Date of Award


Degree Type


Degree Name

Doctor of Philosophy


In the preimplantation mouse embryo, intercellular coupling is acquired in the 8-cell stage during the process of compaction. The presence of permeable cell-to-cell membrane channels (gap junctions) was detected by measuring ionic coupling and by observing the intercellular transfer of fluorescent dye. The rate of fluorescent dye movement within 8-cell embryos increases as they undergo compaction, suggesting that the number of junctional channels between cells increases as development progresses. Compacted 8-cell embryos, when aggregated, are capable of forming inter-embryonic junctional channels after 2 to 3 hours of contact; however the number of channels between embryos is small since aggregated embryos exhibited ionic coupling but very weak dye coupling. In order to test whether gap junctions could be induced to form prematurely, compacted 8-cell embryos were aggregated with 2-cell or 4-cell embryos. Permeable junctional channels did not form between these embryos even by 10 hours after aggregation.;The inhibitors, (alpha)-amanitin and cycloheximide, were used to assess the requirement of new transcription and translation for cleavage to the 8-cell stage and compaction. Transcription of the embryonic genome and de novo protein synthesis are required for both these events, as indicated by the time-dependent sensitivity to the inhibitors. The effect of (alpha)-amanitin and cycloheximide on the acquisition of intercellular junctional communication in the 8-cell stage was examined. Ionic coupling was detected in compacted 8-cell embryos which had been treated with either (alpha)-amanitin or cycloheximide from the early 4-cell stage; however, dye coupling was weak, or undetectable in some embryos. The formation of inter-embryonic junctional channels between aggregated, compacted 8-cell embryos can be entirely prevented by inhibiting protein synthesis, suggesting that externally-facing cell membranes are depleted of junctional components when junctions are formed during compaction.;It is proposed that intercellular junctional coupling acquired in the 8-cell stage initially utilizes junctional components that are present prior to the 8-cell stage, but that continued protein synthesis is required for the increase in junctional coupling observed as embryos progress through the 8-cell stage and beyond.



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