Worm Breeder's Gazette 14(4): 34 (October 1, 1996)
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.
|1||Zoological Institute, University of Koeln, 50923 Germany|
|2||Dept. of Biology, Indiana University, Bloomington, IN 47405, USA|
The pattern of cell-cell communication in embryos of C.elegans has beeninvestigated by injecting tracer dyes into individual blastomeres (Bossinger and Schierenberg, 1992). It has been shown that in embryos from the 4-cell stage onward all blastomeres are well coupled for the diffusion of negatively charged Lucifer Yellow (LY; MW 457 Da) while uncharged Rhodamin-coupled dextran (MW 4.000 - 70.000 Da) remains restricted to the injected cell and its descendants. However, in Cephalobus spec. (another soil nematode), LY and Rhodamin-dextran (even at a molecular weight of 70.000 Da) diffuse along discrete pathways from cell to cell (Bossinger and Schierenberg, 1996). We extended our dye-coupling studies in C. elegans using negatively charged dextrans (LY-dextran and FITC-dextran) with molecular weights of 10.000 and 70.000 Da. Suprisingly, we found that in embryos between the 4-and the 24-cell stage all blastomeres are coupled for negatively charged dextrans whereas under all tested conditions uncharged Rhodamin-dextran (MW 10.000 Da) remains in the injected cell and its descendants. The diffusion of the negatively charged dyes appears to occur quickly and freely between all blastomeres. In contrast to Cephalobus we did not observe preferential pathways of dye spread from the injected cell, suggesting that all blastomeres are equally coupled. However at the 24-cell stage, when the primordial germline cell P4 has been generated, diffusion into D and P4 cells becomes retarded.The diffusion block lasts approximately 5 minutes until D joins the somatic compartment and P4 remains uncoupled for at least 20 min. A similar observation has been made for the much smaller LY in C. elegans indicating that it is a diffusion block and not a reduction in channel diameter. In summary, our findings suggest that in the developing C. elegans embryo all somatic blastomeres are coupled by communication channels much larger than conventional gap junctions. These channels seem to be permeable for negatively charged molecules up to a molecular weight of at least 70.000 Da but are impermeable to uncharged dextrans. Moreover, these channels seem to be equally present between all blastomeres of the somatic cells. Presently we can only speculate about the function of these communication pathways. Bossinger, O; Schierenberg, E. (1992) Dev. Biol. 151: 401-409 Bossinger, O; Schierenberg, E. (1996) Dev. Genes Evol. 206: 25-34