This Week in Science

Science  03 Feb 2017:
Vol. 355, Issue 6324, pp. 444
  1. Sensors

    Sensitive skin for feeling the heat

    1. Marc S. Lavine

    Pit vipers can sense the heat of their prey at a distance.

    PHOTOS (FROM TOP): SIBANDA ET AL.; OSCAR DOMINGUEZ/ALAMY STOCK PHOTO

    Pit vipers' ability to sense temperature is so acute that they can detect warm-blooded prey from a distance. With this as inspiration, Di Giacomo et al. developed cross-linked pectin films that could detect temperature differences down to 10 mK across a temperature range of 45 K. The pectin films were successfully integrated into an artificial skin that protected the films while still allowing for temperature determination.

    Sci. Robot. 10.1126/scirobotics.aai9251 (2017).

  2. Electron Microscopy

    Ultrafast studies using liquid cells

    1. Marc S. Lavine

    Advances in microscopy techniques aim to make it possible to study materials under more realistic conditions, such as in liquid cells, or to use fast probes to capture dynamics. Fu et al. combined liquid cell transmission electron microscopy with ultrafast pump-probe spectroscopy to perform timeresolved studies of nanoscale objects (see the Perspective by Baum). They successfully captured the change in rotational dynamics of coupled gold nanoparticles and also observed the dynamics as two particles fused together in a liquid environment.

    Science, this issue p. 494; see also p. 458

  3. Vascular Biology

    Protected from atherosclerosis by TFEB

    1. Wei Wong

    Atherosclerosis, or the buildup of fatty plaques in blood vessels, can lead to high blood pressure and heart attacks. Lu et al. found that in cultured endothelial cells, the transcription factor TFEB reduced oxidative stress and inflammation, processes that contribute to the development of atherosclerosis. When fed a high-fat diet, mice that overexpressed TFEB in endothelial cells developed smaller atherosclerotic lesions than their control littermates on the same diet.

    Sci. Signal. 10, eaah4214 (2017).

  4. Political Science

    Using global data for election predictions

    1. Barbara R. Jasny

    Assumptions underlying election result predictions have been questioned recently. Kennedy et al. assessed more than 650 executive office elections in over 85 countries and performed two live forecasting experiments. They analyzed a variety of potential predictors theorized to be of importance, ranging from economic performance to polling data. Elections were about 80 to 90% predictable, despite uncertainties with available data. Polling data were very important to successful prediction, although it was necessary to correct for systematic biases. Unexpectedly, economic indicators were only weakly predictive. As data sources improve and grow, predictive power is expected to increase.

    Science, this issue p. 515

  5. Asymmetric Catalysis

    Expressed preferences among methyl groups

    1. Jake Yeston

    Targeting just one of the two equivalent branch ends in Y-shaped molecules is a particular challenge for catalysis. Enzymes manage to do it by grasping the whole molecule, octopus-like, but often enzymes cannot tolerate minor structural variations. Wu et al. produced an amide-directed palladium catalyst that, armed with oxazoline-derived chiral ligands, could reliably attack just one methyl member of isopropyl groups. The reaction successfully replaced C–H bonds with C–C bonds in a wide variety of aryl and vinyl coupling partners.

    Science, this issue p. 499

  6. Ribosome

    The yeast mitoribosome

    1. Valda Vinson

    Mitochondria are eukaryotic organelles that produce ATP, the energy source of the cell. They have dedicated ribosomes (mitoribosomes) that encode some of the membrane proteins that are essential to ATP production. Desai et al. present a high-resolution structure of the 75-component yeast mitoribosome, determined by electron cryomicroscopy. Mitoribosomes share an ancestor with modern bacterial ribosomes. Comparing the structure of the yeast mitoribosome with mammalian mitoribosomes suggests how they have evolved differently to perform species-specific functions.

    Science, this issue p. 528

  7. Sleep Research

    Synapse remodeling during sleep

    1. Peter Stern

    3D reconstructions of mouse neuronal dendrites

    PHOTO: DE VIVO ET AL.

    General activity and information processing while an animal is awake drive synapse strengthening. This is counterbalanced by weakening of synapses during sleep (see the Perspective by Acsády). De Vivo et al. used serial scanning electron microscopy to reconstruct axon-spine interface and spine head volume in the mouse brain. They observed a substantial decrease in interface size after sleep. The largest relative changes occurred among weak synapses, whereas strong ones remained stable. Diering et al. found that synapses undergo changes in synaptic glutamate receptors during the sleep-wake cycle, driven by the immediate early gene Homer1a. In awake animals, Homer1a accumulates in neurons but is excluded from synapses by high levels of noradrenaline. At the onset of sleep, noradrenaline levels decline, allowing Homer1a to move to excitatory synapses and drive synapse weakening.

    Science, this issue p. 457, p. 507; see also p. 511

  8. Chromosomes

    Tethering DNA for packing purposes

    1. Guy Riddihough

    Condensin protein complexes are critical for chromosome segregation and compaction. They form ring-shaped structures that encircle and topologically constrain DNA strands. Wang et al. show that Bacillus subtilis condensin complexes hold the two arms of the circular chromosome together (see the Perspective by Sherratt). The complexes seem to do this by encircling individual DNA duplexes and then tethering the two duplexes together by “handcuffing.” The complexes actively travel along the DNA and function to enlarge DNA loops processively, leading to chromosome compaction.

    Science, this issue p. 524; see also p. 460

  9. Physics

    Getting a sense of atomically thin materials

    1. Ian S. Osborne

    Two-dimensional materials such as graphene and transition metal dichalcogenides provide a powerful platform for optoelectronic applications. As the materials get thinner, however, characterizing the electronic properties can present an experimental challenge. Lovchinsky et al. demonstrate that atomic-like impurities in diamond can be used to probe the properties of 2D materials by nanometer-scale nuclear quadrupole resonance spectroscopy. Coherent manipulation of shallow nitrogen-vacancy color centers enabled probing of nanoscale ensembles down to several tens of nuclear spins in atomically thin hexagonal boron nitride.

    Science, this issue p. 503

  10. Cell Biology

    Peroxisome inheritance and differentiation

    1. Beverly A. Purnell

    For normal tissue structure and function, cells exert strict control over growth versus differentiation. Poor wound healing and aging can result from too little proliferation. Conversely, the development of cancer can involve excessive cell growth. Asare et al. looked for regulators that balance proliferation and differentiation in the epidermis (see the Perspective by Gruneberg and Barr). They observed differences in the transcript profile of epidermal progenitors, their differentiating progeny, and epidermal cancers. Epidermal progenitors that were deficient in the peroxisome-associate protein Pex11b did not segregate peroxisomes properly among dividing cells. This led to a delay in mitosis that perturbed polarized divisions. These events skewed daughter cell fate and resulted in a defective skin barrier. Thus, peroxisome inheritance appears to play a role in normal mitosis and cell differentiation.

    Science, this issue 10.1126/science.aah4701; see also p. 459

  11. DNA Repair

    Activating DNA repair

    1. Valda Vinson

    DNA double-strand breaks must be repaired efficiently to avoid cell death or cancer. The break ends can either be directly ligated by nonhomologous end joining (NHEJ) or more accurately repaired by homologous recombination that uses information from the sister chromatid. Sibanda et al. present a high-resolution x-ray structure of a key component of the DNA repair machinery, the DNA-dependent kinase catalytic subunit (DNA-PKcs), bound to a C-terminal peptide of Ku80. The structure suggests that Ku80 presents the DNA ends for repair to a DNA-PKcs dimer and that activity is modulated by interactions between the monomers. Binding of either Ku80 or BRCA1, which may compete for the same binding site on DNA-PKcs, could provide a switch between NHEJ and homologous recombination.

    Science, this issue p. 520

  12. Forest Restoration

    From lofty goals to on-the-ground success

    1. Julia Fahrenkamp-Uppenbrink

    Global initiatives call for the restoration of vast areas of deforested landscapes worldwide, particularly in the tropics. In a Perspective, Holl highlights the disconnect between these ambitious goals and the reality on the ground, where forest restoration must compete with numerous other land uses. Many studies of forest restoration have been performed at small scales, making it difficult to apply their results. Furthermore, efforts to restore forests in productive agricultural landscapes often meet with local resistance. Examples from the Atlantic Forest Restoration Pact in Brazil and from Colombia point the way to successful forest landscape restoration approaches that balance ecological and human welfare goals.

    Science, this issue p. 455

  13. HIV

    Engineering HIV immunity

    1. Angela Colmone

    For rapidly mutating viruses such as HIV, antibodies that can neutralize more than one strain may have real therapeutic potential. Williams et al. examined the origin of broadly neutralizing antibodies (bnAbs) that recognize a part of the membrane-proximal external region (MPER) of HIV-1 gp41. They found similar clonal lineages of a MPER bnAb from both memory B cells and plasma, highlighting the viability of plasma as a source of bnAbs. These lineages shared an autoreactive unmutated common ancestor, suggesting that tolerance must be overcome for bnAb induction. The authors then engineered chimeric antibodies from the plasma and memory B cells that successfully neutralized most HIV-1 strains.

    Sci. Immunol. 2, eaal2200 (2017).

  14. Cancer

    Stem cells on a mission

    1. Yevgeniya Nusinovich

    Healthy neural stem cells can infiltrate and help treat brain tumors because they naturally migrate toward gliomas in response to tumor-derived chemotactic signals. Obtaining neural stem cells from a patient can be difficult, however, and donor stem cells pose a risk of immune rejection and other safety concerns. Bagó et al. discovered a way to avoid these risks by taking normal human skin fibroblasts and transdifferentiating them into neural stem cells. The entire process took only 4 days to complete, yielding autologous patient-derived neural stem cells. The authors engineered these stem cells to infiltrate and effectively treat brain tumors in multiple mouse models.

    Sci. Transl. Med. 9, eaah6510 (2017).