Possible involvement of mitogen- and stress-activated protein kinase 1, MSK1, in metaphase-II arrest through phosphorylation of EMI2 in mouse oocytes

Dev Biol. 2011 Nov 1;359(1):73-81. doi: 10.1016/j.ydbio.2011.08.021. Epub 2011 Sep 5.


Ovulated oocytes are arrested at the metaphase of second meiotic division. The metaphase-II arrest in Xenopus oocytes is regulated by RSKs located downstream of the Mos-MAPK pathway. In mice, other kinase(s) besides RSKs may be responsible for the metaphase-II arrest, because RSK1/RSK2/RSK3-triple knockout mice exhibit no obvious phenotype. Here, we show the subcellular localization and possible role of mitogen- and stress-activated kinase 1, MSK1 known as another downstream kinase of the Mos-MAPK pathway, in the mouse oocytes. Immunostaining analysis indicated that MSK1 is present in the germinal vesicle (GV) and cytoplasm of oocytes at the GV and metaphase-II stages, respectively. An active, phosphorylated form of MSK1 was predominantly localized to the metaphase-II spindle. The inhibition of the MSK1 activity failed to maintain the sister chromatid alignment within the metaphase-II plate. Importantly, MSK1 exhibited the ability to phosphorylate four Ser/Thr residues of meiotic cell-cycle regulator EMI2. The phosphorylation was required for up-regulation of the EMI2 activity in the oocytes. These results suggest that mouse MSK1 may play a key role in the metaphase-II arrest through phosphorylation of EMI2.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Cell Line
  • DNA Primers
  • F-Box Proteins / chemistry
  • F-Box Proteins / metabolism*
  • Humans
  • Metaphase*
  • Mice
  • Molecular Sequence Data
  • Oocytes / enzymology
  • Oocytes / metabolism*
  • Phosphorylation
  • Reverse Transcriptase Polymerase Chain Reaction
  • Ribosomal Protein S6 Kinases, 90-kDa / metabolism*
  • Sequence Homology, Amino Acid
  • Subcellular Fractions / enzymology


  • DNA Primers
  • Emi2 protein, mouse
  • F-Box Proteins
  • Ribosomal Protein S6 Kinases, 90-kDa
  • mitogen and stress-activated protein kinase 1