This Week in Science

Science  28 Oct 2005:
Vol. 310, Issue 5748, pp. 585
  1. Demystifying Prostate Cancer Genetics


    Many human leukemias display characteristic gene rearrangements, the analysis of which has provided valuable insights into disease mechanisms and stimulated the development of promising therapies such as Gleevec. Gene arrangements also occur in the more common solid tumors, but they are bewilderingly complex and thought to be nonspecific. Tomlins et al. (p. 644; see the news story by Marx) have developed a method that allows them to sort through this cytogenetic complexity and find the gene rearrangements that occur reproducibly in a high percentage of tumors. Using this method, called COPA (for cancer outlier profile analysis), the authors show that the majority of human prostate tumors exhibit chromosomal rearrangements that fuse specific transcription factor genes with the promoter sequences of an androgen-regulated gene, which in turn overexpresses the transcription factor genes in the tumors. These results suggest that COPA may be productively applied to other solid tumors of comparable cytogenetic complexity.

  2. Counting Statistics and Quantum Gases

    Nearly 50 years ago, Hanbury Brown and Twiss showed that photons emitted from a classical thermal light source are correlated, but when the light source was replaced with a coherent one, the correlations disappeared. Their experiment stimulated the birth of modern quantum optics. Schellekens et al. (p. 648, published online 15 September; see the Perspective by Knight) have now observed analogous behavior for ultracold quantum gases and show that atomic correlations vary with the nature of the atom source. For a nondegenerate quantum gas, akin to the thermal optical source, the correlations exist, but when the gas is cooled further to form a coherent ensemble (a Bose-Einstein condensate), the correlations disappear.

  3. Opto-Optical Modulation

    Continued progress in fiber optic communications will rely on the ability to increase the modulation frequency of the optical signal. Present electro-optic modulators typically operate below 100 gigahertz. Carter et al. (p. 651) describe quantum optical effects in a semiconductor quantum-well structure with an optical response at several terahertz. The effects are analogous to those seen in atomic and molecular three-level systems where a pump beam induces coherent oscillations between the two lower levels and creates electromagnetic-induced transparency for a probe beam when it is resonant with one of the lower-level to upper-level transitions. Full optical control over the modulation process should allow communications to operate at much higher frequencies.

  4. Magmatic Activity Maintained


    A simple view of oceanic crust formation is that magma rises at spreading ridges and cools as it moves away. During cooling, magnetic minerals preserve the orientation of Earth's magnetic field and create symmetric patterns of magnetic stripes across the ocean floor. Evaluating this simple process has been difficult, however, because most oceanic crust lacks the mineral zircon, which contains sufficient uranium for the most accurate determination of the ages of crystallization of magmas. Schwartz et al. (p. 654) have now identified and separated zircons from oceanic crust formed along the Southwest India Ridge, a ridge that is spreading slowly. Significant magmatic activity began in each segment of crust long before most of the magmatism and the characteristic magnetic signature were locked in.

  5. Ground Truth About Arctic Warming

    Although radiative forcing by greenhouse gases will likely have the most significant influence on the amount of surface warming that Earth will experience in the near future, other processes can be just as or even more important in particular regions. Chapin et al. (p. 657, published online 22 September; see the Perspective by Foley) analyzed field data from arctic Alaska that show how changes in summer albedo contribute to warming trends there. These reflectivity effects, now mostly caused by longer snow-free seasons but increasingly by expansion of shrub ranges in the future, are as large in magnitude as those caused by the buildup of greenhouse gases. These changes have the potential to amplify surface temperature increases by factors of two to seven.

  6. Microscopy of Melting Metal

    The nature of the solid-liquid interface is key for understanding processes such as liquid-phase epitaxial growth, wetting, liquid-phase joining, crystal growth, and lubrication. For metals, studying this interface in detail can be difficult because of the elevated temperatures at which melting occurs. Using an advanced high-resolution transmission electron microscope, Oh et al. (p. 661, published online 6 October) studied the wetting of aluminum sitting on a substrate of alumina and observed crystalline ordering of the liquid atoms adjacent to the ordered solid. The growth of the alumina was facilitated by the interfacial transport of oxygen from the microscope column along the solid-liquid interface.

  7. Inhibiting Bacterial Virulence and Cholera Susceptibility

    Bacterial virulence gene products have been neglected as targets for drug discovery because inactivation of virulence has not produced bacteriocidal or growth inhibitory effects. Hung et al. (p. 670, published online 13 October) screened a chemical library for molecules that block expression of the cholera toxin gene (ctxA) and identified an inhibitor of virulence gene regulation in Vibrio cholera. The compound, termed virstatin, affects the activity of a transcription factor, ToxT, the ctxA activator. ToxT activity is inhibited by virstatin in both V. cholera and Escherichia coli. As expected, virstatin did not affect growth of the bacteria, but nevertheless had a dramatic effect on the intestinal colonization of V. cholera in mice.

  8. Just the Right Size

    Two parameters control the eventual size of insects: their growth rate and the length of their growth period. Ecdysone, a major steroid hormone, functions as a developmental timer that controls the length of the growth period. Colombani et al. (p. 667; see the Perspective by King-Jones and Thummel) now show that ecdysone from the prothoracic gland of Drosophila also regulates the speed at which the animals grow by inhibiting insulin/insulin-like growth factor signaling. This work provides a conceptual framework for understanding how the final size of an organism is determined and establishes a link between steroid hormone and insulin signaling.

  9. The Tip of the Needle

    The type III secretion apparatus helps transfer proteins from the bacterial cytoplasm into that of a target eukaryotic host cell and includes a well-characterized needle-like structure. The needle tip has not been characterized and represents a critical player in bacteria-cell interaction. Mueller et al. (p. 674) now present evidence that the needle of the Yersinia type III secretion apparatus is topped with a distinct structure, made of a critical protective antigenic protein, LcrV, one of the “translocators” involved in protein transfer.

  10. Appetite and the Adaptive Brain


    Appetite and energy balance are regulated by the hypothalamic region of the brain, and considerable progress has been made in defining the underlying neural circuitry. Two studies underscore the emerging idea that these feeding circuits are not firmly “hardwired” but rather exhibit remarkable plasticity, even in adults. Luquet et al. (p. 683) show that specific neurons that are strictly required for the regulation of food intake in adult mice can be removed without detriment in newborn mice, which suggests that the feeding circuitry can readily adapt to change early in life. Kokoeva et al. (p. 679; see the news story by Vogel) make the surprising observation that a neurotrophic factor that induces sustained weight loss in adult mice does so by stimulating the proliferation of hypothalamic neurons. Pharmacological inhibition of this neurogenesis compromised the capacity of the neurotrophic factor to induce long-term weight loss. Hypothalamic plasticity thus adds another potentially important layer of complexity to the regulation of body weight.

  11. Bats Again

    Attempts to identify the wildlife hosts of emerging diseases have relied on analysis of fecal material from wildlife, trade, and domesticated animals that reveal recent infections circulating in the markets. Li et al. (p. 676, published online 29 September; see the 30 September news story by Normile and the Perspective by Dobson) have targeted their investigations on wild bats in China and discovered several genetically diverse coronaviruses, one of which closely resembles the severe acute respiratory syndrome (SARS) coronavirus. These findings implicate bats as the wild reservoir of this virus.

  12. Sequence Sets Structure

    Since 1973, when Anfinsen determined that the amino acid sequence of a protein defines its three-dimensional structure, the challenge has been to predict protein folds by determining the lowest energy conformation for a particular sequence. The solution to this problem requires not only quantitative models of the energetics of macromolecular interaction but also methods for searching enormous conformational spaces. In their review, Schueler-Furman et al. (p. 638) suggest that high-resolution prediction and design is reaching a stage where it can make important contributions to biology and medicine.

  13. Who Regulates the Regulators?

    In plants, the shoot apical meristem is a group of stem cells at the shoot tip that generate the various differentiated tissues of the vegetative aboveground plant. Reddy and Meyerowitz (p. 663, published online 6 October; see the cover) have analyzed how the meristem in Arabidopsis is maintained at a particular size, despite cells being continually diverted to differentiation pathways. The results indicate that the CLAVATA3 gene product and its resultant signaling network control the number of cells in the meristem, both by effects on cell proliferation and on cellular fates during differentiation.