Abstract
BackgroundMammalian oocyte meiotic maturation involves a number of important processes, including spindle assembly and migration, cortical reorganization and polar body extrusion. Numerous proteins contribute to these processes, but it is unknown whether MKlp2 (mitotic kinesin-like protein 2; also called KIF20A), a microtubule-associated protein that regulates cytokinesis during mitosis, is involved in oocyte maturation.MethodsConfocal microscopy, time lapse microscopy, inhibitor treatment were adopted to examine the roles of MKlp2 in mouse oocyte.ResultsImmunostaining results showed that MKlp2 localized to oocyte microtubules. Time-lapse microscopy showed that disrupting MKlp2 expression with paprotrain, a specific inhibitor of MKlp2, resulted in polar body extrusion failure. This could be rescued after rescuing oocytes from paprotrain in fresh medium. Cell cycle analysis showed that most oocytes were arrested at metaphase I or telophase I. However, oocyte spindle structure and chromosome alignment were not disrupted after the inhibition of MKlp2 by paprotrain.ConclusionsThis study demonstrated that MKlp2 is crucial for oocyte maturation by regulating polar body extrusion.
Highlights
Mammalian oocyte meiotic maturation involves a number of important processes, including spindle assembly and migration, cortical reorganization and polar body extrusion
We demonstrate that Mitotic kinesin-like protein 2 (MKlp2) is involved in mouse oocytes meiotic maturation and disruption of MKlp2 results in the failure of polar body extrusion
Expression and localization of MKLP2 during mouse oocyte meiotic maturation Oocyte samples were collected after culture for 0, 4, 8, 9.5 or 12 h, which represent the time points when most oocytes reach the GV, GVBD, MI, anaphase/telophase I (ATI) and metaphase II (MII) stages, respectively
Summary
Mammalian oocyte meiotic maturation involves a number of important processes, including spindle assembly and migration, cortical reorganization and polar body extrusion. Numerous proteins contribute to these processes, but it is unknown whether MKlp (mitotic kinesin-like protein 2; called KIF20A), a microtubule-associated protein that regulates cytokinesis during mitosis, is involved in oocyte maturation. After chromosome separation during mouse oocyte meiotic maturation, the primary oocyte generates two daughter cells, a small polar body and a highly polarized big metaphase II (MII)-arrested oocyte that awaits fertilization. Based on chromosome separation and cytokinesis, small polar body extrusion is essential for the retention of maternal components for early embryo development [2]. Previous studies showed that MKlp localized to the midzone of the spindle during anaphase and to the cleavage furrow and midbody during telophase in mitotic cells [8,10]. Controlling MKlp by Mad is important for proper mitotic progression and cytokinesis [16]
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