An ECM-Bound, PDGF-like Growth Factor and a TGF-α-like Growth Factor Are Required for Gastrulation and Spiculogenesis in theLytechinusEmbryo

• Published in: Developmental biology 1995-12, Vol.172 (2), p.541-551
• Main Authors: Govindarajan, Venkatesh, Ramachandran, Ravi K., George, Jenny M., Shakes, Diane C., Tomlinson, Craig R.
• Format: Article
• Language: English
• ISSN: 0012-1606; 1095-564X
• DOI: 10.1006/dbio.1995.8059

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-α antibodies immunoprecipitated specific proteins isolated fromLytechinusembryos. Addition of these antibodies toLytechinusembryos 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-α-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 toLytechinusembryo 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-α-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.