Editors' Choice

Science  12 May 2017:
Vol. 356, Issue 6338, pp. 595
  1. Physiology

    Macrophages feel the heart beat

    1. L. Bryan Ray

    Immune cells in the heart influence contractility.

    PHOTO: ZEPHYR/SCIENCE SOURCE

    Macrophages, best known for their phagocytic function in the immune system, also have multiple tissue-specific functions, not least in the heart. Hulsmans et al. explored the role of macrophages that are abundant in the atrioventricular (AV) node of the mouse. These macrophages express the connexin 43 (CX43) protein that forms gap junctions between cells, which allow electrical coupling of cells. Macrophages forming such connections alter the electrophysiological function of cardiomyocytes. Deletion of the CX43 protein from macrophages delays conduction by the AV node, and ablation of macrophages blocks conductance of atrial impulses to the ventricles. Macrophages thus influence normal heart contraction, but, because of their alternative function as immune effectors, they might also contribute to heart abnormalities associated with inflammatory diseases.

    Cell 10.1016/j.cell.2017.03.050 (2017).

  2. Arthritis

    Targeting senescence to combat osteoarthritis

    1. Priscilla N. Kelly

    During senescence, cells remain in a state of growth arrest. Accumulation of similar nonfunctional cells has been linked to chronic inflammatory diseases and degenerative disorders. Inflammation after joint injury is a common sequela. Jeon et al. sought to understand whether senescence was involved in the development of osteoarthritis by using a model of anterior cruciate ligament surgery. Senescent cells assembled in the traumatized knee joint and triggered development of osteoarthritis and cartilage erosion in mice. By injecting a drug that caused the specific removal of these cells, the arthritis symptoms were alleviated, and cartilage regeneration and recovery were improved.

    Nat. Med. 10.1038/nm.4324 (2017).

  3. Crop Science

    Crop resistance to parasites

    1. Catherine Griffin

    Witchweed (Striga) is a parasitic plant that devastates arable crops in the tropics.

    PHOTO: GEBISA EJETA

    The parasitic weed Striga infests a large proportion of cereal crops in Africa and parts of Asia, which has a devastating effect on farming, particularly in subsistence communities. An obligate parasite, Striga requires a chemical signal from the host plant to germinate, offering an avenue for genetic improvement of host crops. Gobena et al. studied the difference between sorghum strains associated with high and low Striga germination levels and mapped a mutation associated with low Striga germination (LGS1) to a previously uncharacterized sulfotransferase gene. Deletion of this gene does not result in reduced levels of root chemical signaling, but rather in a change in the composition of chemicals exuded from the root. Identification of this gene could allow marker-assisted breeding to generate sorghum varieties with reduced Striga infestation.

    Proc. Natl. Acad. Sci. U.S.A. 114, 4471 (2017).

  4. Physics

    An elusive magnet in an atomic cloud

    1. Jelena Stajic

    Whether repulsive interactions alone can cause a system of electrons to become ferromagnetic is an open problem in condensed matter physics. One way to tackle it is to use cold fermionic atoms of opposite spins instead of electrons and generate interactions by tuning an external magnetic field. However, such atoms are much more likely to form a superfluid than a ferromagnet. To avoid the superfluid pairing, Valtolina et al. started with an atomic system divided neatly into two clouds of opposite spin, with a barrier separating them. After removing the barrier, they monitored the dynamics of the cloud motion and the spin diffusion. For some interaction strengths, the dynamics were consistent with those of a metastable ferromagnetic state.

    Nat. Phys. 10.1038/NPHYS4108 (2017).

  5. Organic Chemistry

    Quantum dots visibly forge carbon bonds

    1. Jake Yeston

    Chemists are late to the game that plants play of using visible light to make carbon-carbon bonds. Nonetheless, they have made up for lost time over the past decade, applying light activation of precious iridium and ruthenium catalysts to a wide variety of molecular transformations. Zhang et al. and Caputo et al. now report that nanoparticulate quantum dots (cadmium sulfide and cadmium selenide, respectively) can also catalyze several of these photoredox reactions. Composed of more abundant elements, these quantum dots further benefit from high light-absorption cross sections and straightforward tunability through variation of diameter and surface ligand structure.

    J. Am. Chem. Soc. 139, 4246, 4250 (2017).

  6. Outer Solar System

    A probable dwarf planet beyond Neptune

    1. Keith T. Smith

    The cold outer reaches of our solar system host an array of orbiting bodies and may even hide a distant planet. Gerdes et al. have searched for new bodies in that region by using an optical survey that is primarily used for cosmology. They discovered an object, designated 2014 UZ224, located 92 times as far from the Sun as Earth—making it the second-most distant body whose orbit is known. Follow-up millimeter-wavelength observations allowed them to measure the thermal emission and thereby estimate the body's size and temperature. With a diameter of around 600 km, it is probably a dwarf planet.

    Astrophys. J. 839, L15 (2017).

  7. Transcription

    Selection acts on the neighbors

    1. Laura M. Zahn

    To make a protein, three base pairs of DNA are copied into an RNA transcript that is then translated by a ribosome into amino acids. However, three-base-pair codons are commonly redundant in their translation into amino acids. Chevance and Hughes show that even when the amino acids do not change, the sequences of the codons proximal to a specific DNA sequence may affect the number and rate of transcripts formed, and hence gene expression, in the bacterium Salmonella. Modeling shows how the composition of successive codons can influence translational efficiency profoundly in some cases or not at all in others, depending on the species.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1614896114 (2017).