This Week in Science

Science  04 Sep 2015:
Vol. 349, Issue 6252, pp. 1066
  1. Natural Hazards

    The bigger they are, the harder they fall

    1. Brent Grocholski

    Aftermath of the 2015 Gorkha earthquake, Nepal

    PHOTO: HE - IMAGINECHINA

    The magnitude 7.8 Gorkha earthquake hit Nepal on 25 April 2015. The earthquake killed thousands and caused great damage. Galetzka et al. determined how the fault that caused this earthquake ruptured. The rupture showed a smooth slip pulse 20 km wide that moved eastward along the fault over about 6 s. The nature of the rupture limited damage to regular dwellings but generated shaking that collapsed taller structures.

    Science, this issue p. 1091

  2. Immunology

    Restraining plasma cells and multiple myeloma

    1. John F. Foley

    Plasma cells are specialized B cells that secrete antibodies. People with multiple myeloma have too many plasma cells. Mutations in the gene encoding the adaptor TRAF3 are associated with some cases of multiple myeloma. Lin et al. thus characterized mice that lacked TRAF3 in B cells. These mice had more plasma cells, and their B cells were more responsive to interleukin-6 (IL-6), a key cytokine for the development and survival of plasma cells. In normal mouse B cells, TRAF3 promoted the inactivation of a transcription factor downstream of the IL-6 receptor, suggesting that TRAF3 limits plasma cell numbers by inhibiting IL-6 signaling.

    Sci. Signal. 8, ra88 (2015).

  3. Metallugy

    Welcoming steel's new complexion

    1. Brent Grocholski

    Metals have a number of famous properties, including good strength and ductility. Controlling these properties frequently requires modifying the number and type of structural defects in a metal alloy. Kuzmina et al. produced a new type of defect, called a linear complexion, in magnesium-rich steel (see the Perspective by Kaplan). These complexions are chemically and structurally distinct regions located inside a linear defect and are isolated from the bulk by a layer of dislocations. The discovery suggests a new path for targeting defects and improving alloy development.

    Science, this issue p. 1080; see also p. 1059

  4. Genetic Disorder

    Mutation switches ligand specificity

    1. Katrina L. Kelner

    Fibrodysplasia ossificans progressiva (FOP) is a rare but deadly genetic condition that causes bone growth in place of soft tissues. The causal mutation in the bone morphogenetic protein (BMP) receptor ACVR1 is thought to boost receptor activity and trigger bone formation. Now, Harsell et al. suggest a different mechanism. They found that the mutated receptor (mACVR1) responds to activin. Normally, activin blocks BMP from binding to ACVR1. Adult mice expressing mACVR1 developed heterotopic ossification that required stimulation by endogenous activin. Small sponges soaked with activin ossified when implanted into mACVR1 mice, and animals treated with a monoclonal antibody to activin were protected. This unusual mechanism may explain why ossification in FOP patients is triggered by tissue trauma, which induces activin.

    Sci. Transl. Med. 7, 303ra137 (2015).

  5. Synthetic Biology

    Toward opioids without poppy fields

    1. Barbara R. Jasny

    Producing opioids without having to depend on field-grown poppies would be of great benefit. Synthetic production could potentially produce more-effective drugs with fewer side effects. Now, Galanie et al. have engineered yeast to produce the opioid compounds thebaine and hydrocodone, starting from sugar (see the Perspective by Nielsen). The amounts produced so far are tiny compared with what would be needed commercially. Future optimization and scaleup are the next challenge.

    Science, this issue p. 1095; see also p. 1050

  6. Allergy

    How farming protects against allergies

    1. Kristen L. Mueller

    People who grow up on dairy farms only rarely develop asthma or allergies. This is probably because as children, they breathe air containing bacterial components, which reduce the overall reactivity of the immune system. Schuijs et al. chronically exposed mice to bacterial endotoxin before they received an allergic stimulus. The protocol indeed protected them from developing an allergic response. Protection relied on a particular enzyme: A20. In humans, a variant of A20 correlates with increased susceptibility to asthma and allergy in children growing up on farms.

    Science, this issue p. 1106

  7. DNA Segregation

    Plasmid partitioning superstructure system

    1. Guy Riddihough

    Partitioning and sharing DNA between dividing cells is critical for all domains of life. Prokaryotes must share certain plasmids as well as their genomic DNA to survive. Schumacher et al. studied the partition system that segregates a conjugative plasmid in the prokaryote Sulfolobus. The system consists of three proteins. AspA spreads along the plasmid DNA to create a protein-DNA superhelix. The ParA motor protein is linked to the protein-DNA superhelix through the ParB protein, which has structural similarities to eukaryotic centromere segregating proteins.

    Science, this issue p. 1120

  8. Catalysis

    Iron lends power to traces of palladium

    1. Jake Yeston

    Palladium (Pd) is a mainstay of chemical catalysis. The precious metal has a knack for forging carbon-carbon (C-C) bonds. Handa et al. now report that when mixed in a specific preparation with iron, just parts per million of Pd suffice to catalyze the C-C bond–forming Suzuki coupling reaction. The addition of surfactants allowed the reaction to proceed in water. The protocol bodes well for conserving Pd in pharmaceutical and agrochemical synthesis.

    Science, this issue p. 1087

  9. Plant Science

    Bioremediation from disabled self-destruction

    1. Pamela J. Hines

    Explosives used in mining, construction, or military operations leave behind contaminated soils. Although bioremediation could help, plants do not thrive on these soils. Johnston et al. have now found out why (see the Perspective by Noctor). An enzyme found in plant mitochondria and chloroplasts spins out of control when given the explosive TNT, generating toxic reactive oxygen species and subverting biochemical pathways. With the key enzyme disabled, the plants are better at tolerating and accumulating TNT. These results point the way to future bioremediation and herbicide strategies.

    Science, this issue p. 1072; see also p. 1052

  10. Epidemiology

    Bringing ecology to infection

    1. Caroline Ash

    The tools we use to investigate infectious diseases tend to focus on specific one-host–one-pathogen relationships, but pathogens often have complex life cycles involving many hosts. Johnson et al. review how such complexity is analyzed by community ecologists. Ecologists have the investigative tools to probe cause and effect relationships that change with spatial scale in multispecies communities. These techniques are used to monitor the ways in which communities change through time and to probe the heterogeneity that characterizes individuals, species, and assemblages—all issues that are also essential for disease specialists to understand.

    Science, this issue 10.1126/science.1259504

  11. T Cell Chemotaxis

    Neutrophils lay down the tracks

    1. Kristen L. Mueller

    T cells constantly circulate throughout the body until an invading pathogen calls them into action. Microbes often cause localized infections, so how do T cells know where to go? Lim et al. explore this question in a mouse model of influenza infection and find that immune cells called neutrophils help guide the way (see the Perspective by Kiermaier and Sixt). Upon infection, neutrophils quickly traffic to the trachea. There, they lay down “tracks” enriched in proteins called chemokines, especially the chemokine CXCL12, which guide CD8+ T cells to the infected organ. Mice whose neutrophils could not lay down such tracks exhibited defects in CD8+ T cell recruitment and viral clearance.

    Science, this issue 10.1126/science.aaa4352; see also p. 1055

  12. Microbiome

    Estimating bacterial growth dynamics

    1. Caroline Ash

    The pattern of sequencing read coverage of bacteria in metagenomic samples reflects the growth rate. This pattern is predictive of growth because bacterial genomes are circular, with a single origin of replication. So during growth, copies of the genome accumulate at the origin. Korem et al. use the ratio of copy number at the origin to the copy number at the terminus to detect the actively growing species in a microbiome (see the Perspective by Segre). They could spot the difference between virulent and avirulent strains, population diurnal oscillations, species that are growing in irritable bowel disease, and what happens when a host's diet changes. Results were consistent in chemostats, in mice, and in human fecal samples.

    Science, this issue p. 1101; see also p. 1058

  13. Macroecology

    A general scaling law for ecology

    1. Andrew M. Sugden

    Despite the huge diversity of ecological communities, they can have unexpected patterns in common. Hatton et al. describe a general scaling law that relates total predator and prey biomass in terrestrial and aquatic animal communities (see the Perspective by Cebrian). They draw on data from many thousands of population counts of animal communities ranging from plankton to large mammals, across a wide range of biomes. They find a ubiquitous pattern of biomass scaling, which may suggest an underlying organization in ecosystems. It seems that communities follow systematic changes in structure and dynamics across environmental gradients.

    Science, this issue 10.1126/science.aac6284; see also p. 1053

  14. Chemistry

    Nonequilibrium transient self-assembly

    1. Marc S. Lavine

    In biology, the constant supply of energy can drive a system to be far from its equilibrium conditions and allow for useful work to be done. In contrast, in most synthetic systems, there is a drive toward lower energy states. Boekhoven et al. made a molecule that can switch between a nonassociating state and an associating state through the addition of a chemical fuel (see the Perspective by Van der Zwagg and Meijer). The lifetime, stiffness, and regenerative behavior of the self-assembled state could be controlled and tuned by the kinetics of fuel conversion.

    Science, this issue p. 1075; see also p. 1056

  15. Materials Science

    A superior mix of big and small

    1. Marc S. Lavine

    Graphene is often described as an unrolled carbon nanotube. However, although nanotubes are known for their exceptional mechanical and conductivity properties, the same is not true of graphene-based fibers. Xin et al. intercalated small fragments of graphene into the gaps formed by larger graphene sheets that had been coiled into fibers. Once annealed, the large sheets provided pathways for conduction, while the smaller fragments helped reinforce the fibers. The result? Superior thermal and electrical conductivity and mechanical strength.

    Science, this issue p. 1083

  16. Membrane Fusion

    Unravelling the SM-SNARE conundrum

    1. Stella M. Hurtley

    So-called SNARE proteins mediate and lend specificity to the fusion between different intracellular membranes. The SM proteins are universally required for intracellular vesicle fusion, yet their mechanism of action has long been enigmatic. Baker et al. have solved a piece of the puzzle by “capturing” SNAREs in the process of assembling into fusogenic complexes on the surface of an SM protein. The findings suggest exactly how and why SM proteins help vesicular fusion during intracellular membrane trafficking.

    Science, this issue p. 1111

  17. RNA Editing

    RNA editing helps identify cellular RNAs

    1. Guy Riddihough

    Adenosine bases in messenger RNA (mRNAs) can be enzymatically modified and changed into inosine bases. This RNA “editing” is mediated by adenosine deaminase acting on RNA (ADAR) enzymes. Liddicoat et al. show that the in vivo targets of the principal editing enzyme, ADAR1, are long double-stranded RNA (dsRNA) structures in noncoding portions of cellular mRNAs. ADAR1-directed editing of these cellular targets is critical to avoid activation of an immune response to dsRNA in the cytoplasm, because dsRNA is also a marker of viral infection.

    Science, this issue p. 1115

  18. Gene Expression

    Amalgamated regulators of gene expression

    1. Ali Shilatifard

    Less than 5% of the mammalian genome encodes protein-coding genes; over 95% of the genome consists of regulatory elements. These regulatory elements, which are referred to as enhancers or cis-regulatory elements, provide information that safeguards tissue- and cell type–specific expression of protein-coding genes. Bresnick et al. find that a single protein-coding gene can harbor multiple cis-regulatory elements. The elements are essential during development and for differentially controlling stem cell and progenitor cell transitions. Thus, amalgamated enhancer regulatory mechanisms orchestrate the seamless execution of developmental gene expression.

    Sci Adv. 10.1126/ sciadv.1500503 (2015).

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