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The cell cycle in oocytes generally arrests at a particular meiotic stage to await fertilization. This arrest occurs at metaphase of meiosis II (meta-II) in frog and mouse, and at G1 phase after completion of meiosis II in starfish. Despite this difference in the arrest phase, both arrests depend on the same Mos-MAPK (mitogen-activated protein kinase) pathway, indicating that the difference relies on particular downstream effectors. Immediately downstream of MAPK, Rsk (p90 ribosomal S6 kinase, p90Rsk) is required for the frog meta-II arrest. However, the mouse meta-II arrest challenges this requirement, and no downstream effector has been identified in the starfish G1 arrest. To investigate the downstream effector of MAPK in the starfish G1 arrest, we used a neutralizing antibody against Rsk and a constitutively active form of Rsk. Rsk was activated downstream of the Mos-MAPK pathway during meiosis. In G1 eggs, inhibition of Rsk activity released the arrest and initiated DNA replication without fertilization. Conversely, maintenance of Rsk activity prevented DNA replication following fertilization. In early embryos, injection of Mos activated the MAPK-Rsk pathway, resulting in G1 arrest. Moreover, inhibition of Rsk activity during meiosis I led to parthenogenetic activation without meiosis II. We conclude that immediately downstream of MAPK, Rsk is necessary and sufficient for the starfish G1 arrest. Although CSF (cytostatic factor) was originally defined for meta-II arrest in frog eggs, we propose to distinguish 'G1-CSF' for starfish from `meta-II-CSF' for frog and mouse. The present study thus reveals a novel role of Rsk for G1-CSF. [ABSTRACT FROM AUTHOR]

Establishing the correct kinetochore-microtubule attachment is crucial for faithful chromosome segregation. The kinetochore has various regulatory mechanisms for establishing correct bipolar attachment. However, how the regulations are coupled is not fully understood. Here, we demonstrate a regulatory loop between the kinetochore protein CENP-C and Aurora B kinase, which is critical for the error correction of kinetochore-microtubule attachment. This regulatory loop is mediated through the binding of CENP-C to the outer kinetochore Mis12 complex (Mis12C). Although the Mis12C-binding region of CENP-C is dispensable for mouse development and proliferation in human RPE-1 cells, those cells lacking this region display increased mitotic defects. The CENP-C-Mis12C interaction facilitates the centromeric recruitment of Aurora B and the mitotic error correction in human cells. Given that Aurora B reinforces the CENP-C-Mis12C interaction, our findings reveal a positive regulatory loop between Aurora B recruitment and the CENP-C-Mis12C interaction, which ensures chromosome biorientation for accurate chromosome segregation., (© 2024 Kong et al.)

Accurate chromosome segregation during mitosis requires the kinetochore, a large protein complex, which makes a linkage between chromosomes and spindle microtubes. An essential kinetochore component, CENP-C, is phosphorylated by Cyclin-B-Cyclin dependent kinase 1 (CDK1) that is a master kinase for mitotic progression, promoting proper kinetochore assembly during mitosis. Here, we describe an in vitro CDK1 kinase assay to detect CENP-C phosphorylation using Phos-tag SDS-PAGE without radiolabeled ATP. Our protocol has advantages in ease and safety over conventional phosphorylation assays using [γ- 32 P]-ATP, which has potential hazards despite their better sensitivity. The protocol described here can be applicable to other kinases and be also useful for analysis of phospho-sites in substrates in vitro ., Competing Interests: Competing interestsThe authors declare no competing interests., (Copyright © 2021 The Authors; exclusive licensee Bio-protocol LLC.)

Background: Residual kidney function (RKF) is an important factor influencing both technique and patient survival in peritoneal dialysis (PD) patients. B-type natriuretic peptide (BNP) is considered a marker of cardio-renal syndrome. The relationship between BNP and RKF in PD patients remains unclear., Methods: We conducted a prospective study of 89 patients who had started and continued PD for 6 months or more in Kyushu University Hospital between June 2006 and September 2015. Participants were divided into low BNP (≤ 102.1 ng/L) and high BNP (> 102.1 ng/L) groups according to median plasma BNP level at PD initiation. The primary outcome was RKF loss, defined as 24-hour urine volume less than 100 mL. We estimated the association between BNP and RKF loss using a Kaplan-Meier method and Cox proportional hazards model and compared the rate of RKF decline between the 2 groups. To evaluate the consistency of the association, we performed subgroup analysis stratified by baseline characteristics., Results: During the median follow-up of 30 months, 30 patients lost RKF. Participants in the high BNP group had a 5.87-fold increased risk for RKF loss compared with the low BNP group after adjustment for clinical and cardiac parameters. A high plasma BNP level was more clearly associated with RKF loss in younger participants compared with older participants in subgroup analysis., Conclusions: B-type natriuretic peptide may be a useful risk marker for RKF loss in PD patients. The clinical importance of plasma BNP level as a marker of RKF loss might be affected by age., (Copyright © 2019 International Society for Peritoneal Dialysis.)

♦ BACKGROUND: Outflow obstruction, a common complication in patients with peritoneal dialysis (PD), usually results in unnecessary catheter removal or replacement. This study describes a modified simple method of anchoring a PD catheter on the anterior peritoneal wall without using a laparoscopic system (peritoneal wall anchor technique, PWAT). ♦ METHODS: We performed a retrospective cohort study of consecutive PD catheter insertions, and compared the catheter survival rate between the traditional method and the modified simple PWAT. The traditional method was used in 54 cases and the modified simple PWAT was used in 17 cases. The primary endpoint was the occurrence of surgical catheter repair because of outflow obstruction by day 365. The secondary endpoint was the occurrence of catheter migration with obstruction requiring any interventions, including the alpha-replacement method by day 365. Catheter survival was analyzed by Kaplan-Meier survival curves. ♦ RESULTS: Migration-free catheter survival was significantly (p = 0.02) higher in the PWAT group (100%, 17/17) than in the traditional group (72.2%, 39/54). Catheter survival without surgical repair or cessation of PD was also significantly (p = 0.04) higher in the PWAT group (100%, 17/17) than in the traditional group (77.8%, 42/54). Similarly, migration-free and surgery-free catheter survival rates in cases with a straight-type catheter in the PWAT group were significantly higher than those in cases with a straight-type catheter in the traditional group. ♦ CONCLUSIONS: Our results suggest that the modified simple PWAT provides a better catheter survival rate than the traditional method by preventing catheter migration with obstruction in PD., (Copyright © 2017 International Society for Peritoneal Dialysis.)

Antibodies are widely utilized in cell and molecule biology for immunoblots, immunostaining, immunoprecipitation, immunoaffinity purification, and immunoassay. Some antibodies can be used for in vivo inhibition experiments. These antibodies bind to their target molecules and neutralize their functions, providing functional information in the study of their biological role. Here, we describe our methods for obtaining inhibitory antibodies against desired proteins. We then describe in the starfish oocyte system how to inhibit a target protein, even in the nucleus, by injection of antibody into the cytoplasm, and how to evaluate antibody inhibition of cell cycle regulators in small numbers of oocytes.