Worm Breeder's Gazette 14(1): 43 (October 1, 1995)
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
Zoologisches Institut, Universit„t K"ln, Kerpener Str. 15, 50923 K"ln,
Anionic dyes like Trypan Blue, Evans Blue and Chicago Sky Blue (MW 960-992) with their strong affinity to cationic amino acid residues of proteins bind strongly to the plasma membrane of C. elegans blastomeres. We tested whether they can prevent interactions between cells (e.g. between surface receptors and their ligands or between opposing connexons of neighboring cells. In C. elegans gap junctional communication is established from the 2- cell stage onwards. From then until the end of the proliferation phase all blastomeres remain coupled via gap junctions (Bossinger and Schierenberg, 1992; Dev. Biol. 151: 401-409). If 1- or 2-cell stages are laser perforated in a cell culture medium containing one of the tested dyes, no diffusion of injected Lucifer Yellow (indicating the presence of gap junctions) into the neighbouring cells is detectable afterwards. If the tested dyes are applied later (e.g. early gastrula) all blastomeres are well dye-coupled. The easiest interpretation of this observation is that the dyes only interfere with the establishment of gap junctions but not their function. Using these dyes in combination with inhibitors of protein biosynthesis may help us to learn more about the dynamics of gap junctional turnover in the nematode. During embryogenesis of C. elegans cellular interactions are necessary to determine the fate of blastomeres (e.g. Schierenberg, 1987, Dev. Biol. 122: 452-463; Goldstein, 1992; Nature, 357: 255-257). After application of the dyes via laser-penetration of the eggshell prior to the 6-cell stage we can inhibit the typical polarization of EMS by P2. Using high concentration of dye prior to the 6-cell stage neither birefringence nor binding of an antibody against gut (ICB4) was found. After the 6-cell stage the dyes seem to also interfere with glp-dependent cellular interactions (12-cell stage; e.g. the induction of ABa descendants by the MS cell; Priess and Thomson, 1987, Cell 48, 241-250). Preliminary results indicate that after incubation with dyes in the 8-cell stage only about 10 cells stain positively with the 3NB12 antibody against pharynx myosin indicating the absence of 7 ABax derived pharyngeal cells. Recently we showed that gut differentiation in C. elegans is accompanied by the uptake of yolk proteins (Bossinger and Schierenberg, 1992; Development, 114: 317-330). We have now analyzed the endocytotic activity of the gut primordium by using fluorescently labelled human transferrin and dextranes as markers for receptor-coupled and fluid-phase endocytosis, respectively. Under normal conditions no uptake of dextran takes place but a rapid internalization of tranferrin from the perivitelline fluid. In addition to the effects reported above, the tested dyes also inhibit endocytosis of transferrin. In conclusion, the tested azo-dyes appear to interfere with a wide spectrum of different cell-cell interactions and may be useful to unravel further, so far undetected inductions.