Second meiotic spindle integrity requires MEK/MAP kinase activity in mouse eggs.
ERK-type MAP kinase activity is required for normal first meiotic (MI) metaphase spindle dynamics and first polar body formation at the MI/MII transition, and for MII arrest until egg activation. MEK and MAPK, however, remain active until meiosis is completed and pronuclei form, but whether MEK/MAPK activity affects MII spindle function during egg activation has been unknown. Polarized light microscopy revealed that the MII spindle rapidly (within approximately 15 min) lost birefringence upon treatment of the egg with U0126, indicating decreased organization at the molecular level upon MEK inhibition. In contrast, birefringence rapidly increased when MPF was inhibited with roscovitine, and this was similar to the increased birefringence previously shown after fertilization or parthenogenetic activation with Sr(2+). Confocal microscopy indicated that many spindles in U0126-activated eggs had failed to rotate or were dissociated from the egg cortex. Subsequently, abnormally-located midbodies were evident in U0126-induced parthenogenotes. Thus, MEK/MAPK activity is required to maintain the ordered structure of the MII spindle and for normal spindle dynamics during second polar body formation.
Petrunewich
Mary Ann
MA
Ottawa Health Research Institute, Ottawa, Ontario, Canada.
Trimarchi
James Robert
JR
Hanlan
Amy Katherine Lindsey
AK
Hammer
Mary-Anne
MA
Baltz
Jay Martin
JM
D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D002478:Cells, Cultured; D046149:Embryo Culture Techniques; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D058851:GPI-Linked Proteins; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D008297:Male; D008540:Meiosis / Q000187:drug effects / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000378:metabolism; D000090204:Mesothelin; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D009570:Nitriles / Q000494:pharmacology; D010063:Ovum / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D008941:Spindle Apparatus / Q000187:drug effects / Q000378:metabolism / Q000502:physiology
D002070:Butadienes; D004791:Enzyme Inhibitors; D058851:GPI-Linked Proteins; D008562:Membrane Glycoproteins; C000715528:Msln protein, mouse; D009570:Nitriles; C113580:U 0126; D020930:MAP Kinase Kinase Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D000090204:Mesothelin