This Week in Science

Science  13 May 2016:
Vol. 352, Issue 6287, pp. 783
  1. Atmospheric Science

    The effects of rainfall on rainfall

    1. H. Jesse Smith

    In the United States, soil moisture in the east or west has opposite effects on future rainfall.

    PHOTO: GEORGE RANALLI/SCIENCE SOURCE

    Soil moisture, which is controlled in part by past rainfall, can affect the probability of future rainfall over large areas. This is because the water contained in soils helps determine how sunlight is converted into latent heat (evaporation) and sensible heat (which increases overlying air temperatures). Tuttle and Salvucci used data collected for the contiguous United States over 10 years to study this relationship. The feedback between soil moisture and rainfall is generally positive in the western United States but negative in the east. This regional dependence could be a function of large-scale differences in aridity.

    Science, this issue p. 825

  2. Zika Virus

    Zika virus tested in human brain organoids

    1. Caroline Ash

    The pernicious and resilient Aedes mosquito is rapidly spreading Zika virus (ZIKV) through the Americas. ZIKV infection mostly causes mild disease, but in some patients, nervous system involvement is indicated. A particular worry is an observed correlation between infection of mothers in the first trimester of pregnancy and microcephaly in newborns. Garcez et al. tested the effects of ZIKV compared with dengue virus infection on human neural stem cells grown as organoids. ZIKV targeted the human brain cells, reduced their size and viability in vitro, and caused programmed cell death responses.

    Science, this issue p. 816

  3. Climate Change

    Consequences conferred at a distance

    1. Sacha Vignieri

    Migratory animals have adapted to life in multiple, sometimes very different environments. Thus, they may show particularly complex responses as climates rapidly change. Van Gils et al. show that body size in red knot birds has been decreasing as their Arctic breeding ground warms (see the Perspective by Wikelski and Tertitski). However, the real toll of this change appears not in the rapidly changing northern part of their range but in the apparently more stable tropical wintering range. The resulting smaller, short-billed birds have difficulty reaching their major food source, deeply buried mollusks, which decreases the survival of birds born during particularly warm years.

    Science, this issue p. 819; see also p. 775

  4. Origin of Life

    Making RNA in the prebiotic world

    1. Guy Riddihough

    The RNA World hypothesis posits that RNA was one of the first self-replicating molecules leading to the origin of life. The nucleotide bases of RNA—A, U, C, and G—are chemically complex, and it has been unclear how the large purine bases A and G might have arisen on prebiotic Earth. Becker et al. show that the A and G bases can be synthesized easily and in high yield from prebiotically reasonable precursors, lending further support to the RNA World hypothesis.

    Science, this issue p. 833

  5. Sleep

    The global sleep crisis

    1. Julie A. Phillippi

    A new smartphone app reveals societal influences on sleep habits worldwide. App users tracked light exposure and jet lag effects to see the personalized impact of sleep duration. Taking advantage of the accumulated data, Walch et al. applied mathematical modeling to assess the impact of social pressures on sleep. Country-specific trends in bedtime predicted sleep duration. Age is the prominent determinant of sleep timing, although women tend to schedule more sleep than men. In the perpetual tug-of-war between circadian clocks and social timekeeping, the impact of sleep deprivation on populations can now be explored on a global scale.

    Sci Adv. 2, 10.1126/sciadv.1501705 (2016).

  6. Organic Chemistry

    Carbon links without helpful neighbors

    1. Jake Yeston

    It's an irony of modern organic chemistry that the simplest-looking carbon-carbon bonds are often the hardest to make. Most reactions owe their efficiency to neighboring double bonds or oxygen and nitrogen atoms that linger in the products. Qin et al. now present a broadly applicable protocol for making C-C bonds in the absence of such surrounding help. The nickel-catalyzed process couples a zinc-activated carbon center to an ester that's poised to lose CO2. The ready availability of numerous carboxylic acids (which are easily converted to esters) contributes to the reaction's versatility.

    Science, this issue p. 801

  7. Neurodegeneration

    A window into Alzheimer's disease

    1. Orla M. Smith

    Patient brain scan showing tau topography.

    PHOTO: BRIER ET AL.

    Alzheimer's disease (AD) involves the accumulation of amyloid-β (Aβ) plaques and tau tangles in the brain. The cognitive and pathological results of Ab deposition in patients with AD have been well studied, owing to the availability of PET (positron emission tomography) imaging ligands. Brier et al. used newly available PET imaging agents for tau to explore the relationship between tau pathology and Aβ pathology in patients with early AD. Overall, tau imaging provided a more robust predictor of disease status than Aβ imaging. Whereas Aβ imaging is a good marker of early AD, tau imaging is a more robust predictor of disease progression.

    Sci. Transl. Med. 8, 338a66 (2016).

  8. Sleep Research

    Let sleeping mice remember

    1. Peter Stern

    The role of REM (rapid eye movement) sleep for memory consolidation has been discussed for a long time. Boyce et al. used optogenetics to inhibit theta oscillations in the mouse hippocampus during REM sleep (see the Perspective by Kocsis). Both object recognition memory and contextual fear memory were impaired. This consolidation mechanism occurred in a critical time window immediately after training. Disrupting the same system for similar durations during non-REM sleep or wakefulness had no effect on memory.

    Science, this issue p. 812; see also p. 770

  9. Psychology

    The psychological cost of reconciliation

    1. Gilbert Chin

    During civil wars, individuals and communities who were previously good neighbors can end up fighting each other. One approach to reknit these sundered social ties is to bring perpetrators and victims together in truth and reconciliation forums. Cilliers et al. found that these forums have helped to reestablish social bonds in Sierra Leone, but that they have also imposed a cost on the victims' mental health (see the Perspective by Casey and Glennerster).

    Science, this issue p. 787; see also p. 766

  10. Mucosal Immunology

    A recipe for intestinal lgA

    1. Gilbert Chin

    Our guts are teeming with microbes, some friendly and others not. Plasma cells in the gut secrete immunoglobulin A (IgA), which helps to keep the peace with resident commensal bacteria and fights pathogens. B cell isotype switching to IgA occurs in lymphoid tissues called Peyer's patches. Reboldi et al. studied the cellular processes that guide B cells toward making IgA in mice. B cells took an unexpected journey from Peyer's patches follicles to the intestinal mucosa to interact with specialized IgA-triggering dendritic cells. The B cells then migrated back to the follicles to become IgA-producing B cells.

    Science, this issue p. 10.1126/science.aaf4822

  11. Nonlinear Optics

    Nonlinear optics: A surprise in store?

    1. Ian S. Osborne

    At ultrafast data rates, the ability to use light to control things could speed information processing. However, photons tend not to interact with each other, and so a nonlinear optical material is needed and the response of such materials is typically weak. Alam et al. report a surprising finding: that indium tin oxide, a commercially available transparent conducting oxide widely used in microelectronics, exhibits a large nonlinear response. They used a wavelength regime where the permittivity of the material is close to zero and observed a large and fast nonlinear optical response. The finding offers the possibility that other, so far unexplored, materials may be out there for nonlinear optical applications.

    Science, this issue p. 795

  12. Catalysis

    Lightly dispersed palladium

    1. Phil Szuromi

    Catalysts made from atomically dispersed metal atoms on oxide supports can exhibit very high per atom activity. However, the low loadings needed to prevent metal particle formation can limit overall performance. Liu et al. stably decorated titanium oxide nanosheets with relatively high loadings of single palladium atoms by reducing the ions with ultraviolet light and ethylene glycol. These catalysts cleaved H2 into atoms and were highly effective for hydrogenating alkenes and aldehydes.

    Science, this issue p. 797

  13. Applied Physics

    A twist on optical multiplexing

    1. Ian S. Osborne

    Information can be encoded using various properties of light. Optical multiplexing frequency, brightness, and polarization have played crucial roles in information technologies, high-capacity data storage, high-speed communications, and biological sensing. Angular momentum is another degree of freedom that could increase capacity further. Typically, however, the bulk optical elements used to determine the angular momentum of light limit possible on-chip processing. Ren et al. take a nanophotonics approach to measure and sort light co-propagating with different states of angular momentum (see the Perspective by Molina-Terriza). The approach is promising for on-chip multiplex processing of optical signals.

    Science, this issue p. 805; see also p. 774

  14. Metalloproteins

    Catching a radical in action

    1. Nicholas S. Wigginton

    Many enzymes catalyze reactions through the production of radical intermediates. Radical SAM enzymes, the largest superfamily of enzymes in nature, do this by using an iron-sulfur cluster to cleave S-adenosylmethionine and produce a radical intermediate. Using freeze quenching, Horitani et al. were able to trap a previously unseen radical intermediate from bacterial pyruvate formate-lyase activating enzyme. Spectroscopy revealed that the intermediate consists of a short-lived covalent bond between the terminal carbon of 5′-deoxyadenosyl and the single iron atom of the iron-sulfur cluster. Not only does the observation of this radical expand our mechanistic understanding of radical SAM enzymes, but it expands the range of enzyme active sites or cofactors that function through an organometallic center.

    Science, this issue p. 822

  15. HIV-1 Antibodies

    An antibody to block viral fusion

    1. Kristen L. Mueller

    A small fraction of HIV-1–infected individuals develop broad and potent antibodies that bind the HIV-1 envelope protein (Env). These antibodies recognize a limited set of conserved epitopes on Env, such as Env's host receptor-binding site. Kong et al. now report a neutralizing antibody isolated from an HIV-1–infected individual that binds to the fusion peptide of Env. This is unexpected because viruses often try to mask such key components of their cell entry machinery from antibody attack. Crystal structures of the antibody bound to the fusion peptide and to Env itself define the epitope, provide insight into the specific mechanism of antibody binding, and may inform HIV-1 vaccine design.

    Science, this issue p. 828

  16. Molecular Evolution

    Epistasis and mutational fitness landscape

    1. Laura M. Zahn

    A fitness landscape of a gene defines the molecular potential of evolution. This can help us understand the current state of evolution as well as predict unrealized potential. Using deep sequencing to examine mutations in nonessential genes that affect the growth of yeast strains, two studies have generated fitness landscapes and measured the effect of epistatic interactions (see the Perspective by He and Liu). Li et al. generated a library of mutants in a transfer RNA gene, including all single and many double and multiple mutants. The RNA secondary structure was generally predictive of bases under selection. Similarly, Puchta et al. assessed a small nucleolar RNA gene for the fitness effects of individual mutations, which correlated with evolutionary conservation and structural stability. Both studies suggest that epistasis—the combined functional effect—for double substitutions is more often negative than positive.

    Science, this issue pp. 837 and 840; see also p. 769

  17. Cancer

    An oncohistone deranges inhibitory chromatin

    1. Guy Riddihough

    Missense mutations (that change one amino acid for another) in histone H3 can produce a so-called oncohistone and are found in a number of pediatric cancers. For example, the lysine-36–to-methionine (K36M) mutation is seen in almost all chondroblastomas. Lu et al. show that K36M mutant histones are oncogenic, and they inhibit the normal methylation of this same residue in wild-type H3 histones. The mutant histones also interfere with the normal development of bone-related cells and the deposition of inhibitory chromatin marks.

    Science, this issue p. 844

  18. Neurodegeneration

    A role for PKCα in Alzheimer's disease

    1. Leslie K. Ferrarelli

    The neurodegeneration that occurs in Alzheimer's disease is thought to be due to the accumulation of a protein called amyloid-β (Aβ). Alfonso et al. identified activating mutations in protein kinase Cα (PKCα) in a large cohort of families in which late-onset Alzheimer's disease was diagnosed. Pharmacologically inhibiting PKCα or deleting the gene encoding it prevented Aβ from impairing synaptic activity in mouse hippocampal tissue slices. Thus, PKCα variants may mediate the pathological effects of Aβ in some patients with late-onset Alzheimer's disease.

    Sci. Signal. 9, ra47 (2016).

  19. Geochemistry

    Isotopes isolated after impact

    1. Brent Grocholski

    Details about how Earth formed are gleaned from the daughter products of certain short-lived radioactive isotopes found in rocks. Rizo et al. describe subtle tungsten isotope variations in rocks from the very deep mantle in Baffin Island and the Ontong Java Plateau (see the Perspective by Dahl). The results suggest that portions of Earth have remained unmixed since it formed. The unmixed deep mantle rocks also imply that Earth's core formed from several large impact events.

    Science, this issue p. 809; see also p. 768

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