716 research outputs found

    Genome-wide analysis of alternative splicing in Chlamydomonas reinhardtii

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    <p>Abstract</p> <p>Background</p> <p>Genome-wide computational analysis of alternative splicing (AS) in several flowering plants has revealed that pre-mRNAs from about 30% of genes undergo AS. <it>Chlamydomonas</it>, a simple unicellular green alga, is part of the lineage that includes land plants. However, it diverged from land plants about one billion years ago. Hence, it serves as a good model system to study alternative splicing in early photosynthetic eukaryotes, to obtain insights into the evolution of this process in plants, and to compare splicing in simple unicellular photosynthetic and non-photosynthetic eukaryotes. We performed a global analysis of alternative splicing in <it>Chlamydomonas reinhardtii </it>using its recently completed genome sequence and all available ESTs and cDNAs.</p> <p>Results</p> <p>Our analysis of AS using BLAT and a modified version of the Sircah tool revealed AS of 498 transcriptional units with 611 events, representing about 3% of the total number of genes. As in land plants, intron retention is the most prevalent form of AS. Retained introns and skipped exons tend to be shorter than their counterparts in constitutively spliced genes. The splice site signals in all types of AS events are weaker than those in constitutively spliced genes. Furthermore, in alternatively spliced genes, the prevalent splice form has a stronger splice site signal than the non-prevalent form. Analysis of constitutively spliced introns revealed an over-abundance of motifs with simple repetitive elements in comparison to introns involved in intron retention. In almost all cases, AS results in a truncated ORF, leading to a coding sequence that is around 50% shorter than the prevalent splice form. Using RT-PCR we verified AS of two genes and show that they produce more isoforms than indicated by EST data. All cDNA/EST alignments and splice graphs are provided in a website at <url>http://combi.cs.colostate.edu/as/chlamy</url>.</p> <p>Conclusions</p> <p>The extent of AS in <it>Chlamydomonas </it>that we observed is much smaller than observed in land plants, but is much higher than in simple unicellular heterotrophic eukaryotes. The percentage of different alternative splicing events is similar to flowering plants. Prevalence of constitutive and alternative splicing in <it>Chlamydomonas</it>, together with its simplicity, many available public resources, and well developed genetic and molecular tools for this organism make it an excellent model system to elucidate the mechanisms involved in regulated splicing in photosynthetic eukaryotes.</p

    Cognitive testing of physical activity and acculturation questions in recent and long-term Latino immigrants

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    <p>Abstract</p> <p>Background</p> <p>We ascertained the degree to which language (English versus Spanish), and residence time in the US influence responses to survey questions concerning two topics: self-reported acculturation status, and recent physical activity (PA). This topic is likely to be of general interest because of growing numbers of immigrants in countries worldwide.</p> <p>Methods</p> <p>We carried out qualitative (cognitive) interviews of survey items on acculturation and physical activity on 27 Latino subjects from three groups: (a) In Spanish, of those of low residence time (less than five years living in the U.S.) (n = 9); (b) In Spanish, of those of high residence time (15 or more years in the U.S) (n = 9); and (c) in English, of those of high residence time (n = 9).</p> <p>Results</p> <p>There were very few language translation problems; general question design defects and socio-cultural challenges to survey responses were more common. Problems were found for both acculturation and PA questions, with distinct problem types for the two question areas. Residence time/language group was weakly associated with overall frequency of problems observed: low residence time/Spanish (86%), high residence time/Spanish (67%), and English speaking groups (62%).</p> <p>Conclusions</p> <p>Standardized survey questions related to acculturation and physical activity present somewhat different cognitive challenges. For PA related questions, problems with such questions were similar regardless of subject residence time or language preference. For acculturation related questions, residence time/language or education level influenced responses to such questions. These observations should help in the interpretation of survey results for culturally diverse populations.</p

    The Science Performance of JWST as Characterized in Commissioning

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    This paper characterizes the actual science performance of the James Webb Space Telescope (JWST), as determined from the six month commissioning period. We summarize the performance of the spacecraft, telescope, science instruments, and ground system, with an emphasis on differences from pre-launch expectations. Commissioning has made clear that JWST is fully capable of achieving the discoveries for which it was built. Moreover, almost across the board, the science performance of JWST is better than expected; in most cases, JWST will go deeper faster than expected. The telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies.Comment: 5th version as accepted to PASP; 31 pages, 18 figures; https://iopscience.iop.org/article/10.1088/1538-3873/acb29

    Atrasentan and renal events in patients with type 2 diabetes and chronic kidney disease (SONAR): a double-blind, randomised, placebo-controlled trial

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    Background: Short-term treatment for people with type 2 diabetes using a low dose of the selective endothelin A receptor antagonist atrasentan reduces albuminuria without causing significant sodium retention. We report the long-term effects of treatment with atrasentan on major renal outcomes. Methods: We did this double-blind, randomised, placebo-controlled trial at 689 sites in 41 countries. We enrolled adults aged 18–85 years with type 2 diabetes, estimated glomerular filtration rate (eGFR)25–75 mL/min per 1·73 m 2 of body surface area, and a urine albumin-to-creatinine ratio (UACR)of 300–5000 mg/g who had received maximum labelled or tolerated renin–angiotensin system inhibition for at least 4 weeks. Participants were given atrasentan 0·75 mg orally daily during an enrichment period before random group assignment. Those with a UACR decrease of at least 30% with no substantial fluid retention during the enrichment period (responders)were included in the double-blind treatment period. Responders were randomly assigned to receive either atrasentan 0·75 mg orally daily or placebo. All patients and investigators were masked to treatment assignment. The primary endpoint was a composite of doubling of serum creatinine (sustained for ≥30 days)or end-stage kidney disease (eGFR <15 mL/min per 1·73 m 2 sustained for ≥90 days, chronic dialysis for ≥90 days, kidney transplantation, or death from kidney failure)in the intention-to-treat population of all responders. Safety was assessed in all patients who received at least one dose of their assigned study treatment. The study is registered with ClinicalTrials.gov, number NCT01858532. Findings: Between May 17, 2013, and July 13, 2017, 11 087 patients were screened; 5117 entered the enrichment period, and 4711 completed the enrichment period. Of these, 2648 patients were responders and were randomly assigned to the atrasentan group (n=1325)or placebo group (n=1323). Median follow-up was 2·2 years (IQR 1·4–2·9). 79 (6·0%)of 1325 patients in the atrasentan group and 105 (7·9%)of 1323 in the placebo group had a primary composite renal endpoint event (hazard ratio [HR]0·65 [95% CI 0·49–0·88]; p=0·0047). Fluid retention and anaemia adverse events, which have been previously attributed to endothelin receptor antagonists, were more frequent in the atrasentan group than in the placebo group. Hospital admission for heart failure occurred in 47 (3·5%)of 1325 patients in the atrasentan group and 34 (2·6%)of 1323 patients in the placebo group (HR 1·33 [95% CI 0·85–2·07]; p=0·208). 58 (4·4%)patients in the atrasentan group and 52 (3·9%)in the placebo group died (HR 1·09 [95% CI 0·75–1·59]; p=0·65). Interpretation: Atrasentan reduced the risk of renal events in patients with diabetes and chronic kidney disease who were selected to optimise efficacy and safety. These data support a potential role for selective endothelin receptor antagonists in protecting renal function in patients with type 2 diabetes at high risk of developing end-stage kidney disease. Funding: AbbVie

    The James Webb Space Telescope Mission

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    Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least 4m4m. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the 6.5m6.5m James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

    Revised diagnostic criteria for neurofibromatosis type 1 and Legius syndrome: an international consensus recommendation

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    Purpose By incorporating major developments in genetics, ophthalmology, dermatology, and neuroimaging, to revise the diagnostic criteria for neurofibromatosis type 1 (NF1) and to establish diagnostic criteria for Legius syndrome (LGSS). Methods We used a multistep process, beginning with a Delphi method involving global experts and subsequently involving non-NF experts, patients, and foundations/patient advocacy groups. Results We reached consensus on the minimal clinical and genetic criteria for diagnosing and differentiating NF1 and LGSS, which have phenotypic overlap in young patients with pigmentary findings. Criteria for the mosaic forms of these conditions are also recommended. Conclusion The revised criteria for NF1 incorporate new clinical features and genetic testing, whereas the criteria for LGSS were created to differentiate the two conditions. It is likely that continued refinement of these new criteria will be necessary as investigators (1) study the diagnostic properties of the revised criteria, (2) reconsider criteria not included in this process, and (3) identify new clinical and other features of these conditions. For this reason, we propose an initiative to update periodically the diagnostic criteria for NF1 and LGSS

    Alternative splicing and its regulatory mechanisms in photosynthetic eukaryotes

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    2011 Fall.Includes bibliographical references.In recent years, alternative splicing (AS) of pre-mRNAs, which generates multiple transcripts from a single gene, has emerged as an important process in general proteome diversity and in regulatory gene expression in multicellular eukaryotes. In Arabidopsis over 40% of intron-containing genes are alternatively spliced. However, mechanisms by which AS is regulated in plants are not fully understood, primarily due to the lack of an in vitro splicing system derived from plants. Furthermore, the extent of AS in simple unicellular photosynthetic eukaryotes from which plants have evolved is also not known. My research addresses these two attributes of splicing in plants. In Part 1 of my thesis, I have investigated an aspect of AS regulation in plants. We have previously shown that an SR-related splicing regulator called SR45 regulates AS of pre-mRNAs in Arabidopsis by altering splice site selection (Ali et al. 2007). In this work using bimolecular fluorescent complements, I have demonstrated that SR45 interacts with U2AF35, an important spliceosomal protein involved in 3' splice site selection in plant cells. This interaction takes place in the nucleus, specifically in the subnuclear domains called speckles, which are known to contain splicing regulators and other proteins involved in transcription. My work has shown that SR45 interacts with both paralogs of U2AF35 and I mapped the domains in SR45 that are involved in its interaction with U2AF35. In addition, my studies have revealed interaction of the paralogs as hetero- and homodimers. Interestingly, U2AF35 was found to interact with U1-70K, a key protein involved in 5' splice site selection. Based on this work and previous work in our laboratory, a model is proposed that explains the role of SR45 in splice site selection. In the second part of my work I studied the extent of alternative splicing (AS) in the unicellular green alga Chlamydomonas, that shares a common ancestor with land plants. In collaboration with Dr. Asa Ben Hur's lab, we have performed a comprehensive analysis of AS in Chlamydomonas reinhardtii using both computational and experimental methods. Our results show that AS is common in Chlamydomonas, but its extent is less than what is observed in land plants. However, the relative frequency of different splicing events in Chlamydomonas is very similar to higher plants. We have found that a large number of genes undergo alternative splicing, and together with the simplicity of the system and the use of available molecular and genetic tools. This organism is an experimental system to investigate the mechanisms involved in alternative splicing. To further validate predicted splice variants, we performed extensive analysis of AS for two genes, which not only confirmed predictions but also revealed novel splice variants, suggesting that the extent of AS is higher than we predicted. AS can also play a role in the regulation of gene expression through processes such as regulated unproductive splicing and translation (RUST) that involves nonsense-mediated decay (NMD), a mechanism of mRNA surveillance that degrades transcripts containing premature termination codons (PTCs). The basic mechanism of NMD relies upon many factors, but there are three critical proteins, termed the UP-frameshift (UPF) proteins due to their ability to up-regulate suppression of nonsense transcripts. UPF1, UPF2, and UPF3 appear to be conserved across animals and plants. Our analysis of AS has found that in Chlamydomonas, many splice variants have a premature termination codon (PTC). However, to date, the mechanism of NMD has not been investigated in Chlamydomonas. Analysis of the Chlamydomonas genome sequence shows that UPF1, 2, and 3 proteins are present, and we have shown that they share some sequence similarity with both plants and humans, indicating that the process of NMD may be present in this organism. To address the role of UPFs in NMD in Chlamydomonas, we have utilized the artificial miRNA approach. I have generated stably transformed Chlamydomonas cell lines that are expressing amiRNA for UPF1 and UPF3 that will be useful in analyzing NMD of selected genes as well as all PTC-containing transcripts globally
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