Involvement of l(–)-rhamnose in sea urchin gastrulation. Part II: α-l-Rhamnosidase

Abstract

The sea urchin embryo is recognized as a model system to reveal developmental mechanisms involved in human health and disease. In Part I of this series, six carbohydrates were tested for their effects on gastrulation in embryos of the sea urchin Lytechinus pictus. Only l-rhamnose caused dramatic increases in the numbers of unattached archenterons and exogastrulated archenterons in living, swimming embryos. It was found that at 30 h post-fertilization the l-rhamnose had an unusual inverse dose-dependent effect, with low concentrations (1-3 mM) interfering with development and higher concentrations (30 mM) having little to no effect on normal development. In this study, embryos were examined for inhibition of archenteron development after treatment with α-l-rhamnosidase, an endoglycosidase that removes terminal l-rhamnose sugars from glycans. It was observed that the enzyme had profound effects on gastrulation, an effect that could be suppressed by addition of l-rhamnose as a competitive inhibitor. The involvement of l-rhamnose-containing glycans in sea urchin gastrulation was unexpected, since there are no characterized biosynthetic pathways for rhamnose utilization in animals. It is possible there exists a novel l-rhamnose-containing glycan in sea urchins, or that the enzyme and sugar interfere with the function of rhamnose-binding lectins, which are components of the innate immune system in many vertebrate and invertebrate species.

Terminal alpha-d-mannosides are critical during sea urchin gastrulation

“…Previously, this laboratory has studied several glycan effects during sea urchin gastrulation using similar assays (Latham et al , 1998, 1999; Khurrum et al , 2004; Coyle-Thompson & Oppenheimer 2005; Razinia et al 2007; Singh et al , 2014; Liang et al , 2015). In the present study α-mannosidase enzyme inhibited proper organization and attachment of the Lytechinus pictus archenteron suggesting the presence of one or all types of α1–2-, α1–3-, or α1–6-linkages.…”

‘Biogeneric’ developmental processes: drivers of major transitions in animal evolution

“…Galectins, endogenous carbohydrate-binding proteins present in most metazoan phyla [68] and some multicellular fungi (mushrooms) [69], but in neither unicellular holozoans nor in yeast, may have been involved in the origination of the triploblastic body plan. Interference with galectins leads to the loss of the primitive streak in the early-stage chicken embryo [70], and exogenous administration or degradation of the sugar ligand for a putative endogenous sea urchin lectin dramatically perturbs gastrulation in that organism [71]. Like multilayering, lumen formation and body elongation, triploblasty may thus have arisen ( perhaps more than once) by the mobilization of physical organizational effects by a small number of pre-existing gene products (and perhaps a few novel ones), acting in new contexts.…”

Covid-19 Pandemic, Glycobiology, Glycan Shields, Vaccine Strategies, Heparin Sulfate: A Mini Review

“…This laboratory has studied the role of carbohydrates in embryonic development and cancer for a half century [1][2][3][4][5][6][7][8].…”

“…The author of this current work, Steve Oppenheimer, has been recognized by election as Fellow of the American Association for the Advancement of Science (AAAS) primarily for his work in the field of glycobiology. Studies beginning at Johns Hopkins [1] have identified metabolic pathways and specific glycans involved in cellular interactions in the developing sea urchin embryo model [2][3][4][5][6][7] and in cancer cells [1]. A heavily downloaded review was published by this group that covered the fundamentals of glycobiology [8].…”