This Week in Science

Science  22 Jan 2016:
Vol. 351, Issue 6271, pp. 350
  1. Gut Microbiota

    Social activity alters gut microbiomes

    1. Philip Yeagle

    A pair of chimpanzees grooming in Gombe Stream National Park, Tanzania

    PHOTO: © GERRY ELLIS/MINDEN PICTURES/CORBIS

    Social behavior affects which bacterial species populate the gut microbiome in primate societies. Moeller et al. combined thousands of hours of behavioral observation of the chimpanzees at Gombe National Park, Tanzania, with deep sequencing of their gut bacterial communities. Extensive social interactions among individuals created a set of microbiomes with considerable similarity in bacterial species. The same social behavior also preserved a wide diversity of microbial species in the population. Acquisition of the relatively common microbiome was achieved primarily through social interaction rather than by mother-to-child transmission.

    Sci. Adv. 10.1126.sciadv.1500997 (2016).

  2. Gene Editing

    Editing can help build stronger muscles

    1. Paula A. Kiberstis,
    2. Beverly A. Purnell

    Much of the controversy surrounding the gene-editing technology called CRISPR/Cas9 centers on the ethics of germline editing of human embryos to correct disease-causing mutations. For certain disorders such as muscular dystrophy, it may be possible to achieve therapeutic benefit by editing the faulty gene in somatic cells. In proof-of-concept studies, Long et al., Nelson et al., and Tabebordbar et al. used adeno-associated virus-9 to deliver the CRISPR/Cas9 gene-editing system to young mice with a mutation in the gene coding for dystrophin, a muscle protein deficient in patients with Duchenne muscular dystrophy. Gene editing partially restored dystrophin protein expression in skeletal and cardiac muscle and improved skeletal muscle function.

    Science, this issue p. 400, p. 403, p. 407

  3. Radio Astronomy

    Identifying live radio scattering events

    1. Keith T. Smith

    Radio emissions from distant quasars are occasionally modified for a few weeks by foreground interstellar plasma, in an extreme scattering event (ESE). Understanding this process has been difficult, because existing techniques do not allow events to be identified fast enough for follow-up before they finish. Bannister et al. developed a radio survey technique that allows ESEs to be identified in real time. After finding their first live ESE, they followed it up with additional radio and optical telescopes. The results constrain the size and density of the plasma and rule out one popular model of ESEs.

    Science, this issue p. 354

  4. Molecular Frameworks

    Weaving organic threads

    1. Phil Szuromi

    Woven fabrics are inherently flexible. Liu et al. created a molecular fabric analog using metal-organic frameworks (see the Perspective by Gutierrez-Puebla). Phenanthroline ligands on a copper metal complex directed the addition of organic linkers via imine bonds to create helical organic threads with woven texture. Removing the copper allowed the strands to slide against each other and increased the elasticity of the material 10-fold.

    Science, this issue p. 365; see also p. 336

  5. Photophysics

    A different way to put triplets in play

    1. Jake Yeston

    Most molecules adopt a singlet spin configuration: All their electrons are arranged in pairs. Unpaired triplet states engage in a variety of useful reactions but are hard to produce. Quantum mechanics dictates that photo-excitation from singlet to triplet states is inefficient. Instead, chemists rely on sensitizers, which populate the triplet states of their neighbors through energy transfer after absorbing light themselves. Mongin et al. now show that certain nanoparticles can act as triplet sensitizers.

    Science, this issue p. 369

  6. Geochemistry

    New crustal clues from old rocks

    1. Brent Grocholski

    The ghost of continental crust long eroded away may exist in certain element ratios found in Archean rocks. Tang et al. used Ni/Co and Cr/Zn ratios as a proxy for the magnesium oxide that long ago weathered away in Earth's oldest rocks. This allowed a reconstruction of rock composition, which appears to be very different from that of the crust today. The shift to contemporary crust composition occurred after the Archean era, suggesting the onset of plate tectonics.

    Science, this issue p. 372

  7. Vascular Biology

    Raising blood pressure with age

    1. Wei Wong

    Angiotensin II-induced hypertrophy in mouse aorta

    PHOTO: AKIYUKI NISHIMURA/DIVISION OF CARDIOCIRCULATORY SIGNALING, OKAZAKI INSTITUTE FOR INTEGRATIVE BIOSCIENCE (NATIONAL INSTITUTE FOR PHYSIOLOGICAL SCIENCES), NATIONAL INSTITUTES OF NATURAL SCIENCES, JAPAN

    Hypertrophy of vascular smooth muscle cells increases blood pressure. The activation of angiotensin AT1 receptors in vascular smooth muscle cells by angiotensin II can trigger either proliferation or hypertrophy, depending on age. Nishimura et al. discovered that an age-related increase in the association of AT1 receptors with purinergic P2Y6 receptors explained the different responses to angiotensin II. Vascular smooth muscle cells from young mice had fewer P2Y6 receptors than those from older mice. Angiotensin II increased the proliferation of vascular smooth muscle cells from young mice but increased cell size in those from older mice by activating different signaling pathways.

    Sci. Signal. 9, ra7 (2016).

  8. Comparative Behavior

    Let me comfort you

    1. Sacha Vignieri

    Consolation behavior promotes stress reduction of one by another. We know that consolation occurs in humans and apes. Burkett et al. observed that within a pair of monogamous prairie voles, an unstressed partner increased its grooming of a stressed partner. Furthermore, the unstressed partner matched the stressed partner in its stress hormone response. Thus, consolation may be more common than assumed in animals, and prairie voles may prove a useful model for understanding the physical and neural mechanisms underlying consolation behavior.

    Science, this issue p. 375

  9. Neurodevelopment

    Neuronal migrations follow vascular pathways

    1. Pamela J. Hines

    In the developing brain, various types of cells migrate from their birthplaces to their workplaces. Oligodendrocyte precursors, which develop to form the insulating sheaths that make signal transmission along an axon faster, travel farther than many. Tsai et al. now show just how the oligodendrocyte precursor cells find their way (see the Perspective by Dejana and Beltsholtz). The progenitor cells follow along the endothelial cells of the vasculature. Disrupting endothelial cells interfered with oligodendrocyte migration, leaving some sections of the brain deficient in insulators.

    Science, this issue p. 379; see also p. 341

  10. Solar Energy

    Relying more on the Sun

    1. Phil Szuromi

    Improved technologies for harnessing solar energy are not limited to creating more efficient solar cells. The associated hardware of delivering power from solar cells to homes and businesses, and storing this intermittent resource on the grid, offer R&D opportunities. Lewis reviews the status of these areas, as well as solar thermal and solar fuels approaches for harnessing solar energy.

    Science, this issue p. 10.1126/science.aad1920

  11. Applied Optics

    Timing on a chip

    1. Ian S. Osborne

    Laser-induced optical frequency combs allow precision measurements and affect a broad range of technologies. Brasch et al. generated optical frequency combs on an optical chip (see the Perspective by Akhmediev and Devine). They induced an optical soliton, or optical bullet, and propagated it in an engineered microcavity waveguide. The emitted output light formed a coherent comb of frequencies spanning two-thirds of an octave. Such an on-chip demonstration bodes well for miniaturization of metrological technology and its adaption for widespread application.

    Science, this issue p. 357; see also p. 340

  12. Electrochemisty

    The right kind of dopant

    1. Marc S. Lavine

    The oxygen reduction reaction is an important step in fuel cells and other electrochemical processes but is still largely dependent on precious metal-containing catalysts. Recently explored alternatives include carbon materials that are doped with different, preferably non-precious metal, atoms. Guo et al. studied model graphite catalysts to try to understand the role of nitrogen doping and to elucidate the active catalytic sites. A nitrogen atom bound to two carbons formed an active catalyst site with an activity rivaling that of N-doped graphene catalysts.

    Science, this issue p. 361

  13. Plant Development

    Cell death establishes a site for development

    1. Pamela J. Hines

    As plant roots grow through the soil, lateral roots emerge to reach more resources. Xuan et al. now show that programmed cell death sets the course for lateral root development. Cells in a specialized region of the root cap periodically die off as a group, defining a location at which a lateral root will later develop.

    Science, this issue p. 384

  14. Pollinator Diversity

    More-diverse pollinators improve crop yields

    1. Sacha Vignieri

    It is known that increased pollinator diversity can improve the yield of agricultural crops. However, how best to both produce food and maintain diversity is still debated. Garibaldi et al. show that on small farms, which provide food for the most vulnerable populations globally, pollinator diversity can significantly increase productivity. Thus, the management of crops and surrounding areas for ecological health is likely to benefit both wild pollinator populations and farmers.

    Science, this issue p. 388

  15. Small RNAs

    Offspring affected by sperm small RNAs

    1. Beverly A. Purnell

    Paternal dietary conditions in mammals influence the metabolic phenotypes of offspring. Although prior work suggests the involvement of epigenetic pathways, the mechanisms remains unclear. Two studies now show that altered paternal diet affects the level of small RNAs in mouse sperm. Chen et al. injected sperm transfer RNA (tRNA) fragments from males that had been kept on a high-fat diet into normal oocytes. The progeny displayed metabolic disorders and concomitant alteration of genes in metabolic pathways. Sharma et al. observed the biogenesis and function of small tRNA-derived fragments during sperm maturation. Further understanding of the mechanisms by which progeny are affected by parental exposure may affect human diseases such as diet-induced metabolic disorders.

    Science, this issue p. 397, p. 391

  16. Microbiology

    Two steps in one

    1. Julia Fahrenkamp-Uppenbrink

    Bacteria play key roles in the global nitrogen cycle; for example, by converting ammonia (NH3) to nitrate (NO3). This conversion is typically performed by two groups of bacteria: One group oxidizes ammonia to nitrite, and the other oxidizes nitrite to nitrate. In a Perspective, Santoro highlights recent studies that have found bacteria able to perform both steps of this process. The complete ammonia oxidizers, or comammox bacteria, live in biofilms that allow slower growth than under free-living conditions. Missed by traditional culturing methods, the bacteria were found when scientists combined enrichment of microbial consortia with genomic methods developed for sequencing uncultured bacteria.

    Science, this issue p. 342

  17. Medical Genomics

    Share trumps rare

    1. Kelly LaMarco

    No longer just buzz words, “patient empowerment” and “data sharing” are enabling breakthrough research on rare genetic diseases. Although more than 100,000 genetic variants are believed to drive disease in humans, little is known about penetrance: the probability that a mutation will actually cause disease in the carrier. This conundrum persists because small sample sizes breed imperfect alliance estimates between mutations and disease risk. Now, in Minikel et al., a patient turned scientist has joined with a large bioinformatics team to analyze vast amounts of shared data from the Exome Aggregation Consortium and the 23andMe database. The results provide insights into genetic-variant penetrance and possible treatment approaches for a rare fatal genetic prion disease.

    Sci. Transl. Med. 8, 322ra9 (2016).