Research Highlights

Fucosyltransferases: A roundworm round up

Fluorescence-based microscopic images (G, I) of transgenic C. elegans expressing a CEFT-1:: green fluorescent protein (GFP) reporter construct and light microscopic images (H, J) of the corresponding C. elegans profile. Expression of CEFT-1:GFP reporter in adult head (G,H) and tail (I,J).
Copyright © 2007 Oxford University Press

Fucose is a hexose with a 6^th carbon atom that is a methyl instead of a hydroxy  group and is the most common terminating carbohydrate in living organisms besides sialic acid. Thus, fucose is involved in a broad variety of signaling and recognition events. However, a systematic exploration of the 150 fucosyltransferase genes identified in public sequence databases has been missing. In C. elegans, each developmental stage is characterized by specific N-glycan structures, making the organism a well suited model to study the effects of glycosylation. Now in Glycobiology, Nguyen et al. explore biochemical and physiological properties of the entire group of 1,3 fucosyltransferases in C. elegans (CEFTs).

Nguyen et al. discovered five 1,3 CEFTs (CEFT-1 to CEFT-5) by sequence comparison using a sequence motif known to be characteristic for these enzymes in other species and explored the biochemical properties of the native fucosyltransferases. They demonstrated that CEFT-1 to CEFT-4 have differing N-glycan acceptor specificities, while CEFT-5 does not exhibit any activity towards the acceptors used, suggesting that it might act on an entirely different glycan structure.

Nguyen et al. showed in vivo that CEFT expression was differentially distributed within regions of the developing roundworm; for instance, CEFT–1 promotor activation was restricted to chemosensory neurons and valve regions. In contrast, all CEFTs were expressed at every stage of C. elegans development. Mutagenesis of the CEFT genes and exploration of the resulting phenotypes revealed a lack of 1,3-fucosylated N-glycan core structures in the CEFT-1 mutant, however, the authors did not observe a reduction in life span or any other behavioral or physiological defects. These results indicate that individual CEFTs are not required for worm development.

As C. elegans has 30 fucosyltransferase genes in total, the authors speculate that other CEFT group members may also be locally expressed, which is consistent with their studies on other types of fucosyltransferases published previously. Furthermore, the large number of CEFTs may be an echo of the helminthic defense mechanisms directed against host immune systems. C. elegans appears to be able to compensate for the loss of individual CEFTs, and it is possible that other fucosylated glycans may substitute the functions of CEFT-glycosylated structures. Multiple CEFT knockouts might demarcate the physiological and immunological functions of fucosylated glycans in C. elegans in future studies.

Author: Mirko von Elstermann