Thrombospondin-4 is expressed by early osteogenic tissues in the chick embryo

Authors

  • Richard P. Tucker,

    Corresponding author
    1. Department of Cell Biology and Human Anatomy, School of Medicine, University of California, Davis, California 95616
    • Department of Cell Biology and Human Anatomy, School of Medicine, University of California, Davis CA 95616
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  • Josephine C. Adams,

    1. Vascular Research Division, Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115
    Current affiliation:
    1. MRC Laboratory for Molecular Cell Biology, Department of Biology, University College, London, Gower St., London WC1E 6BT, UK
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  • Jack Lawler

    1. Vascular Research Division, Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115
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Abstract

The thrombospondins are a family of related glycoproteins found in the embryonic extracellular matrix. To date, five members of this family have been identified. Thrombospondin-1 and thrombospondin-2 have similar primary structure, but are expressed in different tissues at different times during development. Thrombospondins-3, -4, and cartilage oligomeric protein belong to a second thrombospondin subgroup in which the carboxyl-half of each molecule is most similar to thrombospondin-1 and -2. Here, we report the cloning and sequencing of a novel probe to avian thrombospondin-4. We have used this probe to determine the origins of thrombospondin-4 in the chick embryo by in situ hybridization. Thrombospondin-4 transcripts first appear in the mesenchyme surrounding bone anlage coinciding with the initial stages of osteogenesis. The expression in osteogenic tissues is transient: thrombospondin-4 mRNAs are not seen in the osteoblasts of bone collars in developing long bones. This pattern is distinct from avian thrombospondin-2, which is expressed in perichondrium and embryonic fibrous connective tissues. Our observations indicate that connective tissues are the principal site of thrombospondin-4 expression in the chick. The diverse origins of different thrombospondin gene family members imply distinctive roles for these proteins related to the growth and differentiation of cartilage, tendons, and bone. ©1995 Wiley-Liss, Inc.

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