Health and Medicine: New genetic brain atlas (pp917-925; N&V)
Researchers are compiling a new atlas of the mouse brain. The Gene Expression Nervous System Atlas or GENSAT, reported in this week's Nature, is based on specific gene expression. It aims to provide a detailed map of the different cell types in the central nervous system, offering new insights for neuroscientists and developmental biologists.
Using information from the mouse genome, Nathaniel Heintz and colleagues have built a library of bacterial artificial chromosomes (BACs). Each BAC represents a gene and carries the green marker protein GFP. The team used these BACs to make over 100 different transgenic mice, allowing the researchers to trace where and when specific genes are expressed and to visualize the connections made by cells expressing them.
One gene, Gscl, is normally produced in a brain region that regulates rapid-eye-movement (REM) sleep, they report. Gscl is missing in people with DiGeorge syndrome, a disorder involving congenital heart defects. The new finding may alert researchers to subtle alterations in REM sleep in DiGeorge patients, they speculate.
GENSAT has already provided data on 150 genes, but it aims to generate detailed expression maps for thousands more. "In the short term, neuroscientists can learn where their favourite gene is expressed and this knowledge might inform their studies into the functional consequences of its loss," says Huda Y. Zoghbi in an accompanying News and Views article.
 Health and Medicine: SARS reservoir runs deep (p915)
The reservoir of animals harbouring the SARS (severe acute respiratory syndrome) coronavirus may be larger than was realised and not confined to wild animals, according to a Brief Communication in this week's Nature.
In laboratory experiments, Albert D. M. E. Osterhaus and colleagues found that both domestic cats and ferrets are easily infected with SARS coronavirus taken from a human patient, and that they transmit the virus to uninfected animals housed with them. The infected cats showed no clinical symptoms but the ferrets fared less well.
This adds a domestic animal to the list of wild animals already known to carry the SARS virus, including masked palm civets and raccoon dogs found in a live-animal market in Guangdong, China — from where the virus is thought to have jumped into humans.
The results suggest that the SARS coronavirus may be lurking in a wide menagerie of animals, increasing the chances that it, or a closely related virus, might infect humans again. But because cats and ferrets show similar lung pathology to macaques infected with the SARS virus, they should prove useful as animal models in which to test SARS vaccines and medicines.
 Earth: Treading on thin ice? (pp947-950)
The thickness of Arctic sea ice may vary more over time than was previously thought, according to research in this week's Nature. Accurate measurements are needed to help predict future temperature rise and model global climate.
Seymour Laxon and colleagues measured the thickness of the ice covering the entire circumference of the Arctic Ocean. The team based their calculations on radar echoes received by satellites between 1993 and 2001. In winter, the mean ice thickness was a little under 3 metres. Over time, this figure fluctuated by up to 25 centimetres each way — 50% more than model-predicted variations.
The variation may mainly be due to summer melting. A one-day increase in melt season length could cause an extra 4.9 centimetres of summer ice melt, they predict. If melt season length continues to increase, Arctic sea ice will continue to thin, they conclude.
***Additional resources (including images, a press release from UCL and linked work) are now available to journalists on http://www.cpom.org. Once on the home page, click the 'for media' link on the left-hand side. The login you will be prompted for is 'media' and the password is 'seattle'. ***
 Neuroscience: Firing up perception (pp954-957; N&V)
Close your eyes. Bizarre though it may seem, the brain regions that process vision have not gone quiet, nor are they firing at random. Instead they are most likely generating organized patterns of electrical pulses, according to a study in this week's Nature. The finding may help researchers get a handle on that most elusive of phenomena, perception.
Tal Kenet and colleagues injected fluorescent dyes into the cortex of anaesthetized cats, enabling the researchers to visualize the spontaneous brain activity. The dyes are sensitive to the voltage changes that occur when neurons are stimulated, thus intensity of fluorescence provides a read-out of brain activity.
The visual cortex seems to possess intrinsic patterns of activity that evolve over time by switching between a specific set of states. The patterns are similar to those elicited by actual visual stimuli and may represent the brain's working hypothesis of the external world. The research is discussed further in an accompanying News and Views article by Dario L. Ringach.
 Space: Black hole in a spin (pp934-937; N&V)
Near-infrared flares have been spotted close to the event horizon of our Galaxy's very own black hole. The research, reported in this week's Nature, suggests that the supermassive black hole Sagittarius A* (Sgr A*) is rotating.
At four million times the size of our Sun, Sgr A* is small for a supermassive black hole, and also very dim. Reinhard Genzel and colleagues studied the infrared radiation emitted from Sgr A* using the Very Large Telescope in Chile's Atacama Desert. They spotted bursts of infrared activity that occurred roughly once every 17 minutes. Their regular recurrence suggests that the radiation comes from gas orbiting close to the black hole. By implication, Sgr A* itself may also be spinning.
The research is discussed further in an accompanying News and Views article by Ramesh Narayan.
 Health and Medicine: Probing bone structure (pp977-980)
Bone is naturally dynamic. It repairs itself when broken or when it is wasting away in conditions such as osteoporosis and brittle bone disease. The three-dimensional structure of the bone protein osteocalcin, unveiled in this week's Nature, may help us to understand such processes.
Osteocalcin is the most abundant protein in bone after collagen. It is thought to influence bone mineralization, in part by binding to the mineral component of bone, hydroxyapatite. Daniel S. C. Yang and colleagues report that the surface of pig osteocalcin has a pattern of negative charges that exactly mirror the positive charges on hydroxyapatite crystals. They speculate that this allows osteocalcin to bind to hydroxyapatite in bone, thus influencing its growth and degradation.
Proteins such as osteocalcin that can recognize crystal surfaces are important in many biological processes, such as protecting arctic fish from the freezing waters in which they live or directing the development of teeth and shells. Blood levels of osteocalcin are closely linked to bone metabolism, and can provide a biological marker for the progression of many debilitating bone diseases.
 And Finally"¦: Bird-brained reptiles flew with ease (pp950-953; N&V)
Pterosaurs may have soared through the skies with ease. The ancient reptiles, which flourished 251 to 65 million years ago, could even have outperformed modern birds, according to a study in this week's Nature.
Lawrence M. Witmer and colleagues studied a pair of pterosaur skulls and generated digital three-dimensional reconstructions of their brains. Overall, the structures were very bird-like, but two balance-related regions were particularly pronounced. These may have gathered information from the wing membranes and helped the reptiles build up detailed maps of the forces experienced by their wings. This could have given them excellent flight control, the authors speculate.
One of the pterosaurs — the large, short-tailed Anhanguera — may have carried its head at a jaunty angle, the authors add. The orientation of one balance-associated region suggests that the reptile's head was directed sharply downwards at angle of about 30 degrees.
Compared to their overall mass, pterosaur brains were smaller than those of modern birds. This may be because birds inherited their grey matter from relatively big-brained therapod dinosaurs, whereas pterosaurs acquired theirs from smaller-brained archosaurs, the authors suggest. The research is discussed further in an accompanying News and Views article by David M. Unwin.
ALSO IN THIS ISSUE"¦
 Motor neuron columnar fate imposed by sequential phases of Hox-c activity (pp926-933)
 Controlled collisions for multiparticle entanglement of optically trapped atoms (pp937-940)
 Demonstration of conditional gate operation using superconducting charge qubits (pp941-944)
 High-Q photonic nanocavity in a two-dimensional photonic crystal (pp944-947)
 SNARE-protein-mediated disease resistance at the plant cell wall (pp973-977)
 ATP-dependent reduction of cysteine"sulphinic acid by S. cerevisiae sulphiredoxin (pp980-984)
 Preserved organs of Devonian harvestmen (p916)
GEOGRAPHICAL LISTING OF AUTHORS"¦
The following list of places refers to the whereabouts of authors on the papers numbered in this release. For example, London: 4 - this means that on paper number four, there will be at least one author affiliated to an institute or company in London. The listing may be for an author's main affiliation, or for a place where they are working temporarily. Please see the PDF of the paper for full details.
CANADAOntario Flamborough: 6 Hamilton: 6 Toronto: 6
CHINAHong Kong: 2
FRANCEGif-sur-Yvette: 13Meuden: 5
GERMANYBerlin: 14Cologne: 5, 12Garching: 5, 9Giessen: 12Muenster: 14Munich: 9
ISRAELRehevot: 4, 5
JAPANItami: 11Kyoto: 11Saitama: 10Tsukuba: 10
THE NETHERLANDSRotterdam: 2
UNITED KINGDOMEdinburgh: 14Exeter: 3London: 3Norwich: 12
UNITED STATES OF AMERICACalifornia Berkeley: 5 San Francisco: 4 Stanford: 12Illinois Chicago: 12Maryland Bethesda: 1New York Buffalo: 1 New York: 1, 8 Ohio Athens: 7Tennessee Johnson City: 1Texas Austin: 7 Lubbock: 7Virginia Charlottesville: 8
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