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 of Strongylocentrotus 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 urchin S. purpuratus blocked archenteron elongation and attachment to the blastocoel roof occurring during gastrulation in S. purpuratus embryos, (Razinia 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 archenteronectoderm 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.

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

“…We showed that hyalin is localized on both the archenteron and blastocoel roof (Carroll et al ., 2008). We showed that hyalin and anti-hyalin antibody block the cellular interaction using the microplate assay (Razinia et al ., 2007; Alvarez et al ., 2008; Carroll et al ., 2008; Contreras et al ., 2008) and finally here, using exogenous hyalin, in the direct pieces assay. We propose that exogenously added hyalin binds to the hyalin on the two pieces of the cellular interaction (hyalin is known to selfassociate) and in this way blocks adhesion.…”

“…The pieces assay results indicate that untreated hyalin blocks the adhesion of the archenteron and blastocoel roof, that was previously only suggested using the microplate assay (Razinia et al ., 2007; Alvarez et al ., 2008; Contreras et al ., 2008). In addition, using both the pieces assay and the microplate assay, we show that periodate-treated hyalin did not block the adhesive interaction, while untreated hyalin did.…”

“…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.…”

Glyconectin Cell Adhesion Epitope, β-d-GlcpNAc3S-(1→3)-α-l-Fucp, Is Involved in Blastulation of Lytechinus pictus Sea Urchin Embryos

“…Majority of reports on cell adhesion in sea urchin embryos were focused on gastrulation and less on blastulation. Several types of aggregation factors, some of which have been isolated and partially characterized [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ], as well as more defined proteins such as desmosome cadherins [ 28 , 29 , 30 ], fibronectin [ 23 , 31 , 32 ], laminin [ 32 , 33 ], collagen type I, III and IV [ 34 , 35 , 36 , 37 ], integrin [ 38 ], lectins [ 39 ] including Pi-nectin [ 11 , 38 ] and echinonectin [ 12 , 40 , 41 , 42 , 43 ], hyalin [ 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ], proteoglycans [ 40 , 52 , 53 , 54 , 55 , 56 ], and glyconectin type of glycans [ 15 , 16 ], were shown to promote cell–cell adhesion and cell–extracellular matrix adhesion that were implicated in the maintenance of sea urchin embryonal shape and morphogenesis.…”