Exogenous hyalin and sea urchin gastrulation. Part III: Biological activity of hyalin isolated fromLytechinus pictusembryos

Abstract

SummaryHyalin is a large glycoprotein, consisting of the hyalin repeat domain and non-repeated regions, and is the major component of the hyaline layer in the early sea urchin embryo ofStrongylocentrotus purpuratus. The hyalin repeat domain has been identified in proteins from organisms as diverse as bacteria, sea urchins, worms, flies, mice and humans. While the specific function of hyalin and the hyalin repeat domain is incompletely understood, many studies suggest that it has a functional role in adhesive interactions. In part I of this series, we showed that hyalin isolated from the sea urchinS. purpuratusblocked archenteron elongation and attachment to the blastocoel roof occurring during gastrulation inS. purpuratusembryos, (Raziniaet al., 2007). The cellular interactions that occur in the sea urchin, recognized by the U.S. National Institutes of Health as a model system, may provide insights into adhesive interactions that occur in human health and disease. In part II of this series, we showed thatS. purpuratushyalin heterospecifically blocked archenteron–ectoderm interaction inLytechinus pictusembryos (Alvarezet al., 2007). In the current study, we have isolated hyalin from the sea urchinL. pictusand demonstrated thatL. pictushyalin homospecifically blocks archenteron–ectoderm interaction, suggesting a general role for this glycoprotein in mediating a specific set of adhesive interactions. We also found one major difference in hyalin activity in the two sea urchin species involving hyalin influence on gastrulation invagination.