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.

INTERCELLULAR COMMUNICATION, EMBRYONIC INDUCTION, AND ENDOCYTOSIS INTO THE GUT PRIMORDIUM IS INHIBITED BY POLYSULFATED POLYCYCLIC HYDROCARBON DYES

Olaf Bossinger, Einhard Schierenberg

Zoologisches Institut, UniversitĄt 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.