This Week in Science

Science  29 Jan 2016:
Vol. 351, Issue 6272, pp. 461
  1. Geophysics

    A silent and periodic earthquake trigger

    1. Brent Grocholski

    Damage to container terminal in Sendai Shiogama Port, Japan after a 9. 0 magnitude earthquake in March 2011

    PHOTO: © PACIFIC PRESS SERVICE/ALAMY STOCK PHOTO

    Large earthquakes that hit places such as Japan seem to be preceded by subtle and silent deformation. Uchida et al. show that these “slow-slip events” are quasi-periodic in the megathrust zone in Japan. Slow-slip events occurred every 1 to 6 years and frequently were correlated with large earthquakes, including the great 2011 Tohoku-oki earthquake. The quasi-periodic behavior stretches back to at least 1930 and provides an important constraint for seismic hazard assessment in the region.

    Science, this issue p. 488

  2. History of Science

    Babylonian astronomers tracked Jupiter

    1. Keith T. Smith

    Ancient Babylonian astronomers developed many important concepts that are still in use, including the division of the sky into 360 degrees. They could also predict the positions of the planets using arithmetic. Ossendrijver translated several Babylonian cuneiform tablets from 350 to 50 BCE and found that they contain a sophisticated calculation of the position of Jupiter. The method relies on determining the area of a trapezium under a graph. This technique was previously thought to have been invented at least 1400 years later in 14th-century Oxford. This surprising discovery changes our ideas about how Babylonian astronomers worked and may have influenced Western science.

    Science, this issue p. 482

  3. Superconductivity

    Going to extremes to find superconductivity

    1. Jelena Stajic

    Quantum phase transitions (QPTs) occur at zero temperature when parameters such as magnetic field or pressure are varied. In heavy fermion compounds, superconductivity often accompanies QPTs, a seeming exception being the material YbRh2Si2, which undergoes a magnetic QPT. Schuberth et al. performed magnetic and calorimetric measurements at extremely low temperatures and magnetic fields and found that it does become superconducting after all. Almost simultaneously with superconductivity, another order appeared that showed signatures of nuclear spin origin.

    Science, this issue p. 485

  4. Cystic Fibrosis

    Airway infections put to an acid test

    1. Paula A. Kiberstis

    Most people with cystic fibrosis suffer from chronic respiratory infections. The mechanistic link between this symptom and the genetic cause of the disease (mutations that compromise the function of the cystic fibrosis transmembrane conductance regulator, CFTR) is not fully understood. Studying animal models, Shah et al. find that in the absence of functional CFTR, the surface liquid in the airways becomes acidic, which impairs host defenses against infection. This acidification occurs through the action of a proton pump called ATP12A. Molecules inhibiting ATP12A could potentially be developed into useful drugs.

    Science, this issue p. 503

  5. Immunology

    All T cells can remember

    1. Kristen L. Mueller

    One of the hallmarks of adaptive immunity is that T and B lymphocytes “remember” previous infections, protecting the host from subsequent infections. When T cells respond to a pathogen, they proliferate, and a fraction of their progeny goes on to form long-lived memory cells. It is not clear whether all of the T cell clones that respond to the initial infection have the potential to form memory T cells. Tubo et al. used a single-cell adoptive transfer model in mice to answer this question. Nearly all T cell clones produced memory cells, which suggests that breadth is probably an important component of immunological memory.

    Science, this issue p. 511

  6. Sex Chromosome

    Replacing the Y chromosome

    1. Beverly A. Purnell

    The mammalian Y chromosome encodes a specialized set of genes that are essential for male viability and fertility. In particular, the sex-determining region Y (SRY) protein is necessary to initiate male sex determination. However, Yamauchi et al. show that the functions of the entire Y chromosome can be replaced with only two genes. In mice, two transgenes, Sox9 and Eif2s3x, compensated for the absence of all Y chromosome genes to allow successful sperm formation.

    Science, this issue p. 514

  7. Lunar Formation

    Rehomogenizing the Earth-Moon system

    1. Brent Grocholski

    Apollo 17 sample of lunar highland rock

    PHOTO: PAUL WARREN/UCLA

    A giant impact formed the Moon, and lunar rocks provide insight into that process. Young et al. found that rocks on Earth and the Moon have identical oxygen isotopes. This suggests that well-mixed material from the giant impact must have formed both the Moon and Earth's mantle. The finding also constrains the composition of the “late veneer”: material sprinkled onto Earth after the Moon-forming impact.

    Science, this issue p. 493

  8. Metabolism

    Antisense now makes sense

    1. Megan Frisk

    Mipomersen is a U.S. Food and Drug Administration-approved antisense oligonucleotide that lowers low-density lipoprotein (LDL) in patients with high cholesterol by targeting apolipoprotein B (apoB) synthesis. It is unclear exactly how mipomersen works in humans. Reyes-Soffer et al. found that in healthy volunteers. the drug reduced levels of LDL and its precursor, very low-density lipoprotein (VLDL), by increasing clearance of both of these vessel-clogging agents rather than reducing their secretion by the liver. Direct clearance of VLDL led to reduced production of LDL. Studies in mice and cell lines revealed how the liver compensates for reduced apoB synthesis to potentially avoid fatty liver disease.

    Sci. Transl. Med. 8, 323ra12 (2016).

  9. Developmental Biology

    A MEK threshold in the placenta

    1. Nancy R. Gough

    The kinases MEK1 and MEK2 have the same substrates, but mice lacking Mek1 die as embryos because of placental defects, whereas mice lacking Mek2 are viable. Aoidi et al. found that MEK1 and MEK2 were functionally redundant as long as sufficient protein was produced. Producing the minimum amount of MEK in the developing placenta required at least four copies of Mek2 in mice lacking Mek1 or two copies of Mek1 in mice lacking Mek2. Thus, the products may be functionally identical, but isoform-specific differences enable isoform-specific regulation and phenotypes.

    Sci. Signal. 9, ra9 (2016).

  10. Melanoma Initiation

    Visualizing the beginnings of melanoma

    1. Beverly A. Purnell

    In cancer biology, a tumor begins from a single cell within a group of precancerous cells that share genetic mutations. Kaufman et al. used a zebrafish melanoma model to visualize cancer initiation (see the Perspective by Boumahdi and Blanpain). They used a fluorescent reporter that specifically lit up neural crest progenitors that are only present during embryogenesis or during adult melanoma tumor formation. The appearance of this tumor correlated with a set of gene regulatory elements, called super-enhancers, whose identification and manipulation may prove beneficial in detecting and preventing melanoma initiation.

    Science, this issue p. 10.1126/science.aad2197; see also p. 453

  11. Polymers

    Doubling down on polymerization

    1. Phil Szuromi

    In biology, structural polymers such as cytoskeletal fibers assemble from covalently polymerized monomers through weaker supramolecular interactions such as hydrogen bonds. Yu et al. report the synthesis of cylindrical fibers when three monomers react, two covalently and one in a supramolecular fashion. When the reaction proceeded stepwise, lower-molecular-weight flat tapes formed instead, which suggests that supramolecular interactions helped to catalyze the covalent polymerization.

    Science, this issue p. 497

  12. Stress Response

    How cells keep going in the face of adversity

    1. Stella M. Hurtley

    When cells experience stresses that affect their ability to process newly synthesized proteins, they turn down their rates of translation to help them survive the stress. They also turn on the translation of proteins that will help them cope with the misfolded proteins generated during stress. How do they turn down translation in general, but maintain or increase translation of specific proteins? Starck et al. developed an approach that allowed them to look at the translation of specific messenger RNAs that were not down-regulated by stress. They identified a motif that helped keep chaperone protein synthesis going.

    Science, this issue p. 10.1126/science.aad3867

  13. Structural Biology

    Structure of a key spliceosomal complex

    1. Valda Vinson

    In eukaryotes, when DNA is transcribed into RNA, the primary transcript has protein-coding sequences interrupted by noncoding sequences called introns. Introns are removed by a complex molecular machine, the spliceosome. Wan et al. determined the structure of a key subcomplex, the tri-SNP, that comprises three small nuclear RNAs and more than 30 proteins. The structure, determined by electron microscopy at 3.8 Å resolution, unexpectedly shows a primary RNA transcript bound in the tri-SNP. Further analysis revealed how the spliceosome assembles to achieve its complex functions.

    Science, this issue p. 466

  14. Surface Science

    Nanoclusters just by adding CO

    1. Phil Szuromi

    The most closely packed surfaces of transition metals are usually stable under vacuum, but during catalytic reactions, energetic changes that result from adsorbing molecules could change the surface structure. Eren et al. present an extreme example for carbon monoxide (CO) adsorption on the (111) surface of copper at very low partial pressures. The surface decomposed into small nanoclusters (most containing 3 or 19 atoms). The surface was more reactive than the original and, for example, could dissociate adsorbed water at room temperature.

    Science, this issue p. 475

  15. Oceanography

    Searching sediment for climate signals

    1. Brent Grocholski

    Sediments on the ocean floor may provide clues about the interplay between ice ages and mid-ocean ridge magma production. Lund et al. present well-dated and detailed sediment records from hydrothermal activity along the East Pacific Rise. The sediments show changes in metal fluxes that are tied to the past two glaciations. Ice age changes in sea level alter magma production, which is manifested by changes in hydrothermal systems. The apparent increase in hydrothermal activity at the East Pacific Rise around the past two glacial terminations suggests some role in moderating the size of ice sheets.

    Science, this issue p. 478

  16. Biochemistry

    A special way to make T

    1. Guy Riddihough

    The genomes of all cell-based life consist of DNA. Blocking DNA synthesis is thus lethal, and if targeted selectively, its inhibition can provide cancer and antibiotic treatments. For example, the drug methotrexate interferes with the synthesis of thymidine, the base T in DNA. Mishanina et al. found that the enzyme that carries out the last step of thymidine synthesis in several human pathogens, which cause tuberculosis, anthrax, and typhus, uses a previously undescribed mechanism. Knowing the mechanism may allow the development of specific inhibitors for this enzyme.

    Science, this issue p. 507

  17. Conservation

    Patterns of biodiversity change

    1. Julia Fahrenkamp-Uppenbrink

    Invasive species and climate change are altering the composition of ecosystems worldwide. In a Perspective, Magurran considers the effects of these changes, which come in addition to natural changes in ecosystem composition. For example, species turnover in rivers in Trinidad and Tobago has doubled compared to that seen in historical data, and ocean warming has led to an influx of warm-adapted species in the sea south of Norway. To conserve biodiversity, it will be important to understand the patterns of turnover and invasion. Rather than merely preserve the status quo, conservation managers will increasingly need to accommodate species turnover in their planning.

    Science, this issue p. 448

  18. Evolution

    Genetics of bird mating systems

    1. Julia Fahrenkamp-Uppenbrink

    Elaborate courtship behaviors are no rarity in birds, but some species even have differently colored types of males and females—or morphs—with different reproductive strategies. In a Perspective, Taylor and Campagna discuss recent studies that shed light on how these morphs evolved. The results show that supergenes (linked genes that are inherited together) play a key role: Chromosomal inversions of these supergenes in some, but not all, birds lead to the evolution of the different morphs, which survive over the course of evolution because each reproductive strategy has distinct advantages and disadvantages.

    Science, this issue p. 446

  19. Molecular Evolution

    Environmental changes bridge evolutionary valleys

    1. Philip Yeagle

    Molecular evolution of individual protein molecules can be described in a “landscape” of possible amino acid sequences containing peaks and valleys. Peaks characterize the beneficial nature of particular sequences for the success of organismal reproduction. Steinberg and Ostermeier designed a way for bacteria evolving under lab conditions to cross valleys in this landscape to achieve superior fitness outcomes.

    Sci. Adv. 10.1126.sciadv.1500921 (2016).

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