FIGURE 8.

A mutation in the fringe gene decreases the prevalence of the O-Fuc trisaccharide and the linear core 1 structure. Embryos collected from adults heterozygous for the fng¹³ mutation carried over a GFP balancer chromosome (TM3-GFP) were manually sorted by fluorescence (supplemental Fig. 7), yielding 884 homozygous fng¹³ late-stage embryos and a pool of age-matched control siblings (mixed fng¹³/TM3-GFP heterozygotes and TM3-GFP homozygotes). O-Linked glycans were prepared from the sorted embryos and from w¹¹¹⁸ embryos, the genetic background in which the fng¹³ mutation is maintained. A, the prevalence of acidic glycans is decreased in fng mutant embryos. A corresponding increase in neutral glycans is driven almost entirely by a higher relative prevalence of the core 1 disaccharide (Structure 2). B, two of the three major glucuronylated O-linked glycans are reduced in fng mutant embryos as a percent of the total profile, including the O-Fuc trisaccharide (Structure 9), which is predicted to require Fng enzyme activity for its biosynthesis. C, normalized to total fatty acid content, the MS signal intensities for the O-Fuc trisaccharide and for the linear core 1 trisaccharide (Structure 4) decrease in proportion to the dose of the mutant fng gene. The amount of the branched, glucuronylated core 1 trisaccharide (Structure 5) is unchanged by loss of Fng function.