title: An ECM-bound, PDGF-like growth factor and a TGF-alpha-like growth factor are required for gastrulation and spiculogenesis in the Lytechinus embryo.
abstract: Growth factors and the extracellular matrix have been shown to fulfill vital developmental roles in many embryonic systems. Our hypothesis is that a developmental role played by the extracellular matrix in sea urchins may be the binding of a PDGF-like growth factor to promote signaling activity. We report here that anti-human PDGF-B antibodies and anti-human TGF-alpha antibodies immunoprecipitated specific proteins isolated from Lytechinus embryos. Addition of these antibodies to Lytechinus embryos inhibited gastrulation and spiculogenesis. The embryos are sensitive to the antibodies from the four-cell through the hatching blastula stages, which suggests that the TGF-alpha-like and PDGF-like ligands are required for the early differentiation of the gut and spicules. We present evidence that the PDGF-like growth factor depends on the extracellular matrix for signaling activity. Synthetic peptides representing the heparan sulfate proteoglycan binding sequence on human PDGF-B were added to Lytechinus embryo cultures to compete for binding sites with the endogenous PDGF-like growth factor. The experimental peptide inhibited gastrulation and caused radially arranged multiple spicules to form. Development was unaffected by a control peptide. These studies support our hypothesis and suggest that TGF-alpha-like and PDGF-like growth factors induce signaling events required for sea urchin gastrulation and spiculogenesis and suggest that an extracellular matrix-associated PDGF-like growth factor is involved in differentiation along the oral-aboral axis.
authors.affiliation: Department of Biology, University of Houston, Texas 77204-5513, USA.
authors.forename: V
authors.initials: V
authors.lastname: Govindarajan
authors.forename: R K
authors.initials: RK
authors.lastname: Ramachandran
authors.forename: J M
authors.initials: JM
authors.lastname: George
authors.forename: D C
authors.initials: DC
authors.lastname: Shakes
authors.forename: C R
authors.initials: CR
authors.lastname: Tomlinson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D016326:Extracellular Matrix Proteins / Q000502:physiology*; D005775:Gastrula / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D010982:Platelet-Derived Growth Factor / Q000502:physiology*; D012617:Sea Urchins / Q000196:embryology*; D015398:Signal Transduction; D016211:Transforming Growth Factor alpha / Q000502:physiology*
chemical_list: D016326:Extracellular Matrix Proteins; D010982:Platelet-Derived Growth Factor; D016211:Transforming Growth Factor alpha