Welcome to the latest issue of Science Roundup!

PLEASE NOTE: There are links throughout Science Roundup to articles on Science Online (http://www.scienceonline.org). You must be a subscriber to Science Online to read the full text of the articles. Abstracts, however, are available free of charge.

----
First, a very quick word from our sponsor:

Invitrogen provides Life Science Researchers worldwide with essential tools designed to save time, save effort, and produce more reliable results. A few of the innovative technologies now available are discussed below.
----

SCIENCE ROUNDUP
Contents of this Issue:

Unthinkable Crimes
The Blossoming of Epigenetics
Time to Rewrite the Textbooks
A Decision on Stem Cells
Flu’s Clues
Visualizing Microarrays
Batten Down the Hatches?
Digging into Seismicity in Central Europe
Taking the Long View on Ecology
All in the Family
Dino Makeover
Vibration Predation
Threatened Treasures
Brain Researchers Unite!
Superconductivity Heats Up
Toward New Energy Sources
How the Brain Makes Faces
Tool for the 21stCentury


During the third quarter of 2001, Science provided the stage for dramatic reporting both of cutting-edge scientific research and of events at the intersection of science and global society. Here’s a review of some of the more notable stories.


Unthinkable Crimes
http://www.sciencemag.org/cgi/content/summary/293/5538/2182a

In the wake of the terrorist attacks of 11 September, the magnitude of the crime initially seemed beyond comprehension. Yet the attacks, wrenching as they were for the U.S. and the world, inevitably brought to mind the still greater horrors that might ensue if terrorist groups were to use weapons of mass destruction. A news article in the 21 Sep 2001 issue of Science reviewed the state of U.S. and international antiterrorist programs, and explored the plausibility of terrorist threats related to mass destruction’s “unholy trinity” -- nuclear, chemical, and biological weapons. Bioweapons formed the focus of a timely editorial in the following week by C. F. Chyba (http://www.sciencemag.org/cgi/content/summary/293/5539/2349), titled “Biological Security in a Changing World.”


The Blossoming of Epigenetics
http://www.sciencemag.org/content/vol293/issue5532/index.shtml#specialintro

The depression among some researchers upon learning that humans have only around 50% more genes than the common laboratory roundworm is being lifted by a flurry of new work in understanding the complex epigenetic regulation of our genome -- a topic reviewed in Science’s 10 Aug 2001 special issue. Review and Viewpoint articles covered DNA methylation in mammals and other organisms, histone modifications, and the known epigenetic phenomena of X-chromosome dosage compensation, imprinting, and centromere function. Reports in the same issue by Lo et al. (http://www.sciencemag.org/cgi/content/short/293/5532/1142) and Noma et al. (http://www.sciencemag.org/cgi/content/short/293/5532/1150) described new findings in regulation of histone modifications, which has emerged as one of the primary mechanisms for control of gene expression. And an accompanying feature on the Science Functional Genomics Web site (http://www.sciencegenomics.org/resources/res_epigenetics.shtml) offered links to a collection of online epigenetics resources, and an archive of articles and reviews published in Science over the past several years.

One key arena for epigenetic study lies in exploring the feasibility of cloning organisms by nuclear transfer. In a landmark report in the 6 Jul 01 issue, Humpherys et al. (http://www.sciencemag.org/cgi/content/short/293/5527/95) examined imprinted gene expression in cloned mice and in the embryonic stem cells from which the mice were derived. The epigenetic state of the stem cells turned out to be highly unstable, which resulted in variation in imprinted gene expression in the derived mice. These results could help explain many abnormalities found in cloned organisms -- and may also serve to dampen enthusiasm for human cloning, which would require exquisite control over the genome’s epigenetic state. As Rideout et al. pointed out in their review of the topic in the epigenetics special issue (http://www.sciencemag.org/cgi/content/short/293/5532/1093),
“even apparently healthy cloned animals may have subtle gene expression abnormalities that were not severe enough to cause lethality or an obvious postnatal phenotype” -- but that may become tragically apparent later on.


Time to Rewrite the Textbooks

Everyone is taught that, in eukaryotic cells, transcription of DNA into RNA occurs only in the nucleus and translation of RNA into protein occurs only in the cytoplasm. Apparently, everyone has been mistaken. In the 10 Aug 2001 Science, Iborra et al. (http://www.sciencemag.org/cgi/content/short/293/5532/1139) offered the most convincing evidence yet that some proteins -- an estimated 10 to 15% -- are made inside the nucleus. To visualize new protein translation, the researchers exposed cells to molecules of the amino acid lysine that were tagged with fluorescent or radioactive markers. They observed similar incorporation of the tagged molecules into new proteins both in the cytoplasm and, surprisingly, at pinpoint sites in the nucleus. What’s more, the nuclear accumulation was time dependent, and was slowed by chemicals known to inhibit protein synthesis in eukaryotic cells -- clear indicators that translation was taking place in the nucleus. Purified nuclei that had been removed from the cell also showed the ability to fashion proteins, a confirmation that the nucleus wasn’t simply importing proteins from the cytoplasm. As M. W. Hentze noted in an accompanying Perspective (http://www.sciencemag.org/cgi/content/short/293/5532/1058), the work opens up entirely new avenues of study on how proteins are constructed in the cell -- and “future research on translation, whether in the nucleus or the cytoplasm, is likely to be full of suspense and surprises.”


A Decision on Stem Cells

On August 9, George W. Bush, in his first televised address as President, announced that he would allow the federal government to fund research on human embryonic stem cells. Science provided full coverage and analysis of the announcement in a 17 Aug 2001 News Focus (http://www.sciencemag.org/cgi/content/short/293/5533/1242). The feature covered both the announcement and its immediate aftermath -- especially concern among scientists regarding the originally reported 64 stem cell lines worldwide. Also included: a full transcript of Bush's address (http://www.sciencemag.org/cgi/content/short/293/5533/1244) and a profile of the administration’s newly appointed bioethics point man, Leon Kass (http://www.sciencemag.org/cgi/content/short/293/5533/1243).

As impressive as their theoretical potential to differentiate into any human cell is, key issues such as how stem cells actually form, what roles they play in the body, and what limitations, if any, there are to their ability to migrate remain largely obscure. A study by Ourednik et al. (http://www.sciencemag.org/cgi/content/short/293/5536/1820) published in the 7 Sep 2001 issue cast some light on all three questions. A traceable clone of human neural stem cells was implanted in developing primate forebrains to study the cells’ differentiability and migratory patterns. The researchers found that the cells divided into two separate subpopulations -- one dedicated to producing differentiated cells and the other set aside in a secondary “reservoir.” Yet both subpopulations had the ability to migrate through the large expanse of the primate cerebrum, suggesting that stem cell transplants could someday be successful in brains larger than those of rodents.


Flu's Clues

The virulence of different strains of the influenza virus, one of humankind’s most enduring pathogenic enemies, constitutes a fascinating and controversial puzzle. A pair of studies in the 7 Sep 2001 issue put together some of the pieces using the tools of comparative genomics and molecular biology. Hatta et al. (http://www.sciencemag.org/cgi/content/short/293/5536/1840) examined the H5N1 influenza A virus -- the “Hong Kong” flu that was fatally transmitted from birds to humans in 1997. Comparing that lethal virus to a close but nonlethal relative suggested that substitutions of two amino acids in the viral genome principally determined the variation in virulence between the two strains.
Digging further into the past, Gibbs et al. (http://www.sciencemag.org/cgi/content/short/293/5536/1842) constructed a molecular history of the H1 influenza hemagglutinin gene, the principal antigen on the surface of the virus capsule. They concluded that the 1918 “Spanish flu” pandemic, the most deadly ever for humans, resulted from a virus with a rare recombination event in its hemagglutinin gene -- although an accompanying Perspective by R. G. Webster (http://www.sciencemag.org/cgi/content/short/293/5536/1773) suggested that the proposed rearrangement was “definitely a stretch for influenza virologists” in view of the extreme rarity of such recombination events. Those differences notwithstanding, an Editorial in the same issue (http://www.sciencemag.org/cgi/content/short/293/5536/1729) pleaded for building up stockpiles of antiviral drugs to combat the next influenza pandemic -- for, as noted in a second, sobering Perspective by Laver and Garman (http://www.sciencemag.org/cgi/content/short/293/5536/1776), a “worldwide epidemic (pandemic) of type A influenza could occur at any time.”


Visualizing Microarrays

The increasing popularity of microarray studies as a way to examine gene expression carries its own quandary: How do you view and analyze the huge volumes of data churned out by each experiment? In the 14 Sep 2001 issue, Kim et al. (http://www.sciencemag.org/cgi/content/short/293/5537/2087) borrowed an answer from geology -- make a topo map. The group compiled data from 553 gene expression microarray experiments on C. elegans, and presented an innovative three-dimensional “terrain map” to view the data -- each “mountain” representing a gene expression cluster, revealing relationships between genes that may not have been seen when testing specific hypotheses. “Fly-over” movies of several of these gene-expression terrains are available as supplemental material on Science Online. In the same issue, Zhu et al. (http://www.sciencemag.org/cgi/content/short/293/5537/2101) reported a different milestone in array studies: the creation of a nearly complete microarray of the entire proteome of the laboratory yeast S. cerevisiae on a single microscope slide.


Batten Down the Hatches?

As residents of the U.S. East and Gulf Coasts well know, the number of Atlantic hurricanes has been above average in recent years. In a report published on 20 Jul 2001, Goldenberg et al. (http://www.sciencemag.org/cgi/content/short/293/5529/475) suggested just how much: Charting the variability of hurricane activity since the mid-20th century, the study noted a 2.5-fold increase in hurricane activity for the past six years relative to the preceding quarter-century. And that increase, they suggest, isn’t just a temporary fluke, but instead traces to a combination of increased North Atlantic sea-surface temperatures and vertical wind shear that’s likely to persist for another 10 to 40 years. In a Perspective (http://www.sciencemag.org/cgi/content/short/293/5529/440), however, L. Bengtsson disagreed, arguing that meteorological records are “too short and too incomplete” to allow such a conclusion. Either way, all agreed that the U.S. coastal population boom during the previous lull in hurricane activity has greatly increased the possible damage costs from any single hurricane.


Digging into Seismicity in Central Europe

The Rhine graben is a lengthy rift valley, bounded by active extensional faults, that runs north-south through much of Germany and Switzerland. The faults are known to have failed in catastrophic earthquakes in the past -- the largest being a magnitude 6.5 event that struck the area of Basel, Switzerland, in 1356. But earthquake-linked faults in the region have been notoriously difficult to study in detail owing to the infrequency of such events. Meghraoui et al. (http://www.sciencemag.org/cgi/content/short/293/5537/2070), reporting in the 14 Sep 2001 issue, applied the techniques of paleoseismology to finger the fault responsible for the 1356 quake. Using remote sensing to narrow down the list of candidate structures, they zeroed in on a 50-meter-high fault scarp south of Basel as a promising candidate; then, they explored the fault’s history by digging trenches into the base of the fault. The trenching revealed sedimentary layers that had been substantially separated along the fault’s trace -- and radiocarbon dating suggested that displacement along the fault amounted to nearly 2 meters, in not one but three major seismic events over the past 8500 years. Although the data imply a relatively long “recurrence interval” for the fault in question (on the order of 1500 to 2500 years), the study offered a sobering new glimpse at the seismic hazards in central Europe -- an area dotted with vulnerable “critical facilities” such as chemical and nuclear plants.


Taking the Long View on Ecology
http://www.sciencemag.org/content/vol293/issue5530/index.shtml#specialintro

Although systematic recordkeeping has been introduced and implemented only in the past century, ecologists have increasingly come to appreciate that gleaning long-term trends -- both over history’s long haul and in modern experiments spanning decades rather than years -- is an important step for understanding current conditions and predicting the future of complex ecosystems. The 27 Jul 2001 special issue of Science chronicled some recent efforts to piece together how ecosystems work over long time scales. An extensive news article by Jocelyn Kaiser examined the granddaddy of all ecology-through-time projects, the NSF-funded Long Term Ecological Research (LTER) network, a program whose big-science approach to ecology has paid off with some impressive successes. Review articles explored a variety of areas in which a long-term perspective is essential, such as reconstructing ancient coastal ecosystems through historical records and studying variations in plant and population dynamics over time. And a Viewpoint article turned the focus to the future: the “emerging imperative” of accurate ecological forecasting, and how long-term studies can aid in such efforts. An online supplement (http://www.sciencemag.org/feature/data/ecology2001.shtml) offered links to general ecological resources, LTER programs in the U.S. and abroad, resources on population ecology and ecological forecasting, and more.


All in the Family

“I seem to have misplaced an elephant” is not a phrase one hears often -- but that’s just what Roca et al. argue that scientists have been doing for more than 100 years, in a 24 Aug 2001 report (http://www.sciencemag.org/cgi/content/abstract/293/5534/1473). The group described variations in the DNA sequence of four nuclear genes gathered from dart-biopsy samples of 195 free-ranging African elephants within the species Loxodonta africana -- variations substantial enough to suggest that two groups of the elephants have evolutionarily diverged. Result: The addition of a second species of African elephant, dubbed L. cyclotis. That’s not all that has been evolving in the pages of Science over the last quarter. In the 21 Sep 2001 issue (http://www.sciencemag.org/cgi/content/short/293/5538/2239), Gingerich et al. described the discovery of skeletons of two primitive whales with well-developed limbs. These findings may be an important “missing link” in whale evolution, as they lend credence to the claim that whales are not just related to, but descended from, artiodactyls -- the group that includes even-toed, hoofed mammals.


Dino Makeover

Watching dinosaurs stalk across the silver screen, it’s easy to forget that what we know about them comes from interpretation of fossils -- and that recreating nonfossilized structures, such as skin and muscle, can be a very difficult task. In a study published in the 3 Aug 2001 issue (http://www.sciencemag.org/cgi/content/short/293/5531/850), Witmer rose to the challenge in grand style. By studying the position, in closely related species such as birds and crocodiles, of the small nasal aperture of the skin with respect to the larger underlying nasal bone cavity, and comparing fine structures on the bones of the extinct reptiles with those of living relatives, Witmer deduced that the fleshy part of the dinosaurs’ nostrils were likely located in front of the nasal cavity, out toward the front of the dinosaur’s snout, rather than high and back as commonly portrayed. As is noted in the accompanying news article by Eric Stokstad (http://www.sciencemag.org/cgi/content/short/293/5531/779a), the difference isn’t just aesthetic -- an up-front nasal opening could mean both enhanced airflow and a better sense of smell and taste for the animals.


Vibration Predation

Sea water is often dark or cloudy, and harbor seals haven't evolved the echolocation employed by other sea mammals. How do they track their prey over a distance? Dehnhardt et al. (http://www.sciencemag.org/cgi/content/short/5527/102) provided an answer in the 6 Jul 2001 Science: In stylishly simple experiments, the group established that the seals use their whiskers to detect hydrodynamic trails left by the moving prey. Dehnhardt et al. trained seals to track small, propeller-driven submarines, and showed that, when tracking the sub, the seals followed a curved trail taken by the submarine rather than making a straight line for the sub’s current position. Only when their whiskers were masked were they unable to track the sub. Normally, seals’ whiskers are extremely sensitive, and vibrate at characteristic frequencies based on swim speed and other factors. Dehnhardt et al. speculated that the vortices left in the wake behind prey, which can persist for more than three minutes, change the whiskers’ vibration frequency, signaling that dinner is nearby.


Threatened Treasures
http://www.sciencemag.org/content/vol293/issue5527/index.shtml#newsfocus

As the “cradle of civilization,” ancient Mesopotamia was home to some of the earliest human societies; today, the same lands, located in modern-day Iraq, are home to some of the most sought-after archeological treasures known. But the political turmoil of the area has raised severe threats for archeology in the once great Fertile Crescent. A ten-page news focus in the 6 Jul 2001 issue of Science surveyed the past, present, and future of archeology in Iraq, with articles focusing on the immediate dangers to artifacts in the country, looting networks at work in the desert, the efforts of archeologists determined to stop the destruction, and new excavations that could help revitalize study of the greatness that was Mesopotamia.


Brain Researchers Unite!

This quarter in Science was remarkable for articles that linked previously disparate areas of research on two devastating neurological diseases:

--Shimura et al (13 Jul 2001; http://www.sciencemag.org/cgi/content/short/293/5528/263) connected two areas of research into Parkinson's disease (PD) that had been proceeding along separate tracks. It has been known for several years that families with one inherited form of PD carried a mutation in the PARKIN gene, which codes for the E3 ubiquitin ligase parkin, and that victims of another familial PD variant showed missense mutations in the gene encoding the alpha-synuclein protein. Shimura et al. closed the loop, reporting that parkin is in fact the ligase that adds ubiquitin groups to a form of alpha-synuclein -- and thereby, in the words of an accompanying Perspective by C. Haass and P. J. Kahle, “targets that protein for destruction in the cell's garbage dump, the proteasome.” The paper, note the Perspective authors, offers “provocative evidence” to reconcile variations in brain pathology between two forms of PD to different problems in a common pathway.

--In the 24 Aug 2001 issue, two groups working independently on Alzheimer's disease (AD) -- Lewis et al. (http://www.sciencemag.org/cgi/content/short/293/5534/1487) and Gotz et al. (http://www.sciencemag.org/cgi/content/short/293/5534/1491) -- demonstrated that amyloid-beta protein interacts with tau protein to increase the formation of neurofibrillary tangles in the mouse brain. As noted in a related Perspective by V. M.-Y. Lee (http://www.sciencemag.org/cgi/content/short/293/5534/1446), the two studies together provide the first compelling evidence that “a causal connection” links the two dominant pathologies of Alzheimer’s, amyloid plaques and tau tangles.


Superconductivity Heats Up

The dream of “killer apps” for superconductivity, such as large superconducting cables, has long been stymied by a nagging fact: The “critical temperature” of most superconducting materials (the temperature below which the materials actually do superconduct) tends to be extremely cold -- on the order of tens of Kelvins. The discovery fifteen years ago of higher-temperature superconducting behavior in copper-oxide planes (the so-called planar cuprates) spurred excitement and a huge amount of subsequent work, but thus far, even for these promising materials, the record critical temperature of 133 K, reached eight years ago, still has not been surpassed. Now two papers by Schoen et al., in the 28 Sep 2001 issue of Science, have opened up a different road toward high-temperature superconductivity -- one paved in fullerene. The group found that these remarkable spherical molecules of sixty carbon atoms (also known by the nickname “buckyballs”) can, using a method called field-effect doping, have their superconducting temperature tweaked up from 52 K to a comparatively balmy 117 K. As noted in an accompanying Perspective by E. Dagotto (http://www.sciencemag.org/cgi/content/short/293/5539/2410), it seems likely that, using the techniques and materials of the Schoen et al. studies, researchers will easily break the current critical-temperature record of 133 K -- and that the studies could spur a renewed “race toward room-temperature superconductivity.”


Toward New Energy Sources

Extracting cheap, efficient power from the sun is the holy grail of renewable energy. But although solar cells made of organic materials have the potential to be substantially cheaper than current, dominantly inorganic photovoltaics, it’s been tough to achieve high enough efficiencies to make organic devices commercially worthwhile. In the 10 Aug 2001 issue of Science, Schmidt-Mende et al. (http://www.sciencemag.org/cgi/content/short/293/5532/1119) took a big step in the direction of practical, efficient organic photovoltaics. By exploiting the self-organizing properties of liquid crystals, the group was able to combine two organic compounds in a photovoltaic device that achieved nanoscale separation between electron-accepting and electron “hole”-accepting parts of the cell. Result: A easy-to-fabricate cell with a highly efficient separation of charge carriers -- and a “quantum efficiency” well above that of most organic photovoltaics. An accompanying Perspective by J. Nelson (http://www.sciencemag.org/cgi/content/short/293/5532/1059) provided a gloss on this elegant work, and placed it in the context of other solar-cell studies.

Another possible route to efficient solar energy is harnessing the sun’s photons to dissociate molecular hydrogen from water or other hydrogen-containing solvents, and using the harvested hydrogen in a fuel cell. The trick for such a scheme lies in fashioning a small-molecule catalyst to repeatedly act as midwife to the hydrogen-liberating reaction. In the 31 Aug 2001 issue, Heyduk and Nocera (http://www.sciencemag.org/cgi/content/short/293/5535/1639) showed that they could photogenerate molecular hydrogen from pure hydrohalic acids, such as condensed HCl, using a cleverly designed dirhodium catalyst. Although it’s not exactly “hydrogen from water,” and although the system needs improvement, as noted in a Perspective by J. K. McCusker (http://www.sciencemag.org/cgi/content/short/293/5535/1599), the work does clear an important hurdle on the path toward sustainable hydrogen-driven energy.


How the Brain Makes Faces

For years, neuroscientists have debated the question: Does the brain organize information of different types, such as human faces, in discrete physical areas, or modules, devoted to that kind of data? Or can a given class of information be processed in many different brain areas, each capable of handling numerous data types? A pair of articles in the 28 Sep 2001 Science, both using the neuroimaging technique known as functional magnetic resonance imaging (fMRI), arrived at strikingly divergent answers to the question. Haxby et al. (http://www.sciencemag.org/cgi/content/short/293/5539/2425) found that categories of objects such as faces, bottles, and cats each evoked a unique brain response that was distributed among different areas across a large region of ventral extrastriate cortex. In a separate study, however, Downing et al. (http://www.sciencemag.org/cgi/content/short/293/5539/2470) provided compelling evidence for the modular view: pictures of the human body -- whether photos, line drawings, silhouettes, or stick figures -- drew a strong response from a highly circumscribed zone of the lateral occipital cortex. Reconciling these apparently contrasting views poses a challenge for the field, as is discussed in a Perspective by J. D. Cohen and F. Tong (http://www.sciencemag.org/cgi/content/short/293/5539/2405).


Tool for the 21st Century
http://www.sciencemag.org/content/vol293/issue5537/index.shtml#specialintro

Over the past 50 years, no machine has done more to shape the way people work -- especially in science -- than the computer. But where is scientific computing headed? Science suggested some answers in a special issue on 14 Sep 2001. News articles covered the increased R&D effort at semiconductor giant Intel, the need for improved “science only” search engines (and how some researchers and companies are meeting that need), and developments in that most speculative realm of computer science, quantum computing, which also formed the subject of a Viewpoint article in the issue. Other Viewpoints discussed applications of computer science in visualizing complex life-science data sets and signaling pathways; the “invisible barrier” of inherent physical limitations facing silicon-based circuitry; machine learning; and social themes, including the potentially troubling impact of the Digital Millennium Copyright Act on scientific openness and communication. An online supplement (http://www.sciencemag.org/feature/data/compsci/index.shtml) offered links to additional Web resources on computer science.

----
A final word from our sponsor:

Over the past ten years Invitrogen has introduced platform technologies that revolutionized the way experiments are performed – making them faster, easier, and more efficient. These ground-breaking tools include:

* TOPO® Cloning – five-minute, bench-top ligation of PCR products and other DNA molecules with >90% recombinants

* Gateway™ Technology – a rapid and highly efficient route to protein expression and functional analysis across multiple systems

* NuPAGE® Novex Pre-cast Gels – polyacrylamide gels with a 12-month shelf life for high-performance protein separation

* TOPO® Tools – a flexible, fast, and completely customizable method to build linear constructs for use in a wide range of applications

* AccuPrime™ Taq DNA Polymerase – accurate performance and unmatched specificity in PCR

* Advanced expression systems – a large selection of vectors and systems for protein expression and analysis in E. coli, yeast, insect and mammalian cells

* ResGen™ GeneFilters® microarrays – ready-to-use microarrays for cost-effective, simple, and rapid analysis of thousands of genes

For more information on these technologies or other cutting-edge products available to enhance your research, visit http://www.invitrogen.com

----
You are listed in the AAAS database as memuser@aaas.org.
If you do not wish to receive e-mail messages from AAAS in the future, please reply to this message with "UNSUBSCRIBE" in the subject line and your e-mail address in the body and we will remove your name from the list promptly.
PLEASE NOTE: This will UNSUBSCRIBE you from ALL further email announcements from AAAS, including announcements of new member benefits, discounts, or meetings of interest.