This Week in Science

Science  21 Sep 2012:
Vol. 337, Issue 6101, pp. 1431
  1. What Kitty Shares with Kings

    CREDIT: STEVE FLAHERTY/WILD CAT EDUCATION AND CONSERVATION FUND

    Although long-studied, the underlying basis of mammalian coat patterns remains unclear. By studying a large number of cat species and varieties, Kaelin et al. (p. 1536) identified two genes, Taqpep and Edn3, as critical factors in the development of feline pigment patterns. Mutations in Taqpep are responsible for the blotched tabby pattern in domestic cats and the unusual coat of wild king cheetahs. Gene expression patterns in cat and cheetah skin suggest that Edn3 is a likely regulator of felid hair color. The findings support a common model for coat and pigment pattern formation in domestic and wild cats.

  2. Location, Location, Location

    It seems obvious that a person's residential neighborhood will influence their sense of well-being, but it has been difficult to nail down cause and effect. Ludwig et al. (p. 1505; see the Perspective by Sampson) describe the analysis, 10 to 15 years onward, of a large-scale social experiment carried out in five U.S. cities in the mid 1990s. Several thousand residents of poor neighborhoods were given housing vouchers that could only be used if they moved into much less poor neighborhoods. In comparison to a similar group of individuals who did not move, those who did experienced substantial improvement in their subjective well-being.

  3. N on P

    Nitrogen atoms form strong, relatively unreactive triple bonds with themselves (in N2) and with carbon (in cyanide and nitriles). In contrast, binding to transition metals often leaves an otherwise naked nitrogen center more prone to reactivity. Dielmann et al. (p. 1526) prepared a compound with nitrogen bound to divalent phosphorus, which acted more like a metal than a light element. Although the compound, formally a nitrene, was sufficiently stable to isolate at room temperature and characterize by x-ray diffraction, it transferred the nitrogen efficiently to unsaturated carbon compounds.

  4. Minimal Ice

    Water clusters comprising fewer than 100 molecules have long been studied in gas phase to model the more complex structures of ice and liquid water. At some stage, as clusters grow larger, they effectively become tiny crystals of ice, but it has been hard to pinpoint precisely where in the range between 100 and 1000 molecules the formal transition takes place. Pradzynski et al. (p. 1529) used vibrational spectroscopy to show that the onset of an icelike structure, indicated by a characteristically distinct absorption band in the infrared, occurs at a cluster size of approximately 275 molecules.

  5. Keeping Track of Photon Phase

    In optical interferometers or optical communications, information is often stored in terms of the phase of the waveform or light pulse. However, fluctuations and noise can give rise to random jitter in the phase and amplitude of the optical pulses, making it difficult to keep track of the phase. Yonezawa et al. (p. 1514) developed a technique based on quantum mechanical squeezing to determine the phase of randomly varying optical waveforms. The quantum mechanical technique enhanced the precision with which the phase could be determined and, as optical technologies continue to be miniaturized, should be helpful in applications within metrology.

  6. Patterning by Subtraction

    Soft lithographic patterning is usually a “positive” inking process. A polymer stamp is cured on a hard master substrate and then inked with molecules such as alkane thiols, which can then be transferred to a second substrate (such as gold). However, the resolution of the transferred pattern is often degraded by surface diffusion. Liao et al. (p. 1517; see the Perspective by Rogers) obtained higher resolution in a subtractive approach, in which oxygen-plasma–activated silicone stamps removed hydroxyl-terminated alkane thiols from gold surfaces. This lift-off process also removed the terminal gold atom bound to the alkane thiol. The bare regions could be backfilled with protein molecules, and multiple lift-off steps could create patterns with features as small as 40 nanometers.

  7. Slip-Sliding Apart

    One versatile means of synthesizing nanometer-scale cylinders has been to start with ring-shaped molecules that stack on top of each other. Huang et al. (p. 1521; see the Perspective by Zhang and Aida) took this approach a step further by giving the rings a flexible diameter. Specifically, rings were prepared consisting of six v-shaped building blocks with hydrophobic sides that could slide back and forth along one another and thereby expand or contract the pore at the center. The rings spontaneously stacked to form tubes in dilute aqueous solution, and heating induced contraction of the whole tube in a process that was readily reversible on cooling.

  8. A Pair of Planets Around a Pair of Stars

    CREDIT: NASA/JPL-CALTECH/T. PYLE

    Most of the planets we know about orbit a single star; however, most of the stars in our galaxy are not single. Based on data from the Kepler space telescope, Orosz et al. (p. 1511, published online 28 August) report the detection of a pair of planets orbiting a pair of stars. These two planets are the smallest of the known transiting circumbinary planets and have the shortest and longest orbital periods. The outer planet resides in the habitable zone—the “goldilocks” region where the temperatures could allow liquid water to exist. This discovery establishes that, despite the chaotic environment around a close binary star, a system of planets can form and persist.

  9. Identifying BAP1 Targets

    Inactivating mutations in the deubiquitinating enzyme BAP1 have been associated with cancer. Dey et al. (p. 1541, published online 9 August; see the Perspective by White and Harper) reveal molecular targets of the enzyme and show evidence for a role in leukemia. Mice specifically lacking the target of BAP1, HCF-1, in the bone marrow developed myeloid leukemia. BAP1 appears to be part of a complex that regulates modification of histones and gene expression important for normal hematopoiesis and tumor suppression.

  10. Motoring Along

    CREDIT: REDWINE ET AL.

    Dyneins are large and complex molecular motors that transport cargo along cellular microtubules and power the movement of cilia. An enigma is how microtubule binding and nucleotide hydrolysis are coordinated between sites separated by 25 nm. Redwine et al. (p. 1532) report an electron microscopy structure of the dynein microtubule-binding domain bound to microtubules in a high-affinity state and combined this with molecular dynamics and existing x-ray structures to provide a model for how dynein couples its affinity for microtubules with the nucleotide-bound state of the motor domain.

  11. Fixing on a Marine Partnership

    Nitrogen fixation by microorganisms determines the productivity of the biosphere. Although plants photosynthesize by virtue of the ancient incorporation of cyanobacteria to form chloroplasts, no equivalent endosymbiotic event has occurred for nitrogen fixation. Nevertheless, in terrestrial environments, nitrogen-fixing symbioses between bacteria and plants, for example, are common. Thompson et al. (p. 1546) noticed that the ubiquitous marine cyanobacterium UCYN-A has an unusually streamlined genome lacking components of the photosynthetic machinery and central carbon metabolism—all suggestive of being an obligate symbiont. By using gentle filtration methods for raw seawater, a tiny eukaryote partner for UCYN-A of less than 3-µm in diameter was discovered. The bacterium sits on the cell wall of this calcifying picoeukaryote, donating fixed nitrogen and receiving fixed carbon in return.

  12. Removing Fear Memories

    Disruption of reconsolidation of an activated fear memory prevents subsequent fear expression. After a memory reminder, extinction training can disrupt fear memory. In rodents, this process is dependent on a brain area called the amygdala. Agren et al. (p. 1550) used functional magnetic resonance imaging and a fear conditioning paradigm to show in humans that, after an associative fear memory was formed, reactivation and reconsolidation left a signature in the basolateral amygdala. This memory trace predicted later fear expression, which was linked to activity in areas forming the fear circuit of the brain. Extinction alone did not change this signal. However, extinction in the reconsolidation window blocked fear expression by erasing the fear memory trace in the amygdala and weakened the connection in the wider fear circuit of the brain.

  13. Recognizing Escaped Commensals

    In order to coexist peacefully, the billions of bacteria in our gut and our immune system have reached a détente. An intestinal mucosal firewall exists, so bacteria remain localized to the gut, where the immune system is tightly regulated so that these bacteria are tolerated. Enteric infections, however, lead to a breach in this mucosal firewall, resulting in exposure of the peripheral immune system to the intestinal bacterial contents. What is the result? Using oral Toxoplasma gondii infection in mice, Hand et al. (p. 1553, published online 23 August) show that, besides the T. gondii–specific T cell response, a commensal bacteria–specific T cell response is elicited. The CD4+ T cell–specific response was tracked to a commensal-derived flagellin, and these T cells expanded after T. gondii infection and formed long-lived memory cells able to respond to subsequent challenges. Thus, enteric infections can lead to the formation of commensal bacteria–specific, long-lived memory T cells that reside throughout the body—which may play a role in intestinal pathologies such as inflammatory bowel disease.

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