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Thomas Q, Motta M, Gautier T, Zaki MS, Ciolfi A, Paccaud J, Girodon F, Boespflug-Tanguy O, Besnard T, Kerkhof J, McConkey H, Masson A, Denommé-Pichon AS, Cogné B, Trochu E, Vignard V, El It F, Rodan LH, Alkhateeb MA, Jamra RA, Duplomb L, Tisserant E, Duffourd Y, Bruel AL, Jackson A, Banka S, McEntagart M, Saggar A, Gleeson JG, Sievert D, Bae H, Lee BH, Kwon K, Seo GH, Lee H, Saeed A, Anjum N, Cheema H, Alawbathani S, Khan I, Pinto-Basto J, Teoh J, Wong J, Sahari UBM, Houlden H, Zhelcheska K, Pannetier M, Awad MA, Lesieur-Sebellin M, Barcia G, Amiel J, Delanne J, Philippe C, Faivre L, Odent S, Bertoli-Avella A, Thauvin C, Sadikovic B, Reversade B, Maroofian R, Govin J, Tartaglia M, Vitobello A. Bi-allelic loss-of-function variants in TMEM147 cause moderate to profound intellectual disability with facial dysmorphism and pseudo-Pelger-Huët anomaly. Am J Hum Genet 2022; 109:1909-1922. [PMID: 36044892 PMCID: PMC9606387 DOI: 10.1016/j.ajhg.2022.08.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2022] [Accepted: 08/09/2022] [Indexed: 01/25/2023] Open
Abstract
The transmembrane protein TMEM147 has a dual function: first at the nuclear envelope, where it anchors lamin B receptor (LBR) to the inner membrane, and second at the endoplasmic reticulum (ER), where it facilitates the translation of nascent polypeptides within the ribosome-bound TMCO1 translocon complex. Through international data sharing, we identified 23 individuals from 15 unrelated families with bi-allelic TMEM147 loss-of-function variants, including splice-site, nonsense, frameshift, and missense variants. These affected children displayed congruent clinical features including coarse facies, developmental delay, intellectual disability, and behavioral problems. In silico structural analyses predicted disruptive consequences of the identified amino acid substitutions on translocon complex assembly and/or function, and in vitro analyses documented accelerated protein degradation via the autophagy-lysosomal-mediated pathway. Furthermore, TMEM147-deficient cells showed CKAP4 (CLIMP-63) and RTN4 (NOGO) upregulation with a concomitant reorientation of the ER, which was also witnessed in primary fibroblast cell culture. LBR mislocalization and nuclear segmentation was observed in primary fibroblast cells. Abnormal nuclear segmentation and chromatin compaction were also observed in approximately 20% of neutrophils, indicating the presence of a pseudo-Pelger-Huët anomaly. Finally, co-expression analysis revealed significant correlation with neurodevelopmental genes in the brain, further supporting a role of TMEM147 in neurodevelopment. Our findings provide clinical, genetic, and functional evidence that bi-allelic loss-of-function variants in TMEM147 cause syndromic intellectual disability due to ER-translocon and nuclear organization dysfunction.
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Affiliation(s)
- Quentin Thomas
- UMR1231 GAD, Inserm, Université Bourgogne-Franche Comté, Dijon, France.
| | - Marialetizia Motta
- Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, IRCCS, 00146 Rome, Italy
| | - Thierry Gautier
- University Grenoble Alpes, Inserm, CNRS, Institute for Advanced Biosciences, 38000 Grenoble, France
| | - Maha S Zaki
- Clinical Genetics Department, Human Genetics and Genome Research Institute, National Research Centre, Cairo, Egypt; Armed Forces College of Medicine, Cairo, Egypt
| | - Andrea Ciolfi
- Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, IRCCS, 00146 Rome, Italy
| | - Julien Paccaud
- UMR1231 GAD, Inserm, Université Bourgogne-Franche Comté, Dijon, France
| | - François Girodon
- UMR1231 GAD, Inserm, Université Bourgogne-Franche Comté, Dijon, France; Biology Division, Department of Biological Hematology, Dijon Hospital, 21000 Dijon, France
| | - Odile Boespflug-Tanguy
- Université Paris Cité, UMR 1141 NeuroDiderot, Inserm, 75019 Paris, France; Service de Neuropédiatrie, reference center for leukodystrophies, APHP, Hopital Robert Debré, 75019 Paris, France
| | - Thomas Besnard
- Service de Génétique Médicale, CHU Nantes, Nantes, France; Université de Nantes, CHU Nantes, CNRS, Inserm, l'Institut du Thorax, 44000 Nantes, France
| | - Jennifer Kerkhof
- Verspeeten Clinical Genome Centre, London Health Sciences Centre, London, ON N6A 5W9, Canada
| | - Haley McConkey
- Verspeeten Clinical Genome Centre, London Health Sciences Centre, London, ON N6A 5W9, Canada; Department of Pathology and Laboratory Medicine, Western University, London, ON N6A 3K7, Canada
| | - Aymeric Masson
- UMR1231 GAD, Inserm, Université Bourgogne-Franche Comté, Dijon, France
| | - Anne-Sophie Denommé-Pichon
- UMR1231 GAD, Inserm, Université Bourgogne-Franche Comté, Dijon, France; Unité Fonctionnelle Innovation en Diagnostic Génomique des Maladies Rares, FHU-TRANSLAD, CHU Dijon Bourgogne, Dijon, France
| | - Benjamin Cogné
- Service de Génétique Médicale, CHU Nantes, Nantes, France; Université de Nantes, CHU Nantes, CNRS, Inserm, l'Institut du Thorax, 44000 Nantes, France
| | - Eva Trochu
- Service de Génétique Médicale, CHU Nantes, Nantes, France
| | - Virginie Vignard
- Université de Nantes, CHU Nantes, CNRS, Inserm, l'Institut du Thorax, 44000 Nantes, France
| | - Fatima El It
- UMR1231 GAD, Inserm, Université Bourgogne-Franche Comté, Dijon, France
| | - Lance H Rodan
- Division of Genetics and Genomics, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA; Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | | | - Rami Abou Jamra
- Institute of Human Genetics, University Medical Center, Leipzig, Germany
| | - Laurence Duplomb
- UMR1231 GAD, Inserm, Université Bourgogne-Franche Comté, Dijon, France
| | - Emilie Tisserant
- UMR1231 GAD, Inserm, Université Bourgogne-Franche Comté, Dijon, France
| | - Yannis Duffourd
- UMR1231 GAD, Inserm, Université Bourgogne-Franche Comté, Dijon, France
| | - Ange-Line Bruel
- UMR1231 GAD, Inserm, Université Bourgogne-Franche Comté, Dijon, France; Unité Fonctionnelle Innovation en Diagnostic Génomique des Maladies Rares, FHU-TRANSLAD, CHU Dijon Bourgogne, Dijon, France
| | - Adam Jackson
- Division of Evolution, Infection and Genomics, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK; Manchester Centre for Genomic Medicine, St Mary's Hospital, Manchester University NHS Foundation Trust, Health Innovation Manchester, Manchester, UK
| | - Siddharth Banka
- Division of Evolution, Infection and Genomics, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK; Manchester Centre for Genomic Medicine, St Mary's Hospital, Manchester University NHS Foundation Trust, Health Innovation Manchester, Manchester, UK
| | - Meriel McEntagart
- Medical Genetics, St George's University Hospitals NHS FT, London SW17 0RE, UK
| | - Anand Saggar
- Medical Genetics, St George's University Hospitals NHS FT, London SW17 0RE, UK; The Portland Hospital, 205-209 Great Portland St, London W1W 5AH, UK
| | - Joseph G Gleeson
- Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093, USA; Rady Children's Institute for Genomic Medicine, San Diego, La Jolla, CA 92093, USA
| | - David Sievert
- Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Hyunwoo Bae
- Department of Pediatrics, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Republic of Korea
| | - Beom Hee Lee
- Department of Pediatrics, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Republic of Korea
| | | | | | - Hane Lee
- 3billion, Inc, Seoul, South Korea
| | - Anjum Saeed
- Children's Hospital and University of Child Health Lahore, Lahore, Pakistan
| | - Nadeem Anjum
- Children's Hospital and University of Child Health Lahore, Lahore, Pakistan
| | - Huma Cheema
- Children's Hospital and University of Child Health Lahore, Lahore, Pakistan
| | | | | | | | - Joyce Teoh
- Laboratory of Human Genetics & Therapeutics, Genome Institute of Singapore, A(∗)STAR, Singapore, Singapore
| | - Jasmine Wong
- Laboratory of Human Genetics & Therapeutics, Genome Institute of Singapore, A(∗)STAR, Singapore, Singapore
| | - Umar Bin Mohamad Sahari
- Laboratory of Human Genetics & Therapeutics, Genome Institute of Singapore, A(∗)STAR, Singapore, Singapore
| | - Henry Houlden
- Department of Neuromuscular Disease, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London, UK
| | - Kristina Zhelcheska
- Department of Neuromuscular Disease, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London, UK
| | - Melanie Pannetier
- Service d'Hématologie cellulaire et hémostase bioclinique, CHU Rennes, Rennes, France
| | - Mona A Awad
- Clinical and Chemical Pathology Department, Medical Research and Clinical Studies Institute National Research Centre, Cairo, Egypt
| | - Marion Lesieur-Sebellin
- Service de Médecine Génomique des Maladies Rares, Hôpital Necker-Enfant Malades, AP-HP, Paris, France
| | - Giulia Barcia
- Service de Médecine Génomique des Maladies Rares, Hôpital Necker-Enfant Malades, AP-HP, Paris, France
| | - Jeanne Amiel
- Service de Médecine Génomique des Maladies Rares, Hôpital Necker-Enfant Malades, AP-HP, Paris, France
| | - Julian Delanne
- UMR1231 GAD, Inserm, Université Bourgogne-Franche Comté, Dijon, France; Centre de Référence maladies rares « Anomalies du Développement et syndromes malformatifs », Centre de Génétique, FHU-TRANSLAD, CHU Dijon Bourgogne, Dijon, France
| | - Christophe Philippe
- UMR1231 GAD, Inserm, Université Bourgogne-Franche Comté, Dijon, France; Unité Fonctionnelle Innovation en Diagnostic Génomique des Maladies Rares, FHU-TRANSLAD, CHU Dijon Bourgogne, Dijon, France
| | - Laurence Faivre
- UMR1231 GAD, Inserm, Université Bourgogne-Franche Comté, Dijon, France; Centre de Référence maladies rares « Anomalies du Développement et syndromes malformatifs », Centre de Génétique, FHU-TRANSLAD, CHU Dijon Bourgogne, Dijon, France
| | - Sylvie Odent
- Service de Génétique Clinique, Centre Référence Anomalies du Développement CLAD Ouest, Univ Rennes, Rennes, France; Institut de Génétique et Développement de Rennes, CNRS Inserm UMR 6290, ERL 1305, Univ Rennes, Rennes, France
| | | | - Christel Thauvin
- UMR1231 GAD, Inserm, Université Bourgogne-Franche Comté, Dijon, France; Unité Fonctionnelle Innovation en Diagnostic Génomique des Maladies Rares, FHU-TRANSLAD, CHU Dijon Bourgogne, Dijon, France; Centre de référence maladies rares « déficiences intellectuelles de causes rares », Centre de Génétique, FHU-TRANSLAD, CHU Dijon Bourgogne, Dijon, France
| | - Bekim Sadikovic
- Verspeeten Clinical Genome Centre, London Health Sciences Centre, London, ON N6A 5W9, Canada; Department of Pathology and Laboratory Medicine, Western University, London, ON N6A 3K7, Canada
| | - Bruno Reversade
- Laboratory of Human Genetics & Therapeutics, Genome Institute of Singapore, A(∗)STAR, Singapore, Singapore; Medical Genetics Department, School of Medicine, Koç University, Istanbul, Turkey; Smart-Health Initiative, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
| | - Reza Maroofian
- Department of Neuromuscular Disease, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London, UK
| | - Jérôme Govin
- University Grenoble Alpes, Inserm, CNRS, Institute for Advanced Biosciences, 38000 Grenoble, France
| | - Marco Tartaglia
- Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, IRCCS, 00146 Rome, Italy
| | - Antonio Vitobello
- UMR1231 GAD, Inserm, Université Bourgogne-Franche Comté, Dijon, France; Unité Fonctionnelle Innovation en Diagnostic Génomique des Maladies Rares, FHU-TRANSLAD, CHU Dijon Bourgogne, Dijon, France.
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Kumar V, Park S, Lee U, Kim J. The Organizer and Its Signaling in Embryonic Development. J Dev Biol 2021; 9:jdb9040047. [PMID: 34842722 PMCID: PMC8628936 DOI: 10.3390/jdb9040047] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 10/20/2021] [Accepted: 10/29/2021] [Indexed: 12/25/2022] Open
Abstract
Germ layer specification and axis formation are crucial events in embryonic development. The Spemann organizer regulates the early developmental processes by multiple regulatory mechanisms. This review focuses on the responsive signaling in organizer formation and how the organizer orchestrates the germ layer specification in vertebrates. Accumulated evidence indicates that the organizer influences embryonic development by dual signaling. Two parallel processes, the migration of the organizer’s cells, followed by the transcriptional activation/deactivation of target genes, and the diffusion of secreting molecules, collectively direct the early development. Finally, we take an in-depth look at active signaling that originates from the organizer and involves germ layer specification and patterning.
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Affiliation(s)
- Vijay Kumar
- Department of Biochemistry, Institute of Cell Differentiation and Aging, College of Medicine, Hallym University, Chuncheon 24252, Korea;
| | - Soochul Park
- Department of Biological Sciences, Sookmyung Women’s University, Seoul 04310, Korea;
| | - Unjoo Lee
- Department of Electrical Engineering, Hallym University, Chuncheon 24252, Korea
- Correspondence: (U.L.); (J.K.); Tel.: +82-33-248-2544 (J.K.); Fax: +82-33-244-8425 (J.K.)
| | - Jaebong Kim
- Department of Biochemistry, Institute of Cell Differentiation and Aging, College of Medicine, Hallym University, Chuncheon 24252, Korea;
- Correspondence: (U.L.); (J.K.); Tel.: +82-33-248-2544 (J.K.); Fax: +82-33-244-8425 (J.K.)
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Bethea M, Liu Y, Wade AK, Mullen R, Gupta R, Gelfanov V, DiMarchi R, Bhatnagar S, Behringer R, Habegger KM, Hunter CS. The islet-expressed Lhx1 transcription factor interacts with Islet-1 and contributes to glucose homeostasis. Am J Physiol Endocrinol Metab 2019; 316:E397-E409. [PMID: 30620636 PMCID: PMC6415717 DOI: 10.1152/ajpendo.00235.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The LIM-homeodomain (LIM-HD) transcription factor Islet-1 (Isl1) interacts with the LIM domain-binding protein 1 (Ldb1) coregulator to control expression of key pancreatic β-cell genes. However, Ldb1 also has Isl1-independent effects, supporting that another LIM-HD factor interacts with Ldb1 to impact β-cell development and/or function. LIM homeobox 1 (Lhx1) is an Isl1-related LIM-HD transcription factor that appears to be expressed in the developing mouse pancreas and in adult islets. However, roles for this factor in the pancreas are unknown. This study aimed to determine Lhx1 interactions and elucidate gene regulatory and physiological roles in the pancreas. Co-immunoprecipitation using β-cell extracts demonstrated an interaction between Lhx1 and Isl1, and thus we hypothesized that Lhx1 and Isl1 regulate similar target genes. To test this, we employed siRNA-mediated Lhx1 knockdown in β-cell lines and discovered reduced Glp1R mRNA. Chromatin immunoprecipitation revealed Lhx1 occupancy at a domain also known to be occupied by Isl1 and Ldb1. Through development of a pancreas-wide knockout mouse model ( Lhx1∆Panc), we demonstrate that aged Lhx1∆Panc mice have elevated fasting blood glucose levels, altered intraperitoneal and oral glucose tolerance, and significantly upregulated glucagon, somatostatin, pancreatic polypeptide, MafB, and Arx islet mRNAs. Additionally, Lhx1∆Panc mice exhibit significantly reduced Glp1R, an mRNA encoding the insulinotropic receptor for glucagon-like peptide 1 along with a concomitant dampened Glp1 response and mild glucose intolerance in mice challenged with oral glucose. These data are the first to reveal that the Lhx1 transcription factor contributes to normal glucose homeostasis and Glp1 responses.
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Affiliation(s)
- Maigen Bethea
- Comprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham , Birmingham, Alabama
| | - Yanping Liu
- Comprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham , Birmingham, Alabama
| | - Alexa K Wade
- Comprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham , Birmingham, Alabama
| | - Rachel Mullen
- Department of Genetics, The University of Texas MD Anderson Cancer Center , Houston, Texas
| | - Rajesh Gupta
- Comprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham , Birmingham, Alabama
| | - Vasily Gelfanov
- Department of Chemistry, Indiana University , Bloomington, Indiana
| | - Richard DiMarchi
- Department of Chemistry, Indiana University , Bloomington, Indiana
| | - Sushant Bhatnagar
- Comprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham , Birmingham, Alabama
| | - Richard Behringer
- Department of Genetics, The University of Texas MD Anderson Cancer Center , Houston, Texas
| | - Kirk M Habegger
- Comprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham , Birmingham, Alabama
| | - Chad S Hunter
- Comprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham , Birmingham, Alabama
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Carron C, Shi DL. Specification of anteroposterior axis by combinatorial signaling during Xenopus development. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2015; 5:150-68. [PMID: 26544673 DOI: 10.1002/wdev.217] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2015] [Revised: 09/01/2015] [Accepted: 09/12/2015] [Indexed: 01/08/2023]
Abstract
The specification of anteroposterior (AP) axis is a fundamental and complex patterning process that sets up the embryonic polarity and shapes a multicellular organism. This process involves the integration of distinct signaling pathways to coordinate temporal-spatial gene expression and morphogenetic movements. In the frog Xenopus, extensive embryological and molecular studies have provided major advance in understanding the mechanism implicated in AP patterning. Following fertilization, cortical rotation leads to the transport of maternal determinants to the dorsal region and creates the primary dorsoventral (DV) asymmetry. The activation of maternal Wnt/ß-catenin signaling and a high Nodal signal induces the formation of the Nieuwkoop center in the dorsal-vegetal cells, which then triggers the formation of the Spemann organizer in the overlying dorsal marginal zone. It is now well established that the Spemann organizer plays a central role in building the vertebrate body axes because it provides patterning information for both DV and AP polarities. The antagonistic interactions between signals secreted in the Spemann organizer and the opposite ventral region pattern the mesoderm along the DV axis, and this DV information is translated into AP positional values during gastrulation. The formation of anterior neural tissue requires simultaneous inhibition of zygotic Wnt and bone morphogenetic protein (BMP) signals, while an endogenous gradient of Wnt, fibroblast growth factors (FGFs), retinoic acid (RA) signaling, and collinearly expressed Hox genes patterns the trunk and posterior regions. Collectively, DV asymmetry is mostly coupled to AP polarity, and cell-cell interactions mediated essentially by the same regulatory networks operate in DV and AP patterning. For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Clémence Carron
- Laboratory of Developmental Biology, Sorbonne Universités, Institut de Biologie Paris-Seine (IBPS), Paris, France
| | - De-Li Shi
- Laboratory of Developmental Biology, Sorbonne Universités, Institut de Biologie Paris-Seine (IBPS), Paris, France.,School of Life Sciences, Shandong University, Jinan, China
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Kaneda T, Motoki JYD. Gastrulation and pre-gastrulation morphogenesis, inductions, and gene expression: Similarities and dissimilarities between urodelean and anuran embryos. Dev Biol 2012; 369:1-18. [DOI: 10.1016/j.ydbio.2012.05.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2011] [Revised: 05/14/2012] [Accepted: 05/18/2012] [Indexed: 10/28/2022]
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Elinson RP, del Pino EM. Developmental diversity of amphibians. WILEY INTERDISCIPLINARY REVIEWS. DEVELOPMENTAL BIOLOGY 2012; 1:345-69. [PMID: 22662314 PMCID: PMC3364608 DOI: 10.1002/wdev.23] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The current model amphibian, Xenopus laevis, develops rapidly in water to a tadpole which metamorphoses into a frog. Many amphibians deviate from the X. laevis developmental pattern. Among other adaptations, their embryos develop in foam nests on land or in pouches on their mother's back or on a leaf guarded by a parent. The diversity of developmental patterns includes multinucleated oogenesis, lack of RNA localization, huge non-pigmented eggs, and asynchronous, irregular early cleavages. Variations in patterns of gastrulation highlight the modularity of this critical developmental period. Many species have eliminated the larva or tadpole and directly develop to the adult. The wealth of developmental diversity among amphibians coupled with the wealth of mechanistic information from X. laevis permit comparisons that provide deeper insights into developmental processes.
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Affiliation(s)
- Richard P Elinson
- Department of Biological Sciences, Duquesne University, Pittsburgh, PA, USA.
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Sharon N, Mor I, Golan-lev T, Fainsod A, Benvenisty N. Molecular and Functional Characterizations of Gastrula Organizer Cells Derived from Human Embryonic Stem Cells. Stem Cells 2011; 29:600-8. [DOI: 10.1002/stem.621] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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FOLEY ANNC, STERN CLAUDIOD. Evolution of vertebrate forebrain development: how many different mechanisms? J Anat 2009. [DOI: 10.1046/j.1469-7580.199.parts1-2.5.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
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Molecular characterization of the gastrula in the turtle Emys orbicularis: an evolutionary perspective on gastrulation. PLoS One 2008; 3:e2676. [PMID: 18628985 PMCID: PMC2442194 DOI: 10.1371/journal.pone.0002676] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2008] [Accepted: 05/23/2008] [Indexed: 11/19/2022] Open
Abstract
Due to the presence of a blastopore as in amphibians, the turtle has been suggested to exemplify a transition form from an amphibian- to an avian-type gastrulation pattern. In order to test this hypothesis and gain insight into the emergence of the unique characteristics of amniotes during gastrulation, we have performed the first molecular characterization of the gastrula in a reptile, the turtle Emys orbicularis. The study of Brachyury, Lim1, Otx2 and Otx5 expression patterns points to a highly conserved dynamic of expression with amniote model organisms and makes it possible to identify the site of mesoderm internalization, which is a long-standing issue in reptiles. Analysis of Brachyury expression also highlights the presence of two distinct phases, less easily recognizable in model organisms and respectively characterized by an early ring-shaped and a later bilateral symmetrical territory. Systematic comparisons with tetrapod model organisms lead to new insights into the relationships of the blastopore/blastoporal plate system shared by all reptiles, with the blastopore of amphibians and the primitive streak of birds and mammals. The biphasic Brachyury expression pattern is also consistent with recent models of emergence of bilateral symmetry, which raises the question of its evolutionary significance.
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Fujii H, Sakai M, Nishimatsu SI, Nohno T, Mochii M, Orii H, Watanabe K. VegT, eFGF and Xbra cause overall posteriorization while Xwnt8 causes eye-level restricted posteriorization in synergy with chordin in early Xenopus development. Dev Growth Differ 2008; 50:169-80. [PMID: 18318733 DOI: 10.1111/j.1440-169x.2008.01014.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We examined several candidate posterior/mesodermal inducing molecules using permanent blastula-type embryos (PBEs) as an assay system. Candidate molecules were injected individually or in combination with the organizer factor chordin mRNA. Injection of chordin alone resulted in a white hemispherical neural tissue surrounded by a large circular cement gland, together with anterior neural gene expression and thus the development of the anterior-most parts of the embryo, without mesodermal tissues. When VegT, eFGF or Xbra mRNAs were injected into a different blastomere of the chordin-injected PBEs, the embryos elongated and formed eye, muscle and pigment cells, and expressed mesodermal and posterior neural genes. These embryos formed the full spectrum of the anteroposterior embryonic axis. In contrast, injection of CSKA-Xwnt8 DNA into PBEs injected with chordin resulted in eye formation and expression of En2, a midbrain/hindbrain marker, and Xnot, a notochord marker, but neither elongation, muscle formation nor more posterior gene expression. Injection of chordin and posteriorizing molecules into the same cell did not result in elongation of the embryo. Thus, by using PBEs as the host test system we show that (i) overall anteroposterior neural development, mesoderm (muscle) formation, together with embryo elongation can occur through the synergistic effect(s) of the organizer molecule chordin, and each of the 'verall posteriorizing molecules'eFGF, VegT and Xbra; (ii) Xwnt8-mediated posteriorization is restricted to the eye level and is independent of mesoderm formation; and (iii) proper anteroposterior patterning requires a separation of the dorsalizing and posteriorizing gene expression domains.
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Affiliation(s)
- Hidefumi Fujii
- Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori Akou, Hyogo 678-1297, Japan.
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del Pino EM, Venegas-Ferrín M, Romero-Carvajal A, Montenegro-Larrea P, Sáenz-Ponce N, Moya IM, Alarcón I, Sudou N, Yamamoto S, Taira M. A comparative analysis of frog early development. Proc Natl Acad Sci U S A 2007; 104:11882-8. [PMID: 17606898 PMCID: PMC1924569 DOI: 10.1073/pnas.0705092104] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2007] [Indexed: 11/18/2022] Open
Abstract
The current understanding of Xenopus laevis development provides a comparative background for the analysis of frog developmental modes. Our analysis of development in various frogs reveals that the mode of gastrulation is associated with developmental rate and is unrelated to egg size. In the gastrula of the rapidly developing embryos of the foam-nesting frogs Engystomops coloradorum and Engystomops randi, archenteron and notochord elongation overlapped with involution at the blastopore lip, as in X. laevis embryos. In embryos of dendrobatid frogs and in the frog without tadpoles Eleutherodactylus coqui, which develop somewhat more slowly than X. laevis, involution and archenteron elongation concomitantly occurred during gastrulation; whereas elongation of the notochord and, therefore, dorsal convergence and extension, occurred in the postgastrula. In contrast, in the slow developing embryos of the marsupial frog Gastrotheca riobambae, only involution occurred during gastrulation. The processes of archenteron and notochord elongation and convergence and extension were postgastrulation events. We produced an Ab against the homeodomain protein Lim1 from X. laevis as a tool for the comparative analysis of development. By the expression of Lim1, we were able to identify the dorsal side of the G. riobambae early gastrula, which otherwise was difficult to detect. Moreover, the Lim1 expression in the dorsal lip of the blastopore and notochord differed among the studied frogs, indicating variation in the timing of developmental events. The variation encountered gives evidence of the modular character of frog gastrulation.
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Affiliation(s)
- Eugenia M del Pino
- Escuela de Ciencias Biológicas, Pontificia Universidad Católica del Ecuador, Avenida 12 de Octubre 1076 y Roca, Quito, Ecuador.
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12
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Schambony A, Wedlich D. Wnt-5A/Ror2 regulate expression of XPAPC through an alternative noncanonical signaling pathway. Dev Cell 2007; 12:779-92. [PMID: 17488628 DOI: 10.1016/j.devcel.2007.02.016] [Citation(s) in RCA: 228] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Revised: 01/18/2007] [Accepted: 02/20/2007] [Indexed: 02/06/2023]
Abstract
XWnt-5A, a member of the nontransforming Wnt-5A class of Wnt ligands, is required for convergent extension movements in Xenopus embryos. XWnt-5A knockdown phenocopies paraxial protocadherin (XPAPC) loss of function: involuted mesodermal cells fail to align mediolaterally, which results in aberrant movements and a selective inhibition of constriction. XWnt-5A depletion was rescued by coinjection of XPAPC RNA, indicating that XWnt-5A acts upstream of XPAPC. XWnt-5A, but not XWnt-11, stimulates XPAPC expression independent of the canonical Wnt/beta-catenin pathway. We show that transcriptional regulation of XPAPC by XWnt-5A requires the receptor tyrosine kinase Ror2. XWnt-5A/Xror2 signal through PI3 kinase and cdc42 to activate the JNK signaling cascade with the transcription factors ATF2 and c-jun. The Wnt-5A/Ror2 pathway represents an alternative, distinct branch of noncanonical Wnt signaling that controls gene expression and is required in the regulation of convergent extension movements in Xenopus gastrulation.
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Affiliation(s)
- Alexandra Schambony
- Universitaet Karlsruhe (TH), Zoologisches Institut II, Kaiserstrasse 12, D-76128 Karlsruhe, Germany.
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13
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Patil SS, Alexander TB, Uzman JA, Lou CH, Gohil H, Sater AK. Novel gene ashwin functions in Xenopus cell survival and anteroposterior patterning. Dev Dyn 2006; 235:1895-907. [PMID: 16680723 DOI: 10.1002/dvdy.20834] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The novel gene ashwin was isolated in a differential display screen for genes activated or up-regulated early in neural specification. ashwin is expressed maternally and zygotically, and it is up-regulated in the neural ectoderm after the midgastrula stage. It is expressed in the neural plate and later in the embryonic brain, eyes, and spinal cord. Overexpression of ashwin in whole embryos leads to anterior truncations and other defects. However, a second Organizer does not form, and the secondary axial structures may result from splitting of the Organizer, rather than axis duplication. Morpholino oligonucleotide-mediated reduction in ashwin expression leads to lethality or abnormalities in gastrulation, as well as significant apoptosis in midgastrula embryos. Apoptosis is also observed in midgastrula embryos overexpressing ashwin. Coexpression of ashwin with the bone morphogenetic protein-4 antagonist noggin has a synergistic effect on neural-specific gene expression in isolated animal cap ectoderm. Ashwin has no previously characterized domains, although two nuclear localization signals can be identified. Orthologues have been identified in the human, mouse, chicken, and pufferfish genomes. Our results suggest that ashwin regulates cell survival and anteroposterior patterning.
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Affiliation(s)
- Sonali S Patil
- Department of Biology and Biochemistry, University of Houston, Houston, Texas 77204-5001, USA
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14
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Suga A, Hikasa H, Taira M. Xenopus ADAMTS1 negatively modulates FGF signaling independent of its metalloprotease activity. Dev Biol 2006; 295:26-39. [PMID: 16690049 DOI: 10.1016/j.ydbio.2006.02.041] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2005] [Revised: 02/17/2006] [Accepted: 02/23/2006] [Indexed: 10/24/2022]
Abstract
We have isolated the Xenopus ortholog of ADAMTS1 (a disintegrin and metalloprotease with thrombospondin motifs), XADAMTS1, which is expressed in the presumptive ectoderm, then the Spemann organizer, and later in the trunk organizer region and posterior ectoderm in the Xenopus embryo. We show that, when overexpressed in the dorsal marginal zone or in the anterior ectoderm by mRNA injection, XADAMTS1 inhibits gastrulation or generates embryos with an enlarged cement gland, respectively. XADAMTS1 also reduces the expression of Xbra in both whole embryos and FGF-treated animal caps. These effects of XADAMTS1 are likely to be due to its inhibition of the Ras-MAPK cascade because XADAMTS1 inhibits the phosphorylation of ERK by FGF4 in animal caps. Deletion analysis of XADAMTS1 revealed that a combination of the signal peptide and the C-terminal region containing the thrombospondin type 1 repeats is necessary and sufficient for this function, whereas the metalloprotease domain is dispensable. In addition, loss-of-function analysis with antisense morpholino oligos showed that knockdown of XADAMTS1 sensitizes animal caps to Xbra induction by FGF2. These data suggest that secreted XADAMTS1 negatively modulates FGF signaling in the Xenopus embryo.
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Affiliation(s)
- Akiko Suga
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Japan
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15
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Anteroposterior and Dorsoventral Patterning. Dev Neurobiol 2006. [DOI: 10.1007/0-387-28117-7_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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16
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Hayashi S, Itoh M, Taira S, Agata K, Taira M. Expression patterns of Xenopus FGF receptor-like 1/nou-darake in early Xenopus development resemble those of planarian nou-darake and Xenopus FGF8. Dev Dyn 2005; 230:700-7. [PMID: 15254904 DOI: 10.1002/dvdy.20040] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Fibroblast growth factors (FGFs) mediate many cell-to-cell signaling events during early development. Nou-darake (ndk), a gene encoding an FGF receptor (FGFR)-like molecule, was found to be highly and specifically expressed in the head region of the planarian Dugesia japonica, and its functional analyses provided strong molecular evidence for the existence of a brain-inducing circuit based on the FGF signaling pathway. To analyze the role of ndk during vertebrate development, we isolated the Xenopus ortholog of ndk, the vertebrate FGFR-like 1 gene (XFGFRL1). Expression of XFGFRL1/Xndk was first detected in the anterior region at the late gastrula stage and dramatically increased at the early neurula stage in an overall anterior mesendodermal region, including the prechordal plate, paraxial mesoderm, anterior endoderm, and archenteron roof. This anterior expression pattern resembles that of ndk in planarians, suggesting that the expression of FGFRL1/ndk is conserved in evolution between these two distantly diverged organisms. During the tail bud stages, XFGFRL1/Xndk expression was detected in multiple regions, including the forebrain, eyes, midbrain-hindbrain boundary, otic vesicles, visceral arches, and somites. In many of these regions, XFGFRL1/Xndk was coexpressed with XFGF8, indicating that XFGFRL1/Xndk is a member of the XFGF8 synexpression group, which includes sprouty, sef, and isthmin.
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Affiliation(s)
- Shuichi Hayashi
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Japan
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17
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Hiratani I, Yamamoto N, Mochizuki T, Ohmori SY, Taira M. Selective degradation of excess Ldb1 by Rnf12/RLIM confers proper Ldb1 expression levels and Xlim-1/Ldb1 stoichiometry in Xenopus organizer functions. Development 2003; 130:4161-75. [PMID: 12874135 DOI: 10.1242/dev.00621] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Xenopus LIM homeodomain (LIM-HD) protein, Xlim-1, is expressed in the Spemann organizer and cooperates with its positive regulator, Ldb1, to activate organizer gene expression. While this activation is presumably mediated through Xlim-1/Ldb1 tetramer formation, the mechanisms regulating proper Xlim-1/Ldb1 stoichiometry remains largely unknown. We isolated the Xenopus ortholog (XRnf12) of the RING finger protein Rnf12/RLIM and explored its functional interactions with Xlim-1 and Ldb1. Although XRnf12 functions as a E3 ubiquitin ligase for Ldb1 and causes proteasome-dependent degradation of Ldb1, we found that co-expression of a high level of Xlim-1 suppresses Ldb1 degradation by XRnf12. This suppression requires both the LIM domains of Xlim-1 and the LIM interaction domain of Ldb1, suggesting that Ldb1, when bound to Xlim-1, escapes degradation by XRnf12. We further show that a high level of Ldb1 suppresses the organizer activity of Xlim-1/Ldb1, suggesting that excess Ldb1 molecules disturb Xlim-1/Ldb1 stoichiometry. Consistent with this, Ldb1 overexpression in the dorsal marginal zone suppresses expression of several organizer genes including postulated Xlim-1 targets, and importantly, this suppression is rescued by co-expression of XRnf12. These data suggest that XRnf12 confers proper Ldb1 protein levels and Xlim-1/Ldb1 stoichiometry for their functions in the organizer. Together with the similarity in the expression pattern of Ldb1 and XRnf12 throughout early embryogenesis, we propose Rnf12/RLIM as a specific regulator of Ldb1 to ensure its proper interactions with LIM-HD proteins and possibly other Ldb1-interacting proteins in the organizer as well as in other tissues.
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Affiliation(s)
- Ichiro Hiratani
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan
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18
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López SL, Paganelli AR, Siri MVR, Ocaña OH, Franco PG, Carrasco AE. Notch activates sonic hedgehog and both are involved in the specification of dorsal midline cell-fates in Xenopus. Development 2003; 130:2225-38. [PMID: 12668635 DOI: 10.1242/dev.00443] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
We analysed the role of Notch signalling during the specification of the dorsal midline in Xenopus embryos. By activating or blocking the pathway we found that Notch expands the floor plate domain of sonic hedgehog and pintallavis and represses the notochordal markers chordin and brachyury, with a concomitant reduction of the notochord size. We propose that within a population of the early organiser with equivalent potential to develop either as notochord or floor plate, Notch activation favours floor plate development at the expense of the notochord, preferentially before mid gastrula. We present evidence that sonic hedgehog down-regulates chordin, suggesting that secreted Sonic hedgehog may be involved or reinforcing the cell-fate switch executed by Notch. We also show that Notch signalling requires Presenilin to modulate this switch.
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Affiliation(s)
- Silvia L López
- Laboratorio de Embriología Molecular, Instituto de Biología Celular y Neurociencias, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155, 3 degrees piso (1121), Buenos Aires, Argentina
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19
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Yamamoto S, Hikasa H, Ono H, Taira M. Molecular link in the sequential induction of the Spemann organizer: direct activation of the cerberus gene by Xlim-1, Xotx2, Mix.1, and Siamois, immediately downstream from Nodal and Wnt signaling. Dev Biol 2003; 257:190-204. [PMID: 12710967 DOI: 10.1016/s0012-1606(03)00034-4] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
To elucidate the molecular basis of organizer functions in Xenopus, we sought the target genes of the LIM homeodomain protein Xlim-1, which is one of the organizer-specific transcriptional activators. We found that an activated form of Xlim-1, Xlim-1/3m, initiates ectopic expression of the head-inducing organizer factor gene cerberus in animal caps. Thus, we analyzed the cerberus promoter using reporter assays. We show that three consecutive TAAT motifs of the homeodomain-binding sites between positions -141 and -118, collectively designated the "3xTAAT element," are crucial for the response of the cerberus promoter to Xlim-1/3m, and for its activation in the dorsal region of the embryo. Because cooperative activation of the cerberus promoter by Xnr1 and Xwnt8 also requires the 3xTAAT element, we focused on homeodomain transcriptional activators downstream from either Nodal or Wnt signaling. We found that wild-type Xlim-1 synergistically activates the cerberus promoter with Mix.1 and Siamois through the 3xTAAT element, and this synergy requires the LIM domains of Xlim-1. In contrast, Xotx2 acts synergistically with Mix.1 and Siamois through the TAATCT sequence at -95. Electrophoretic mobility shift assays revealed that Xlim-1, Siamois, and Mix.1 are likely to bind as a complex, in a LIM domain-dependent manner, to the region containing the 3xTAAT element. These data suggest that cerberus is a direct target for Xlim-1, Mix.1, Siamois, and Xotx2. Therefore, we propose a model for the molecular link in the inductive sequence from the formation of the organizer to anterior neural induction.
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Affiliation(s)
- Shinji Yamamoto
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo 7-3-1, 113-0033, Bunkyo-ku, Tokyo, Japan
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20
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Hukriede NA, Tsang TE, Habas R, Khoo PL, Steiner K, Weeks DL, Tam PPL, Dawid IB. Conserved requirement of Lim1 function for cell movements during gastrulation. Dev Cell 2003; 4:83-94. [PMID: 12530965 DOI: 10.1016/s1534-5807(02)00398-2] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
To investigate Lim1 function during gastrulation, we used transcript depletion through DEED antisense oligonucleotides in Xenopus and cell transplantation in mice. Xenopus embryos depleted of Lim1 lack anterior head structures and fail to form a proper axis as a result of a failure of gastrulation movements, even though mesodermal cell identities are specified. Similar disruption of cell movements in the mesoderm is also observed in Lim1(-/-) mice. Paraxial protocadherin (PAPC) expression is lost in the nascent mesoderm of Lim1(-/-) mouse embryos and in the organizer of Lim1-depleted Xenopus embryos; the latter can be rescued to a considerable extent by supplying PAPC exogenously. We conclude that a primary function of Lim1 in the early embryo is to enable proper cell movements during gastrulation.
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Affiliation(s)
- Neil A Hukriede
- Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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21
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Hikasa H, Shibata M, Hiratani I, Taira M. TheXenopusreceptor tyrosine kinase Xror2 modulates morphogenetic movements of the axial mesoderm and neuroectoderm via Wnt signaling. Development 2002; 129:5227-39. [PMID: 12399314 DOI: 10.1242/dev.129.22.5227] [Citation(s) in RCA: 128] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Spemann organizer plays a central role in neural induction, patterning of the neuroectoderm and mesoderm, and morphogenetic movements during early embryogenesis. By seeking genes whose expression is activated by the organizer-specific LIM homeobox gene Xlim-1 in Xenopusanimal caps, we isolated the receptor tyrosine kinase Xror2. Xror2 is expressed initially in the dorsal marginal zone, then in the notochord and the neuroectoderm posterior to the midbrain-hindbrain boundary. mRNA injection experiments revealed that overexpression of Xror2 inhibits convergent extension of the dorsal mesoderm and neuroectoderm in whole embryos, as well as the elongation of animal caps treated with activin, whereas it does not appear to affect cell differentiation of neural tissue and notochord. Interestingly, mutant constructs in which the kinase domain was point-mutated or deleted (named Xror2-TM) also inhibited convergent extension, and did not counteract the wild-type, suggesting that the ectodomain of Xror2 per se has activities that may be modulated by the intracellular domain. In relation to Wnt signaling for planar cell polarity, we observed: (1) the Frizzled-like domain in the ectodomain is required for the activity of wild-type Xror2 and Xror2-TM; (2) co-expression of Xror2 with Xwnt11, Xfz7, or both,synergistically inhibits convergent extension in embryos; (3) inhibition of elongation by Xror2 in activin-treated animal caps is reversed by co-expression of a dominant negative form of Cdc42 that has been suggested to mediate the planar cell polarity pathway of Wnt; and (4) the ectodomain of Xror2 interacts with Xwnts in co-immunoprecipitation experiments. These results suggest that Xror2 cooperates with Wnts to regulate convergent extension of the axial mesoderm and neuroectoderm by modulating the planar cell polarity pathway of Wnt.
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Affiliation(s)
- Hiroki Hikasa
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, and Core Research for Evolutional Science and Technology, Japan Science and Technology Corporation, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan
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22
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Affiliation(s)
- Malcolm Maden
- MRC Centre for Developmental Neurobiology, 4th Floor New Hunt's House, King's College London, Guy's Campus, London Bridge, London SE1 1UL, UK.
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23
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Shinga J, Itoh M, Shiokawa K, Taira S, Taira M. Early patterning of the prospective midbrain-hindbrain boundary by the HES-related gene XHR1 in Xenopus embryos. Mech Dev 2001; 109:225-39. [PMID: 11731236 DOI: 10.1016/s0925-4773(01)00528-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The molecular mechanisms that govern early patterning of anterior neuroectoderm (ANE) for the prospective brain region in vertebrates are largely unknown. Screening a cDNA library of Xenopus ANE led to the isolation of a Hairy and Enhancer of split- (HES)-related transcriptional repressor gene, Xenopus HES-related 1 (XHR1). XHR1 is specifically expressed in the midbrain-hindbrain boundary (MHB) region at the tailbud stage. The localized expression of XHR1 was detected as early as the early gastrula stage in the presumptive MHB region, an area just anterior to the involuting dorsal mesoderm that is demarcated by the expression of the gene Xbra. Expression of XHR1 was detected much earlier than that of other known MHB genes, XPax-2 and En-2, and also before the formation of the expression boundary between Xotx2 and Xgbx-2, suggesting that the early patterning of the presumptive MHB is independent of Xotx2 and Xgbx-2. Instead, the location of XHR1 expression appears to be determined in relation to the Xbra expression domain, since reduced or ectopic expression of Xbra altered the XHR1 expression domain according to the location of Xbra expression. In functional assays using mRNA injection, overexpression of dominant-negative forms of XHR1 in the MHB region led to marked reduction of XPax-2 and En-2 expression, and this phenotype was rescued by coexpression of wild-type XHR1. Furthermore, ectopically expressed wild-type XHR1 near the MHB region enhanced En-2 expression only in the MHB region but not in the region outside the MHB. These data suggest that XHR1 is required, but not sufficient by itself, to initiate MHB marker gene expression. Based on these data, we propose that XHR1 demarcates the prospective MHB region in the neuroectoderm in Xenopus early gastrulae.
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Affiliation(s)
- J Shinga
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, 113-0033, Tokyo, Japan
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Shibata M, Itoh M, Ohmori SY, Shinga J, Taira M. Systematic screening and expression analysis of the head organizer genes in Xenopus embryos. Dev Biol 2001; 239:241-56. [PMID: 11784032 DOI: 10.1006/dbio.2001.0428] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We describe here a systematic screen of an anterior endomesoderm (AEM) cDNA library to isolate novel genes which are expressed in the head organizer region. After removing clones which hybridized to labeled cDNA probes synthesized with total RNA from a trunk region of tailbud embryos, the 5' ends of 1039 randomly picked cDNA clones were sequenced to make expressed sequence tags (ESTs), which formed 754 tentative unique clusters. Those clusters were compared against public databases and classified according to similarities found to other genes and gene products. Of them, 151 clusters were identified as known Xenopus genes, including eight organizer-specific ones (5.3%). Gene expression pattern screening was performed for 198 unique clones, which were selected because they either have no known function or are predicted to be developmental regulators in other species. The screen revealed nine possible organizer-specific clones (4.5%), four of which appeared to be expressed in the head organizer region. Detailed expression analysis from gastrula to neurula stages showed that these four genes named crescent, P7E4 (homologous to human hypothetical genes), P8F7 (an unclassified gene), and P17F11 (homologous to human and Arabidopsis hypothetical genes) demarcate spatiotemporally distinct subregions of the AEM corresponding to the head organizer region. These results indicate that our screening strategy is effective in isolating novel region-specific genes.
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Affiliation(s)
- M Shibata
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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25
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Tabata T, Sakaguchi K, Tajima T, Suzuki AS. Comparative study of sequential expression of the organizer-related genes in normal Cynops pyrrhogaster embryos and mesodermalized ectoderm. Dev Growth Differ 2001; 43:351-9. [PMID: 11473542 DOI: 10.1046/j.1440-169x.2001.00581.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
An artificially mesodermalized ectoderm (mE) of early Cynops pyrrhogaster gastrula acquires the organizer property; the mE is able to induce the secondary axis. The expression of organizer-related genes was investigated during the mesodermalizing process of the mE. The expression of C. pyrrhogaster organizer-related genes, such as bra, gsc, lim-1, chd and noggin, were analyzed. Cynops pyrrhogaster shh expression was also investigated. The organizer-related genes were activated by 12 h after the mesoderm-inducing stimulus. It was noted that there was a temporal gap in the expression of each gene. The expression of bra and gsc seemed to be more quickly activated during the mesodermalizing process. While expression of lim-1 and noggin was activated later than that of bra and gsc, lim-1 expression was earlier than chd and noggin expression. Shh expression was activated later than lim-1/noggin. The present study suggests the possibility that the bra/gsc, lim-1, chd, noggin and shh genes are expressed one by one in that order during the mesodermalizing of the presumptive ectoderm. It also indicates that the sequence is not always consistent with that of the whole embryo during normal embryogenesis. The meaning of the discrepancy will be discussed in connection with the cascade of certain genes expressed during the mesodermalizing process.
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Affiliation(s)
- T Tabata
- Natural Enviromental Science, Department of Enviromental Science, Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan
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Abstract
Over the past 50 years and more, many models have been proposed to explain how the nervous system is initially induced and how it becomes subdivided into gross regions such as forebrain, midbrain, hindbrain and spinal cord. Among these models is the 2-signal model of Nieuwkoop & Nigtevecht (1954), who suggested that an initial signal ('activation') from the organiser both neuralises and specifies the forebrain, while later signals ('transformation') from the same region progressively caudalise portions of this initial territory. An opposing idea emerged from the work of Otto Mangold (1933) and other members of the Spemann laboratory: 2 or more distinct organisers, emitting different signals, were proposed to be responsible for inducing the head, trunk and tail regions. Since then, evidence has accumulated that supports one or the other model, but it has been very difficult to distinguish between them. Recently, a considerable body of work from mouse embryos has been interpreted as favouring the latter model, and as suggesting that a 'head organiser', required for the induction of the forebrain, is spatially separate from the classic organiser (Hensen's node). An extraembryonic tissue, the 'anterior visceral endoderm' (AVE), was proposed to be the source of forebrain-inducing signals. It is difficult to find tissues that are directly equivalent embryologically or functionally to the AVE in other vertebrates, which led some (e.g. Kessel, 1998) to propose that mammals have evolved a new way of patterning the head. We will present evidence from the chick embryo showing that the hypoblast is embryologically and functionally equivalent to the mouse AVE. Like the latter, the hypoblast also plays a role in head development. However, it does not act like a true organiser. It induces pre-neural and pre-forebrain markers, but only transiently. Further development of neural and forebrain phenotypes requires additional signals not provided by the hypoblast. In addition, the hypoblast plays a role in directing cell movements in the adjacent epiblast. These movements distance the future forebrain territory from the developing organiser (Hensen's node), and we suggest that this is a mechanism to protect the forebrain from caudalising signals from the node. These mechanisms are consistent with all the findings obtained from the mouse to date. We conclude that the mechanisms responsible for setting up the forebrain and more caudal regions of the nervous system are probably similar among different classes of higher vertebrates. Moreover, while reconciling the two main models, our findings provide stronger support for Nieuwkoop's ideas than for the concept of multiple organisers, each inducing a distinct region of the CNS.
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Affiliation(s)
- ANN C.
FOLEY
- Department of Genetics and Development, Columbia University, New York, NY 10032, USA
| | - CLAUDIO D.
STERN
- Department of Genetics and Development, Columbia University, New York, NY 10032, USA
- Correspondence to Prof. Claudio Stern, Department of Anatomy and Developmental Biology, University College London, Gower Street, London WCIE 6BT, UK. Fax: +44 (0) 20 7679 2091; e-mail
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Mochizuki T, Karavanov AA, Curtiss PE, Ault KT, Sugimoto N, Watabe T, Shiokawa K, Jamrich M, Cho KW, Dawid IB, Taira M. Xlim-1 and LIM domain binding protein 1 cooperate with various transcription factors in the regulation of the goosecoid promoter. Dev Biol 2000; 224:470-85. [PMID: 10926781 DOI: 10.1006/dbio.2000.9778] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The homeobox genes Xlim-1 and goosecoid (gsc) are coexpressed in the Spemann organizer and later in the prechordal plate that acts as head organizer. Based on our previous finding that gsc is a possible target gene for Xlim-1, we studied the regulation of gsc transcription by Xlim-1 and other regulatory genes expressed at gastrula stages, by using gsc-luciferase reporter constructs injected into animal explants. A 492-bp upstream region of the gsc promoter responds to Xlim-1/3m, an activated form of Xlim-1, and to a combination of wild-type Xlim-1 and Ldb1, a LIM domain binding protein, supporting the view that gsc is a direct target of Xlim-1. Footprint and electrophoretic mobility shift assays with GST-homeodomain fusion proteins and embryo extracts overexpressing FLAG-tagged full-length proteins showed that the Xlim-1 homeodomain or Xlim-1/Ldb1 complex recognize several TAATXY core elements in the 492-bp upstream region, where XY is TA, TG, CA, or GG. Some of these elements are also bound by the ventral factor PV.1, whereas a TAATCT element did not bind Xlim-1 or PV.1 but did bind the anterior factors Otx2 and Gsc. These proteins modulate the activity of the gsc reporter in animal caps: Otx2 activates the reporter synergistically with Xlim-1 plus Ldb1, whereas Gsc and PV.1 strongly repress reporter activity. We show further, using animal cap assays, that the endogenous gsc gene was synergistically activated by Xlim-1, Ldb1, and Otx2 and that the endogenous otx2 gene was activated by Xlim-1/3m, and this activation was suppressed by the posterior factor Xbra. Based on these data, we propose a model for gene interactions in the specification of dorsoventral and anteroposterior differences in the mesoderm during gastrulation.
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Affiliation(s)
- T Mochizuki
- Laboratory of Molecular Embryology, Department of Biological Sciences, Graduate School of Science, University of Tokyo, Japan
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28
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Nakano H, Amemiya S, Shiokawa K, Taira M. RNA interference for the organizer-specific gene Xlim-1 in Xenopus embryos. Biochem Biophys Res Commun 2000; 274:434-9. [PMID: 10913356 DOI: 10.1006/bbrc.2000.3178] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Double-stranded RNA (dsRNA) interferes with gene expression in various species, a phenomenon known as RNA interference (RNAi). We show here that RNAi is also effective in modifying gene expression in Xenopus embryos. First, expression of an exogenous luciferase gene as a reporter in embryos was reduced by coinjection with dsRNA corresponding to the luciferase gene. Next, injection of dsRNA for Xlim-1, a homeobox gene suggested to be involved in Spemann organizer functions, reduced the endogenous level of Xlim-1 mRNA and produced embryos with reduced eyes or anterior truncation at high efficiency. In addition, injection of an antisense expression construct of Xlim-1 elicited phenotypes very similar to those of Xlim-1 dsRNA-injected embryos. These results indicate the effectiveness of RNAi for loss of function studies in Xenopus embryos, and the importance of Xlim-1 in head formation.
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MESH Headings
- Animals
- Blastomeres/drug effects
- Blastomeres/metabolism
- DNA, Antisense/pharmacology
- Embryo, Nonmammalian/abnormalities
- Embryo, Nonmammalian/drug effects
- Embryo, Nonmammalian/metabolism
- Embryo, Nonmammalian/pathology
- Gene Expression Regulation, Developmental/drug effects
- Gene Expression Regulation, Developmental/genetics
- Genes, Reporter
- Homeodomain Proteins/genetics
- Homeodomain Proteins/metabolism
- LIM-Homeodomain Proteins
- Luciferases/genetics
- Mesoderm/drug effects
- Mesoderm/pathology
- Microinjections
- Phenotype
- RNA, Antisense/pharmacology
- RNA, Double-Stranded/pharmacology
- RNA, Messenger/antagonists & inhibitors
- RNA, Messenger/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Transcription Factors
- Xenopus Proteins
- Xenopus laevis/embryology
- Xenopus laevis/genetics
- beta-Galactosidase/genetics
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Affiliation(s)
- H Nakano
- Laboratory of Molecular Embryology, Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
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29
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Tsang TE, Shawlot W, Kinder SJ, Kobayashi A, Kwan KM, Schughart K, Kania A, Jessell TM, Behringer RR, Tam PP. Lim1 activity is required for intermediate mesoderm differentiation in the mouse embryo. Dev Biol 2000; 223:77-90. [PMID: 10864462 DOI: 10.1006/dbio.2000.9733] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
During gastrulation and early organogenesis, Lim1 is expressed in the visceral endoderm, the anterior mesendoderm, and the lateral mesoderm that comprises the lateral plate and intermediate mesoderm. A previous study has reported that kidneys and gonads are missing in the Lim1 null mutants (W. Shawlot and R. R. Behringer, 1995, Nature 374, 425-430). Results of the present study show that in the early organogenesis stage mutant embryo, the intermediate mesoderm that contains the urogenital precursor tissues is disorganized and displays diminished expression of PAX2 and the Hoxb6-lacZ transgene. When posterior epiblast cells of the Lim1 null mutant embryo were transplanted to the primitive streak of wild-type host embryos, they were able to colonize the lateral plate and intermediate mesoderm of the host, suggesting that Lim1 activity is not essential for the allocation of epiblast cells to these mesodermal lineages. However, most of the mutant cells that colonized the lateral and intermediate mesoderm of the host embryo did not express the Hoxb6-lacZ transgene, except for some cells that were derived from the distal part of the posterior epiblast. Lim1 activity may therefore be required for the full expression of this transgene that normally marks the differentiation of the lateral plate and intermediate mesoderm.
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Affiliation(s)
- T E Tsang
- Embyology Unit, University of Sydney, New South Wales, Australia
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30
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Strong CF, Barnett MW, Hartman D, Jones EA, Stott D. Xbra3 induces mesoderm and neural tissue in Xenopus laevis. Dev Biol 2000; 222:405-19. [PMID: 10837128 DOI: 10.1006/dbio.2000.9710] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Homologues of the murine Brachyury gene have been shown to be involved in mesoderm formation in several vertebrate species. In frogs, the Xenopus Brachyury homologue, Xbra, is required for normal formation of posterior mesoderm. We report the characterisation of a second Brachyury homologue from Xenopus, Xbra3, which has levels of identity with mouse Brachyury similar to those of Xbra. Xbra3 encodes a nuclear protein expressed in mesoderm in a temporal and spatial manner distinct from that observed for Xbra. Xbra3 expression is induced by mesoderm-inducing factors and overexpression of Xbra3 can induce mesoderm formation in animal caps. In contrast to Xbra, Xbra3 is also able to cause the formation of neural tissue in animal caps. Xbra3 overexpression induces both geminin and Xngnr-1, suggesting that Xbra3 can play a role in the earliest stages of neural induction. Xbra3 induces posterior nervous tissue by an FGF-dependent pathway; a complete switch to anterior neural tissue can be effected by the inhibition of FGF signalling. Neither noggin, chordin, follistatin, nor Xnr3 is induced by Xbra3 to an extent different from their induction by Xbra nor is BMP4 expression differentially affected.
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Affiliation(s)
- C F Strong
- Cell and Molecular Development Group, University of Warwick, Coventry, CV4 7AL, United Kingdom
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31
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O'Keefe DD, Thor S, Thomas JB. Function and specificity of LIM domains in Drosophila nervous system and wing development. Development 1998; 125:3915-23. [PMID: 9729499 DOI: 10.1242/dev.125.19.3915] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
LIM domains are found in a variety of proteins, including cytoplasmic and nuclear LIM-only proteins, LIM-homeodomain (LIM-HD) transcription factors and LIM-kinases. Although the ability of LIM domains to interact with other proteins has been clearly established in vitro and in cultured cells, their in vivo function is unknown. Here we use Drosophila to test the roles of the LIM domains of the LIM-HD family member Apterous (Ap) in wing and nervous system development. Using a rescuing assay of the ap mutant phenotype, we have found that the LIM domains are essential for Ap function. Furthermore, expression of LIM domains alone can act in a dominant-negative fashion to disrupt Ap function. The Ap LIM domains can be replaced by those of another family member to generate normal wing structure, but LIM domains are not interchangeable during axon pathfinding of the Ap neurons. This suggests that the Ap LIM domains mediate different protein interactions in different developmental processes, and that LIM domains can participate in conferring specificity of target gene selection.
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Affiliation(s)
- D D O'Keefe
- Department of Neurosciences, School of Medicine, University of California, San Diego, La Jolla, California 92093, USA
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32
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Szebenyi G, Fallon JF. Fibroblast growth factors as multifunctional signaling factors. INTERNATIONAL REVIEW OF CYTOLOGY 1998; 185:45-106. [PMID: 9750265 DOI: 10.1016/s0074-7696(08)60149-7] [Citation(s) in RCA: 356] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The fibroblast growth factor (FGF) family consists of at least 15 structurally related polypeptide growth factors. Their expression is controlled at the levels of transcription, mRNA stability, and translation. The bioavailability of FGFs is further modulated by posttranslational processing and regulated protein trafficking. FGFs bind to receptor tyrosine kinases (FGFRs), heparan sulfate proteoglycans (HSPG), and a cysteine-rich FGF receptor (CFR). FGFRs are required for most biological activities of FGFs. HSPGs alter FGF-FGFR interactions and CFR participates in FGF intracellular transport. FGF signaling pathways are intricate and are intertwined with insulin-like growth factor, transforming growth factor-beta, bone morphogenetic protein, and vertebrate homologs of Drosophila wingless activated pathways. FGFs are major regulators of embryonic development: They influence the formation of the primary body axis, neural axis, limbs, and other structures. The activities of FGFs depend on their coordination of fundamental cellular functions, such as survival, replication, differentiation, adhesion, and motility, through effects on gene expression and the cytoskeleton.
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Affiliation(s)
- G Szebenyi
- Anatomy Department, University of Wisconsin, Madison 53706, USA
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33
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Rebagliati MR, Toyama R, Fricke C, Haffter P, Dawid IB. Zebrafish nodal-related genes are implicated in axial patterning and establishing left-right asymmetry. Dev Biol 1998; 199:261-72. [PMID: 9698446 DOI: 10.1006/dbio.1998.8935] [Citation(s) in RCA: 238] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nodal-related 1 (ndr1) and nodal-related 2 (ndr2) genes in zebrafish encode members of the nodal subgroup of the transforming growth factor-beta superfamily. We report the expression patterns and functional characteristics of these factors, implicating them in the establishment of dorsal-ventral polarity and left-right asymmetry. Ndr1 is expressed maternally, and ndr1 and ndr2 are expressed during blastula stage in the blastoderm margin. During gastrulation, ndr expression subdivides the shield into two domains: a small group of noninvoluting cells, the dorsal forerunner cells, express ndr1, while ndr2 RNA is found in the hypoblast layer of the shield and later in notochord, prechordal plate, and overlying anterior neurectoderm. During somitogenesis, ndr2 is expressed asymmetrically in the lateral plate as are nodal-related genes of other organisms, and in a small domain in the left diencephalon, providing the first observation of asymmetric gene expression in the embryonic forebrain. RNA injections into Xenopus animal caps showed that Ndr1 acts as a mesoderm inducer, whereas Ndr2 is an efficient neural but very inefficient mesoderm inducer. We suggest that Ndr1 has a role in mesoderm induction, while Ndr2 is involved in subsequent specification and patterning of the nervous system and establishment of laterality.
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Affiliation(s)
- M R Rebagliati
- Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
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34
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Abstract
The organizer is formed in an equatorial sector of the blastula stage amphibian embryo by cells that have responded to two maternal agents: a general mesoendoderm inducer (involving the TFG-beta signaling pathway) and a dorsal modifier (probably involving the Wnt signaling pathway). The meso-endoderm inducer is secreted by most vegetal cells, those containing maternal materials that had been localized in the vegetal hemisphere of the oocyte during oogenesis. As a consequence of the inducer's distribution and action, the competence domains of prospective ectoderm, mesoderm, and endoderm are established in an animal-to-vegetal order in the blastula. The dorsal modifier signal is secreted by a sector of cells of the animal and vegetal hemispheres on one side of the blastula. These cells contain maternal materials transported there in the first cell cycle from the vegetal pole of the egg along microtubules aligned by cortical rotation. The Nieuwkoop center is the region of blastula cells secreting both maternal signals, and hence specifying the organizer in an equatorial sector. Final steps of organizer formation at the late blastula or early gastrula stage may involve locally secreted zygotic signals as well. At the gastrula stage, the organizer secretes a variety of zygotic proteins that act as antagonists to various members of the BMP and Wnt families of ligands, which are secreted by cells of the competence domains surrounding the organizer. BMPs and Wnts favor ventral development, and cells near the organizer are protected from these agents by the organizer's inducers. The nearby cells are derepressed in their inherent capacity for dorsal development, which is apparent in the neural induction of the ectoderm, dorsalization of the mesoderm, and anteriorization of the endoderm. The organizer also engages in extensive specialized morphogenesis, which brings it within range of responsive cell groups. It also self-differentiates to a variety of axial tissues of the body.
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Affiliation(s)
- R Harland
- Department of Molecular and Cell Biology, University of California, Berkeley 94720, USA.
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35
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Kim J, Lin JJ, Xu RH, Kung HF. Mesoderm induction by heterodimeric AP-1 (c-Jun and c-Fos) and its involvement in mesoderm formation through the embryonic fibroblast growth factor/Xbra autocatalytic loop during the early development of Xenopus embryos. J Biol Chem 1998; 273:1542-50. [PMID: 9430694 DOI: 10.1074/jbc.273.3.1542] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We have previously demonstrated the involvement of AP-1/Jun in fibroblast growth factor (FGF) signaling by loss-of-function assay (Dong, Z., Xu, R.-H., Kim, J., Zhan, S.-N., Ma, W.-Y., Colburn, N. H., and Kung, H. (1996) J. Biol. Chem. 271, 9942-9946). Further investigations by gain-of-function are reported in this study. AP-1 transactivation activity was increased by the treatment of animal cap explants with FGF. Ectopic overexpression of two components of AP-1 (c-jun and c-fos together, but not alone) produced posteriorized embryos and induced mesoderm formation in animal cap explants, indicating that both AP-1 heterodimers are required for mesoderm induction. Since Ras/AP-1 functions downstream of FGF signaling, we then tested the involvement of Ras/AP-1 in mesoderm maintenance mediated by embryonic FGF/Xbra using dominant-negative mutants. Mesoderm maintenance mediated by embryonic FGF/Xbra was blocked by dominant-negative mutants of Ras/AP-1, and AP-1 enhanced the expression of Xbra. Further studies demonstrated the inhibition of Ras/AP-1-mediated mesoderm formation by dominant-negative mutants of the FGF receptor and Xbra. These results indicate that Ras/AP-1 and FGF/Xbra signals are involved in the mesoderm maintenance machinery and mesoderm formation through the synergistic action of the diversified signal pathways derived from the FGF/Xbra autocatalytic loop.
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Affiliation(s)
- J Kim
- Laboratory of Biochemical Physiology, NCI-Frederick Cancer Research and Development Center, National Institutes of Health, Maryland 21702-1201, USA
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36
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Abstract
We have asked how posterior neural tissue is patterned in Xenopus by assaying the involvement of endogenous retinoic acid (RA) in this process and by using the labial Hox gene, HoxD1, as a posterior marker. Although RA is able to inhibit anterior gene expression and activate expression of more posterior genes, the normal role of retinoids in anteroposterior (A/P) patterning is unclear. HoxD1 is an early posterior neurectodermal marker, expressed from midgastrula with a later anterior expression limit in the future hindbrain. We previously showed that HoxD1 was induced as an immediate early response to retinoic acid in naive ectoderm (animal caps). Here, we use a truncated RARalpha2.2 receptor (RARDelta) to dominantly interfere with retinoid signaling. In embryos injected with RARDelta expression of HoxD1 is eliminated. Conjugates of ectoderm and dorsolateral mesoderm show that retinoid receptors are required in the ectoderm for HoxD1 induction. Further, expression of Krox-20 in r3 and r5 of the presumptive hindbrain is compressed into a single stripe that suggests elimination of r5. RARalpha2.2 expression almost precisely overlaps that of HoxD1, suggesting that this receptor may normally activate HoxD1. Expression of neither more anterior genes including cement gland, forebrain, and midbrain markers nor a more posterior spinal cord marker is affected by RARDelta. These data suggest that the posterior hindbrain is the region of the nervous system most sensitive to retinoid loss. Finally, we compare the ability of RA and fibroblast growth factor (FGF) to posteriorize isolated anterior neurectoderm and show that both factors can act directly on this substrate. RA acts in a more anterior domain than does FGF; however, neither factor is equivalent to the natural posteriorizing capacity of the posterior mesoderm. We propose that endogenous retinoid and FGF signals pattern largely nonoverlapping regions along the A/P axis and that posterior neural patterning requires multiple inducers.
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Affiliation(s)
- P J Kolm
- Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, Massachusetts 02142, USA
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37
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Studies on the role of fibroblast growth factor signaling in neurogenesis using conjugated/aged animal caps and dorsal ectoderm-grafted embryos. J Neurosci 1997. [PMID: 9278524 DOI: 10.1523/jneurosci.17-18-06892.1997] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Basic fibroblast growth factor (bFGF) has been shown to induce neural fate in dissociated animal cap (AC) cells or in AC explants cultured in low calcium and magnesium concentrations. However, long-term disclosure of the cap may cause diffusion of the secreted molecule bone morphogenetic protein 4 (BMP-4), a neural inhibitor present in the AC. This may contribute to the subsequent neurogenesis induced by bFGF. Here we used conjugated and aged blastula AC to avoid diffusion of endogenous molecules from the AC. Unlike noggin, bFGF failed to induce neural tissue in this system. However, it enhanced neuralization elicited by a dominant negative BMP receptor (DN-BR) that inhibits the BMP-4 signaling. Posterior neural markers were turned on by bFGF in AC expressing DN-BR or chordin. Blocking the endogenous FGF signal with a dominant negative FGF receptor (XFD) mainly inhibited development of posterior neural tissue in neuralized ACs. These in vitro studies were confirmed in vivo in embryos grafted with XFD-expressing ACs in the place of neuroectoderm. Expression of some regional neural markers was inhibited, although markers for muscle and posterior notochord were still detectable in the grafted embryos, suggesting that XFD specifically affected neurogenesis but not the dorsal mesoderm. The use of these in vitro and in vivo model systems provides new evidence that FGF, although unable to initiate neurogenesis on its own, is required for neural induction as well as for posteriorization.
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38
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Xu RH, Kim J, Taira M, Sredni D, Kung H. Studies on the role of fibroblast growth factor signaling in neurogenesis using conjugated/aged animal caps and dorsal ectoderm-grafted embryos. J Neurosci 1997; 17:6892-8. [PMID: 9278524 PMCID: PMC6573287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Basic fibroblast growth factor (bFGF) has been shown to induce neural fate in dissociated animal cap (AC) cells or in AC explants cultured in low calcium and magnesium concentrations. However, long-term disclosure of the cap may cause diffusion of the secreted molecule bone morphogenetic protein 4 (BMP-4), a neural inhibitor present in the AC. This may contribute to the subsequent neurogenesis induced by bFGF. Here we used conjugated and aged blastula AC to avoid diffusion of endogenous molecules from the AC. Unlike noggin, bFGF failed to induce neural tissue in this system. However, it enhanced neuralization elicited by a dominant negative BMP receptor (DN-BR) that inhibits the BMP-4 signaling. Posterior neural markers were turned on by bFGF in AC expressing DN-BR or chordin. Blocking the endogenous FGF signal with a dominant negative FGF receptor (XFD) mainly inhibited development of posterior neural tissue in neuralized ACs. These in vitro studies were confirmed in vivo in embryos grafted with XFD-expressing ACs in the place of neuroectoderm. Expression of some regional neural markers was inhibited, although markers for muscle and posterior notochord were still detectable in the grafted embryos, suggesting that XFD specifically affected neurogenesis but not the dorsal mesoderm. The use of these in vitro and in vivo model systems provides new evidence that FGF, although unable to initiate neurogenesis on its own, is required for neural induction as well as for posteriorization.
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Affiliation(s)
- R H Xu
- Intramural Research Support Program, Science Applications International Corporation-Frederick, Frederick, Maryland 21702-1201, USA
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39
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Rebbert ML, Dawid IB. Transcriptional regulation of the Xlim-1 gene by activin is mediated by an element in intron I. Proc Natl Acad Sci U S A 1997; 94:9717-22. [PMID: 9275190 PMCID: PMC23256 DOI: 10.1073/pnas.94.18.9717] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The Xlim-1 gene is activated in the late blastula stage of Xenopus embryogenesis in the mesoderm, and its RNA product becomes concentrated in the Spemann organizer at early gastrula stage. A major regulator of early expression of Xlim-1 is activin or an activin-like signal. We report experiments aiming to identify the activin response element in the Xlim-1 gene. The 5' flanking region of the gene contains a constitutive promoter that is not activin responsive, whereas sequences in the first intron mediate repression of basal promoter activity and stimulation by activin. An intron-derived fragment of 212 nt is the smallest element that could mediate activin responsiveness. Nodal and act-Vg1, factors with signaling properties similar to activin, also stimulated Xlim-1 reporter constructs, whereas BMP-4 did not stimulate or repress the constructs. The mechanism of activin regulation of Xlim-1 and the sequence of the response element are distinct from activin response elements of other genes studied so far.
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Affiliation(s)
- M L Rebbert
- Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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40
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Abstract
A novel LIM class homeobox gene, lim6, was isolated from a zebrafish embryonic cDNA library. The encoded protein shares a high degree of sequence similarity with the previously described Lim1 and Lim5 proteins. This study compares the spatial and temporal expression pattern of the closely related lim6 and lim1 genes during early embryogenesis. Generally, lim6 mRNA was found at rather low amounts compared to lim1 mRNA. At the shield stage, lim6 mRNA, similar to lim1 mRNA, was predominantly expressed in the shield. Lim6 was transiently expressed in a restricted region of the anterior neural plate at the bud stage, distinct from the expression of lim1 in the notochord and the pronephros and pronephric ducts. During the segmentation period, the lim6 gene started to be expressed in single cells in the spinal cord, followed by a gradually increasing wide-spread expression throughout the CNS. During this stage, lim1 mRNA disappeared in the notochord and pronephric ducts and was found in the pronephroi and single cells in the CNS. In 24 hr embryos, lim6 and lim1 were expressed in the fore-, mid-, and hindbrain and the spinal cord, except that lim1 mRNA was limited to two small domains in the telencephalon, whereas lim6 mRNA was widely expressed in this region. A comparison of expression of lim1 and lim6 and of the previously characterized lim5 show that, in spite of close sequence similarity, distinct expression patterns imply nonredundant functions for each member of this group of genes.
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Affiliation(s)
- R Toyama
- Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
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