Gap junctional units are functionally expressed before first cleavage in the early ascidian embryo.
Manually apposed ascidian zygotes established electrical communication within 50 min of fertilization and before cytokinesis. Junctional conductance between zygotes was 14.5 +/- 2.9 nS (n = 7), similar to that previously reported for ascidian two-cell-stage blastomeres, suggesting that zygotes and blastomeres express an equivalent number of gap junctional half-channels. Because puromycin at 400 microM does not inhibit the functional expression of these half-channels, they appear to be of maternal origin and their activation does not require protein synthesis. Loading zygotes with 500 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid or exposing zygotes to 10 microM of the calcium ionophore A-23187 shows that these half-channels are regulated by intracellular calcium, consistent with the behavior of these channels in adult tissues. The results show that gap junctional units are expressed in the ascidian at the zygote stage.
Tosti
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Department of Cell and Developmental Biology, Stazione Zoologica, Naples, Italy.
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002938:Ciona intestinalis / Q000196:embryology*; D002970:Cleavage Stage, Ovum; D004492:Edetic Acid / Q000494:pharmacology; D004625:Embryo, Nonmammalian / Q000502:physiology; D017629:Gap Junctions / Q000187:drug effects / Q000502:physiology*; D007476:Ionophores / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011691:Puromycin / Q000494:pharmacology; D013997:Time Factors; D015053:Zygote / Q000187:drug effects
D007476:Ionophores; D011500:Protein Synthesis Inhibitors; D000001:Calcimycin; D011691:Puromycin; D004492:Edetic Acid