Glycocoding as an Information Management System in Embryonic Development

Abstract

The past 5 years have seen a burgeoning in the amount of data emerging from laboratories studying the early stages of embryogenesis. Much of this data implicates various aspects of glycobiology in the initiation and regulation of these processes. The level of analytical detail coming from these investigations has surpassed our ability to fully understand its overall significance within the context of the interactive/dynamic developmental process. This review proposes a pause in this seemingly endless quest for more detail so that we may take stock of our goals and objectives. The proposed goals include a mechanistic understanding of the process(es) involved in information managed at various ‘transition points’ during early embryogenesis, and an understanding of the mechanism(s) by which the spatial/temporal regulation of early development are managed. The ‘transitions’ which occur during cell to cell cluster, cell cluster to early organ architecture, and early organ architecture to functional organ development are fundamental and mirror the evolutionary process of biological information management. All of these ‘transitions’ involve increasing complexity, the development of hierarchies of information management systems (integrated bidirectionally), and spatial/temporal regulation which relies on historical events to map future structure and function. This review focuses on a relatively small number of studies which highlight these aspects of early development. A mechanism which involves glycocoding, an extension of the Roseman Hypothesis, and its direct use as an information management system is proposed and some supporting experimental evidence is presented. This extension of an existing hypothesis is related to several recent investigations, and is designed to broaden the experimental design of future studies so that these important process issues can be addressed.

Signaling Pathways for Transduction of the Initial Message of the Glycocode into Cellular Responses

“…Figure 1A depicts common lectin targets, among which soluble glycoproteins, different types of membranebound or matrix-associated glycoproteins, proteoglycans and glycolipids, such as glycosphingolipids, cerebrosides and gangliosides as carriers for the lectin-reactive sugar determinants are predominant. Whereas other articles in this issue deal with the structural and biosynthetic aspects of the ligands and their location [Brinck et al, 1998;Brockhausen et al, 1998;Danguy et al, 1998;Geyer and Geyer, 1998;Hakomori, 1998;Mann and Waterman, 1998;Plendl and Sinowatz, 1998;Sharon, 1998;Zschäbitz, 1998], this review will focus on describing ways of signal transmission downstream from the binding event.…”

Animal Lectins as Cell Adhesion Molecules

“…Focusing on the type of molecular interaction, not only protein-protein recognition is operative. As similarly emphasized by Sinowatz et al [1998] and Mann and Waterman [1998] in this issue, another fundamental molecular interaction makes a pivotal contribution to the accuracy and versatility of cell interactions. Based on the enormous potential of sugar structures to code biologi-cal information [Laine, 1997] and on the presence of lectins as receptors for such structures in animal tissues [Gabius, 1991[Gabius, , 1997aZanetta, 1997Zanetta, , 1998; for a collection of recent reviews, see , it has been evident that protein-carbohydrate interactions play a crucial role in recognitive events.…”

Characterization of a Novel Drosophila melanogasterGalectin

“…Cell surface carbohydrates have been proposed to function in cellular recognition events during embryogenesis, because the synthesis and presentation of diverse carbohydrate structures are spatially and temporally regulated during development (7,8,60,61). In addition, carbohydrate modifications during Drosophila embryogenesis have been shown to regulate the activity of developmental proteins such as Notch, allowing Notch to be spatially activated along a discrete boundary of cells (62,63).…”