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951.
O'Rourke SM Carter C Carter L Christensen SN Jones MP Nash B Price MH Turnbull DW Garner AR Hamill DR Osterberg VR Lyczak R Madison EE Nguyen MH Sandberg NA Sedghi N Willis JH Yochem J Johnson EA Bowerman B 《PloS one》2011,6(3):e16644
To study essential maternal gene requirements in the early C. elegans embryo, we have screened for temperature-sensitive, embryonic lethal mutations in an effort to bypass essential zygotic requirements for such genes during larval and adult germline development. With conditional alleles, multiple essential requirements can be examined by shifting at different times from the permissive temperature of 15°C to the restrictive temperature of 26°C. Here we describe 24 conditional mutations that affect 13 different loci and report the identity of the gene mutations responsible for the conditional lethality in 22 of the mutants. All but four are mis-sense mutations, with two mutations affecting splice sites, another creating an in-frame deletion, and one creating a premature stop codon. Almost all of the mis-sense mutations affect residues conserved in orthologs, and thus may be useful for engineering conditional mutations in other organisms. We find that 62% of the mutants display additional phenotypes when shifted to the restrictive temperature as L1 larvae, in addition to causing embryonic lethality after L4 upshifts. Remarkably, we also found that 13 out of the 24 mutations appear to be fast-acting, making them particularly useful for careful dissection of multiple essential requirements. Our findings highlight the value of C. elegans for identifying useful temperature-sensitive mutations in essential genes, and provide new insights into the requirements for some of the affected loci. 相似文献
952.
Chronological aging has been studied extensively in laboratory yeast by culturing cells into stationary phase in synthetic complete medium with 2% glucose as the carbon source. During this process, acidification of the culture medium occurs due to secretion of organic acids, including acetic acid, which limits survival of yeast cells. Dietary restriction or buffering the medium to pH 6 prevents acidification and increases chronological life span. Here we set out to determine whether these effects are specific to laboratory-derived yeast by testing the chronological aging properties of the vineyard yeast strain RM11. Similar to the laboratory strain BY4743 and its haploid derivatives, RM11 and its haploid derivatives displayed increased chronological life span from dietary restriction, buffering the pH of the culture medium, or aging in rich medium. RM11 and BY4743 also displayed generally similar aging and growth characteristics when cultured in a variety of different carbon sources. These data support the idea that mechanisms of chronological aging are similar in both the laboratory and vineyard strains. 相似文献
953.
Kisby GE Fry RC Lasarev MR Bammler TK Beyer RP Churchwell M Doerge DR Meira LB Palmer VS Ramos-Crawford AL Ren X Sullivan RC Kavanagh TJ Samson LD Zarbl H Spencer PS 《PloS one》2011,6(6):e20911
Methylazoxymethanol (MAM), the genotoxic metabolite of the cycad azoxyglucoside cycasin, induces genetic alterations in bacteria, yeast, plants, insects and mammalian cells, but adult nerve cells are thought to be unaffected. We show that the brains of adult C57BL6 wild-type mice treated with a single systemic dose of MAM acetate display DNA damage (O
6-methyldeoxyguanosine lesions, O
6-mG) that remains constant up to 7 days post-treatment. By contrast, MAM-treated mice lacking a functional gene encoding the DNA repair enzyme O
6-mG DNA methyltransferase (MGMT) showed elevated O
6-mG DNA damage starting at 48 hours post-treatment. The DNA damage was linked to changes in the expression of genes in cell-signaling pathways associated with cancer, human neurodegenerative disease, and neurodevelopmental disorders. These data are consistent with the established developmental neurotoxic and carcinogenic properties of MAM in rodents. They also support the hypothesis that early-life exposure to MAM-glucoside (cycasin) has an etiological association with a declining, prototypical neurodegenerative disease seen in Guam, Japan, and New Guinea populations that formerly used the neurotoxic cycad plant for food or medicine, or both. These findings suggest environmental genotoxins, specifically MAM, target common pathways involved in neurodegeneration and cancer, the outcome depending on whether the cell can divide (cancer) or not (neurodegeneration). Exposure to MAM-related environmental genotoxins may have relevance to the etiology of related tauopathies, notably, Alzheimer''s disease. 相似文献
954.
Gehring AJ Koh S Chia A Paramasivam K Chew VS Ho ZZ Lee KH Maini MK Madhavan K Lim SG Bertoletti A 《PloS one》2011,6(8):e23330
T cell functional plasticity helps tailor antiviral immunity during different phases of infections. We tested whether, during different phases of HBV infection, virus-specific T cells can acquire specific proinflammatory functions that could drive granulocyte/mononuclear cell liver infiltration. Multifunctional analysis of HBV-specific T cells during acute and chronic HBV infection revealed that HBV-specific T cells had the capacity to produce the neutrophil chemokine CXCL-8 but not IL-17. CXCL-8 producing T cells were detectable in the liver of chronic HBV patients with active hepatitis; while in acute HBV patients CXCL-8 production by T cells was temporally limited to the acute phase of disease, concomitant with the peak of liver inflammation. Characterization of the conditions necessary for the development of CXCL-8 producing T cells showed a requirement for IL-7 and IL-15 during T cell expansion. These data show that functional plasticity of virus-specific T cells spontaneously occurs during HBV infection and that an environment rich IL-7 and IL-15 can license T cells with the ability to produce CXCL-8 and potentially influence liver pathology. 相似文献
955.
Yang Sun Gay Hui Ho Heng Nung Koong Gayathri Sivaramakrishnan Wei Tzer Ang Qiu Mei Koh Valerie C.-L. Lin 《Biochemical and biophysical research communications》2013
Tripartite-motif containing 22 (TRIM22) is a direct p53 target gene and inhibits the clonogenic growth of leukemic cells. Its expression in Wilms tumors is negatively associated with disease relapse. This study addresses if TRIM22 expression is de-regulated in breast carcinoma. Western blotting analysis of a panel of 10 breast cancer cell lines and 3 non-malignant mammary epithelial cell lines with a well-characterized TRIM22 monoclonal antibody showed that TRIM22 protein is greatly under-expressed in breast cancer cells as compared to non-malignant cell lines. Similarly, TRIM22 protein is significantly down-regulated in breast tumors as compared to matched normal breast tissues. Study of cell lines with methylation inhibitor and bisulfite sequencing indicates that TRIM22 promoter hypermethylation may not be the cause for TRIM22 under-expression in breast cancer. Instead, we found that TRIM22 protein level correlates strongly (R = 0.79) with p53 protein level in normal breast tissue, but this correlation is markedly impaired (R = 0.48) in breast cancer tissue, suggesting that there is some defects in p53 regulation of TRIM22 gene in breast cancer. This notion is supported by cell line studies, which showed that TRIM22 was no longer inducible by p53-activating genotoxic drugs in breast cancer cell lines and in a p53 null cell line H1299 transfected with wild type p53. In conclusion, this study shows that TRIM22 is greatly under-expressed in breast cancer. p53 dysfunction may be one of the mechanisms for TRIM22 down-regulation. 相似文献
956.
Valerie C. Coffman Jennifer A. Sees David R. Kovar Jian-Qiu Wu 《The Journal of cell biology》2013,203(1):101-114
Both de novo–assembled actin filaments at the division site and existing filaments recruited by directional cortical transport contribute to contractile ring formation during cytokinesis. However, it is unknown which source is more important. Here, we show that fission yeast formin For3 is responsible for node condensation into clumps in the absence of formin Cdc12. For3 localization at the division site depended on the F-BAR protein Cdc15, and for3 deletion was synthetic lethal with mutations that cause defects in contractile ring formation. For3 became essential in cells expressing N-terminal truncations of Cdc12, which were more active in actin assembly but depended on actin filaments for localization to the division site. In tetrad fluorescence microscopy, double mutants of for3 deletion and cdc12 truncations were severely defective in contractile ring assembly and constriction, although cortical transport of actin filaments was normal. Together, these data indicate that different formins cooperate in cytokinesis and that de novo actin assembly at the division site is predominant for contractile ring formation. 相似文献
957.
Xianrong Zhang Ji Zhu Yumei Li Tiao Lin Valerie A. Siclari Abhishek Chandra Elena M. Candela Eiki Koyama Motomi Enomoto-Iwamoto Ling Qin 《The Journal of biological chemistry》2013,288(45):32229-32240
The epidermal growth factor receptor (EGFR) is an essential player in the development of multiple organs during embryonic and postnatal stages. To understand its role in epiphyseal cartilage development, we generated transgenic mice with conditionally inactivated EGFR in chondrocytes. Postnatally, these mice exhibited a normal initiation of cartilage canals at the perichondrium, but the excavation of these canals into the cartilage was strongly suppressed, resulting in a delay in the formation of the secondary ossification center (SOC). This delay was accompanied by normal chondrocyte hypertrophy but decreased mineralization and apoptosis of hypertrophic chondrocytes and reduced osteoclast number at the border of marrow space. Immunohistochemical analyses demonstrated that inactivation of chondrocyte-specific EGFR signaling reduced the amounts of matrix metalloproteinases (MMP9, -13, and -14) and RANKL (receptor activator of NF-κB ligand) in the hypertrophic chondrocytes close to the marrow space and decreased the cartilage matrix degradation in the SOC. Analyses of EGFR downstream signaling pathways in primary epiphyseal chondrocytes revealed that up-regulation of MMP9 and RANKL by EGFR signaling was partially mediated by the canonical Wnt/β-catenin pathway, whereas EGFR-enhanced MMP13 expression was not. Further biochemical studies suggested that EGFR signaling stimulates the phosphorylation of LRP6, increases active β-catenin level, and induces its nuclear translocation. In line with these in vitro studies, deficiency in chondrocyte-specific EGFR activity reduced β-catenin amount in hypertrophic chondrocytes in vivo. In conclusion, our work demonstrates that chondrocyte-specific EGFR signaling is an important regulator of cartilage matrix degradation during SOC formation and epiphyseal cartilage development and that its actions are partially mediated by activating the β-catenin pathway. 相似文献
958.
Niclas Engene Valerie J. Paul Tara Byrum William H. Gerwick Andrea Thor Mark H. Ellisman 《Journal of phycology》2013,49(6):1095-1106
An adverse consequence of applying morphology‐based taxonomic systems to catalog cyanobacteria, which generally are limited in the number of available morphological characters, is a fundamental underestimation of natural biodiversity. In this study, we further dissect the polyphyletic cyanobacterial genus Lyngbya and delineate the new genus Okeania gen. nov. Okeania is a tropical and subtropical, globally distributed marine group abundant in the shallow‐water benthos. Members of Okeania are of considerable ecological and biomedical importance because specimens within this group biosynthesize biologically active secondary metabolites and are known to form blooms in coastal benthic environments. Herein, we describe five species of the genus Okeania: O. hirsuta (type species of the genus), O. plumata, O. lorea, O. erythroflocculosa, and O. comitata, under the provisions of the International Code of Nomenclature for Algae, Fungi, and Plants. All five Okeania species were morphologically, phylogenetically, and chemically distinct. This investigation provides a classification system that is able to identify Okeania spp. and predict their production of bioactive secondary metabolites. 相似文献
959.
Christine V. Hawkes Stephanie N. Kivlin Jennifer Du Valerie T. Eviner 《Plant and Soil》2013,369(1-2):141-150
Background
Current knowledge of plant-soil feedback is based largely on single end point studies with soils conditioned by monocultures, but accounting for variability in the ecological impacts of feedback effects may require understanding how feedback develops over time and in multi-species plant communities.Methods
To examine temporal development and additivity of feedback, two pairs of native and non-native congeneric grasses were grown alone or in mixtures to create six soil conditioning treatments. We measured plant growth and feedback on the soils over 19 months and addressed whether plant biomass was additive or non-additive between soils treated by mixtures and their constituent monocultures.Results
For native grasses, plant-soil feedback either became progressively more negative through time or switched from neutral to negative. Feedback to non-native grasses was variably neutral to positive. Final biomass of the grasses growing on soils conditioned by mixtures was generally an additive function of growth on soils conditioned by the component monocultures, except native grasses growing in soils conditioned by their own congener mixtures, which were non-additive.Conclusions
Temporal variation and non-additivity in feedback suggest that extrapolation to communities may be complex. More work is needed to assess the generality of temporal and scaling effects. 相似文献960.
Norosoa J. Razafinarivo Romain Guyot Aaron P. Davis Emmanuel Couturon Serge Hamon Dominique Crouzillat Michel Rigoreau Christine Dubreuil-Tranchant Valerie Poncet Alexandre De Kochko Jean-Jacques Rakotomalala Perla Hamon 《Annals of botany》2013,111(2):229-248