This Week in Science

Science  05 Mar 2021:
Vol. 371, Issue 6533, pp. 1004
  1. Insect Declines

    Warming autumns, fewer butterflies

    1. Sacha Vignieri

    Butterflies such as the great purple hairstreak, Atlides halesus, are in decline in the warming American West according to community surveys.

    PHOTO: JEFFREY GLASSBERG/NORTH AMERICAN BUTTERFLY ASSOCIATION

    Many recent studies have revealed sweeping declines in insects over the past few decades. Butterflies are no exception. Forister et al. used three different datasets, collected by both experts and community scientists, and found that the number of butterflies has declined over the past 40 years. Although the drivers of decline are complex, the authors found that climate change—in particular, warmer months in the autumn—explain a large portion, even as warming summers actually lead to increases. This work shows that climate change impacts may be insidious and unexpected in their effects.

    Science, this issue p. 1042

  2. Metallurgy

    A two-stage lightweighting

    1. Brent Grocholski

    Dealloying allows voids to be created in metals, decreasing the weight of the material. However, when the solid fraction is below about 30%, the mechanical properties rapidly degrade. Shi et al. discovered that two dealloying steps allow for the creation of a silver-gold alloy with a solid fraction as low as 12%. Unexpectedly, this process does not degrade the mechanical properties while allowing for large samples to be synthesized. The strategy should be applicable to other alloy systems, providing a pathway for creating strong and lightweight materials.

    Science, this issue p. 1026

  3. Exoplanets

    A transiting rocky planet 8 parsecs away

    1. Keith T. Smith

    Most exoplanets have been detected using either the radial velocity (RV) method or the transit method, which provide only limited information on the planet's physical properties. In the rare cases in which both methods detect the same planet, the combination determines the planet's mass, radius, and density. Trifonov et al. identified a planet, Gliese 486 b, using both RV and transit data. The host star is a red dwarf only 8 parsecs away, making this one of the closest exoplanet systems known. A rocky super-Earth, Gliese 486 b has an equilibrium surface temperature of 700 kelvin. The authors say that it is observationally favorable for searches for an atmosphere.

    Science, this issue p. 1038

  4. Spectroscopy

    Electron dynamics in time and space

    1. Yury Suleymanov

    Following molecular excitation and electron transfer processes in time and space within a single experiment is a long-standing goal of spectroscopy in the field of chemistry. Wallauer et al. combined tomographic photoemission imaging with a femtosecond pump-probe scheme to trace the excited state molecular orbitals of surface-adsorbed molecules with both spatial and temporal resolution. The present demonstration opens a new window for investigating the ultrafast electron transfer dynamics in such processes as chemical reactions on surfaces and intermolecular charge transfers.

    Science, this issue p. 1056

  5. Microbiology

    Phenazines liberate phosphate

    1. Michael A. Funk

    Bacteria secrete a wide range of small molecules with chemical reactivity that offers multiple functions in different contexts. Phenazines are commonly considered to be antibiotics, but they can also participate in environmental redox reactions, especially with iron. McRose and Newman found that phenazines, when added exogenously or made by bacteria in situ, can liberate phosphorous (P) in the form of phosphate from mineral surfaces, and that the production of these molecules is regulated by signaling pathways that respond to P limitation. Strains unable to produce these molecules grew more slowly under P limitation but could be rescued by the addition of exogenous phenazines. The authors hypothesize that reductive dissolution of iron oxides has the benefit of liberating P, and that this could be one mechanism of microbial P acquisition in some environments.

    Science, this issue p. 1033

  6. Influenza

    Toward a universal influenza vaccine

    1. Courtney S. Malo

    The development of a universal influenza vaccine is of paramount importance because seasonal vaccines vary in terms of protection. Darricarrère et al. have now moved a universal influenza vaccine one step closer to the clinic. The authors vaccinated nonhuman primates with headless hemagglutinin-stabilized stem antigens presented on ferritin nanoparticles. The vaccines elicited antibodies that neutralized a diverse array of influenza strains, suggesting that they would provide broad protection against influenza infection in vivo. These vaccines, which are now in clinical trials, are promising candidates as broadly protective influenza vaccines.

    Sci. Transl. Med. 13, eabe5449 (2021).

  7. Physiology

    The source of the leak in sepsis

    1. Wei Wong

    A challenge in treating the systemic inflammation that occurs in sepsis is the increase in endothelial permeability that leads to widespread tissue edema and immune cell infiltration. Maier-Begandt et al. uncovered a pathway activated specifically in veins by tumor necrosis factor–α (TNFα), a proinflammatory cytokine whose circulating levels increase greatly during sepsis. TNFα treatment resulted in the activation of Pannexin 1 channels, which ultimately led to disrupted tight junctions in veins but not in arteries. Sepsis induced less lung edema and was less fatal to Pannexin 1–deficient mice compared with control mice.

    Sci. Signal. 14, eaba2940 (2021).

  8. Hematology

    A red-letter day for RBC research

    1. Seth Thomas Scanlon

    Colored scanning electron microscopy image of sickle cell red blood cells

    CREDIT: CDC/JANICE HANEY CARR/SCIENCE SOURCE

    The study of primary human red blood cell (huRBC) disorders such as sickle cell disease (SCD) and infectious diseases such as malaria has been hampered by a lack of in vivo models of human erythropoiesis. Song et al. transferred human fetal liver cells into MISTRG mice, which are immunodeficient and are genetically engineered with several human genes involved in hematopoiesis. This approach was unsuccessful because mature huRBCs are rapidly destroyed in the mouse liver. They then used CRISPR-Cas9 to mutate these mice into a fumarylacetoacetate hydrolase–deficient strain, allowing them to replace the mouse liver with engrafted human hepatocytes. These mice exhibited enhanced human erythropoiesis and circulating huRBC survival and could recapitulate SCD pathology when reconstituted with SCD-derived HSCs.

    Science, this issue p. 1019

  9. Infectious Disease

    Nature's “responsible” response to disease

    1. Sacha Vignieri

    With the emergence of the COVID-19 pandemic, there have been global calls for the implementation of “social distancing” to control transmission. Throughout the world, some have resisted this requirement with the unfounded argument that it is unnecessary or ineffective. Social distancing, however, is a natural consequence of disease across animals, both human and nonhuman. Stockmaier et al. reviewed responses to disease across animal taxa and reveal how these responses naturally limit disease transmission. Understanding such natural responses and their impacts on pathogenic transmission provides epidemiological insight into our own responses to pandemic challenges.

    Science, this issue p. eabc8881

  10. Sperm Genomics

    Sperm-specific natural selection

    1. Laura M. Zahn

    Sperm cells are genetically haploid, but because of the cytoplasmic bridges that link cells, they can be transcriptionally diploid. However, some gene transcripts are not shared. Bhutani et al. sequenced single sperm from mice, cattle, and macaques to determine the extent of distortion in the expression of these putatively selfish transcripts, which the authors call genoinformative markers (GIMs). Investigating the evolutionary pressures on these GIMs, they found that they exhibited signatures of positive selection yet tend to be biased toward sperm function. This observation explains why, relative to other tissues, testis shows distinctive gene expression patterns.

    Science, this issue p. eabb1723

  11. Cancer

    Turning a tumor suppressor into a target

    1. Yevgeniya Nusinovich

    Tumor-suppressor genes such as TP53 (tumor protein P53) play key roles in the pathogenesis of cancer but, unfortunately, they are difficult to target because they do not create an overactive protein that can be inhibited with a drug. Hsiue et al. discovered a way to target a cancer-associated mutant form of the p53 protein using the body's own immune system (see the Perspective by Weidanz). The authors identified a distinct fragment of this mutant protein, characterized the structural basis for its presentation to T cells, and designed a bispecific antibody to stimulate T cell killing of p53-mutant cancer cells.

    Science, this issue p. eabc8697; see also p. 996

  12. Enzyme Evolution

    Some like it hot, others not

    1. Michael A. Funk

    Enzymes strike a delicate balance between features that enhance chemical reactivity and those that contribute to stable structure. Both features are important and can be unrelated or antagonistic. Pinney et al. combined rich experimental work on thermophilic and mesophilic variants of the enzyme ketosteroid isomerase (KSI) with bioinformatic data from a diverse set of bacterial enzymes to reveal the molecular determinants of thermal adaptation in enzymes. For KSI, they observed a trade-off between activity and thermal stability that comes down to a single active-site residue. With their larger dataset, they identified patterns of individual amino acid substitutions that are favored at higher temperatures, and also consider how networks of stabilizing interactions develop.

    Science, this issue p. eaay2784

  13. Structural Biology

    A cellular cholesterol sensor

    1. Valda Vinson

    Cholesterol levels in cells are controlled by the sterol regulatory element–binding protein (SREBP) pathway. When the cell has sufficient cholesterol, the transcription factor that regulates cholesterol metabolism is sequestered at the endoplasmic reticulum membrane, but when cholesterol is depleted, the transcription factor is released to activate the expression of genes involved in cholesterol synthesis and uptake. Yan et al. determined the structure of a central complex in human SREBP containing the proteins Scap and Insig-2. These two membrane-embedded proteins undergo 25-hydroxycholesterol (25HC)–dependent association and must dissociate for the pathway to be activated. The structure shows that 25HC is sandwiched between Scap and Insig-2 to facilitate their association. A mutational analysis is consistent with the structural model.

    Science, this issue p. eabb2224

  14. Heart Development

    Forming the early heart

    1. Beverly A. Purnell

    The heart is the first organ to form during development and is critical for the survival of the embryo. The precise molecular identities of the various cell types that make up the heart during these early stages remain poorly defined. Tyser et al. used a combination of transcriptomic, imaging, and genetic lineage–labeling approaches to profile the molecular identity and precise locations of cells involved in the formation of the mouse embryonic heart. This approach allowed them to identify the earliest known progenitor of the epicardium, the outermost layer of the heart, which is an important source of signals and cells during cardiac development and injury.

    Science, this issue p. eabb2986

  15. Immunology

    Macrophages seal 'em in the coelom

    1. Seth Thomas Scanlon

    GATA6+ macrophages resident in body cavities exhibit both phagocytic and repair functions. However, the mechanisms by which these cells can identify and migrate to sites of injury have remained unclear. Using intravital imaging of mouse peritoneal cavities, Zindel et al. report that GATA6+ macrophages rapidly assemble clot-like structures in a process strongly analogous to thrombosis (see the Perspective by Herrick and Allen). The formation of these aggregates requires the expression of macrophage scavenger receptor domains and acts to plug wounds and promote healing. This pathway can be inadvertently activated during medical procedures, when macrophage aggregates can promote the generation of abdominal scar tissue known as adhesions. Inhibition of macrophage scavenger receptors may therefore be a useful therapeutic approach after surgeries that cause injury to body cavities.

    Science, this issue p. eabe0595; see also p. 993

  16. Climate Variability

    A volcanic source of variation

    1. H. Jesse Smith

    The Atlantic Multidecadal Oscillation (AMO), a 50- to 70-year quasiperiodic variation of climate centered in the North Atlantic region, was long thought to be an internal oscillation of the climate system. Mann et al. now show that this variation is forced externally by episodes of high-amplitude explosive volcanism. They used an ensemble of climate models to evaluate the causes of the AMO, finding that volcanos are the most important influence, and that there is no evidence to show that it has been internally generated during the last millennium.

    Science, this issue p. 1014

  17. Ferroelectrics

    Polarization hits a bull's-eye

    1. Brent Grocholski

    Polymer-based ferroelectric materials are attractive because they can be solution processed cheaply and have much greater flexibility than ceramics. Guo et al. found concentric circular bands of polarization in a ferroelectric polymer that look like a bull's-eye target (see the Perspective by Martin). This self-organized toroidal texture is aligned perpendicularly to the axis of the polymer chains, allowing the authors to demonstrate selective absorption of infrared radiation and manipulation of terahertz radiation. This distinct structure in a polymer could be of interest for exploring and using other exotic effects.

    Science, this issue p. 1050; see also p. 992

  18. Black Holes

    A heavy black hole in an x-ray binary

    1. Keith T. Smith

    If a black hole interacts with a binary companion star, the system emits x-rays and can form a radio jet. The masses of black holes in these x-ray binaries are all lower than those detected using gravitational waves, challenging models of black hole formation from massive stars. Miller-Jones et al. used radio astrometry to refine the distance to Cygnus X-1, a well-studied x-ray binary. They found a larger distance than previous estimates, raising the mass of the black hole in the system to 21 solar masses. The results challenge the wind mass loss rates implemented in stellar evolution models.

    Science, this issue p. 1046

  19. Sensory Perception

    A new way to “see” color

    1. Sacha Vignieri

    Color perception is an important aspect of the way many organisms navigate their world. The ability to perceive color has thus far thought to depend on the presence of either eyes or minimally receptive cells containing opsin receptor genes. Ghosh et al. show that foraging Caenorhabditis elegans roundworms, which do not have eyes or opsins, can distinguish a blue color indicative of a toxin released by bacterial mats (see the Perspective by Neal and Vosshall). They suggest that the worms do this through the detection of the ratio between blue and amber light, a process dependent on at least two cellular stress-response genes. Different strains of C. elegans responded to different ratios, suggesting that this pathway plays an ecological role.

    Science, this issue p. 1059; see also p. 995

  20. T Cells

    Co-opting erythrocyte clearance

    1. Claire Olingy

    Whereas T cell dysfunction contributes to immune evasion in cancer and chronic viral infection, strategies that induce dysfunction in autoreactive T cells may facilitate self-tolerance. Watkins et al. used phage display to identify a human antibody fragment (Fab) that selectively binds erythrocytes, enabling efficient antigen targeting to splenic antigen-presenting cells that rapidly clear apoptotic erythrocytes. Fab-tethered antigen induced antigen-specific T cell dysfunction in mice that was sustained in response to antigen rechallenge for at least 3 months and required Batf3-dependent dendritic cells. In a mouse model of experimental autoimmune encephalomyelitis, erythrocyte-targeted antigen prevented encephalogenic T cells from contributing to autoimmune pathology, demonstrating the therapeutic potential of leveraging erythrocyte clearance pathways to disarm overactive T cells.

    Sci. Immunol. 6, eabe1801 (2021).

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