Posterior extension of the chick nephric (Wolffian) duct: The role of fibronectin and NCAM polysialic acid

Authors

  • Ruth Bellairs,

    1. Department of Anatomy and Development Biology, University College London, London WC1E 6BT, U. K.
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  • Pamela Lear,

    1. Department of Anatomy and Development Biology, University College London, London WC1E 6BT, U. K.
    Current affiliation:
    1. Pamela Lear is now at Department of Human Anatomy, Oxford University, OX1 3QX U. K.
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  • Kenneth M. Yamada,

    1. Laboratory of Developmental Biology, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland 20892–4370
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  • Urs Rutishauser,

    1. Department of Genetics, Case Western Reserve University, Cleveland, Ohio 44106–4955
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  • James W. Lash

    Corresponding author
    1. Department of Cell and Developmental Biology, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104–6058
    • Department of Cell and Developmental Biology, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6058
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Abstract

The nephric duct of the chick embryo starts to form at about stage 10 of Hamburger and Hamilton ([1951] J. Morphol. 88:49–92) and extends posteriorly, fusing with the cloaca at about the end of the third day of incubation (HH stage 17). Evidence from the literature suggests that the extension involves active migration of the posterior tip. This investigation concerned some molecules that might control this migration: fibronectin, vitronectin, the β1 integrin receptor, and NCAM polysialic acid. The concentration of fibronectin in the extracellular matrix was found by immunocytochemistry to be negligible at the posterior end of the duct; treatment of the living embryo with GRGDS failed to halt further extension of the duct; SEM examination of embryos treated with the synthetic peptides of fibronectin GRGDS, GRDGS, SDGR, and GRGES, or with vitronectin, revealed negligible morphological effects on the duct. It is concluded that there is yet no evidence that fibronectin is an important factor in duct migration. NCAM polysialic acid had a similar distribution to fibronectin, but treatment of the living embryo with Endo-N caused cessation of extension of the duct. Endo-N is an enzyme that specifically degrades PSA without affecting the NCAM polypeptide itself. It is suggested therefore that PSA may play an important role in duct extension. The synthetic peptides of fibronectin each produced distinctive patterns of blebbing on the surfaces of cells in trunk mesoderm, but the duct cells were unaffected. GRGES and SDGR caused blebbing on cells in the somites and the anterior segmental plate, though not on cells in the posterior segmental plate. This suggests that integrin receptors change in the anterior segmental plate as the mesoderm forms somites from somitomeres. © 1995 Wiley-Liss, Inc.

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