Mutational Analysis of Tunicate Development

Summary

Principal Investigator: William Smith
Abstract: DESCRIPTION (provided by applicant): We have discovered a requirement for a novel connexin gene (frm-cx) in specification of the anterior neural plate in the invertebrate chordate Ciona. (The connexin proteins make gap junctions.) In embryos from the frimousse (frm) mutant line, the anterior neural plate is transfated to epidermis. The anterior neural plate of Ciona gives rise both to brain and to two other non-neural tissues, the mouth and adhesive palp. The initial FGF-dependent induction of the anterior neural plate appears to be normal in the mutant, as judged by expression of early response genes. However, the expression of these genes is quickly lost, and the anterior neural plate derivatives become incorporated into the epidermis and express epidermal genes. We hypothesize that the frm-cx gene product is required for maintaining neural plate identity by allowing for intercellular communication between the newly induced anterior neural plate cells. We also hypothesize that that frm-cx expression is an early response to anterior neural induction. Experiments in the first two Specific Aims of this proposal will test these hypotheses. Because some connexins have biological activities distinct from their channel forming role, in the first Specific Aim we will investigate the necessity of gap junction communication within the newly-induced neural plate. In further experiments to determine whether the anterior neural plate makes a distinct communication compartment within the embryo, we will assess the cellular connectivity of cells using a photoactivatable gap junction-permeable fluorescent dye. Additional experiments will investigate whether over expression of frm-cx is sufficient to cause expansion of the neural plate. In the second Specific Aim we will place frm-cx within the regulatory context of anterior neural induction by determining its epigenetic relationship to other known anterior neural transcription factors. To test for the necessity of these factors we will isolate a minimal regulatory element from the frm-cx gene. In this element we will identify and then mutate potential transcription factor binding sites. The final Specific Aim will characterize a new mutant line, bugeye (bug) that disrupts the same set of cells affected in the frm mutant. In the bug mutant neural tube folding and closure (neurulation), but not specification, are disrupted. Specific experiments will fully characterize the mechanical defects in neurulation in bug mutants by confocal imaging and 3-dimensional modeling. The final goal of this Specific Aim is to postionally clone the bug mutant using established methods. PUBLIC HEALTH RELEVANCE: The formation of the central nervous system is a critical component of human development. This proposal will examine the cellular and molecular mechanisms of early events in brain development using an animal that models human brain development.
Funding Period: 2000-04-01 - 2016-01-31
more information: NIH RePORT

Top Publications

  1. pmc Ascidian notochord morphogenesis
    Di Jiang
    Sars International Centre for Marine Molecular Biology, Bergen, Norway
    Dev Dyn 236:1748-57. 2007
  2. pmc Ciona genetics
    Michael T Veeman
    Department of Molecular, Cell and Developmental Biology, University of California Santa Barbara, Santa Barbara, CA, USA
    Methods Mol Biol 770:401-22. 2011
  3. pmc doublesex/mab3 related-1 (dmrt1) is essential for development of anterior neural plate derivatives in Ciona
    Jason Tresser
    Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, CA 93106, USA
    Development 137:2197-203. 2010
  4. ncbi The ascidian mouth opening is derived from the anterior neuropore: reassessing the mouth/neural tube relationship in chordate evolution
    Michael T Veeman
    Department of Molecular, University of California Santa Barbara, Santa Barbara, CA 93106, USA
    Dev Biol 344:138-49. 2010
  5. pmc Key steps in the morphogenesis of a cranial placode in an invertebrate chordate, the tunicate Ciona savignyi
    Matthew J Kourakis
    University of California, Santa Barbara, Department of Molecular, Cell and Developmental Biology, USA
    Dev Biol 340:134-44. 2010
  6. pmc Tube formation by complex cellular processes in Ciona intestinalis notochord
    Bo Dong
    Sars International Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgt 55, N 5008 Bergen, Norway
    Dev Biol 330:237-49. 2009
  7. pmc Brachyury null mutant-induced defects in juvenile ascidian endodermal organs
    Shota Chiba
    Department of Molecular, Cell and Developmental Biology, University of California Santa Barbara, Santa Barbara, CA 93106, USA
    Development 136:35-9. 2009
  8. pmc Ascidians and the plasticity of the chordate developmental program
    Patrick Lemaire
    Institut de Biologie du Developpement de Marseille Luminy IBDML, UMR6216, CNRS Université de la Méditerranée, Case 907, Campus de Luminy, F 13288 Marseille Cedex 9, France
    Curr Biol 18:R620-31. 2008
  9. pmc Inverse correlation of population similarity and introduction date for invasive ascidians
    Nathan Silva
    Interdepartmental Graduate Program in Marine Science, University of California Santa Barbara, Santa Barbara, California, United States of America
    PLoS ONE 3:e2552. 2008
  10. pmc The C. savignyi genetic map and its integration with the reference sequence facilitates insights into chordate genome evolution
    Matthew M Hill
    Department of Pathology, SUMC, Stanford, CA 94305 5324, USA
    Genome Res 18:1369-79. 2008

Detail Information

Publications13

  1. pmc Ascidian notochord morphogenesis
    Di Jiang
    Sars International Centre for Marine Molecular Biology, Bergen, Norway
    Dev Dyn 236:1748-57. 2007
    ..Modern analysis of ascidian notochord morphogenesis promises to contribute to our understanding of these fundamental biological processes...
  2. pmc Ciona genetics
    Michael T Veeman
    Department of Molecular, Cell and Developmental Biology, University of California Santa Barbara, Santa Barbara, CA, USA
    Methods Mol Biol 770:401-22. 2011
    ....
  3. pmc doublesex/mab3 related-1 (dmrt1) is essential for development of anterior neural plate derivatives in Ciona
    Jason Tresser
    Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, CA 93106, USA
    Development 137:2197-203. 2010
    ..We speculate that the variability and late onset in the phenotype may be due to partially overlapping activities of other gene products...
  4. ncbi The ascidian mouth opening is derived from the anterior neuropore: reassessing the mouth/neural tube relationship in chordate evolution
    Michael T Veeman
    Department of Molecular, University of California Santa Barbara, Santa Barbara, CA 93106, USA
    Dev Biol 344:138-49. 2010
    ..This close association between the mouth primordium and the anterior neural tube in both ascidians and amphibians suggests that the evolution of these two structures may be more closely linked than previously appreciated...
  5. pmc Key steps in the morphogenesis of a cranial placode in an invertebrate chordate, the tunicate Ciona savignyi
    Matthew J Kourakis
    University of California, Santa Barbara, Department of Molecular, Cell and Developmental Biology, USA
    Dev Biol 340:134-44. 2010
    ....
  6. pmc Tube formation by complex cellular processes in Ciona intestinalis notochord
    Bo Dong
    Sars International Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgt 55, N 5008 Bergen, Norway
    Dev Biol 330:237-49. 2009
    ..Ciona notochord tube formation utilized an assortment of common and fundamental cellular processes including cell shape change, apical membrane biogenesis, cell/cell adhesion remodeling, dynamic cell crawling, and lumen matrix secretion...
  7. pmc Brachyury null mutant-induced defects in juvenile ascidian endodermal organs
    Shota Chiba
    Department of Molecular, Cell and Developmental Biology, University of California Santa Barbara, Santa Barbara, CA 93106, USA
    Development 136:35-9. 2009
    ..Some cells misdirected from the notochord lineage were found to be incorporated into definitive endodermal structures, such as stomach and intestine...
  8. pmc Ascidians and the plasticity of the chordate developmental program
    Patrick Lemaire
    Institut de Biologie du Developpement de Marseille Luminy IBDML, UMR6216, CNRS Université de la Méditerranée, Case 907, Campus de Luminy, F 13288 Marseille Cedex 9, France
    Curr Biol 18:R620-31. 2008
    ..Further, we propose that the comparative analysis of the architecture of ascidian and vertebrate gene regulatory networks may provide critical insight into the origin of the chordate body plan...
  9. pmc Inverse correlation of population similarity and introduction date for invasive ascidians
    Nathan Silva
    Interdepartmental Graduate Program in Marine Science, University of California Santa Barbara, Santa Barbara, California, United States of America
    PLoS ONE 3:e2552. 2008
    ..These findings show exceptions to the assumptions that invasive species start with a low level of genetic polymorphism that increases over time and that closely related species have similar levels of genetic polymorphism...
  10. pmc The C. savignyi genetic map and its integration with the reference sequence facilitates insights into chordate genome evolution
    Matthew M Hill
    Department of Pathology, SUMC, Stanford, CA 94305 5324, USA
    Genome Res 18:1369-79. 2008
    ..These results, when considered in light of the neutral theory, suggest fundamentally different modes of evolution of animal species with large versus small population sizes...
  11. pmc Chongmague reveals an essential role for laminin-mediated boundary formation in chordate convergence and extension movements
    Michael T Veeman
    Department of Molecular, Cell and Developmental Biology, University of California Santa Barbara, Santa Barbara CA, 93106, USA
    Development 135:33-41. 2008
    ..These mechanisms therefore initially act in parallel, but we also find that PCP signaling has an important later role in maintaining the perinotochordal/intranotochordal polarity of Cs-lamalpha3/4/5 localization...
  12. pmc A conserved role for FGF signaling in chordate otic/atrial placode formation
    Matthew J Kourakis
    Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA 93106, USA
    Dev Biol 312:245-57. 2007
    ..Our data suggest interactions required for formation of the atrial siphon and highlight the role of atrial ectoderm during gill slit morphogenesis...
  13. pmc A transiently expressed connexin is essential for anterior neural plate development in Ciona intestinalis
    Christopher Hackley
    Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, CA 93106, USA
    Development 140:147-55. 2013
    ..The requirement for cx-11 for anterior neural fate points to a crucial role for intercellular communication via gap junctions, probably through mediation of Ca(2+) transients, in Ciona intestinalis neural induction...