This Week in Science

Science  15 Aug 2014:
Vol. 345, Issue 6198, pp. 782
  1. Robotics

    Large-scale robotic self-assembly

    1. Marc S. Lavine
    A swarm of mini-robots on the moveCREDIT: CURTIS CLARK/WIKIMEDIA COMMONS

    When individuals swarm, they must somehow communicate to direct collective motion. Swarms of robots need to deal with outliers, such as robots that move more slowly than the rest. Rubenstein et al. created a large swarm of programmed robots that can form collaborations using only local information. The robots could communicate only with nearby members, within about three times their diameter. They were able to assemble into complex preprogrammed shapes. If the robots' formation hit snags when they bumped into one another or because of an outlier, additional algorithms guided them to rectify their collective movements.

    Science, this issue p. 795

  2. Place Cells

    Nerve cells displaying extra large spaces

    1. Peter Stern

    Rats use brain cells called “place” cells to figure out where they are. Rich et al. used mazes or tracks many meters long—the size of rats' ranges in the wild—to investigate how rats represent a very large environment or extended experience in their brain. As novel environments became larger and larger, the rats' brains recruited new place cells. However, no matter how large the environment became, some cells always remained silent, perhaps as a reserve for other environments yet to be visited.

    Science, this issue p. 814

  3. Interstellar Dust

    Can you spot a speck of space dust?

    1. Margaret M. Moerchen

    NASA's Stardust spacecraft has been collecting cosmic dust: Aerogel tiles and aluminum foil sat for nearly 200 days in the interstellar dust stream before returning to Earth. Citizen scientists identified most of the 71 tracks where particles were caught in the aerogel, and scanning electron microscopy revealed 25 craterlike features where particles punched through the foil. By performing trajectory and composition analysis, Westphal et al. report that seven of the particles may have an interstellar origin. These dust particles have surprisingly diverse mineral content and structure as compared with models of interstellar dust based on previous astronomical observations.

    Science, this issue p. 786

  4. Cancer

    A potential target in a deadly brain cancer

    1. Wei Wong

    A growth factor receptor called EGFR is often overactive in glioblastoma, a common and frequently lethal form of brain cancer. Kusne et al. found that the kinase aPKC was stimulated in glioblastoma cells not only by abnormally active EGFR but also in response to a cytokine called TNF-α released by immune cells that infiltrate the tumors. A drug that inhibited aPKC reduced tumor growth in a mouse model of glioblastoma, and glioblastoma patients with high aPKC levels had shorter survival times. Thus, two cancer-promoting pathways converge on aPKC, making it an attractive therapeutic target in glioblastoma.

    Sci. Signal. 7, ra75 (2014).

  5. Plant Science

    Strangleweed shares too much information

    1. Pamela J. Hines
    Parasitic dodder plant strangles its hostCREDIT: MICHAEL RUBENSTEIN/HARVARD UNIVERSITY\WYSS INSTITUTE

    Because RNA normally functions within an individual cell, we generally think that we keep our RNAs to ourselves. Kim et al. now show that the parasitic dodder plant breaks that rule. When dodder attacks a host plant, it opens up a conduit through which messenger and perhaps other regulatory RNAs are exchanged between parasite and host. Because a single dodder plant can attack multiple hosts, such exchanges may underlie instances of genes transferring between species.

    Science, this issue p. 808

  6. Cystic Fibrosis

    A breathtaking tale of sticky mucus

    1. Paula A. Kiberstis

    Patients with cystic fibrosis have difficulty breathing because their airways are clogged with thick mucus. Does this mucus accumulate because there is a defect in the way it is produced? Or does it accumulate because of other disease features, such as dehydration or airway wall remodeling? Distinguishing between these possibilities is important for future drug development. In a study of piglets with cystic fibrosis, Hoegger et al. identify mucus production as the primary defect (see the Perspective by Wine). The airway glands of the piglets synthesized strands of mucus normally, but the strands were never released and stayed tethered to the gland ducts.

    Science, this issue p. 818; see also p. 730

  7. Cell Therapy

    A Swiss Army knife for treating sepsis

    1. Kelly LaMarco

    Sepsis is a complication of infection that kills ∼7 million people a year, with no successful molecular therapy. But cells are more versatile than molecules: They make products and respond to their environments. Now, Fletcher et al. investigate whether cells are better equipped to battle this multifocal disease. One injection of anti-inflammatory cells derived from the lymph nodes dramatically increased survival in two mouse models of sepsis under conditions that mimic those in the clinic. These beneficial cells reduced the deadly “cytokine storm” associated with sepsis.

    Sci. Transl. Med. 6, 249ra109 (2014).

  8. RNA Nanostructures

    The future of RNA origami writ large

    1. Phil Szuromi

    Researchers have long fabricated intricate nanostructures from carefully linked DNA strands. Now they can use RNA made by gene expression, which avoids the costly strand synthesis and lengthy annealing steps necessary with DNA origami. Geary et al. used molecular modeling to extend the size of folded RNA origami structures (see the Perspective by Leontis and Westhof). The modeling revealed assembly patterns for linking single-stranded RNA into A-form helices. The authors created two-dimensional structures as large as 660 nucleotides on mica surfaces.

    Science, this issue p. 799; see also p. 732

  9. Water Engineering

    Sourcing corrosive sewer sulfides

    1. Nicholas S. Wigginton

    Sewer systems are corroding at an alarming rate, costing governments billions of dollars to replace. Differences among water treatment systems make it difficult to track down the source of corrosive sulfide responsible for this damage. Pikaar et al. performed an extensive industry survey and sampling campaign across Australia (see the Perspective by Rauch and Kleidorfer). Aluminum sulfate added as a coagulant during drinking water treatment was the primary culprit in corroding sewer systems. Modifying this common treatment strategy to include sulfate-free coagulants could dramatically reduce sewer corrosion across the globe.

    Science, this issue p. 812; see also p. 734

  10. In Utero Effects

    The nutritional sins of the mother…

    1. Beverly A. Purnell

    Prenatal exposures of a mother can affect the health of her offspring, but how? Radford et al. found that the male progeny of undernourished pregnant mice had altered DNA chemistry in their sperm. In addition, the offspring displayed compromised metabolic health. The specific affected genes not only lost DNA methylation but also lacked the normal sperm DNA packaging factors (protamines) and instead were enriched in nucleosomes. Thus, when subjected to a suboptimal prenatal environment, offspring feel the effects of the maternal assault.

    Science, this issue p. 1255903

  11. Interstellar Dust

    Clues to a mystery with RAVE results

    1. Margaret M. Moerchen

    An unknown interloper systematically picks off light from galactic sources, snatching at specific wavelengths ranging from the ultraviolet to the infrared. The cause of what astronomers term diffuse interstellar bands (DIBs) still evades identification. Kos et al. combined nearly 500,000 stellar spectra from the RAVE survey to make a telling map that may clue us in further. This pseudo–three-dimensional map shows the distribution of the carrier that absorbs light at 862 nm, and it closely follows a separate map of interstellar dust, but with a significantly larger scale height in the Galactic plane. Though this is only one DIB of many, this analysis sets a path for the future study of others.

    Science, this issue p. 791

  12. Photosynthesis

    Setting the stage for release of oxygen

    1. Jake Yeston

    Plants transform water into the oxygen we breathe using a protein-bound cluster of four manganese (Mn) ions and a calcium ion. Cox et al. now establish the precise electronic structure in that cluster immediately before formation of the O-O bond (see the Perspective by Britt and Oyala). Using the technique of electron paramagnetic resonance spectroscopy, they confirm a hypothesis that all four Mn ions are octahedrally coordinated and in the 4+ oxidation state. Such clues to the efficiency of the photosynthetic process, so essential to life on Earth, may also facilitate the development of artificial waters-plitting catalysts.

    Science, this issue p. 804; see also p. 736

  13. Cell Reprogramming

    Factor in oocyte assists reprogramming

    1. Beverly A. Purnell

    Unfertilized eggs contain components that can dedifferentiate other cells that have gone down the path toward a specific cell fate. Gonzalez-Muñoz et al. show that the protein-folding factor ASF1A facilitates this reprogramming event and it acts at a particular phase of germ cell division termed metaphase II. ASF1A helps turn differentiated cells such as human adult dermal fibroblasts into undifferentiated pluripotent stem cells.

    Science, this issue p. 822

  14. Transdifferentiation

    Epigenetics direct transdifferentiation

    1. Beverly A. Purnell

    To make an entire animal, many and varied cell types form and interact. Some of these differentiated cells take a U-turn and can de-differentiate or transdifferentiate to another cell fate. Although relatively rare in nature, Zuryn et al. followed such a program in the tiny roundworm Caenorhabditis elegans, where a rectal cell–to–motor neuron conversion is seen. Transcription factors with conserved roles in cell plasticity and terminal fate selection partner up with specific histone-modifying enzymes in discrete steps to specify separate sequential phases of cell identity.

    Science, this issue p. 826

  15. Synthetic Biology

    Toward an “artificial cell” on a chip

    1. Guy Riddihough

    Cell-free systems that reconstitute biochemical pathways have been critical for unraveling the inner workings of the cell. Karzbrun et al. created a highly miniaturized cell-free system on a silicon chip. A series of tiny linked compartments were fabricated on the chip, in which DNA-driven reactions occurred, with materials flowing into and diffusing between the compartments. The system recreated oscillating protein expression patterns and protein gradients, and provides a stepping stone to creating “artificial cells” on a chip.

    Science, this issue p. 829

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