This Week in Science

Science  09 Oct 2015:
Vol. 350, Issue 6257, pp. 173
  1. Virology

    Orchestrating a viral takeover

    1. Kristen L. Mueller

    New dengue virus strains emerge by reducing host immunity

    PHOTO: SCIENCE PICTURE CO/SCIENCE SOURCE

    For some pathogenic viruses, outbreaks occur when a new viral strain emerges and displaces the endemic strain. How such a takeover occurs at a molecular level, however, remains an open question. Manokaran et al. examined one example, the emergence of a new clade of dengue virus (DENV) that caused an outbreak in Puerto Rico in 1994. The epidemic strain produced elevated amounts of subgenomic flavivirus RNA (sfRNA), a viral noncoding RNA, relative to amounts of genomic viral RNA. sfRNA bound to and inhibited TRIM25, a protein important for activating the host's antiviral response, and so by reducing host immunity was able to increase its own fitness.

    Science, this issue p. 217

  2. Geomorphology

    The glacial way of wearing away

    1. Brent Grocholski

    The rate at which glaciers erode landscapes is an important but poorly constrained relationship. Herman et al. tackle this issue by considering the Franz Josef alpine glacier in New Zealand. The amount of sediment piling up at the edge of the glacier provided erosion rates, whereas remote sensing allowed for simultaneous tracking of glacial motion. The result was a nonlinear relationship, suggesting that fast glaciers are much more effective at gouging landscapes. This could explain the paradox of why long-term erosion rates are so much lower in polar regions with more permanent glaciers.

    Science, this issue p. 193

  3. Frustrated Magnetism

    Elucidating order within disorder

    1. Jelena Stajic

    In some materials, the geometry of the crystal lattice gets in the way of magnetic ordering. Their spins, although magnetically interacting, remain seemingly disordered and form a so-called spin liquid. Paddison et al. propose a different model for the spin-liquid compound Gd3Ga5O12. Neutron diffraction measurements and numerical techniques revealed that even though individual spins in this material were disordered, they formed 10-spin loops that were correlated with one another. The nature of this “hidden order” was such that it escaped direct detection by conventional techniques

    Science, this issue p. 179

  4. Surface Chemistry

    Comparing active site reactivity

    1. Phil Szuromi

    Noble metal nanoparticles often exhibit behaviors distinct from atomic and bulk versions of the same material. Gold and platinum dispersed on metal oxide supports, for example, show remarkable low-temperature reactivity for carbon monoxide (CO) oxidation by oxygen or water. Ding et al. used infrared spectroscopy to identify CO adsorbed on isolated platinum atoms or nanoparticles dispersed on zeolite and oxide supports. Temperature-programmed desorption studies showed that CO reacted at much lower temperatures when adsorbed on nanoparticles versus on isolated metal atoms.

    Science, this issue p. 189

  5. Plant Science

    Secondary cell walls built with speed

    1. Pamela J. Hines

    Plant cell walls provide the cellulose that is integral for wood, cotton fiber, and many biofuels. Cellulose is synthesized outside the cell membrane by cellulose synthase enzymes. Much of the secondary cell wall, responsible for the sturdiness of wood, is formed by xylem cells embedded in the core of the plant. Watanabe et al. leveraged ectopic expression to bring xylem-style cellulose synthase activity to the epidermal surface of the plant (see the Perspective by Schneider and Persson). Combining this improved accessibility with fluorescent tagging showed that secondary cell walls are built faster than primary cell walls, perhaps due to increased velocity and density of cellulose synthase complexes.

    Science, this issue p. 198, see also p. 156

  6. Astrophysics

    Evidence of a universal physics of accretion

    1. Kip Hodges

    From nascent stars to supermassive black holes, most objects in the universe grow by the gradual accretion of material. One important signature of the accretion process is the amplitude of variability in the brightness of energy emitted from an astrophysical object. Scaringi et al. demonstrated that brightness variabilities of accreting white dwarfs and young stellar objects obey the same functional relationships with respect to brightness. Previously, these same functional relationships have been shown to hold for much larger objects, including supermassive black holes, implying a universality of the physics of accretion.

    Science Adv. 10.1126.sciadv.1500686 (2015).

  7. Education

    A little bit of math goes a long way

    1. Pamela J. Hines

    Children's emerging language skills are supported when their caregivers read to them at home. Math skills, however, are often relegated to the schools. Berkowitz et al. developed a mobile-device app designed to help caregivers bring a little bit of math into the home. Improved math skills were apparent within months for elementary school students. Improvements were most dramatic in families where the caregivers reported themselves to be anxious about math.

    Like reading, caregivers can help children improve their math skills away from school

    PHOTO: ©GARETH BROWN/CORBIS

    Science, this issue p. 196

  8. Oncology

    Is cancer immunotherapy a private affair?

    1. Paula A. Kiberstis

    Immune checkpoint blockade, a relatively new cancer treatment, substantially extends the survival of a subset of patients. Previous work has shown that patients whose tumors harbor the largest number of mutations—and thus produce a large number of “neoantigens” recognized as foreign by the immune system—are most likely to benefit. Expanding on these earlier studies, Van Allen et al. studied over 100 patients with melanoma and found a similar correlation (see the Perspective by Gubin and Schreiber). There was no evidence, however, that specific neoantigen sequences were shared by patients who responded.

    Science, this issue p. 207, see also p. 158

  9. Transplantation

    Blocking a fatal punch

    1. Angela Colmone

    Bone marrow transplantation replaces unhealthy bone marrow with that of a healthy donor. But donor-derived immune cells might recognize the transplant recipient as foreign and attack, resulting in graft-versus-host disease (GVHD). Zhang et al. report that blocking the suppression of tumorigenicity 2 protein (sST2), a serum marker for GVHD, with a neutralizing antibody reduces GVHD severity and mortality. The blockade decreased the production of proinflammatory cytokines and increased the frequency of anti-inflammatory molecules and cells while maintaining graft-versus-leukemia activity. Targeting sST2 might therefore decrease GVHD after bone marrow transplantation.

    Sci. Transl. Med. 7, 308ra160 (2015).

  10. Martian Geology

    Ancient lake system at Gale crater

    1. Nicholas S. Wigginton

    Since 2012, the Curiosity rover has been diligently studying rocky outcrops on Mars, looking for clues about past water, climate, and habitability. Grotzinger et al. describe the analysis of a huge section of sedimentary rocks near Gale crater, where Mount Sharp now stands (see the Perspective by Chan). The features within these sediments are reminiscent of delta, stream, and lake deposits on Earth. Although individual lakes were probably transient, it is likely that there was enough water to fill in low-lying depressions such as impact craters for up to 10,000 years. Wind-driven erosion removed many of these deposits, creating Mount Sharp.

    Science, this issue p. 10.1126/science.aac7575, see also p. 167

  11. Nanoparticles

    Solutions for nanoparticle solutions

    1. Phil Szuromi

    Nanoparticle interactions in solution affect their binding to biomolecules, their electronic properties, and their packing into larger crystals. However, the theories that describe larger colloidal particles fail for nanoparticles, because the interactions do not add together linearly. Nanoparticles also have complex shapes and are closer in size to the solvent molecules. Silvera Batista et al. review approaches that can treat the nonadditive nature of nanoparticle interactions, resulting in a more complete understanding of nanoparticles in solution.

    Science, this issue 10.1126/science.1242477

  12. Structural Biology

    Opening up Vps34 protein complexes

    1. Stella M. Hurtley

    During intracellular membrane trafficking, large protein complexes regulate and adapt the activity of signal transducer enzymes such as the class III phosphatidylinositol 3-kinase Vps34. These large enzyme complexes are present in all eukaryotic cells, having widespread importance in neurodegeneration, aging, and cancer; however, a structural understanding has been lacking. Rostislavleva et al. provide atomic-resolution insights into the structures of the Vps34-containing protein complexes required for autophagy, endocytic sorting, and cytokinesis. The V-shaped complexes can undergo opening motions, which allows them to adapt to and phosphorylate membranes.

    Science, this issue p. 10.1126/science.aac7365

  13. History of Science

    Mendel, revisited

    1. Julia Fahrenkamp-Uppenbrink

    150 years ago, Gregor Mendel was getting ready to publish his work on dominant and recessive traits of pea varieties. The work was forgotten until the turn of the 20th century, when Mendel was recognized as the father of genetics. Some scientists concluded that Mendel's data were “too good to be true,” but concerns over possible data manipulation have proved to be unfounded. Yet as Radick discusses in a Perspective, the debate over potential fraud has dominated critical discussions of Mendel's work. Broader critiques of Mendel's legacy should, for example, take a closer look at his binary inheritance categories, which do not allow for the diversity of inherited characters.

    Science, this issue p. 159

  14. Cancer

    Killing cancer cells with aggregates

    1. Leslie K. Ferrarelli

    The drug verteporfin, which is used clinically to enhance phototherapy, may also be useful as a cancer chemotherapeutic. Zhang et al. show that verteporfin triggered the accumulation of protein oligomers that selectively killed colorectal cancer cells in mice and in cells cultured in hypoxic and nutrient-deprived conditions (see the Focus by Avril and Chevet). Normal cells in culture and in tumor-adjacent tissue sections from mice cleared these aggregates through autophagy and survived. Verteporfin thus produces tumor-selective proteotoxicity, which may be a useful therapeutic for patients with solid tumors.

    Sci. Signal. 8, ra98 and fs17 (2015).

  15. Topological Matter

    Handedness at the edge of a line

    1. Jelena Stajic

    Topological insulators are characterized by conducting boundary states. For those existing as two-dimensional (2D) materials, the boundaries are lines, the edge currents are 1D, and their two spin components flow in opposite directions. To address whether this handedness also applies to the edge states of 1D topological systems, Cheon et al. deposited indium atoms on the surface of silicon, where the atoms formed wires consisting of double zigzag chains. The chains underwent distortions that caused topological edge states called solitons to appear under certain conditions. The solitons came in three flavors, two of which had a definite handedness.

    Science, this issue p. 182

  16. Surface Chemistry

    Accounting for surface coordination

    1. Phil Szuromi

    The exploration of heterogeneous catalysts using first-principles calculations can be daunting because the large number of atoms and possible surface geometries. Calle-Vallejo et al. describe a simpler metric for assessing optimal reactivity: a weighted average of surface coordination that includes second-nearest neighbors (see the Perspective by Stephens et al.). The calculations identified three approaches for introducing cavity sites into the platinum(111) surface to improve its performance for the oxygen reduction reaction used in fuel cells.

    Science, this issue p. 185, see also p. 164

  17. Oncogene Signaling

    Cancer as a case of uncontrolled traffic

    1. Paula A. Kiberstis

    Healthy cells are like skilled air traffic controllers. They continually move proteins to and from the cellular destinations where they are needed, usually without mishap, through an elaborate system of endomembranes. Wheeler et al. show that a glitch in the traffic control system can help propel a cell toward malignancy (see the Perspective by Ferguson). RAB35, a protein previously implicated in endomembrane trafficking, is a key regulator of a well-known oncogenic signaling pathway. Mutations in RAB35 found in certain human tumors aberrantly activate this pathway and cause mislocalization of a factor that promotes cell growth.

    Science, this issue p. 211, see also p. 162

  18. Plant Science

    Striga uses a hypersensitive receptor

    1. Pamela J. Hines

    The strigolactone hormones govern plant growth and development. A nasty parasitic weed, Striga, senses traces of these hormones to identify its targets. After functionally characterizing several strigolactone receptors from Striga, Toh et al. solved the crystal structure of one that is especially sensitive. The structure shows an unexpectedly large ligand-binding pocket, which may explain how Striga manages to sense picomolar concentrations of the range of strigolactones.

    Science, this issue p. 203