Synthesis of glycoconjugates during the development of mouse embryos in vitro

Abstract

Mouse embryos, culturedin vitro through the early stages of organogenesis, were labeled in the presence of [3H]glucosamine and [35S]sulfate at various times in order to assess synthesis of glycoconjugates during embryonic development. During thein vitro culturing and labeling procedures employed, the embryos display the morphogenetic changes corresponding to normal postimplantation development and proceed from gastrula, through primitive streak formation, to the early somite stages. The results of gel filtration analysis of the glycopeptides produced by Pronase digestion of the total glycoconjugates indicated that cultured embryos synthesize three main classes of saccharide chains; the synthesis of these three classes increases markedly during development. One class, derived from proteoglycans, consists of the large molecular weight glycosaminoglycans (>10,000 daltons), heparan sulfate, hyaluronic acid, and chondroitin and/or dermatan sulfate. A second class, derived from glycoproteins, is composed of a mixture of relatively low molecular weight (1500–3200 daltons) glycopeptides, consisting of 40% neutral and 60% acidic oligosaccharide chains. The third class of saccharide chains, intermediate in molecular weight (4000 to >10,000 daltons) and presumed to be derived from glycoproteins, contains a GlcNAc → Gal disaccharide repeating structure as well as terminal sialic acid residues. This recently discovered class of glycopeptides accounts for 30–50% of the total [3H]hexosamine-labeled glycopeptides. Duringin vitro development and organogenesis in these mouse embryos, the proportion of label incorporated into the smaller molecular weight glycopeptides slightly increased, whereas that in glycosaminoglycans decreased. In contrast, the proportion of label found in the glycopeptides containing repeating GlcNAc → Gal disaccharide units remained relatively constant during development from the blastocyst attachment stage through the early somite stages.