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The nematode Caenorhabditis elegans is an excellent model organism for studies of glycan dynamics, a goal that requires tools for imaging glycans in vivo. Here we applied the bioorthogonal chemical reporter technique for the molecular imaging of mucin-type O-glycans in live C. elegans. We treated worms with azidosugar variants of N-acetylglucosamine (GlcNAc), N-acetylgalactosamine (GalNAc), and N-acetylmannosamine (ManNAc), resulting in the metabolic labeling of their cell-surface glycans with azides. Subsequently, the worms were reacted via copper-free click reaction with fluorophore-conjugated difluorinated cyclooctyne (DIFO) reagents. We identified prominent localization of mucins in the pharynx of all four larval stages, in the adult hermaphrodite pharynx, vulva and anus, and in the tail of the adult male. Using a multicolor, time-resolved imaging strategy, we found that the distribution and dynamics of the glycans varied anatomically and with respect to developmental stage.

Heat-shock protein 43 (HSP43) of Caenorhabditis elegans is prominently expressed in the utse cell, which attaches the uterus to the hypodermis, the uv1 cells joining the vulva and the uterus, the spermathecal valve and junctions between cells of the spermathecal cage. In body-wall muscle, HSP43 forms a punctate pattern of circumferential lines, probably corresponding to regions where the hypodermis contacts the muscle cells.

In C. elegans, the LET-23 receptor tyrosine kinase is localized to the basolateral membranes of polarized vulval epithelial cells. lin-2, lin-7, and lin-10 are required for basolateral localization of LET-23, since LET-23 is mislocalized to the apical membrane in lin-2, lin-7, and lin-10 mutants. Yeast two-hybrid, in vitro binding, and in vivo coimmunoprecipitation experiments show that LIN-2, LIN-7, and LIN-10 form a protein complex. Furthermore, compensatory mutations in lin-7 and let-23 exhibit allele-specific suppression of apical mislocalization and signaling-defective phenotypes. These results present a mechanism for basolateral localization of LET-23 receptor tyrosine kinase by direct binding to the LIN-2/LIN-7/LIN-10 complex. Each of the binding interactions within this complex is conserved, suggesting that this complex may also mediate basolateral localization in mammals.

We have identified a new Caenorhabditis elegans NK-2 class homeobox gene, designated ceh-24. Distinct cis-acting elements generate a complex neuronal and mesodermal expression pattern. A promoter-proximal enhancer mediates expression in a single pharyngeal muscle, the donut-shaped m8 cell at the posterior end of the pharynx. A second mesodermal enhancer is active in a set of eight nonstriated vulval muscles used in egg laying. Activation in the egg laying muscles requires an 'NdE-box' consensus motif (CATATG) which is related to, but distinct from, the standard E-box motif bound by the MyoD family of transcriptional activators. Ectodermal expression of ceh-24 is limited to a subset of sublateral motor neurons in the head of the animal; this activity requires a cis-acting activator element that is distinct from the control elements for pharyngeal and vulval muscle expression. Activation of ceh-24 in each of the three cell types coincides with the onset of differentiation. Using a set of transposon-induced null mutations, we show that ceh-24 is not essential for the formation of any of these cells. Although ceh-24 mutants have no evident defects under laboratory conditions, the pattern of ceh-24 activity is apparently important for Rhabditid nematodes: the related species C. briggsae contains a close homologue of C. elegans ceh-24 including a highly conserved and functionally equivalent set of cis-acting control signals.