Characterization of Polo-like Kinase 1 during Meiotic Maturation of the Mouse Oocyte

Abstract

We have characterized plk1 in mouse oocytes during meiotic maturation and after parthenogenetic activation until entry into the first mitotic division. Plk1 protein expression remains unchanged during maturation. However, two different isoforms can be identified by SDS-PAGE. A fast migrating form, present in the germinal vesicle, seems characteristic of interphase. A slower form appears as early as 30 min before germinal vesicle breakdown (GVBD), is maximal at GVBD, and is maintained throughout meiotic maturation. This form gradually disappears after exit from meiosis. The slow form corresponds to a phosphorylation since it disappears after alkaline phosphatase treatment. Plk1 activation, therefore, takes place before GVBD and MAPK activation since plk1 kinase activity correlates with its slow migrating phosphorylated form. However, plk1 phosphorylation is inhibited after treatment with two specific p34(cdc2) inhibitors, roscovitine and butyrolactone, suggesting plk1 involvement in the MPF autoamplification loop. During meiosis plk1 undergoes a cellular redistribution consistent with its putative targets. At the germinal vesicle stage, plk1 is found diffusely distributed in the cytoplasm and enriched in the nucleus and during prometaphase is localized to the spindle poles. At anaphase it relocates to the equatorial plate and is restricted to the postmitotic bridge at telophase. After parthenogenetic activation, plk1 becomes dephosphorylated and its activity drops progressively. Upon entry into the first mitotic M-phase at nuclear envelope breakdown plk1 is phosphorylated and there is an increase in its kinase activity. At the two-cell stage, the fast migrating form with weak kinase activity is present. In this work we show that plk1 is present in mouse oocytes during meiotic maturation and the first mitotic division. The variation of plk1 activity and subcellular localization during this period suggest its implication in the organization and progression of M-phase.

Involvement of Polo-like Kinase 1 (Plk1) in Mitotic Arrest by Inhibition of Mitogen-activated Protein Kinase-Extracellular Signal-regulated Kinase-Ribosomal S6 Kinase 1 (MEK-ERK-RSK1) Cascade

“…According to previous research, the protein expression levels of Plk1 peak during M phase in somatic cells but remain constant during the meiotic and early embryonic cell cycles (42)(43)(44)(45). Knockdown of Plk1 activity in Artemia using doublestranded RNA injections showed that phosphorylation of RSK1 increased gradually from the 1st day to the 3rd day after the oocytes entered the ovisac (uterus) in line with embryo development.…”

Error-prone mammalian female meiosis from silencing the spindle assembly checkpoint without normal interkinetochore tension

“…Our observations of aberrant spindle poles in the Δ22 NuMA mutant oocytes, together with the known function of NuMA at spindle poles in mitotic cells (reviewed in 21), prompted us to analyze the nature of these meiotic defects more closely. To do this, we followed behavior of MTOCs by immunofluorescence analysis of pericentrin, a major MTOC component, and time-lapse microscopic analysis of Venus-tagged Polo kinase 1, which has previously been shown to associate with MTOCs in meiosis (22). Analysis of both time-lapse microscopy and fixed samples clearly showed that the kinetics of MTOCs sorting to the spindle poles were similar in control and mutant oocytes ( Fig.…”

Mitochondrial functions on oocytes and preimplantation embryos

“…Chromosomal aneuploidies often occur during the first meiotic division (Robertson, 1998) and aberrant activity of motor proteins and kinetochores-related kinases may contribute to these chromosomal aneuploidies in aged female (Yin et al, 1998). Polo-like kinases (Plks) are key cytokinesis-related protein kinases in oocytes during meiotic maturation for spindle formation and chromosome separation (Pahlavan et al, 2000), and their activities are correlated with protein phosphorylation, which depends on the endogenous substrates and ATP as phosphate donor (Golsteyn et al, 1994).…”