Symbol Nomenclature for Graphical Representations of Glycans

Abstract

Glycans are among the most complex biological molecules found in nature, being composed of monosaccharide units in various combinations and linkages, and featuring diverse and asymmetric types of branching. Until the 1970s, glycan structures were generally represented in scientific publications as chemically accurate drawings, or using standard IUPAC-approved abbreviations (Sharon 1986; McNaught 1997; Chester 1998). However, given the complexity of many glycan structures, it became difficult to represent such molecules in publication figures, especially those involving multistep biosynthetic pathways or multiple structures. Thus, various investigators began to use symbols to represent monosaccharides in glycans. In 1978, Kornfeld and colleagues put forward an elegant and simple system for representation of vertebrate glycans (Kornfeld et al. 1978), and it entered into popular use over the next two decades. This system was eventually adopted and standardized by the editors of the first edition of the textbook Essentials of Glycobiology (Varki et al. 1999). While this adoption increased the popularity of the symbols, the system had some limitations and inconsistencies and did not take advantage of color. Anticipating a revision, the editors developed an updated symbol nomenclature, which was made available to the community in 2005 before the publication of the Second Edition (Varki, Cummings, Esko, Freeze, Stanley, Bertozzi, et al. 2009). This nomenclature was adopted and widely disseminated, especially by the NIGMS-funded Consortium for Functional Glycomics (CFG), which also consulted the scientific community on this issue, thus enhancing acceptance. The official version of the Second Edition nomenclature has since been available in the online version of the textbook. A suggested extended version was then presented at the website Glycopedia. Meanwhile, alternate symbol nomenclature systems have been proposed (Harvey et al. 2009). Issues regarding nomenclature tend to be more controversial than the underlying science (Varki, Cummings, Esko, Freeze, Stanley, Marth, et al. 2009), as there is never one correct answer, and some aspects are matters of taste. For example, the two systems mentioned each have some relative advantages and disadvantages.