Increased parthenogenetic development of bovine and porcine oocytes activated with a combination of a protein synthesis and phosphorylation inhibitor

Calcium ionophores such as A23187 (A) are used to artificially trigger the release of free intracellular Ca2+ within oocytes. Calcium ionophores cannot effectively induce parthenogenetic development in bovine and porcine oocytes alone. Therefore, it is necessary to combine the ionophore with either a protein synthesis inhibitor or a phosphorylation inhibitor to initiate development. Cycloheximide (CHX), maintains low MPF activity in the oocyte by inhibiting cyclin B synthesis. Exposing oocytes to 6-dimethylaminopurine (6-DMAP) induces early inactivation of MAPK through the dephosphorylation of ERK2. Regulating these proteins is critical as they are responsible for the resumption of meiosis and microtubule/chromatin organization. These studies were designed to compare the cell cycle progression and development of bovine and porcine oocytes activated with CHX and 6-DMAP alone or in combination with each other. Oocytes treated with the triple chemical combination of A23187, CHX and 6-DMAP had significantly higher rates of blastocyst development compared to conventional activation methods. It is possible that the combination of a protein synthesis inhibitor and a phosphorylation inhibitor better mimics natural fertilization by inactivating both MPF and MAPK. Results from this study may be beneficial to other areas of biotechnology such as cloning in which chemical activation is required for development.