This Week in Science

Science  17 Jun 2005:
Vol. 308, Issue 5729, pp. 1709
  1. Tubulin-Modifying Enzymes Identified


    Polyglutamylation of tubulin has been implicated in several functions of microtubules. Janke et al. (p. 1758, published online 12 May 2005) present evidence that the neuronal tubulin polyglutamylase is a protein complex containing a conserved tubulin tyrosine ligase-like (TTLL) protein, TTLL1. The unicellular, ciliated freshwater protozoan Tetrahymena thermophila has at least two conserved types of TTLLs that act as polyglutamylases. The polyglutamylases differ in substrate preference and subcellular localization and contribute in Tetrahymena to ciliary motility and cell division.

  2. Freshening Up Slowly

    The strength of large-scale ocean thermohaline circulation depends in part on the saltiness of the waters of the North Atlantic Ocean. The salinity of the upper waters there has been decreasing during the past 30 or more years, but how much fresh water must have been added to produce those changes has been unclear. Curry and Mauritzen (p. 1772) reconstruct the history of the ocean temperature, salinity, and density of the Nordic Seas and Subpolar Basins for last 50 years in order to determine what must have been the fresh water inputs there. Although the fluxes that they calculate are high, they do not appear to be great enough to slow or shut down thermohaline circulation within the next century or two.

  3. Nanowires and SQUIDs

    Using molecules as templates onto which metal wires can be deposited is opening up opportunities for self-assembled circuitry and the formation of devices. Hopkins et al. (p. 1762) used two strands of DNA stretched across a trench as a template to deposit two finely coupled superconducting nanowires. Although the structure superficially resembles a superconducting quantum interference device (SQUID), and the resistance oscillates as a function of magnetic field, close inspection of the magnetotransport behavior suggests somewhat different behavior from that of standard mesoscopic superconducting devices.

  4. Beyond H3O+


    Despite the ease with which we can now measure pH, a molecular picture of aqueous protons remains elusive, and recent studies have shown that the standard H3O+ structure is more of a shorthand than an accurate description of bonding. Headrick et al. (p. 1765) used infrared spectroscopy to probe the structure from the bottom up, starting with a proton shared between just two water molecules. They then watched the bonding structure change as one to nine additional water molecules were added. Enlarging the solvation shell varied the dominance of structures in which the proton is bound to one water molecule (H3O+) or shared equally between two (H2OHOH2+). These results suggest that coordination in the bulk may fluctuate between these extremes.

  5. A Long-Lived Earthquake

    The 26 December 2004 Sumatra-Andaman earthquake produced noticeable deformation over most of Earth. Banerjee et al. (p. 1769 published online 19 May 2005) used global positioning satellite measurements from both far from and near to the earthquake to provide an estimate of how the rupture progressed and the amount of energy it released. Stations to the east of the rupture moved to the west, and vice versa, consistent with the quake's thrust motion. The inversion implies that significant energy was released even after 1 hour after the quake.

  6. Clearing Up Glass

    Glass artifacts can be found in Mesopotamia and Egypt that date from 1000 to 1500 B.C. The primary source of the glass, before its later reworking by craftsmen, has been uncertain, although most arguments have favored Mesopotamia. Rehren and Pusch (p. 1756; see the Perspective by Jackson) now describe glass-coated ceramic vessels and slag discovered in site in the eastern Nile Delta in Egypt dating to about 1250 B.C. The nature of the material implies that it was fired to nearly 1000C and is consistent with this site being a major center of primary glass production.

  7. Patient-Specific Embryonic Stem Cells Become a Reality

    The generation of pluripotent patient-specific cell lines is a first step toward specifically tailored cellular therapies. Hwang et al. (p. 1777; published online 19 May 2005; see the 20 May news story by Vogel) have isolated embryonic stem cell lines via an improved somatic cell nuclear transfer method. These cell lines match the nuclear DNA and show in vitro immunological compatibility with cells from the original somatic nucleus donor patients. However, these patient-specific cells could only be used for preclinical analyses until the remaining animal components introduced during culture are removed and until reliable methods provide efficient, directed differentiation of stable cells of whichever cell type may be needed for therapeutic transplantation. In a related Policy Forum, Magnus and Cho (p. 1747; published online 19 May 2005) discuss the ethical issues raised by nonclinical oocyte donation.

  8. Home Sweet Home

    Leguminous plants fix atmospheric nitrogen with the aid of symbiotic rhizobial bacteria. When rhizobia infect the root, a complex developmental program is initiated to form the nodules that house the symbiotic bacteria (see the Perspective by Udvardi and Scheible). Smit et al. (p. 1789) and Kaló et al. (p. 1786) identify key elements in the signaling cascade by which the bacteria signal their presence to the host plants. The constitutively expressed plant proteins NSP1 and NSP2 are likely transcription factors poised to respond early to the bacterial nodulation factor signal. It appears that NSP1 and NSP2 respond to the initial nodulation factorinduced calcium signal to generate changes in gene transcription.

  9. Indirect Defenses


    Some plants defend against fungal infection by using the hypersensitive response, in which plant cells at the site of invasion are killed off to retard spread of the infection. The process relies upon an elicitor from the pathogen and a corresponding resistance gene in the plant. When Cladosporium fulvum infects tomato leaves, these two factors do not, however, seem to interact directly. Rooney et al. (p. 1783, published online 21 April 2005) analyze the function of the plant protease Rcr3 in mediating the defense response. The pathogen avirulence factor, Avr, is secreted extracellularly, where it interacts with the tomato plant Rcr3 protease. Together, this interaction signals to the membrane-bound host resistance factor, Cf-2, to initiate plant defense responses.

  10. Of Mice and Men

    Differences between the left and right hemispheres of the brain mean that each side is somewhat specialized, the right being more “artistic” and the left being more “mathematical.” These differences are laid down early in development, and the skills associated with each side honed as we mature. Sun et al. (p. 1794, published online 12 May 2005) have now analyzed gene expression in the early developing human brain and identified a number of genes that are asymmetrically expressed. In-depth analysis of one of the genes, LMO4, and comparison of how the related gene is expressed in developing mouse brains, indicates that human brains consistently attain a similar left-right asymmetry, whereas in the mouse the asymmetry is established randomly.

  11. The Neural Signature of Disappointment

    Neurons in several brain structures respond to dopamine in a way that is positively correlated with the difference between reward magnitude and reward expectation. However, what happens when our expectations are frustrated, as often happens in real life? Minamimoto et al. (p. 1798) observed a reward-related signal in the centromedian nucleus of the thalamus that is correlated with the expectation or delivery of a small reward. This signal seems to be specifically related to disappointment or unhappiness. Electrical stimulation of this nucleus specifically disrupted behavior in a task with differential reward structure. Thus, the feeling of disappointment interferes with the execution of a straightforward behavioral process.

  12. TRP'ing Up the Kidney

    In focal and segmental glomerulosclerosis (FSGS), scarring or hardening of the tiny blood vessels within the kidney leads to leakage of protein into the urine. FSGS is a significant cause of end-stage renal disease, and its prevalence is increasing. Disruption of cytoskeletal and structural proteins are known to play a role in pathogenesis. Now, Winn et al. (p. 1801, published online 5 May 2005) describe an alternative route to the disease. Studying a large family with a hereditary form of FSGS, they find that the causative mutation occurs in the gene encoding transient receptor potential cation channel 6 (TRPC6), a protein believed to mediate calcium entry into cells. Because channels are often amenable to pharmacological manipulation, this study raises the possibility that TRPC6 may be a useful therapeutic target in chronic kidney disease.

  13. Accidental Attacks

    The drilling seen into brachiopods throughout nearly all of their fossil record has typically been attributed to persistent predation. Kowalewski et al. (p. 1774) show that the evolutionary story is much more nuanced. Studying ancient and modern brachiopods, as well as literature reports, they show that predation, as marked by drilling, always remained low, but increased just slightly from the early Paleozoic. Furthermore, the relatively few drill holes varied greatly in size. These data imply that brachiopods were—and are—attacked only rarely, perhaps by mistake, and were not in an evolutionary arms race. The slight increase with time is consistent with an overall increase in marine predators brought about by coevolution with other species.

  14. Cortical Input to the Hippocampus

    The main inputs to the hippocampus are still not fully understood. Hargreaves et al. (p. 1792) suggest that spatial and nonspatial information reaches the hippocampus by different routes through the entorhinal cortex, which exhibits a medial-lateral functional division. Spike activity was recorded with electrodes from rats that ran for food in a square enclosure. Neurons in the medial entorhinal cortex had highly specific firing fields that were slightly more dispersed than those of place cells in the hippocampus. However, cells in the lateral entorhinal cortex showed little if any spatial modulation.

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