[Location and role of protein kinase Cα in parthenogenetic and tetraploid preimplantation embryonic development in mouse].

ABSTRACT

Protein kinase C (PKC) is a critical molecule in cellular signal transduction in mammals. It is involved in many biological processes in embryonic development, including nuclear remodeling, cell cycle adjustment and cellular polarity regulation. The present study aimed to observe the location of PKCα, an important isozyme of PKC, in fertilized, parthenogenetic and tetraploid preimplantation embryos, and compare the expression of PKCα during embryonic compaction in Kunming mice. The location of PKCα was detected by immunochemistry and laser confocal microscopy. Western blot was performed to quantify PKCα expression during embryonic compaction in the three kinds of embryos. In the experiment, fertilized embryos were flushed from oviduct or uterus at 45, 52, 69, 76 and 93 h after injection of human chorionic gonadotrophin (hCG); parthenogenetic embryos were collected by SrCl2 activation of oocytes for 6 h; and tetraploid embryos were produced by electrofusion of 2-cell embryos. Embryos were fixed at different developmental stages for immunofluorescent staining. 8-cell/4-cell embryos and morula were lysed for Western blot. The results showed that PKCα had similar location pattern in different embryos. It was distributed mainly in the nuclear aggregating around chromatin at different developmental stages. However, PKCα expressed strongly in the interphase than in mitotic blastomere. Before embryonic compaction, PKCα was localized at the blastomere boundary. At late blastocyst stage of fertilized embryos, PKCα was localized only in the polar trophoblast, but not in other trophoblast. At late stage of pathenogenetic blastocyst, there was no clear PKCα signal in the polar trophoblast. Tetraploid embryos had larger blastomere than other embryos and compacted after 4-cell stage, but not after 8-cell stage. Meanwhile, there was PKCα signal at the blastomere boundary at 4-cell stage. Our results showed that the expression of PKCα lasted through all the preimplantation stage. Although there were different expression levels among different stages, the expression increased around embryonic compaction. Quantification of expression of PKCα by Western blot demonstrated that the expression increased after compaction, indicating that the compaction was possibly dependent on the relocation of PKCα. Moreover, it was shown that the second relocation of PKCα occurred during the blastocyst formation. PKCα had different expression patterns in the three kinds of preimplantation embryos. However, the effects of PKCα on embryonic development started in early stage. There must be a necessary connection between PKCα relocation and cell adhesion starting at embryonic compaction.