Transcriptional activation of the embryonic genome initiates at 2-cell stage in mouse embryo and is characterized by the synthesis of TRC which is restricted to 2-cell stage. To investigate the roles of various protein kinases on the embryonic
gene
activation, the effects of protein kinase inhibitors on in vitro development and protein synthetic profiles of the early mouse embryos were examined.
None of α-amanitin which is a mRNA synthetic inhibitor, H8 which is a PKA inhibitor, and H7 which is a PKC inhibitor, affected on first cleavage of mouse 1-cell embryos in vitro. However, all of these drugs inhibited the second cleavage. When
the
drugs
were removed following treatment for 6 hours, H8 or H7 showed little inhibition on subsequent development of 1-cell embryos to 2-cell stage or further. In contrast, α-amanitin irreversibly inhibited the development of 1-cell embryos to 2-cell
stage
following of the drug. Genistein, a TPK inhibitor, inhibited both the first cleavage of 1-cell embryos and the second cleavage of 2-cell embryos, suggesting that TPK activity may be important during the early cleavages.
All of the above four drugs inhibited TRC synthesis as shown by the fluorographic analysis of [35S]-Met labeled protein profiles. When late 1-cell embryos treated with H7 and analyzed synthetic patterns of [35S]-Met labeled protein, the
quantitative
differences of protein synthesis on SDS-PAGE appeared on 77 kD and 33 kD region at 32~38 hours post hCG.
From these studies, transcriptional activation of embryonic genome is not essenting to the mouse 1-cell embryos to develop to 2-cell stage. Hawever, TPK activity is reguisite for both the first cleavage and second cleavage. Similarly, both PKC
and
PKA
activities are required for the second cleavage of mouse embryos, but not for the first cleavage.
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