This Week in Science

Science  09 May 2014:
Vol. 344, Issue 6184, pp. 555
  1. Under the Dome

    CREDIT: HE ET AL.

    The superconducting transition temperature Tc of copper oxides has a dome-shaped dependence on chemical doping. Whether there is a quantum critical point (QCP) beneath the dome, and whether it is related to the enigmatic pseudogap, has been heavily debated. Two papers address this question in two different families of Bi-based cuprates. In (Bi,Pb)2(Sr,La)2CuO6+δ, He et al. (p. 608) found that the Fermi surface (FS) undergoes a topological change as doping is increased, which points to the existence of a QCP at a doping close to the maximum in Tc, seemingly uncorrelated with the pseudogap. Fujita et al. (p. 612) studied a range of dopings in Bi2Sr2CaCu2O8+δ to find an FS reconstruction simultaneous with the disappearance of both rotational and translational symmetry breaking, the latter of which has been associated with the pseudogap. These findings point to a concealed QCP.

  2. One Hormone, Two Phases

    The switch from vegetative growth to flowering in the plant Arabidopsis involves two phases—inflorescence branching and flowering. Yamaguchi et al. (p. 638) examined how the phytohormone gibberellin regulates each phase differently. First, gibberellin levels increase and stimulate production of key flowering factors, one of which degrades gibberellin. As gibberellin levels then fall, the next phase of flowering factors is released from gibberellin repression. By regulating inflorescence branching separately from flowering, this system determines overall seed yield.

  3. Individualism Rules?

    On a diverse and large set of cognitive tests, subjects in East Asian countries are more inclined to display collectivist choices, whereas subjects in the United States are more inclined to score as individualists. Talhelm et al. (p. 603; see the Perspective by Henrich) suggest that one historical source of influence was societal patterns of farming rice versus wheat, based on three cognitive measures of individualism and collectivism in 1000 subjects from rice- and wheat-growing regions in China.

  4. Upgrading Methane Sans Oxygen

    Direct routes to converting methane to higher hydrocarbons can allow natural gas to be used to provide chemical feedstocks. However, the reaction conditions needed to activate the strong C-H bond tend to overoxidize the products. Guo et al. (p. 616) report a high-temperature nonoxidative route that exposes methane to isolated iron sites on a silica catalyst. Methyl radicals were generated and coupled in the gas phase to form ethylene and aromatics along with hydrogen. The isolation of the active sites avoided surface reactions between the radicals that would deposit solid carbon.

  5. Forget It!

    When examining the relationship between the production of new neurons in the hippocampus and memory, studies have generally first manipulated hippocampal neurogenesis and afterward investigated memory formation and found that new neurons help to encode new memories. However, when investigating how similar manipulations of neurogenesis impact established hippocampus-dependent memories, Akers et al. (p. 598; see the Perspective by Mongiat and Schinder) uncovered a role for neurogenesis in memory clearance. Thus, the continuous addition of new neurons both degrades existing information stored in hippocampal circuits and simultaneously provides substrates for new learning.

  6. Self-Healing Larger Wounds

    By loading a polymer with pockets of monomer, it is possible to heal small cracks in a sample through the polymerization of the monomer following the formation of a crack. However, large holes are much harder to repair. White et al. (p. 620; see the Perspective by Zhao and Arruda) developed a vascular-like repair system involving a dual-stage strategy to self-heal epoxy thermosets. After injecting a damaged site with precursors, a gel with reversible cross-links rapidly formed, so the material stayed in place that then solidified further upon cross-linking. The approach successfully patched holes larger than 3 centimeters in diameter.

  7. Nanowire Growth Observed

    In the hypothetical microcrucible growth mechanism for nanowires, a molten catalytic particle located in a pore on a substrate continually feeds the outward growth of the wire. To observe such a mechanism requires the ability to examine nanowire growth in situ. Boston et al. (p. 623) studied various stages of Y2BaCuO5 nanowire growth using transmission electron microscopy and were able to observe a microcrucible growth mechanism directly.

  8. Help the Aged

    CREDIT: SINHA ET AL.

    Muscle function declines with age, as does neurogenesis in certain brain regions. Two teams analyzed the effects of heterochronic parabiosis in mice. Sinha et al. (p. 649) found that when an aged mouse shares a circulatory system with a youthful mouse, the aged mouse sees improved muscle function, and Katsimpardi et al. (p. 630) observed increased generation of olfactory neurons. In both cases, Growth Differentiation Factor 11 appeared to be one of the key components of the young blood.

  9. T Cells for Epithelial Tumors

    Malignant tumors harbor genetic alterations. Recently, adoptive T cell therapies have taken advantage of this: T cells specific for mutations in tumors are infused into patients to generate an antitumor immune response. Although therapeutic benefit has been seen for melanomas, effectiveness against more common epithelial tumors is unclear. Using whole-exome sequencing, Tran et al. (p. 641) identified tumor-infiltrating CD4+ T cells specific for a mutated antigen expressed by a tumor from a patient with metastatic cholangiocarcinoma. Infusion of this patient with an expanded-population, mutation-specific T cell resulted in tumor regression and stabilization of disease.

  10. Hearing Aid

    Many millions of people across the globe are subject to hearing loss. Géléoc and Holt (10.1126/science.1241062) review recent developments in potential therapeutic strategies to restore inner-ear function in patients with acquired or genetic forms of deafness. While challenges remain, fundamental research in molecular, gene, and stem-cell therapies has enabled progress toward developing alternatives to conventional, sound amplification–based prostheses.

  11. Extracting Spatial Information

    CREDIT: DORUK GOLCU

    The location of a rat can be deciphered from hippocampal activity by detecting the firing of individual place-selective neurons. In contrast, the local field potential (LFP), which arises from the coherent voltage fluctuations of large hippocampal cell populations, has been hard to decode. Agarwal et al. (p. 626) worked out how to recover positional information exclusively from multiple-site LFP measurements in the rat hippocampus. The information was as precise as that derived from spiking place cells. The approach might also be applicable more generally for deciphering information from coherent population activity anywhere in the brain.

  12. Recognize and Protect

    Molecular chaperones play a key role in maintaining protein homeostasis in the cell by preventing protein aggregation and misfolding. Chaperone-substrate complexes tend to be large and dynamic, making structure determination challenging. Saio et al. (10.1126/science.1250494; see the Perspective by Gamerdinger and Deuerling) used advanced NMR spectroscopy techniques to determine the structure of three trigger factor (TF) chaperone molecules in complex with the unfolded substrate, alkaline phosphatase (PhoA), and of each of the TFs in complex with the relevant region of PhoA. TF binds at multiple sites on PhoA through hydrophobic contacts, thus shielding these residues from solvent and preventing aggregation. The stability of the complex increases as longer PhoA regions are engaged by TF, and the multivalent binding keeps the substrate in an extended conformation.

  13. One Swell Ion Channel

    When mammalian cells are faced with osmotic challenges, they need to swell or shrink. The molecular characterization of the volume-regulated anion channel (VRAC) remains unknown, although many candidate proteins have been proposed. Voss et al. (p. 634, published online 10 April; see the Perspective by Mindell) used a genome-wide screen to identify a group of leucine-rich repeat–containing (LRRC) proteins necessary for forming VRAC. Suppression of LRRC8A nearly eliminated the presence of VRAC in mammalian cells. A heterooligomer of LRRC proteins appears to form VRAC. Identification of VRAC components is an essential step forward in the understanding of swelling-activated ion channels and provides opportunities for understanding both the mechanism of the channel and its role in physiology.

  14. Gata6 Controls Peritoneal Macs

    Macrophages seed tissues throughout the body and are shaped both phenotypically and functionally by the microenvironment they inhabit. Despite such heterogeneity, most tissue macrophages self-renew by local proliferation. How this is regulated, however, is unclear. Rosas et al. (p. 645, published online 24 April) used gene expression analysis to show that the transcription factor Gata6 is specifically expressed in peritoneal macrophages. Gata6 was critical for maintaining the transcriptional signature of peritoneal macrophages and for their proliferative renewal during homeostasis and under inflammatory conditions.