This Week in Science

Science  01 Aug 2014:
Vol. 345, Issue 6196, pp. 526
  1. Modeling Digits

    How do fingers know where to grow?

    1. Beverly A. Purnell

    Limbs self-organize in development


    Most researchers today believe that each finger forms because of its unique position within the early limb bud. However, 30 years ago, developmental biologists proposed that the arrangement of fingers followed the Turing pattern, a self-organizing process during early embryo development. Raspopovic et al. provide evidence to support a Turing mechanism (see the Perspective by Zuniga and Zeller). They reveal that Bmp and Wnt signaling pathways, together with the gene Sox9, form a Turing network. The authors used this network to generate a computer model capable of accurately reproducing the patterns that cells follow as the embryo grows fingers.

    Science, this issue p. 566; see also p. 516

  2. Dinosaur Evolution

    Turning large dinosaurs into small birds

    1. Sacha Vignieri

    Most paleontologists agree that birds are descended from dinosaurs. How did such large terrestrial or aquatic animals evolve into small feathered fliers? Lee et al. used two large databases of theropod morphology to explore possible evolutionary patterns that may have driven this dramatic transformation (see the Perspective by Benton). They found no clear pattern of miniaturization across the entire clade of Theropoda. However, several lines of evidence suggested that the lineage leading to birds underwent sustained miniaturization. Within that lineage, body sizes decreased and species evolved faster. They also developed ecological and morphological innovations linked to smaller body sizes.

    Science, this issue p. 562; see also p. 508

  3. Co-Infection

    Parasites make it hard to fight viruses

    1. Kristen L. Mueller

    Microbial co-infections challenge the immune system—different pathogens often require different flavors of immune responses for their elimination or containment (see the Perspective by Maizels and Gause). Two teams studied what happens when parasitic worms and viruses infect mice at the same time. Reese et al. found that parasite co-infection woke up a dormant virus. Osborne et al. found that mice already infected with parasitic worms were worse at fighting off viruses. In both cases, worms skewed the immune response so that the immune cells and the molecules they secreted created an environment favorable for the worm at the expense of antiviral immunity.

    Science, this issue p. 573 and p. 578; see also p. 517

  4. Chronic Pain

    A neuropeptide kills patient's motivation

    1. Peter Stern

    Chronic pain is not only extremely disturbing and unpleasant; it can also make people depressed and demotivated. What causes these effects? Schwartz et al. discovered that chronic pain causes changes in the way a neuropeptide called galanin affects certain neurons in a brain region called the nucleus accumbens (see the Perspective by Fields). Galanin influences a variety of behaviors, including feeding and certain aspects of pain. In this case, it depresses synaptic transmission at specific excitatory synapses. It does so, in part, by changing the ratio of subunits of an important receptor protein.

    Science, this issue p. 535; see also p. 513

  5. Catalysis

    Converting CO2 into methanol by catalysis

    1. Phil Szuromi

    By hydrogenating CO2, scientists can transform a greenhouse gas into methanol, a desirable fuel. Graciani et al. cast copper in the role of the highly active catalyst for this reaction by putting copper particles on cerium oxide. The interface between the cerium oxide and the copper enables the reverse water-gas shift reaction that converts CO2 into CO, which reacts more readily with hydrogen to make methanol. This result takes a step forward in innovating catalysts for this environmentally friendly process.

    Science, this issue p. 546

  6. Quantum Information

    Toward quantum teleportation on demand

    1. Ian S. Osborne

    Artist's view of a diamond defect


    Quantum information processing relies on the ability to store, manipulate, and propagate information encoded in quantum states of matter. Doing so, however, may destroy or compromise these delicate quantum states. Pfaff et al. present a quantum teleportation protocol that uses two defects in diamond 3 m apart (see the Perspective by Atatüre and Morton). They then map the quantum state of one of the diamond defects onto the other. The work presents a key building block for the successful development of larger quantum networks.

    Science, this issue p. 532; see also p. 510

  7. Cancer

    Preventing drug resistance in breast cancer

    1. Leslie K. Ferrarelli

    Some patients with breast cancer respond to therapy with trastuzumab, but many later develop resistance. Breast tumors often lack SIRT6, which encodes an enzyme that is a tumor suppressor. Thirumurthi et al. found that the kinase AKT phosphorylated SIRT6, triggering a chain of events that breaks it down. Patients whose breast tumors had high SIRT6 levels and low AKT levels had higher survival rates. Preventing SIRT6 from being degraded or phosphorylated made resistant breast cancer cells less resistant to trastuzumab, suggesting that high SIRT6 may improve therapeutic responses in patients.

    Sci. Signal. 7, ra71 (2014).

  8. Cell Biology

    New tools for sorting good and bad fat cells

    1. Megan Frisk

    There's “good fat” and there's “bad fat.” Brown adipose tissue is considered “good” because it burns calories and could thus be harnessed to combat obesity. When brown fat cells develop within “bad” white fat, the tissue is called “beige.” Ussar et al. developed tools for imaging these cell subtypes or targeting drugs to them. The authors identified three protein markers of white, beige, and brown fat cells—ASC-1, PAT2, and P2RX5—which they selected using computational methods, confirmed in mice, and then verified in human adipose tissue. The proteins sit on the cell surface, making them especially useful for imaging tissue and guiding drugs.

    Sci. Transl. Med. 6, 247ra103 (2014)

  9. Novae

    Gamma-ray novas may be garden variety

    1. Margaret M. Moerchen

    When astronomers detected gamma rays from the nova V407 Cyg, an explosive mass transfer from a red giant onto a white dwarf, they found it surprising enough. They blamed the rays on strong stellar winds enabling particle acceleration. Now, the Fermi-LAT Collaboration has observed gamma rays from three more novas, all lacking the strong winds. Although the three sources vary slightly in nature, none is particularly unusual. If all novas emit gamma rays, then astronomers would expect to see the same number of novas that they did in fact see within a 5-kpc distance over 5 years.

    Science, this issue p. 554

  10. Interneurons

    A central player in brain computation

    1. Peter Stern

    A small subgroup of nerve cells plays a central role in information processing in the brain. Hu et al. review our present knowledge about the specific makeup of these neurons. Specifically, the individual properties of the molecules, their distribution within the cell, and the anatomy of the cells themselves are described. This information helps to explain why these neurons are so important for the function of microcircuits in the brain, as well as the behavior of the organism. This detailed level of understanding will become relevant as these cells become future targets for the treatment of neurological diseases.

    Science, this issue 10.1126/science.1255263

  11. Computational Sociology

    A macroscopic view of cultural history

    1. Barbara R. Jasny

    Sociologists and anthropologists study the growth and evolution of human culture, but it is hard to measure cultural interactions on a historical time scale. Schich et al. developed a tool for extracting information about cultural history from simple but large sets of birth and death records. A network of cultural centers connected via the birth and death of more than 150,000 notable individuals revealed human mobility patterns and cultural attraction dynamics. Patterns of city growth over a period of 2000 years differed between countries, but the distribution of birth-to-death distances remained unchanged over more than eight centuries.

    Science, this issue p. 558

  12. Photovoltaics

    A layered approach improves solar cells

    1. Phil Szuromi

    Perovskite films received a boost in photovoltaic efficiency through controlled formation of charge-generating films and improved current transfer to the electrodes. Zhou et al. lowered the defect density of the film by controlling humidity while the perovskite film formed from lead chloride and methylammonium iodide. Low-temperature processing steps allowed the use of materials that draw current out of the perovskite layer more efficiently. These and other modifications enabled a maximum cell efficiency of just over 19% and an average of 16.6%.

    Science, this issue p. 542

  13. Mobile DNA in Cancer

    Hitchhiking through the tumor genome

    1. Paula A. Kiberstis

    Retrotransposons are DNA repeat sequences that are constantly on the move. By poaching certain cellular enzymes, they copy and insert themselves at new sites in the genome. Sometimes they carry along adjacent DNA sequences, a process called 3′ transduction. Tubio et al. found that 3′ transduction is a common event in human tumors. Because this process can scatter genes and regulatory sequences across the genome, it may represent yet another mechanism by which tumor cells acquire new mutations that help them survive and grow.

    Science, this issue 10.1126/science.1251343

  14. HIV Latency

    A not-so-random integration for HIV

    1. Kristen L. Mueller

    Even in the face of a cocktail of antiretroviral drugs, HIV manages to hang on. It does so by integrating its own genome into those of host cells, where it persists in a latent state. To better understand this process, Wagner et al. determined the sites where HIV integrated into three HIV-infected patients treated with antiretroviral drugs for more than a decade. They found an overrepresentation of sites where HIV integrated into genes associated with cancer and cell proliferation. Also, multiple cells in the same individual harbored the same integration sites. This suggests that integration into specific genes may drive cell proliferation and viral persistence.

    Science, this issue p. 570

  15. Asteroseismology

    A finger on the pulse of young stars

    1. Margaret M. Moerchen

    Adolescent stars quiver and quake before the onset of nuclear fusion in their cores. Zwintz et al. confirm theoretical predictions that the frequency of the seismic oscillations in a given star is tied to its evolutionary status (see the Perspective by Stahler and Palla). As the protostar evolves and contracts, growing hotter and denser, it pulsates faster. Though previously applied only to aging stars, asteroseismology now offers a powerful tool for discerning the ages of very young stars. The relative timing of star formation within young clusters especially benefits from this refinement, as stars there are often tagged with one blanket age.

    Science, this issue p. 550; see also p. 514

  16. Epigenomics

    Ancient patterns reveal species divergence

    1. Julia Fahrenkamp-Uppenbrink

    Modifications to DNA, termed epigenetic changes, regulate the expression of genes. Scientists have recently detected such epigenetic changes in the remains of human ancestors that have been preserved for thousands of years. In a Perspective, Orlando and Willerslev explain that differences between the ancient epigenetic patterns and those in living humans can shed light on how humans have adapted to changing environments and how species have diverged from each other. Epigenetic patterns are complicated and vary with cell type, age, gender, health, and the environment. Further experimental advances are needed to fully unlock the epigenetic information in ancient DNA.

    Science, this issue p. 511

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