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Vol 463|14 January 2010
RESEARCH HIGHLIGHTS
X. BONNET/CEBC-CNRS
Snakes face the heat
J. Exp. Biol. 213, 242–248 (2010)
How animals will cope with changing global temperatures is a
major question — especially for cold-blooded animals that rely
on the environment to regulate their body temperature. Fabien
Aubret at the French National Center for Scientific Research
in Moulis and Richard Shine of the University of Sydney,
Australia, investigated this by raising tiger snakes (Notechis
scutatus, pictured) under different thermal conditions.
They found that animals exposed to high temperatures
(19–37°C) during the first 14 months of their lives exhibited
the same body temperature, locomotor speed and predator
responses as those raised in cold and intermediate
environments.
However, regardless of the temperature they were raised in,
none of the animals was later able to respond successfully to a
rapid change in ambient conditions. The authors suggest that
the main impact of climate change may result from greater
year-to-year variations than from an overall upward trend in
temperature.
Brain cell gain and cocaine
J. Neurosci. 30, 304–315 (2010)
Blocking the growth of new neurons in a key
region of the adult rat brain may make the
animal more vulnerable to cocaine addiction
and relapse.
Amelia Eisch at the University of Texas
Southwestern Medical Center in Dallas and
her colleagues inhibited neurogenesis in the
adult hippocampus by irradiating it. The rats
were then trained to give themselves cocaine.
Animals whose hippocampus had been
zapped self-administered more cocaine than
those who had received a sham irradiation.
When brain-cell generation was blocked
after the rats had learned to give themselves
cocaine, they worked harder than control rats
to get the drug when it was no longer available.
MATERIALS SCIENCE
Sequencing with carbon
Nano Lett. doi:10.1021/nl9029237 (2010)
A device that could rapidly sequence a single
strand of DNA passing through a gap in a
piece of graphene — a one-atom thick sheet
of carbon — is outlined by Henk
Postma of California State University,
Northridge.
Postma’s device would make use
of graphene’s conducting ability. The
graphene would act as the electrodes
to measure the conductance of DNA
as it moved through the gap. Each of
the four bases that make up DNA has
a unique conductance, which would
allow the DNA sequence to be read.
Other nanopores have been devised for
DNA sequencing, but graphene’s innate
conductance and sturdiness makes it more
attractive, says Postma.
CANCER BIOLOGY
Kicking out cancer cells
J. Cell Sci. 123, 171–179 (2010)
It seems that when some cells turn cancerous,
their healthy neighbours can detect the
transformation and eject the cells. Yasuyuki
Fujita of University College London and
his colleagues have identified signalling
pathways that may drive this process.
Cultured canine kidney cells bearing the
mutated Src cancer gene are squeezed out in
a specific direction from a layer of normal
cells (pictured below left) but remain in place
when surrounded by similar cancer cells
(right). The authors pinpointed two proteins,
myosin II and FAK, that are activated in the
cancer cells when surrounded by normal cells
and are involved in the cancer cells’ ejection.
The authors say that the process prevents
cancer cells from spreading around the body,
because the cells are kicked out in the opposite
direction to that required for such metastasis.
138
© 2010 Macmillan Publishers Limited. All rights reserved
GEOSCIENCE
Extraterrestrial dust
Earth Planet. Sci. Lett. 289, 287–297 (2010)
Studies of an ice core taken from East
Antarctica’s Dome Fuji reveal evidence of
two meteoritic events that took place around
434,000 and 481,000 years ago. Keiji Misawa
of Japan’s National Institute of Polar Research
in Tokyo and his colleagues report their
discovery of silicate-rich dust layers. Analysis
of the dust indicated an extraterrestrial source.
The dust layers, which are a few
millimetres thick, are similar to those found
in another core drilled about 2,000 kilometres
to the east. The authors say that this massive
spread of debris came from large impacts,
evidence of which has not previously been
found in the Southern Hemisphere.
BIOGEOCHEMISTRY
DDT in the ocean
Geophys. Res. Lett. doi:10.1029/2009GL041340
(2009)
Once hailed as an effective insecticide, but
later loathed for its toxic environmental effects,
DDT (dichlorodiphenyltrichloroethane)
was banned in many countries in
the 1970s. Now, a modelling study
suggests that, in parts of the ocean,
it may have accumulated in large
enough amounts to oversaturate the
surface waters and be re-emitted into
the atmosphere.
Irene Stemmler and Gerhard
Lammel, both now at the Max Planck
Institute for Chemistry in Mainz,
Germany, used a three-dimensional
J. CELL SCI.
NEUROSCIENCE
RESEARCH HIGHLIGHTS
Vol 463|14 January
NATURE|Vol
463|142010
January 2010
For a longer story on this research,
see go.nature.com/ZVw7VN
out the neural mechanism behind this by
studying 20 blind migraine sufferers. Those
who could detect light reported heightened
pain when exposed to it.
The researchers then examined the
posterior thalamus — the brain region
containing neurons that fire during
migraines — of anaesthetized rats. They
found that projections from a specific group
of retinal cells converge on other cells that
process both migraine pain and light signals.
Most of the retinal cells involved can respond
to light but cannot form images and are still
functional in some blind people.
IMMUNOLOGY
Double punch for HIV
J. Exp. Med. doi:10.1084/jem.20091933 (2009)
The antiviral enzyme APOBEC3G inhibits
HIV infection by causing damaging genetic
mutations in replicating viruses. Arnaud
Moris of the Pasteur Institute in Paris and his
colleagues now demonstrate that this enzyme
also combats HIV by triggering the activation
of the immune system’s cytotoxic T cells,
which kill helper T cells infected with HIV.
Moris and his co-workers showed in vitro
that HIV particles harbouring APOBEC3G
are more effective activators of HIV-specific
cytotoxic T cells than viruses lacking the
enzyme. Mutating the enzyme’s active site
eliminated this effect.
NEUROSCIENCE
Dark migraine relief
Nature Neurosci. doi:10.1038/nn.2475 (2010)
For many migraine sufferers, light makes
the pain worse. Rami Burstein of Harvard
Medical School in Boston, Massachusetts,
and his colleagues began their quest to figure
JOURNAL CLUB
Monica Gotta
University of Geneva Medical
School, Switzerland
A cell biologist connects her
research to bacterial brain
invasion.
My main interest is in
understanding how some cells
organize their structure and
components asymmetrically — a
property called cell polarity. When
I moved to my current job in a
medical faculty I was asked to teach
a course on infectious diseases. So I
MOLECULAR BIOLOGY
Flowering time unravelled
Cell 140, 136–147 (2010)
Plants are sensitive to temperature and
respond to changes by, for example,
adjusting flowering times. Vinod Kumar
and Philip Wigge of the John Innes Centre in
Norwich, UK, have discovered the molecular
mechanism behind this in the model plant
Arabidopsis thaliana. Warmer temperatures
trigger the loosening of certain nucleosomes
— tightly wound DNA structures — allowing
the up- or downregulation of certain genes.
The researchers first identified a mutant
(pictured above right) in which flowering
was very excited by the publication
of a paper from Mathieu Coureuil
at the University of Paris Descartes
and his colleagues that brings
together my passion and my
teaching activity. The work shows
that a bacterial pathogen can reach
the brain by destroying cell polarity
(Coureuil, M. et al. Science 325,
83–87; 2009).
Few bacteria are able to cross
the blood–brain barrier, and it is
not known whether those that
can do so by moving through or
between cells. The bacterium
Neisseria meningitidis can cross this
barrier. It adheres to cells lining
occurs more rapidly than usual — the same
behaviour seen in plants exposed to warmer
temperatures. They found that the mutant
plant is unable to incorporate a protein
called histone H2A.Z into its nucleosomes
to keep them wound up. The duo found
that as temperatures rise, H2A.Z is less able
to bind to nucleosomes, causing them to
unravel.
DRUG DISCOVERY
Virtual antibiotic screen
Proc. Natl Acad. Sci. USA doi:10.1073/
pnas.0909181107 (2010)
The hunt for new antibiotics can be aided by
computational tools that identify indispensible
components of a pathogen’s physiology.
Olaf Wiest at the University of Notre
Dame in Indiana, Zoltán Oltvai of the
University of Pittsburg in Pennsylvania
and their colleagues analysed the
metabolic networks of Escherichia coli and
Staphylococcus aureus and identified 13
enzymes that catalyse essential reactions in
both these bacteria. The researchers then ran
molecular simulations to find 41 compounds
with potential to inhibit these enzymes.
Finally, they confirmed that some of those
compounds reduced enzyme activity and
killed the bacteria in vitro.
The study, the authors say, shows how
genomic and metabolic information can
enhance drug discovery, including the
development of tailored therapies for specific
bacterial strains.
Correction
The two images illustrating the Research
Highlight ‘Dual-aspect particles’ (Nature 462,
828; 2009) were inadvertently swapped. The
left-hand image shows the liquid phase of
Janus particles, and the right-hand image shows
the gas phase.
the brain’s blood vessels using
type IV pili — hairlike appendages
that connect the bacterium to the
interior of these endothelial cells.
Using human brain endothelial
cells and N. meningitidis in culture,
Coureuil et al. show that a complex
of polarity proteins — Cdc42,
PAR6, PKC and PAR3, which form
tight junctions between endothelial
cells — are recruited to the site of
bacterial adhesion. This results in
depletion of these proteins at the
junctions and thus the formation of
gaps between infected cells.
Although this study was
performed in cultured cells
owing to a lack of suitable animal
models, it strongly suggests that
N. meningitidis enters the brain by
disrupting the junctions between
cells — allowing the bacteria to
squeeze in between them — and not
by penetrating the cells themselves.
This elegant paper unveils
a route that may also be used
by other pathogens that cross
the blood–brain barrier. It also
underscores an important function
of cell polarity: protecting our
brain from infectious diseases.
Discuss this paper at http://blogs.
nature.com/nature/journalclub
139
© 2010 Macmillan Publishers Limited. All rights reserved
ELSEVIER
atmosphere–ocean global circulation
model that included two-dimensional
representations of vegetation surfaces and
soils to track the movement of DDT. Their
analysis revealed that the western North
Atlantic ocean has been re-emitting DDT
for more than three decades, longer than
most other regions. The distribution of the
pesticide has been creeping northwards,
despite the DDT bans in the northern high
and mid-latitudes. The authors caution that
DDT-monitoring data have not been gathered
for long enough to test the model.