Editors' Choice

Science  22 May 2020:
Vol. 368, Issue 6493, pp. 841
  1. Glaciers

    Continuity in a gap year

    1. H. Jesse Smith

    Illustration of one of the twin Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) satellites

    ILLUSTRATION: NASA/JPL-CALTECH

    The Gravitational Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) satellite missions have provided measurements of how much mass has been lost from the glaciers of the world since GRACE began operation in 2002. However, GRACE ended in 2017 and GRACE-FO was not launched until 2018, creating a data gap of 1.5 years. Is there an offset of their records? Ciracì et al. report that there is not. Using an independent dataset, they show that there is continuity in the satellite mass balance record. This is important because these glaciers, even though they contain far less mass than the Greenland or Antarctic ice sheets, were the biggest contributor to sea-level rise over the 20th century.

    Geophys. Res. Lett. 47, e2019GL086926 (2020).

  2. Immunogenetics

    HLA genetics and COVID-19

    1. Laura M. Zahn

    Human leukocyte antigens (HLAs) are proteins encoded by a diverse set of human genes in the major histocompatibility complex. Most people carry between three and six different HLA alleles that show geographically specific distributions. These proteins are important for how the immune system recognizes and mounts immune defenses against infection. Nguyen et al. examined how HLA variation affects the cellular immune response to peptides from human-infecting coronaviruses. The authors found that HLA-B*46:01 had the fewest predicted binding sites to the severe acute respiratory syndrome–coronavirus 2 (SARS-CoV-2) virus, and HLA-B*15:03 showed the greatest capacity to present highly conserved shared SARS-CoV-2 peptides to immune cells. HLA typing may therefore offer valuable information on how coronavirus disease 2019 (COVID-19) might manifest in an individual and help to prioritize treatment options.

    J. Virol. 10.1128/JVI.00510-20 (2020).

  3. Soil Microbiome

    Rehydrating peatland microbiomes

    1. Pamela J. Hines

    After short periods of drought, rehydration of peat bogs allows recovery of their microbial communities.

    PHOTO: MARTYN WILLIAMS/ALAMY STOCK PHOTO

    Peatlands are good at storing carbon but are destabilized when they dry out. This happens because oxygen penetrates the dry peat to promote aerobic degradation, releasing carbon and nutrients. Destruction of the mossy overlay follows, which in an intact functioning bog supplies a continuous accumulation of organic matter. Rewetting might restore dried-out peatlands, but whether functioning bog communities that draw down carbon are restored depends on whether microbial communities are restored. Emsens et al. surveyed the microbial communities of undrained, dry, and rewetted peatlands. Microbial communities differed between undrained and dry peatland. Rewetted peatlands showed recovery of microbial communities, although loss of organic matter during extended dry times seemed to limit microbiome recovery.

    ISME J. 10.1038/s41396-020-0639-x (2020).

  4. Cancer Immunology

    Vaccine potential of dendritic cells

    1. Priscilla N. Kelly

    The ability of dendritic cells (DCs) to process and present antigens to the immune system makes them intriguing candidates for the development of cancer immunotherapies. Zhou et al. investigated whether the CD103+ tissue-resident conventional DC1 (cDC1) subset could control tumors in mouse models. DCs were grown and activated in cell culture using an immunostimulant called polyinosinic:polycytidylic acid (poly I:C). The cells were then loaded with tumor antigens and injected into mice to assess their vaccine potential. The authors found that in vitro–generated CD103+ cDC1s restrained melanoma and osteosarcoma tumor growth. Tumors could be further hindered if the in vitro–generated cDC1s were combined with immune checkpoint blockade treatment.

    J. Immunother. Cancer 8, e000474 (2020).

  5. High Pressure

    Diffuse density determination

    1. Brent Grocholski

    Liquid iron at extreme pressure and temperature powers Earth's magnetic field, but its properties are not well constrained. Kuwayama et al. used diffuse x-ray scattering to determine the density of molten iron at conditions near those of Earth's outer core. The authors developed a new data analysis method to obtain these values, which can be combined with shock-wave observations to determine the thermal equation of liquid state for iron. The results help to constrain the amounts of alloying elements in Earth's core and provide a new strategy for measuring liquid density at high pressures.

    Phys. Rev. Lett. 124, 165701 (2020).

  6. Optomechanics

    The coolest of vibrations

    1. Ian S. Osborne

    Shifts in the resonance frequency of micrometer-sized mechanical resonators provide a platform for high-resolution sensing and detection applications. To exploit optomechanical resonators for quantum technologies, the temperature of the system needs to be very low, ideally well below an occupancy of just one phonon, so that the system is in its ground state. From there, selection and control of the transitions between quantized energy levels provide for quantum-enhanced precision measurement. Qiu et al. demonstrate laser cooling of a crystalline silicon optomechanical resonator to its zero-point energy. With a mean thermal phonon occupancy of just ∼0.09 quantum, corresponding to ∼92% ground state probability and −7.4 decibels of the zero-point energy, the stage is now set for exquisite quantum-sensing applications as well as fundamental tests of quantum mechanics.

    Phys. Rev. Lett. 124, 173601 (2020).

  7. Developmental Biology

    Atlas of gastrulation

    1. Beverly A. Purnell

    We marvel at the progression of a single cell into a complex organism, and microscopy has long been used to visualize early developmental events. More recently, molecular networks and cellular lineages have been constructed by measuring cells' gene expression profile through single-cell RNA sequencing (scRNA-seq). Sladitschek et al. combined scRNA-seq and light-sheet imaging of the ascidian Phallusia mammillata to reveal gene expression in all cells of the embryo up to the formation of the multilayered gastrula. Every cell was followed for all cell divisions in 18 cell lineages. The result is a map of cell spatial position and lineage history that reveals embryonic bilateral symmetry and interembryonic variability, as well as the patterned expression of cell adhesion molecules. This resource can be used to examine any number of molecular mechanisms and developmental events occurring in the gastrulating embryo and can serve as model for the spatiotemporal map.

    Cell 10.1016/j.cell.2020.03.055 (2020).

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