This press release contains:
· Summaries of newsworthy papers:
Planetary science: Clues from beneath Mars
Palaeontology: Island-hopping dinosaurs
Molecular biology: Keeping the flow
Cancer: The mutation spectrum of lung cancer
Nuclear physics: The magic of tin
Oncology: A double-edged sword
Earth science: A weak lowermost mantle?
And finally…The secret life of Nectocaris
· Mention of papers to be published at the same time with the same embargo
· Geographical listing of authors
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[1] & [2] Planetary science: Clues from beneath Mars (pp 446-453)
A pinwheel array of spiral troughs has been one of the most perplexing features of layered deposits on the northern surface of Mars. Equally mysterious have been the forces responsible for the Chasma Boreale — a deep canyon cutting into the same deposits. Numerous explanations have been proposed, but with observations limited to the exposed surface of the planet, researchers have struggled to test which one, if any, is likely to be correct.
Using data from two orbiting radars capable of imaging the entire depth of the layered deposits, two groups have now peered beneath the Martian surface to uncover the most likely model. Both groups report their findings in this week's Nature.
On the basis of the internal structure of the spiral troughs, Isaac Smith and John Holt conclude that they have formed through a combination of material being deposited and the sculpting forces of wind and Sun. After forming, these troughs appear to have migrated towards the poles, and 600 metres upwards in elevation, over the past 2.5 million years.
In a second study, Holt and colleagues use data from the Mars Reconnaissance Orbiter to show that long-term and large-scale processes of deposition — rather than catastrophic events, ice flow or focused erosion — have produced the largest geomorphic anomaly in the polar ice of Mars, the Chasma Boreale.
Author contact:
Isaac Smith (University of Texas, Austin, TX, USA) – Author paper [1]
Tel: +1 512 471 0468
E-mail: [email protected]
John Holt (University of Texas, Austin, TX, USA) – Author paper [2]
Tel: +1 512 471 0487
E-mail: [email protected]
[3] Palaeontology: Island-hopping dinosaurs (pp 466-468; N&V)
The Ceratopsians, or horned dinosaurs, were a highly diverse, herbivorous group of dinosaurs that existed in the Late Cretaceous period. They lived in east Asia and western North America and were thought to have been geographically limited to these areas.
In this week’s Nature, Attila Ősi and colleagues describe a new species of ceratopsian, whose fossilized remains were found in what is now Hungary.
During the Late Cretaceous, much of Europe was a complex series of island chains lying between the African and Eurasian land masses. The discovery of the island-dwelling species — the first unambiguous find of a horned dinosaur from Europe — indicates that the interchange of animals between Asia and Europe during the Late Cretaceous may have been possible through some kind of ‘island-hopping’ dispersal event.
Author contact:
Attila Ősi (Hungarian Natural History Museum, Budapest, Hungary)
Tel: +36 1 210 1075 (ext. 2317)
E-mail: [email protected]
Xing Xu (Institute of Vertebrate Paleontology and Paleoanthropology, Beijing, China)
N&V author
Tel: +86 10 8836 9196
E-mail: [email protected]
[4] Molecular biology: Keeping the flow (pp 478-482)
Throughout people’s lives, tiny blood clots develop in the blood vessels of their brain. Many of these are cleared away by the force of blood flow and by digestive enzymes in a process called fibrinolysis. However, in a paper in this week’s Nature, Jaime Grutzendler and colleagues discover a new mechanism by which clots are removed.
Grutzendler and his group have used high-resolution microscopy to study fixed mouse brain tissues as well as an imaging technique called two-photon microscopy to track individual blood clots in the living mouse brain. They show that, within a week, many clots are actively removed by the endothelial cells that make up the walls of the blood vessels. Membrane projections from the endothelial cells wrap around the clots, and in so doing, form a new vessel wall. The underlying endothelium is then remodelled and the clot pushed out of the vessel and into the surrounding tissue where it is degraded.
This process takes longer in aged mice, suggesting that altering the efficiency of the clot-clearance mechanism could have therapeutic potential for patients recovering from a stroke or for age-related cognitive disorders.
Author contact:
Jaime Grutzendler (Northwestern University, Chicago, IL, USA)
Tel: +1 312 503 5298
E-mail: [email protected]
[5] Cancer: The mutation spectrum of lung cancer (pp 473-477)
Lung cancers may harbour tens of thousands of tumour-related mutations, indicates a study that compares the complete genomes of a primary lung cancer and neighbouring normal tissue. The data are revealed in this week’s Nature.
Genetic analysis of the two samples provides an overview of the many genetic changes that contribute to tumour formation in a single patient, in this case a 51-year-old male heavy smoker. Zemin Zhang and colleagues catalogue a staggering 50,000 genetic mutations — some known, some new — that occur in numerous different molecular pathways. The data indicate that genetically complex tumours may contain many partially redundant mutations, rather than being addicted to single oncogenes, and so may be more difficult to treat.
The team also report evidence of selection against mutations within expressed genes and in promoter regions. So the study provides an overview of the various forces that help shape the complex mutational landscape of a solid tumour.
Author contact:
Zemin Zhang (Genentech Inc., South San Francisco, CA, USA)
Tel: +1 650 225 4293
E-mail: [email protected]
[6] Nuclear physics: The magic of tin (pp 454-457; N&V)
A short-lived isotope of tin with ‘magic’ numbers of protons and neutrons has had its magic qualities confirmed by measurements made on a neighbouring isotope. The results, published in this week’s Nature, confirm the successful shell model of nuclear structure, and will help to predict the properties of more exotic nuclei, such as those involved in the synthesis of the heaviest elements.
Atomic nuclei have a shell structure, analogous to that of electrons in atoms, which gives special properties to nuclei with closed shells of protons and/or neutrons. Tin-132 (132Sn), with 50 protons and 82 neutrons, is doubly magic; but with a half-life of only 40 seconds, its properties have been difficult to examine.
Now Kate Jones and colleagues report the results of a technically challenging experiment, in which they added single neutrons to 132Sn to create 133Sn. By measuring the spectrum of quantum states available to the added neutron, the authors were able to show that the characteristics of the 133Sn nucleus are determined almost completely by this single neutron — confirming the closed-shell character of 132Sn. This finding extends the validity of the shell model to neutron-rich nuclei, and provides a benchmark for predicting the properties of nuclei even farther from stability, including those involved in neutron capture reactions in supernovae.
Author contact
Kate Jones (University of Tennessee, Knoxville, TN, USA)
Tel: +1 865 974 4022
E-mail: [email protected]
Paul Cottle (Florida State University, Tallahassee, FL, USA) N&V author
Tel: +1 850 644 5777
E-mail: [email protected]
[7] Oncology: A double-edged sword (pp 492-496; N&V)
The protein CD95 is a death receptor found on the surface of cells that leads to programmed cell death. CD95 is often downregulated in cancerous cells that are resistant to cell death, suggesting that the loss of CD95 is involved in tumour growth. In this week's Nature, however, Marcus Peter and colleagues show that knocking out CD95 in various human cancer cell lines can actually reduce tumour growth.
Peter and his team used a specific class of RNA virus to knock out CD95 in various cell lines representing breast, ovary, renal and liver cancers and neuroblastoma (a cancer that develops in nerve tissue). They consistently found that the loss of CD95 reduced the growth of tumours.
In the cell lines, and in mouse models of ovarian and liver cancer, the protein kinase JNK1 is phosphorylated when CD95 is activated, indicating that CD95 drives the proliferation of cancer cells by activating JNK.
Author contact:
Marcus Peter (Northwestern University, Chicago, IL, USA)
Please contact via:
Marla Paul (Senior Health Sciences Editor, Northwestern University)
Tel: +1 312-503-8928
E-mail: [email protected]
Douglas Green (St Jude Children’s Research Hospital, Memphis, TN, USA) N&V author
Tel: +1 901 595 3488
E-mail: [email protected]
[8] Earth science: A weak lowermost mantle? (pp 462-465; N&V)
Calculations of diffusion rates in the mineral thought to dominate the Earth’s lowermost mantle suggest that this region may be significantly weaker than the zone immediately above it. This finding, published this week in Nature, may provide an explanation for previously puzzling seismic observations of this region.
The deepest few hundred kilometres of the mantle, the D′′ layer, has seismic properties distinct from those of the overlying mantle, from which it is separated by a seismic reflector, also called D′′. A phase transition from the mineral perovskite (MgSiO3) to a denser, layered structure called ‘post-perovskite’ has been invoked to explain the D′′ reflector, but recent measurements of the width of this phase transition have posed problems for this explanation.
Michael Ammann and colleagues offer a possible solution to this conundrum, based on their calculated diffusion rates for magnesium and silicon ions in post-perovskite at lower-mantle conditions. They find that the rate at which these ions diffuse depends strongly on direction, with diffusion in the fast direction sufficiently fast to make post-perovskite significantly weaker than perovskite. The authors show how this weakness, combined with a preferential alignment of the deforming post-perovskite grains, could lead to seismic anisotropy in the D′′ layer, with a rapid onset that could explain the sharp D′′ reflector.
Author contact:
Michael Ammann (University College London, UK)
Tel: +44 207 6793 0165
E-mail: [email protected]
James Van Orman (Case Western Reserve University, Cleveland, OH, USA) N&V author
Tel: +1 216 368 3765
E-mail: [email protected]
[9] And finally…The secret life of Nectocaris (pp 469-472; N&V)
One of the strangest creatures recovered from the 505-million-year-old Burgess Shale of British Columbia, Nectocaris pteryx, is identified as a primitive form of cephalopod mollusc in a study in this week’s Nature.
Measuring only a few centimetres in length, Nectocaris, like many other animals extracted from the Burgess Shale, has resisted classification for decades, as the single surviving specimen presented a puzzling mix of chordate and arthropod features. Using ninety new specimens collected by the Royal Ontario Museum, Martin Smith and Jean-Bernard Caron demonstrate Nectocaris’s status as a soft-bodied creature, akin to a squid, although with two tentacles rather than eight or ten.
The research has important implications for the evolution of molluscs and, particularly, the origin of cephalopods and their relationship to other mollusc taxa.
Author contact:
Jean-Bernard Caron (Royal Ontario Museum, Toronto, Canada)
Tel: +1 416 586 5593
E-mail: [email protected]
Stefan Bengtson (Swedish Museum of Natural History, Stockholm, Sweden) N&V author
Tel: +46 8 519 542 20
E-mail: [email protected]
ALSO IN THIS ISSUE…
[10] Distinguishing the ultrafast dynamics of spin and orbital moments in solids (pp 458-461)
[11] The architecture of respiratory complex I (pp 441-445; N&V)
ADVANCE ONLINE PUBLICATION
These papers will be published electronically on Nature's website on 26 May at 1800 London time / 1300 US Eastern Time (which is also when the embargo lifts) as part of our AOP (ahead of print) programme. Although we have included them on this release to avoid multiple mailings they will not appear in print on 27 May, but at a later date.
[12] Distinct FGFs promote differentiation of excitatory and inhibitory synapses
DOI: 10.1038/nature09041
[13] Structure of the bifunctional isocitrate dehydrogenase kinase/phosphatise
DOI: 10.1038/nature09088
[14] Structural basis for 59-nucleotide base-specific recognition of guide RNA by human AGO2
DOI: 10.1038/nature09039
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.
CANADA
Kingston: 13
Montreal: 14
Toronto: 9
CHINA
Beijing: 13
FRANCE
Strasbourg: 10
GERMANY
Berlin: 10
Munich: 3
HUNGARY
Budapest: 3
JAPAN
Osaka: 7
UNITED KINGDOM
Bristol: 8
Cambridge: 7, 11
Guildford: 6
London: 8
UNITED STATES OF AMERICA
Arizona
Tucson: 2
California
Menlo Park: 10
Mountain View: 5
Pasadena: 2
South San Francisco: 5
Colorado
Boulder: 2
Golden: 6
District of Columbia
Washington: 2
Illinois
Chicago: 4, 7
Maryland
Baltimore: 3
Michigan
Ann Arbor: 12
East Lansing: 6
New Jersey
New Brunswick: 6
Ohio
Athens: 6
Pennsylvania
Bryn Mawr: 2
Tennessee
Cookeville: 6
Knoxville: 6
Oak Ridge: 6
Texas
Austin: 1, 2
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From Japan, Korea, China, Singapore and Taiwan
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Tel: +81 3 3267 8751; E-mail: [email protected]
From the UK
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