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  • 1
    Publikationsdatum: 2014-09-13
    Beschreibung: The origin of chordates has been debated for more than a century, with one key issue being the emergence of the notochord. In vertebrates, the notochord develops by convergence and extension of the chordamesoderm, a population of midline cells of unique molecular identity. We identify a population of mesodermal cells in a developing invertebrate, the marine annelid Platynereis dumerilii, that converges and extends toward the midline and expresses a notochord-specific combination of genes. These cells differentiate into a longitudinal muscle, the axochord, that is positioned between central nervous system and axial blood vessel and secretes a strong collagenous extracellular matrix. Ancestral state reconstruction suggests that contractile mesodermal midline cells existed in bilaterian ancestors. We propose that these cells, via vacuolization and stiffening, gave rise to the chordate notochord.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lauri, Antonella -- Brunet, Thibaut -- Handberg-Thorsager, Mette -- Fischer, Antje H L -- Simakov, Oleg -- Steinmetz, Patrick R H -- Tomer, Raju -- Keller, Philipp J -- Arendt, Detlev -- Howard Hughes Medical Institute/ -- New York, N.Y. -- Science. 2014 Sep 12;345(6202):1365-8. doi: 10.1126/science.1253396.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Developmental Biology Unit, European Molecular Biology Laboratory (EMBL), D-69117 Heidelberg. ; Developmental Biology Unit, European Molecular Biology Laboratory (EMBL), D-69117 Heidelberg. Janelia Farm Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA. ; Janelia Farm Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA. ; Developmental Biology Unit, European Molecular Biology Laboratory (EMBL), D-69117 Heidelberg. Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany. detlev.arendt@embl.de.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25214631" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Abdominal Muscles/cytology/embryology ; Animals ; *Biological Evolution ; Gene Expression Regulation, Developmental ; Mesoderm/cytology/*embryology ; Notochord/cytology/*embryology ; Phylogeny ; Polychaeta/*classification/*embryology/genetics
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2018-02-22
    Beschreibung: Retinoic acid (RA) is an important intercellular signaling molecule in vertebrate development, with a well-established role in the regulation of hox genes during hindbrain patterning and in neurogenesis. However, the evolutionary origin of the RA signaling pathway remains elusive. To elucidate the evolution of the RA signaling system, we characterized RA metabolism and signaling in the marine annelid Platynereis dumerilii , a powerful model for evolution, development, and neurobiology. Binding assays and crystal structure analyses show that the annelid retinoic acid receptor (RAR) binds RA and activates transcription just as vertebrate RARs, yet with a different ligand-binding pocket and lower binding affinity, suggesting a permissive rather than instructive role of RA signaling. RAR knockdown and RA treatment of swimming annelid larvae further reveal that the RA signal is locally received in the medial neuroectoderm, where it controls neurogenesis and axon outgrowth, whereas the spatial colinear hox gene expression in the neuroectoderm remains unaffected. These findings suggest that one early role of the new RAR in bilaterian evolution was to control the spatially restricted onset of motor and interneuron differentiation in the developing ventral nerve cord and to indicate that the regulation of hox -controlled anterior-posterior patterning arose only at the base of the chordates, concomitant with a high-affinity RAR needed for the interpretation of a complex RA gradient.
    Digitale ISSN: 2375-2548
    Thema: Allgemeine Naturwissenschaft
    Standort Signatur Erwartet Verfügbarkeit
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