Editors' Choice

Science  24 May 2019:
Vol. 364, Issue 6442, pp. 747
  1. Neuroscience

    Artificial memories

    1. Claudia Pama

    Memories can be artificially implanted by stimulating circuits within the amygdala of the brain.

    ILLUSTRATION: THIERRY BERROD, MONA LISA PRODUCTION/SCIENCE SOURCE

    Activity patterns in distinct neural circuits eventually form coded memories during learning. In theory, replicating the same neural activity could recreate these memories without requiring the real-life learning experience. Vetere et al. show how artificial memories can be created by stimulating brain regions. In optogenetics, light can be used to silence or activate proteins labeled with light-sensitive rhodopsins. With this technology, the authors identified the neural pathways that are involved in the formation of “real” memories during an odor conditioning task. Mice will memorize a preference or aversion toward specific odors. In these experiments, animals that were conditioned through experience showed the same responses as animals that had an optogenetically implanted memory. The expression of both real and artificial memories depended on activity in a brain region called the basolateral amygdala.

    Nat. Neurosci. 10.1038/s41593-019-0389-0 (2019).

  2. Nanomaterials

    Grafting nanocorrals onto graphite

    1. Phil Szuromi

    Scanning tunneling micrograph of nanocorrals formed by aryl diazonium compounds on a graphite surface

    CREDIT: DE FEYTER GROUP

    The electrochemical reduction of a mixture of two aryl diazonium compounds on graphite can lead to the formation of an array of nanoscale corrals. Phan et al. found that reduction of 4-nitrobenzenediazonium or 3,5-bis-tert-butylbenzenediazonium (TBD) alone creates aromatic radicals that graft homogeneously to the graphite surface. However, mixtures of these compounds created a quasi-periodic array of open regions that ranged from 45 to 130 nanometers. Mixtures richer in the more sterically hindered TBD resulted in larger diameters. The authors suggest that open corrals form from nanobubble structures created by N2 released in the reduction process that prevent access of the reactants to the graphite surface.

    ACS Nano 10.1021/acsnano.9b00439 (2019).

  3. Signal Transduction

    Turning on a G protein receptor

    1. L. Bryan Ray

    The mammalian target of rapamycin complex 1 (mTORC1) protein kinase is activated at the lysosomal membrane and helps control autophagy and metabolism. It interacts with other proteins that act as sensors for stimuli like amino acids. Gan et al. used an unbiased screen to discover another protein that functions in this complex, one with similarity to heterotrimeric G protein—coupled receptors (GPCRs). The GPCR-like protein, GPR137B, appears to regulate cycles of association and release of the small guanosine triphosphatase Rag and mTORC1 at the lysosome even in the absence of amino acids. Whether a ligand for the orphan receptor could provide additional regulation adds a further intriguing twist.

    Nat. Cell Biol. 22, 614 (2019).

  4. Neurodegeneration

    Galectin-3 in Alzheimer's disease

    1. Stella M. Hurtley

    The role of the innate immune system and inflammation in Alzheimer's disease is currently undergoing scrutiny. Galectin-3 has been identified as a protein that is highly up-regulated in brain microglia during neurodegeneration and aging. Boza-Serrano et al. analyzed the potential role of galectin-3 in Alzheimer's disease pathology. They found that galectin-3 was highly up-regulated in brains from Alzheimer's disease patients, particularly in microglia associated with amyloid plaques. A similar distribution was seen in mouse models of Alzheimer's disease. Polymorphisms in the gene encoding galectin-3 were associated with increased risk of Alzheimer's disease. In mouse models, reducing galectin-3 expression ameliorated plaque burden and improved cognitive behaviors. Furthermore, direct injections of galectin-3 and amyloid into wild-type mice induced amyloid aggregation in the hippocampus. Further work will be needed to confirm whether inhibiting galectin-3 could provide an approach to Alzheimer's disease treatment or prevention.

    Acta Neuropathol. 10.1007/s00401-019-02013-z (2019).

  5. Immunology

    Liquid crystal immune sensing

    1. Seth Thomas Scanlon

    Systemic scleroderma (SSc) is an autoimmune disease of the connective tissue thought to be the result of aberrant innate immune signaling. CXCL4, a platelet-derived chemoattractant for neutrophils, monocytes, and fibroblasts, can serve as a biomarker for this disease. Lande et al. report that high CXCL4 levels found in SSc patients correlates with plasmacytoid dendritic cell (pDC) activation and interferon-α production. They show that CXCL4 organizes both “self” and foreign DNA into liquid-crystalline supramolecular complexes in a DNA size–dependent manner. These complexes chaperone nucleic acids into pDCs and allow for optimal clustering and activation of the innate immune sensor Toll-like receptor 9. Beyond SSc pathogenesis, these findings may illuminate the role of platelets in wound healing and tissue repair.

    Nat. Commun. 10, 1731 (2019).

  6. Linguistics

    Climate variability and linguistic diversity

    1. Tage S. Rai

    Different parts of the world vary in the number of languages they contain. Prior research has suggested that climate plays a major role in this variability. When social groups live in areas with high seasonality and unpredictable rainfall, they are more likely to develop a shared language with other communities across larger land areas to mitigate ecological risks. Hua et al. draw on a global dataset of 6425 languages to confirm the climate variability hypothesis against competing hypotheses related to landscape features and biodiversity, while statistically controlling for spatial and phylogenetic factors. These results provide insight into how stable climates support small social group living and how more-variable climates support the formation of larger coalitions.

    Nat. Commun. 10, 2047 (2019).

  7. Catalysis

    Catalytic alkene cross-coupling

    1. Yury Suleymanov

    Hydrogen atom transfer (HAT) from a metal-hydride complex to an alkene, which produces a free radical responsible for subsequent bond formation, is becoming an increasingly useful type of alkene coupling reaction. Using kinetic, spectroscopic, and computational analyses, Kim et al. pinpoint the key organometallic species and proton-coupled electron transfer steps responsible for regulating selectivity and reactivity in this reaction class. They explain several observations that were previously incomprehensible and demonstrate the intimate involvement of metal species throughout the catalytic cycle. The methods for the present mechanistic work may be applicable to various HAT alkene coupling reactions and should be useful for more expedient design of metal catalysts.

    J. Am. Chem. Soc. 141, 7473 (2019).