This Week in Science

Science  26 Feb 2016:
Vol. 351, Issue 6276, pp. 929
  1. Cell Nucleus

    Close-up view of the nuclear periphery

    1. Stella M. Hurtley
    CREDIT: MAHAMID ET AL.

    Cell biologists would like to be able to visualize complexes inside cells at molecular resolution. Several limitations, however, have prevented the field from realizing this goal. The thickness of most cells precludes cryo-electron tomography, a technique which itself does not provide sufficient contrast. Mahamid et al. successfully combined recent advances on both fronts to analyze structures in situ at the periphery of the nucleus. Their images reveal features that inform our understanding of the native organization of nuclear pores and of the nuclear lamina.

    Science, this issue p. 969

  2. Neuroimmunology

    A T cell cause for autism?

    1. Kristen L. Mueller

    The causes of autism spectrum disorder (ASD) are complex and not entirely clear. Alterations in the mother's immune system during pregnancy, especially during key early periods of fetal neurodevelopment, may play a role. Choi et al. provided infectious or inflammatory stimuli to pregnant mice, which resulted in of spring exhibiting behaviors reminiscent of ASD (see the Perspective by Estes and McAllister). A subset of T helper cells that make the cytokine interleukin-17a in the mothers caused cortical defects and associated ASD behaviors in offspring. Therapeutic targeting of interleukin-17a during gestation reduced ASD symptoms in offspring.

    Science, this issue p. 933; see also p. 919

  3. Organic Lewis Acids

    Silicon marries a chiral counterion

    1. Jake Yeston

    Acid is among the oldest and most versatile of chemical catalysts, but its symmetrical protons can't guide reactions to favor a product over its mirror image. Chemists have resolved this shortcoming through the use of chiral conjugate bases. While the proton activates the substrate, the nearby counterion asymmetrically biases the space around it. Gatzenmeier et al. extend this approach to Lewis acid catalysis by silyl cations, which can activate a variety of substrates in complementary fashion to protons (see the Perspective by Dumoulin and Masson). By pairing these silyl groups with chiral carbon-based anions, they achieve highly enantioselective catalysis of Diels-Alder reactions.

    Science, this issue p. 949; see also p. 918

  4. Quantum Simulation

    Watching fermions transition on site

    1. Jelena Stajic

    Optical lattices are a promising platform for simulating the many-body physics that occurs in solids. In lattices filled with cold bosonic atoms, “quantum microscopy” makes it possible to watch quantum phase transitions as they unravel. Greif et al. bring a similar capability to lattices filled with fermions, which are trickier to cool but are a closer match to electrons in a solid. Tuning the interaction between the 6Li atoms allowed for the observation of transitions from a metallic phase to a band insulator and then to an interaction-dominated Mott insulator phase.

    Science, this issue p. 953

  5. Thin Films

    A golden opportunity for graphene

    1. Brent Grocholski

    Reducing friction can limit wear and improve the energy efficiency of mechanical devices. Graphene is a promising lubricant because the friction between sheets is minuscule under certain circumstances. Kawai et al. show that the same ultra-low frictional properties extend to other surfaces. They find ultralow friction when dragging graphene nanoribbons across a gold surface using an atomic force microscope. This discovery sets up the potential for developing nanographene frictionless coatings.

    Science, this issue p. 957

  6. Forest Ecology

    Leaf seasonality in Amazon forests

    1. Andrew M. Sugden

    Models assume that lower precipitation in tropical forests means less plant-available water and less photosynthesis. Direct measurements in the Amazon, however, show that production remains constant or increases in the dry season. To investigate this mismatch, Wu et al. use tower-based cameras to detect the phenology (i.e., the seasonal patterns) of leaf dynamics in tropical tree crowns in Amazonia, Brazil, and relate this to patterns of CO2 flux. Accounting for age-dependent variation among individual leaves and crowns is necessary for understanding the seasonal dynamics of photosynthesis in the entire ecosystem. Leaf phenology regulates seasonality of the carbon flux in tropical forests across a gradient of climate zones.

    Science, this issue p. 972

  7. Cancer

    Managing metastasis

    1. Angela Colmone

    Because of the poor prognosis of metastatic cancer, it is critical to determine exactly how various factors contribute to cancer spread. Mlecnik et al. examined the impact of tumor-intrinsic, microenvironmental, and immunological factors on tumor metastasis in colorectoral cancer patients. A decrease in the presence of lymphatic vessels and a reduction in immune cytotoxicity was associated more strongly with the metastatic process than were tumor-intrinsic factors such as chromosomal instability or cancer-associated mutations. Testing this so-called Immunoscore could be used as a biomarker to predict metastasis and guide therapy.

    Sci. Transl. Med. 8, 327ra26 (2016).

  8. Cell Migration

    Control cAMP to control migration

    1. John F. Foley

    Activation of the G protein-coupled receptors that stimulate cellular migration generates active G protein α and βγ subunits. These subunits then interact with distinct effector molecules. Using a small molecule that activates βγ subunits without activating α subunits in neutrophils, Surve et al. determined that active βγ subunits alone increased the intracellular concentration of the second messenger cAMP so much that the cells stuck to coated surfaces. Active G protein αi subunits balanced this βγ signal, reducing cAMP sufficiently to enable the cells to move.

    Sci. Signal. 9, ra22 (2016).

  9. Circadian Rhythms

    Layered versatility atop circadian clocks

    1. L. Bryan Ray

    The circadian clock evolved to allow cells or organisms to anticipate changes in physiological requirements associated with Earth's 24-hour light/dark cycle. Some activities, however, need to occur out of phase with the core clock. Liang et al. imaged changes in intracellular concentration of Ca2+ in populations of neurons in the fruit fly brain. Although the underlying clock was synchronous, the rhythms of Ca2+ changes corresponded with distinct timing of activities associated with activity of the particular neuronal populations. Proper coordination of these distinct phases required expression of the neuropeptide pigment-dispersing factor and its receptor.

    Science, this issue p. 976

  10. Gene Editing

    CRISPR-Cas captures invading RNA

    1. Guy Riddihough

    The CRISPR (clustered regularly interspaced short palindromic repeat) system provides bacteria with an adaptive immune response. DNA captured from viruses and plasmids by CRISPR-associated protein 1 (Cas1) is used by bacteria to target the invaders' for destruction. Silas et al. discover that certain classes of the Cas1 gene are fused to a reverse transcriptase gene (RT-Cas1) (see the Perspective by Sontheimer and Marraffini). These RT-Cas1 proteins are able to capture and directly incorporate both DNA and RNA into CRISPR loci. RT-Cas1 systems could be effective against parasitic RNA species, or even to modulate bacterial gene expression.

    Science, this issue p. 10.1126/science.aad4234; see also p. 920

  11. Organic Chemistry

    Competition for binaphthyl catalysts

    1. Jake Yeston

    The binaphthyl framework has proven extremely effective in biasing a broad range of chemical reactions toward just one of two mirror-image products. The motif was first applied as a ligand in metal catalysis, and more recently as a conjugate base in acid catalysis. Gheewala et al. report a class of chiral carbon acids based around a cyclopentadiene framework that are easily accessible from readily available precursors. The compounds are showcased as highly selective catalysts for asymmetric Mukaiyama Mannich and oxocarbenium aldol reactions.

    Science, this issue p. 961

  12. Water Infrastructure

    Improving drinking water safety

    1. Julia Fahrenkamp-Uppenbrink

    In many countries, such as the United States and the United Kingdom, drinking water contains a residual disinfectant to guard against microbial contamination. Yet others, such as the Netherlands, distribute water without such a residual to households. In a Perspective, Rosario-Ortiz et al. compare the two approaches. They show that the risk of water-borne disease is lower in the Netherlands than in the United States and the United Kingdom. The latter countries have aging pipe networks with higher rates of leakage—a measure of infrastructure vulnerability. Several barriers need to be in place, however, to allow water distribution without residual disinfectants.

    Science, this issue p. 912

  13. Clinical Neuroscience

    Treating Alzheimer's from the start

    1. Ali Shilatifard

    The formation of beta-amyloid plaques, known as Aβ aggregates, is implicated as a driving force of Alzheimer's disease. Vendruscolo et al. applied chemical kinetic approaches to identify bexarotene, an anticancer drug that selectively activates retinoid X receptor, as a molecule that can alter Aβ aggregation in vitro and in a C. elegans model. The inhibition of Aβ aggregate nucleation by bexarotene may therefore reduce the risk of development and progression of Alzheimer's disease and other similar neurodegenerative disorders.

    Sci. Adv. 2, 10.1126.sciadv.01244 (2016).

  14. Catalysis

    Direct hydrogen peroxide synthesis

    1. Phil Szuromi

    Hydrogen peroxide is synthesized industrially without direct contact of hydrogen and oxygen in order to achieve high concentrations. For many applications, only dilute aqueous solutions are needed. Freakley et al. report an improvement in the direct synthesis of hydrogen peroxide over using palladium-tin alloys. This catalyst still achieves selectivities of >95%, like palladium-gold alloys, but is cheaper and can suppress reactions that decompose the product.

    Science, this issue p. 965

  15. Conservation

    Beyond utilitarian management

    1. Julia Fahrenkamp-Uppenbrink

    Efforts to conserve species and ecosystems tend to focus on their perceived social, cultural, and economic value to humans. In a Perspective, Sarrazin and Lecomte argue that these conservation efforts, together with many other human activities, are shaping the evolutionary trajectories of nonhuman species in numerous, generally unplanned ways. To give other species the best chance of survival in a rapidly changing world, conservation approaches must take into account these long-term evolutionary consequences of human actions.

    Science, this issue p. 922

  16. Synaptic Vesicles

    Neurotransmitter uptake one vesicle at a time

    1. Stella M. Hurtley

    Despite opposing ionic gradients, synaptic vesicles are able to accumulate neurotransmitters. To resolve the mystery of how this happens, Farsi et al. made parallel measurements of pH gradients and membrane potential at the single synaptic vesicle level. Glutamatergic and GABAergic vesicles had different uptake mechanisms, revealing insights into the energetic and ionic coupling of vesicular neurotransmitter transport.

    Science, this issue p. 981

  17. Meiosis

    A partner protein for meiotic snip

    1. Guy Riddihough

    Eukaryotes generate germ cells through meiotic recombination. This process initiates through breaks in genomic DNA catalyzed by the SPO11 protein. Vrielynck et al. and Robert et al. discover that SPO11, like topoisomerase VI enzymes, interacts with a partner protein (see the Perspective by Bouuaert and Keeney). This partner is required for proper meiotic recombination and is found in a wide range of eukaryotes, suggesting that it is a universal feature of the essential recombination step.

    Science, this issue p. 939, 943; see also p. 916

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