This Week in Science

Science  17 Jan 2014:
Vol. 343, Issue 6168, pp. 228
  1. Health Economy?

    The intensity of arguments over social science issues often seems inversely correlated with the quantity of experimental evidence. Taubman et al. (p. 263, published online 2 January; see the Policy Forum by Fisman) report on the latest analysis of an ongoing controlled experiment—the Oregon Health Insurance Experiment—that seeks to identify and quantify the effects of extending health insurance coverage to a low-income adult population. A substantial increase was observed in visits to the emergency departments of hospitals, corresponding to approximately 120 U.S. dollars per year more in hospital costs.

  2. Topochemical Polymerization

    In a topochemical reaction, chemical changes start at active sites in the solid and then proceed autocatalytically to neighboring regions. If one starts with a monomer that can form ordered structures similar to the final polymer, it is possible to polymerize chains in a fully ordered state and thus make very long single chains. Dou et al. (p. 272; see the Perspective by Goroff) describe an unexpected visible-light–induced polymerization of derivatives of a dye. Two of the derivatives underwent photoinduced single-crystal-to-single-crystal topochemical polymerization.

  3. The Secret Life of a Vaccine

    CREDIT: RAVINDRAN ET AL.

    Antigen-specific CD8÷ T cells play a central role in the adaptive immune response to viral infections and to cancer. Ravindran et al. (p. 313, published online 5 December) studied the successful yellow fever virus vaccine YF-17D to gain insight into its mechanism of action. The vaccine activated the nutrient deprivation sensor, GCN2 kinase, in dendritic cells. In transgenic mouse models, GCN2 activation promoted autophagy and antigen cross-presentation, enhancing the virus-specific CD8÷ T cell response. The findings suggest an important role for nutrient availability and autophagy in vaccine efficacy, which could aid more successful vaccine development.

  4. Regular Nanowires

    For a range of nanotechnology applications, semiconductor nanowires will need to be grown with high precision and control. Chou et al. (p. 281) studied the growth of gallium phosphide (GaP) nanowires using chemical vapor deposition within a transmission electron microscope and worked out conditions that could generate regular and predictable wire growth.

  5. What Does It All Mean?

    CREDIT: FELIX GROSS

    Strong emissions of methane have recently been observed from shallow sediments in Arctic seas. Berndt et al. (p. 284, published online 2 January) present a record of methane seepage from marine sediments off the coast of Svalbard showing that such emissions have been present for at least 3000 years, the result of normal seasonal fluctuations of bottom waters. Thus, contemporary observations of strong methane venting do not necessarily mean that the clathrates that are the source of the methane are decomposing at a faster rate than in the past.

  6. Renewable Breakdown Routine

    In order to transform cellulose-containing biomass into liquid fuels such as ethanol, it is first necessary to break down the cellulose into its constituent sugars. Efforts toward this end have focused on chemical protocols using concentrated acid or ionic liquid solvents, and on biochemical protocols using cellulase enzymes. Luterbacher et al. (p. 277) now show that γ-valerolactone, a small molecule solvent that can itself be sourced renewably from biomass, promotes efficient and selective thermal breakdown of cellulose in the presence of dilute aqueous acid.

  7. Drug With a (Re)Purpose

    Thalidomide, once infamous for its deleterious effects on fetal development, has re-emerged as a drug of great interest because of its beneficial immunomodulatory effects. A derivative drug called lenalidomide significantly extends the survival of patients with multiple myeloma, but the molecular mechanisms underlying its efficacy remain unclear (see the Perspective by Stewart). Building on a previous observation that thalidomide binds to cereblon, a ubiquitin ligase, Lu et al. (p. 305, published online 28 November) and Krönke et al. (p. 301, published online 28 November) show that in the presence of lenalidomide, cereblon selectively targets two B cell transcription factors (Ikaros family members, IKZF1 and IKZF3) for degradation. In myeloma cell lines and patient cells, down-regulation of IKZF1 and IKZF3 was necessary and sufficient for the drug's anticancer activity. Thus, lenalidomide may act, at least in part, by “grepurposing” a ubiquitin ligase.

  8. Identifying Drivers and Passengers

    Modern genomics is unearthing hundreds of genetic and epigenetic alterations associated with human cancers. It is important to delineate which of these alterations participate actively in tumor progression and/or metastases (driver mutations) and which are inconsequential (passenger mutations). To this end, Schramek et al. (p. 309) conducted an in vivo RNA interference screen in mice to test simultaneously the functionality of putative cancer genes and down-regulated messenger RNAs associated with tumor-initiating cells of squamous cell carcinomas (SCCs). Several candidates, including nonmuscle myosin-IIa, not previously viewed as tumor suppressors were uncovered.

  9. Long Live the Queen

    Eusociality is often considered to have arisen, at least in part, due to the inclusive fitness that workers gain through helping their queen sister to raise her offspring. Van Oystaeyen et al. (p. 287; see the Perspective by Chapuisat) characterized the sterility-inducing queen pheromone across three distantly related eusocial hymenopterans (a wasp, a bumblebee, and a desert ant) and synthesized data across 69 other species. Queen pheromones appear to be remarkably conserved, which suggests that reproductive manipulation has ancient roots.

  10. Wnt–β-Catenin in Germ Cells

    CREDIT: NORIKO HAMADA-KAWAGUCHI

    The Wnt–β-catenin pathway contributes to many signaling mechanisms during organismal development and carcinogenesis by regulating both transcription and cell adhesion. Hamada-Kawaguchi et al. (p. 294) demonstrate that this pathway must be activated in ovarian somatic cells to stop proliferation of germ cells in Drosophila. Phosphorylation of a tyrosine residue on β-catenin by the tyrosine kinase Btk turns on signaling in the niche cells by promoting transcriptional activity of β-catenin. Failure in this process resulted in ovarian tumors in the flies.

  11. Stubbornly Spherical

    The shape of the electron's charge distribution reflects the degree to which switching the direction of time impacts the basic ingredients of the universe. The Standard Model (SM) of particle physics predicts a very slight asphericity of the charge distribution, whereas SM extensions such as supersymmetry posit bigger and potentially measurable, but still tiny, deviations from a perfect sphere. Polar molecules have been identified as ideal settings for measuring this asymmetry, which should be reflected in a finite electric dipole moment (EDM) because of the extremely large effective electric fields that act on an electron inside such molecules. Using electron spin precession in the molecule ThO, Baron et al. (p. 269, published online 19 December; see the cover; see the Perspective by Brown) measured the EDM of the electron as consistent with zero. This excludes some of the extensions to the SM and sets a bound to the search for a nonzero EDM in other facilities, such as the Large Hadron Collider.

  12. ATP Receptor in Arabidopsis

    As well as its role as an intracellular energy source, extracellular adenosine triphosphate (ATP) has diverse functions as a signaling molecule. ATP receptors have been identified in animal cells, but searches based on structural homology have not identified ATP receptors in plants. Choi et al. (p. 290) have now identified an ATP receptor in the model plant Arabidopsis thaliana by tracking down the cause of mutations that leave mutant plants unresponsive to ATP signals. The receptor identified carries an intracellular kinase domain and an extracellular lectin domain.

  13. Germline Pol I

    RNA polymerase I (Pol I)–directed ribosomal RNA (rRNA) transcription has been extensively studied in mammalian cell lines and yeast. However, the functional significance of cell-specific regulation of Pol I transcription within developmental contexts in vivo remains unclear. Zhang et al. (p. 298) characterized a Drosophila Pol I regulatory complex and found that germline stem cells (GSCs) of the ovary exhibited increased levels of rRNA transcription relative to their immediate daughter cells. High levels of rRNA expression promoted GSC proliferation, with attenuation of Pol I activity showing effects during early germ cell differentiation.

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