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Gap junctional units are functionally expressed before first cleavage in the early ascidian embryo
1Department of Cell and Developmental Biology, Stazione Zoologica, Naples, Italy.
The American Journal of Physiology
|May 1, 1997
Summary
Ascidian zygotes establish electrical communication before cell division, indicating gap junctions are present early. These maternal gap junctional half-channels are calcium-regulated and do not require new protein synthesis for activation.
Area of Science:
- Developmental Biology
- Cell Biology
- Molecular Biology
Background:
- Gap junctions facilitate direct cell-to-cell communication in various tissues.
- Previous studies indicated gap junctional communication in early ascidian development.
Purpose of the Study:
- To investigate the presence and characteristics of gap junctional communication in newly fertilized ascidian zygotes.
- To determine the developmental timing and regulatory mechanisms of gap junctions in early ascidian embryos.
Main Methods:
- Electrical coupling measurements between manually apposed ascidian zygotes.
- Assessment of protein synthesis requirement using puromycin.
- Investigation of intracellular calcium regulation using chelators and ionophores.
Main Results:
- Electrical communication was established within 50 minutes of fertilization, prior to cytokinesis.
- Junctional conductance was measured at 14.5 +/- 2.9 nS, comparable to two-cell stage blastomeres.
- Gap junctional half-channels are of maternal origin, do not require protein synthesis for activation, and are regulated by intracellular calcium.
Conclusions:
- Gap junctional units are expressed at the ascidian zygote stage.
- Early expression suggests a role for gap junctions in maternal provisioning or initial developmental signaling.
- Calcium regulation of these channels is conserved from zygote to adult stages.