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VOL.440 NO.7084 DATED 30 MARCH 2006
This press release contains:
* Summaries of newsworthy papers:
* Astronomy: How does your galaxy grow?
* Neuroanatomy: What makes kids 'brainy'?
* Cancer: Metastasis blocked
* Planetary science: Missing moonlets make clean sweep in Saturn's rings
* Cancer: RNA interference unearths cancer genes
* Evolution: How multicoloured beards help society
* Chemical physics: Crystallography without crystals
* Physics: Ratcheting backwards
* Evolution: Uprooting eukaryotic evolution
* And finally...Let's not twist again
* Mention of papers to be published at the same time with the same embargo
* Geographical listing of authors
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[2] Astronomy: How does your galaxy grow? (pp 644-647)
A computer simulation of a growing galaxy published in this week's Nature
shows how giant elliptical structures can grow from small clumps of gas and
dust. Masao Mori and Masayuki Umemura found that after about 300 million years of
growth, the bubbles of gas look like primitive galaxies called Lyman-alpha
emitters.
After about 1 billion years they have mutated into a form similar to
so-called Lyman break galaxies, which astronomers find in the most distant -
and therefore oldest - parts of the Universe. Finally, after 10 billion
years of evolution within the computer simulation, the structures look like
present-day elliptical galaxies.
The simulation shows how one form of galaxy can spontaneously evolve into
another without having to undergo collisions. It also predicts the mixture
of chemical elements in the simulated galaxy at each stage, and suggests
that it had roughly the same composition as our Solar System just a billion
years into its life.
CONTACT
Masao Mori (University of California, Los Angeles, CA, USA)
Tel: +1 310 825 4782; E-mail: [email protected]
[3] Neuroanatomy: What makes kids 'brainy'? (pp 676-679; N&V)
The search for a link between intelligence and brain size has a long and
controversial history. Writing in this week's Nature, a group of US
neuroscientists take the debate in a new direction. They reveal a link
between intelligence and changes in brain morphology during childhood and
adolescence that is more pronounced in high-ability children.
Philip Shaw and colleagues used magnetic resonance imaging (MRI) to take
snapshots of the brains of 307 children at several points during development
from childhood to adulthood. They revealed a distinct pattern of change in
high-ability children: certain parts of the cortex became thicker between
ages seven and eleven, before thinning through the teens. Similar changes
were seen in some other children, but the effect was more pronounced in the
highly intelligent group. Intelligence was measured by testing verbal and
non-verbal knowledge and reasoning.
The results suggest that intelligence is linked to the way the brain changes
during adolescence, rather than the total mass of brain matter, conclude
Shaw and colleagues. "'Brainy' children are not cleverer solely by virtue of
having more or less grey matter at any one age," they say. "Rather,
intelligence is related to dynamic properties of cortical maturation."
CONTACT
Philip Shaw (National Institutes of Health, Bethesda, Md, USA)
Tel: +1 301 492 8867; E-mail: [email protected]
Richard Passingham (Oxford University, Oxford, UK) N&V
Tel: +44 1865 271 418; E-mail: [email protected]
[4] Cancer: Metastasis blocked (pp 692-696)
An international research team has identified what may be a pivotal molecule
in the ability of tumours to metastasize - or spread - into bone. Metastases
are responsible for more cancer deaths than primary tumours, and bone is a
particularly fertile site into which other cancers often spread. Researchers
have long hypothesized that bone tissue might manufacture certain molecules
that entice cancer cells to lodge there.
In this week's Nature, Josef Penninger and his colleagues present evidence
that a cytokine protein called RANKL, which is produced at high levels in
bone marrow, acts through the RANK receptor on breast, prostate and skin
cancer cells and triggers their migration.
In a mouse model of melanoma, the team shows that blocking the action of
RANKL prevents the cancer from metastasizing to the bones but not other
organs, and protects the animals from paralysis and death. Drugs that
inhibit RANKL or its receptor might also block human metastases in bone,
they suggest.
CONTACT
Josef Penninger (Austrian Academy of Sciences, Vienna, Austria)
Tel: +43 1 79730 ext 454; E-mail: [email protected]
[6] Planetary science: Missing moonlets make clean sweep in Saturn's rings
(pp 648-650; N&V)
Evidence for moonlets in Saturn's rings, predicted by theory but never
observed before, is presented in this week's Nature.
Most scientists think that Saturn's rings formed after an icy moon was
broken up by an impact with a comet or asteroid. This should create a range
of debris, from kilometre-sized chunks down to small grains just a few
centimetres across.
Particles smaller than 10 metres across have been observed, and a pair of
kilometre-wide moons (Pan and Daphnis) plough gaps through the A ring, but
intermediate rocks have not been found.
Now, Matthew Tiscareno and colleagues have found propeller-shaped gaps in
the ring material that they believe are formed by moonlets about 100 metres
across, supporting the break-up theory. "The propellers offer a unique
chance to estimate the number of such embedded moonlets," comment Frank
Spahn and Jürgen Schmidt in a related News and Views article.
CONTACT
Matthew Tiscareno (Cornell University, Ithaca, NY, USA)
Tel: +1 607 255 5913; E-mail: [email protected]
Frank Spahn (Potsdam University, Potsdam, Germany) N&V
Tel: + 49 331 977 1626; E-mail: [email protected]
[7] Cancer: RNA interference unearths cancer genes
DOI: 10.1038/nature04687
***This paper will be published electronically on Nature's website on 29th
March at 1800 London time / 1200 US Eastern time (which is also when the
embargo lifts) as part of our AOP (ahead of print) programme. Although we
have included it on this release to avoid multiple mailings it will not
appear in print on 29th March, but at a later date.***
The technique of RNA interference (RNAi) allows scientists to switch off
specific genes associated with human disease. A paper published online this
week by Nature takes advantage of this technology to search for the
'Achilles' heel' of cancer cells - genes required for the survival of cancer
but not normal cells - and thus discover new potential therapeutic targets.
Louis Staudt and his co-workers built a library of viruses that make many
different small hairpin RNAs (shRNAs) that can disable, or 'interfere' with,
one of 2,500 human genes. They infected two different subtypes of B-cell
lymphoma cell lines with the library, and determined which shRNAs are able
to block the cells' growth, because these cells die out from the cell
population when compared with a control group of cells.
Using this method, the team identified one shRNA - targeting a gene called
CARD11 - that blocks the survival of one lymphoma subtype but not the other.
The CARD11 protein and associated molecules could make attractive
therapeutic targets for drugs, the authors say - and their method could be
used to identify many other key proteins that promote cell survival or death
in different cancers.
CONTACT
Luis Staudt (National Caner Institute, Bethesda, MD, USA)
Tel: +1 301 496 1892; E-mail: [email protected]
[8] Evolution: How multicoloured beards help society (pp 663-666)
The question of how cooperation, or altruism, arises in populations is a
tricky one for evolutionists. One proposed process, called the 'green beard
effect', relies on altruistic individuals bearing some sort of distinctive
marker, nicknamed a green beard. New research suggests, however, that the
effect will only work if the 'green beards' come in a range of different
variants - a society of multicoloured beard-bearers.
Theorists had imagined that, for the green beard effect to work, a single
gene would be responsible both for producing the marker and for instilling
the desire to cooperate with any other individual bearing the same badge,
which might be anything from a distinctive body coloration to a specific
cell-surface protein. But this system would leave the population vulnerable
to cheaters, who might evolve to bear the hallmark of an altruist without
actually being one, thus gaining the benefits of others' help without
meeting any of the costs of cooperating.
This problem is less severe, however, if the markers come in a range of
different variants (or 'beard colours'), and if the genes responsible for
the marker and cooperation are separate but loosely linked, explain Vincent
Jansen and Minus van Baalen in this week's Nature. According to their
computer simulations of population evolution, this system would allow
individuals sharing 'beards' of the same 'colour' to cooperate without fear
that the population will be flooded with unscrupulous cheats.
CONTACT
Vincent Jansen (University of London - Royal Holloway, Egham, UK)
Tel: +44 178 444 3179; E-mail: [email protected]
[9] Chemical physics: Crystallography without crystals (pp 655-658; N&V)
A method for calculating where atoms sit in non-crystalline atomic clusters
is proposed in this week's Nature.
Scientists use X-ray crystallography to view the positions of atoms in a
crystal but it can be hard to figure out the atomic structure of
non-crystalline materials. In general, probing the structure of materials
using beams of X-rays or neutrons only gives precise and accurate
information about atomic positions when the atoms' arrangement is periodic,
repeating again and again throughout the material. But increasingly,
chemists, materials scientists and engineers today are interested in
'nanostructured' materials, in which the atoms tend to be clustered into
units that are just a few to a few hundred nanometres in size, so that they
have no periodicity.
Simon Billinge and colleagues now show that the patterns of scattered X-rays
or neutrons from such nanostructures may contain an imprint of all the
information needed to figure out these positions. They show how even a crude
initial guess at where a few of the atoms sit in a nanoscale cluster of
atoms can be 'guided' towards progressively better guesses by the scattering
data, so that it eventually produces a unique indication of the atomic-scale
structure. The method involves compiling a 'league table' of possible
structures that is constantly updated as the calculation proceeds, with good
candidates promoted and poorer ones relegated, like football teams. They
name this approach the Liga algorithm, after Spain's La Liga soccer league.
CONTACT
Simon Billinge (Michigan State University, East Lansing, MI, USA)
Tel: +1 517 353 8697; E-mail: [email protected]
John Rehr (University of Washington, Seattle, WA, USA) N&V
Tel: +1 206 543 8593/2770; E-mail: [email protected]
[10] Physics: Ratcheting backwards (pp 651-654)
Scientists know that tiny particles jittering around at random can be made
to drift in a particular direction by placing them in an 'asymmetric
potential'; that is, by making their movement a series of uphill journeys
that are steeper in one direction than the other. It has been suggested that
this is how some molecules inside living cells acquire directional
preferences. Victor Moshchalkov and colleagues show in Nature this week that
under certain circumstances such particles can prefer the steeper to the
gentler incline - a seemingly counter-intuitive result.
The easiest way to see how random motion can give rise to directional motion
is to think of a particle moving over a surface with a set of parallel,
sawtooth-shaped ridges. The particle is more likely to wander up the gentler
incline of a ridge and pop over the top than to make the reverse trip up a
steep slope. So on average, it gradually moves in the direction of the
gentler slope. This can be regarded as a kind of ratcheting motion: easy one
way, hard the other.
Moshchalkov shows that if there are several particles moving over such a
'ratchet terrain', and if they repel one another, their interactions can
sometimes have the effect of reversing the preferred direction of flow. Even
more strangely, as the number of particles increases, the preferred
direction can switch back and forth repeatedly, first one way and then the
other.
The researchers report that this is just what happens experimentally for
vortices - whorls of electrical current - moving through an array of
asymmetric holes in a superconductor. They speculate that this dependence of
direction on the concentration of particles might be exploited in some
biological systems.
CONTACT
Victor Moshchalkov (Catholic University of Leuven, Leuven, Belgium)
Tel: +32 16 327618; E-mail: [email protected]
[11] Evolution: Uprooting eukaryotic evolution (pp 623-630)
The evolutionary tree of eukaryotes may be due a good prune. In this week's
Nature, Martin Embley and William Martin review how influxes of sequence
data and computational advancements are changing our view of eukaryotic
evolution - even to the point of questioning whether the notion of a 'tree'
is an adequate model for describing relationships between genomes.
Prokaryotes, such as bacteria, are organisms without a cell nucleus;
eukaryotes, such as plants and animals and a host of single-celled creatures
collectively known as protists, are organisms with complex cells in which
the genetic material is organized into membrane-bound nuclei. Originally,
prokaryote-to-eukaryote evolution seemed to be fairly clear-cut: the
intermediate between the two was believed to be a primitive eukaryote that
lacked mitochondria - an organelle found in most eukaryotic cells. However,
the reality is more complex. For example, it has been shown that Archezoa, a
collective group of protists believed to have split from the eukaryotes
prior to the acquisition of mitochondria, contain mitochondrial proteins.
Mitochondria are also found on separate sides of the tree, and both
anaerobic and aerobic eukaryotes have been shown to contain mitochondrial
homologues.
Such findings raise questions over the timing of mitochondrial endosymbiosis
and the role of anaerobic eukaryotes in eukaryotic evolution. The authors
conclude that although genomic studies are helping to unravel the broader
branches of the eukaryotic phylogenetic tree, its roots remain firmly buried
underground.
CONTACT
Martin Embley (University of Newcastle upon Tyne, Newcastle, UK)
Tel: +44 191 246 4804; E-mail: [email protected]
[12] And finally...Let's not twist again (pp 621)
Unlike a mountain climber swinging from a rope, a spider suspended from its
silk thread hardly ever twists. In a Brief Communication to this week's
Nature, scientists reveal just how good the damping properties of spider
silk are.
Olivier Emile and colleagues used a small rod to represent the weight of a
spider, and tied it to a thread of Kevlar, a synthetic organic polymer.
Twisting it through 90 degrees made the rod twist back and forth many times
around its original position. But when they substituted the Kevlar with
spider silk, this oscillation was damped down after just a few twists. And
unlike a copper thread, which has similarly few twists in the same
experiment, the silk fibre does not become brittle after several trials.
This adds yet another beneficial quality to the famously strong silk, and
the authors suggest it could prevent an abseiling spider from swinging in a
way that might attract predators.
CONTACT
Olivier Emile (University of Rennes, Rennes, France)
Tel: +33 2 2323 6521; E-mail: [email protected]
ALSO IN THIS ISSUE...
[13] Melting in the Earth's deep upper mantle caused by carbon dioxide
(pp 659-662)
[14] Chance and necessity in the evolution of minimal metabolic networks
(pp 667-670)
[15] Analysis of the DNA sequence and duplication history of human
chromosome 15 (pp 671-675)
[16] A C. elegans stretch receptor neuron revealed by a mechanosensitive
TRP channel homologue (pp 684-687)
[17] Analysis of a RanGTP-regulated gradient in mitotic somatic cells (pp
697-701)
[18] Oncogenic activity of Cdc6 through repression of the INK4/ARF locus
(pp 702-706)
ADVANCE ONLINE PUBLICATION
***This paper will be published electronically on Nature's website on 29th
March at 1800 London time / 1200 US Eastern time (which is also when the
embargo lifts) as part of our AOP (ahead of print) programme. Although we
have included it on this release to avoid multiple mailings it will not
appear in print on 29th March, but at a later date.***
[19] Copper-containing plastocyanin used for electron transport by an
oceanic diatom
DOI: 10.1038/nature04630
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.
AUSTRIA
Vienna: 4
BELGIUM
Leuven: 10
BRAZIL
Recife: 10
CANADA
London: 4
Montreal: 3, 4, 15, 19
Oshawa: 4
Toronto: 4
FRANCE
Paris: 8
GERMANY
Dusseldorf: 11
Gottingen: 1
Heidelberg: 14
HUNGARY
Budapest: 14
JAPAN
Ibaraki: 2, 5
Kanagawa: 2
Kurashiki: 5
Osaka: 5
SOUTH KOREA
Kyungbuk: 4
UNITED KINGDOM
Bath: 14
Egham: 8
London: 6, 15
Manchester: 14
Newcastle: 11
Oxford: 14
UNITED STATES OF AMERICA
California
Berkeley: 17
Los Angeles: 2
Pasadena: 16
Thousand Oaks: 4
Colorado
Boulder: 6
Iowa
Iowa City: 15
Maryland
Bethesda: 3, 7
College Park: 6
Massachusetts
Cambridge: 15
Michigan
Ann Arbor: 16
East Lansing: 9
Minnesota
Minneapolis: 13
New York
Ithaca: 6
Washington
Bothwell: 15
Seattle: 15
PRESS CONTACTS...
For North America and Canada
Katie McGoldrick, Nature Washington
Tel: +1 202 737 2355; E-mail: [email protected]
For Japan, Korea, China, Singapore and Taiwan
Rinoko Asami, Nature Tokyo
Tel: +81 3 3267 8751; E-mail: [email protected]
For the UK/Europe/other countries not listed above
Ruth Francis, Nature London
Tel: +44 20 7843 4562; E-mail [email protected]
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