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844 18 NOVEMBER 2016 • VOL 354 ISSUE 6314 sciencemag.org SCIENCE
ACTIVE MATTER
Directing traffic with patternsBiological entities, such as
bacteria, may direct their motion
in response to their environment,
but this usually does not lead to
large-scale patterns or collective
behavior. Peng et al. found that
the orientational ordering of a
liquid crystal could direct the flow
of self-propelling bacteria, which
in turn influenced the patterning
of the liquid crystal molecules.
Patterns on a substrate caused
surface anchoring of the liquid
crystals that transmitted to the
ordering of the bacteria, thus
imparting control on what would
otherwise be chaotic out-of-equi-
librium behavior. —MSL
Science, this issue p. 882
DNA METHYLATION
Combating parasitic DNA by methylationDNA methylation plays an
important role in repressing
the expression of “parasitic”
DNAs, such as transposable
elements, which have invaded
our genomes. Mammals have
three DNA methyltransferase
enzymes. Barau et al. discovered
a fourth DNA methyltransferase
enzyme in mice. The enzyme
DNMT3C is a duplication of
DNMT3B and is found in male
germ cells. There it targets evo-
lutionarily young transposons,
of which there is a heavy burden
in the mouse genome. DNMT3C
methylates and silences the
young transposons, preserving
male fertility. —GR
Science, this issue p. 909
NEURODEGENERATION
Tau phosphorylation—not all badAlzheimer’s disease presents
with amyloid-β (Aβ) plaques
and tau tangles. The prevail-
ing idea in the field is that Aβ
induces phosphorylation of
tau, which in turn mediates
neuronal dysfunction. Working
in Alzheimer’s disease mouse
models, Ittner et al. found
evidence for a protective role of
tau in early Alzheimer’s disease.
This protection involves specific
tau phosphorylation at threonine
205 at the postsynapse. A pro-
tective role of phosphorylated
tau in disease challenges the
dogma that tau phosphorylation
only mediates toxic processes.
—SMH
Science, this issue p. 904
DRUG DELIVERY
Toward malaria eradicationEven though we know how to
prevent malaria, we have failed
to eliminate this damaging
disease. Bellinger et al. designed
an easy-to-administer device
that provides long-lasting
delivery of an antimalarial drug.
A star-shaped, drug-containing
material is packaged into a
capsule. When swallowed, the
capsule dissolves in the stomach
and the star unfolds, assuming a
shape that cannot pass further
down the intestine. The star
delivers the anti-malarial drug
for weeks, but eventually falls
apart and passes harmlessly out
of the body. —KLK
Sci. Transl. Med. 8, 365ra157 (2016).
TYPE 1 DIABETES
Exhausting autoimmunity In the case of autoimmune dis-
eases, such as type 1 diabetes,
so-called “exhausted” T cells
may be the answer to stopping
disease. Long et al. report that
the best responses in type 1
diabetics treated with tepli-
zumab, a monoclonal antibody
against CD3, were associated
with CD8+ T cells with features
of exhausted T cells. These cells
recognized a broad spectrum
of autoantigens but prolifer-
ated less than nonexhausted
cells ex vivo. However, they
were not terminally exhausted:
Stimulation with a ligand for the
inhibitory receptor TIGIT further
down-regulated their activa-
tion. Inducing T cell exhaustion
may thus represent a potential
therapeutic approach in type 1
diabetes. —ACC
Sci. Immunol. 1, eaai7793 (2016).
URBAN ECOLOGY
C4 plants in the heat of the cityCities tend to have a warmer
microclimate than their
surroundings—the so-called
“urban heat island” effect. The
elevated temperature, along
with other aspects of the urban
environment, can have a marked
influence on the organisms
that live in cities. Duffy and
Chown find that plants with C4
photosynthetic metabolism, a
trait that is favored in warmer
herbaceous communities, are
more common in European
cities than in adjacent nonurban
habitats. They predict that under
further climatic warming, C4
species may become generally
more widespread in temperate
habitats, compared with C3 spe-
cies that are adapted to cooler
conditions. —AMS
J. Ecol. 104, 1618 (2016).
METABOLISM
Small RNA regulates glucose homeostasis Noncoding RNAs, such as
microRNAs, regulate gene
expression through RNA silenc-
ing and posttranscriptional
gene regulation. Lin et al. show
that miR-155 is important for
glucose homeostasis and insulin
sensitivity. When miR-155 is
IN OTHER JOURNALS Edited by Caroline Ash
and Jesse Smith
Hubble eXtreme Deep Field
view of distant galaxies
Higher temperatures in cities select for C4 plants. PH
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RESEARCH | IN SCIENCE JOURNALS
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18 NOVEMBER 2016 • VOL 354 ISSUE 6314 845SCIENCE sciencemag.org
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overexpressed in mice, they
become hypoglycemic, whereas
if miR-155 is deleted, the result
is hyperglycemia and insulin
resistance. miR-155 does not
seem to alter pancreas morphol-
ogy or β-cell function; instead, it
appears to act on negative regu-
lators of insulin signaling, such
as C/EPBb, HDAC4, and SOCS1.
Patients with type 2 diabetes
show reduced miR-155, suggest-
ing that it may also be involved in
human insulin signaling. The dis-
covery of this microRNA function
opens a window of opportunity
for the treatment of diabetes
through glycemic control. —BAP
PLOS Genet. 10.1371/journal.
pgen.1006308 (2016).
TISSUE REPAIR
Getting one’s joint out of noseArticular cartilage lubricates
joints and is essential for
pain-free movement. Unlike
other tissues, injured cartilage
does not repair on its own. One
common treatment involves har-
vesting cartilage-secreting cells
called chondrocytes from the
injured joint, expanding the cells
in culture for a few weeks, and
then implanting them back into
from their European forager
counterparts but, like them,
showed little genetic diversity,
indicating a small population.
The later farmer-settlers, who
had acquired pottery-making
skills, were genetically more
diverse. These data point to an
additional wave of migration
from the Fertile Crescent or the
Levant that brought new genes
and promoted further westward
expansion before the mobile
hunter-gatherers of the northern
steppes added their genes to the
European mix. —CA
Curr. Biol. 26, 2659 (2016).
CATALYSIS
Longer lifetimes for a metal oxideAlthough heterogeneous molyb-
denum catalysts can convert
cyclohexene to its epoxide with
high conversion and selectivity,
the catalysts deactivate quickly
because the Mo species leach
into solution. Noh et al. show
that a more stable catalyst can
be made by depositing Mo via a
metallorganic complex onto the
zirconium oxide nodes within the
metal organic framework (MOF)
NU-1000. After exposure to air to
form the Mo oxide species, this
catalyst showed activity com-
parable to that of epoxidation of
Mo supported on ZrO2. However,
the ZrO2 support lost 80% of
its Mo after reaction, whereas
no loss of Mo occurred for the
MOF catalyst. Density functional
theory calculations indicate that
the loss of Mo(VI) from the MOF
Zr node is energetically unfavor-
able. —PDS
J. Am. Chem. Soc. 10.1021/
jacs.6b08898 (2016).
ANTIBIOTIC RESISTANCE
No silver bullet for wastewater treatmentThe spread of antibiotic
resistance is a major public
health concern. Czekalski et al.
investigate whether ozonation of
wastewater can help to combat
this spread by eliminating
resistant bacteria. In labora-
tory experiments, ozone doses
that can be used in full-scale
applications disrupted intracel-
lular resistance genes. However,
ozonation of secondary effluent
at a wastewater treatment plant
did not affect the abundance of
intracellular resistance genes,
and multiresistant bacteria
partly regrew after ozonation.
The results have important
implications for wastewater
treatment plants that are plan-
ning to implement ozonation.
—JFU
Environ. Sci. Technol. 10.1021/acs.
est.6b02640 (2016).
the joint. Animal studies suggest
that chondrocytes from a differ-
ent tissue source, the nose, are
better at regenerating articular
cartilage. Mumme et al. tested
this less invasive procedure in
a pilot study of 10 patients with
knee injuries. In all cases, they
successfully produced cartilage
tissue ex vivo by using chon-
drocytes taken from the nasal
septum. All patients reported an
improvement in clinical scores
for pain, knee function, and qual-
ity of life. —PAK
Lancet 388, 1985 (2016).
PALEOANTHROPOLOGY
Farmer-foragers went westHumans began to settle and
combine farming with foraging
about 12,000 years ago. Over
the next 2000 to 3000 years,
they moved west from the Fertile
Crescent into Anatolia, although
it seems, from the distribution
of obsidian flints, that the east-
ern and western populations
kept in contact. Kılınç et al.
obtained genome sequence data
from nine Neolithic individuals
from two ancient village sites
in Anatolia. The settlers from
the older site were distinct
GALAXIES
How many galaxies are in the universe?
Counting the number of galaxies is
a complicated problem because
astronomical surveys are biased
and incomplete: It is easier to
detect a bright nearby galaxy than
a faint distant one. Small galaxies are the
most numerous, but a boundary must
be drawn between them and large star
clusters. Distant galaxies are seen as they
were earlier in their lifetime, and galaxy
numbers can fall through merging. Taking
into account these effects and more,
Conselice et al. combined and extrapo-
lated results from numerous surveys to
determine that there are 2.0 ± 0.6 trillion
galaxies in the observable universe. The
vast majority still await discovery. —KTS
Astrophys. J. 830, 83 (2016).
Fragment of a clay pot discovered
at Tepecik Çiftlik, Turkey
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No silver bullet for wastewater treatmentJulia Fahrenkamp-Uppenbrink
DOI: 10.1126/science.354.6314.844-g (6314), 844-845.354Science
ARTICLE TOOLS http://science.sciencemag.org/content/354/6314/844.7
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