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SCIENCE sciencemag.org 4 JANUARY 2019 • VOL 363 ISSUE 6422 39
RESEARCHEdited by Stella Hurtley
I N SC IENCE J O U R NA L S
VIROLOGY
Mobile detection of Lassa virus Lassa fever is a hemorrhagic viral
disease endemic to West Africa.
Usually, each year sees only a
smattering of cases reported, but
hospitalized patients risk a 15%
chance of death. Responding to
fears that a 10-fold surge in cases
in Nigeria in 2018 signaled an
incipient outbreak, Kafetzopoulou
et al. performed metagenomic
nanopore sequencing directly
from samples from 120 patients
(see the Perspective by Bhadelia).
Results showed no strong
evidence of a new strain emerg-
ing nor of person-to-person
transmission; rather, rodent
contamination was the main
source. To prevent future escala-
tion of this disease, we need to
understand what triggers the
irruption of rodents into human
dwellings. —CA
Science, this issue p. 74;
see also p. 30
PROTEIN TRANSLOCATION
Posttranslational translocon architectureAbout a third of proteins are
transported into endoplasmic
reticulum by the universally
conserved Sec61 protein-
conducting channel. Itskanov
and Park determined a cryo–
electron microscopy structure
of the Sec complex from yeast,
which mediates posttranslational
translocation of many secretory
proteins across the endoplasmic
reticulum membrane. The study
reveals how Sec63 activates
the Sec61 channel for substrate
polypeptide insertion. The
structure also explains the
mutually exclusive binding of
Sec63 and the ribosome to the
channel. —SMH
Science, this issue p. 84
CHEMICAL PHYSICS
C60 at high resolution It generally takes more energy
for molecules to vibrate than to
rotate. A vibrational absorption
band thus encompasses many
distinct concurrent rotational
transitions, but these tend to blur
together when the molecules
have more than a few atoms.
Changala et al. succeeded in cool-
ing C60
fullerenes sufficiently to
obtain rotational resolution within
a C–C stretching band. Success
hinged on careful optimization
of argon buffer gas flow. Such
quantum state–resolved features
could aid characterization of
fullerene-type compounds in
exotic environments such as
interstellar space. —JSY
Science, this issue p. 49
ATOMIC PHYSICS
Making a strongly coupled plasma Plasmas—gases of ionized
atoms and electrons—are
naturally formed at high temper-
atures, such as those reached in
the interiors of stars. Describing
plasmas theoretically is tricky
when they are in the strongly
coupled regime; reaching that
regime in the laboratory would
provide a valuable benchmark
for theory. To that end, Langin
et al. worked with a cold plasma
created out of atoms of stron-
tium that were ionized by laser
light (see the Perspective by
Bergeson). They used lasers to
cool the ions down to about 50
CROWD DYNAMICS
A crowd that flows like water
The behavior of large numbers of insects, animals, and
other flocks is often based on rules about individual inter-
actions. Bain and Bartolo applied a fluid-like model to the
behavior of marathon runners as they walked up to the
start line of the Chicago Marathon (see the Perspective by
Ouellette). They observed nondamping linear waves with the
same speed for different starting corrals of runners and at dif-
ferent races around the world. Their model should apply both
to this type of polarized crowd as well as to other groups, which
may help guide crowd management. —BG
Science, this issue p. 46; see also p. 27
Runners moving down Columbus Drive at the Chicago Marathon, October 2017
Fluorinated aryl groups couple to form nanographenes Kolmer et al., p. 57
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Published by AAAS
sciencemag.org SCIENCE40 4 JANUARY 2019 • VOL 363 ISSUE 6422
millikelvin, reaching the desired
strongly coupled regime. —JS
Science, this issue p. 61;
see also p. 33
PALEONTOLOGY
A proto-mammalian giant Early terrestrial amniotes evolved
into two groups: the sauropsids,
which led to the bird and dinosaur
lineages, and the synapsids,
which led to mammals. Synapsids
were diverse during the Permian
but were greatly reduced after the
end-Permian extinction (about
252 million years ago). The few
groups that survived into the
Triassic were mostly small and
retained a sprawling gait. Sulej
and Niedźwiedzki, however,
describe a dicynodont from
the Late Triassic of Poland that
is as large as some coexisting
dinosaurs and appears to have
had an erect gait—like modern
mammals. Thus, megaherbivores
in the Triassic were not only dino-
saurs. —SNV
Science, this issue p. 78
SOCIAL SCIENCES
Deadliest 100 days of the HolocaustMore than 25% of the approxi-
mately 6 million Jews murdered
during the Holocaust were killed
in one 100-day period in 1942.
Stone used an unusual dataset
of railway transportation records
to show that during this period,
the Nazis murdered more than
1.47 million Jews, a kill rate that
is 10 times higher than previous
estimates. Contradicting contem-
porary analyses of the Holocaust,
the author shows that Operation
Reinhard was exceptionally
violent in its extreme kill rate,
number, and proportion of the
population murdered, even when
compared to other 20th-century
genocides. —PJB
Sci. Adv. 10.1126/
sciadv.aau7292 (2018).
PROKARYOTIC IMMUNITY
Additional, diverse CRISPR systems CRISPR systems have been
revolutionizing molecular biol-
ogy. Mining the metagenomic
database, Yan et al. system-
atically discovered additional
subtypes of type V CRISPR-Cas
systems. The additional Cas12
effectors displayed a range of
activities, including target and
collateral cleavage of single-
stranded RNA and DNA, as well as
double-stranded DNA nicking and
cleavage. These diverse nuclease
activities suggest how an ancient
transposase may have evolved
into various type V effectors and
expand the nucleic acid detec-
tion and genome-editing toolbox.
—SYM
Science, this issue p. 88
DRUG DEVELOPMENT
A long-lasting poison scavengerNerve agents are neurotoxic
compounds found in pesticides
and chemical weapons. They
act by blocking the transmis-
sion of nerve impulses to the
muscles, and exposure can be
fatal within minutes. Zhang et al.
developed a nanoparticle-based
bioscavenger that breaks down
organophosphate nerve agents
into innocuous compounds.
Prophylactic treatment of rats
and guinea pigs confirmed
low immunogenicity
and good biodistribu-
tion. Treated animals
were protected from
repeated exposure
to the nerve agent
sarin over 7 days. This
nanoscavenger might
thus help prevent nerve-
agent poisoning in
at-risk subjects. —MM
Sci. Transl. Med. 11,
eaau7091 (2019).
HUMAN GENETICS
Alzheimer’s disease in admixed peopleSeveral genes have been identi-
fied that increase the risk of
late-onset genetic disorders,
such as Alzheimer’s disease
(AD). Specifically, the ApoE «4
allele is associated with a higher
risk of developing AD. However,
individuals of African ancestry
that carry this variant appear
to be less prone to developing
AD. Rajabli et al. examined AD
cases and controls in admixed
individuals of Puerto Rican
and African-American descent
and found that individuals who
carried an African ApoE «4
background had less risk of
developing the disease. It seems
the African variant of ApoE «4
contains protective genetic
variants. —LMZ
PLOS Genet. 14, e1007791 (2018).
PLANT SCIENCE
Essential metal for plantsAlthough zinc (Zn) is an essen-
tial micronutrient for plants and
humans, much of the world’s
agricultural land is deficient in Zn.
Sinclair et al. studied plants that
are unable to deliver Zn into their
own xylem. The plant shoots were
thus internally starved regardless
of whether Zn was available from
the root. The Zn-starved shoots
signaled to roots to increase Zn
supplies. In response, the roots
up-regulated expression of the
genes encoding metal transport/
tolerance protein 2 (MTP2) and
heavy metal ATPase 2 (HMA2).
Local Zn deficiency in roots left
these same genes unaffected. It
seems that Zn taken up in lateral
roots is transported into the
endoplasmic reticulum by MTP2,
thus gaining access to the inter-
cellular symplastic network. The
Zn then progresses from outer
epidermal cells toward the core
of the root, where it is exported
by HMA2 into the xylem for trans-
port to the shoot. The shoot asks
for what it needs, and the root
delivers. —PJH
Plant Cell 30, 2463 (2018).
SKIN
Roots of acne Most people experience a bout
of acne at some stage in their
life. For an unlucky few, the skin
Edited by Caroline Ash
and Jesse SmithIN OTHER JOURNALS
Transport records have been analyzed to
estimate the number of Jews murdered by the
Nazis in 1942.
A Raggiana bird-of-paradise
from the Southern Highlands,
Papua New Guinea
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RESEARCH | IN SCIENCE JOURNALS
Published by AAAS
41-B 4 JANUARY 2019 • VOL 363 ISSUE 6422 sciencemag.org SCIENCE
RESEARCH
OPTICS
Exceptional points in optics Many complex systems operate
with loss. Mathematically, these
systems can be described as
non-Hermitian. A property of
such a system is that there can
exist certain conditions—excep-
tional points—where gain and
loss can be perfectly balanced
and exotic behavior is predicted
to occur. Optical systems gener-
ally possess gain and loss and so
are ideal systems for explor-
ing exceptional point physics.
Miri and Alù review the topic of
exceptional points in photonics
and explore some of the possible
exotic behavior that might be
expected from engineering such
systems. —ISO
Science, this issue p. 42
NEUROSCIENCE
Forgetting and receptor removal The trafficking of AMPA recep-
tors to and from the surface
of postsynaptic membranes
regulates synaptic strength
and underlies learning and
memory. Awasthi et al. found
that the integral membrane
protein synaptotagmin-3 (Syt3)
is predominantly found on
postsynaptic endocytic zones
of neurons, where it promotes
AMPA receptor internaliza-
tion (see the Perspective by
Mandelberg and Tsien). In Syt3
overexpressing or knockdown
neurons, synaptic transmis-
sion and short-term plasticity
were unchanged. However, in
neurons from Syt3 knock-
out mice, synaptic long-term
depression was abolished and
decaying long-term potentiation
endured. In Syt3 knockout mice,
spatial learning was unaltered;
however, these animals showed
signs of impaired forgetting and
relearning during the water maze
spatial memory task. —PRS
Science, this issue p. 44;
see also p. 31
IMMUNOLOGY
Commensal-specific T cells are flexible Barrier tissues, like the skin, are
sites where noninvasive com-
mensal microbes constantly
interact with resident T cells.
These encounters can result
in commensal-specific T cell
responses that promote, for
example, host defense and tis-
sue repair. Harrison et al. show
that subsets of skin-resident
commensal-specific interleukin-
17A–producing CD4+ and CD8+
T cells have a dual nature:
They coexpress transcription
factors that direct antagonistic
antimicrobial (type 17) and
antiparasite and pro–tissue
repair (type 2) programs. When
skin is damaged, epithelial cell
alarmins license type 17 T cells
to turn on type 2 cytokines.
Thus, commensal-specific type
17 T cells can direct antimicro-
bial activity under homeostatic
conditions but rapidly turn on
tissue repair in the context of
injury. —STS
Science, this issue p. 43
PLANT SCIENCE
Fixing photosynthetic inefficienciesIn some of our most useful
crops (such as rice and wheat),
photosynthesis produces toxic
by-products that reduce its
efficiency. Photorespiration
deals with these by-products,
converting them into metaboli-
cally useful components, but at
the cost of energy lost. South et
al. constructed a metabolic path-
way in transgenic tobacco plants
that more efficiently recaptures
the unproductive by-products
of photosynthesis with less
energy lost (see the Perspective
by Eisenhut and Weber). In field
trials, these transgenic tobacco
plants were ~40% more produc-
tive than wild-type tobacco
plants. —PJH
Science, this issue p. 45;
see also p. 32
NANOMATERIALS
Nanographenes on oxides The growth of nanographene
islands and ribbons on metal
surfaces can be accomplished
on single-crystal metal surfaces
through carbon-carbon coupling
reactions, but the surfaces of
oxides do not assist these reac-
tions. Kolmer et al. show that
fluorinated aryl groups can be
coupled to form nanographenes
on the rutile surface of titanium
oxide. The fluorine substitution
of the aryl groups was selected
so that as the carbon-fluorine
bonds were thermally activated,
a stepwise process sequentially
added aromatic rings around
a central aryl group until it was
completely substituted. —PDS
Science, this issue p. 57
MESOSCOPIC PHYSICS
A backward current Two-dimensional materials in a
magnetic field can exhibit the so-
called quantum Hall effect. This
regime is characterized by cur-
rents running along the edge of
the sample in the “downstream”
direction determined by the sign
of the magnetic field. Lafont et
al. studied electrical transport in
GaAs-AlGaAs heterostructures,
focusing on a previously less-
studied spin-unpolarized state
in the fractional quantum Hall
regime. By considering various
experimental configurations,
they observed a component of
the charge current flowing in the
opposite, “upstream” direction.
—JS
Science, this issue p. 54
NEUROSCIENCE
Another primary visual cortex Most functional studies in the
visual system have focused on
the cortical representation of
the geniculo-striate pathway
that links the retina to the
cortex. The parallel collicular
pathway is believed to sparsely
project throughout the visual
cortex and have a modulatory
role on cortical responses to
visual stimuli. Beltramo and
Scanziani found a visual cortical
area that is entirely dedicated
to the superior colliculus. This
area can discriminate moving
visual stimuli that the “classical”
primary visual cortex cannot.
Thus, the superior colliculus, a
phylogenetically ancient struc-
ture, has its own projection in
neocortex that provides this area
with exquisite feature-detection
abilities not found in the classical
primary visual cortex. —PRS
Science, this issue p. 64
CLIMATE CHANGE
Deep Pacific cooling Earth’s climate cooled consider-
ably across the transition from
the Medieval Warm Period to
the Little Ice Age about 700
years ago. Theoretically, owing
to how the ocean circulates, this
cooling should be recorded in
Pacific deep-ocean tempera-
tures, where water that was on
the surface then is found today.
Gebbie and Huybers used an
ocean circulation model and
observations from both the end
of the 19th century and the end
of the 20th century to detect
and quantify this trend. The
ongoing deep Pacific is cooling,
which revises Earth’s overall heat
budget since 1750 downward by
35%. —HJS
Science, this issue p. 70
EVOLUTION
DNA breakage and adaptation Adaptation to new environments
often occurs in similar ways
across different colonization
events. Stickleback fish repre-
sent a classic example of this, in
which repeated colonizations of
freshwater have resulted in the
loss of pelvic hind fins. Previous
work has shown that a pelvic
enhancer gene is involved. Xie et
al. now show that this gene lies
within a region of the genome
Edited by Stella HurtleyALSO IN SCIENCE JOURNALS
Published by AAAS
SCIENCE sciencemag.org 4 JANUARY 2019 • VOL 363 ISSUE 6422 41-C
that is prone to double-stranded
DNA breakage owing to a high
thymine-guanine content. This
enhanced region of breakage
could lead to enhanced mutation
rates that facilitate repeated
adaptations to new environ-
ments. —SNV
Science, this issue p. 81
CONSERVATION
The distinctive sound of a biodiverse forestAssessing the state of
biodiversity in a forest is a time-
consuming task that typically
requires detailed on-the-ground
surveys. In a Perspective,
Burivalova et al. explain that
recordings of soundscapes
can provide an easier route to
this information. By record-
ing soundscapes from a forest
over time and comparing them
to a regional baseline, scien-
tists can determine whether a
forest’s ecosystem is healthy
or not. If the soundscape of
a forest spared from conver-
sion becomes impoverished
and altered, an on-the-ground
survey would be warranted. This
approach may be particularly
useful for companies interested
in sustainability certification
or zero-deforestation commit-
ments. —JFU
Science, this issue p. 28
TUBERCULOSIS
Faulty kinase purged by tuberculosis?Rare mutations in genes involved
in interferon-g–dependent
immunity underpin human
genetic susceptibility to severe
mycobacterial diseases,
including primary tuberculosis.
Boisson-Dupuis et al. investi-
gated whether two common
missense variants of the TYK2
Janus kinase that have impaired
catalytic activity conferred an
increased risk of tuberculosis.
Individuals homozygous for
the P1104A (proline to alanine
substitution at residue 1104)
variant of TYK2 are markedly
predisposed to developing
primary tuberculosis, defining
a common monogenic etiol-
ogy for the “white plague.” The
current frequency of the P1104A
allele in European popula-
tions is significantly decreased
compared with its frequency in
ancient European DNA samples.
These findings suggest that
negative selection against the
TYK2 P1104A allele by endemic
tuberculosis in Europe may have
contributed to a slow genetic
purge of this susceptibility allele
during recent millennia. —IW
Sci. Immunol. 3, eaau8714 (2018).
CANCER
Altering membrane potential for cancerPolymorphisms in the G pro-
tein–coupled receptor GPR35
are associated with increased
risk for certain inflammatory
diseases that can progress to
cancer. Schneditz et al. found
that GPR35 promoted the activ-
ity of Na+- and K+-dependent
adenosine triphosphatase
(Na+,K+-dependent ATPase),
a transmembrane pump that
sets the membrane potential in
cells. This effect was enhanced
by a disease-associated GPR35
variant. Stimulation of Na+,K+-
ATPase activity by GPR35
increased glycolysis and pro-
liferation in intestinal epithelial
cells. Na+,K+-ATPase deficiency
or treatment with a pepducin
targeting GPR35 decreased
tumor burden in mouse models
of intestinal cancer. —WW
Sci. Signal. 12, eaau9048 (2019).
Published by AAAS