This Week in Science

Science  05 Feb 2016:
Vol. 351, Issue 6273, pp. 571
  1. Emerging Diseases

    Small bats in damp places doomed

    1. Shahid Naeem

    White nose syndrome in bat found in Chickamauga and Chattanooga National Military Park, Georgia, USA

    CREDIT: NATIONAL PARK SERVICE

    Emerging diseases are often selective killers. White nose syndrome (WNS), for example, is caused by a fungal pathogen that kills bats by disrupting hibernation. Introduced to North America from Europe in 2006, it has spread to 26 states and 5 Canadian provinces and killed millions of bats. Yet several species, like their European counterparts, survive infection. Hayman et al. used complex models of hibernation, pathogen energetics, and local climate to try to understand WNS's enigmatic selectivity. Small infected bats that hibernate in damp habitats are less likely to survive than larger bats that hibernate in dry habitats. These findings may help toward predicting the spread and selective toll of WNS on North American bats.

    Sci. Adv. 10.1126.sciadv.00831 (2016).

  2. Structural Biology

    A bacterial defense mechanism

    1. Valda Vinson

    Polymyxins are antibiotics that disrupt the bacterial cell membrane and are used to treat multidrug-resistant infections. A bacterial enzyme called ArnT can mediate resistance to polymyxins by transferring a sugar group from a lipid carrier to lipid A, a component of the bacterial outer membrane. Petrou et al. described structures of ArnT alone and in complex with a lipid carrier and identified a cavity where lipid A probably binds. Insights into the enzyme mechanism could be exploited to design drugs that combat polymyxin resistance.

    Science, this issue p. 608

  3. Materials Science

    Controlled colloid bonding using DNA

    1. Marc S. Lavine

    Colloidal particles can act as analogs of atoms for studying crystallization and packing behavior, but they don't naturally bond together the way atoms do. Short strands of DNA are one versatile way to link together colloidal particles (see the Perspective by Tao). Kim et al. designed a series of gold colloids with DNA ligands that reversibly bound to or released neighboring particles via DNA strands that opened or closed hairpin loops. Liu et al. devised a set of DNA strands that pack into origami structures. Inside each structure were strands that cage a gold nanoparticle. These were further linked to other uncaged nanoparticles to assemble a diamond-like structure. Changing the strand design yielded a wide range of sparsely packed colloidal crystals.

    Science, this issue p. 561, p. 579; see also p. 582

  4. Spintronics

    Manipulating a stubborn magnet

    1. Jelena Stajic

    Spintronics is an alternative to conventional electronics, based on using the electron's spin rather than its charge. Spintronic devices, such as magnetic memory, have traditionally used ferromagnetic materials to encode the 1's and 0's of the binary code. A weakness of this approach—that strong magnetic fields can erase the encoded information—could be avoided by using antiferromagnets instead of ferromagnets. But manipulating the magnetic ordering of antiferromagnets is tricky. Now, Wadley et al. have found a way (see the Perspective by Marrows). Running currents along specific directions in the thin films of the antiferromagnetic compound CuMnAs reoriented the magnetic domains in the material.

    Science, this issue p. 587; see also p. 558

  5. Forest Management

    Europe's managed forests contribute to warming

    1. Andrew M. Sugden

    For most of the past 250 years, surprisingly it seems that Europe's managed forests have been a net source of carbon, contributing to climate warming rather than mitigating it. Naudts et al. reconstructed the history of forest management in Europe in the context of a land-atmosphere model. The release of carbon otherwise stored in litter, dead wood, and soil carbon pools in managed forests was one key factor contributing to climate warming. Second, the conversion of broadleaved forests to coniferous forests has changed the albedo and evapotranspiration of those forests, also leading to warming. Thus, climate change mitigation policies in Europe and elsewhere may need to consider changes in forest management.

    Science, this issue p. 597

  6. Honey Bee Disease

    Varroa-vectored virus pandemic

    1. Caroline Ash

    Light micrograph of a honey bee Varroa mite

    PHOTO: GERD GUENTHER/SCIENCE SOURCE

    Bees are facing several threats that are causing population collapses. Wilfert et al. found that European honey bees are the primary source of deformed wing virus (DWV) (see the Perspective by Villalobos). However, paradoxically, transmission between bees is inefficient. It seems that parasitic mites can facilitate virus transmission. European honeybees acquired the rapidly spreading Varroa mite from Asian honey bees, possibly via the commercial exchange of queens. Not only do bees suffer direct damage from the mites, but the bees are also efficiently inoculated with DWV.

    Science, this issue p. 594; see also p. 554

  7. Heart Disease

    Powering down yields a healthier heart

    1. Paula A. Kiberstis

    In hypertrophic cardiomyopathy (HCM), the heart muscle enlarges and becomes progressively less efficient at pumping blood. HCM can be caused by mutations in components of the sarcomere (the heart's contractile unit), most notably myosin. Hypercontractility is among the earliest heart disturbances seen in mice carrying these myosin mutations, implying that the mutations inflict their damage by increasing myosin's power production. Green et al. identified a small molecule that binds to myosin and inhibits its activity (see the Perspective by Warshaw). When orally administered to young mice, the molecule prevented the development of several hallmark features of HCM without adversely affecting skeletal muscle.

    Science, this issue p. 617; see also p. 556

  8. Cancer

    Metastatic breast tumors break down bone

    1. Wei Wong

    Most breast cancer cells activate the breakdown of bone to promote metastases. Wang et al. found that the ABL kinases enhanced the ability of breast cancer cells to invade and break down bone in mice. In breast cancer cells, the ABL kinases activated pathways that triggered the transcription of genes encoding factors that activate osteoclasts (cells that break down bone) and those that enhanced the survival of breast cancer cells in the bone micro-environment. An ABL-specific inhibitor decreased bone metastasis in mice.

    Sci. Signal. 9, ra12 (2016).

  9. Batteries

    Why batteries go bad

    1. Marc S. Lavine

    Rechargeable batteries are found in a range of everyday devices, from shavers and laptops to cars and airplanes. Over time, these batteries can fail, either through a gradual loss of charge or through the inability to work under tough environmental conditions, leading to more catastrophic failures that cause fires or explosions. Palacin and de Guibert review such failures and suggest that, although often chemistry-specific, common causes can be found. They also look at ways to enhance battery lifetime, such as through improved battery management systems, which are needed for advanced rechargeable batteries.

    Science, this issue p. 10.1126/science.1253292

  10. Stem Cells

    Quiescent and aging hair follicle stem cells

    1. Beverly A. Purnell

    Stem cells enable normal cell homeostasis, but they also exist in a quiescent state, ready to proliferate and differentiate after tissue damage. Now, two studies reveal features of stem cells in the hair follicle, an epithelial mini-organ of the skin that is responsible for hair growth and recycling (see the Perspective by Chuong and Lei). Wang et al. found that the Foxc1 transcription factor is induced in activated hair follicle stem cells, which in turn promote Nfatc1 and BMP signaling, to reinforce quiescence. Matsumura et al. analyzed hair follicle stem cells during aging. They identified type XVII collagen (COL17A1) as key to hair thinning. DNA damage-induced depletion of COL17A1 triggered cell differentiation resulting in the shedding of epidermal keratinocytes from the skin surface. These changes then caused hair follicle shrinkage and hair loss.

    Science, this issue p. 559, p. 613; see also p. 10.1126/science.aad4395

  11. Superconductivity

    Disentangling intertwined orders

    1. Jelena Stajic

    In copper oxide superconductors, several types of order compete for supremacy. In addition to superconductivity, researchers have found periodic patterns in charge density (CDW order), as well as an asymmetry in the electronic density within the unit cell of some cuprates (nematicity). CDW order has been detected in the underdoped regime of all major cuprate families, but the ubiquity of nematicity is less clear. Achkar et al. used resonant x-ray scattering to find that, in the copper oxide planes of three lanthanum-based cuprates, nematicity has a temperature dependence distinct from that of a related structural distortion. This implies that there are additional, electronic mechanisms for nematicity

    Science, this issue p. 576

  12. Ice Sheets

    Keeping a stiff upper layer

    1. H. Jesse Smith

    The interior of the Greenland Ice Sheet is growing thicker, in contrast to the thinning that is occurring at its edges. Why? MacGregor et al. conclude that more snow is accumulating and that the ice in the interior is flowing more slowly than it did thousands of years ago (see the Perspective by Hvidberg). During the last glacial period, higher rates of atmospheric dust deposition produced softer ice, which flowed more readily than cleaner ice. During most of the Holocene, though, atmospheric dust concentrations were lower, and the less-dusty ice that formed was stiffer, meaning it did not flow or thin so rapidly. Thus, the thickening seen today in the central regions of Greenland is partly a response to changes in ice rheology that occurred thousands of years ago.

    Science, this issue p. 590; see also p. 562

  13. Cancer

    The more the merrier

    1. Yevgeniya Nusinovich

    Monoclonal antibodies against the epidermal growth factor receptor (EGFR), which drives tumor growth, are frequently used to treat colorectal cancer. Unfortunately, the cancers commonly develop drug-resistant mutations, and the monoclonal antibodies become ineffective. To overcome this problem, Arena et al. used a polyclonal antibody called MM-151, which binds multiple parts of the EGFR molecule at once, so that the cancer cannot develop resistance by mutating one site at a time. The approach was effective in both preclinical models and patients who were resistant to other anti-EGFR therapies, paving the way for further clinical development of MM-151.

    Sci. Transl. Med. 8, 324ra14 (2016).

  14. Climate Change

    It's not only the carbon in the trees

    1. H. Jesse Smith

    Forest loss affects climate not just because of the impacts it has on the carbon cycle, but also because of how it affects the fluxes of energy and water between the land and the atmosphere. Evaluating global impact is complicated because deforestation can produce different results in different climate zones, making it hard to determine large-scale trends rather than more local ones. Alkama and Cescatti conducted a global assessment of the biophysical effects of forest cover change. Forest loss amplifies diurnal temperature variations, increases mean and maximum air temperatures, and causes a significant amount of warming when compared to CO2 emission from land-use change.

    Science, this issue p. 600

  15. Cancer Therapeutics

    Cancer therapy by entrapment

    1. Paula A. Kiberstis

    Mutations in the KRAS oncogene occur at high frequency in several of the most lethal human cancers, including lung and pancreatic cancer. Substantial effort has thus been directed toward developing KRAS inhibitors. KRAS encodes an enzyme that binds the nucleotide GTP and hydrolyzes it to GDP. It had been thought that oncogenic mutations disable this hydrolytic activity, locking KRAS in the GTP-bound, active state. Surprisingly, Lito et al. found that a certain KRAS mutant (G12C) retains hydrolytic activity and continues to cycle between its active and inactive states. They describe a compound that inhibits KRAS(G12C) signaling and tumor cell growth by binding to the GDPbound form of KRAS, trapping it in its inactive state.

    Science, this issue p. 604

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