This Week in Science

Science  01 Sep 2017:
Vol. 357, Issue 6354, pp. 882
  1. Development

    How microtubules organize in embryos

    1. Beverly A. Purnell

    Microtubule bridges between cells help to arrange early embryos.

    PHOTO: ZENKER ET AL.

    Cell functions ranging from cell division to morphogenesis rely on microtubules, with microtubule-organizing centers serving as anchoring sites for their outgrowth. Although the centrosome organizes the microtubule cytoskeleton in most animal cells, this organelle is absent in early development. Using live-cell imaging, Zenker et al. found that the cells of the early mouse embryo are connected by stable microtubule bridges to direct the growth of microtubules within them. Microtubules emanating from the bridges help to guide transport of key proteins, including E-cadherin, to the cell membrane to control cell polarization during early development.

    Science, this issue p. 925

  2. Plant Science

    Algal enzyme driven by blue light

    1. Pamela J. Hines

    Microalgae make hydrocarbons. In searching for the enzyme responsible, Sorigué et al. found a glucose-methanolcholine oxidoreductase (see the Perspective by Scrutton). Expression of the enzyme in Escherichia coli showed that hydrocarbon production requires visible light. In fact, the enzyme requires a constant input of blue photons to carry out its catalytic reaction. A long hydrophobic tunnel in the enzyme stabilizes the fatty acid substrates in proximity to the flavin adenine dinucleotide cofactor.

    Science, this issue p. 903; see also p. 872

  3. Microbiota

    Light, fat, and commensals

    1. Caroline Ash

    The gut microbiota facilitates energy harvest from food and transfers it into fat storage. Working in mice, Wang et al. found that an epithelial cell circadian transcription factor, NFIL3, is involved in regulating body composition through lipid uptake. Flagellin and lipopolysaccharide produced by certain microbes tuned the amplitude of oscillation of NFIL3 through innate lymphoid cell (ILC3) signaling, STAT3, and the epithelial cell clock. Such interactions may help to explain why circadian clock disruptions in humans, arising from shift work or international travel, frequently track with metabolic diseases, including obesity, diabetes, and cardiovascular disease.

    Science, this issue p. 912

  4. Plant Ecology

    Leaf size, climate, and energy balance

    1. Andrew M. Sugden

    Why does plant leaf size increase at lower latitudes, as exemplified by the evolutionary success of species with very large leaves in the tropics? Wright et al. analyzed leaf data for 7670 plant species, along with climatic data, from 682 sites worldwide. Their findings reveal consistent patterns and explain why earlier predictions from energy balance theory had only limited success. The authors provide a fully quantitative explanation for the latitudinal gradient in leaf size, with implications for plant ecology and physiology, vegetation modeling, and paleobotany.

    Science, this issue p. 917

  5. Transcription

    Transcription machinery remains steadfast

    1. Steve Mao

    Eukaryotic transcription of mRNA is a multistep process mediated by RNA polymerase II (Pol II). Pol II combines with several other factors to form an elongation complex that promotes transcription elongation. Ehara et al. determined the high-resolution structure of the elongation complex by means of x-ray crystallography and cryo-electron microscopy (see the Perspective by Fouqueau and Werner). Multiple elongation factors are distributed on a wide surface of Pol II and establish an RNA exit path and DNA entry or exit tunnels, which facilitate nascent transcript transfer and DNA unwinding or rewinding. The Pol II elongation complex thus adopts a stable architecture suitable for processive transcription.

    Science, this issue p. 921; see also p. 871

  6. Dengue

    Distinguishing dengue presentation

    1. Lindsey Pujanandez

    Although dengue hemorrhagic fever can be life-threatening, not all dengue virus infections even cause symptoms. Simon-Lorière et al. examined the serum and immune gene transcripts of Cambodian children infected with dengue virus serotype 1. Relative to those with clinical infections, the small subset of asymptomatic children had increased signs of antigen presentation, T cell activation, and T cell apoptosis; plasmablast differentiation and antibodies against dengue seemed to be lower. These results provide clues for pathological pathways that may drive severe dengue virus infections.

    Sci. Transl. Med. 9, eaal5088 (2017).

  7. Lung Disease

    Vascularized grafts for lungs

    1. Philip Yeagle

    Lung diseases are a major cause of death worldwide, and therapies for rebuilding damaged lung tissue are urgently needed. However, because the lung is such a complex organ, creating effective therapies is difficult. Dorrello et al. describe a way to remove pulmonary epithelial cells selectively, leaving behind an intact vasculature that preserves the structure of the organ. They then refilled the structure with adult human pulmonary cells and stem cells from alveolar progenitor cells. The approach could potentially lead to a new lung graft therapy for lung disease.

    Sci. Adv. 10.1126/sciadv.1700521 (2017).

  8. Catalysis

    X-ray vision spies copper on the move

    1. Jake Yeston

    Copper ions in zeolites help remove noxious nitrogen oxides from diesel exhaust by catalyzing their reaction with ammonia and oxygen. Paolucci et al. found that these copper ions may move about during the reaction (see the Perspective by Janssens and Vennestrøm). Zeolite catalysts generally fix metals in place while the reacting partners flow in and out of their cagelike structures. In this case, though, x-ray absorption spectroscopy suggested that the ammonia was mobilizing the copper ions to pair up as they activated oxygen during the catalytic cycle.

    Science, this issue p. 898; see also p. 866

  9. Organic Chemistry

    Keeping all fluorines on the same side

    1. Jake Yeston

    Carbon-fluorine bonds are highly polarized, and this effect is magnified when several of them reside on the same face of a saturated ring. However, most existing fluorination methods have difficulty consistently producing this all-cis mutual configuration. Wiesenfeldt et al. used a rhodium catalyst in nonpolar solvent to add hydrogens selectively to just one face of a wide variety of flat fluoroarene rings, pushing all fluorines toward the other face. The reaction also pushed fluorine toward the same face as nitrogen and oxygen in heterocycles such as indole and benzofuran.

    Science, this issue p. 908

  10. Biogeography

    Dynamics of island biodiversity

    1. Andrew M. Sugden

    Fifty years ago, MacArthur and Wilson published their influential book, The Theory of Island Biogeography. This work provided a quantitative framework for understanding the ecological processes governing the diversity of species on oceanic islands. Whittaker et al. review the subsequent progress in the field, focusing particularly on the integration of the ecological model with island geophysical dynamics. Recent work is showing how immigration, speciation, and extinction respond to the phases of emergence, development, and submergence in oceanic islands.

    Science, this issue p. eaam8326

  11. Reprogramming

    Trisomic animals lose third chromosome

    1. Beverly A. Purnell

    Generally, when a third sex chromosome is added to the normal two in mammals (XX for female and XY for male), developmental defects result. Mice that are trisomic for the sex chromosomes are infertile. Hirota et al. demonstrate that reprogramming cells from sterile mice with chromosome trisomies XXY or XYY generates XY stem cells. Sperm generated from these XY stem cells could give rise to healthy, fertile offspring. Reprogramming also promoted loss of the extra chromosome in cells from patients with Klinefelter (XXY) or Down (trisomy 21) syndrome.

    Science, this issue p. 932

  12. Neurodevelopment

    Wiring up the eye

    1. Pamela J. Hines

    During development, sensory systems must build topographic maps by connecting neurons at different levels within a circuit. Fernandes et al. now open a window into how the Drosophila eye develops these maps (see the Perspective by Isaacman-Beck and Clandinin). The authors show that glial cells that ensheath axons relay cues from photoreceptors to induce the differentiation of the photoreceptor target field—the so-called lamina neurons—in the Drosophila visual system. Thus, glia can play an instructive role in differentiation, helping to direct the spatiotemporal patterning of neurogenesis.

    Science, this issue p. 886; see also p. 867

  13. Pharmacogenomics

    Elucidating the risk of Parkinson's disease

    1. Laura M. Zahn

    High expression of the α-synuclein gene (SNCA) is a risk factor for Parkinson's disease (PD), but certain drugs may mitigate this risk. Mittal et al. ran a small-molecule screen to identify compounds that regulate levels of SNCA expression and found that several β2-adrenoreceptor (β2AR) agonists reduced them (see the Perspective by Snyder). These compounds modulated epigenetic marks at the SNCA gene, effectively suppressing SNCA transcription. The authors looked at the pharmaceutical history of more than 4 million Norwegians over an 11-year period and found a reduced risk of PD among those that were taking one of the β2AR agonists for other medical problems.

    Science, this issue p. 891; see also p. 869

  14. Structural Biology

    How a hydrogenase protects its active site

    1. Valda Vinson

    Hydrogen-metabolizing organisms use an [NiFe]-hydrogenase to catalyze hydrogen oxidation. One type of [NiFe]-hydrogenase, the NAD+-reducing soluble [NiFe]-hydrogenase (SH), couples reduction of NAD+ to the oxidation of hydrogen. Shomura et al. solved the structure of SH from an H2-oxidizing bacterium in both the air-oxidized and the active reduced state. In the reduced state, the NiFe catalytic center in SH has the same ligand coordination as in other [NiFe]-hydrogenases. However, the air-oxidized active site has an unusual coordination geometry that would prevent O2 from accessing the site and so may protect against irreversible oxidation.

    Science, this issue p. 928

  15. Infectious Disease

    For flu vaccines, age matters

    1. Angela Colmone

    Development of a broad flu vaccine has been hampered by a lack of insight into protective mechanisms of seasonal vaccines across individuals. Avey et al. performed a systems-level analysis on multiple influenza vaccination cohorts spanning distinct geographical locations and vaccination seasons. They identified prevaccination predictive transcriptional signatures of influenza vaccination responses. They then validated nine genes and three gene cohorts that were associated with the magnitude of antibody response in an independent cohort. However, these signatures were specific to young patients and had an inverse correlation in older individuals. These data may help to predict antibody response to influenza vaccination and shed light on the distinct mechanisms governing immune responses in young and old people.

    Sci. Immunol. 2, eaal4656 (2017).

  16. Immunology

    Blocking tumor immunosuppression

    1. John F. Foley

    Tumor-derived regulatory T cells (Tregs) suppress the antitumor effects of CD8+ T cells. Budhu et al. investigated the underlying mechanisms with an in vitro system that recreated some of the key features of the in vivo tumor microenvironment. Tregs inhibited the antitumor activity of CD8+ T cells toward cocultured melanoma cells from mouse tumors through the cytokine TGF-β (transforming growth factor-β), which increased the levels of an immune checkpoint protein on CD8+ T cells. A TGF-β-blocking antibody prevented immunosuppression, suggesting a therapeutic strategy to inhibit Treg activity in tumors.

    Sci. Signal. 10, eaak9702 (2017).