Project: Research project

Project Details


The tunicate embryo, which proceeds from fertilization to swimming larva in
about 18 hours (in the case of Ciona intestinalis), provides a remarkable
preparation for the study of the role of intercellular communication in
development. Preliminary data indicate compartmentation of dye coupling;
the mechanisms whereby these compartments are formed will be investigated.
Gap junctions in the ascidians show voltage dependence and the blastomeres
exhibit two stable resting potentials sufficiently far apart to shut down
junctional conductance and uncouple cells; these properties could lead to
transient or reversible compartment formation. Determination of regional
differences in resting potential, already indicated by differences in
intensity of fluorescence observed with slow voltage sensitive dyes, will
be validated with microelectrode measurement. Such regional differences
must occur if voltage dependence of junctional conductance accounts for
compartment formation. Alternatively the distribution of gap junctions
might be the controlling factor. Measurement of coupling coefficients
along with resting potentials would establish this mechanism of compartment
formation. Some inductive interactions are known; electrical coupoing
between participating cells will be assayed over time and compared to that
between other cells where developmental information is not being
transmitted. Effects of antibodies on junctional properties will be
assayed and their use in exploration of the role of gap junctions in
development explored. Studies of gap junctions from other embryos will be continued. Sensitivity
to H and Ca will be assayed as part of an ongoing comparative study.
Permeability will be correlated with conductance during treatments
modulating junctional conductance. The results will provide information
about the permeation process and indicate whether channel closure is
all-or-none or graded. Reconstitution will be attempted in a three, rather
than a two, compartment system. Improvements in perfusion media will be
sought with a view to understanding cellular control of junction formation
and removal, and parallel studies will be carried out on intact cells.
Phosphorylation of junction protein has been demonstrated and
pharmacological treatments of intact cells suggest an involvement in
control of junctional conductance in a number of systems. The availability
of antibodies and the imminent availability of the cDNA will make the cell
biology of gap junctions accessible.
Effective start/end date12/31/8911/30/91


  • Embryology
  • Medicine(all)
  • Cell Biology


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