Mitogen-activated protein kinase-activated protein kinase 2 is a critical regulator of pig oocyte meiotic maturation.

Mitogen-activated protein kinase (MAPK)-activated protein kinase 2 (MK2), a direct substrate of p38 MAPK, plays key roles in multiple cellular processes. In the present study, we showed that MK2 affected not only cumulus expansion, but also the oocyte meiotic cell cycle in porcine oocytes. Inhibition of MK2 arrested oocytes at the germinal vesicle (GV) stage or the prometaphase I/metaphase I stage. Unlike in mouse oocytes, where phosphorylated (p-) MK2 was localised at the minus end of spindle microtubules and close to the spindle poles, in porcine oocytes p-MK2 was concentrated at the spindle equator and localised at the plus end of spindle microtubules. Knockdown or inhibition of MK2 resulted in spindle defects: spindles were surrounded by irregular chromosome non-disjunction or by chromosomes detached from the spindles. MK2 regulated spindle organisation and chromosome alignment by connecting microtubules with kinetochores. In addition, unlike in mitotic cells and meiotic mouse oocytes, the MK2-p38 MAPK pathway may not play an important role during meiotic cell cycle in porcine oocytes. In conclusion, MK2 is an important regulator of porcine oocyte meiotic maturation.