This Week in Science

Science  10 Jul 2015:
Vol. 349, Issue 6244, pp. 150
  1. Animal Physiology

    Laid-back bamboo eater

    1. Sacha Vignieri

    Pandas live life in a metabolic slow zone

    PHOTO: © OLGA KHOROSHUNOVA/ALAMY

    Pandas are members of the order Carnivora but are entirely herbivorous, living almost exclusively on bamboo. Unlike most other herbivorous species, however, their digestive tract has not evolved the long twists and turns that facilitate the slower digestion necessary for cellulose-rich plants. Nie et al. measured energy expenditure in both wild and captive pandas, which was extremely low, relative to other mammals. The pandas' thyroid hormone levels are also a fraction of the mammalian norm.

    Science, this issue p. 171

  2. Protein Structure

    Structure of a sterol sensor

    1. Valda Vinson

    The aberrant accumulation of sterols contributes to heart attack and stroke. Two proteins embedded in the membrane of the endoplasmic reticulum, Insig-1 and Insig-2, are key players in the cellular pathway that regulates cellular sterol levels. Ren et al. report the structure of a mycobacterial homolog of Insig. The structure, together with biochemical experiments, suggests how Insig interacts with other components of the sterol regulatory pathway.

    Science, this issue p. 187

  3. Alzheimer's Disease

    Protecting neurons from amyloid β

    1. Wei Wong

    In the developing nervous system, the secreted protein Reelin helps to guide migrating neurons to their correct destination. In the adult nervous system, Reelin enhances synaptic plasticity and protects isolated neurons from amyloid β toxicity. Accumulation of amyloid β causes the neurodegeneration characteristic of Alzheimer's disease. To avoid the developmental defects associated with Reelin deficiency, Lane-Donovan et al. generated mice with an inducible knockout of Reelin. Mice that lacked Reelin as adults showed defects in synaptic plasticity, learning, and memory in response to amyloid β accumulation. Thus, Reelin can protect against amyloid β neurotoxicity in vivo.

    Sci. Signal. 8, ra67 (2015).

  4. Galaxy Evolution

    Black hole out of kilter with theory

    1. Ian S. Osborne

    It is believed that black holes and their host galaxies coevolve, with the feedback from the black hole inducing star formation. Such a scenario requires certain timing and mass constraints for the black hole and the star-forming gas. Trakhtenbrot et al. looked at high–red shift galaxies, when the universe was only about 2 billion years old. They found a black hole that developed to maturity much earlier than would be expected and was about 10% of the total galactic mass—much more than expected. Moreover, star formation continued after it would have been expected to stop.

    Science, this issue p. 168

  5. Water Resources

    Continental global water filter

    1. Nicholas S. Wigginton

    Mobile surface waters and soil waters are relatively disconnected on a global scale. Water on land is eventually lost by surface runoff into the oceans or is ultimately sent back to the atmosphere through evapotranspiration processes. Good et al. determined that 65% of continental water evaporation is from soils, which includes water taken up and transpired by plants (see the Perspective by Brooks). Although just a small fraction of global surface waters pass through soils, individual stream ecosystems may be affected by water quality changes in nearby soils.

    Science, this issue p. 175; see also p. 138

  6. Vesicular Transport

    A coat of many components

    1. Stella M. Hurtley

    The formation of coated trafficking vesicles is among the most fundamental of cellular processes. COP1 transport vesicles are involved in retrograde membrane trafficking in the Golgi apparatus and endoplasmic reticulum. Dodonova et al. applied cryo–electron tomography to determine the structure of the COPI coat in its fully assembled form on budded vesicles (see the Perspective by Noble and Stagg). They combined structural data with cross-linking mass spectrometry to generate a complete molecular model. The model suggests a mechanism of coat assembly in which coat proteins cluster via flexible interactions instead of forming a protein cage on the membrane.

    Science, this issue p. 195; see also p. 142

  7. Soft Robotics

    Making jack jump efficiently

    1. Marc S. Lavine

    In the future, soft-bodied robots may be able to squeeze into tight spaces or work in environments where they could be crushed. However, it is hard to ensure efficient power transmission in a soft-bodied device. One promising solution is to use explosions to drive the robot, using efficient weight-to-power energy sources. Using three-dimensional printing to fuse together multiple materials, Bartlett et al. built a combustion-powered robot. The robot has a rigid core that transitions to a soft exterior. They produced an efficient jumping robot in which the gradations in the hardness of the body materials also improved robustness.

    Jumping robots in action

    PHOTO: BARTLETT ET AL.

    Science, this issue p. 161

  8. Plutonium

    “Missing magnetism” puzzle solved

    1. Zakya H. Kafafi

    To explain plutonium's complex structural properties, conventional band structure theories typically invoke magnetism, in stark contrast with experiment. Janoschek et al. used neutron spectroscopy and found that the magnetism in plutonium is not “missing” but dynamic: the fingerprint of an electronic ground state that is a quantum-mechanical admixture of localized and itinerant electronic configurations. This finding provides a natural explanation for plutonium's complex structural, magnetic, and electronic properties.

    Sci. Adv. 10.1126. sciadv.1500188 (2015).

  9. Neuronal Modeling

    A better way to explain neuronal activity

    1. Peter Stern

    A brain region called the lateral intraparietal (LIP) area is involved in primate decision-making. The dominant model to explain neuronal firing in LIP assumes that neurons slowly accumulate sensory evidence in favor of one choice or another. Latimer et al. hypothesized that neurons instead exhibit rapid steps or jumps in their firing rate, reflecting discrete changes in the animal's decision state. They recorded from LIP neurons in macaque monkeys performing a motion-discrimination task. LIP spike trains in most cells involved discrete stepping dynamics rather than slow evidence integration dynamics.

    Science, this issue p. 184

  10. Sea-Level Rise

    Warming climate, melting ice, rising seas

    1. H. Jesse Smith

    We know that the sea level will rise as climate warms. Nevertheless, accurate projections of how much sea-level rise will occur are difficult to make based solely on modern observations. Determining how ice sheets and sea level have varied in past warm periods can help us better understand how sensitive ice sheets are to higher temperatures. Dutton et al. review recent interdisciplinary progress in understanding this issue, based on data from four different warm intervals over the past 3 million years. Their synthesis provides a clear picture of the progress we have made and the hurdles that still exist.

    Science, this issue 10.1126/science.aaa4019

  11. HIV-1 Vaccines

    Steps in the right direction

    1. Kristen L. Mueller

    HIV-1 mutates rapidly, making it difficult to design a vaccine that will protect people against all of the virus' iterations. A potential successful vaccine design might protect by eliciting broadly neutralizing antibodies (bNAbs), which target specific regions on HIV-1's trimeric envelope glycoprotein (Env) (see the Perspective by Mascola). Jardine et al. used mice engineered to express germline-reverted heavy chains of a particular bNAb and immunized them with an Env-based immunogen designed to bind to precursors of that bNAb. Sanders et al. compared rabbits and monkeys immunized with Env trimers that adopt a nativelike conformation. In both cases, immunized animals produced antibodies that shared similarities with bNAbs. Boosting these animals with other immunogens may drive these antibodies to further mutate into the longsought bNAbs. Chen et al. report that retaining the cytoplasmic domain of Env proteins may be important to attract bNAbs. Removing the cytoplasmic domain may distract the immune response and instead generate antibodies that target epitopes on Env that would not lead to protection.

    Science, this issue p. 139, 10.1126/science.aac4223, p. 156; see also p. 191

  12. Immunology

    Single-cell measurements map immunity

    1. Bryan L. Ray

    Multiple characteristics of individual cells define cell types and their physiological states. Spitzer et al. quantitated the abundance of 39 different cell surface proteins or transcription factors on individual cells of the mouse immune system. They used these measurements to create a map that clustered similar individual cells into groups corresponding to cell type and function. Their extensible experimental platform will allow the inclusion of other data types and data from independent laboratories.

    Science, this issue 10.1126/science.1259425

  13. Applied Physics

    Graphene-based biosensors

    1. Ian S. Osborne

    The mid-infrared (mid-IR) range is particularly well suited for biosensing because it encompasses the molecular vibrations that identify the biochemical building blocks of life, such as proteins, lipids, and DNA. However, the resulting optical signal is extremely weak and often requires complex techniques to enhance the biological detection. Rodrigo et al. present a graphene-based biosensor that they dynamically tuned over a broad spectral range through electrical gating. The authors selectively probed protein molecules at different mid-IR frequencies using a single device.

    Science, this issue p. 165

  14. Economics

    The heroes of the Industrial Revolution

    1. Julia Fahrenkamp-Uppenbrink

    Did a few great inventors and scientists drive the Industrial Revolution, or would it have happened regardless of such brilliant individuals? In a Perspective, Mokyr argues that the truth probably lies in the middle. Only a small minority of the population was involved in creating and adapting the new techniques and machines that would revolutionize the economy. A recent study estimates the size of these educated elites in French cities from the subscribers to the Grande Encyclopédie. The more subscribers there were in a city, the faster was the subsequent process of industrialization. Modern societies aiming to foster scientific and technological creativity may thus need to do more than raise the levels of mass education.

    Science, this issue p. 141

  15. Place Cells

    Memory storage in neural networks

    1. Peter Stern

    Neuronal networks can store and retrieve discrete memories, but often fail to retrieve stored sequences. This is because error decreases over time for a static attractor, but builds up drastically over time if patterns are not trained to retrieve themselves but to retrieve the next item in a sequence. Pfeiffer and Foster studied brain activity in awake but immobile rats. Recording simultaneously from a large number of place cells in the hippocampal formation, they found that internally generated sequences alternated between periods of hovering in place while being strengthened, and periods of abrupt transition to a new place.

    Science, this issue p. 180

  16. Climate Change

    Bucking the trend

    1. Sacha Vignieri

    Responses to climate change have been observed across many species. There is a general trend for species to shift their ranges poleward or up in elevation. Not all species, however, can make such shifts, and these species might experience more rapid declines. Kerr et al. looked at data on bumblebees across North America and Europe over the past 110 years. Bumblebees have not shifted northward and are experiencing shrinking distributions in the southern ends of their range. Such failures to shift may be because of their origins in a cooler climate, and suggest an elevated susceptibility to rapid climate change.

    Science, this issue p. 177

  17. Lung Disease

    Calming the cytokine storm

    1. Angela Colmone

    The innate immune response is poised to act quickly in the face of pathogenic invaders. However, this priming can incite a cytokine storm: excessive production of inflammatory cytokines that harm the host. Coon et al. now report that HECTD2, a ubiquitin E3 ligase, can degrade the anti-inflammatory protein PIAS1, enhancing this inflammatory effect. People with a polymorphism in the HECTD2 gene exhibit lower inflammation and are protected from acute respiratory distress syndrome. Moreover, a small-molecule inhibitor of HECTD2 reduced lung inflammation in mice. These observations pinpoint HECTD2 as a therapeutic target for inflammation-induced lung injury.

    Sci. Transl. Med. 7, 295ra109 (2015).

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