This Week in Science

Science  29 Sep 2017:
Vol. 357, Issue 6358, pp. 1366
  1. Innate Immunity

    There's more than one way to skin an infection

    1. Angela Colmone

    Fungal skin infections are kept at bay using a two-pronged innate defense strategy.

    PHOTO: EYE OF SCIENCE/SCIENCE SOURCE

    There are two phases of innate immune control of skin infection by Candida albicans: protective containment and elimination. Santus et al. report that early activation of the transcription factor NFAT balances these two phases. During the containment phase, NFAT regulates expression of transforming growth factor-β, which induces collagen deposition and traps the microbe. During the elimination phase, NFAT induces interferon-γ, which promotes skin ulceration and microbial expulsion. Similar cross-talk between the innate immune and fibrinolytic responses also contributes to defense against Staphylococcus aureus. Such cooperation helps to minimize tissue damage while fighting infection.

    Sci. Immunol. 2, eaan2725 (2017).

  2. Solid-State Physics

    Ordering and disordering electrons

    1. Jelena Stajic

    When a liquid is cooled rapidly, it can form a glass, a state stuck between liquid and solid. Two groups looked in detail into analogous dynamics in electronic systems. Sato et al. and Sasaki et al. studied layered organic materials with a triangular in-plane lattice. These materials can assume a state in which their charge distribution has a regular pattern—an electronic or charge crystal. When the materials were cooled rapidly, a charge glass was formed instead and then allowed to crystallize. The dynamics of crystallization showed similarities to the analogous processes in conventional glasses.

    Science, this issue p. 1378, p. 1381

  3. Biogeography

    Long-distance life rafting

    1. Andrew M. Sugden

    When coastal ecosystems are affected by storms or tsunamis, organisms can be rafted across oceans on floating debris. However, such events are rarely observed, still less quantified. Carlton et al. chart the rafting journeys of coastal marine organisms across the Pacific Ocean after the 2011 East Japan earthquake and tsunami (see the Perspective by Chown). Of the nearly 300 mainly invertebrate species that reached the shores of the U.S. Pacific Northwest, most arrived attached to the remains of manmade structures.

    Science, this issue p. 1402; see also p. 1356

  4. Gene Editing

    Flexible association comes at a price

    1. Valda Vinson

    The CRISPR-Cas9 genome editing system is guided to its target DNA sequence by a small RNA that must search the genome to find its target site. To allow the guide RNA to bind, Cas9 must unwind the DNA at each location that it searches. Jones et al. used single-molecule fluorescence methods and bulk biochemistry to show that Cas9 takes 6 hours to find its target sequence, with each potential target bound for less than 30 ms. Overall, the CRISPR-Cas9 system pays for its flexible association mechanism with slow kinetics, but this can be overcome by using high concentrations of Cas9 and guide RNA.

    Science, this issue p. 1420

  5. Black Hole Formation

    Making the first supermassive black holes

    1. Keith T. Smith

    Supermassive black holes existed less than a billion years after the Big Bang. Because black holes can grow at a maximum rate that depends on their current mass, it has been difficult to understand how such massive black holes could have formed so quickly. Hirano et al. developed simulations to show that streaming motions—velocity offsets between the gas and dark matter components—could have produced black holes with tens of thousands of solar masses in the early universe. That's big enough to grow into the supermassive black holes that we observe today.

    Science, this issue p. 1375

  6. Neuroscience

    Brain circuits that modulate sociability

    1. Peter Stern

    Understanding the neural mechanisms that mediate social reward has important societal and clinical implications. Hung et al. found that release of the neuropeptide oxytocin in the ventral tegmental area of the brain increased prosocial behaviors in mice (see the Perspective by Preston). Optogenetic manipulation of oxytocin release influenced sociability in a context-dependent manner. Oxytocin increased activity in dopamine cells that project to the nucleus accumbens, another key node of reward circuitry in the brain.

    Science, this issue p. 1406; see also p. 1353

  7. Cancer

    Two-step role for mutant TERT promoters

    1. Paula A. Kiberstis

    Telomeres preserve genomic stability by preventing chromosomal fusions. The recent discovery that human tumors harbor mutations in the promoter region of the telomerase gene (TERT) produced a flurry of research aimed at elucidating the role of these mutations in cancer development. Chiba et al. present data that reconcile many of the conflicting results reported to date (see the Perspective by Shay). In human melanoma samples and a fibroblast model, TERT promoter mutations acted in two steps. First, the mutations allowed cells to proliferate with short telomeres. This fueled genomic instability and up-regulation of telomerase expression, leading to uncontrolled cell proliferation.

    Science, this issue p. 1416; see also p. 1358

  8. Thrombosis

    Rip ’n’ roll

    1. Lindsey Pujanandez

    In critically ill patients, ischemia can result in thrombosis in unrelated organs, partially owing to neutrophil recruitment. Yuan et al. combined intravital microscopy of thrombosis after gut ischemia-reperfusion injury with samples from patients with acute respiratory distress syndrome. Rolling neutrophils grabbed and ripped fragments of phosphatidylserine-expressing dying platelets, forming macroaggregates. These macroaggregates induced thrombosis that could not be targeted by conventional therapies such as aspirin. Encouragingly, however, the necrotic factor cyclophilin D had beneficial effects.

    Sci. Transl. Med. 9, eaam5861 (2017).

  9. Quantum Simulation

    Imaging a microscopic power struggle

    1. Jelena Stajic

    Strongly interacting fermions in a two-dimensional lattice form a checkerboard pattern, with spins of opposite directions occupying neighboring sites of the lattice. When an external magnetic field is applied, the situation becomes more complicated—should the spins align with the field, or try to preserve the checkerboard order? Brown et al. studied this problem using 6Li atoms in an optical lattice with unequal numbers of two spin components; the imbalance between the two played the role of an effective magnetic field. With the field applied, the checkerboard pattern correlations of the spin component perpendicular to the field became stronger than those of the spin component parallel to the field, indicating that the system was approaching the so-called canted antiferromagnetic state.

    Science, this issue p. 1385

  10. Thermoelectrics

    Strategies for efficient thermoelectrics

    1. Brent Grocholski

    Thermoelectric materials convert heat into electricity and can provide solid-state cooling for spot-sized refrigeration. One important barrier for adopting these materials beyond niche applications is their low efficiency. He and Tritt review the mechanisms and strategies for improving thermoelectric efficiency. They discuss how to report material performance and highlight the most promising materials. With new materials and strategies for performance enhancement, thermoelectrics are poised to alter the renewable energy landscape.

    Science, this issue p. eaak9997

  11. Laser Physics

    Comb quickly through a spectral zoo

    1. Jake Yeston

    Dual-comb spectroscopy relies on a pair of laser pulses with multiple frequencies distributed like tines in a comb. It is a rapid means of characterizing atoms and molecules in fine detail, but, when applied to complex mixtures, it can produce a sea of peaks that are hard to discriminate. Lomsadze and Cundiff present a protocol to extend dual comb spectroscopy into the nonlinear regime. The cross-peaks that appear in the resulting two-dimensional spectra allow assignment of crowded features to common sources, as demonstrated for an isotopic mixture of 87Rb and 85Rb.

    Science, this issue p. 1389

  12. Chemical Physics

    A chilly meeting of barium and calcium

    1. Jake Yeston

    The periodic table is an excellent predictor of element ratios in chemical compounds that form at temperatures that we commonly experience, give or take a factor of 10. Strange things start happening at hot and cold extremes, though. Puri et al. take advantage of extreme cold to observe the formation of the BaOCa+ ion, an electron-deficient alternative to conventional binary barium or calcium oxides. They first prepared cold barium methoxide ions and then exposed them to calcium atoms cooled to thousandths of a kelvin. Mass spectral and theoretical analyses revealed a barrierless reaction pathway in which triplet-state calcium displaces the methyl group.

    Science, this issue p. 1370

  13. DNA Repair

    Resolving a DNA-protein cross-link

    1. Valda Vinson

    Topoisomerase 2 (TOP2) creates DNA double-strand breaks to regulate DNA topology and is critical for processes such as replication and transcription. A covalent complex between TOP2 and DNA (TOP2cc) is an intermediate in the reaction that can be trapped by drugs. Schellenberg et al. show how the SUMO ligase ZATT promotes the resolution of TOP2cc by means of tyrosyl-DNA phosphoesterase 2 (TDP2), both by enhancing recruitment of TDP2 to SUMOylated TOP2 and by enhancing the hydrolase activity of TDP2.

    Science, this issue p. 1412

  14. Immunology

    Fetal protection from maternal immunity

    1. John F. Foley

    Recurrent miscarriages can be caused by a breakdown in immune tolerance between the mother and the fetus. Li et al. found that the surface levels of the receptor Tim-3 were increased on circulating natural killer (NK) cells in the first trimester of pregnancy. In contrast to NK cells from women with normal pregnancies, those from patients with recurrent miscarriages had decreased Tim-3 levels and were defective in immune suppression. Abortion-prone mice were protected from fetal loss if given Tim-3-positive NK cells, but not if given NK cells lacking Tim-3.

    Sci. Signal. 10, eaah4323 (2017).

  15. Mosquito Control

    Getting to the guts of mosquito control

    1. Caroline Ash

    Malaria persistently evades our best efforts to eliminate it. Pike et al. genetically modified malaria vector mosquitoes to be more immune-resistant to infection by the parasite, which altered the composition of the mosquitoes' gut bacteria. Genetically modified male (female) mosquitoes preferentially mated with wild-type females (males). Ten generations later, the genetically modified mosquitoes constituted 90% of a caged population without losing resistance to the malaria parasite. In an alternative strategy, Wang et al. engineered mosquitoes' gut bacteria. A strain of nonpathogenic bacteria, AS1, was both sexually and transgenerationally transmitted. The strain infected a laboratory population of mosquitoes and persisted for at least three generations. AS1 engineered to inhibit malaria parasite development in the midgut could do so without handicapping the mosquitoes.

    Science, this issue p. 1396, p. 1399

  16. Quantum Optics

    A rare-earth quantum memory

    1. Ian S. Osborne

    The development of global quantum networks will require chip-scale optically addressable quantum memories for quantum state storage, manipulation, and state swapping. Zhong et al. fabricated a nanostructured photonic crystal cavity in a rare-earth-doped material to form a high-fidelity quantum memory (see the Perspective by Waks and Goldschmidt). The cavity enhanced the light-matter interaction, allowing quantum states to be stored and retrieved from the memory on demand. The high fidelity and small footprint of the device offer a powerful building block for a quantum information platform.

    Science, this issue p. 1392; see also p. 1354