This Week in Science

Science  21 Nov 2014:
Vol. 346, Issue 6212, pp. 960
  1. Geomorphology

    Tibetan gorge avoids a tectonic aneurysm

    1. Brent Grocholski

    Tsangpo Gorge, Tibet

    PHOTO: FENG WEI PHOTOGRAPHY/GETTY IMAGES

    Rapid tectonic uplift was responsible for the immense Tsangpo Gorge on the eastern edge of the Tibetan plateau 2.5 million years ago. Wang et al. found a buried canyon upstream from the gorge along the Yarlung Tsangpo River that began filling with sediments after sudden uplift. Drill cores of the buried canyon sediments show the same river gradient as found downstream of the gorge. The constant river gradient strongly suggests a rapid uplift event created the gorge, rather than river incision as previously believed.

    Science, this issue p. 978

  2. Chromosomes

    A cohesin ring around two DNA strands

    1. Guy Riddihough

    Holding together homologous sister chromosome pairs is a vital requirement during cell division and DNA repair. A special complex, called cohesin, forms a ring made of three different proteins and functions to hold together the two sister DNA strands. Gligoris et al. and Huis in 't Veld et al. identified a specific protein-protein interface within the cohesin ring that forms a DNA exit gate. Mutations in this interface prevented cohesion between sister chromatids. Thus, the cohesin ring must indeed encircle the two DNA strands to hold them together.

    Science, this issue p. 963, p. 968

  3. Optics

    Compensating optical loss for laser gain

    1. Ian S. Osborne

    Optical loss is thought to be detrimental to the operation of a laser, typically resulting in poor beam quality, multimode emission, and low efficiencies. Now results that take their cue from theoretical ideas of parity-time symmetry and implement them into the design of coupled laser components show that loss and gain can actually work together. Feng et al. and Hodaei et al. designed laser systems based on microring cavities to carefully control the amount of loss and gain within each component. The interplay between the loss and gain resulted in enhanced and cleaner emission from their lasers.

    Science, this issue p. 972, p. 975

  4. Liquid Structure

    Containing the nuclear elephant's foot

    1. Brent Grocholski

    Molten nuclear fuel composed of large amounts of uranium dioxide is extremely dangerous. Liquid UO2 has a high melting temperature and is very reactive, making it difficult to find a suitable sample container within which to study it. Skinner et al. bypassed the container and used instead a laser to heat beads of UO2 levitated in a synchrotron x-ray beam with inert gas. They found an unexpected increase in the fluidity of molten nuclear fuel caused by a fall in the number of oxygen atoms surrounding each uranium cation. These findings are important when considering how to contain nuclear fuel during an accident.

    Science, this issue p. 984

  5. Ebola Epidemiology

    Recharging Ebola mitigation measures

    1. Caroline Ash

    Effective drugs and vaccines for Ebola virus are not available, so what can be done? Pandey et al. used a mathematical model to analyze transmission in different scenarios: the community, hospitals, and at funerals. Achieving full compliance with any single control measure, such as case isolation, is impossible under prevailing conditions. However, with a minimum of 60% compliance, a combination of case isolation, hygienic burial, and contact tracing could reduce daily case numbers to single figures in 5 to 6 months. Success will also require persistence and sensitivity to local customs.

    Science, this issue p. 991

  6. Tuberculosis

    Using a diabetes drug to treat tuberculosis

    1. Angela Colmone

    The increasing prevalence of drug-resistant strains of Mycobacterium tuberculosis—the bacterium that causes tuberculosis (TB)—has led to a paradigm shift in the search for new drugs. Rather than targeting the bacterium itself, researchers are trying to augment host defenses. Now, Singh et al. report that the FDA-approved drug metformin, currently used to treat type 2 diabetes, can improve the immune response to M. tuberculosis infection. Metformin inhibited the growth of M. tuberculosis by enhancing specific immune responses in vitro and in infected mice. Furthermore, in human diabetic patients with TB, metformin treatment decreased TB severity.

    Sci. Transl. Med. 6, 263ra159 (2014).

  7. Exoplanet Magnetism

    Transit marked by magnetosphere effects

    1. Margaret M. Moerchen

    Transit observations of an exoplanet reveal its atmospheric and magnetic properties

    CREDIT: EUROPEAN SPACE AGENCY/ALFRED VIDAL-MADJAR/INSTITUT D'ASTROPHYSIQUE DE PARIS/CNRS, FRANCE/NASA

    Life on Earth exists under the protective sheath of our magnetosphere that deflects charged particles blown out by the Sun. Kislyakova et al. calculated the strength of the magnetic field of a well-studied hot-Jupiter–type exoplanet that produces similar effects. During the planet's transit in front of its host star, HD 209458, hydrogen atoms leave a peculiar asymmetric signature in the transmitted spectrum.

    Science, this issue p. 981

  8. Metabolism

    Making the brain promote fat loss in mice

    1. Wei Wong

    Obesity is a growing global problem associated with diabetes and metabolic syndrome. Signals from the brain regulate whole body metabolism and can trigger adipose tissue to burn fat. Perino et al. found that mice that expressed catalytically inactive forms of two phosphoinositide 3-kinases (PI3Kβ and PI3Kγ) were leaner, burned more fat, and expended more energy than normal mice. Fat loss also occurred in mice that received inhibitors of PI3Kβ and PI3Kγ delivered specifically into the brain. Thus, drugs that block these enzymes in the brain could potentially help to fight obesity.

    Sci. Signal. 7, ra110 (2014).

  9. Influenza Immunology

    Hills and valleys of influenza infection

    1. Caroline Ash

    Each one of us may encounter several different strains of the ever-changing influenza virus during a lifetime. Scientists can now summarize such histories of infection over a lifetime of exposure. Fonville et al. visualize the interplay between protective responses and the evasive influenza virus by a technique called antibody landscape modeling (see the Perspective by Lessler). Landscapes reveal how exposure to new strains of the virus boost immune responses and indicate possibilities for optimizing future vaccination programs.

    Science, this issue p. 996; see also p. 919

  10. Ebola Mouse Model

    Variety of Ebola symptoms in mice

    1. Caroline Ash

    Apart from monkeys, there are no animal models available that show the same symptoms of Ebola virus infection as those of humans. Rasmussen et al. tested the effects of Ebola virus in mice with defined genetic backgrounds in a series of pains-taking experiments performed under stringent biosafety conditions. Resistance and susceptibility to Ebola virus was associated with distinct genetic profiles in inflammation, blood coagulation, and vascular function. This panel of mice could prove valuable for preliminary screens of candidate therapeutics and vaccines.

    Science, this issue p. 987

  11. Inflammation

    HIV drugs can dampen inflammation, too

    1. Kristen L. Mueller

    Nucleoside reverse transcriptase inhibitors (NRTIs) stop HIV in its tracks by blocking reverse transcription, a process critical for HIV to replicate its genome. Fowler et al. found that in mice, these drugs also block inflammation caused by a large protein complex called the NLRP3 inflammasome. This activity is independent of the drugs' ability to block reverse transcription. Instead, the drugs block the activity of the ion channel P2X7, which activates the NLRP3 inflammasome. NRTIs improved outcomes in several NLRP3 inflammasome-dependent mouse models of inflammation, including age-related macular degeneration and graft-versus-host disease.

    Science, this issue p. 1000

  12. Hox Loci Regulation

    Similar regulation of digit and genital development

    1. Beverly A. Purnell

    Hox proteins help set up the vertebrate and invertebrate body plan and also specify segment identity, such as leg versus antennae. Lonfat et al. examined Hox gene regulation in mouse limb and genitals. Although the limb and genitals have widely differing structure and function, they display common features for Hox regulation during development. Transcription at these anatomical sites depends upon gene enhancers within a shared chromatin topological domain. It is likely that this regulatory landscape provided genomic niches for enhancer evolution.

    Science, this issue p. 1004

  13. Mouse Genomics

    Rewiring the gene regulatory landscape

    1. Laura M. Zahn

    DNAse I hypersensitive sites (DHSs) correlate with genomic locations that control where messenger RNA is to be produced. DHSs differ, depending on the cell type, developmental stage, and species. Vierstra et al. compared mouse and human genome-wide DHS maps. Approximately one-third of the DHSs are conserved between the species, which separated approximately 80 million years ago. Most DHSs fell into tissue-specific cohorts; however, these were generally not conserved between the human and mouse. It seems that the majority of DHSs evolve because of changes in the sequence that gradually change how the region is regulated.

    Science, this issue p. 1007

  14. Aging

    How a fungus can live for centuries

    1. Julia Fahrenkamp-Uppenbrink

    Some species of fungi and plants can live for a thousand years or more. How do these species avoid harmful mutations over these long time spans? In a Perspective, Aanen highlights a recent study that reports extremely low genetic variation in an individual of a long-lived fungus. The manner in which stem cells divide differs between fungi, plants, and animals. These differences may allow certain fungi and plants to avoid accumulation of harmful mutation s at the growth front, enabling them to grow particularly old.

    Science, this issue p. 922

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