Editors' Choice

Science  06 Sep 2019:
Vol. 365, Issue 6457, pp. 996
  1. Aging

    Microbiota and age-related disease

    1. Priscilla N. Kelly

    The microbiota in the mouse gut becomes disrupted in premature aging disease (progeria).

    PHOTO: DAVID M. PHILLIPS/SCIENCE SOURCE

    Gut bacteria have been shown to influence numerous conditions including cancer, diabetes, and neurological diseases. Bárcena et al. explored how the microbiota affects aging by analyzing the gut microbiota of children with the premature aging disorder called progeria. Patients with accelerated aging displayed greater disturbances in their intestinal bacteria during disease progression when compared with normally aging individuals. Using mouse models of aging, the researchers found that transplantation of fecal microbiota from healthy mice extended the life span of two different models of progeria. This effect correlated with the restoration of levels of secondary bile acids.

    Nat. Med. 25, 1234 (2019).

  2. Neural Stem Cells

    MicroRNA regulation of adult neural stem cells

    1. Pamela J. Hines

    Neuroscientists are keen to tap into the brain's reservoir of neural stem cells to treat age-associated cognitive decline, neurodegeneration, and other illnesses. In the mouse brain, quiescent stem cells in the central subependymal zone are poised to produce new neuroblasts during adulthood. Lepko et al. have linked mobile microRNA signals to regulation of stem cell quiescence. Low amounts of neurogenic fate determinants can be expressed in the stem cells as RNA but are not translated into proteins. Analysis of posttranscriptional regulation fingered the microRNA miR-204, which is abundant in the brain, as the block on the stem cells. The source of miR-204 was the choroid plexus, which delivered miR-204 into the cerebrospinal fluid and, from there, to the neural stem cells. Thus, at the blood–brain interface, the choroid plexus is ready to integrate external, systemic signals with demands for adult brain neurogenesis.

    EMBO J. 10.15252/embj.2018100481 (2019).

  3. Metabolic Disease

    An islet cell reaches out

    1. Paula A. Kiberstis

    Blood glucose levels in mammals are controlled by the coordinated activity of several distinct hormone-secreting cells within pancreatic islets. These include beta cells, which release insulin; alpha cells, which release glucagon; and delta cells, which release somatostatin. Delta cells are integral because their release of somatostatin suppresses hormone secretion by the other cell types. At the islet level, how delta cells accomplish this has been unclear, as they are relatively rare. In a study of mice, Arrojo e Drigo et al. find the answer lies in the characteristic cytoplasmic projections of the delta cells called filipodia. These projections contain secretory machinery, and their dynamic nature allows delta cells to contact distant beta and alpha cells and control their activity.

    Nat. Commun. 10, 3700 (2019).

  4. Molecular Separation

    Engineering alkene affinity

    1. Phil Szuromi

    Metal-organic frameworks (MOFs) that have open sites on metals have potential applications for separating alkanes and alkenes through preferential adsorption. On the basis of density functional theory calculations, Mohamed et al. substituted Zn2+ with Cu+ to modify the MOF MFU-4l, in which Zn5Cl4(ta)6 nodes (where ta is triazolate) bridge long fused aromatic ring linkers. These open sites had greater alkene binding affinity and had minimal interactions with each other, so the binding energy was maintained even as more Cu+ sites were introduced. These materials maintained very high separation ratios for ethylene from ethane and propylene from propane separations in which the alkenes were retained from mixtures at room temperature and then released through thermal cycling.

    J. Am. Chem. Soc. 141, 13003 (2019).

  5. Neuroscience

    Single neurons activate cortical networks

    1. Peter Stern

    All living reptiles and mammals have a brain cortex derived from a common primordial cortex. Thus, they may retain traces of this common ancestry in their structure, connectivity, and function. Hemberger et al. simultaneously sampled action potentials from hundreds of neurons in intact turtle cortical explants and found that minimal manipulation of single cortical pyramidal cells had detectable effects on other neurons and on the animal's behavior. With only one to three spikes, single pyramidal neurons could trigger distributed patterns of firing that cascaded across neurons, space, and time in the form of reliable firing sequences. These sequences are similar to those produced during replay events in the mammalian hippocampus. These data provide evidence for chained synaptic activation in a cortical structure supporting the synfire chain hypothesis.

    Neuron 10.1016/j.neuron.2019.07.017 (2019).

  6. Galaxies

    A large faint companion to the Milky Way

    1. Keith T. Smith

    The dwarf galaxy Antlia 2 (bottom left; added artificially to the photo to make its location visible) is large but very faint.

    PHOTO: G. TORREALBA (ACADEMIA SINICA, TAIWAN), V. BELOKUROV (CAMBRIDGE, UK AND CCA, NEW YORK, US) BASED ON THE IMAGE BY ESO/S. BRUNIER

    The Milky Way is orbited by numerous low-mass dwarf galaxies, which are mostly small and faint. Torrealba et al. have discovered a nearby dwarf galaxy, Antlia 2, which is faint but very large. Combining astrometric, photometric, and spectroscopic data, they determine the distance, mass, and brightness of the galaxy. Because its starlight is spread over a large region, Antlia 2 has the faintest surface brightness of any known galaxy, more than 100 times lower than previously discovered ultra-diffuse galaxies. Its peculiar properties may result from tidal interactions with the Milky Way, implying that Antlia 2 was once even larger.

    Mon. Not. R. Astron. Soc. 488, 2743 (2019).

  7. Electrochemistry

    Smooth path through a molecular catalyst

    1. Jake Yeston

    Molecular electrocatalysts accelerate reactions by shuttling electrons between the electrodes and reactants. This process typically is constrained by the energetics of electron transfer between the electrode and the catalyst. However, Jackson et al. now show that, when linked carefully to the electrode, the catalyst can act as an electron conduit without being reduced ahead of time. They specifically conjugated a rhodium hydrogen-evolution catalyst to a graphite electrode through a pyrazine linker. The ensuing reaction proceeded through concerted proton-coupled electron transfer.

    J. Am. Chem. Soc. 10.1021/jacs.9b04981 (2019).