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Manning E, Placzek M. Organizing activities of axial mesoderm. Curr Top Dev Biol 2024; 157:83-123. [PMID: 38556460 DOI: 10.1016/bs.ctdb.2024.02.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/02/2024]
Abstract
For almost a century, developmental biologists have appreciated that the ability of the embryonic organizer to induce and pattern the body plan is intertwined with its differentiation into axial mesoderm. Despite this, we still have a relatively poor understanding of the contribution of axial mesoderm to induction and patterning of different body regions, and the manner in which axial mesoderm-derived information is interpreted in tissues of changing competence. Here, with a particular focus on the nervous system, we review the evidence that axial mesoderm notochord and prechordal mesoderm/mesendoderm act as organizers, discuss how their influence extends through the different axes of the developing organism, and describe how the ability of axial mesoderm to direct morphogenesis impacts on its role as a local organizer.
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Affiliation(s)
- Elizabeth Manning
- School of Biosciences, University of Sheffield, Sheffield, United Kingdom; Bateson Centre, University of Sheffield, Sheffield, United Kingdom
| | - Marysia Placzek
- School of Biosciences, University of Sheffield, Sheffield, United Kingdom; Bateson Centre, University of Sheffield, Sheffield, United Kingdom; Neuroscience Institute, University of Sheffield, Sheffield, United Kingdom.
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2
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Ulmer B, Tingler M, Kurz S, Maerker M, Andre P, Mönch D, Campione M, Deißler K, Lewandoski M, Thumberger T, Schweickert A, Fainsod A, Steinbeißer H, Blum M. A novel role of the organizer gene Goosecoid as an inhibitor of Wnt/PCP-mediated convergent extension in Xenopus and mouse. Sci Rep 2017; 7:43010. [PMID: 28220837 PMCID: PMC5318956 DOI: 10.1038/srep43010] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 01/18/2017] [Indexed: 12/12/2022] Open
Abstract
Goosecoid (Gsc) expression marks the primary embryonic organizer in vertebrates and beyond. While functions have been assigned during later embryogenesis, the role of Gsc in the organizer has remained enigmatic. Using conditional gain-of-function approaches in Xenopus and mouse to maintain Gsc expression in the organizer and along the axial midline, neural tube closure defects (NTDs) arose and dorsal extension was compromised. Both phenotypes represent convergent extension (CE) defects, arising from impaired Wnt/planar cell polarity (PCP) signaling. Dvl2 recruitment to the cell membrane was inhibited by Gsc in Xenopus animal cap assays and key Wnt/PCP factors (RhoA, Vangl2, Prickle, Wnt11) rescued Gsc-mediated NTDs. Re-evaluation of endogenous Gsc functions in MO-mediated gene knockdown frog and knockout mouse embryos unearthed PCP/CE-related phenotypes as well, including cartilage defects in Xenopus and misalignment of inner ear hair cells in mouse. Our results assign a novel function to Gsc as an inhibitor of Wnt/PCP-mediated CE. We propose that in the organizer Gsc represses CE as well: Gsc-expressing prechordal cells, which leave the organizer first, migrate and do not undergo CE like the Gsc-negative notochordal cells, which subsequently emerge from the organizer. In this model, Gsc provides a switch between cell migration and CE, i.e. cell intercalation.
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Affiliation(s)
- Bärbel Ulmer
- University of Hohenheim, Garbenstr. 30, 70599 Stuttgart, Germany
| | - Melanie Tingler
- University of Hohenheim, Garbenstr. 30, 70599 Stuttgart, Germany
| | - Sabrina Kurz
- University of Hohenheim, Garbenstr. 30, 70599 Stuttgart, Germany
| | - Markus Maerker
- University of Hohenheim, Garbenstr. 30, 70599 Stuttgart, Germany
| | - Philipp Andre
- University of Hohenheim, Garbenstr. 30, 70599 Stuttgart, Germany
| | - Dina Mönch
- University of Hohenheim, Garbenstr. 30, 70599 Stuttgart, Germany
| | - Marina Campione
- University of Hohenheim, Garbenstr. 30, 70599 Stuttgart, Germany
| | - Kirsten Deißler
- University of Hohenheim, Garbenstr. 30, 70599 Stuttgart, Germany
| | - Mark Lewandoski
- Genetics of Vertebrate Development Section, Cancer and Developmental Biology Lab, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA
| | | | - Axel Schweickert
- University of Hohenheim, Garbenstr. 30, 70599 Stuttgart, Germany
| | - Abraham Fainsod
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Hebrew University, Jerusalem 9112102, Israel
| | - Herbert Steinbeißer
- Institute of Human Genetics, University Hospital Heidelberg, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany
| | - Martin Blum
- University of Hohenheim, Garbenstr. 30, 70599 Stuttgart, Germany
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Perry KJ, Lyons DC, Truchado-Garcia M, Fischer AHL, Helfrich LW, Johansson KB, Diamond JC, Grande C, Henry JQ. Deployment of regulatory genes during gastrulation and germ layer specification in a model spiralian mollusc Crepidula. Dev Dyn 2016. [PMID: 26197970 DOI: 10.1002/dvdy.24308] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND During gastrulation, endoderm and mesoderm are specified from a bipotential precursor (endomesoderm) that is argued to be homologous across bilaterians. Spiralians also generate mesoderm from ectodermal precursors (ectomesoderm), which arises near the blastopore. While a conserved gene regulatory network controls specification of endomesoderm in deuterostomes and ecdysozoans, little is known about genes controlling specification or behavior of either source of spiralian mesoderm or the digestive tract. RESULTS Using the mollusc Crepidula, we examined conserved regulatory factors and compared their expression to fate maps to score expression in the germ layers, blastopore lip, and digestive tract. Many genes were expressed in both ecto- and endomesoderm, but only five were expressed in ectomesoderm exclusively. The latter may contribute to epithelial-to-mesenchymal transition seen in ectomesoderm. CONCLUSIONS We present the first comparison of genes expressed during spiralian gastrulation in the context of high-resolution fate maps. We found variation of genes expressed in the blastopore lip, mouth, and cells that will form the anus. Shared expression of many genes in both mesodermal sources suggests that components of the conserved endomesoderm program were either co-opted for ectomesoderm formation or that ecto- and endomesoderm are derived from a common mesodermal precursor that became subdivided into distinct domains during evolution.
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Affiliation(s)
- Kimberly J Perry
- University of Illinois, Department of Cell and Developmental Biology, Urbana, Illinois
| | | | - Marta Truchado-Garcia
- Departamento de Biología Molecular and Centro de Biología Molecular, "Severo Ochoa" (CSIC, Universidad Autónoma de Madrid), Madrid, Spain
| | - Antje H L Fischer
- Department of Metabolic Biochemistry, Ludwig-Maximilians-University, Munich, Germany.,Marine Biological Laboratory, Woods Hole, Massachusetts
| | | | - Kimberly B Johansson
- Marine Biological Laboratory, Woods Hole, Massachusetts.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts
| | | | - Cristina Grande
- Departamento de Biología Molecular and Centro de Biología Molecular, "Severo Ochoa" (CSIC, Universidad Autónoma de Madrid), Madrid, Spain
| | - Jonathan Q Henry
- University of Illinois, Department of Cell and Developmental Biology, Urbana, Illinois
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4
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Nouri M, Ratther E, Stylianou N, Nelson CC, Hollier BG, Williams ED. Androgen-targeted therapy-induced epithelial mesenchymal plasticity and neuroendocrine transdifferentiation in prostate cancer: an opportunity for intervention. Front Oncol 2014; 4:370. [PMID: 25566507 PMCID: PMC4274903 DOI: 10.3389/fonc.2014.00370] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Accepted: 12/04/2014] [Indexed: 01/22/2023] Open
Abstract
Androgens regulate biological pathways to promote proliferation, differentiation, and survival of benign and malignant prostate tissue. Androgen receptor (AR) targeted therapies exploit this dependence and are used in advanced prostate cancer to control disease progression. Contemporary treatment regimens involve sequential use of inhibitors of androgen synthesis or AR function. Although targeting the androgen axis has clear therapeutic benefit, its effectiveness is temporary, as prostate tumor cells adapt to survive and grow. The removal of androgens (androgen deprivation) has been shown to activate both epithelial-to-mesenchymal transition (EMT) and neuroendocrine transdifferentiation (NEtD) programs. EMT has established roles in promoting biological phenotypes associated with tumor progression (migration/invasion, tumor cell survival, cancer stem cell-like properties, resistance to radiation and chemotherapy) in multiple human cancer types. NEtD in prostate cancer is associated with resistance to therapy, visceral metastasis, and aggressive disease. Thus, activation of these programs via inhibition of the androgen axis provides a mechanism by which tumor cells can adapt to promote disease recurrence and progression. Brachyury, Axl, MEK, and Aurora kinase A are molecular drivers of these programs, and inhibitors are currently in clinical trials to determine therapeutic applications. Understanding tumor cell plasticity will be important in further defining the rational use of androgen-targeted therapies clinically and provides an opportunity for intervention to prolong survival of men with metastatic prostate cancer.
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Affiliation(s)
- Mannan Nouri
- Vancouver Prostate Centre , Vancouver, BC , Canada ; The University of British Columbia , Vancouver, BC , Canada
| | - Ellca Ratther
- Australian Prostate Cancer Research Centre Queensland, Institute of Health and Biomedical Innovation, Princess Alexandra Hospital, Queensland University of Technology , Brisbane, QLD , Australia ; Australian Prostate Cancer Research Centre Queensland, Translational Research Institute, Princess Alexandra Hospital, Queensland University of Technology , Brisbane, QLD , Australia
| | - Nataly Stylianou
- Australian Prostate Cancer Research Centre Queensland, Institute of Health and Biomedical Innovation, Princess Alexandra Hospital, Queensland University of Technology , Brisbane, QLD , Australia ; Australian Prostate Cancer Research Centre Queensland, Translational Research Institute, Princess Alexandra Hospital, Queensland University of Technology , Brisbane, QLD , Australia
| | - Colleen C Nelson
- Australian Prostate Cancer Research Centre Queensland, Institute of Health and Biomedical Innovation, Princess Alexandra Hospital, Queensland University of Technology , Brisbane, QLD , Australia ; Australian Prostate Cancer Research Centre Queensland, Translational Research Institute, Princess Alexandra Hospital, Queensland University of Technology , Brisbane, QLD , Australia
| | - Brett G Hollier
- Australian Prostate Cancer Research Centre Queensland, Institute of Health and Biomedical Innovation, Princess Alexandra Hospital, Queensland University of Technology , Brisbane, QLD , Australia ; Australian Prostate Cancer Research Centre Queensland, Translational Research Institute, Princess Alexandra Hospital, Queensland University of Technology , Brisbane, QLD , Australia
| | - Elizabeth D Williams
- Australian Prostate Cancer Research Centre Queensland, Institute of Health and Biomedical Innovation, Princess Alexandra Hospital, Queensland University of Technology , Brisbane, QLD , Australia ; Australian Prostate Cancer Research Centre Queensland, Translational Research Institute, Princess Alexandra Hospital, Queensland University of Technology , Brisbane, QLD , Australia ; Department of Surgery, St Vincent's Hospital, The University of Melbourne , Melbourne, VIC , Australia ; Monash University , Melbourne, VIC , Australia
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5
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Morphology of the facial motor nuclei in a rat model of autism during early development. Int J Dev Neurosci 2012; 31:138-44. [PMID: 23253376 DOI: 10.1016/j.ijdevneu.2012.12.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 11/22/2012] [Accepted: 12/08/2012] [Indexed: 11/22/2022] Open
Abstract
The development of facial nuclei in animal models of disease is poorly understood, but autism is sometimes associated with facial palsy. In the present study, to investigate migration of facial neurons and initial facial nucleus formation in an animal model of autism, rat embryos were treated with valproic acid (VPA) in utero at embryonic day (E) 9.5 and their facial nuclei were analyzed by in situ hybridization at E13.5, E14.5 and E15.5. Signals for Tbx20, which is expressed in early motor neurons, appeared near the floor plate at the level of the vestibular ganglion and extended caudolaterally, where they became ovoid in shape. This pattern of development was similar between control and VPA-exposed embryos. However, measurements of the migratory pathway and the size of the facial nuclei revealed that exposure to VPA hindered the caudal migration of neurons to the facial nuclei. Signals for cadherin 8, which is expressed in mature facial nuclei, revealed that exposure to VPA caused a significant reduction in the size of the facial nuclei. Our findings provide the first quantitative description of tangential migration and nucleus formation in the developing hindbrain in a rat model of autism.
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6
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Tashiro Y, Oyabu A, Imura Y, Uchida A, Narita N, Narita M. Morphological abnormalities of embryonic cranial nerves after in utero exposure to valproic acid: implications for the pathogenesis of autism with multiple developmental anomalies. Int J Dev Neurosci 2011; 29:359-64. [DOI: 10.1016/j.ijdevneu.2011.03.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2010] [Revised: 03/25/2011] [Accepted: 03/25/2011] [Indexed: 11/29/2022] Open
Affiliation(s)
- Yasura Tashiro
- Department of Anatomy IIGraduate School of MedicineMie University2‐174 EdobashiTsu‐cityMieJapan
| | - Akiko Oyabu
- Department of Anatomy IIGraduate School of MedicineMie University2‐174 EdobashiTsu‐cityMieJapan
| | - Yoshio Imura
- Department of Anatomy IIGraduate School of MedicineMie University2‐174 EdobashiTsu‐cityMieJapan
| | - Atsuko Uchida
- Department of Anatomy IIGraduate School of MedicineMie University2‐174 EdobashiTsu‐cityMieJapan
| | - Naoko Narita
- Department of EducationBunkyo UniversityMieJapan
| | - Masaaki Narita
- Department of Anatomy IIGraduate School of MedicineMie University2‐174 EdobashiTsu‐cityMieJapan
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7
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Kornikova ES, Troshina TG, Kremnyov SV, Beloussov LV. Neuro-mesodermal patterns in artificially deformed embryonic explants: a role for mechano-geometry in tissue differentiation. Dev Dyn 2010; 239:885-96. [PMID: 20140909 DOI: 10.1002/dvdy.22238] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The mutual arrangement of neural and mesodermal rudiments in artificially bent double explants of Xenopus laevis suprablastoporal areas was compared with that of intact explants. While some of the bent explants straightened or became spherical, most retained and actively reinforced the imposed curvature, creating folds on their concave sides and expanding convex surfaces. In the intact explants, the arrangement of neural and mesodermal rudiments exhibited a distinct antero-posterior polarity, with some variability. In the bent explants, this polarity was lost: the neural rudiments were shifted towards concave while the mesodermal tissues moved towards the convex side, embracing the neural rudiments in a horseshoe-shaped manner. We associate these drastic changes in neuro-mesodermal patterning with the active extension and contraction of the convex and concave sides, respectively, triggered by the imposed deformations. We speculate that similar events are responsible for the establishment of neuro-mesodermal patterns during normal development.
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Affiliation(s)
- E S Kornikova
- Department of Embryology, Faculty of Biology, Moscow State University, Moscow, Russia
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8
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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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9
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Shan ZY, Shen JL, Li QM, Wang Y, Huang XY, Guo TY, Liu HW, Lei L, Jin LH. pCREB is involved in neural induction of mouse embryonic stem cells by RA. Anat Rec (Hoboken) 2008; 291:519-26. [PMID: 18383274 DOI: 10.1002/ar.20686] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Mouse embryonic stem (ES) cells can be induced by various chemicals to differentiate into a variety of cell types in vitro. In our study, retinoic acid (RA), one of the most important inducers, used at a concentration of 5 microM, was found to induce the differentiation of ES cells into neural progenitor cells (NPCs). During embryoid body (EB) differentiation, the level of active cyclic AMP response element-binding protein (CREB) was relatively high when 5 microM RA treatment was performed. Inhibition of CREB activity committed EBs to becoming other germ layers, whereas increased expression of CREB enhanced NPC differentiation. Moreover, RA increased the expression of active CREB by enhancing the activity of JNK. Our research suggests that CREB plays a role in RA-induced NPC differentiation by increasing the expression of active JNK.
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Affiliation(s)
- Zhi-Yan Shan
- Department of Histology and Embryology, Harbin Medical University, China
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10
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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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11
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Sakai M. Cell-autonomous and inductive processes among three embryonic domains control dorsal-ventral and anterior-posterior development of Xenopus laevis. Dev Growth Differ 2007; 50:49-62. [DOI: 10.1111/j.1440-169x.2007.00975.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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12
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Beloussov LV, Korvin-Pavlovskaya EG, Luchinskaya NN, Kornikova ES. Role of cooperative cell movements and mechano-geometric constrains in patterning of axial rudiments in Xenopus laevis embryos. Russ J Dev Biol 2007. [DOI: 10.1134/s1062360407030034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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13
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Joshi-Banka D, Paranjape S, Ghaskadbi S, Modak SP. Post-nodal mesoblast caudalizes the host axis and inhibits cell population growth, and induces new primitive streaks in chick embryos. Dev Growth Differ 2002; 44:169-80. [PMID: 11940103 DOI: 10.1046/j.1440-169x.2002.00632.x] [Citation(s) in RCA: 2] [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
One to eight post-nodal fragments (PN) or Hensen's nodes (HN) from full primitive streak stage chick embryos were transplanted onto the area pellucida or area opaca of stage 4 embryos and cultured for 20 h. Thirteen morphological and numerical parameters were affected in the host embryos and analyzed by multiple logistic regression for parametric hierarchy. In the area pellucida, both PN and HN transplants inhibited cell population growth while only PN caudalized the host axis and induced supernumerary primitive streaks expressing the mesoderm-specific gene Brachyury. In the area opaca, neither grafts influenced host axis morphogenesis, but PN inhibited the cell population growth significantly. Tracking [(3)H]TdR labeled grafts showed that PN cells migrated towards the host axis and participated in the formation of supernumerary somites and hearts. When placed near the host axis, PN caudalized it and inhibited cell population growth.
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Affiliation(s)
- Deepti Joshi-Banka
- Molecular Embryology Research Laboratory, Department of Zoology, University of Pune, Ganeshkhind Road, Pune 411016, India
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14
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Tour E, Pillemer G, Gruenbaum Y, Fainsod A. Gbx2 interacts with Otx2 and patterns the anterior-posterior axis during gastrulation in Xenopus. Mech Dev 2002; 112:141-51. [PMID: 11850185 DOI: 10.1016/s0925-4773(01)00653-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Anterior-posterior patterning of the embryo requires the activity of multiple homeobox genes among them Hox, caudal (Cdx, Xcad) and Otx2. During early gastrulation, Otx2 and Xcad2 establish a cross-regulatory network, which is an early event in the anterior-posterior patterning of the embryo. As gastrulation proceeds and the embryo elongates, a new domain forms, which expresses neither, Otx2 nor Xcad2 genes. Early transcription of the Xenopus Gbx2 homologue, Xgbx2a, is spatially restricted between Otx2 and Xcad2. When overexpressed, Otx2 and Xcad2 repress Xgbx2a transcription, suggesting their role in setting the early Xgbx2a expression domain. Homeobox genes have been shown to play crucial roles in the specification of the vertebrate brain. The border between the transcription domains of Otx2 and Gbx2 is the earliest known marker of the region where the midbrain/hindbrain boundary (MHB) organizer will develop. Xgbx2a is a negative regulator of Otx2 and a weak positive regulator of Xcad2. Using obligatory activator and repressor versions of Xgbx2a, we demonstrate that, during early embryogenesis, Xgbx2a acts as a transcriptional repressor. In addition, taking advantage of hormone-inducible versions of Xgbx2a and its antimorph, we show that the ability of Xgbx2a to induce head malformations is restricted to gastrula stages and correlates with its ability to repress Otx2 during the same developmental stages. We therefore suggest that the earliest known step of the MHB formation, the establishment of Otx2/Gbx2 boundary, takes place via mutual inhibitory interactions between these two genes and this process begins as early as at midgastrulation.
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Affiliation(s)
- Ella Tour
- Department of Cellular Biochemistry and Human Genetics, Hebrew University-Hadassah Medical School, P.O. Box 12272, Jerusalem 91120, Israel
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15
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Holland LZ. Heads or tails? Amphioxus and the evolution of anterior-posterior patterning in deuterostomes. Dev Biol 2002; 241:209-28. [PMID: 11784106 DOI: 10.1006/dbio.2001.0503] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In Xenopus, the canonical Wnt-signaling pathway acting through beta-catenin functions both in establishing the dorso-ventral axis and in patterning the anterior-posterior axis. This pathway also acts in patterning the animal-vegetal axis in sea urchins. However, because sea urchin development is typically indirect, and adult sea urchins have pentamerous symmetry and lack a longitudinal nerve cord, it has not been clear how the roles of the canonical Wnt-signaling pathway in axial patterning in sea urchins and vertebrates are evolutionarily related. The developmental expression patterns of Notch, brachyury, caudal, and eight Wnt genes have now been determined for the invertebrate chordate Amphioxus, which, like sea urchins, has an early embryo that gastrulates by invagination, but like vertebrates, has a later embryo with a dorsal hollow nerve cord that elongates posteriorly from a tail bud. Comparisons of Amphioxus with other deuterostomes suggest that patterning of the ancestral deuterostome embryo along its anterior-posterior axis during the late blastula and subsequent stages involved a posterior signaling center including Wnts, Notch, and transcription factors such as brachyury and caudal. In tunicate embryos, in which cell numbers are reduced and cell fates largely determined during cleavage stages, only vestiges of this signaling center are still apparent; these include localization of Wnt-5 mRNA to the posterior cytoplasm shortly after fertilization and localization of beta-catenin to vegetal nuclei during cleavage stages. Neither in tunicates nor in Amphioxus is there any evidence that the canonical Wnt-signaling pathway functions in establishment of the dorso-ventral axis. Thus, roles for Wnt-signaling in dorso-ventral patterning of embryos may be a vertebrate innovation that arose in connection with the evolution of yolky eggs and gastrulation by extensive involution.
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Affiliation(s)
- Linda Z Holland
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0202, USA.
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Cao Y, Zhao H, Grunz H. XCL-2 is a novel m-type calpain and disrupts morphogenetic movements during embryogenesis in Xenopus laevis. Dev Growth Differ 2001; 43:563-71. [PMID: 11576173 DOI: 10.1046/j.1440-169x.2001.00592.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
We identified a novel cDNA, XCL-2, encoding an m-type calpain, a calcium-dependent intracellular protease. This protein has all characteristic structures and active sites of canonical calpains. Zygotic transcription of the gene was first detected at stage 10. It is expressed exclusively in the ventral circumblastoporal collar and the mesoderm-free zone at the most anterior tip of neural fold in late gastrulae and neurulae. In later stages, expression is only found in cement gland and proctodeum. It is also expressed in a tissue-specific manner. In adult tissues, various levels of expression were detected in brain, eye, heart, intestine, kidney, lung, stomach and testis, but not in liver, muscle, nerve, ovary, skin and spleen. Overexpression of wild-type XCL-2 suggests that this gene is involved in gastrulation movement and convergent extension during gastrulation and neurulation. Overexpression of a dominant-negative mutant caused a phenotype morphologically similar to, but histologically different from, that caused by overexpression of wild-type XCL-2. The mutant phenotype can be rescued by injection of wild-type XCL-2. These data suggest that XCL-2 plays an important role in convergent extension movements during embryogenesis in Xenopus laevis.
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Affiliation(s)
- Y Cao
- Department of Zoophysiology, University of Essen, 45117 Essen, Germany
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17
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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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18
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Mathis L, Kulesa PM, Fraser SE. FGF receptor signalling is required to maintain neural progenitors during Hensen's node progression. Nat Cell Biol 2001; 3:559-66. [PMID: 11389440 DOI: 10.1038/35078535] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Previous analyses of labelled clones of cells within the developing nervous system of the mouse have indicated that descendants are initially dispersed rostrocaudally followed by more local proliferation, which is consistent with the progressing node's contributing descendants from a resident population of progenitor cells as it advances caudally. Here we electroporated an expression vector encoding green fluorescent protein into the chicken embryo near Hensen's node to test and confirm the pattern inferred in the mouse. This provides a model in which a proliferative stem zone is maintained in the node by a localized signal; those cells that are displaced out of the stem zone go on to contribute to the growing axis. To test whether fibroblast growth factor (FGF) signalling could be involved in the maintenance of the stem zone, we co-electroporated a dominant-negative FGF receptor with a lineage marker, and found that it markedly alters the elongation of the spinal cord primordium. The results indicate that FGF receptor signalling promotes the continuous development of the posterior nervous system by maintaining presumptive neural progenitors in the region near Hensen's node. This offers a potential explanation for the mixed findings on FGF in the growth and patterning of the embryonic axis.
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Affiliation(s)
- L Mathis
- Biological Imaging Center, Beckman Institute 139-74, California Institute of Technology, Pasadena, California 91125, USA
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19
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Abstract
For three-quarters of a century, developmental biologists have been asking how the nervous system is specified as distinct from the rest of the ectoderm during early development, and how it becomes subdivided initially into distinct regions such as forebrain, midbrain, hindbrain and spinal cord. The two events of 'neural induction' and 'early neural patterning' seem to be intertwined, and many models have been put forward to explain how these processes work at a molecular level. Here I consider early neural patterning and discuss the evidence for and against the two most popular models proposed for its explanation: the idea that multiple signalling centres (organizers) are responsible for inducing different regions of the nervous system, and a model first articulated by Nieuwkoop that invokes two steps (activation/transformation) necessary for neural patterning. As recent evidence from several systems challenges both models, I propose a modification of Nieuwkoop's model that most easily accommodates both classical and more recent data, and end by outlining some possible directions for future research.
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Affiliation(s)
- C D Stern
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK.
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20
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Abstract
Choroid plexus lipocalin 1 (Cpl1) has been isolated from the African clawed toad (Xenopus laevis) and the cane toad (Bufo marinus). Xcpl1 has been used as a marker for studying early neural development. Due to its retinoid binding properties and the fact that it causes dysmorphogenesis when overexpressed in the early embryo, the protein product is considered to be part of the retinoic acid signalling pathway. Later in development and during adulthood, the epithelial cell sheet of the choroid plexus which forms the blood-cerebrospinal fluid barrier expresses cpl1 as the predominant secretory protein. These data, the similarity of Cpl1 to prostaglandin D(2) synthase and its functional homology to transthyretin will be discussed.
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Affiliation(s)
- G Lepperdinger
- Institute of Molecular Biology, Austrian Academy of Sciences, Billrothstrasse 11, A-5020 Salzburg, Austria.
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21
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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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22
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Doi JY, Niigaki H, Sone K, Takabatake T, Takeshima K, Yasui K, Tosuji H, Tsukahara J, Sakai M. Distribution of dorsal-forming activity in precleavage embryos of the Japanese newt, Cynops pyrrhogaster: effects of deletion of vegetal cytoplasm, UV irradiation, and lithium treatment. Dev Biol 2000; 223:154-68. [PMID: 10864468 DOI: 10.1006/dbio.2000.9735] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Two types of axis-deficient embryos developed after deletion of the vegetal cytoplasm: wasp-shaped embryos and permanent-blastula-type embryos. In situ hybridization revealed that neither type of axis-deficient embryo expressed goosecoid or pax-6. brachyury was expressed in the constricted waist region of the wasp-shaped embryos but was not expressed in the permanent-blastula-type embryos. Further, we examined the effect of UV irradiation on Japanese newt embryos. Surprisingly, UV-irradiated Japanese newt eggs formed hyperdorsalized embryos. These embryos gastrulated in an irregular circular fashion with goosecoid expression in the circular equatorial region. At tailbud stage, these embryos formed a proboscis which is very reminiscent of that formed in hyperdorsalized Xenopus embryos. Transplantation of the marginal region of the UV-irradiated embryos revealed that the entire marginal zone had organizer activity. Thus we conclude that UV hyperdorsalizes Japanese newt embryos. Finally, lithium treatment of normal embryos at the 32-cell stage also resulted in hyperdorsalization. Lithium treatment of vegetally deleted embryos had two distinct results. Lithium treatment of permanent-blastula-type embryos did not result in the formation of dorsal axial structures, while the same treatment reinduced gastrulation and dorsal axis formation in the wasp-shaped embryos. Based on these results, we propose a model for early axis specification in Japanese newt embryos. The model presented here is fundamentally identical to the Xenopus model, with some important modifications. The vegetally located determinants required for dorsal development (dorsal determinants, DDs) are distributed over a wider region at fertilization in Japanese newt embryos than in Xenopus embryos. The marginal region of the Japanese newt embryo at the beginning of development overlaps with the field of the DDs. Gastrulation is very likely to be a dorsal marginal-specific property, while self-constriction is most probably a ventral marginal-specific property in Japanese newt embryos.
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Affiliation(s)
- J Y Doi
- Department of Chemistry and Bioscience, Kagoshima University, Kagoshima, 890-0065, Japan
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23
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Katsuyama Y, Saiga H. Retinoic acid affects patterning along the anterior-posterior axis of the ascidian embryo. Dev Growth Differ 1998; 40:413-22. [PMID: 9727355 DOI: 10.1046/j.1440-169x.1998.t01-2-00006.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Because retinoic acid (RA) is known to affect anterior posterior patterning in vertebrate embryos, it was questioned whether it shows similar effects in a more primitive chordate, the ascidian Halocynthia roretzi. Ascidian embryos treated with RA exhibited truncated phenotypes in a dose-dependent manner similar to the anterior truncations seen in vertebrate embryos. The most severely affected larvae possessed a round trunk without the papillae characteristic of the anterior terminal epidermis. Retinoic acid also altered the expression of HrHox-1 and Hroth in a dose-dependent manner. Expression of HrHox-1 increased, whereas expression of Hroth decreased with increasing levels of RA. In treated embryos, HrHox-1 was first expressed pan-ectodermally, then degraded in all but specific regions of the embryo. By contrast, initiation of Hroth expression was not affected, but epidermal expression was lost while expression in the neural tube narrowed toward the anterior in tail-bud embryos. These alterations in the expression of homeobox genes appear to correlate closely to the morphological defects elicited by RA treatment, suggesting broad conservation of developmental patterning mechanisms within the Phylum Chordata.
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Affiliation(s)
- Y Katsuyama
- Department of Biological Sciences, Graduate School of Science, Tokyo Metropolitan University, Hachiohji, Japan
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24
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Ecochard V, Cayrol C, Rey S, Foulquier F, Caillol D, Lemaire P, Duprat AM. A novel Xenopus mix-like gene milk involved in the control of the endomesodermal fates. Development 1998; 125:2577-85. [PMID: 9636073 DOI: 10.1242/dev.125.14.2577] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Here we describe a novel Xenopus homeobox gene, milk, related by sequence homology and expression pattern to the vegetally expressed Mix.1. As is the case with Mix.1, milk is an immediate early response gene to the mesoderm inducer activin. milk is expressed at the early gastrula stage in the vegetal cells, fated to form endoderm, and in the marginal zone fated to form mesoderm. During gastrulation, expression of milk becomes progressively reduced in the involuting mesodermal cells but is retained in the endoderm, suggesting that it may play a key role in the definition of the endo-mesodermal boundary in the embryo. Overexpression of milk in the marginal zone blocks mesodermal cell involution, represses the expression of several mesodermal genes such as Xbra, goosecoid, Xvent-1 or Xpo and increases the expression of the endodermal gene, endodermin. In the dorsal marginal zone, overexpression of milk leads to a severe late phenotype including the absence of axial structures. Ectopic expression of milk in the animal hemisphere or in ectodermal explants induces a strong expression of endodermin. Taken together, we propose that milk plays a role in the correct patterning of the embryo by repressing mesoderm formation and promoting endoderm identity.
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Affiliation(s)
- V Ecochard
- Centre de Biologie du Développement, UMR 5547 CNRS/Université Paul Sabatier, affiliée à l'INSERM, Bât. 4R3, France
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25
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Yamada T, Modak SP. Genetic evidence for posterior specification by convergent extension in the Xenopus embryo. Dev Growth Differ 1998; 40:125-32. [PMID: 9572355 DOI: 10.1046/j.1440-169x.1998.00002.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Genetic studies substantiate that mesodermal convergent extension expressed behind the anteroposterior borderline, in the form of a gradient with the posterior apex after gastrulation, regulates morphogenesis of the posterior zone at the dorsal and dorso-lateral levels which is in full agreement with the model of dorsalization-caudalization. In contrast, how anteroposterior specification of mesodermal tissues occurs at the ventral and latero-ventral levels is not yet understood.
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Affiliation(s)
- T Yamada
- Swiss Institute for Experimental Cancer Research, Epalinges
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26
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Kavka AI, Green JB. Tales of tails: Brachyury and the T-box genes. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1333:F73-84. [PMID: 9395282 DOI: 10.1016/s0304-419x(97)00016-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- A I Kavka
- Dana-Farber Cancer Institute, Boston, MA 02215, USA.
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27
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Epstein M, Pillemer G, Yelin R, Yisraeli JK, Fainsod A. Patterning of the embryo along the anterior-posterior axis: the role of the caudal genes. Development 1997; 124:3805-14. [PMID: 9367436 DOI: 10.1242/dev.124.19.3805] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Patterning along the anterior-posterior axis takes place during gastrulation and early neurulation. Homeobox genes like Otx-2 and members of the Hox family have been implicated in this process. The caudal genes in Drosophila and C. elegans have been shown to determine posterior fates. In vertebrates, the caudal genes begin their expression during gastrulation and they take up a posterior position. By injecting sense and antisense RNA of the Xenopus caudal gene Xcad-2, we have studied a number of regulatory interactions among homeobox genes along the anterior-posterior axis. Initially, the Xcad-2 and Otx-2 genes are mutually repressed and, by late gastrulation, they mark the posterior- or anterior-most domains of the embryo, respectively. During late gastrulation and neurulation, Xcad-2 plays an additional regulatory function in relation to the Hox genes. Hox genes normally expressed anteriorly are repressed by Xcad-2 overexpression while those normally expressed posteriorly exhibit more anterior expression. The results show that the caudal genes are part of a posterior determining network which during early gastrulation functions in the subdivision of the embryo into anterior head and trunk domains. Later in gastrulation and neurulation these genes play a role in the patterning of the trunk region.
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Affiliation(s)
- M Epstein
- Department of Cellular Biochemistry, Hebrew University-Hadassah Medical School, Jerusalem, Israel
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28
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Foley AC, Storey KG, Stern CD. The prechordal region lacks neural inducing ability, but can confer anterior character to more posterior neuroepithelium. Development 1997; 124:2983-96. [PMID: 9247340 DOI: 10.1242/dev.124.15.2983] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The avian equivalent of Spemann's organizer, Hensen's node, begins to lose its ability to induce a nervous system from area opaca epiblast cells at stage 4+, immediately after the full primitive streak stage. From this stage, the node is no longer able to induce regions of the nervous system anterior to the hindbrain. Stage 4+ is marked by the emergence from the node of a group of cells, the prechordal mesendoderm. Here we have investigated whether the prechordal region possesses the lost functions of the organizer, using quail-chick chimaeras to distinguish graft- and host-derived cells, together with several region-specific molecular markers. We find that the prechordal region does not have neural inducing ability, as it is unable to divert extraembryonic epiblast cells to a neural fate. However, it can confer more anterior character to prospective hindbrain cells of the host, making them acquire expression of the forebrain markers tailless and Otx-2. It can also rescue the expression of Krox-20 and Otx-2 from nervous system induced by an older (stage 5) node in extraembryonic epiblast. We show that these properties reflect a true change of fate of cells rather than recruitment from other regions. The competence of neuroectoderm to respond to anteriorizing signals declines by stages 7–9, but both posteriorizing signals and the ability of neuroectoderm to respond to them persist after this stage.
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Affiliation(s)
- A C Foley
- Department of Genetics and Development, College of Physicians and Surgeons of Columbia University, New York, NY 10032, USA
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29
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Taira M, Saint-Jeannet JP, Dawid IB. Role of the Xlim-1 and Xbra genes in anteroposterior patterning of neural tissue by the head and trunk organizer. Proc Natl Acad Sci U S A 1997; 94:895-900. [PMID: 9023353 PMCID: PMC19610 DOI: 10.1073/pnas.94.3.895] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Anteroposterior patterning of neural tissue is thought to be directed by the axial mesoderm which is functionally divided into head and trunk organizer. The LIM class homeobox gene Xlim-1 is expressed in the entire axial mesoderm, whereas the distinct transcription factor Xbra is expressed in the notochord but not in the prechordal mesoderm. mRNA injection experiments showed that Xenopus animal explants (caps) expressing an activated form of Xlim-1 (a LIM domain mutant named 3m) induce anterior neural markers whereas caps coexpressing Xlim-1/3m and Xbra induce posterior neural markers. These data indicate that, in terms of neural inducing ability, Xlim-1/3m-expressing caps correspond to the head organizer and Xlim-1/3m plus Xbra-coexpressing caps to the trunk organizer. Thus the expression domains of Xlim-1 and Xbra correlate with, and possibly define, the functional domains of the organizer. In animal caps Xlim-1/3m initiates expression of a neuralizing factor, chordin, whereas Xbra activates embryonic fibroblast growth factor (eFGF) expression, as reported previously; these factors could mediate the neural inducing and patterning effects that were observed. A dominant-negative FGF receptor (XFD) inhibits posteriorization by Xbra in a dose-dependent manner, supporting the suggestion that eFGF or a related factor has posteriorizing influence.
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Affiliation(s)
- M Taira
- Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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30
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The Patterning of Progenitor Tissues for the Cranial Region of the Mouse Embryo During Gastrulation and Early Organogenesis. ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s1566-3116(08)60037-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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31
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Mesoderm induction in amphibians and chick. J Biosci 1996. [DOI: 10.1007/bf02703094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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32
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von Bubnoff A, Schmidt JE, Kimelman D. The Xenopus laevis homeobox gene Xgbx-2 is an early marker of anteroposterior patterning in the ectoderm. Mech Dev 1996; 54:149-60. [PMID: 8652408 DOI: 10.1016/0925-4773(95)00468-8] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
In a search for homeobox genes expressed during early Xenopus development, we have isolated a gene which appears to be the Xenopus cognate of the mouse Gbx-2 gene. Expression of Xgbx-2 is first detectable by in situ hybridization at the midgastrula stage when it is predominantly expressed in the dorsolateral ectoderm, with a gap in expression at the dorsal midline. By the end of gastrulation and during neurulation, Xgbx-2 is expressed dorsolaterally in the neural ectoderm and laterally and ventrally in the epidermis with sharp anterior expression borders in both tissues. The anteriormost expression in the neural ectoderm persists throughout the early stages of development, and was mapped to the region of rhombomere 1, with an anterior expression border in the region of the midbrain-hindbrain boundary. Thus Xgbx-2 is expressed anterior to the Hox genes. Xgbx-2 expression is induced by retinoic acid (RA) in animal caps, and RA treatment of whole embryos expands and enhances Xgbx-2 expression in the ectoderm. We suggest a role for Xgbx-2 in establishing the midbrain-hindbrain boundary, which appears to separate early neurectodermal regions expressing genes that are positively and negatively regulated by RA.
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Affiliation(s)
- A von Bubnoff
- Department of Biochemistry, University of Washington, Seattle 98195-7350, USA
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33
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35
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Yamada T. Anteroposterior specification in amphibian embryogenesis: The regulative roles of positive and negative controls of mitogenesis. Dev Growth Differ 1995. [DOI: 10.1046/j.1440-169x.1995.t01-3-00002.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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36
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Abstract
Lim1 is a homeobox gene expressed in the organizer region of mouse embryos. To investigate the role of Lim1 during embryogenesis, a targeted deletion of the Lim1 gene was generated in embryonic stem cells. Embryos homozygous for the null allele lacked anterior head structures but the remaining body axis developed normally. A partial secondary axis developed anteriorly in some mutant embryos. Lim1 is thus an essential regulator of the vertebrate head organizer.
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Affiliation(s)
- W Shawlot
- Department of Molecular Genetics, University of Texas M.D. Anderson Cancer Center, Houston 77030, USA
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37
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Barro O, Vriz S, Joly JS, Joly C, Condamine H, Boulekbache H. Widespread expression of the eve1 gene in zebrafish embryos affects the anterior-posterior axis pattern. DEVELOPMENTAL GENETICS 1995; 17:117-28. [PMID: 7586753 DOI: 10.1002/dvg.1020170204] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The zygotic expression of the eve1 gene is restricted to the ventral and lateral cells of the marginal zone. At later stages, the mRNAs are localized in the most posterior part of the extending tail tip. An eve1 clone (pcZf14), containing a poly-A tail, has been isolated. In order to address eve1 gene function, pcZf14 transcript injections into zebrafish embryos have been performed. The injection into uncleaved eggs of a synthetic eve1 mRNA (12 pg), which encodes a protein of approximately 28 kd, produces embryos with anterior-posterior (A-P) axis defects and the formation of additional axial structures. The first category of 24 h phenotypes (87%) mainly displays a gradual decrease in anterior structures. This is comparable to previous phenotypes observed following Xhox3 messenger injection either in Xenopus or in zebrafish that have been classified according to the index of axis deficiency (zf-IAD). These phenotypes result in anomalies of the development of the neural keel, from microphthalmia to acephaly. The second category (13%) corresponds to the phenotypes described above together with truncal or caudal supernumerary structures. Additional truncal structures are the most prominent of these duplicated phenotypes, displaying a "zipper" shape of axial structures including neural keels and notochords. Caudal duplication presents no evident axis supernumerary structures. The observation of these phenotypes suggests an important role for the eve1 gene in mesodermal cell specification and in the development of the posterior region, and more particularly of the most posterior tail tip where endogenous eve1 messengers are found.
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Affiliation(s)
- O Barro
- Laboratoire de Biologie du Développement, Université Paris, France
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