Involvement of L(-)rhamnose in sea urchin gastrulation : a live embryo assay

The sea urchin embryo is a National Institutes of Health model system that has provided major developments later found of importance in human health and disease. To obtain initial clues to identify glycans that mediate cellular interactions, Lytechinus pictus sea urchin embryos were incubated at 24 and 30 hrs post-fertilization with 0.0009M - 0.03M alpha cyclodextrin, melibiose, L(-) rhamnose, trehalose, D(+) xylose and L(-) xylose in lower calcium artificial sea water (pH 8.0, 15oC) that speeds entry of molecules into the interior of the embryos. While alpha cyclodextrin killed the embryos, and L (-) xylose had small effects at one concentration, L (-) rhamnose statistically caused increased numbers of unattached archenterons and exogastrulated embryos at low glycan concentrations after 18-24 hrs incubation with the sugar. The results were statistically significant compared to control embryos in the absence of sugar (p<0.05). The other sugars melibiose, trehalose, D (+) xylose had no statistically significant effects whatsoever at any concentration. A total of 39,369 embryos were examined in this study. Other studies have identified L (-) rhamnose and L (-) rhamnose- binding receptors in cellular interactions. This is the first demonstration of a likely role for L (-) rhamnose in cellular interactions using a live embryo assay in the NIH designated model sea urchin embryo system.