Assembly of the trilaminar eggshell and development of the permeability barrier after fertilization in C. elegans are distinct in their timing and mechanism.

To facilitate qualitative and quantitative analysis of glycosaminoglycans, we tagged the reducing end of lyase-generated disaccharides with aniline-containing stable isotopes ( 12 C 6 and 13 C 6 ). Because different isotope tags have no effect on chromatographic retention times but can be discriminated by a mass detector, differentially isotope-tagged samples can be compared simultaneously by liquid chromatography/mass spectrometry and quantified by admixture with known amounts of standards. The technique is adaptable to all types of glycosaminoglycans, and its sensitivity is only limited by the type of mass spectrometer available. We validated the method using commercial heparin and keratan sulfate as well as heparan sulfate isolated from mutant and wild-type Chinese hamster ovary cells, and select tissues from mutant and wild-type mice. This new method provides more robust, reliable, and sensitive means of quantitative evaluation of glycosaminoglycan disaccharide compositions than existing techniques allowing us to compare the chondroitin and heparan sulfate compositions of Hydra vulgaris, Drosophila melanogaster, Caenorhabditis elegans, and mammalian cells. Our results demonstrate significant differences in glycosaminoglycan structure among these organisms that might represent evolutionarily distinct functional motifs.Metazoans make several types of sulfated glycosaminoglycans (GAGs), 2 including keratan sulfate (KS), chondroitin sulfate/dermatan sulfate (CS/DS), and heparan sulfate/heparin (HS). Each type of chain consists of unique disaccharide units. KS consists of galactose (Gal) and GlcNAc ([Gal␤1, 4GlcNAc␤1,3] n ) with variable sulfation at C6 of either sugar. CS/DS assembles as a copolymer of GlcA␤1,3GalNAc␤1,4 and then undergoes various processing reactions, including C5 epimerization of a portion of GlcA units to iduronic acid in DS, O-sulfation at C2 and more rarely at C3 of the uronic acids, and O-sulfation at C4 and C6 of the GalNAc residues (1). HS is the most highly modified GAG, consisting initially of GlcA␤1,4GlcNAc␣1,4 units, which then undergo variable processing by GlcNAc N-deacetylation and N-sulfation, C5 epimerization of some GlcA units to iduronic acid, and O-sulfate addition to C2 of the uronic acids and C6 and more rarely at C3 of the glucosamine units (2). The arrangement of the modified residues along the chain creates binding sites for numerous growth factors, enzymes, and extracellular matrix proteins. The structural variation that can occur makes sulfated GAG chains one of the most complex classes of macromolecules found in nature.GAG fine structure is typically assessed by analyzing the disaccharide composition of an isolated mixture of chains. A number of techniques have been developed to accomplish this task that rely on chemical or enzymatic depolymerization of the chains into their constituent disaccharides, followed by separation via anion exchange chromatography, reversed-phase chromatography with ion pairing agents, or capillary electrophoresis. These techniques separate...

Defects in glycosaminoglycan biosynthesis disrupt animal development and can cause human disease. So far much of the focus on glycosaminoglycans has been on heparan sulphate. Mutations in eight squashed vulva (sqv) genes in Caenorhabditis elegans cause defects in cytokinesis during embryogenesis and in vulval morphogenesis during postembryonic development. Seven of the eight sqv genes have been shown to control the biosynthesis of the glycosaminoglycans chondroitin and heparan sulphate. Here we present the molecular identification and characterization of the eighth gene, sqv-5. This gene encodes a bifunctional glycosyltransferase that is probably localized to the Golgi apparatus and is responsible for the biosynthesis of chondroitin but not heparan sulphate. Our findings show that chondroitin is crucial for both cytokinesis and morphogenesis during C. elegans development.

Genetic and genome-wide RNAi approaches available in C. elegans, combined with tools for visualizing subcellular events with high-resolution, have led to increasing adoption of the early C. elegans embryo as a model for mechanistic and functional genomic analysis of cellular processes. However, a limitation of this system has been the impermeability of the embryo eggshell, which has prevented the routine use of small molecule inhibitors. Here, we present a method to permeabilize and immobilize embryos for acute inhibitor treatment in conjunction with live imaging. To identify a means to permeabilize the eggshell, we used a dye uptake assay to screen a set of 310 candidate genes defined by a combination of bioinformatic criteria. This screen identified 20 genes whose inhibition resulted in >75% eggshell permeability, and 3 that permeabilized embryos with minimal deleterious effects on embryo production and early embryonic development. To mount permeabilized embryos for acute drug addition in conjunction with live imaging, we combined optimized inhibition of one of these genes with the use of a microfabricated chamber that we designed. We demonstrate that these two developments enable the temporally controlled introduction of inhibitors for mechanistic studies. This method should also open new avenues of investigation by allowing profiling and specificity-testing of inhibitors through comparison with genome-wide phenotypic datasets.