This Week in Science

Science  03 Jun 2016:
Vol. 352, Issue 6290, pp. 1185
  1. Nonhuman Genetics

    A dogged investigation of domestication

    1. Laura M. Zahn
    PHOTO: MAGUID ET AL.; JUNIORS BILDARCHIV GMBH/ALAMY STOCK PHOTO

    The history of how wolves became our pampered pooches of today has remained controversial. Frantz et al. describe high-coverage sequencing of the genome of an Irish dog from the Bronze Age as well as ancient dog mitochondrial DNA sequences. Comparing ancient dogs to a modern worldwide panel of dogs shows an old, deep split between East Asian and Western Eurasian dogs. Thus, dogs were domesticated from two separate wolf populations on either side of the Old World.

    Science, this issue p. 1228

  2. Ecotoxicology

    Microplastic's triple threat

    1. Sacha Vignieri

    The billions of tons of plastics that we release into the environment for the most part do not biodegrade. But they do degrade, breaking into ever smaller particles that end up in the oceans. Lönnstedt et al. show that the impacts of these microplastics are multifold (see the Perspective by Rochman). Eurasian perch larvae exposed to microplastics were less active, less responsive to predator cues, more likely to be eaten, and less likely to thrive—preferring to eat plastic rather than their natural prey.

    Perch larvae will consume microplastics.

    PHOTO: OONA LÖNNSTEDT

    Science, this issue p. 1213; see also p. 1172

  3. Medical Genetics

    At risk by association

    1. Megan Frisk

    Soon genetics may routinely tell clinicians whether certain drugs put patients at risk of developing heart disease or cancer. Scott et al. inspected six genes that encode targets of various drugs for type 2 diabetes or obesity to identify genetic variations linked to metabolic traits such as fasting glucose levels. Using two cohorts totaling more than 50,000 individuals, the authors landed on a variant in GLPR1—which encodes glucagon-like peptide-1 receptor, a target for certain drugs frequently used in the clinic—and compared it against disease outcomes. In more than 200,000 patients (some with heart disease, some controls) the GLPR1 variant proved protective against coronary artery disease and was not associated with cancers or neurological diseases.

    Sci. Transl. Med. 8, 341ra76 (2016).

  4. Cell Reprogramming

    Making cardiac cells from fibroblasts

    1. Beverly A. Purnell

    Reprogramming noncardiac cells into functional cardiomyocytes without any genetic manipulation could open up new avenues for cardiac regenerative therapies. Cao et al. identified a combination of nine small molecules that could epigenetically activate human fibroblasts, efficiently reprogramming them into chemically induced cardiomyocytes (ciCMs). The ciCMs contracted uniformly and resembled human cardiomyocytes. This method may be adapted for reprogramming multiple cell types and have important implications in regenerative medicine.

    Science, this issue p. 1216

  5. Gas Giant Planets

    A radio view into Jupiter's atmosphere

    1. Keith T. Smith

    Jupiter's atmosphere is a complex system of belts, layers, storms, and cloud systems. de Pater et al. used Earth-bound radio observations to peer beneath its surface. Previous radio studies have been limited to average properties at each latitude, but the new observations allow a full two-dimensional view. This can be related to features (such as storms) seen in visible or infrared images. The results aid our understanding of gas giant atmospheres and will provide important context for the Juno spacecraft that arrives at Jupiter in July 2016.

    Science, this issue p. 1198

  6. Bioenergy

    Artificial photosynthesis steps up

    1. Nicholas S. Wigginton

    Photosynthesis fixes CO2 from the air by using sunlight. Industrial mimics of photosynthesis seek to convert CO2 directly into biomass, fuels, or other useful products. Improving on a previous artificial photosynthesis design, Liu et al. combined the hydrogen-oxidizing bacterium Raistonia eutropha with a cobalt-phosphorus water-splitting catalyst. This biocompatible self-healing electrode circumvented the toxicity challenges of previous designs and allowed it to operate aerobically. When combined with solar photovoltaic cells, solar-to-chemical conversion rates should become nearly an order of magnitude more efficient than natural photosynthesis.

    Science, this issue p. 1210

  7. Cancer Metabolism

    Basic principles of cancer metabolism

    1. Ali Shilatifard

    Metabolic activities are altered in cancer cells as compared with normal cells, and these alterations support the acquisition and maintenance of the malignant state. Cancer metabolism is one of the oldest areas of research in cancer biology, predating the discovery of oncogenes and tumor suppressors by some 50 years. Cancer metabolism research is currently undergoing a renaissance. Deberardinis and Chandel review the fundamental principles of cancer metabolism, focusing on recent discoveries that have opened the door for targeted therapeutics.

    Sci. Adv. 2, 10.1126.sciadv.00200 (2016).

  8. Biochemistry

    A nuclear power source in the cell

    1. Guy Riddihough

    DNA is packaged onto nucleosomes, the principal component of chromatin. This chromatin must be remodeled to allow gene transcription, DNA replication, and DNA repair machineries access to the enclosed DNA. Chromatin-remodeling complexes require high levels of cellular energy to do their job. Wright et al. show that the energy needed to remodel chromatin can be derived from a source, poly-ADP-ribose, in the cell nucleus, rather than by diffusion of ATP from mitochondria in the cytoplasm, the usual powerhouse of the cell. Poly-ADP-ribose is converted to ADP-ribose and then to ATP, which can be used to fuel chromatin remodeling within the nucleus.

    Science, this issue p. 1221

  9. Magnetism

    Orbitals and charge go their separate ways

    1. Jelena Stajic

    In certain materials at very low temperatures, an electron's spin can separate from its charge, zooming through the crystal in the form of a “spinon.” Such materials are usually one-dimensional, and their atoms have spins of 1/2. Wu et al. observed related behavior in a three-dimensional metal, Yb2Pt2Pb, where the Yb ions have a large magnetic moment that has its origin in the electrons' orbital motion rather than their spin. Neutron-scattering measurements indicated that these large magnetic moments can flip their direction through an exchange process similar to the one that occurs in spin 1/2 systems. This process results in effective charge-orbital separation.

    Science, this issue p. 1206

  10. Epigenetics

    A balancing act in modifying chromatin

    1. Beverly A. Purnell

    Chromatin modifiers add chemical groups to histones, the proteins that package DNA. These modifications are central to cellular development, and mutations in their molecular machinery are linked to a variety of human diseases. Piunti and Shilatifard review the balance between the prototypic chromatin modifiers Polycomb and COMPASS complexes and their role in gene regulation and normal development. Although originally identified as indispensible regulators of fruit fly development, related roles have been identified in other organisms. Furthermore, mutations in human homologs have been implicated in various cancers. As such, these complexes may serve as effective targets for epigenetic therapies.

    Science, this issue p. 10.1126/science.aad9780

  11. Plasma Astrophysics

    Probing magnetic reconnection in space

    1. Keith T. Smith

    Magnetic reconnection occurs when the magnetic field permeating a conductive plasma rapidly rearranges itself, releasing energy and accelerating particles. Reconnection is important in a wide variety of physical systems, but the details of how it occurs are poorly understood. Burch et al. used NASA's Magnetospheric Multiscale mission to probe the plasma properties within a reconnection event in Earth's magnetosphere (see the Perspective by Coates). They find that the process is driven by the electron-scale dynamics. The results will aid our understanding of magnetized plasmas, including those in fusion reactors, the solar atmosphere, solar wind, and the magnetospheres of Earth and other planets.

    Science, this issue p. 10.1126/science.aaf2939; see also p. 1176

  12. Water Chemistry

    A close-up look at eight water molecules

    1. Jake Yeston

    A raindrop may look small, but it contains far too much water to model with the highest chemical precision. Theorists rely on studies of clusters with just a few molecules to enhance their understanding of the quantum-mechanical forces at play in the liquid. Cole et al. now report a high-resolution spectrum in the terahertz regime of the eight-membered cluster. By resolving 99 absorption lines associated with a collective torsional mode, the authors distinguish prolate and oblate isomers that are very similar in energy.

    Science, this issue p. 1194

  13. RNA Transcription

    TT-Seq maps a transient transcriptome

    1. Laura M. Zahn

    RNA expression is related to protein abundance and cellular function. However, the amounts of RNA generated at any one time-point have been difficult to determine. Schwalb et al. developed a method, transient transcriptome sequencing (TT-Seq), to collect and sequence all RNA segments synthesized over 5 minutes. Because 5 minutes is not long enough to fully degrade even the most transient RNA, this method can detect the synthesis of most RNA without bias. Applying this method to human K562 cells, TT-Seq detected thousands of noncoding transcripts, providing a snapshot of RNA synthesis rates and RNA half-lives, and full-length maps of short-lived RNAs such as enhancers and short intergenic noncoding RNAs.

    Science, this issue p. 1225

  14. Applied Optics

    Multifunction planar optics

    1. Ian S. Osborne

    Specially designed two-dimensional (2D) arrays of nanometer-scale metallic antennas, or metasurfaces, may allow bulky optical components to be shrunk down to a planar device structure. Khorasaninejad et al. show that arrays of nanoscale fins of TiO can function as high-end optical lenses. At just a fraction of the size of optical objectives, such planar devices could turn your phone camera or your contact lens into a compound microscope. Maguid et al. interleaved sparse 2D arrays of metal antennas to get multifunctional behavior from the one planar device structure (see the Perspective by Litchinitser). The enhanced functionality of such designed metasurfaces could be used in sensing applications or to increase the communication capacity of nanophotonic networks.

    Science, this issue pp. 1190 and 1202; see also p. 1177

  15. Innate Immunity

    Immune activation in context

    1. Kristen L. Mueller

    Dendritic cells (DCs) initiate protective immunity upon binding molecules derived from microbes or released from dying cells. Zanoni et al. examined how microbial and endogenous signals interact to shape the course of the ensuing immune response (see the Perspective by Napier and Monack). They found that oxPAPC, an oxidized phospholipid released from dying cells, binds to a protein called caspase-11 in DCs, activating an inflammatory program in these cells. Whereas caspase-11 binding to oxPAPC and bacterial lipopolysaccharide causes DCs to produce the cytokine interleukin-1 (IL-1) and undergo cell death, binding to oxPAPC alone triggers DCs to secrete IL-1 and induce strong adaptive immunity. Thus, context-dependent signals can shape the ensuing immune response.

    Science, this issue p. 1232; see also p. 1173

  16. Origin of Life

    A network view of life's beginnings

    1. Julia Fahrenkamp-Uppenbrink

    What were the chemical reaction networks that enabled the emergence of life on Earth? Many previous studies have investigated the likely chemistry of these networks; for example, postulating an earlier RNA world that paved the way to today's living systems. In a Perspective, Cronin and Walker argue that elucidating the network properties, rather than the detailed chemistry, is key to understanding how life began. Further insight may come from characterizing the emergence of life as a phase transition and asking fundamental questions about what it means for a physical system to be alive. By challenging current models, scientists may not only understand how life as we know it originated but may also be able to detect or create different forms of life.

    Science, this issue p. 1174

  17. Immunology

    Why rapamycin is a good immunosuppressant

    1. John F. Foley

    Recipients of organ transplants receive the immunosuppressant rapamycin to prevent rejection. Rapamycin targets mTORC1, a ubiquitous kinase-containing complex that promotes cell growth and proliferation. So et al. discovered why lymphocytes are particularly sensitive to rapamycin (see the Focus by Abraham). Lymphocytes used one mTORC1 effector to mediate both cell growth and proliferation, unlike other cell types in which these processes are mediated by two different effectors. Phosphorylation of this effector by mTORC1 triggers cell growth and proliferation, and was more sensitive to disruption by rapamycin in lymphocytes.

    Sci. Signal. 9, ra57 and fs10 (2016).