This Week in Science

Science  05 Oct 2018:
Vol. 362, Issue 6410, pp. 41
  1. Geomorphology

    A sudden outburst of erosion

    1. Brent Grocholski

    Boulder-filled channel near the eastern margin of the Tibetan Plateau, a setting similar to the Bhotekoshi River

    CREDIT: NIELS HOVIUS

    Glacial lake outburst floods (GLOFs) are exactly what they sound like. The sudden emptying of a glacial lake in high-topography regions like the Himalaya can quickly destroy everything in its path. Cook et al. intercepted a GLOF in the Bhotekoshi and Sunkoshi river valleys in central Nepal as they were monitoring the region in the aftermath of the 2015 Gorkha earthquake. They found that a massive amount of erosion occurred during the outburst flood, which suggests that GLOFs may be the primary factor in landscape evolution for these regions.

    Science, this issue p. 53

  2. Superconductivity

    Conspiring interactions in a cuprate

    1. Jelena Stajic

    More than 30 years after the discovery of high-temperature superconductivity in copper oxides, its mechanism remains a mystery. Electron pairing mediated solely by lattice vibrations—phonons—is thought to be insufficient to account for the high transition temperatures. He et al. found a rapid and correlated increase of the superconducting gap and electron-phonon interactions as the chemical composition of their bismuth-based cuprate samples was varied across a critical doping concentration. The interplay of electron-phonon with electron-electron interactions may lead to enhanced transition temperatures.

    Science, this issue p. 62

  3. Adaptive Radiations

    Secrets revealed by kangaroo teeth

    1. Sacha Vignieri

    The teeth of mammals display complex adaptations to diet and can thus provide a window into the environments of extinct species. Couzens and Prideaux used such a window to examine the expansion and diversification of kangaroos, Australia's largest herbivores (see the Perspective by Polly). True kangaroos diversified not in response to drying in the Miocene, as suggested by molecular results, but rather as grasslands expanded during the Pliocene. Furthermore, the now-extinct short-faced kangaroos were not declining because of increases in aridity at the end of the Pleistocene but instead were experiencing an increase in dietary divergence.

    Science, this issue p. 72; see also p. 25

  4. Influenza

    Seasonal flu by ZIP code

    1. Caroline Ash

    Influenza virus strikes communities in northern latitudes during winter, straining health care provision almost to the breaking point. Change in environmental humidity is a key driver, but many other seasonal and social factors contribute. Dalziel et al. obtained a geographical distribution of doctor visits for influenza-like illness for more than 600 U.S. cities (see the Perspective by Wallinga). Some ZIP codes regularly experienced sharply defined peaks of cases, or intense epidemics, and others showed a longer, more diffuse influenza season. The surges tended to occur in smaller cities with less residential density and lower household incomes. Larger, more densely populated cities had more-diffuse epidemics, presumably because of higher rates of personal contact, which makes influenza transmission less subject to climate variation.

    Science, this issue p. 75; see also p. 29

  5. Economics

    Educating for economic rationality

    1. Andrew M. Sugden

    The hypothesis that education enhances economic decision-making has been surprisingly underexplored. Kim et al. studied this question using a randomized control trial in a sample of 2812 girls in secondary schools in Malawi. Four years after providing financial support for a year's schooling, they presented the subjects with a set of decision problems (for example, allocating funds to immediate versus future expenses) that test economic rationality. The education intervention enhanced both educational outcomes and economic rationality as measured by consistency with utility maximization in the long run.

    Science, this issue p. 83

  6. Muscle Disease

    Gene editing and muscular dystrophy

    1. Paula A. Kiberstis

    Duchenne muscular dystrophy (DMD) is characterized by progressive muscle weakness and a shortened life span. The disease is caused by mutations that reduce or prevent expression of dystrophin, an essential structural protein in skeletal and heart muscle. The gene editing technology CRISPR-Cas9 can correct disease-causing mutations and has yielded promising results in mouse models of DMD. In a small, short-term study, Amoasii et al. tested this strategy in a dog model of DMD that exhibits many features of the human disease. Intramuscular or systemic delivery of the gene editing components resulted in a substantial increase in dystrophin protein levels in skeletal and heart muscle. Restoration of dystrophin expression was accompanied by improved muscle histology.

    Science, this issue p. 86

  7. Astronomy

    New moon rising

    1. Kip Hodges

    Although the existence of exomoons—moons orbiting extrasolar planets—is probable, direct observational evidence has been elusive. Previous observations made using NASA's Kepler space telescope suggested that Kepler-1625b, a Jupiter-sized planet orbiting the solar-mass yellow star Kepler-1625, may be orbited by an exomoon. Now, Teachey and Kipping report additional observations made using the Hubble Space Telescope, as well as a refined analysis of Kepler photometry data, that strongly support the exomoon hypothesis. This moon, if it exists, would be similar in size to Neptune or Uranus in our own Solar System.

    Sci. Adv. 10.1126/sciadv.aav1784 (2018).

  8. HIV

    Gut check for a promising HIV treatment

    1. Lindsey Pujanandez

    Eradicating HIV in infected patients likely requires disrupting the reservoir of infected T cells in the gastrointestinal tract. One approach may be targeting cells expressing the integrin α4β7, which has been tested in simian immunodeficiency virus models and is an approved therapy for inflammatory bowel disease. Uzzan et al. studied a small cohort of HIV-infected individuals on antiretroviral therapy who began receiving an antibody against α4β7 as a treatment for their mild inflammatory bowel disease. Longitudinal colonoscopies revealed that the anti-α4β7 therapy disrupted local lymphoid aggregates. The treatment was well tolerated, but long-term effects on the HIV reservoir remain to be determined.

    Sci. Transl. Med. 10, eaau4711 (2018).

  9. Gas Giant Planets

    Cassini's final phase of exploration

    1. Keith T. Smith

    The Cassini spacecraft spent 13 years orbiting Saturn; as it ran low on fuel, the trajectory was changed to sample regions it had not yet visited. A series of orbits close to the rings was followed by a Grand Finale orbit, which took the spacecraft through the gap between Saturn and its rings before the spacecraft was destroyed when it entered the planet's upper atmosphere. Six papers in this issue report results from these final phases of the Cassini mission. Dougherty et al. measured the magnetic field close to Saturn, which implies a complex multilayer dynamo process inside the planet. Roussos et al. detected an additional radiation belt trapped within the rings, sustained by the radioactive decay of free neutrons. Lamy et al. present plasma measurements taken as Cassini flew through regions emitting kilometric radiation, connected to the planet's aurorae. Hsu et al. determined the composition of large, solid dust particles falling from the rings into the planet, whereas Mitchell et al. investigated the smaller dust nanograins and show how they interact with the planet's upper atmosphere. Finally, Waite et al. identified molecules in the infalling material and directly measured the composition of Saturn's atmosphere.

    Science, this issue p. eaat5434, p. eaat1962, p. eaat2027, p. eaat3185, p. eaat2236, p. eaat2382

  10. Structural Biology

    It takes two to signal

    1. Valda Vinson

    The Hedgehog (HH) signaling pathway is important in development, and excessive HH signaling is associated with cancer. Signaling occurs through the G protein–coupled receptor Smoothened. The pathway is repressed by the membrane receptor Patched-1 (PTCH1), and this inhibition is relieved when PTCH1 binds the secreted protein HH. Two recent papers have described structures of HH bound to PTCH1, but surprisingly, each described a different binding epitope on HH. Qi et al. present a cryo–electron microscopy structure that explains this apparent contradiction by showing that a single HH protein uses both of these interfaces to engage two PTCH1 receptors (see the Perspective by Sommer and Lemmon). Functional assays suggest that both interfaces must be bound for efficient signaling.

    Science, this issue p. eaas8843; see also p. 26

  11. Geophysics

    Detailing subduction zones

    1. Brent Grocholski

    Subduction zones are responsible for the most-damaging and tsunami-generating great earthquakes. Hayes et al. updated their Slab1.0 model to include all seismically active subduction zones, including geometrically complex regions like the Philippines. The new model, Slab2, details the geometry of 24 million square kilometers of subducted slabs, from ocean trench to upper mantle. The model will be vital for fully understanding seismic hazard in some of the most populated regions in the world.

    Science, this issue p. 58

  12. Solid-State Physics

    Insulator or a metal?

    1. Jelena Stajic

    When a metal is cooled to low temperatures and placed in an external magnetic field, its resistivity may oscillate as the magnitude of the field is varied. Seeing these so-called quantum oscillations in an insulating material would be very unusual. Xiang et al. report such findings in the insulator ytterbium dodecaboride (YbB12) (see the Perspective by Ong). In addition to oscillations in resistivity, the authors observed oscillations in the magnetic torque. The results present a challenge to theories that aim to explain the insulating state of YbB12.

    Science, this issue p. 65; see also p. 32

  13. Plasmonic Chemistry

    Hot carriers reducing thermal barriers

    1. Phil Szuromi

    Plasmonic catalysts can generate hot charge carriers that can activate reactants and, in turn, reduce the overall barrier to a reaction. Zhou et al. studied the decomposition of ammonia to hydrogen on a copper alloy nanostructure that absorbed light and generated electrons that activated nitrogen atoms on ruthenium surface atoms (see the Perspective by Cortés). By measuring reaction rates at different wavelengths, light intensities, and catalyst surface temperatures, the light-induced reduction of the apparent activation barrier was quantified.

    Science, this issue p. 69; see also p. 28

  14. Forest Ecology

    Tree diversity improves forest productivity

    1. Andrew M. Sugden

    Experimental studies in grasslands have shown that the loss of species has negative consequences for ecosystem functioning. Is the same true for forests? Huang et al. report the first results from a large biodiversity experiment in a subtropical forest in China. The study combines many replicates, realistic tree densities, and large plot sizes with a wide range of species richness levels. After 8 years of the experiment, the findings suggest strong positive effects of tree diversity on forest productivity and carbon accumulation. Thus, changing from monocultures to more mixed forests could benefit both restoration of biodiversity and mitigation of climate change.

    Science, this issue p. 80

  15. Cancer

    Some (re)programming notes on cancer

    1. Paula A. Kiberstis

    Epithelial cancers develop resistance to targeted therapies in a number of different ways. Several cancer types do so by undergoing phenotypic conversion to a highly aggressive cancer called small cell neuroendocrine carcinoma (SCNC). Whether distinct cancer types accomplish this “reprogramming” through the same mechanism has been unclear. Park et al. show that the same set of oncogenic factors transforms both normal lung and normal prostate epithelial cells into SCNCs that resemble clinical samples (see the Perspective by Kareta and Sage). This convergence of molecular pathways could potentially simplify the development of new therapies for SCNC, which is currently untreatable.

    Science, this issue p. 91; see also p. 30

  16. Microbiology

    Industrialization reduces microbiota diversity

    1. Gemma Alderton

    Disturbances in the microbiota that live on or in the human body are associated with various diseases. In a Perspective, Dominguez Bello et al. propose that a reduction in microbiota diversity associated with modern, industrialized living is linked to the increasing incidence of metabolic, immune, and cognitive diseases. They propose that microbiota samples should be collected from individuals in traditional societies. These could potentially be used to reinstate microbiota ecology, which might help to prevent and/or treat modern diseases.

    Science, this issue p. 33

  17. Infectious Diseases

    Turning the tables on interferon

    1. Ifor Williams

    An early step in the host response to viral infection involves a burst of synthesis of type I interferons that allow cells to quickly fight back against the offending viruses. Shaabani et al. investigated how the same interferon-stimulated genes (ISGs) that usually help against viruses surprisingly dampen the host's ability to resist many bacterial infections. Deletion of a single ISG called Usp18 in mouse dendritic cells was sufficient to enhance host control of infections with two strains of Gram-positive bacteria. Normal induction of USP18 after infection impaired antibacterial responses mediated by tumor necrosis factor. USP18 thus represents a potential therapeutic target for control of serious bacterial infections.

    Sci. Immunol. 3, eaau2125 (2018).

  18. Biochemistry

    How Vibrio disrupts Ras signaling

    1. Annalisa M. VanHook

    Many pathogenic bacteria, including Vibrio vulnificus, target the small guanosine triphosphatase Ras because it is critical for signaling pathways that control host cell biology and innate defenses. Biancucci et al. solved the crystal structure of RRSP, a toxin effector domain from V. vulnificus that cleaves KRAS, a member of the Ras family. Cleavage by RRSP did not release any fragments but structurally altered KRAS so that it could not bind to its downstream effector Raf. These findings may prove useful for developing strategies to inhibit Ras proteins that are aberrantly activated in tumors.

    Sci. Signal. 11, eaat8335 (2018).