OSGN-1 is a conserved flavin-containing monooxygenase required to stabilize the intercellular bridge in late cytokinesis.

Cytokinesis is the last step of cell division and is regulated by the small GTPase RhoA. RhoA activity is required for all steps of cytokinesis, including prior to abscission when daughter cells are ultimately physically separated. Like germ cells in all animals, the embryonic germline founder cell initiates cytokinesis but does not complete abscission, leaving a stable intercellular bridge between the two daughter cells.

Increases in cyclin A/Cdk activity and in PP2A-B55 inhibition by FAM122A are key mitosis-inducing events.

Entry into mitosis has been classically attributed to the activation of a cyclin B/Cdk1 amplification loop via a partial pool of this kinase becoming active at the end of G2 phase. However, how this initial pool is activated is still unknown. Here we discovered a new role of the recently identified PP2A-B55 inhibitor FAM122A in triggering mitotic entry.

Phosphoproteomic analysis identifies supervillin as an ERK3 substrate regulating cytokinesis and cell ploidy.

Extracellular signal-regulated kinase 3 (ERK3) is a poorly characterized member of the mitogen-activated protein (MAP) kinase family. Functional analysis of the ERK3 signaling pathway has been hampered by a lack of knowledge about the substrates and downstream effectors of the kinase. Here, we used large-scale quantitative phosphoproteomics and targeted gene silencing to identify direct ERK3 substrates and gain insight into its cellular functions.

Uncoupling cell division and cytokinesis during germline development in metazoans.

The canonical eukaryotic cell cycle ends with cytokinesis, which physically divides the mother cell in two and allows the cycle to resume in the newly individualized daughter cells. However, during germline development in nearly all metazoans, dividing germ cells undergo incomplete cytokinesis and germ cells stay connected by intercellular bridges which allow the exchange of cytoplasm and organelles between cells. The near ubiquity of incomplete cytokinesis in animal germ lines suggests that this is an ancient feature that is fundamental for the development and function of this tissue.

The pentacyclic triterpenoid phytosterol lupeol promotes antioxidant response in the nematode .

Plants of the Mimosa genus are studied and used for their bioactive properties. Among bioactive phytochemicals are quercetin and myricetin, which have been demonstrated to act as antioxidants in many contexts (Taheri et al. 2020; Xu et al.

PP2A-B55: substrates and regulators in the control of cellular functions.

PP2A is a major serine/threonine phosphatase class involved in the regulation of cell signaling through the removal of protein phosphorylation. This class of phosphatases is comprised of different heterotrimeric complexes displaying distinct substrate specificities. The present review will focus on one specific heterocomplex, the phosphatase PP2A-B55.

The primordial germ line is refractory to perturbations of actomyosin regulator function in L1 larvae.

Cytokinesis, the separation of daughter cells at the end of mitosis, relies on the coordinated activity of several regulators of actomyosin assembly and contractility (Green et al. 2012). These include the small GTPase RhoA (RHO-1) and its guanine-nucleotide exchange factor Ect2 (ECT-2), the scaffold protein Anillin (ANI-1), the non-muscle myosin II (NMY-2), the formin CYK-1 and the centralspindlin complex components ZEN-4 and CYK-4.

The initial expansion of the C. elegans syncytial germ line is coupled to incomplete primordial germ cell cytokinesis.

The C. elegans germline is organized as a syncytium in which each germ cell possesses an intercellular bridge that is maintained by a stable actomyosin ring and connected to a common pool of cytoplasm, termed the rachis. How germ cells undergo cytokinesis while maintaining this syncytial architecture is not completely understood.

The study of the determinants controlling Arpp19 phosphatase-inhibitory activity reveals an Arpp19/PP2A-B55 feedback loop.

Arpp19 is a potent PP2A-B55 inhibitor that regulates this phosphatase to ensure the stable phosphorylation of mitotic/meiotic substrates. At G2-M, Arpp19 is phosphorylated by the Greatwall kinase on S67. This phosphorylated Arpp19 form displays a high affinity to PP2A-B55 and a slow dephosphorylation rate, acting as a competitor of PP2A-B55 substrates.

CentTracker: a trainable, machine-learning-based tool for large-scale analyses of germline stem cell mitosis.

Investigating the complex interactions between stem cells and their native environment requires an efficient means to image them in situ. germline stem cells (GSCs) are distinctly accessible for intravital imaging; however, long-term image acquisition and analysis of dividing GSCs can be technically challenging. Here we present a systematic investigation into the technical factors impacting GSC physiology during live imaging and provide an optimized method for monitoring GSC mitosis under minimally disruptive conditions.

PP2A-B55 Holoenzyme Regulation and Cancer.

Protein phosphorylation is a post-translational modification essential for the control of the activity of most enzymes in the cell. This protein modification results from a fine-tuned balance between kinases and phosphatases. PP2A is one of the major serine/threonine phosphatases that is involved in the control of a myriad of different signaling cascades.

Cyclin A-cdk1-Dependent Phosphorylation of Bora Is the Triggering Factor Promoting Mitotic Entry.

Mitosis is induced by the activation of the cyclin B/cdk1 feedback loop that creates a bistable state. The triggering factor promoting active cyclin B/cdk1 switch has been assigned to cyclin B/cdk1 accumulation during G2. However, this complex is rapidly inactivated by Wee1/Myt1-dependent phosphorylation of cdk1 making unlikely a triggering role of this kinase in mitotic commitment.

Spindle assembly checkpoint strength is linked to cell fate in the Caenorhabditis elegans embryo.

The spindle assembly checkpoint (SAC) is a conserved mitotic regulator that preserves genome stability by monitoring kinetochore-microtubule attachments and blocking anaphase onset until chromosome biorientation is achieved. Despite its central role in maintaining mitotic fidelity, the ability of the SAC to delay mitotic exit in the presence of kinetochore-microtubule attachment defects (SAC "strength") appears to vary widely. How different cellular aspects drive this variation remains largely unknown.

Actomyosin contractility regulators stabilize the cytoplasmic bridge between the two primordial germ cells during embryogenesis.

Stable cytoplasmic bridges arise from failed cytokinesis, the last step of cell division, and a key feature of syncytial architectures in the germline of most metazoans. Whereas the germline is syncytial, its formation remains poorly understood. We found that the germline precursor blastomere, , fails cytokinesis, leaving a stable cytoplasmic bridge between the daughter cells, Z and Z Depletion of several regulators of actomyosin contractility resulted in a regression of the membrane partition between Z and Z, indicating that they required to stabilize the cytoplasmic bridge.

DAF-18/PTEN signals through AAK-1/AMPK to inhibit MPK-1/MAPK in feedback control of germline stem cell proliferation.

Under replete growth conditions, abundant nutrient uptake leads to the systemic activation of insulin/IGF-1 signalling (IIS) and the promotion of stem cell growth/proliferation. Activated IIS can stimulate the ERK/MAPK pathway, the activation of which also supports optimal stem cell proliferation in various systems. Stem cell proliferation rates can further be locally refined to meet the resident tissue's need for differentiated progeny.

The master Greatwall kinase, a critical regulator of mitosis and meiosis.

Entry into mitosis requires the coordinated activation of various protein kinases and phosphatases that together activate sequential signaling pathways allowing entry, progression and exit of mitosis. The limiting step is thought to be the activation of the mitotic Cdk1-cyclin B kinase. However, this model has recently evolved with new data showing that in addition to the Cdk1-cyclin B complex, Greatwall (Gwl) kinase is also required to enter into and maintain mitosis.

Bigger Isn't Always Better: Cell Size and the Spindle Assembly Checkpoint.

Variation in the activity of the spindle assembly checkpoint has been observed in different cell types, yet the reason for this variability remains poorly understood. Reporting in Developmental Cell, Galli and Morgan (2016) show that checkpoint activity increases during development as cell size, and the cytoplasm-to-kinetochore ratio, decreases.

DAF-18/PTEN locally antagonizes insulin signalling to couple germline stem cell proliferation to oocyte needs in C. elegans.

During development, stem cell populations rapidly proliferate to populate the expanding tissues and organs. During this phase, nutrient status, by systemically affecting insulin/IGF-1 signalling, largely dictates stem cell proliferation rates. In adults, however, differentiated stem cell progeny requirements are generally reduced and vary according to the spatiotemporal needs of each tissue.

Investigating the regulation of stem and progenitor cell mitotic progression by in situ imaging.

Genome stability relies upon efficacious chromosome congression and regulation by the spindle assembly checkpoint (SAC). The study of these fundamental mitotic processes in adult stem and progenitor cells has been limited by the technical challenge of imaging mitosis in these cells in situ. Notably, how broader physiological changes, such as dietary intake or age, affect mitotic progression in stem and/or progenitor cells is largely unknown.

CDK-1 and two B-type cyclins promote PAR-6 stabilization during polarization of the early C. elegans embryo.

In the C. elegans embryo, formation of an antero-posterior axis of polarity relies on signaling by the conserved PAR proteins, which localize asymmetrically in two mutually exclusive groups at the embryonic cortex. Depletion of any PAR protein causes a loss of polarity and embryonic lethality.

C. elegans Anillin proteins regulate intercellular bridge stability and germline syncytial organization.

Cytokinesis generally produces two separate daughter cells, but in some tissues daughter nuclei remain connected to a shared cytoplasm, or syncytium, through incomplete cytokinesis. How syncytia form remains poorly understood. We studied syncytial formation in the Caenorhabditis elegans germline, in which germ cells connect to a shared cytoplasm core (the rachis) via intercellular bridges.