This Week in Science

Science  10 Jul 2020:
Vol. 369, Issue 6500, pp. 154
  1. Paleontology

    Teeth and jaws

    1. Sacha Vignieri

    Lingual (from inside out) tooth addition, observed in modern fishes such as this great white shark, has now also been observed in fossils of basal jawed vertebrates.

    CREDIT: DAVID FLEETHAM/ALAMY STOCK PHOTO

    The first vertebrates were jawless, much like a modern hagfish. There has been a lot of interest in how these forms transitioned to having jaws like most of their descendants, including humans. Much of our understanding of this process has focused on how the teeth are replaced relative to the jaw. Previous theories suggested that tooth growth that occurred lingually—or from inside out as in modern fishes—was a derived condition. Vaškaninová et al. vertebrates, suggesting that it may have been ancestral.

    Science, this issue p. 211

  2. Structural Biology

    Engineering a toxin

    1. Valda Vinson

    Developing drugs that target a specific subtype in a G protein–coupled receptor (GPCR) family is a major challenge. Maeda et al. examined the basis of specificity of a snake venom toxin binding to muscarinic acetylcholine receptors (MAChRs), which mediate many functions of the central and parasympathetic nervous systems. They determined a structure that shows why the mamba venom toxin MT7 is specific for one receptor, M1AChR, and also explains how it inhibits downstream signaling. Based on this structure, they engineered MT7 to be selective for another receptor, M2AChR, instead of M1ChR. The toxin may present a promising scaffold for developing specific GPCR modulators.

    Science, this issue p. 161

  3. Biochemistry

    Conserved redox regulation of kinases

    1. Leslie K. Ferrarelli

    The effects of pathological oxidative stress are partially mediated through functional modification of various proteins. A pair of papers show that the oxidation of kinases at evolutionarily conserved cysteine residues regulates cell metabolism and mitosis. Shrestha et al. found that oxidation of the diabetes-associated metabolic kinase FN3K promoted its functional oligomerization and altered cellular redox status. Byrne et al. found that oxidation of mitotic kinases in human cells and yeast suppressed kinase catalytic activity and impaired cellular division in yeast.

    Sci. Signal 13, eaax6313, eaax2713 (2020).

  4. Bioengineering

    Beneficial bioartificial livers

    1. Caitlin Czajka

    Liver cells grown in a custom bioreactor, as seen in an artist's conception, can provide some support in a model of acute liver failure.

    CREDIT: SHANGHAI CELLIVER BIOTECHNOLOGY CO. LTD.

    Bioartificial livers are an attractive option as a bridge to transplant or to promote liver regeneration in cases of acute liver failure. Li et al. tested an extracorporeal bioartificial liver system composed of human liver progenitor-like cells cultured on macroporous scaffolds in a bioreactor that provides alternating air-liquid exposure. Three hours of treatment improved survival, reducing inflammation and promoting native liver regeneration in pigs with drug-induced acute liver failure. These results suggest that extracorporeal, cell-based bioartificial livers may be a promising treatment for acute liver failure.

    Sci. Transl. Med. 12, eaba5146 (2020).

  5. Immunodeficiencies

    An inherited disorder makes WAVEs

    1. Seth Thomas Scanlon

    The WAVE regulatory complex (WRC) is a multiunit complex that regulates actin cytoskeleton formation. Although other actin-regulatory proteins modulate human immune responses, the precise role for the WRC has not yet been established. Cook et al. studied five patients from four unrelated families who harbor missense variants of the gene encoding the WRC component HEM1. These patients presented with recurrent infections and poor antibody responses, along with enhanced allergic and autoimmune disorders. HEM1 was found to be required for the regulation of cortical actin and granule release in T cells and also interacted with a key metabolic signaling complex contributing to the disease phenotype. By linking these interactions to immune function, this work suggests potential targets for future immunotherapies.

    Science, this issue p. 202

  6. Quantum Physics

    Strongly coupled at distance

    1. Ian S. Osborne

    The development of hybrid quantum systems provides a flexibility that allows for various components to be coupled together, thereby expanding the opportunity to build quantum sensors and devices that can be designed for specific purposes. Key to doing so is being able to strongly couple the different components. Most developments to date have relied on the components being in close proximity, which can hamper design flexibility. Karg et al. used a laser to induce strong coupling between a cloud of atoms and an optomechanical membrane. With the components separated by 1 meter, this approach demonstrates a methodology of coupling quantum systems and easing up restrictions on spatial proximity.

    Science, this issue p. 174

  7. Arctic Productivity

    Food for thought

    1. H. Jesse Smith

    Phytoplankton abundances in the Arctic Ocean have been increasing over recent decades as the region has warmed and sea ice has disappeared. The presumptive causes of this increase were expanding open water area and a longer growing season—at least until now. Lewis et al. show that although these factors may have driven the productivity trends before, over the past decade, phytoplankton primary production rose by more than half because of increased phytoplankton concentrations (see the Perspective by Babin). This finding means that there has been an influx of new nutrients into the region, suggesting that the Arctic Ocean could become more productive and export additional carbon in the future.

    Science, this issue p. 198; see also p. 137

  8. Aging

    Plasma transfers exercise benefit in mice

    1. L. Bryan Ray

    Exercise has a broad range of beneficial healthful effects. Horowitz et al. tested whether the beneficial effects of exercise on neurogenesis in the brain and improved cognition in aged mice could be transferred in plasma (blood without its cellular components) from one mouse to another (see the Perspective by Ansere and Freeman). Indeed, aged mice that received plasma from young or old mice that had exercised showed beneficial effects in their brains without hitting the treadmill. The authors identified glycosylphosphatidylinositol-specific phospholipase D1 as a factor in plasma that might, in part, mediate this favorable effect.

    Science, this issue p. 167; see also p. 144

  9. Lymphatic Biology

    Roles of organ-specific lymphatic vessels

    1. Priscilla N. Kelly

    Lymphatic vessels are spread throughout the human body and have critical functions in mammalian physiology. Petrova et al. review emerging roles of the lymphatic vasculature in organ function and pathology and provide perspectives beyond the traditional view of lymphatic vessels in the maintenance of fluid homeostasis. The authors highlight new insights into lymphatic vessel function and lymphatic endothelial cell biology as it relates to intestinal lacteals, lymph nodes, central nervous system meninges, and cancer. Recent steps toward therapeutic opportunities that could alter lymphatic function or growth are also discussed.

    Science, this issue p. eaax4063

  10. Coronavirus

    Monitoring wildlife disease

    1. Gemma Alderton

    The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has highlighted the danger to humans of disease spillover from wild animals. In a Perspective, Watsa et al. discuss current surveillance of wildlife pathogens and how a decentralized system could be implemented. Such an approach could provide comprehensive surveillance of diseases in wildlife, in farmed animals, and at wildlife markets to ensure that a system is in place for early warning and to be able to identify the sources of disease spillover.

    Science, this issue p. 145

  11. Developmental Biology

    Cell-cell contacts specify cell fate

    1. Beverly A. Purnell

    Ascidians, or sea squirts, are marine invertebrate filter feeders with highly reproducible cellular events and invariant embryonic cell lineages. Guignard et al. studied the ascidian embryo to address the determinants of this cellular reproducibility. They introduce computational methods for the robust and automated segmentation, tracking, and analysis of whole-cell behaviors in high-throughput light-sheet microscopy datasets. This work shows that cell induction can be controlled by the contact area among cells. The range of cell signaling is proposed to set the scale at which animal embryonic reproducibility is observed. A high level of reproducibility of embryonic geometries may also counter-intuitively lift constraints on genome evolution, thereby contributing to the rapid molecular evolution observed in ascidians.

    Science, this issue p. eaar5663

  12. Organoids

    Brain barrier and support in a dish

    1. Beverly A. Purnell

    Deep within the brain, the choroid plexus filters blood and secretes cerebrospinal fluid (CSF), a nutrient-rich liquid that bathes and supports the brain and protects it from entry of toxic compounds. Current understanding of this vital tissue in humans is limited. Pellegrini et al. developed choroid plexus organoids that quantitatively predict human brain permeability of small molecules and secrete an isolated CSF-like fluid (see the Perspective by Silva-Vargas and Doetsch). This CSF model reveals secretion of developmental factors and disease-related biomarkers by key cell types and provides a testing ground for drug entry into the brain.

    Science, this issue p. eaaz5626; see also p. 143

  13. Coronavirus

    Keeping the lid on infection spread

    1. Caroline Ash

    From February to April 2020, many countries introduced variations on social distancing measures to slow the ravages of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Publicly available data show that Germany has been particularly successful in minimizing death rates. Dehning et al. quantified three governmental interventions introduced to control the outbreak. The authors predicted that the third governmental intervention—a strict contact ban since 22 March—switched incidence from growth to decay. They emphasize that relaxation of controls must be done carefully, not only because there is a 2-week lag between a measure being enacted and the effect on case reports but also because the three measures used in Germany only just kept virus spread below the growth threshold.

    Science, this issue p. eabb9789

  14. Fuel Cells

    A metallic route for protons

    1. Phil Szuromi

    The operating temperatures of solid oxide fuel cells are usually much higher than needed to drive the uncatalyzed electrochemical reaction to transport oxygen anions or protons through ceramic electrolytes. Wu et al. report that the interface between two semiconductors, NaxCoO2 and CeO2, forms a metallic state that enables proton transport at temperatures below 600°C (see the Perspective by Ni and Shao). The authors constructed a hydrogen fuel cell with this material that delivered 1 watt per centimeter.

    Science, this issue p. 184; see also p. 138

  15. Cognitive Maps

    Knowing their way around

    1. Sacha Vignieri

    The presence of a cognitive map is essential to our ability to navigate through areas we know because it facilitates the use of spatial knowledge to derive new routes. Whether such maps exist in nonhuman animals has been debated, largely because of the difficulty of demonstrating qualifying components of the map outside of a laboratory. In two studies on Egyptian fruit bats, Harten et al. and Toledo et al. together show that this species's navigational strategies meet the requirements for the use of a cognitive map of their environment, confirming that this skill occurs outside of humans (see the Perspective by Fenton).

    Science, this issue p. 194, p. 188; see also p. 142

  16. Coronavirus

    COVID-19 pandemic in France

    1. Caroline Ash

    Coronavirus disease 2019 (COVID-19) exacted a heavy toll in France during March and April 2020. Quarantine measures were effective in reducing transmission by 84%, and some relaxation of social isolation was expected in May. Salje et al. fit transmission models for the epidemic in France to hospital admissions. The authors forecast that 2.9 million people will have been infected by 11 May, representing 4.4% of the population—a value inadequate for herd immunity. Daily critical care hospitalizations should reduce from several hundreds to tens of cases, but control will remain a delicate balancing act. Any relaxation of lockdown in France will have to be carefully controlled and monitored to avoid undermining more optimistic forecasts.

    Science, this issue p. 208

  17. Topological Matter

    A very high Chern number

    1. Jelena Stajic

    Topologically nontrivial electronic structure can often be characterized by the Chern number, the value of which is related to the magnitude of some of the exotic effects predicted to occur in such systems. Many topological phases discovered so far have a Chern number of 1 or 2, but higher values are also theoretically possible. Schröter et al. predicted that the chiral material palladium gallium (PdGa) would have a Chern number of 4, and they confirmed that prediction using photoemission experiments. Interestingly, the sign of the Chern number was opposite for the two enantiomers of PdGa.

    Science, this issue p. 179

  18. T Cells

    The TOX profiles of T cells

    1. Anand Balasubramani

    Transcription factors TOX and TCF-1 have emerged as key drivers of exhaustion and stemness programs in CD8+ T cells. Using bulk and single-cell transcriptome analyses and flow cytometric analyses, Sekine et al. generated a detailed map of TOX and TCF-1 expression in human CD8+ T cells. TOX is generally expressed by effector memory CD8+ T cells and is not restricted to exhausted T cells, whereas TCF-1 demarcates early-differentiated, memory CD8+ T cells. Using tetramers to examine the specificity of antigen-specific CD8+ T cells, the authors found that cytotoxic memory CD8+ T cells targeting both pathogenic and well-controlled chronic infections are more likely to express TOX. These results support a model in which TOX-dependent transcriptional wiring is not restricted to exhausted CD8+ T cells.

    Sci. Immunol. 5, eaba7918 (2020).

  19. Engineering

    Self-powered electronic skin

    1. Qing Cao

    New technologies are transforming the way humans and machines interact. Zhao et al. developed a self-powered artificial skin capable of simultaneously converting touch stimuli into electrical signals and visible light in real time. The electrical signals can be used to drive an interactive touch operation platform for easy and intuitive control of consumer electronic devices. Electroluminescent signals provide instant visual feedback to the pressure input. The device uses the triboelectric effect to generate the electrical current, and part of the generated current produces light by exciting embedded luminescence centers. Such surface coverings can operate without an external power supply, which is important for portable or wearable electronics.

    Sci. Adv. 10.1126/sciadv.aba4294 (2020).

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