Abstract
BackgroundPolo-like kinase 1 (Plk1), as a characteristic regulator in meiosis, organizes multiple biological events of cell division. Although Plk1 has been implicated in various functions in somatic cell mitotic processes, considerably less is known regarding its function during the transition from metaphase I (MI) to metaphase II (MII) stage in oocyte meiotic progression.MethodsIn this study, the possible role of Plk1 during the MI-to-MII stage transition in pig oocytes was addressed. Initially, the spatiotemporal expression and subcellular localization pattern of Plk1 were revealed in pig oocytes from MI to MII stage using indirect immunofluorescence and confocal microscopy imaging techniques combined with western blot analyses. Moreover, a highly selective Plk1 inhibitor, GSK461364, was used to determine the potential role of Plk1 during this MI-to-MII transition progression.ResultsUpon expression, Plk1 exhibited a specific dynamic intracellular localization, and co-localization of Plk1 with α-tubulin was revealed in the meiotic spindle of pig oocyte during the transition from MI to MII stage. GSK461364 treatment significantly blocked the first polar body (pbI) emission in a dose-dependent manner and resulted in a failure of meiotic maturation, with a larger percentage of the GSK461364-treated oocytes arresting in the anaphase-telophase I (ATI) stage. Further subcellular structure examination results showed that inhibition of Plk1 with GSK461364 had no visible effect on spindle assembly but caused a significantly higher proportion of the treated oocytes to have obvious defects in homologous chromosome segregation at ATI stage.ConclusionsThus, these results indicate that Plk1 plays an essential role during the meiosis I/meiosis II transition in porcine oocytes, and the regulation is associated with Plk1’s effects on homologous chromosome segregation in the ATI stage.
Highlights
Polo-like kinase 1 (Plk1), as a characteristic regulator in meiosis, organizes multiple biological events of cell division
After germinal vesicle breakdown (GVBD), metaphase I (MI) spindles are formed, and homologous chromosomes begin to segregate between the oocyte and the first polar body
Dynamic distribution of the oocyte cytoskeleton To determine the expression and subcellular localization of Plk1 in porcine oocytes during the MI-to-metaphase II (MII) transition, the cytoskeletal changes in oocytes at different stages were systematically examined by immunofluorescence techniques initially
Summary
Polo-like kinase 1 (Plk1), as a characteristic regulator in meiosis, organizes multiple biological events of cell division. Plk has been implicated in various functions in somatic cell mitotic processes, considerably less is known regarding its function during the transition from metaphase I (MI) to metaphase II (MII) stage in oocyte meiotic progression. After germinal vesicle breakdown (GVBD), metaphase I (MI) spindles are formed, and homologous chromosomes begin to segregate between the oocyte and the first polar body (pbI). These oocytes subsequently progress to the second round of meiosis, but. The majority of aneuploidies appear to be caused by missegregation of a bivalent in the first meiotic division [6, 7] During this MI to MII stage transition, any process error can lead to the failure of oocyte meiotic maturation. Much has been studied regarding the GV to MI stage in meiotic cell division [8,9,10,11], very little is known about how these events are orchestrated during the following MI to MII meiotic progression
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