Exogenous hyalin and sea urchin gastrulation, Part II: hyalin, an interspecies cell adhesion molecule

Abstract

SummaryThe 330 kDa fibrillar glycoprotein hyalin is a well known component of the sea urchin embryo extracellular hyaline layer. Only recently, the main component of hyalin, the hyalin repeat domain, has been identified in organisms as widely divergent as bacteria and humans using the GenBank database and therefore its possible function has garnered a great deal of interest. In the sea urchin, hyalin serves as an adhesive substrate in the developing embryo and we have recently shown that exogenously added purified hyalin from Strongylocentrotus purpuratus embryos blocks a model cellular interaction in these embryos, archenteron elongation/attachment to the blastocoel roof. It is important to demonstrate the generality of this result by observing if hyalin from one species of sea urchin blocks archenteron elongation/attachment in another species. Here we show in three repeated experiments, with 30 replicate samples for each condition, that the same concentration of S. purpuratus hyalin (57 μg/ml) that blocked the interaction in living S. purpuratus embryos blocked the same interaction in living Lytechinus pictus embryos. These results correspond with the known crossreactivity of antibody against S. purpuratus hyalin with L. pictus hyalin. We propose that hyalinhyalin receptor binding may mediate this adhesive interaction. The use of a microplate assay that allows precise quantification of developmental effects should help facilitate identification of the function of hyalin in organisms as divergent as bacteria and humans.

Exogenous hyalin and sea urchin gastrulation. Part IV: a direct adhesion assay – progress in identifying hyalin's active sites

“…Gametes of Lytechinus pictus ( L. pictus ) sea urchins were prepared as described above. Hyalin from S. purpuratus is biologically active with L. pictus (Alvarez et al ., 2008) and antibody to hyalin from one species cross reacts with hyalin from other species (Vater & Jackson, 1990). Eggs collected from individual females were washed separately two times with 100 ml of ASW, pH 8.0.…”

“…This model is the best organism for studying hyalin function because of the quantity of embryos obtainable and because of the availability and transparency of the sea urchin embryo. Hyalin has been implicated in controlling general adhesive interactions in the sea urchin embryo (Kondo, 1973; Wessel et al ., 1998) and our laboratories provided evidence that hyalin is a cell adhesion molecule involved in mediating specific cellular interactions during the process of archenteron elongation and attachment to the blastocoel roof (Razinia et al ., 2007; Alvarez et al ., 2008; Carroll et al ., 2008; Contreras et al ., 2008), cellular interactions that have interested investigators for over a century (Herbst, 1900).…”

“…In past studies we used a quantitative microplate assay for assessing the effects of exogenous hyalin and anti-hyalin antibody on the specific cellular interactions in whole, living embryos (Razinia et al ., 2007; Alvarez et al ., 2008; Carroll et al ., 2008; Contreras et al ., 2008). This assay was indirect because it did not directly measure the effects of hyalin on the specific interactions and did not even assure that hyalin entered the embryo to probe the interactions being studied.…”

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

“…We have used two of the assays in identifying a putative role for glucose/mannose groups in the specific adhesive interaction studied here (Latham et al, 1999; Khurrum et al, 2004; Coyle-Thompson & Oppenheimer, 2005; Sajadi et al, 2007) and are currently examining the relationship between these past findings with respect to sugar involvement, and the hyalin results reported here, in Razinia et al (2007), and in Alvarez et 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 that S. purpuratus hyalin heterospecifically blocked archenteron-ectoderm interaction in Lytechinus pictus embryos (Alvarez et al, 2007). In the current study, we have isolated hyalin from the sea urchin L. pictus and demonstrated that L. pictus hyalin homospecifically blocks archenteron-ectoderm interaction, suggesting a general role for this glycoprotein in mediating a specific set of adhesive interactions.…”