This Week in Science

Science  30 Aug 2013:
Vol. 341, Issue 6149, pp. 935
  1. Lamins and Tissue Stiffness

    CREDIT: V. ALTOUNIAN/SCIENCE

    Microenvironment can influence cell fate and behavior; for example, extracellular matrix (ECM) stiffness increases cell proliferation, and ECM rigidity induces disorders in tissue morphogenesis by increasing cell tension. Swift et al. (1240104; see the Perspective by Bainer and Weaver) used proteomics to identify molecules that are mechanical sensors for tissue elasticity in the nucleus and discovered that expression of lamin-A levels apparently functions as a “mechanostat.”

  2. Strategies for Metal-Organic Frameworks

    Metal-organic frameworks are porous materials that can exhibit very high surface areas that have potential for applications such as gas storage and separation, as well as catalysis. Furukawa et al. (1230444) review the structures devised so far and discuss the design strategies that allow families of materials to be synthesized and modified with similar framework topology but vary in pore size and type of functional groups present on the linkers.

  3. A Uranian Trojan

    Bodies that share their orbit with that of a planet and that trail or lead the planet by 60° are called Trojans. Based on data from the Canada-France-Hawaii Telescope, Alexandersen et al. (p. 994) have found an object shadowing Uranus that is predicted to remain a Trojan for at least 700,000 years and to stay in co-orbital motion for around one million years before escaping.

  4. Depression and the Habenula

    The lateral habenula (LHb) appears to have a role in depression. However, the underlying mechanisms are poorly understood, and by using multiple rodent models of depression, Li et al. (p. 1016) identified a signaling pathway and associated neuronal adaptations in which the enzyme βCaMKII was selectively up-regulated in the LHb. Manipulations that enhanced βCaMKII levels increased depression-related phenotypes, and RNA interference of CaMKIIb blunted depression. Enhanced βCaMKII levels in the habenula promoted excitatory synaptic transmission on these neurons and increased action potential firing mediated by an up-regulation of a specific subtype of glutamate receptors.

  5. Ice Lubricant

    The Greenland and Antarctic ice sheets both possess hydrological systems that allow water accumulating from the melting of surface ice to be transported to the base of the ice sheet. If that water, when it reaches the ice-bedrock interface, is distributed over large areas, it will lubricate rapid ice sheet flow toward the sea. Bamber et al. (p. 997) report the existence of a large, 750-km-long subglacial canyon in northern Greenland, which may act as a channel for the transport of basal meltwater to the margin of the ice sheet and thus influence overall ice sheet dynamics.

  6. Follow the Leader

    How birds migrate between wintering and breeding grounds, often over thousands of kilometers through difficult conditions, remains mysterious. The recovery of North American Whooping Cranes by release of captive-reared birds trained to migrate by following aircraft provided an opportunity for Mueller et al. (p. 999; see the cover) to analyze 8 years of data for individual birds. The presence of older birds within a group of migrating cranes significantly decreased the deviations the flock took from a straight line migration path. The lack of evidence for a genetic component indicates that social learning dominates any innate capacity in developing migratory behavior.

  7. Egg WAVE1

    Eggs not only activate sperm nuclei for normal development but also reprogram transplanted somatic nuclei. In addition to its well-established cytoplasmic role in actin organization, Miyamoto et al. (p. 1002) discovered that the Wiskott-Aldrich syndrome protein family member 1 in oocytes cooperates with transcriptional machineries in the nucleus to activate previously silenced genes.

  8. Cilium Conundrum

    The cilium has emerged as the antenna of eukaryotic cells, having numerous functions in sensory reception and developmental signaling. Several disorders, such as polycystic kidney disease, are the result of compromised cilia structure. Bhogaraju et al. (p. 1009) elucidate how the intraflagellar transport machinery recognizes tubulin, a ciliary cargo that is integral to cilium maintenance and formation and is constantly turned over at the cilium tip.

  9. Hydrogel Stretch

    CREDIT: KEPLINGER ET AL.

    A range of stretchable, conductive materials can be made either by making an electrical conductor more stretchable or by adding an electrical conductor to a stretchable material. Keplinger et al. (p. 984; see the Perspective by Rogers) have added to the possibilities of an alternative stretchable ionic conductor based on a hydrogel material used to make deformable devices that are fully transparent to light over the visible spectrum and that can withstand high voltages and high frequencies.

  10. Oxide Chemistry Below the Surface

    CREDIT: SETVIN ET AL.

    Although metal oxides, such as titanium dioxide (TiO2), are used for catalytic oxidation reactions and photocatalysis, the O2 does not react directly with substrates. Vacancies in the surface region of the TiO2 rutile phase can transfer a negative charge to adsorbed O2 to create more reactive species. By contrast, in anatase—the phase associated with nanoscale TiO2 particles—subsurface vacancies form. Setvin et al. (p. 988) used a scanning tunneling microscopy tip to pull these vacancies to the surface in a niobium-doped anatase crystal and followed the transformation of adsorbed O2 into a peroxo species and a bridging O2 dimer.

  11. Burden of Poverty

    Lacking money or time can lead one to make poorer decisions, possibly because poverty imposes a cognitive load that saps attention and reduces effort. Mani et al. (p. 976; see the Perspective by Vohs) gathered evidence from shoppers in a New Jersey mall and from farmers in Tamil Nadu, India. They found that considering a projected financial decision, such as how to pay for a car repair, affects people's performance on unrelated spatial and reasoning tasks. Lower-income individuals performed poorly if the repairs were expensive but did fine if the cost was low, whereas higher-income individuals performed well in both conditions, as if the projected financial burden imposed no cognitive pressure. Similarly, the sugarcane farmers from Tamil Nadu performed these tasks better after harvest than before.

  12. The Galaxy Center in X-rays

    At the center of our Galaxy there is a black hole 4-million-fold more massive than the Sun. Wang et al. (p. 981; see the Perspective by Schnittman) report x-ray data on the accretion flow around this supermassive black hole, revealing how it interacts with its surroundings. The data rule out the possibility that the quiescent (that is, flare-free) x-rays observed are produced by coronal emission from a population of stars at the center of the Galaxy and also rule out the possibility that there is a pure radiatively inefficient accretion flow with no outflows.

  13. Pluripotency Control

    The transcription factors Pou5f1/Oct4, Sox2, and Nanog play central roles in pluripotency control in mammalian embryonic stem (ES) cells. The evolution of the pluripotency regulatory network and its roles during early development of nonmammalian vertebrates is unknown. Leichsenring et al. (p. 1005, published online 15 August) show that in zebrafish embryos, Pou5f1 controls priming and transcriptional activation of the first zygotically expressed genes. This mechanism for transition from the transcriptionally silent cleavage stage to the transcriptionally active blastula stage may have evolved to control the prolonged cell pluripotency state in mammalian early development and ES cells, establishing a link between zygotic gene activation and pluripotency control.

  14. Local Acceleration

    CREDIT: REEVES ET AL.

    How the electrons trapped in Earth-encircling Van Allen radiation belts get accelerated has been debated since their discovery in 1958. Reeves et al. (p. 991, published online 25 July) used data from the Van Allen Radiation Belt Storm Probes, launched by NASA on 30 August 2012, to discover that radiation belt electrons are accelerated locally by wave-particle interactions, rather than by radial transport from regions of weaker to stronger magnetic fields.

  15. Moving Bricks with MraY

    Peptidoglycan, the building brick of bacterial cell walls, is synthesized in the cytoplasm and must be transported across the cell membrane. To achieve this, it is attached to a carrier lipid by the integral membrane protein MraY. MraY is targeted by natural antibacterials and is a promising antibiotic target. Chung et al. (p. 1012) report the crystal structure of MraY at 3.3 Å resolution. The structure, together with mutational mapping, outlines the location of the active site and provides interesting hints for how the enzyme binds the substrate and catalyzes attachment to the carrier lipid.

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