This Week in Science

Science  07 Jun 2019:
Vol. 364, Issue 6444, pp. 966
  1. Steroid Hormones

    An evolutionary change in ligand

    1. John F. Foley

    The mineralocorticoid receptor in the elephant shark (Callorhinchus milii) responds to progesterone.

    CREDIT: MARINETHEMES.COM/KELVIN AITKIN

    Aldosterone binds to mammalian mineralocorticoid receptors to regulate electrolyte homeostasis. However, the mineralocorticoid receptor first arose in cartilaginous fish, which do not have aldosterone. Katsu et al. found that the mineralocorticoid receptor of the elephant shark, a cartilaginous fish found in the oldest group of jawed vertebrates, was activated by progesterone, which is an antagonist of the human mineralocorticoid receptor. These findings suggest that mineralocorticoid receptors may play an unappreciated role in reproductive physiology.

    Sci. Signal. 12, eaar2668 (2019).

  2. Physics

    Something repulsive in the Casimir effect

    1. Ian S. Osborne

    Two uncharged objects (metal plates for instance) will experience an attractive force between them, the magnitude of which increases as they are brought closer together. This force, or Casimir effect, is caused by vacuum fluctuations of the electromagnetic field. Effectively, more modes outside than between the objects results in the objects being pushed together. Zhao et al. show that the extent of the electromagnetic fluctuations can be controlled by coating one of the objects with a dielectric (Teflon), which changes the Casimir effect to a repulsive force at small distances. This then cancels out the force between plates and produces a point of stable equilibrium.

    Science, this issue p. 984

  3. Superconductivity

    Decoding the halo pattern

    1. Jelena Stajic

    Magnetic fields can cause the formation of vortices in a superconductor. In cuprate superconductors, the vortex cores are surrounded by “halos,” where the density of electronic states exhibits a checkerboard pattern. Edkins et al. used scanning tunneling spectroscopy to take a closer look into the halos. The results revealed that the patterns correspond to an exotic state called the pair density wave, in which the density of finite momentum Cooper pairs is spatially modulated.

    Science, this issue p. 976

  4. Radio Astronomy

    A radio ridge between two galaxy clusters

    1. Keith T. Smith

    Galaxy clusters contain dozens or hundreds of galaxies, vast quantities of hot gas, and large amounts of dark matter. The gas can emit at radio wavelengths if it contains electrons at relativistic speeds, which can be injected by active galaxies or accelerated during a merger between two clusters. Govoni et al. used the Low-Frequency Array (LOFAR) radio telescope to observe a ridge of radio-emitting plasma extending between two galaxy clusters that are approaching a merger. The results imply that intergalactic magnetic fields connect the two clusters and challenge theories of particle acceleration in the intergalactic medium.

    Science, this issue p. 981

  5. Paleobotany

    Fossil Fagaceae from Patagonia

    1. Andrew M. Sugden

    The oak family Fagaceae is thought to have its evolutionary origins in northern temperate forests and Southeast Asia. Wilf et al. now report 52-million-year-old fossils from the Southern Hemisphere belonging to the still-living genus Castanopsis. Hypotheses of Fagaceae origins have focused only on the Northern Hemisphere. Ancestral Castanopsis may represent one of numerous paleo-Antarctic plant genera that are found with Castanopsis today in Southeast Asian rainforests.

    Science, this issue p. eaaw5139

  6. Malaria

    Targeting malaria transmission

    1. Lindsey Pujanandez

    To effectively block transmission of Plasmodium falciparum, vaccines must target appropriate antigens. To identify candidate antigens, Dantzler et al. studied immune responses from large cohorts of people who had been infected with P. falciparum. Multiple complementary assays revealed how antibodies recognize gametocytes, the sexual stage that allows transmission from human blood into mosquitoes. Interesting antigens were present in immature gametocytes, with a subset conserved among P. falciparum strains. Natural immunity to these antigens indicates that an appropriately designed vaccine could potentially interfere with malaria transmission.

    Sci. Transl. Med. 11, eaav3963 (2019).

  7. Global Warming

    Keep cool and carry on

    1. Aaron Clauset,
    2. Kollen Post

    The current trajectory of global warming is predicted to lead to an increase in global mean temperatures greater than preindustrial levels of 2.6° to 3.1°C by 2100. The Paris Agreement aims to keep that number below 2°C, with recent efforts pushing signatories to ratchet up those ambitions and stay below 1.5°C. Lo et al. assessed data on both climate and heat-related mortality from 15 major U.S. cities. They found that the current Paris Agreement limit should result in substantial reductions in mortality in all of these cities except for Atlanta, with Philadelphia seeing the greatest drop in heat-related deaths at 3.1%. Achieving the more ambitious 1.5°C target would translate into an estimated reduction in annual deaths of between 110 and 2720 per city.

    Sci. Adv. 10.1126/sciadv.aau4373 (2019).

  8. Neurodevelopment

    Brain map of touch sensation

    1. Pamela J. Hines

    The brain's somatosensory cortex contains a topographical map that reflects touch sensation inputs. During embryonic development, axons from the midbrain thalamus build columnar connections to the cortex in the absence of sensory input. Working in mice, Antón-Bolaños et al. found that these thalamocortical connections are responsible for organizing the somatosensory cortex (see the Perspective by Tiriac and Feller). Organization of the map in the cortex depends on spontaneous calcium waves in the embryonic thalamus. Thus, the somatosensory map is sketched out before actual sensory input begins to refine the details.

    Science, this issue p. 987; see also p. 933

  9. Neuroscience

    This is safe, you can eat it

    1. Peter Stern

    Social transmission of food preference is a model for studying nonspatial memory. In mice, a signal that food is safe to eat is transmitted by its smell along with molecules in the breath of a conspecific. How the odor itself is encoded and assigned valence is poorly understood. Loureiro et al. found a monosynaptic pathway between two brain areas, the piriform cortex and the medial prefrontal cortex, that plays a central role in this process. This connection strengthens during social interaction, thereby allowing a mouse to provide a food safety message to its companion.

    Science, this issue p. 991

  10. Human Genetics

    Somatic mosaicism in normal tissues

    1. Laura M. Zahn

    Somatic cells can accumulate mutations over the course of an individual's lifetime. This generates cells that differ genetically at specific loci within the genome. To explore how this genetic diversity in individuals contributes to disease, Yizhak et al. developed a method to detect mutations from RNA sequencing data (see the Perspective by Tomasetti). Applying this method to Cancer Genome Atlas samples and normal samples from the Genotype-Tissue Expression (GTEx) project generated a tissue-specific study of mutation accumulation. Somatic mutations were detected in nearly all individuals and across many normal human tissues in genomic regions called cancer hotspots and in genes that play a role in cancer. Interestingly, the skin, lung, and esophagus exhibited the most mutations, suggesting that the environment generates many human mutations.

    Science, this issue p. eaaw0726; see also p. 938

  11. Neurodevelopment

    Binary decisions refine fate decisions

    1. Pamela J. Hines

    Neural crest cells develop into tissues ranging from craniofacial bones to peripheral neurons. Combining single-cell RNA sequencing with spatial transcriptomics, Soldatov et al. analyzed how neural crest cells in mouse embryos decide among the various fates available to them (see the Perspective by Mayor). These multipotent cells become biased toward a given fate early on and step through a progression of binary decisions as their fate is refined. Competing fate programs coexist until increased synchronization favors one and repression disfavors the other.

    Science, this issue p. eaas9536; see also p. 937

  12. Ice Sheets

    An uplifting effect

    1. H. Jesse Smith

    The rise in sea level that is occurring from the melting of Antarctica is only going to accelerate as climate warms. However, Larour et al. report that crustal uplift in the Amundsen Sea sector is helping to reduce grounding line retreat, thereby stabilizing the ice sheet and slowing its rate of mass loss (see the Perspective by Steig). This effect will not stop or reverse ice sheet loss, but it could delay the progress of dynamic mass loss of Thwaites Glacier by approximately 20 years.

    Science, this issue p. eaav7908; see also p. 936

  13. Magnetism

    A detailed look into 2D magnetism

    1. Jelena Stajic

    The van der Waals material chromium triiodide (CrI3) is a ferromagnet in the bulk but appears to become antiferromagnetic when thinned to a few atomic layers. Thiel et al. used a local magnetometry technique based on diamond nitrogen-vacancy centers to study the magnetism of these thin films at the nanoscale (see the Perspective by Fernández-Rossier). In agreement with previous results, films with odd numbers of layers had magnetization values consistent with that of a single layer, indicating antiferromagnetic coupling. But when the researchers' probe caused an accidental puncture, the magnetization of a nine-layer film increased approximately ninefold to a value expected in a ferromagnetic material. Further characterization suggested that the puncture had caused a structural transition, linking the structural and magnetic properties of this enigmatic system.

    Science, this issue p. 973; see also p. 935

  14. Climate

    Why is methane rising?

    1. Julia Fahrenkamp-Uppenbrink

    Methane is a powerful greenhouse gas that is emitted through both natural and human-driven processes. In a Perspective, Mikaloff Fletcher and Schaefer highlight recent evidence for a rapid rise in the amount of methane emitted to Earth's atmosphere. This rise began in 2007 and accelerated in 2014. Isotope measurements suggest that the likely culprits include rising emissions from livestock and from burning fossil fuels. If the rise in methane continues, then even larger reductions in other greenhouse gas emissions will be required to limit climate warming to 1.5° or 2°C, as required under the 2015 Paris Agreement.

    Science, this issue p. 932

  15. Immunotherapy

    Tempering dendritic cell activation

    1. Anand Balasubramani

    Checkpoint blockade targeting cytotoxic T lymphocyte associated protein 4 (CTLA-4) and programed cell death 1 (PD-1) have changed the landscape of cancer therapeutics. However, much remains to be learned about the biology of these molecules. CTLA-4 expressed on T cells captures costimulatory molecules CD80 and CD86 from antigen-presenting cells by transendocytosis to inhibit CD28-mediated costimulation of T cell activation. Ovcinnikovs et al. report that regulatory T cells (Tregs) outperform conventional T cells in their ability to transendocytose CD80 and CD86 and that migratory dendritic cells are the main population targeted by Treg-expressed CTLA-4 in vivo. These findings elucidate why CTLA-4 expressed on Tregs is so central in maintaining immune homeostasis.

    Sci. Immunol. 4, eaaw0902 (2019).