Oogenesis, Oocyte maturation
, First polar body extrusion
Comment
A Casein Kinase 1 Prevents Expulsion of the Oocyte Meiotic Spindle into a Polar Body by Regulating Cortical Contractility. Flynn JR et al. (2017) During female meiosis, haploid eggs are generated from diploid oocytes. This reduction in chromosome number occurs through two highly asymmetric cell divisions resulting in one large egg and two small polar bodies. Unlike mitosis, where an actomyosin contractile ring forms between the sets of segregating chromosomes, the meiotic contractile ring forms on the cortex adjacent to one spindle pole, then ingresses down the length of the spindle to position itself at the exact midpoint between the two sets of segregating chromosomes. Depletion of casein kinase 1 gamma (CSNK-1) in C. elegans led to the formation of large polar bodies that contain all maternal DNA because the contractile ring ingressed past the spindle midpoint. Depletion of CSNK-1 also resulted in the formation of deep membrane invaginations during meiosis, suggesting an effect on cortical myosin. Both myosin and anillin assemble into dynamic rho-dependent cortical patches that rapidly disassemble in wild-type embryos. CSNK-1 was required for disassembly of both myosin patches and anillin patches. Disassembly of anillin patches was myosin independent suggesting that CSNK-1 prevents expulsion of the entire meiotic spindle into a polar body by negatively regulating the rho pathway rather than through direct inhibition of myosin.//////////////////
Casein Kinase 1 Alpha Regulates Chromosome Congression and Separation during Mouse Oocyte Meiotic Maturation and Early Embryo Development. Wang L et al. Casein kinase I alpha (CK1a) is a member of serine/threonine protein kinase, generally present in all eukaryotes. In mammals, CK1a regulates the transition from interphase to metaphase in mitosis. However, little is known about its role in meiosis. Here we examined Ck1a mRNA and protein expression, as well as its subcellular localization in mouse oocytes from germinal vesicle to the late 1-cell stage. Our results showed that the expression level of CK1a was increased in metaphase. Immunostaining results showed that CK1a colocalized with condensed chromosomes during oocyte meiotic maturation and early embryo development. We used the loss-of-function approach by employing CK1a specific morpholino injection to block the function of CK1a. This functional blocking leads to failure of polar body 1 (PB1) extrusion, chromosome misalignment and MII plate incrassation. We further found that D4476, a specific and efficient CK1 inhibitor, decreased the rate of PB1 extrusion. Moreover, D4476 resulted in giant polar body extrusion, oocyte pro-MI arrest, chromosome congression failure and impairment of embryo developmental potential. In addition, we employed pyrvinium pamoate (PP), an allosteric activator of CK1a, to enhance CK1a activity in oocytes. Supplementation of PP induced oocyte meiotic maturation failure, severe congression abnormalities and misalignment of chromosomes. Taken together, our study for the first time demonstrates that CK1a is required for chromosome alignment and segregation during oocyte meiotic maturation and early embryo development.
Expression regulated by
Comment
Ovarian localization
Oocyte
Comment
Casein kinase 1 (α, δ and ε) localize at the spindle poles, but may not be essential for mammalian oocyte meiotic progression. Qi ST et al. (2015) CK1 (casein kinase 1) is a family of serine/threonine protein kinase that is ubiquitously expressed in eukaryotic organism. CK1 members are involved in the regulation of many cellular processes. Particularly, CK1 was reported to phosphorylate Rec8 subunits of cohesin complex and regulate chromosome segregation in meiosis in budding yeast and fission yeast (1-3) . Here we investigated the expression, subcellular localization and potential functions of CK1α, CK1δ and CK1ε during mouse oocyte meiotic maturation. We found that CK1α, CK1δ and CK1ε all concentrated at the spindle poles and co-localized with γ-tubulin in oocytes at both metaphase I (MI) and metaphase II (MII) stages. However, depletion of CK1 by RNAi or overexpression of wild type or kinase-dead CK1 showed no effects on either spindle organization or chromosome segregation during oocyte meiotic maturation. Thus, CK1 is not the kinase that phosphorylates Rec8 cohesin in mammalian oocytes, and CK1 may not be essential for spindle organization and meiotic progression although they localize at spindle poles.//////////////////Molecular cloning and expression of cDNA coding for four spliced isoforms of casein kinase Ialpha in goldfish oocytes Horiguchi R, et al .
Casein kinase I (CKI) is a member of the serine/threonine protein kinases and located in a separate group within the superfamily of eukaryotic protein kinases. CKI isoforms regulate several checkpoints of the cell cycle and meiosis. In higher eukaryotes, CKIalpha has four isoforms produced through the alternative splicing of two short inserts. Here, we report the cloning, sequencing and expression of four alternatively spliced isoforms of CKIalpha from goldfish ovary. The cloned cDNAs were 2099-3002-bp long and classified as CKIalpha, CKIalphaS, CKIalphaL and CKIalphaLS. It was revealed that two major (3.0 and 2.0 kb) messages were strongly expressed in the ovary. Four isoforms are expressed in previtellogenic to vitellogenic oocytes. In the huge nucleus of the oocyte, referred to as the germinal vesicle, CKIalphaS is dominant and CKIalphaL is expressed at a detectable level. Immunoblot analysis revealed that CKIalpha and CKIalphaS are major products in both immature and mature oocytes. These two isoforms were expressed in a tissue-dependent manner.