Fission yeast Dis1 is an unconventional TOG/XMAP215 that induces microtubule catastrophe to drive chromosome pulling.

The shortening of microtubules attached to kinetochores is the driving force of chromosome movement during cell division. Specific kinesins are believed to shorten microtubules but are dispensable for viability in yeast, implying the existence of additional factors responsible for microtubule shortening. Here, we demonstrate that Dis1, a TOG/XMAP215 ortholog in fission yeast, promotes microtubule shortening to carry chromosomes. Although TOG/XMAP215 orthologs are generally accepted as microtubule polymerases, Dis1 promoted microtubule catastrophe in vitro and in vivo. Notably, microtubule catastrophe was promoted when the tip was attached to kinetochores, as they steadily anchored Dis1 at the kinetochore-microtubule interface. Engineered Dis1 oligomers artificially tethered at a chromosome arm region induced the shortening of microtubules in contact, frequently pulling the chromosome arm towards spindle poles. This effect was not brought by oligomerised Alp14. Thus, unlike Alp14 and other TOG/XMAP215 orthologs, Dis1 plays an unconventional role in promoting microtubule catastrophe, thereby driving chromosome movement.

Time-lapse single-cell transcriptomics reveals modulation of histone H3 for dormancy breaking in fission yeast.

How quiescent cells break dormancy is a key issue in eukaryotic cells including cancer. Fungal spores, for example, remain quiescent for long periods until nourished, although the mechanisms by which dormancy is broken remain enigmatic. Transcriptome analysis could provide a clue, but methods to synchronously germinate large numbers of spores are lacking, and thus it remains a challenge to analyse gene expression upon germination. Hence, we develop methods to assemble transcriptomes from individual, asynchronous spore cells of fission yeast undergoing germination to assess transcriptomic changes over time. The virtual time-lapse analyses highlights one of three copies of histone H3 genes whose transcription fluctuates during the initial stage of germination. Disruption of this temporal fluctuation causes defects in spore germination despite no visible defects in other stages of the life cycle. We conclude that modulation of histone H3 expression is a crucial 'wake-up' trigger at dormancy breaking.

Functional Dissection of Mitosis Using Immortalized Fibroblasts from the Indian Muntjac, a Placental Mammal with Only Three Chromosomes.

During cell division in eukaryotes a microtubule-based network undergoes drastic changes and remodeling to assemble a mitotic spindle competent to segregate chromosomes. Several model systems have been widely used to dissect the molecular and structural mechanisms behind mitotic spindle assembly and function. These include budding and fission yeasts, which are ideal for genetic and molecular approaches, but show limitations in high-resolution live-cell imaging, while being evolutionarily distant from humans. On the other hand, systems that were historically used for their exceptional properties for live-cell imaging of mitosis (e.g., newt lung cells and Haemanthus endosperm cells) lack the necessary genomic tools for molecular studies. In a CRISPR-Cas9 era, human cultured cells have conquered the privilege to be positioned among the most powerful genetically manipulatable systems, but their high chromosome number remains a significant bottleneck for the molecular dissection of mitosis in mammals. We believe that we can significantly broaden this scenario by establishing a unique placental mammal model system that combines the powerful genetic tools and low chromosome number of fission yeast and Drosophila melanogaster, with the exceptional cytological features of a rat kangaroo cell. This system is based on hTERT-immortalized fibroblasts from a female Indian muntjac, a placental mammal with the lowest known chromosome number (n = 3). Here we describe a series of methodologies established in our laboratory for the study of mitosis in Indian muntjac. These include standard techniques such as immunofluorescence, western blotting, and FISH, but also several state-of-the-art methodologies, including live-cell imaging, cell confinement, RNAi, super-resolution STED microscopy, and laser microsurgery.

CLASP2 binding to curved microtubule tips promotes flux and stabilizes kinetochore attachments.

CLASPs are conserved microtubule plus-end-tracking proteins that suppress microtubule catastrophes and independently localize to kinetochores during mitosis. Thus, CLASPs are ideally positioned to regulate kinetochore-microtubule dynamics required for chromosome segregation fidelity, but the underlying mechanism remains unknown. Here, we found that human CLASP2 exists predominantly as a monomer in solution, but it can self-associate through its C-terminal kinetochore-binding domain. Kinetochore localization was independent of self-association, and driving monomeric CLASP2 to kinetochores fully rescued normal kinetochore-microtubule dynamics, while partially sustaining mitosis. CLASP2 kinetochore localization, recognition of growing microtubule plus-ends through EB-protein interaction, and the ability to associate with curved microtubule protofilaments through TOG2 and TOG3 domains independently sustained normal spindle length, timely spindle assembly checkpoint satisfaction, chromosome congression, and faithful segregation. Measurements of kinetochore-microtubule half-life and poleward flux revealed that CLASP2 regulates kinetochore-microtubule dynamics by integrating distinctive microtubule-binding properties at the kinetochore-microtubule interface. We propose that kinetochore CLASP2 suppresses microtubule depolymerization and detachment by binding to curved protofilaments at microtubule plus-ends.

Spatiotemporal Regulation of Nuclear Transport Machinery and Microtubule Organization.

Spindle microtubules capture and segregate chromosomes and, therefore, their assembly is an essential event in mitosis. To carry out their mission, many key players for microtubule formation need to be strictly orchestrated. Particularly, proteins that assemble the spindle need to be translocated at appropriate sites during mitosis. A small GTPase (hydrolase enzyme of guanosine triphosphate), Ran, controls this translocation. Ran plays many roles in many cellular events: nucleocytoplasmic shuttling through the nuclear envelope, assembly of the mitotic spindle, and reorganization of the nuclear envelope at the mitotic exit. Although these events are seemingly distinct, recent studies demonstrate that the mechanisms underlying these phenomena are substantially the same as explained by molecular interplay of the master regulator Ran, the transport factor importin, and its cargo proteins. Our review focuses on how the transport machinery regulates mitotic progression of cells. We summarize translocation mechanisms governed by Ran and its regulatory proteins, and particularly focus on Ran-GTP targets in fission yeast that promote spindle formation. We also discuss the coordination of the spatial and temporal regulation of proteins from the viewpoint of transport machinery. We propose that the transport machinery is an essential key that couples the spatial and temporal events in cells.

Impulsive force on the head during performance of typical ukemi techniques following different judo throws.

In this study, eight judo athletes who are major candidates for the Japan national team were recruited as participants. Kinematic analysis of exemplary ukemi techniques was carried out using two throws, o-soto-gari, a throw linked to frequent injury, and o-uchi-gari. The aim of this study was to kinematically quantify the timing patterns of exemplary ukemi techniques and to obtain kinematic information of the head, in a sequence of ukemi from the onset of the throw to the completion of ukemi. The results indicated that the vertical velocity with which the uke's head decelerated was reduced by increasing the body surface exposed to the collision with the tatami and by increasing the elapsed time. In particular, overall upper limb contact with the tatami is greatly associated with deceleration. In o-soto-gari, the impulsive force on the faller's head as the head reached the lowest point was 204.82 ± 19.95 kg m · s(-2) while in o-uchi-gari it was 118.46 ± 63.62 kg m · s(-2), z = -1.75, P = 0.08, and it did present a large-sized effect with r = 0.78. These findings indicate that the exemplary o-soto-gari as compared to o-uchi-gari is the technique that causes more significant damage to the uke's head.

Targeting Alp7/TACC to the spindle pole body is essential for mitotic spindle assembly in fission yeast.

The conserved TACC protein family localises to the centrosome (the spindle pole body, SPB in fungi) and mitotic spindles, thereby playing a crucial role in bipolar spindle assembly. However, it remains elusive how TACC proteins are recruited to the centrosome/SPB. Here, using fission yeast Alp7/TACC, we have determined clustered five amino acid residues within the TACC domain required for SPB localisation. Critically, these sequences are essential for the functions of Alp7, including proper spindle formation and mitotic progression. Moreover, we have identified pericentrin-like Pcp1 as a loading factor to the mitotic SPB, although Pcp1 is not a sole platform.

CDK-dependent phosphorylation of Alp7-Alp14 (TACC-TOG) promotes its nuclear accumulation and spindle microtubule assembly.

As cells transition from interphase to mitosis, the microtubule cytoskeleton is reorganized to form the mitotic spindle. In the closed mitosis of fission yeast, a microtubule-associated protein complex, Alp7-Alp14 (transforming acidic coiled-coil-tumor overexpressed gene), enters the nucleus upon mitotic entry and promotes spindle formation. However, how the complex is controlled to accumulate in the nucleus only during mitosis remains elusive. Here we demonstrate that Alp7-Alp14 is excluded from the nucleus during interphase using the nuclear export signal in Alp14 but is accumulated in the nucleus during mitosis through phosphorylation of Alp7 by the cyclin-dependent kinase (CDK). Five phosphorylation sites reside around the nuclear localization signal of Alp7, and the phosphodeficient alp7-5A mutant fails to accumulate in the nucleus during mitosis and exhibits partial spindle defects. Thus our results reveal one way that CDK regulates spindle assembly at mitotic entry: CDK phosphorylates the Alp7-Alp14 complex to localize it to the nucleus.

Microtubules and Alp7-Alp14 (TACC-TOG) reposition chromosomes before meiotic segregation.

Tethering kinetochores at spindle poles facilitates their efficient capture and segregation by microtubules at mitotic onset in yeast. During meiotic prophase of fission yeast, however, kinetochores are detached from the poles, which facilitates meiotic recombination but may cause a risk of chromosome mis-segregation during meiosis. How cells circumvent this dilemma remains unclear. Here we show that an extensive microtubule array assembles from the poles at meiosis I onset and retrieves scattered kinetochores towards the poles to prevent chromosome drift. Moreover, the microtubule-associated protein complex Alp7-Alp14 (the fission yeast orthologues of mammalian TACC-TOG) is phosphorylated by Polo kinase, which promotes its meiosis-specific association to the outer kinetochore complex Nuf2-Ndc80 of scattered kinetochores, thereby assisting in capturing remote kinetochores. Although TOG was recently characterized as a microtubule polymerase, Dis1 (the other TOG orthologue in fission yeast), together with the Dam1 complex, plays a role in microtubule shortening to pull kinetochores polewards. Thus, microtubules and their binding proteins uniquely reconstitute chromosome configuration during meiosis.

Nucleocytoplasmic transport of Alp7/TACC organizes spatiotemporal microtubule formation in fission yeast.

Ran GTPase activates several target molecules to induce microtubule formation around the chromosomes and centrosomes. In fission yeast, in which the nuclear envelope does not break down during mitosis, Ran targets the centrosomal transforming acidic coiled-coil (TACC) protein Alp7 for spindle formation. Alp7 accumulates in the nucleus only during mitosis, although its underlying mechanism remains elusive. Here, we investigate the behaviour of Alp7 and its binding partner, Alp14/TOG, throughout the cell cycle. Interestingly, Alp7 enters the nucleus during interphase but is subsequently exported to the cytoplasm by the Exportin-dependent nuclear export machinery. The continuous nuclear export of Alp7 during interphase is essential for maintaining the array-like cytoplasmic microtubule structure. The mitosis-specific nuclear accumulation of Alp7 seems to be under the control of cyclin-dependent kinase (CDK). These results indicate that the spatiotemporal regulation of microtubule formation is established by the Alp7/TACC-Alp14/TOG complex through the coordinated interplay of Ran and CDK.

Dermatan sulfate in the synovial fluid of patients with knee osteoarthritis.

Biochemical factors play an important role in osteoarthritis (OA) pathogenesis. The purpose of this study is to clarify whether the dermatan sulfate (DS) levels in the synovial fluid of patients with knee OA are related to residual cartilage. Synovial fluid was obtained from 51 OA patients. Knee radiographs were evaluated with the Kellgren-Lawrence (K/L) grading scale. The levels of the following disaccharides were measured by high-performance liquid chromatography (HPLC): DS (DSDeltaDi4S), chondroitin 6-sulfate (CSDeltaDi6S), and chondroitin 4-sulfate (CSDeltaDi4S). The concentration of cartilage oligomeric matrix protein (COMP) was measured by a sandwich ELISA. The levels of DSDeltaDi4S in Grades 0 and I OA were significantly higher than levels in Grade II (P = 0.0458), Grade III (P < 0.0001) and Grade IV (P < 0.0001), and we found strong relationships between the levels of DSDeltaDi4S and those of CSDeltaDi6S (P < 0.0001, r = 0.705), CSDeltaDi4S (P < 0.0001, r = 0.750), and COMP (P < 0.0001, r = 0.699). We conclude that the presence of DSDeltaDi4S reflects proteoglycan metabolism in the residual articular cartilage of OA patients. This suggests that metabolism of the small leucine-rich repeat proteoglycans decorin and biglycan, which contain chains of DSDeltaDi4S, is similar to that of aggrecan.

Cartilage oligomeric matrix protein in serum and synovial fluid of rheumatoid arthritis: potential use as a marker for joint cartilage damage.

This study examined the serum and synovial fluid concentrations of cartilage oligomeric matrix protein (COMP) in relation to the evolution of joint cartilage damage and the requirement for surgery in 125 patients with rheumatoid arthritis (RA). We compared the erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) level, and matrix metalloproteinase-3 (MMP-3) levels with COMP levels determined by specific enzyme-linked immunosorbent assay (ELISA). Patients were divided into three groups: (1) patients with least erosive disease (LES); (2) patients with more erosive disease (MES); and (3) patients with mutilating disease (MUD). In addition, synovial fluid samples were collected from patients undergoing arthroscopic synovectomy of the knee joint (ASS) and total knee arthroplasty (TKA). Serum COMP levels correlated with the ESR (P < 0.0001, r = 0.374, n = 125) and the CRP level (P = 0.0014, r = 0.281, n = 125). COMP levels did not correlate with the MMP-3 level (P = 0.182, r = 0.114, n = 125). The COMP levels of the LES group were significantly lower than those of the MES or MUD groups. Lastly, synovial fluid COMP levels in the TKA group were higher than in the ASS group. Therefore, these findings suggest that serum and synovial fluid COMP levels in patients with RA may reflect cartilage destruction and are correlated with the ESR and the CRP level, which are indicators of the acute-phase response.

Novel Perfluoroacyl Olefinations of Aldehydes Using ß-Thio-Substituted Perfluoroalkyl Enol Ethers.

α-(Methylthio)- or α-(phenylthio)-substituted perfluoroacylolefinations of nonenolizable aldehydes using the ß-lithio-ß-thio-perfluoroalkyl enol ethers 1-4 stereoselectively proceeded to give (Z)-α,ß-unsaturated perfluoroalkyl ketones 9a-e, 10a-c, 11a-c, and 12a. The α-(thio)-α,ß-unsaturated trifluoromethyl ketones were easily converted to 3-(thio)-2-(trifluoromethyl)-1,3-butadienes 21a-c and 22a,b in moderate to high yields (41-85%).