This Week in Science

Science  06 Jul 2018:
Vol. 361, Issue 6397, pp. 38
  1. Domestication

    How humans got their goats

    1. Laura M. Zahn

    Genomics traces ancient movements of domesticated goats.

    CREDIT: PHILIPUS/ALAMY STOCK PHOTO

    Little is known regarding the location and mode of the early domestication of animals such as goats for husbandry. To investigate the history of the goat, Daly et al. sequenced mitochondrial and nuclear sequences from ancient specimens ranging from hundreds to thousands of years in age. Multiple wild populations contributed to the origin of modern goats during the Neolithic. Over time, one mitochondrial type spread and became dominant worldwide. However, at the whole-genome level, modern goat populations are a mix of goats from different sources and provide evidence for a multilocus process of domestication in the Near East. Furthermore, the patterns described support the idea of multiple dispersal routes out of the Fertile Crescent region by domesticated animals and their human counterparts.

    Science, this issue p. 85

  2. Organic Chemistry

    Cyclobutanes sourced right from ethylene

    1. Jake Yeston

    Ethylene is one of the highest-volume commodity chemicals manufactured from fossil fuels. It is mainly used to make plastic, although its ready availability incentivizes its expanded use in pharmaceutical synthesis. Pagar and RajanBabu now report that a cobalt catalyst can couple ethylene with enynes (another comparatively inexpensive feedstock bearing carbon-carbon double and triple bonds) to make complex chiral molecules. Initially, the ethylene reacts with the enyne's triple bond to form an isolable cyclobutene compound. At longer reaction times, the same catalyst can add a second equivalent of ethylene enantioselectively to form cyclobutanes with a quaternary chiral carbon center.

    Science, this issue p. 68

  3. Quantum Information

    In search of the right diamond defect

    1. Jelena Stajic

    Certain defects in diamond are among the most promising physical implementations of qubits, the building blocks of quantum computers. However, identifying a defect with balanced properties is tricky: Nitrogen vacancy centers have a long lifetime but comparatively poor optical properties, whereas negatively charged silicon vacancy centers have the opposite characteristics. Rose et al. used careful materials engineering to stabilize the neutral charge state of silicon vacancy centers and found that they combine long coherence times with excellent optical properties.

    Science, this issue p. 60

  4. Neuroscience

    Neurons that regulate feeding

    1. Peter Stern

    The tuberal nucleus, an area of the hypothalamus, has not been studied in great detail. Luo et al. found that GABAergic somatostatin neurons in the tuberal nucleus are functionally involved in the regulation of feeding in mice (GABA, γ-aminobutyric acid) (see the Perspective by Diano). These neurons were activated by food deprivation or hunger hormone. Loss- and gain-of-function experiments indicated that these cells are necessary and sufficient to control systemic metabolic balance. This newly described regulatory center is extensively connected with other feeding control circuits via projections to other hypothalamic nuclei.

    Science, this issue p. 76; see also p. 29

  5. Oceanography

    Pinpointing no-mining areas in the deep sea

    1. Philippa J. Benson

    Areas near mid-ocean ridges are being approved for mining, and protecting these diverse seafloor ecosystems is critical The International Seabed Authority is responsible for regulating deep-sea mining in the high seas. This agency has developed environmental management plans to protect local diversity by identifying areas where mining should be prohibited. Dunn et al. developed an ecological framework to identify criteria for establishing such mining-free regions on mid-ocean ridges. The areas should be at least 200 kilometers long to hold regional biodiversity intact. Furthermore, the species within these areas should be distributed properly to maintain population connectivity.

    Sci. Adv. 10.1126/sciadv.aar4313 (2018).

  6. Quantum Optics

    A single-photon gate

    1. Ian S. Osborne

    The makings of a photon transistor

    CREDIT: E. EDWARDS/JOINT QUANTUM INSTITUTE

    A long-standing goal in optics is to produce a solid-state alloptical transistor, in which the transmission of light can be controlled by a single photon that acts as a gate or switch. Sun et al. used a solid-state system comprising a quantum dot embedded in a photonic crystal cavity to show that transmission through the cavity can be controlled with a single photon. The single photon is used to manipulate the occupation of electronic energy levels within the quantum dot, which in turn changes its optical properties. With the gate open, about 28 photons can get through the cavity on average, thus demonstrating single-photon switching and the gain for an optical transistor.

    Science, this issue p. 57

  7. Premature Aging

    Delaying premature aging

    1. Annalisa M. VanHook

    Cells from patients with Hutchinson-Gilford progeria syndrome (HGPS) have defects in nuclear architecture that lead to premature cellular senescence. Larrieu et al. investigated the mechanisms by which a small molecule called remodelin improves the phenotype of HGPS cells (see the Focus by Wilson). Remodelin restored a nuclear import pathway mediated by Transportin-1 that was defective in HGPS cells, thereby delaying premature senescence. These results could also be applied to delay cellular senescence in cells derived from aged healthy individuals.

    Sci. Signal. 11, eaar5401; see also eaat9448 (2018).

  8. Atmospheric Circulation

    A traffic jam of air

    1. H. Jesse Smith

    Persistent meandering of the jet stream can cause atmospheric blocking of prevailing eastward winds and result in weather extremes such as heat waves in the midlatitudes. Nakamura and Huang interpret the poorly understood origins of these systems as the meteorological equivalents of traffic congestion on a highway and show how they can be described by analogous mathematical theory. Climate change may affect the frequency of blocking as well as its geographic distribution, reflecting a simultaneous shift in the structure of the stationary atmospheric waves and the regional capacity of the jet stream.

    Science, this issue p. 42

  9. Structural Biology

    Target degradation of Type I CRISPR

    1. Steve Mao

    The CRISPR adaptive immune systems defend bacteria against invaders. Type I CRISPR-Cas systems, the most prevalent type, use a Cascade complex to search the target DNA that is then degraded by Cas3 protein. Xiao et al. report cryo–electron microscopy structures of the Type I-E Cascade/Cas3 complex in the pre– and post–DNA-nicking states. These structures reveal how Cas3 captures Cascade only in its correct conformation to reduce off-targeting and how Cas3 switches from the initial DNA-nicking mode to the processive DNA degradation mode.

    Science, this issue p. eaat0839

  10. Framework Materials

    Covalent organic frameworks writ large

    1. Phil Szuromi

    Covalent organic framework (COF) materials have been difficult to characterize structurally and to exploit because they tend to form powders or amorphous materials. Ma et al. studied a variety of three-dimensional COFs based on imine linkages (see the Perspective by Navarro). They found that the addition of aniline inhibited nucleation and allowed the growth of crystals large enough for single-crystal x-ray diffraction studies. Evans et al. describe a two-step process in which nanoscale seeds of boronate ester–linked two-dimensional COFs can be grown into micrometer-scale single crystals by using a solvent that suppresses the nucleation of additional nanoparticles. Transient absorption spectroscopy revealed superior charge transport in these crystallites compared with that observed in conventional powders.

    Science, this issue p. 48, p. 52; see also p. 35

  11. Chemical Physics

    Motion picture of a conical intersection

    1. Jake Yeston

    In most chemical reactions, electrons move earlier and faster than nuclei. It is therefore common to model reactions by using potential energy surfaces that depict nuclear motion in a particular electronic state. However, in certain cases, two such surfaces connect in a conical intersection that mingles ultrafast electronic and nuclear rearrangements. Yang et al. used electron diffraction to obtain time-resolved images of CF3I molecules traversing a conical intersection in the course of photolytic cleavage of the C–I bond (see the Perspective by Fielding).

    Science, this issue p. 64; see also p. 30

  12. Ocean Chemistry

    Controlling zinc in the oceans

    1. H. Jesse Smith

    Zinc, a key micronutrient for marine phytoplankton, has a global distribution remarkably similar to that of silicic acid, even though Zn and Si have very different biogeochemical cycles. Weber et al. investigated why this is so by combining model calculations and observations. They found that biological uptake in the Southern Ocean and reversible scavenging of Zn onto sinking particles both affect the distribution of Zn in the ocean. Thus, Zn and Si distributions will be affected differently by future changes in ocean temperature, pH, and carbon fluxes.

    Science, this issue p. 72

  13. Human Genomics

    Ancient migrations in Southeast Asia

    1. Laura M. Zahn

    The past movements and peopling of Southeast Asia have been poorly represented in ancient DNA studies (see the Perspective by Bellwood). Lipson et al. generated sequences from people inhabiting Southeast Asia from about 1700 to 4100 years ago. Screening of more than a hundred individuals from five sites yielded ancient DNA from 18 individuals. Comparisons with present-day populations suggest two waves of mixing between resident populations. The first mix was between local hunter-gatherers and incoming farmers associated with the Neolithic spreading from South China. A second event resulted in an additional pulse of genetic material from China to Southeast Asia associated with a Bronze Age migration. McColl et al. sequenced 26 ancient genomes from Southeast Asia and Japan spanning from the late Neolithic to the Iron Age. They found that present-day populations are the result of mixing among four ancient populations, including multiple waves of genetic material from more northern East Asian populations.

    Science, this issue p. 92, p. 88; see also p. 31

  14. Domestication

    Lineage losses for man's best friend

    1. Laura M. Zahn

    Dogs have been present in North America for at least 9000 years. To better understand how present-day breeds and populations reflect their introduction to the New World, Ní Leathlobhair et al. sequenced the mitochondrial and nuclear genomes of ancient dogs (see the Perspective by Goodman and Karlsson). The earliest New World dogs were not domesticated from North American wolves but likely originated from a Siberian ancestor. Furthermore, these lineages date back to a common ancestor that coincides with the first human migrations across Beringia. This lineage appears to have been mostly replaced by dogs introduced by Europeans, with the primary extant lineage remaining as a canine transmissible venereal tumor.

    Science, this issue p. 81; see also p. 27

  15. HIV

    Learning from naïve B cells

    1. Lindsey Pujanandez

    Despite decades of intensive research, HIV vaccines are unable to generate the broadly neutralizing antibodies that are likely necessary for protection. Havenar-Daughton et al. inspected the potential of human naïve B cells to recognize the vaccine candidate eOD-GT8 and isolated B cells that use similar genes as those used to make the broadly neutralizing antibody VRC01. Interestingly, they also observed B cells with immunoglobulin genes similar to those used in other types of broadly neutralizing antibodies, some with a more conventional maturation path than VRC01. Thus, vaccination of humans with eOD-GT8 has the potential to induce CD4–binding site broadly neutralizing antibodies, which would be a major step forward in HIV vaccines.

    Sci. Transl. Med. 10, eaat0381 (2018).