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

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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 

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