Characterization of polo‐like kinase‐1 in rat oocytes and early embryos implies its functional roles in the regulation of meiotic maturation, fertilization, and cleavage

Abstract

Polo-like kinase 1 (Plk1) is a family of serine/threonine protein kinases that play important regulatory roles during mitotic cell cycle progression. In this study, Plk1 expression, subcellular localization, and possible functions during rat oocyte meiotic maturation, fertilization, and embryonic cleavages were studied by using RT-PCR, Western blot, confocal microscopy, drug-treatments, and antibody microinjection. Both the mRNA and protein of this kinase were detected in rat maturing oocytes and developing embryos. Confocal microscopy revealed that Plk1 distributed abundantly in the nucleus at the germinal vesicle (GV) stage, was associated with spindle poles during the formation of M-phase spindle, and was translocated to the spindle mid-zone at anaphase. In fertilized eggs, Plk1 was strongly stained in the cytoplasm between the apposing male and female pronuclei, from where microtubules radiated. Throughout cytokinesis, Plk1 was localized to the division plane, both during oocyte meiosis and embryonic mitosis. The specific subcellular distribution of Plk1 was distorted after disrupting the M-phase spindle, while additional aggregation dots could be induced in the cytoplasm by taxol, suggesting its intimate association with active microtubule assembly. Plk1 antibody microinjection delayed the meiotic resumption and blocked the emission of polar bodies. In conclusion, Plk1 may be a multifunctional kinase that plays pivotal regulatory roles in microtubule assembly during rat oocyte meiotic maturation, fertilization, and early embryonic mitosis.

Developmental Regulation and In Vitro Culture Effects on Expression of DNA Repair and Cell Cycle Checkpoint Control Genes in Rhesus Monkey Oocytes and Embryos1

“…The polo-like kinases (PLK1 and PLK3) provide important regulation of the G2/ M phase transition [55]. PLK1 is required for correct spindle function during mitosis and meiosis [56][57][58][59]. Both PLK mRNAs were expressed as maternal transcripts and continued to be expressed throughout development.…”

Involvement of Polo-like kinase 1 in MEK1/2-regulated spindle formation during mouse oocyte meiosis

“…[20][21][22] In meiosis, our earlier findings have indicated that Plk1 plays pivotal roles in regulating the microtubule assembly and spindle formation in mouse, rat and porcine oocytes. [23][24][25] Since both MEK1/2 and Plk1 are shown to localize to the spindle poles and play an essential role in spindle assembly during mouse oocyte meiotic maturation, we hypothesized that Plk1 might be a molecule interacting with MEK1/2 in the regulation of spindle formation.…”

ERK1/2 Activities Are Dispensable for Oocyte Growth but Are Required for Meiotic Maturation and Pronuclear Formation in Mouse

“…The result indicated that ERK1/2 activities were required for MII arrest, but its loss was not sufficient for a full parthenogenetic activation. It has been previously reported that a large portion of in vitro cultured rat oocytes did not arrest at MII and developed to MIII (Fan et al, 2003b). Therefore, it will be interesting to check if ERK1/2 were inactivated in these rat oocytes.…”