| 4801. |
- Corcoran, Padraic, et al.
(författare)
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Introgression maintains the genetic integrity of the mating-type determining chromosome of the fungus Neurospora tetrasperma.
- 2016
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Ingår i: Genome Research. - : Cold Spring Harbor Laboratory. - 1088-9051 .- 1549-5469. ; 26:4, s. 486-498
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Tidskriftsartikel (refereegranskat)abstract
- Genome evolution is driven by a complex interplay of factors, including selection, recombination, and introgression. The regions determining sexual identity are particularly dynamic parts of eukaryotic genomes that are prone to molecular degeneration associated with suppressed recombination. In the fungus Neurospora tetrasperma, it has been proposed that this molecular degeneration is counteracted by the introgression of nondegenerated DNA from closely related species. In this study, we used comparative and population genomic analyses of 92 genomes from eight phylogenetically and reproductively isolated lineages of N. tetrasperma, and its three closest relatives, to investigate the factors shaping the evolutionary history of the genomes. We found that suppressed recombination extends across at least 6 Mbp (similar to 63%) of the mating-type (mat) chromosome in N. tetrasperma and is associated with decreased genetic diversity, which is likely the result primarily of selection at linked sites. Furthermore, analyses of molecular evolution revealed an increased mutational load in this region, relative to recombining regions. However, comparative genomic and phylogenetic analyses indicate that the mat chromosomes are temporarily regenerated via introgression from sister species; six of eight lineages show introgression into one of their mat chromosomes, with multiple Neurospora species acting as donors. The introgressed tracts have been fixed within lineages, suggesting that they confer an adaptive advantage in natural populations, and our analyses support the presence of selective sweeps in at least one lineage. Thus, these data strongly support the previously hypothesized role of introgression as a mechanism for the maintenance of mating-type determining chromosomal regions.
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| 4802. |
- Corcoran, Padraic, et al.
(författare)
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Quantifying functional heterothallism in the pseudohomothallic ascomycete Neurospora tetrasperma
- 2012
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Ingår i: Fungal Biology. - : Elsevier BV. - 1878-6146 .- 1878-6162. ; 116:9, s. 962-975
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Tidskriftsartikel (refereegranskat)abstract
- Neurospora tetrasperma is a pseudohomothallic filamentous ascomycete that has evolved from heterothallic ancestors. Throughout its life cycle, it is predominantly heterokaryotic for mating type, and thereby self-fertile. However, studies of N. tetrasperma have revealed the occasional production of self-sterile asexual and sexual spores of a single-mating type, indicating that it can be functionally heterothallic. Here, we report the extensive sampling and isolation of natural, heterokaryotic, strains of N. tetrasperma from the United Kingdom (UK): 99 strains were collected from Surrey, England, and four from Edinburgh, Scotland. We verified by phylogenetic analyses that these strains belong to N. tetrasperma. We isolated cultures from single germinated asexual spores (conidia) from 17 of these newly sampled UK strains from Surrey, and 16 previously sampled strains of N. tetrasperma from New Zealand (NZ). Our results show that the N. tetrasperrna strains from the UK population produced a significantly greater proportion of self-sterile, homokaryotic conidia than the NZ population: the proportion of homokaryotic conidia was 42.6 % (133/312 spores) and 15.3 % (59/386) from the UK and the NZ populations, respectively. Although homokaryons recovered from several strains show a bias for one of the mating types, the total ratio of mat A to mat a mating type in homokaryons (UK: 72/61, NZ 28/31) did not deviate significantly from the expected 1:1 ratio for either of these populations. These results indicate that different populations exhibit differences in their life cycle characteristics, and that a higher degree of outcrossing might be expected from the UK population. This study points to the importance of studying multiple strains and populations when investigating life history traits of an organism with a complex life cycle, as previously undetected differences between populations may be revealed.
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| 4803. |
- Cordeddu, Viviana, et al.
(författare)
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Activating Mutations Affecting the Dbl Homology Domain of SOS2 Cause Noonan Syndrome
- 2015
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Ingår i: Human Mutation. - : WILEY-BLACKWELL. - 1059-7794 .- 1098-1004. ; 36:11, s. 1080-1087
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Tidskriftsartikel (refereegranskat)abstract
- The RASopathies constitute a family of autosomal-dominant disorders whose major features include facial dysmorphism, cardiac defects, reduced postnatal growth, variable cognitive deficits, ectodermal and skeletal anomalies, and susceptibility to certain malignancies. Noonan syndrome (NS), the commonest RASopathy, is genetically heterogeneous and caused by functional dysregulation of signal transducers and regulatory proteins with roles in the RAS/extracellular signal-regulated kinase (ERK) signal transduction pathway. Mutations in known disease genes account for approximately 80% of affected individuals. Here, we report that missense mutations altering Son of Sevenless, Drosophila, homolog 2 (SOS2), which encodes a RAS guanine nucleotide exchange factor, occur in a small percentage of subjects with NS. Four missense mutations were identified in five unrelated sporadic cases and families transmitting NS. Disease-causing mutations affected three conserved residues located in the Dbl homology (DH) domain, of which two are directly involved in the intramolecular binding network maintaining SOS2 in its autoinhibited conformation. All mutations were found to promote enhanced signaling from RAS to ERK. Similar to NS-causing SOS1 mutations, the phenotype associated with SOS2 defects is characterized by normal development and growth, as well as marked ectodermal involvement. Unlike SOS1 mutations, however, those in SOS2 are restricted to the DH domain.
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| 4804. |
- Corkhill, Claire L., et al.
(författare)
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Contribution of Energetically Reactive Surface Features to the Dissolution of CeO2 and ThO2 Analogues for Spent Nuclear Fuel Microstructures
- 2014
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 6:15, s. 12279-12289
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Tidskriftsartikel (refereegranskat)abstract
- In the safety case for the geological disposal of nuclear waste, the release of radioactivity from the repository is controlled by the dissolution of the spent fuel in groundwater. There remain several uncertainties associated with understanding spent fuel dissolution, including the contribution of energetically reactive surface sites to the dissolution rate. In this study, we investigate how surface features influence the dissolution rate of synthetic CeO2 and ThO2, spent nuclear fuel analogues that approximate as closely as possible the microstructure characteristics of fuel-grade UO2 but are not sensitive to changes in oxidation state of the cation. The morphology of grain boundaries (natural features) and surface facets (specimen preparation-induced features) was investigated during dissolution. The effects of surface polishing on dissolution rate were also investigated. We show that preferential dissolution occurs at grain boundaries, resulting in grain boundary decohesion and enhanced dissolution rates. A strong crystallographic control was exerted, with high misorientation angle grain boundaries retreating more rapidly than those with low misorientation angles, which may be due to the accommodation of defects in the grain boundary structure. The data from these simplified analogue systems support the hypothesis that grain boundaries play a role in the so-called "instant release fraction" of spent fuel, and should be carefully considered, in conjunction with other chemical effects, in safety performance assessements for the geological disposal of spent fuel. Surface facets formed during the sample annealing process also exhibited a strong crystallographic control and were found to dissolve rapidly on initial contact with dissolution medium. Defects and strain induced during sample polishing caused an overestimation of the dissolution rate, by up to 3 orders of magnitude.
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| 4805. |
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| 4806. |
- Corsi, I., et al.
(författare)
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Common Strategies and Technologies for the Ecosafety Assessment and Design of Nanomaterials Entering the Marine Environment
- 2014
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Ingår i: Acs Nano. - 1936-0851. ; 8:10, s. 9694-9709
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Tidskriftsartikel (refereegranskat)abstract
- The widespread use of engineered nanomaterials (ENMs) in a variety of technologies and consumer products inevitably causes their release into aquatic environments and final deposition into the oceans. In addition, a growing number of ENM products are being developed specifically for marine applications, such as antifouling coatings and environmental remediation systems, thus increasing the need to address any potential risks for marine organisms and ecosystems. To safeguard the marine environment, major scientific gaps related to assessing and designing ecosafe ENMs need to be filled. In this Nano Focus, we examine key issues related to the state-of-the-art models and analytical tools being developed to understand ecological risks and to design safeguards for marine organisms.
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| 4807. |
- Corvigno, Sara, et al.
(författare)
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Multi-parametric profiling of renal cell, colorectal, and ovarian cancer identifies tumour-type-specific stroma phenotypes and a novel vascular biomarker
- 2017
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Ingår i: The journal of pathology. Clinical research. - : WILEY. - 2056-4538. ; 3:3, s. 214-224
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Tidskriftsartikel (refereegranskat)abstract
- A novel set of integrated procedures for quantification of fibroblast-rich stroma and vascular characteristics has recently been presented allowing discovery of novel perivascular and stromal biomarkers in colorectal, renal cell, and ovarian cancer. In the present study, data obtained through these procedures from clinically well-annotated collections of these three tumour types have been used to address two novel questions. First, data have been used to investigate if the three tumour types demonstrate significant differences regarding features such as vessel diameter, vessel density, and perivascular marker expression. Second, analyses of the cohorts have been used to explore the prognostic significance of a novel vascular metric, 'vessel distance inter-quartile range (IQR)' that describes intra-case heterogeneity regarding vessel distribution. The comparisons between the three tumour types demonstrated a set of significant differences. Vessel density of renal cell cancer was statistically significantly higher than in colorectal and ovarian cancer. Vessel diameter was statistically significantly higher in ovarian cancer. Concerning perivascular status, colorectal cancer displayed significantly higher levels of perivascular PDGFR-beta expression than the other two tumour types. Intra-case heterogeneity of perivascular PDGFR-beta expression was also higher in colorectal cancer. Notably, these fibroblast-dominated stroma phenotypes matched previously described experimental tumour stroma characteristics, which have been linked to differential sensitivity to anti-VEGF drugs. High 'vessel distance IQR' was significantly associated with poor survival in both renal cell cancer and colorectal cancer. In renal cell cancer, this characteristic also acted as an independent prognostic marker according to multivariate analyses including standard clinico-pathological characteristics. Explorative subset analyses indicated particularly strong prognostic significance of 'vessel distance IQR' in T stage 4 of this cancer type. Together, these analyses identified tumour-type-specific vascular-stroma phenotypes of possible functional significance, and suggest 'vessel distance IQR' as a novel prognostic biomarker.
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| 4808. |
- Costa, Nathalia, et al.
(författare)
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A Definition of "Flare" in Low Back Pain: A Multiphase Process Involving Perspectives of Individuals With Low Back Pain and Expert Consensus
- 2019
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Ingår i: Journal of Pain. - : CHURCHILL LIVINGSTONE. - 1526-5900 .- 1528-8447. ; 20:11, s. 1267-1275
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Tidskriftsartikel (refereegranskat)abstract
- Low back pain (LBP) varies over time. Consumers, clinicians, and researchers use various terms to describe LBP fluctuations, such as episodes, recurrences and flares. Although "flare" is use commonly, there is no consensus on how it is defined. This study aimed to obtain consensus for a LBP flare definition using a mixed-method approach. Step 1 involved the derivation of a preliminary candidate flare definition based on thematic analysis of views of 130 consumers in consultation with an expert consumer writer. In step 2, a workshop was conducted to incorporate perspectives of 19 LBP experts into the preliminary flare definition, which resulted in 2 alternative LBP flare definitions. Step 3 refined the definition using a 2-round Delphi consensus with 50 experts in musculoskeletal conditions. The definition favored by experts was further tested with 16 individuals with LBP in step 4, using the definition in three scenarios. This multiphase study produced a definition of LBP flare that distinguishes it from other LBP fluctuations, represents consumers views, involves expert consensus, and is understandable by consumers in clinical and research contexts: "A flare-up is a worsening of your condition that lasts from hours to weeks that is difficult to tolerate and generally impacts your usual activities and/or emotions." Perspective: A multiphase process, incorporating consumers views and expert consensus, produced a definition of LBP flare that distinguishes it from other LBP fluctuations. (C) 2019 by the American Pain Society
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| 4809. |
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| 4810. |
- Cotrim, Camila A., et al.
(författare)
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A structural overview of the zinc transporters in the cation diffusion facilitator family
- 2019
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Ingår i: Acta Crystallographica Section D. - 2059-7983. ; 75, s. 357-367
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Forskningsöversikt (refereegranskat)abstract
- The cation diffusion facilitators (CDFs) are a family of membrane-bound proteins that maintain cellular homeostasis of essential metal ions. In humans, the zinc-transporter CDF family members (ZnTs) play important roles in zinc homeostasis. They do this by facilitating zinc efflux from the cytoplasm to the extracellular space across the plasma membrane or into intracellular organelles. Several ZnTs have been implicated in human health owing to their association with type 2 diabetes and neurodegenerative diseases. Although the structure determination of CDF family members is not trivial, recent advances in membrane-protein structural biology have resulted in two structures of bacterial YiiPs and several structures of their soluble C-terminal domains. These data reveal new insights into the molecular mechanism of ZnT proteins, suggesting a unique rocking-bundle mechanism that provides alternating access to the metal-binding site.
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