This Week in Science

Science  02 Mar 2018:
Vol. 359, Issue 6379, pp. 1004
  1. Adaptation

    Changing coats with the season

    1. Sacha Vignieri

    The Arctic fox molts in the autumn from a dark summer to a white winter coat.

    CREDIT: NATURE PICTURE LIBRARY/ALAMY STOCK PHOTO

    Many species of mammals and birds molt from summer brown to winter white coats to facilitate camouflage. Mills et al. mapped global patterns of seasonal coat color change across eight species including hares, weasels, and foxes. They found regions where individuals molt to white, brown, and both white and brown winter coats. Greater proportions of the populations molted to white in higher latitudes. Regions where seasonal coat changes are the most variable (molting to both brown and white) may provide resilience against the warming climate.

    Science, this issue p. 1033

  2. Tuberculosis

    A trehalose tool for tuberculosis

    1. Caitlin Czajka

    Tuberculosis is the leading infectious killer worldwide. The prevalence of drug- and multidrug-resistant Mycobacterium tuberculosis necessitates more rapid and specific diagnostics. Kamariza et al. designed a color-changing dye based on trehalose, a sugar that makes up the outer membrane of M. tuberculosis. The dye stained live bacteria within minutes, emitting fluorescence upon incorporation into the hydrophobic mycobacterial membrane. Heat-inactivated bacteria did not fluoresce, and drug-treated bacteria emitted reduced fluorescence. This trehalose-based dye does not require sample washing and emits minimal background fluorescence, potentially making it particularly useful for the rapid detection of metabolically active M. tuberculosis in resource-limited environments.

    Sci. Transl. Med. 10, eaam6310 (2018).

  3. Geology

    Mudrocks get a vegetative assist

    1. Brent Grocholski

    Mudrocks such as slate and shale are rarely found in stratigraphy older than about 500 million years. McMahon and Davies compiled a large database of mudrock occurrence over the past 3.5 billion years to help assess the origin of this ubiquitous rock type (see the Perspective by Fischer). Mudrocks appeared at the same time as did deep-rooted land plants. The interplay between plants and sedimentary rocks suggests that a change in erosion rate and the chemistry of sediments delivered to the oceans occurred around 500 million years ago.

    Science, this issue p. 1022; see also p. 994

  4. Molecular Biology

    Tracking regulatory DNA in action

    1. Steve Mao

    Cis-regulatory DNA elements such as enhancers and promoters are critical for transcription regulation. Little is known about the relationship between these elements' transcriptional activity and their mobility within the nucleus in living cells. Gu et al. developed a strategy to deliver multiple RNAs to guide inactive Cas9 to label these elements. Quantitative measurement of their movement during stem cell differentiation revealed that increased DNA loci mobility correlated with transcriptional activation.

    Science, this issue p. 1050

  5. Neurophysiology

    The proton channel behind sour taste

    1. L. Bryan Ray

    Although many proteins that form ion channels in cell membranes have been described, none that selectively conduct protons into eukaryotic cells have been identified. Tu et al. used a genetic screen to pinpoint candidate genes that might encode such a protein from mouse taste receptor cells (see the Perspective by Montell). They identified the known protein otopetrin and showed that it conferred proton conductance when expressed in cultured human cells. Their results indicate that otopetrin may function in sensory recognition of sour (acidic) taste in humans and other organisms.

    Science, this issue p. 1047; see also p. 991

  6. Astronomy

    Advancing astronomy, one screen saver at a time

    1. Warren Warren

    One of the major challenges of modern astronomy is finding important results in the overwhelming volume of acquired data. Clark et al. used the computers of tens of thousands of volunteers participating in the Einstein@Home project to search Fermi Large Area Telescope data. Their goal was to discover radio-quiet gamma-ray millisecond pulsars (MSPs). More than 10,000 donated CPU years in this survey led to the discovery of two isolated MSPs, including a rotation-powered MSP that has remained undetected in radio observations.

    Sci. Adv. 10.1126/sciadv.aao7228 (2018).

  7. Medical Robots

    Individually optimized exosuit

    1. Rachel Kline

    Like a regular suit, a wearable exosuit can be customized for the individual. Ding et al. tested a hip-extension device on eight adult male volunteers. The device reduced the energy required to walk, and the authors' approach tailored the assistance for each wearer. They applied a Bayesian algorithm that could rapidly find optimal settings. Optimization reduced the metabolic cost of walking by 17.4%, improving on existing devices by more than 60%. Optimal settings varied between the participants, suggesting that customizing assistance is better than a one-size-fits-all approach.

    Sci. Robot. 3, eaar5438 (2018).

  8. Organic Chemistry

    Guiding nitrenes away from a migration

    1. Jake Yeston

    Nitrogen conventionally shares its electrons in three bonds with one or more partners. A singly bonded nitrogen, or nitrene, is exceptionally reactive and can insert itself into normally inert C–H bonds. If the nitrene forms next to a carbonyl center, though, it tends to react with the C–C bond on the other side instead. Hong et al. used theory to guide the design of an iridium catalyst that inhibits this rearrangement, steering the nitrene toward C–H insertion to form a variety of useful lactam rings.

    Science, this issue p. 1016

  9. Evolution

    Ratcheting up wild virulence

    1. Caroline Ash

    Partially protective vaccination can sometimes select for increasingly virulent pathogens. Fleming-Davies et al. asked what happens in a natural system. In the United States, the house finch population is suffering an increasingly virulent epidemic caused by Mycoplasma gallisepticum. The pathogen induces incomplete immunity that clears less virulent pathogens and offers partial protection against strains of greater virulence. In the birds, the partial immune response does away with competition from the less virulent pathogens. The partial immunity of the host also hinders replication of the more virulent pathogens enough to allow some birds to survive. This allows increasingly virulent forms of the pathogen to be transmitted.

    Science, this issue p. 1030

  10. Science Community

    The whys and wherefores of SciSci

    1. Barbara R. Jasny

    The science of science (SciSci) is based on a transdisciplinary approach that uses large data sets to study the mechanisms underlying the doing of science—from the choice of a research problem to career trajectories and progress within a field. In a Review, Fortunato et al. explain that the underlying rationale is that with a deeper understanding of the precursors of impactful science, it will be possible to develop systems and policies that improve each scientist's ability to succeed and enhance the prospects of science as a whole.

    Science, this issue p. eaao0185

  11. Neuroscience

    How to select and shape neural activity

    1. Peter Stern

    When we learn a new skill or task, our movements are reinforced and shaped. Learning occurs because the neural activity patterns in the movement control–related brain regions that are rewarded are repeated. But how does this reinforcement work? Athalye et al. developed a closed-loop self-stimulation paradigm in which a target motor cortical activity pattern resulted in the optogenetic stimulation of dopaminergic neurons. With training, mice learned to reenter specific neuronal activity patterns, which triggered self-stimulation and shaped their neural activity to be closer to the target pattern.

    Science, this issue p. 1024

  12. Microbiology

    Maps of defense arsenals in microbial genomes

    1. Steve Mao

    To survive the attack of foreign invaders such as viruses and plasmids, bacteria and archaea fight back with immune systems that are usually clustered in “defense islands” in their genomes. Doron et al. took advantage of this property to map microbial defense systems systematically (see the Perspective by Kim). Candidate immune systems were then experimentally validated for their activities. Like well-known defense arsenals such as restriction-modification and CRISPR systems, these additional immune systems now require mechanistic investigation and could potentially be engineered into useful molecular tools in the future.

    Science, this issue p. eaar4120; see also p. 993

  13. Optics

    Exploring photonic topology

    1. Ian S. Osborne

    Scattering topological effects are being explored in a variety of electronic and optical materials systems owing to their robustness against defects (see the Perspective by Özdemir). Yang et al. designed and fabricated an ideal optical analog of a three-dimensional Weyl system. Angular transmission measurements revealed four Weyl points at the same energy, as well as the signature helicoidal arcs associated with such an exotic topological system. Zhou et al. theoretically proposed and experimentally demonstrated the formation of a topologically protected bulk Fermi arc. They attributed the formation of the arc to the topological nature of paired exceptional points (points at which gain and loss in the system are matched). Photonic crystals may provide a powerful platform for studying exotic properties of topological electronic systems and may also be used to develop optical devices that exploit topological properties of light-matter interactions.

    Science, this issue p. 1013, p. 1009; see also p. 995

  14. Protein Design

    Membrane protein oligomers by design

    1. Valda Vinson

    In recent years, soluble protein design has achieved successes such as artificial enzymes and large protein cages. Membrane proteins present a considerable design challenge, but here too there have been advances, including the design of a zinc-transporting tetramer. Lu et al. report the design of stable transmembrane monomers, homodimers, trimers, and tetramers with up to eight membrane-spanning regions in an oligomer. The designed proteins adopted the target oligomerization state and localized to the predicted cellular membranes, and crystal structures of the designed dimer and tetramer reflected the design models.

    Science, this issue p. 1042

  15. Neuroimmunology

    An off switch for helminth immunity

    1. Priscilla N. Kelly

    Group 2 innate lymphoid cells (ILC2s) are involved in responses to helminths, viruses, and allergens. Moriyama et al. found that ILC2s interact with the nervous system to modulate helminth immunity. ILC2s from the small intestine expressed the β2-adrenergic receptor (β2AR), which normally interacts with the neurotransmitter epinephrine. Inactivating β2AR resulted in lower helminth burden and more ILC2s, eosinophils, and type 2 cytokine production in mice. Conversely, treatment of helminth-infected mice with a β2AR agonist enhanced worm burden and reduced proliferation of ILC2s. Thus, β2AR negatively regulates ILC2-driven protective immunity.

    Science, this issue p. 1056

  16. Immune Engineering

    Engineering cytokine-receptor pairs

    1. Priscilla N. Kelly

    Interleukin-2 (IL-2) is an important cytokine that helps T cells destroy tumors and virus-infected cells. IL-2 has great therapeutic promise but is limited by toxic side effects and its capacity to both activate and repress immune responses. Sockolosky et al. set out to improve IL-2–based immunotherapy by engineering synthetic IL-2–receptor pairs (i.e., IL-2 and its receptor, IL-2R) (see the Perspective by Mackall). Engineered complexes transmitted IL-2 signals but only interacted with each other and not with endogenous IL-2/IL-2R. Treatment of mice with IL-2 improved the ability of engineered T cells to reject tumors with no obvious side effects. This type of approach may provide a way to mitigate toxicities associated with some cytokine-based immunotherapies.

    Science, this issue p. 1037; see also p. 990

  17. Ecology

    Fostering the resilience of ecosystems

    1. Julia Fahrenkamp-Uppenbrink

    What makes an ecosystem resilient to environmental change? Answering this question is increasingly important as climate change and other stressors affect ecosystems around the world. But, as Willis et al. explain in a Perspective, identifying resilient ecosystems and determining the factors behind their resilience can be difficult. Focusing on tropical ecosystems, the authors outline the many biotic and abiotic factors contributing to resilience and highlight recent studies that provide pointers for future research and conservation aimed at fostering resilience. In another Perspective, Darling and Côté discuss whether coral reef ecosystems might be protected through conservation approaches and technological interventions focused on increasing their resilience.

    Science, this issue p. 988, p. 986

  18. Allergy

    Dectin-1 limits allergic responses

    1. Anand Balasubramani

    Aberrant activation of pattern recognition receptors (PRRs) drives inflammation in autoimmune and allergic diseases. Gour et al. identified invertebrate tropomyosin from house dust mites and shrimp as a ligand for dectin-1. Dectin-1 is a PRR that recognizes fungal β-glucans in antifungal immune responses. Engagement of dectin-1 by invertebrate tropomyosins limited type 2 inflammation, and dectin-1–deficient mice were more prone to allergic airway inflammation. Furthermore, expression of dectin-1 was repressed in allergic individuals. Thus, dectin-1 is important in limiting allergic responses.

    Sci. Immunol. 3, eaam9841 (2018).

  19. Inflammation

    Tracking inflammation in the colon

    1. John F. Foley

    The therapeutic options for ulcerative colitis, a form of inflammatory bowel disease, are limited. Lyons et al. tracked gene expression, protein levels, and protein phosphorylation in individual animals in a mouse model of colitis. Computational analysis of the data sets identified discrepancies between transcriptomic and proteomic measurements and predicted that the kinase Pak1 mediated colonic inflammation. Treatment of mice with a pharmacological inhibitor of Pak1 ameliorated disease, highlighting the importance of proteomic measurement to the understanding of disease pathogenesis.

    Sci. Signal. 11, eaan3580 (2018).