This Week in Science

Science  07 Aug 2015:
Vol. 349, Issue 6248, pp. 598
  1. Evolutionary Biology

    The benefits of pupil orientation

    1. SN

    Vertical pupils allow cats and other predators to better stalk their prey

    CREDITS: © S. DEISSNER/F1 ONLINE/CORBIS

    Slit-eyed animals have either vertical or horizontal pupils. It is unclear whether one orientation conveys any sort of competitive advantage over the other, and if so, under what circumstances. Banks et al. suggest that the optics of vertical pupil slits generally benefit predators, whereas the optics of horizontal slits benefit prey. Vertical slits are better for estimating object distance and distances along the ground—perfect for a predator stalking its prey. In contrast, horizontal slits are better for seeing objects on the horizon—ideal for prey seeing an approaching predator and deciding which way to flee.

    Sci. Adv. 1, el500391

  2. Neuroscience

    Silencing neurons using optogenetics

    1. L. Bryan Ray

    Rhodopsin light-sensitive ion channels from green algae provide a powerful tool to control neuronal circuits. Rhodopsin cation channels effectively depolarize neurons and cause the firing of short-lived electrical membrane potentials. Govorunova et al. describe algal channels that do the opposite; that is, they hyperpolarize or silence particular neurons (see the Perspective by Berndt and Deisseroth). These cation channels provide greater light sensitivity than that of existing hyperpolarizing light-activated channels, operate rapidly, and selectively conduct only anions. This approach is an ideal complement to the widely used technique of creating light-sensitive neurons through the expression of rhodopsin cation channels.

    Science, this issue p. 647; see also p. 590

  3. Statistics

    Testing hypotheses privately

    1. Gilbert Chin

    Large data sets offer a vast scope for testing already-formulated ideas and exploring new ones. Unfortunately, researchers who attempt to do both on the same data set run the risk of making false discoveries, even when testing and exploration are carried out on distinct subsets of data. Based on ideas drawn from differential privacy, Dwork et al. now provide a theoretical solution. Ideas are tested against aggregate information, whereas individual data set components remain confidential. Preserving that privacy also preserves statistical inference validity.

    Science, this issue p. 636

  4. Biological Adhesives

    Keeping it sticky when wet

    1. Marc S. Lavine

    Some biological molecules are remarkably sticky, even to surfaces submerged in water. Mussel adhesion, for example, is based on the overproduction of dihydroxyphenylalanine (DOPA) and proteins with a high abundance of cationic amine residues such as lysine. Using bacterial iron chelators consisting of paired DOPA and lysine groups as analogs for the mussel proteins, Maier et al. show that these two functional groups synergistically enhance interfacial adhesion (see the Perspective by Wilker). The lysine appears to displace hydrated cations from the surface, thus giving a dry patch for better adhesion.

    Science, this issue p. 628; see also p. 582

  5. Paleoecology

    Climate killed off the megafauna

    1. Andrew M. Sugden

    The causes of the Pleistocene extinctions of large numbers of megafaunal species in the Northern Hemisphere remain unclear. A range of evidence points to human hunting, climate change, or a combination of both. Using ancient DNA and detailed paleoclimate data, Cooper et al. report a close relationship between Pleistocene megafaunal extinction events and rapid warming events at the start of interstadial periods. Their analysis strengthens the case for climate change as the key driver of megafaunal extinctions, with human impacts playing a secondary role.

    Science, this issue p. 602

  6. Humoral Immunity

    B cells have a need for speed

    1. Kristen L. Mueller

    High-affinity antibodies provide long-lasting protective immunity against many infections. Generating such antibodies requires help, in the form of T cells, which interact with antibody-producing B cells. As B cells proliferate and mutate their antibody genes, T cells select the cells producing high-affinity antibodies. Gitlin et al. show in mice that B cells that receive T cell help transit through the cell cycle more quickly by increasing the speed at which replication forks progress. Such a rapid cell cycle transition gives high-affinity B cells a selective advantage.

    Science, this issue p. 643

  7. Topological Matter

    Weyl physics emerges in the laboratory

    1. Jelena Stajic

    Weyl fermions—massless particles with half-integer spin—were once mistakenly thought to describe neutrinos. Although not yet observed among elementary particles, Weyl fermions may exist as collective excitations in so-called Weyl semimetals. These materials have an unusual band structure in which the linearly dispersing valence and conduction bands meet at discrete “Weyl points.” Xu et al. used photoemission spectroscopy to identify TaAs as a Weyl semimetal capable of hosting Weyl fermions. In a complementary study, Lu et al. detected the characteristic Weyl points in a photonic crystal. The observation of Weyl physics may enable the discovery of exotic fundamental phenomena.

    Surface of a 3D photonic crystal with four Weyl points in the band structure

    PHOTO: LING LU

    Science, this issue p. 613 and 622

  8. Stroke Treatment

    Randomized clinical trials for mice

    1. Katrina L. Kelner

    To ensure valid conclusions for formal drug approval, the design and analysis of clinical trials are very stringent. Llovera et al. applied the criteria of the gold-standard randomized controlled clinical trial to a preclinical investigation in mice. They tested an antibody to CD49d, which inhibits leukocyte migration into the brain, in two mouse models of stroke. Their six-center randomized controlled study showed that the antibody reduced both leukocyte invasion and infarct volume after a small cortical stroke, but had no effect on larger injuries.

    Sci. Transl. Med. 7, 299ra121 (2015).

  9. Environmental Science

    Deltas are growing centers of risk

    1. Nicholas S. Wigginton

    Population growth, urbanization, and rising sea levels are placing populations living in delta regions under increased risk. The future resiliency and potential for adaptation by these populations depend on a number of socioeconomic and geophysical factors. Tessler et al. examined 48 deltas from around the globe to assess changes in regional vulnerability (see the Perspective by Temmerman). Some deltas in countries with a high gross domestic product will be initially more resilient to these changes, because they can perform expensive maintenance on infrastructure. However, short-term policies will become unsustainable if unaccompanied by long-term investments in all delta regions.

    Science, this issue p. 638; see also p. 588

  10. Neurodegeneration

    Converging paradigms in neurodegeneration

    1. Stella M. Hurtley

    Parkinson's disease and Alzheimer's disease are progressive neurodegenerative diseases with increasing prevalence in our aging populations. Recent evidence suggests that some of the molecular mechanisms involved in the pathology of these diseases have similarities to those observed in infectious prion diseases such as bovine spongiform encephalopathy (mad cow disease). Goedert reviews how the spread of a variety of pathological protein aggregates is involved in neurodegenerative disease.

    Science, this issue p. 601

  11. Charge Transfer

    Improving electron harvesting

    1. Phil Szuromi

    Small metal nanostructures generate electrons from light by creating surface plasmons, which can transfer “hot electrons” to a semiconductor. The efficiency of this process, however, is often low because of electron-electron scattering. Wu et al. demonstrate a pathway that allows the plasmon to directly excite an electron in a strongly coupled semiconductor acceptor (see the Perspective by Kale). Cadmiun selenide nanorods bearing gold nanoparticles on their ends strongly damped plasmons via interfacial electron transfer with a quantum efficiency exceeding 24%.

    Science, this issue p. 632; see also p. 587

  12. Immunodeficiencies

    A surprising immune twist for RORC

    1. Kristen L. Mueller

    The immune system needs its full array of soldiers—including cells and the molecules they secrete—to optimally protect the host. When this isn't the case, minor infections can become chronic or even deadly. Markle et al. report the discovery of seven individuals carrying loss-of-function mutations in RORC, which encodes the transcription factors RORγ and RORγT. These individuals lacked immune cells that produce the cytokine interleukin-17, causing them to suffer from chronic candidiasis. RORC-deficient individuals also exhibited impaired immunity to mycobacterium, probably due to reduced production of the cytokine interferon-γ, a molecule not known to require RORC for its induction.

    Science, this issue p. 606

  13. Rock Physics

    Cementing Roman concrete to a caldera

    1. Brent Grocholski

    Ancient concrete would seem to have little to do with volcano geology. However, Vanorio and Kanitpanyacharoen found similarities between the caprock of the Campi Flegrei caldera near Naples, Italy, and the Roman-era concrete for which the region was known. Both materials require a similar set of chemical reactions to give it the high strength caused by microstructures of intertwining fibrous minerals. The high strength of the natural rock explains the ability of the caldera to withstand periods of high-rate uplift without eruption. The Romans living in the caldera, where the town of Pozzuoli is today, may have been trying to mimic nature to produce this iconic material.

    Science, this issue p. 617

  14. Neurodegeneration

    Mechanistic surprise in ALS-FTD

    1. Stella M. Hurtley

    Intense efforts have focused on identifying therapeutic targets for misfolded proteins that cause amyotrophic lateral sclerosis and frontotemporal dementia (ALS-FTD). Ling et al. show that the main culprit of proteinopathy, TDP-43, acts as a splicing suppressor of nonconserved cryptic exons. These exons often disrupt messenger RNA translation and promote nonsense-mediated decay. When TDP-43 was depleted in cells, a set of nonconserved cryptic exons spliced into target RNAs, leading to down-regulation of corresponding proteins critical for cellular function. Repression of cryptic exons prevented cell death in TDP-43–null cells. Because brains of ALS-FTD cases showed evidence of missplicing of cryptic exons, failure in these regions may underlie TDP-43 proteinopathy.

    Science, this issue p. 650

  15. Device Technology

    Making better contacts

    1. Phil Szuromi

    A key issue in fabricating transistors is making a good electrical contact to the semiconductor gate material. For two-dimensional materials, one route is through a phase transition that converts a hexagonally packed semiconductor phase into a distorted octahedrally packed metallic phase. Cho et al. show that laser heating of molybdenum telluride (MoTe2) achieves this conversion through the creation of Te vacancies. The phase transition improves charge carrier mobility while maintaining the low resistance necessary for improved transistor function.

    Science, this issue p. 625

  16. Cancer

    Semaphorin signals guide metastases

    1. Leslie K. Ferrarelli

    Tumors of patients with metastatic pancreatic ductal adenocarcinoma (PDAC) contain elevated levels of semaphorin 3D, which guides the growth of new blood vessels. Foley et al. found that the protein annexin A2 increased the release of semaphorin from tumor cells from a genetic mouse model of PDAC and promoted migration in these cells. Knockdown of annexin A2 in PDAC cells decreased the ability of these cells to colonize the liver and lungs when injected into mice. These prometastatic effects of annexin A2 did not involve changes in tumor vascularization.

    Sci. Signal. 8, ra77 (2015).

  17. Environmental Science

    Lessons from Deepwater Horizon

    1. Julia Fahrenkamp-Uppenbrink

    The explosion and sinking of the Deepwater Horizon drilling unit caused the largest accidental marine oil spill to date. For almost 3 months in 2010, oil and gas flooded into the Gulf of Mexico. In contrast to previous spills, much of the oil and gas formed deep-water plumes. However, Joye explains how accurate data are lacking on both the amount and ultimate fate of the oil and gas emitted from the well. As deep-water oil and gas exploration continues around the world, ecological baseline data and the implementation of daily flow rate measurements from wells should be a high priority.

    Science, this issue p. 592