Casein kinase 2 modulates the spindle assembly checkpoint to orchestrate porcine oocyte meiotic progression

Xiayan Shiyang,Zhaokang Cui,Yilong Miao,Bo Xiong,Yu Zhang,Yajuan Lu,Changyin Zhou

doi:10.1186/s40104-020-00438-1

Abstract

BackgroundCK2 (casein kinase 2) is a serine/threonine-selective protein kinase that has been involved in a variety of cellular processes such as DNA repair, cell cycle control and circadian rhythm regulation. However, its functional roles in oocyte meiosis have not been fully determined.ResultsWe report that CK2 is essential for porcine oocyte meiotic maturation by regulating spindle assembly checkpoint (SAC). Immunostaining and immunoblotting analysis showed that CK2 was constantly expressed and located on the chromosomes during the entire oocyte meiotic maturation. Inhibition of CK2 activity by its selective inhibitor CX-4945 impaired the first polar body extrusion and arrested oocytes at M I stage, accompanied by the presence of BubR1 at kinetochores, indicative of activated SAC. In addition, we found that spindle/chromosome structure was disrupted in CK2-inhibited oocytes due to the weakened microtubule stability, which is a major cause resulting in the activation of SAC. Last, we found that the level DNA damage as assessed by γH2A.X staining was considerably elevated when CK2 was inhibited, suggesting that DNA damage might be another critical factor leading to the SAC activation and meiotic failure of oocytes.ConclusionsOur findings demonstrate that CK2 promotes the porcine oocyte maturation by ensuring normal spindle assembly and DNA damage repair.

Highlights

Casein kinase 2 (CK2) is an ubiquitously expressed and highly conserved serine/threonine protein kinase that forms a tetramer containing two catalytic (α and/or α) subunits and two regulatory β subunits [1]
Collection and in vitro maturation of Cumulus-oocyte complexes (COCs) COCs with a compact cumulus mass were collected from medium-sized follicles of porcine ovaries using the disposable syringe, and transferred to the in vitro maturation medium (improved TCM-199 supplemented with 0.5 μg/mL Follicle-stimulating hormone (FSH), 0.5 μg/mL Luteinizing hormone (LH), 0.57 mmol/L cysteine (Sigma), 10 ng/mL Epidermal growth factor (EGF), 50 μg/mL streptomycin and 75 μg/mL penicillin)
CK2 localizes to chromosomes in porcine oocyte meiosis To examine the roles of CK2 during porcine oocyte meiotic maturation, we firstly observed its subcellular localization and protein expression patterns in different stages of meiotic maturation

Summary

Introduction

CK2 (casein kinase 2) is an ubiquitously expressed and highly conserved serine/threonine protein kinase that forms a tetramer containing two catalytic (α and/or α) subunits and two regulatory β subunits [1]. According to the specific functions, its catalytic and regulatory subunits may form ααβ, α2β2, α2β2, or unassembled molecules [2, 3]. It has been reported to CK2 participates in cell cycle regulation [5], cell proliferation, DNA damage repair [6, 7], apoptosis [8, 9], and other cellular processes [4, 10, 11]. CK2 (casein kinase 2) is a serine/threonine-selective protein kinase that has been involved in a variety of cellular processes such as DNA repair, cell cycle control and circadian rhythm regulation. Its functional roles in oocyte meiosis have not been fully determined

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