Phosphorylation of histone H3 on Ser10 by auto-phosphorylated PAK1 is not essential for chromatin condensation and meiotic progression in porcine oocytes

Abstract

Abstract Background The p21-activated kinase 1 (PAK1) is essential for mitosis and plays an important role in the regulation of microtubule assembly during oocyte meiotic maturation in mice; however, little is known about its role in porcine oocytes. Result Total p21-activated kinase 1 (PAK1) and phosphorylated PAK1 at Thr423 (PAK1Thr423) were consistently expressed in porcine oocytes from the germinal vesicle (GV) to the second metaphase (MII) stages, but phosphorylation of histone H3 at Ser10 (H3Ser10) was only expressed after the GV stage. Immunofluorescence analysis revealed that PAK1Thr423 and H3Ser10 colocalized on chromosomes after the GV stage. Blocking of endogenous PAK1Thr423 by injecting a specific antibody decreased the phosphorylation level of H3Ser10; however, it had no impact on chromatin condensation, meiotic progression, cleavage rate of blastomeres or the rate of blastocyst formation. Conclusion Phosphorylation of PAK1Thr423 is a spontaneous activation process and the activated PAK1Thr423 can promote the phosphorylation of H3Ser10; however, this pathway is not required for meiotic maturation of porcine oocytes or early embryonic development.