This Week in Science

Science  02 Sep 2016:
Vol. 353, Issue 6303, pp. 1000
  1. Speech Processing

    Language representation in the dog brain

    1. Peter Stern

    Dogs' brains integrate praise words with their owners' intonation.

    PHOTO: TIERFOTOAGENTUR/ALAMY STOCK PHOTO

    Dogs have been domesticated for many thousands of years. Humans and dogs have thus had plenty of time to develop close communication bonds for work and play. Using brain-scanning techniques, Andics et al. investigated how dogs process human speech. The left brain hemisphere in dogs responds more strongly to praise words, and a right auditory brain region distinguishes intonation. Reward regions only light up if both the word and the intonation are consistent with praise. Hence, the subtlety of dog-human communication has become hardwired in the absence of language.

    Science, this issue p. 1030

  2. Dengue Vaccine

    Discerning dengue vaccine protection

    1. Caroline Ash

    Clinical trials of the Sanofi-Pasteur dengue vaccine have not been an unmixed success because of complex immune interactions between dengue subtypes. Ferguson et al. analyzed data from the published phase III clinical trials to work out how best to deploy the vaccine and minimize the risk of enhancing disease. Vaccination has the same immunological effect as a silent natural infection: It boosts protection in people who are seropositive but puts naïve individuals at risk of the potentially severe effects of subsequent natural infection. Thus, routine vaccination success critically depends on the proportion of the target group that has experienced prior dengue infections.

    Science, this issue p. 1033

  3. Neurodevelopment

    Signposts for synapses

    1. Pamela J. Hines

    Brain development entails not only positioning the neurons in the right place but also building the correct connections for functional circuits. In the early postnatal mouse brain, Oh et al. discovered how the exact locations for synapse development are specified. The neurotransmitter GABA (γ-aminobutyric acid) induces the formation of dendritic spines, accumulation of anchoring sites, and subsequent recruitment of GABA receptors. Thus, the release of GABA, usually known as an inhibitory neurotransmitter in the adult brain, serves in the developing brain to determine just where synapses are built.

    Science, this issue p. 1037

  4. Ion Channels

    Snapshots of a potassium channel

    1. Valda Vinson

    Potassium channels help maintain the appropriate charge difference between the inside and the outside of a cell. The channel's selectivity for potassium is imparted by a pore so narrow that potassium ions must pass in single file. How potassium ions move through this pore is much debated. Kratochvil et al. obtained instantaneous snapshots of ions in the pore by using ultrafast two-dimensional infrared spectroscopy. It appears that, like beads on a string, potassium ions and water molecules occupy alternating binding sites in the channel.

    Science, this issue p. 1040

  5. HIV-1 Antibodies

    How antibodies protect against HIV-1

    1. Kristen L. Mueller

    A protective vaccine is a major goal in HIV-1 prevention. Such a vaccine needs to elicit neutralizing antibodies to block infection. To understand mechanisms of protection by neutralizing antibodies, Liu et al. first treated rhesus macaques with an antibody known to block infection, then infected them with a monkey-adapted HIV-1. Subsequently, viral DNA and RNA were found in the macaques' gut and lymph nodes a few days after genital tract infection. This suggests that antibodies may block the virus in multiple sites throughout the body, rather than just at the site of entry.

    Science, this issue p. 1045

  6. Immunology

    Divergent responses, same receptor

    1. John F. Foley

    Macrophages detect infection or tissue injury with pattern recognition receptors, including the Toll-like receptors (TLRs). Piccinini et al. investigated how macrophages react to the bacterial product lipo-polysaccharide (LPS) and the extracellular matrix component tenascin-C, both of which stimulate TLR4. Although both stimuli activated some common signaling pathways, LPS stimulation predisposed macrophages to destroy the extracellular matrix, whereas tenascin-C stimulation induced macrophages to synthesize matrix components. Thus, diverse stimuli can trigger the appropriate inflammatory or tissue-repair response, even though they activate the same receptor.

    Sci. Signal. 9, ra86 (2016).

  7. Global Change Biology

    Trees surge on the Tibetan Plateau

    1. Shahid Naeem

    So many factors affect tree growth that it is almost impossible to develop a concise idea of how forests will respond to global change. Accelerating tree growth on the Tibetan Plateau provides an opportunity to explore the issue. Silva et al. analyzed stable isotopes of carbon, oxygen, and nitrogen in the rings of trees from Tibet to understand why there has been a recent surge in growth during the past ~250 years. Elevated CO2, changes in water use efficiency, and permafrost thawing may explain the enhanced growth.

    Tibet's trees are experiencing a growth spurt.

    PHOTO: CHEN PELLED/ALAMY STOCK PHOTO

    Sci. Adv. 10.1126.sciadv.1501302 (2016).

  8. Textiles

    Keeping cool without losing your shirt

    1. Brent Grocholski

    People use clothing to retain warmth in cold weather. But what about clothing to keep us cool when it is hot? The challenge is to find a material that lets radiation from the human body pass through but that is opaque to visible light. Hsu et al. have created a nanoporous polyethylene textile that has both of these characteristics (see the Perspective by Boriskina). The key feature of the material is the pore size, which can be tuned to absorb visible light while being almost invisible to mid-infrared radiation. The material is water-wicking and strong and keeps skin much cooler than cotton.

    Science, this issue p. 1019; see also p. 986

  9. Organic Chemistry

    Copper-catalyzed radical relay

    1. Jake Yeston

    Breaking C-H bonds can produce highly reactive carbon radicals that enzymes can use to form new bonds to such carbon centers. Zhang et al. show that when the radicals escape the environs of their formation, a copper catalyst can also finely direct their reactivity. Chiral ligands on copper guide the asymmetric addition of a CN group to form a nitrile product with high enantioselectivity that can be used for pharmaceutical intermediates.

    Science, this issue p. 1014

  10. Planetary Science

    Dawn explores the dwarf planet Ceres

    1. Keith T. Smith

    In March 2015, the Dawn spacecraft arrived in orbit around Ceres, a dwarf planet and the largest object in the asteroid belt. Over the following months, the Dawn team extensively mapped the surface of Ceres and investigated its properties. Russell et al. give an overview of Ceres' global properties and the discovery of a plasma bow shock, which they interpret as due to a transient atmosphere. Hiesinger et al. investigated the surface craters, whose morphology and distribution allow the surface to be dated and indicate that the crust is made from a mixture of rock and ice. Buczkowski et al. describe the geological features and topology of the surface, such as domes and linear structures, which suggest cryomagmatism and subsurface ice. Ruesch et al. present a detailed study of the mountain Ahuna Mons, concluding that it is a cryovolcano formed by the eruption of a viscous mixture of salt and ice. Ammannito et al. mapped the mineral composition of the surface, which is dominated by clay-like phyllosilicates. Combe et al. report exposed water ice in Oxo crater, which must have been brought to the surface relatively recently. Together, these papers indicate a complex world of rock and ice, very different from previously investigated asteroids, and will underpin the analysis of Dawn data for years to come.

    Science, this issue pp. 1008, 1003, 1004, 1005, 1006, and 1007

  11. Climate Change

    Warm Arctic—cold continents?

    1. Julia Fahrenkamp-Uppenbrink

    In recent decades, temperatures in the Arctic have risen rapidly, causing widespread losses in sea ice. In a Perspective, Shepherd considers whether these rising Arctic temperatures could also play a role in unusually cold winters in northern mid-latitudes. Some scientists have argued that a trend toward a warm Arctic and cold mid-latitudes can be explained by natural climate variability; others contend that it is caused by climate change. Shepherd concludes that this either/or dichotomy is too simplistic: Rather, natural variability and climate change are likely to act together to affect weather patterns in the Arctic and beyond.

    Science, this issue p. 989

  12. Water Splitting

    Strontium's loss is iridium's gain

    1. Jake Yeston

    Neither plants nor people split water with the goal of making oxygen. It is simply a by-product of liberating the H in H2O for downstream use. Nonetheless, the slow kinetics of the so-called oxygen evolution reaction (OER) pose a challenge to improving the efficiency of water-derived hydrogen production. Seitz et al. have enhanced iridium oxide catalysts using the strontium-bearing precursor SrIrO3 in acid conditions. Initially, strontium leaches out of the surface layers, leaving behind a highly active, stable OER catalyst.

    Science, this issue p. 1011

  13. Plant Science

    Hormone clearance and morphogenesis in plants

    1. Pamela J. Hines

    Cytokinins are a class of plant hormones that help regulate plant morphogenesis. Züercher et al. show how cytokinin signaling in plant cells can be regulated. Purine permease 14 (PUP14) is a transporter located in the cell membrane that vacuums up cytokinin from the continuum of the plant's cell walls (the apoplast). PUP14 delivers cytokinin to the intracellular space, where it is degraded. When cytokinin is removed from the apoplast, the cytokinin sensor on the plasma membrane finds no signal. Regulation of this signaling sink fine-tunes morphogenesis.

    Science, this issue p. 1027

  14. Cardiac Arrhythmia

    Genetic underpinnings of atrial fibrillation

    1. Katrina L. Kelner

    The fluttery heartbeat of atrial fibrillation puts people in danger of stroke and heart disease. Genomic studies have identified gene variants that increase the risk for this abnormality. Nadadur et al. show how these genes influence the beat of the heart's atrium. In a mouse model of atrial fibrillation, which lacks the gene Tbx5, the authors describe a multitiered transcriptional network that links seven of these atrial fibrillation risk loci. Organized as an incoherent feed-forward loop, the network tightly controls expression of atrial rhythm genes, and its perturbation by the risk loci causes susceptibility to atrial fibrillation.

    Sci. Transl. Med. 8, 354ra115 (2016).

  15. Asymmetric Catalysis

    Targeting just one of two C-H bonds

    1. Jake Yeston

    Direct replacement of C-H bonds with C-C bonds is an especially efficient way to make complex molecules. Palladium catalysts are effective at asymmetric variants of this reaction and are valuable in pharmaceutical development. However, selecting one of two C-H bonds on the same carbon center is particularly challenging. Chen et al. have developed a set of two-coordinate chiral ligands that confer high selectivity in that particular scenario. Palladium complexes of these ligands append a variety of aryl rings to CH2 groups in amides and several carboxylic acids.

    Science, this issue p. 1023