Inhibition of the Arp2/3 complex impairs early embryo development of porcine parthenotes

The Arp2/3 complex, which nucleates actin filaments, comprises a stable assembly of seven-protein subunits including two actin-related proteins (Arp2 and Arp3). Previous work showed that Arp2/3 binds to the sides of actin filaments and is concentrated at the leading edges of motile cells. In the present study, we show that the Arp2/3 complex is critical for cytokinesis during early embryonic development in porcine parthenotes. The Arp2/3 complex is concentrated at the cortex of each cell at the 1-, 2-, and 4-cell stages, and at the periphery at the morula stage. The amount of Arp2/3 significantly decreased at the blastocyst stage in parthenogenetically activated porcine embryos. Inhibition of the Arp2/3 complex in the pig embryos by the Arp2/3-specific inhibitor CK666 resulted in abnormal cell division, a decrease in developmental rate and total cell numbers, and an increase in the ratio of trophectoderm cell number to inner cell mass number in blastocyst-stage embryos. In addition, 4-cell stage embryos subjected to CK666 treatment exhibited significantly decreased expression of ZGA genes (Pou5f1, Sox2, and Nanog), suggesting that the Arp2/3 complex plays an important role in early porcine embryo development. Thus, our data demonstrate that the Arp2/3 complex is required for early embryonic development in pigs and appears to regulate the expression of pluripotency genes.