Biomedical subjects
Publications and source records attributed to Yoshinori Watanabe.
Meiosis includes a reductional division in which homologous chromosomes, rather than sister chromatids, are segregated to opposite poles of the spindle. In this issue of Cell, report that casein kinase 1 contributes to this process by promoting the attachment of both kinetochores of a homolog to only one pole of the meiotic spindle in budding yeast.
Much remains unknown about the molecular regulation of meiosis. Here we show that meiosis-specific transcripts are selectively removed if expressed during vegetative growth in fission yeast. These messenger RNAs contain a cis-acting region--which we call the DSR--that confers this removal via binding to a YTH-family protein Mmi1. Loss of Mmi1 function severely impairs cell growth owing to the untimely expression of meiotic transcripts. Microarray analysis reveals that at least a dozen such meiosis-specific transcripts are eliminated by the DSR-Mmi1 system. Mmi1 remains in the form of multiple nuclear foci during vegetative growth. At meiotic prophase these foci precipitate to a single focus, which coincides with the dot formed by the master meiosis-regulator Mei2. A meiotic arrest due to the loss of the Mei2 dot is released by a reduction in Mmi1 activity. We propose that Mei2 turns off the DSR-Mmi1 system by sequestering Mmi1 to the dot and thereby secures stable expression of meiosis-specific transcripts.
Sister chromatid cohesion, mediated by a complex called cohesin, is crucial--particularly at centromeres--for proper chromosome segregation in mitosis and meiosis. In animal mitotic cells, phosphorylation of cohesin promotes its dissociation from chromosomes, but centromeric cohesin is protected by shugoshin until kinetochores are properly captured by the spindle microtubules. However, the mechanism of shugoshin-dependent protection of cohesin is unknown. Here we find a specific subtype of serine/threonine protein phosphatase 2A (PP2A) associating with human shugoshin. PP2A colocalizes with shugoshin at centromeres and is required for centromeric protection. Purified shugoshin complex has an ability to reverse the phosphorylation of cohesin in vitro, suggesting that dephosphorylation of cohesin is the mechanism of protection at centromeres. Meiotic shugoshin of fission yeast also associates with PP2A, with both proteins collaboratively protecting Rec8-containing cohesin at centromeres. Thus, we have revealed a conserved mechanism of centromeric protection of eukaryotic chromosomes in mitosis and meiosis.
To determine whether lymphangiogenesis was associated with the development of colorectal carcinoma and whether the mean maximal diameter of lymphatic microvessels (LMMMD) or lymphatic microvessel density (LMVD) is associated with lymph node metastasis in early stage invasive colorectal carcinoma (T1 carcinoma), we used immunohistochemical staining with podoplanin to measure LMMMD and LMVD in intratumoral (LMMMDit, LMVDit) and peritumoral areas (LMMMDpt, LMVDpt) of T1 carcinomas (n=87). By comparing the LMMMD and LMVD in normal large intestine (n=10), adenoma (n=15), and Tis carcinoma (n=15), we found out that the LMVDpt in T1 carcinoma with lymphatic vessel invasion (LVI) was significantly high (P<0.001), and there was a significant decrease in LMMMDpt in T1 carcinoma (P=0.031). Both LMMMDpt and LMVDpt were significantly increased in the T1 carcinomas, with LVI compared with the T1 carcinomas without LVI (P=0.018, P=0.003). Multivariate analysis revealed that LVI and combined greater LMMMDpt and greater LMVDpt were associated with lymph node metastases (P=0.005, P=0.036). These results indicate that lymphangiogenesis might be induced in the surrounding tumor areas of the T1 colorectal carcinoma with LVI; thus, evaluation of the diameter and density of lymphatic microvessels is important in T1 colorectal carcinoma to predict lymph node metastases.
BACKGROUND AND AIMS: It has been suggested that the incidence of digestive diseases associated with Helicobacter pylori is influenced by the strain diversity of H. pylori, factors involving the host or environment, and the duration of infection. The authors have previously reported that human leukocyte antigen (HLA)-DQB1*0401 plays an important role in the development of atrophic gastritis in H. pylori infected patients. The aim of the present study was to investigate the relationship between HLA-DQB1 genotype and cancer development. METHODS: HLA-DQB1 genotyping was performed by the PCR-RFLP method on 122 H. pylori-infected non-ulcer dyspepsia (NUD) patients, 53 gastric cancer patients and 28 uninfected controls. To reliably estimate the grade of atrophic gastritis, histological evaluation was performed. RESULTS: The allele frequency of DQB1*0401 was significantly higher in intestinal type cancer patients compared with age- and sex-matched H. pylori-infected NUD patients. There was no significant difference in the mean atrophic scores of the biopsy samples from the lesser curvature of the mid-corpus between these groups. CONCLUSIONS: HLA-DQB1*0401 is a useful marker for determining susceptibility to intestinal type gastric cancer.
BACKGROUND: Although cases of reflux esophagitis (RE) developing after treatment to eradicate Helicobacter pylori have been discussed in some detail, no reports are available concerning the histologic examination of RE both before and after eradication therapy. MATERIALS AND METHODS: Sixty-one patients and 111 specimens were investigated using endoscopic and histologic techniques. The histologic findings including basal zone height, papillar height, Ki-67 labeling index, and COX-2 expression before and after treatment for H. pylori infection were compared with those in normal controls and patients with endoscopic RE. RESULTS: Twelve months after eradication therapy, the incidence of newly developed endoscopic RE was 20% (5/25). Basal zone height and papillar height had increased at 1 month, but had returned to pretreatment levels after 12 months of eradication therapy. The Ki-67 labeling index was significantly increased 1 and 12 months after eradication therapy compared to values before treatment. COX-2 expression gradually increased after the treatment. The phenomena linked to esophagitis appeared after eradication therapy. However, the severity and extent of these signs were not so high after the treatment of H. pylori than those in patients with overt reflux esophagitis. Focusing on the patients with hiatal hernia, papillar height and Ki-67 labeling index increased significantly after eradication therapy, values being almost the same as those in the patients with endoscopic RE. CONCLUSIONS: Hiatal hernia plays an important role in the possible occurrence of hidden RE after treatment for a H. pylori infection.
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UNLABELLED: We studied the possibility that cryopreserved human heart cells could be transplanted with some advantage. METHOD: Cells derived human atrial tissues (control group (n = 13)), cryopreserved cells (cell-cryopreservation group (n = 23), and cells derived cryopreserved tissue (tissue-cryopreservation group (n = 29)) were cultured for 15 days. The cell proliferation was compared between control and cryopreservation group by growth curves. BasicFGF, TGFbeta-1, IL-6, IL-8, and cell cycle were measured at pre and post-cryopreservation. Mixed Lymphocyte-heart cell culture established by PBL and heart cells was evaluated by PBL proliferation. Transplanted cells were evaluated by visually and histology. RESULTS: Cryopreserved cells were proliferated much more than control cells (p < 0.0001). The growth factors were increased, and cytokines were decreased by cryopreservation (p < 0.05). The cryopreserved cell cycles were shifted to G2 + M from G1 + G0 period. Cryopreserved cells stimulated PBL less than non-cryopreserved cells (p < 0.0001). Transplanted cryopreserved cell were survived. CONCLUSION: Cryopreserved human heart cells can be transplanted, and proliferated much more than non-cryopreserved cells. Cryopreservation enables the human cells to be more prolific, and reduced the immunogenicity of them. The transplanted cryopreserved cells survived and formed cardiac-like tissue.
An emergency off-pump coronary artery bypass (OPCAB) was performed successfully in an aged patient with acute coronary syndrome (ACS). The patient, an 80-year-old woman residing in a nursing home, suddenly lost consciousness during lunch. The electrocardiogram (ECG) showed ventricular fibrillation (Vf) but defibrillation successfully recovered the sinus rhythm. The patient was brought to our hospital as an emergency. She underwent emergency cardiac catheterization. Coronary angiography demonstrated severe three vessel disease with left main coronary trunk (LMT) stenosis. Even during intra-aortic balloon pumping (IABP), the hemodynamic state was unstable, with repeated development of ventricular tachycardia and fibrillation. An emergency coronary artery bypass without a cardiopulmonary bypass was performed. Saving her life was of primary importance and revascularization of the left anterior descending artery (LAD) branch, was performed. Thanks to the advances made in various devices, safe and reliable anastomoses have become possible in OPCAB applied to ACS. OPCAB for ACS have become safe and reliable anastomoses following development of various devices. We think that OPCAB is an effective surgical technique for coronary revascularization for emergency or serious cases involving elderly patients.
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OBJECTIVE: To clarify the position of on-pump beating coronary artery bypass (CAB) and to define preoperative indicators of intentional conversion to the procedure in the era of advancement of off-pump CAB (OPCAB), we assessed on-pump beating CAB performed after the introduction of OPCAB. SUBJECTS AND METHODS: We assessed 130 patients who underwent single CAB [117 (90%) with OPCAB and 13 (10%) with on-pump beating CAB] between August 1999 (when OPCAB was selected as the first-line surgical procedure) and December 2004. RESULTS: No significant differences were seen between the groups in the number of coronary lesions or the prevalence of left main trunk (LMT) lesion. Reduced left cardiac function, cardiac dilatation, and mitral regurgitation (MR) were more remarkable in the on-pump beating CAB group. Preoperative ischemic condition was generally unstable in the both groups. A conversion to on-pump beating CAB occurred at anastomosis for the left anterior descending (LAD) branch in 61% and for the left circumflex (LCX) branch in 15%. LAD patients had more severe left cardiac dysfunction and cardiac dilatation than LCX patients. CONCLUSION: To perform safe and reliable CAB surgery, cardiovascular surgeons should define preoperative indicators of difficult OPCAB and convert OPCAB to on-pump beating CAB intentionally without hesitation when unstable hemodynamics is detected.
OBJECTIVE: We assessed potential limitations of retrograde continuous tepid blood cardioplegia (RCTBC) for myocardial remodeling, represented by hypertrophied and/or dilated myocardium in patients with severe cardiomyopathy following single aortic valve replacement. METHODS: The study was conducted on 91 patients who underwent initial single aortic valve replacement with tepid cardiopulmonary bypass (CPB) and RCTBC. Based on the postoperative maximum creatine phosphokinase (max CPK)-MB level, the patients were allocated to Group H (>/=100 IU/mL) with severe cardiomyopathy or Group L (<100 IU/mL) to make intergroup comparisons of preoperative, intraoperative, and postoperative parameter values. RESULTS: Preoperative measurements were as follows: pressure gradient between left ventricle and aorta (DeltaPG), 92.8+/-46.2 mmHg in Group H and 57.9+/-41.6 mmHg in Group L (p<0.01); implanted valve size, 21.0+/-2.2 mm in Group H and 22.8+/-2.2 mm in Group L (p<0.01); left ventricular end-diastolic volume (LVEDV), 155.7+/-73.3 mL in Group H and 224.3+/-101.5 mL in Group L (p<0.01). The rate of RCTBC flow rate increase did not differ between the groups (17.6% in Group H and 20.7% in Group L), while the rate of concomitant use of optional antegrade coronary perfusion was significantly lower in Group H (25%) than in Group L (37%) (p<0.05). Pre- and post-perfusion lactic acid levels in the myocardial protection solution measured every 30 min after aortic cross clamping were higher in Group H than in Group L. CONCLUSION: The study suggests preoperative high DeltaPG, small aortic root diameter, and low LVEDV, namely, concentrically hypertrophied myocardium, as risk factors for severe cardiomyopathy after RCTBC. RCTBC in patients with any risk factor should be accompanied by an increase in initial continuous perfusion flow and/or aggressive use of intermittent antegrade coronary perfusion.
Meiosis resembles mitosis but employs a unique "reductional" nuclear division to allow the production of haploid gametes from diploid cells. The crucial ploidy reduction step requires that sister kinetochores attach to microtubules emanating from the same spindle pole, achieving "monopolar attachment," which ensures that maternal and paternal chromosomes are segregated. Here we screened for factors required to establish monopolar attachment in fission yeast and identified a novel protein, Moa1. Moa1 is meiosis specific and localizes exclusively to the central core of the centromere, a region that binds meiotic Rec8-containing cohesin complexes but not mitotic Rad21/Scc1-containing complexes. Enforced cleavage of Rec8 in the central core region led to the disruption of monopolar attachment, as in moa1Delta cells, without diminishing Moa1 localization. Moa1 physically interacts with Rec8, implying that Moa1 functions only through Rec8, presumably to facilitate central core cohesion. These results prove that monoorientation of kinetochores is established in a cohesion-mediated manner.
A recently emerging protein family, shugoshin, plays a crucial role in the centromeric protection of cohesin, which is responsible for sister chromatid cohesion. This is especially important at the first meiotic division, where cohesin is cleaved by separase only along chromosome arms while the centromeric cohesin must be preserved. In vertebrate cells, arm cohesion is largely lost during prophase and prometaphase in order to facilitate sister chromatid resolution, whereas centromeric cohesion is preserved until the bipolar attachment of sister chromatids is established. Vertebrate shugoshin plays an essential role in protecting centromeric cohesin from prophase dissociation. In yeast, shugoshin also has a crucial role in sensing the loss of tension at kinetochores and in generating the spindle checkpoint signal.
The different regulation of sister chromatid cohesion at centromeres and along chromosome arms is obvious during meiosis, because centromeric cohesion, but not arm cohesion, persists throughout anaphase of the first division. A protein required to protect centromeric cohesin Rec8 from separase cleavage has been identified and named shugoshin (or Sgo1) after shugoshin ("guardian spirit" in Japanese). It has become apparent that shugoshin shows marginal homology with Drosophila Mei-S332 and several uncharacterized proteins in other eukaryotic organisms. Because Mei-S332 is a protein previously shown to be required for centromeric cohesion in meiosis, it is now established that shugoshin represents a conserved protein family defined as a centromeric protector of Rec8 cohesin complexes in meiosis. The regional difference of sister chromatid cohesion is also observed during mitosis in vertebrates; the cohesion is much more robust at the centromere at metaphase, where it antagonizes the pulling force of spindle microtubules that attach the kinetochores from opposite poles. The human shugoshin homologue (hSgo1) is required to protect the centromeric localization of the mitotic cohesin, Scc1, until metaphase. Bub1 plays a crucial role in the localization of shugoshin to centromeres in both fission yeast and humans.
Shugoshin (Sgo) proteins constitute a conserved protein family defined as centromeric protectors of Rec8-containing cohesin complexes in meiosis . In vertebrate mitosis, Scc1/Rad21-containing cohesin complexes are also protected at centromeres because arm cohesin, but not centromeric cohesin, is largely dissociated in pro- and prometaphase . The dissociation process is dependent on the activity of polo-like kinase (Plk1) and partly dependent on Aurora B . Recently, it has been demonstrated that vertebrate shugoshin is required for preserving centromeric cohesion during mitosis ; however, it was not addressed whether human shugoshin protects cohesin itself. Here, we show that the persistence of human Scc1 at centromeres in mitosis is indeed dependent on human Sgo1. In fission yeast, Sgo localization depends on Bub1, a conserved spindle checkpoint protein, which is enigmatically also required for chromosome congression during prometaphase in vertebrate cells. We demonstrate that human Sgo1 fails to localize at centromeres in Bub1-repressed cells, and centromeric cohesion is significantly loosened. Remarkably, in these cells, Sgo1 relocates to chromosomes all along their length and provokes ectopic protection from dissociation of Scc1 on chromosome arms. These results reveal a hitherto concealed role for human Bub1 in defining the persistent cohesion site of mitotic chromosomes.
There is an obvious difference between the regulation of sister chromatid cohesion at centromeres and along chromosome arms during meiosis, because centromeric cohesion, but not arm cohesion, persists throughout anaphase of the first meiotic division. This regional difference of sister chromatid cohesion is also observed during mitosis; the cohesion is much more robust at the centromere at metaphase, where it antagonizes the pulling force of spindle microtubules that attach to the kinetochores from opposite poles. Recent studies have illuminated the underlying molecular mechanisms that strengthen and protect centromeric cohesion in mitosis and meiosis, and the central role of a conserved protein, shugoshin.
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