed across vastly divergent eukaryotic species. We present a number of novel methods and non-model organisms that may provide important insight into the evolutionary origins of cellularization.
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Affiliation(s)
- Brooke McCartney
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
| | - Omaya Dudin
- Swiss Institute for Experimental Cancer Research, School of Life Sciences, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland.
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5
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Sonam S, Balasubramaniam L, Lin SZ, Ivan YMY, Jaumà IP, Jebane C, Karnat M, Toyama Y, Marcq P, Prost J, Mège RM, Rupprecht JF, Ladoux B. Mechanical stress driven by rigidity sensing governs epithelial stability. NATURE PHYSICS 2023; 19:132-141. [PMID: 36686215 PMCID: PMC7614076 DOI: 10.1038/s41567-022-01826-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Epithelia act as a barrier against environmental stress and abrasion and in vivo they are continuously exposed to environments of various mechanical properties. The impact of this environment on epithelial integrity remains elusive. By culturing epithelial cells on 2D hydrogels, we observe a loss of epithelial monolayer integrity through spontaneous hole formation when grown on soft substrates. Substrate stiffness triggers an unanticipated mechanical switch of epithelial monolayers from tensile on soft to compressive on stiff substrates. Through active nematic modelling, we find that spontaneous half-integer defect formation underpinning large isotropic stress fluctuations initiate hole opening events. Our data show that monolayer rupture due to high tensile stress is promoted by the weakening of cell-cell junctions that could be induced by cell division events or local cellular stretching. Our results show that substrate stiffness provides feedback on monolayer mechanical state and that topological defects can trigger stochastic mechanical failure, with potential application towards a mechanistic understanding of compromised epithelial integrity during immune response and morphogenesis.
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Affiliation(s)
- Surabhi Sonam
- Université de Paris, CNRS, Institut Jacques Monod, F-75006 Paris, France
| | | | - Shao-Zhen Lin
- Aix Marseille Univ, Université de Toulon, CNRS, CPT, Turing Center for Living Systems, Marseille, France
| | | | - Irina Pi Jaumà
- Université de Paris, CNRS, Institut Jacques Monod, F-75006 Paris, France
| | - Cecile Jebane
- Université de Paris, CNRS, Institut Jacques Monod, F-75006 Paris, France
| | - Marc Karnat
- Aix Marseille Univ, Université de Toulon, CNRS, CPT, Turing Center for Living Systems, Marseille, France
| | - Yusuke Toyama
- Mechanobiology Institute, National University of Singapore, Singapore
- Department of Biological Sciences, National University of Singapore, Singapore
| | - Philippe Marcq
- Physique et Mécanique des Milieux Hétérogènes, CNRS, ESPCI Paris, PSL University, Sorbonne Université, Université de Paris, 75005, Paris, France
| | - Jacques Prost
- Mechanobiology Institute, National University of Singapore, Singapore
- Physico-Chimie Curie, Institut Curie, CNRS UMR 168, Paris, France
| | - René-Marc Mège
- Université de Paris, CNRS, Institut Jacques Monod, F-75006 Paris, France
| | - Jean-François Rupprecht
- Aix Marseille Univ, Université de Toulon, CNRS, CPT, Turing Center for Living Systems, Marseille, France
- Corresponding authors Dr. Benoit Ladoux, , Dr. Jean-François Rupprecht,
| | - Benoît Ladoux
- Université de Paris, CNRS, Institut Jacques Monod, F-75006 Paris, France
- Corresponding authors Dr. Benoit Ladoux, , Dr. Jean-François Rupprecht,
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6
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Panfilio KA, Chuva de Sousa Lopes SM. The extended analogy of extraembryonic development in insects and amniotes. Philos Trans R Soc Lond B Biol Sci 2022; 377:20210268. [PMID: 36252225 PMCID: PMC9574626 DOI: 10.1098/rstb.2021.0268] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 02/14/2022] [Indexed: 12/22/2022] Open
Abstract
It is fascinating that the amnion and serosa/chorion, two extraembryonic (EE) tissues that are characteristic of the amniote vertebrates (mammals, birds and reptiles), have also independently evolved in insects. In this review, we offer the first detailed, macroevolutionary comparison of EE development and tissue biology across these animal groups. Some commonalities represent independent solutions to shared challenges for protecting the embryo (environmental assaults, risk of pathogens) and supporting its development, including clear links between cellular properties (e.g. polyploidy) and physiological function. Further parallels encompass developmental features such as the early segregation of the serosa/chorion compared to later, progressive differentiation of the amnion and formation of the amniotic cavity from serosal-amniotic folds as a widespread morphogenetic mode across species. We also discuss common developmental roles for orthologous transcription factors and BMP signalling in EE tissues of amniotes and insects, and between EE and cardiac tissues, supported by our exploration of new resources for global and tissue-specific gene expression. This highlights the degree to which general developmental principles and protective tissue features can be deduced from each of these animal groups, emphasizing the value of broad comparative studies to reveal subtle developmental strategies and answer questions that are common across species. This article is part of the theme issue 'Extraembryonic tissues: exploring concepts, definitions and functions across the animal kingdom'.
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Affiliation(s)
| | - Susana M. Chuva de Sousa Lopes
- Department of Anatomy and Embryology, Leiden University Medical Center, 2333 ZC Leiden, The Netherlands
- Department for Reproductive Medicine, Ghent University Hospital, 9000 Ghent, Belgium
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7
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Vishwakarma V, Le TP, Chung S. Multifunctional role of GPCR signaling in epithelial tube formation. Development 2022; 149:276083. [DOI: 10.1242/dev.200519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 07/12/2022] [Indexed: 11/20/2022]
Abstract
ABSTRACT
Epithelial tube formation requires Rho1-dependent actomyosin contractility to generate the cellular forces that drive cell shape changes and rearrangement. Rho1 signaling is activated by G-protein-coupled receptor (GPCR) signaling at the cell surface. During Drosophila embryonic salivary gland (SG) invagination, the GPCR ligand Folded gastrulation (Fog) activates Rho1 signaling to drive apical constriction. The SG receptor that transduces the Fog signal into Rho1-dependent myosin activation has not been identified. Here, we reveal that the Smog GPCR transduces Fog signal to regulate Rho kinase accumulation and myosin activation in the medioapical region of cells to control apical constriction during SG invagination. We also report on unexpected Fog-independent roles for Smog in maintaining epithelial integrity and organizing cortical actin. Our data support a model wherein Smog regulates distinct myosin pools and actin cytoskeleton in a ligand-dependent manner during epithelial tube formation.
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Affiliation(s)
- Vishakha Vishwakarma
- Louisiana State University Department of Biological Sciences , , Baton Rouge, LA 70803 , USA
| | - Thao Phuong Le
- Louisiana State University Department of Biological Sciences , , Baton Rouge, LA 70803 , USA
| | - SeYeon Chung
- Louisiana State University Department of Biological Sciences , , Baton Rouge, LA 70803 , USA
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8
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Nunes-da-Fonseca R. Editorial overview: Development and regulation: Lessons from a multispecies approach. CURRENT OPINION IN INSECT SCIENCE 2022; 51:100917. [PMID: 35358719 DOI: 10.1016/j.cois.2022.100917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Affiliation(s)
- Rodrigo Nunes-da-Fonseca
- Institute of Biodiversity and Sustainability-NUPEM, Universidade Federal do Rio de Janeiro, Av. São José do Barreto 764 Zip Code: 27965-045, Brazil.
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9
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Tidswell ORA, Benton MA, Akam M. The neuroblast timer gene nubbin exhibits functional redundancy with gap genes to regulate segment identity in Tribolium. Development 2021; 148:271199. [PMID: 34351412 PMCID: PMC8406537 DOI: 10.1242/dev.199719] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 07/23/2021] [Indexed: 12/05/2022]
Abstract
The neuroblast timer genes hunchback, Krüppel, nubbin and castor are expressed in temporal sequence in neural stem cells, and in corresponding spatial sequence along the Drosophila blastoderm. As canonical gap genes, hunchback and Krüppel play a crucial role in insect segmentation, but the roles of nubbin and castor in this process remain ambiguous. We have investigated the expression and functions of nubbin and castor during segmentation in the beetle Tribolium. We show that Tc-hunchback, Tc-Krüppel, Tc-nubbin and Tc-castor are expressed sequentially in the segment addition zone, and that Tc-nubbin regulates segment identity redundantly with two previously described gap/gap-like genes, Tc-giant and Tc-knirps. Simultaneous knockdown of Tc-nubbin, Tc-giant and Tc-knirps results in the formation of ectopic legs on abdominal segments. This homeotic transformation is caused by loss of abdominal Hox gene expression, likely due to expanded Tc-Krüppel expression. Our findings support the theory that the neuroblast timer series was co-opted for use in insect segment patterning, and contribute to our growing understanding of the evolution and function of the gap gene network outside of Drosophila. Summary:nubbin and the gap genes knirps and giant redundantly repress Krüppel expression during segmentation. Simultaneous knockdown of all three genes causes ectopic Krüppel expression and loss of abdominal segment identity.
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Affiliation(s)
| | - Matthew A Benton
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | - Michael Akam
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
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10
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Le TP, Chung S. Regulation of apical constriction via microtubule- and Rab11-dependent apical transport during tissue invagination. Mol Biol Cell 2021; 32:1033-1047. [PMID: 33788621 PMCID: PMC8101490 DOI: 10.1091/mbc.e21-01-0021] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The formation of an epithelial tube is a fundamental process for organogenesis. During Drosophila embryonic salivary gland (SG) invagination, Folded gastrulation (Fog)-dependent Rho-associated kinase (Rok) promotes contractile apical myosin formation to drive apical constriction. Microtubules (MTs) are also crucial for this process and are required for forming and maintaining apicomedial myosin. However, the underlying mechanism that coordinates actomyosin and MT networks still remains elusive. Here, we show that MT-dependent intracellular trafficking regulates apical constriction during SG invagination. Key components involved in protein trafficking, such as Rab11 and Nuclear fallout (Nuf), are apically enriched near the SG invagination pit in a MT-dependent manner. Disruption of the MT networks or knockdown of Rab11 impairs apicomedial myosin formation and apical constriction. We show that MTs and Rab11 are required for apical enrichment of the Fog ligand and the continuous distribution of the apical determinant protein Crumbs (Crb) and the key adherens junction protein E-Cadherin (E-Cad) along junctions. Targeted knockdown of crb or E-Cad in the SG disrupts apical myosin networks and results in apical constriction defects. Our data suggest a role of MT- and Rab11-dependent intracellular trafficking in regulating actomyosin networks and cell junctions to coordinate cell behaviors during tubular organ formation.
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Affiliation(s)
- Thao Phuong Le
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803
| | - SeYeon Chung
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803
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11
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Jain A, Ulman V, Mukherjee A, Prakash M, Cuenca MB, Pimpale LG, Münster S, Haase R, Panfilio KA, Jug F, Grill SW, Tomancak P, Pavlopoulos A. Regionalized tissue fluidization is required for epithelial gap closure during insect gastrulation. Nat Commun 2020; 11:5604. [PMID: 33154375 PMCID: PMC7645651 DOI: 10.1038/s41467-020-19356-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Accepted: 10/05/2020] [Indexed: 12/15/2022] Open
Abstract
Many animal embryos pull and close an epithelial sheet around the ellipsoidal egg surface during a gastrulation process known as epiboly. The ovoidal geometry dictates that the epithelial sheet first expands and subsequently compacts. Moreover, the spreading epithelium is mechanically stressed and this stress needs to be released. Here we show that during extraembryonic tissue (serosa) epiboly in the insect Tribolium castaneum, the non-proliferative serosa becomes regionalized into a solid-like dorsal region with larger non-rearranging cells, and a more fluid-like ventral region surrounding the leading edge with smaller cells undergoing intercalations. Our results suggest that a heterogeneous actomyosin cable contributes to the fluidization of the leading edge by driving sequential eviction and intercalation of individual cells away from the serosa margin. Since this developmental solution utilized during epiboly resembles the mechanism of wound healing, we propose actomyosin cable-driven local tissue fluidization as a conserved morphogenetic module for closure of epithelial gaps. The mechanics of embryonic tissue spreading over spherical eggs is not fully understood. Here, the authors show that during gastrulation in the red flour beetle, extraembryonic tissue epiboly is facilitated by local actomyosin-mediated fluidization of the tissue at the leading edge.
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Affiliation(s)
- Akanksha Jain
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Technische Universität Dresden, Dresden, Germany
| | - Vladimir Ulman
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,IT4Innovations, Technical University of Ostrava, Ostrava, Czech Republic
| | | | - Mangal Prakash
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Center for Systems Biology, Dresden, Germany
| | - Marina B Cuenca
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Lokesh G Pimpale
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Biotechnology Center, TU Dresden, Dresden, Germany
| | - Stefan Münster
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Max-Planck-Institute for the Physics of Complex Systems, Dresden, Germany.,Center for Systems Biology, Dresden, Germany.,Biotechnology Center, TU Dresden, Dresden, Germany
| | - Robert Haase
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Center for Systems Biology, Dresden, Germany
| | - Kristen A Panfilio
- Institute for Zoology: Developmental Biology, University of Cologne, Cologne, Germany.,School of Life Sciences, University of Warwick, Coventry, UK
| | - Florian Jug
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Center for Systems Biology, Dresden, Germany
| | - Stephan W Grill
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Center for Systems Biology, Dresden, Germany.,Biotechnology Center, TU Dresden, Dresden, Germany.,Cluster of Excellence Physics of Life, TU Dresden, Dresden, Germany
| | - Pavel Tomancak
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Dresden, Germany. .,IT4Innovations, Technical University of Ostrava, Ostrava, Czech Republic.
| | - Anastasios Pavlopoulos
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA. .,Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece.
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12
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Martin AC. The Physical Mechanisms of Drosophila Gastrulation: Mesoderm and Endoderm Invagination. Genetics 2020; 214:543-560. [PMID: 32132154 PMCID: PMC7054018 DOI: 10.1534/genetics.119.301292] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Accepted: 11/21/2019] [Indexed: 12/14/2022] Open
Abstract
A critical juncture in early development is the partitioning of cells that will adopt different fates into three germ layers: the ectoderm, the mesoderm, and the endoderm. This step is achieved through the internalization of specified cells from the outermost surface layer, through a process called gastrulation. In Drosophila, gastrulation is achieved through cell shape changes (i.e., apical constriction) that change tissue curvature and lead to the folding of a surface epithelium. Folding of embryonic tissue results in mesoderm and endoderm invagination, not as individual cells, but as collective tissue units. The tractability of Drosophila as a model system is best exemplified by how much we know about Drosophila gastrulation, from the signals that pattern the embryo to the molecular components that generate force, and how these components are organized to promote cell and tissue shape changes. For mesoderm invagination, graded signaling by the morphogen, Spätzle, sets up a gradient in transcriptional activity that leads to the expression of a secreted ligand (Folded gastrulation) and a transmembrane protein (T48). Together with the GPCR Mist, which is expressed in the mesoderm, and the GPCR Smog, which is expressed uniformly, these signals activate heterotrimeric G-protein and small Rho-family G-protein signaling to promote apical contractility and changes in cell and tissue shape. A notable feature of this signaling pathway is its intricate organization in both space and time. At the cellular level, signaling components and the cytoskeleton exhibit striking polarity, not only along the apical-basal cell axis, but also within the apical domain. Furthermore, gene expression controls a highly choreographed chain of events, the dynamics of which are critical for primordium invagination; it does not simply throw the cytoskeletal "on" switch. Finally, studies of Drosophila gastrulation have provided insight into how global tissue mechanics and movements are intertwined as multiple tissues simultaneously change shape. Overall, these studies have contributed to the view that cells respond to forces that propagate over great distances, demonstrating that cellular decisions, and, ultimately, tissue shape changes, proceed by integrating cues across an entire embryo.
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Affiliation(s)
- Adam C Martin
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142
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