CR
ED
ITS
: (T
OP
TO
BO
TT
OM
) E
. H. K
EL
LO
GG
ET
AL
.; C
YR
IL R
UO
SO
/M
IND
EN
PIC
TU
RE
S/
GE
TT
Y I
MA
GE
S
1198 15 JUNE 2018 • VOL 360 ISSUE 6394 sciencemag.org SCIENCE
is consistent with adjacent layers
naturally having opposite mag-
netizations, which align parallel
to each other in high magnetic
fields. —JS
Science, this issue p. 1218, p. 1214
PHOTOSYNTHESIS
Lower-energy photons do the work, too Plants and cyanobacteria
use chlorophyll-rich photo-
system complexes to convert
light energy into chemical
energy. Some organisms
have developed adaptations
to take advantage of longer-
wavelength photons. Nürnberg
et al. studied photosystem
complexes from cyanobac-
teria grown in the presence
of far-red light. The authors
identified the primary donor
chlorophyll as one of a few
chlorophyll molecules in the
far-red light–adapted enzymes
that were chemically altered to
shift their absorption spec-
trum. Kinetic measurements
demonstrated that far-red light
is capable of directly driving
water oxidation, despite having
less energy than the red light
used by most photosynthetic
organisms. —MAF
Science, this issue p. 1210
CYTOMETRY
Seeing ghostsIn fluorescence-activated
cell sorting, characteristic
target features are labeled
with a specific fluorophore,
and cells displaying different
fluorophores are sorted. Ota
et al. describe a technique
called ghost cytometry that
allows cell sorting based on the
MACHINE LEARNING
A scene-internalizing computer program To train a computer to “rec-
ognize” elements of a scene
supplied by its visual sensors,
computer scientists typically use
millions of images painstakingly
labeled by humans. Eslami et
al. developed an artificial vision
system, dubbed the Generative
Query Network (GQN), that
has no need for such labeled
data. Instead, the GQN first
uses images taken from differ-
ent viewpoints and creates an
Edited by Stella HurtleyI N SC IENCE J O U R NA L S
RESEARCH
abstract description of the scene,
learning its essentials. Next, on
the basis of this representation,
the network predicts what the
scene would look like from a new,
arbitrary viewpoint. —JS
Science, this issue p. 1204
MAGNETISM
An intrinsic magnetic tunnel junction An electrical current running
through two stacked magnetic
layers is larger if their mag-
netizations point in the same
direction than if they point in
opposite directions. These so-
called magnetic tunnel junctions,
used in electronics, must be
carefully engineered. Two groups
now show that high magneto-
resistance intrinsically occurs in
samples of the layered mate-
rial CrI3 sandwiched between
graphite contacts. By varying
the number of layers in the
samples, Klein et al. and Song
et al. found that the electrical
current running perpendicular
to the layers was largest in high
magnetic fields and smallest
near zero field. This observation
HUMAN IMPACTS
Nocturnal refuge
As the human population grows, there are fewer
places for animals to live out their lives inde-
pendently of our influence. Given our mostly
diurnal tendencies, one domain that remains
less affected by humans is the night. Gaynor
et al. found that across the globe and across mam-
malian species—from deer to coyotes and from
tigers to wild boar—animals are becoming more
nocturnal (see the Perspective by Benítez-López).
Human activities of all kinds, including nonlethal
pastimes such as hiking, seem to drive animals to
make use of hours when we are not around. Such
changes may provide some relief, but they may also
have ecosystem-level consequences. —SNV
Science, this issue p. 1232; see also p. 1185
Human activities are driving many
animals, including coyotes (Canis latrans)
like this one, to become more nocturnal.
Tau binding to tubulin monomers Kellogg et al., p. 1242
Published by AAAS
on June 23, 2018
http://science.sciencemag.org/
Dow
nloaded from
15 JUNE 2018 • VOL 360 ISSUE 6394 1199SCIENCE sciencemag.org
morphology of the cytoplasm,
labeled with a single-color
fluorophore. The motion of cells
relative to a patterned optical
structure provides spatial
information that is compressed
into temporal signals, which
are sequentially measured by
a single-pixel detector. Images
can be reconstructed from this
spatial and temporal informa-
tion, but this is computationally
costly. Instead, using machine
learning, cells are classified
directly from the compressed
signals, without reconstruct-
ing an image. The method
was able to separate morpho-
logically similar cell types in an
ultrahigh-speed fluorescence
imaging–activated cell sorter.
—VV
Science, this issue p. 1246
ANTHROPOLOGY
Mesoamerican turquoise locally sourcedScholars have long assumed
that Aztec and Mixtec tur-
quoise artifacts uncovered in
Mesoamerica were imported
from the American Southwest,
which is home to abundant
turquoise deposits. Thibodeau
et al. analyzed the lead and
strontium isotopic ratios in
38 Mesoamerican turquoise
mosaic tiles (tesserae) from the
Sacred Precinct of Tenochtitlan
and in five tesserae from Mixtec
turquoise mosaics. The isoto-
pic compositions of most of
the samples matched copper
Edited by Caroline Ash
and Jesse SmithIN OTHER JOURNALS
deposits and crustal rocks of
Mesoamerica, suggesting at least
one Mesoamerican region as the
source of this turquoise. —PJB
Sci. Adv. 10.1126/sciadv.aas9370
(2018).
NEUROSCIENCE
Disentangling specific memories Each memory is stored in a
distinct memory trace in the
brain, in a specific population of
neurons called engram cells. How
does the brain store and define
the identity of a specific memory
when two memories interact and
are encoded in a shared engram?
Abdou et al. used optogenetic
reactivation coupled with manipu-
lations of long-term potentiation
to analyze engrams that share
neurons in the lateral amygdala
(see the Perspective by Ramirez).
Synapse-specific plasticity
guaranteed the storage and the
identity of individual memories in
a shared engram. Moreover, syn-
aptic plasticity between specific
engram assemblies was neces-
sary and sufficient for memory
engram formation. —PRS
Science, this issue p. 1227;
see also p. 1182
INFECTIOUS DISEASE
Designer bugs as drugsThe endemic persistence and
outbreaks of Vibrio cholerae
indicate a need for new methods
of control. Mao et al. discovered
that lactic acid production by the
probiotic Lactococcus
lactis rendered the
infant mouse gut hostile
to V. cholerae and
engineered L. lactis to
detect breakthrough
infection. Hubbard et al.
extensively modified a
contemporary V. chol-
erae strain for a live oral
vaccine, which resulted
in an attenuated strain
that could protect infant
rabbits from V. cholerae
challenge within 24
hours of vaccine admin-
istration. —LP
Sci. Transl. Med. 10,
eaao2586, eaap8423 (2018).
Isotope analysis indicates a Central American
source for Aztec turquoise.
Part of the Compact Muon Solenoid at CERN’s Large Hadron Collider
PARTICLE PHYSICS
In the company of top quarks
The coupling of elementary particles to the Higgs boson
is correlated with their masses. For some particles, it
can be measured by observing the decay of the Higgs
into those particles. The top quark, however, is too heavy
for the Higgs to decay into. Therefore, Sirunyan et al.
from the Compact Muon Solenoid Collaboration at the Large
Hadron Collider (LHC) looked at the processes in which the
Higgs boson is produced in conjunction with the top quark
and its antiparticle. By combining the results from the runs at
different center-of-mass energies of proton-proton collisions
at the LHC, they found that such processes indeed occurred
and that the signal strength was consistent with the predic-
tions of the Standard Model of particle physics. —JS
Phys. Rev. Lett. 120, 231801 (2018).
PH
OT
OS
: (L
EF
T T
O R
IGH
T)
NA
TIO
NA
L G
EO
GR
AP
HIC
CR
EA
TIV
E/A
LA
MY
ST
OC
K P
HO
TO
; N
G I
MA
GE
S/A
LA
MY
ST
OC
K P
HO
TO
DA_0615ISIO.indd 1199 6/13/18 11:07 AM
Published by AAAS
on June 23, 2018
http://science.sciencemag.org/
Dow
nloaded from
RESEARCH
sciencemag.org SCIENCE
ALSO IN SCIENCE JOURNALS
IMMUNOLOGY
Modeling memory differentiation in T cells The balance between effector
and central memory T cells
shifts toward the latter as the
number of T cells participating
in immune responses increases.
Polonsky et al. determined the
mechanisms by which T cell
quorum sensing affects memory
differentiation by using live-cell
imaging to track cell proliferation
and differentiation. They found
that the rate of memory CD4+
T cell differentiation is deter-
mined by cell number. This rate
substantially increases above
a threshold number of locally
interacting cells. Mathematical
modeling suggests that the num-
ber of initially seeded cells and
the number of cell divisions are
not critical. Instead, the instan-
taneous number of interacting
cells continuously modulates the
differentiation rate. This is partly
fueled by increased sensitivity
to the cytokines interleukin-2
(IL-2) and IL-6, independent of
any effects on cell proliferation.
—STS
Science, this issue p. 1201
CANCER
Chronic stress as a survival tactic Most patients with pancreatic
ductal adenocarcinoma (PDA)
develop liver metastases after
surgical removal of their primary
tumor. These metastases are
thought to potentially arise from
quiescent disseminated cancer
cells, likely present at the time of
surgery, which evade elimination
by the immune system. Pommier
et al. explored how these
quiescent cells survive by ana-
lyzing mouse models and tissue
samples from patients with PDA.
They found that disseminated
cancer cells do not express a cell
surface molecule that triggers
killing by T cells. This pheno-
typic feature is linked to their
inability to resolve endoplasmic
reticulum stress. When this
stress is resolved, the dissemi-
nated cells begin proliferating
and form metastases. —PAK
Science, this issue p. 1202
NANOTECHNOLOGY
Reconsidering resonator sensing Changes in the frequency
of a nanoscale mechanical
resonator can be used for many
sensing applications, provided
that there is an adequate signal-
to-noise ratio. Normally, this
ratio is improved by creating
resonators with higher quality
factors that “ring” for longer
times. Taking a cue from the
approaches used in atomic
force microscopy, Roy et al.
show that if the thermomechan-
ical noise of the resonator is
well defined, the signal-to-noise
ratio of the frequency shift can
improve by lowering the quality
factor. They used this approach
to demonstrate temperature
sensing with a double-clamped
silicon beam resonator, which
performed better at ambient
pressures than in a vacuum.
—PDS
Science, this issue p. 1203
PLANT SCIENCE
How to make bioactive alkaloidsVinblastine and vincristine are
important, expensive anticancer
agents that are produced by
dimerization of the plant-derived
alkaloids catharanthine and
vindoline. The enzymes that
transform tabersonine into
vindoline are known; however,
the mechanism by which the
scaffolds of catharanthine and
tabersonine are generated has
been a mystery. Caputi et al. now
describe the biosynthetic genes
and corresponding enzymes
responsible. This resolves a
long-standing question of how
plant alkaloid scaffolds are
synthesized, which is important
not only for vinblastine and
vincristine biosynthesis, but
also for understanding the many
other biologically active alkaloids
found throughout nature. —PJH
Science, this issue p. 1235
NEUROSCIENCE
The mechanisms of fear attenuation Surprisingly little is known
about how remote fearful mem-
ories are stored and attenuated.
Khalaf et al. used independent
fear memory attenuation para-
digms, engram-based tagging
techniques, and chemogenetic
tools to alter neuronal activ-
ity (see the Perspective by
Frankland and Josselyn). They
found that a discrete subset of
neurons within an ensemble
is engaged during recall after
memory attenuation, which
correlated with fear reduction.
Memory updating and extinc-
tion mechanisms thus likely
coexist to make this happen.
These findings support the
notion that effective memory
attenuation is mediated by a
rewriting of the original memory
trace of fear toward one of
safety. —PRS
Science, this issue p. 1239;
see also p. 1186
STRUCTURAL BIOLOGY
Tackling microtubule-tau interactions Alzheimer’s disease is a major
cause of death in the elderly.
Disease progression is associ-
ated with the accumulation
of neurofibrillary tangles
composed of tau, a protein
important for neuronal devel-
opment and function. Tangle
formation is preceded by phos-
phorylation events that cause
tau to dissociate from its native
binding partner, microtubules.
Microtubule-tau interactions
have been mysterious. Kellogg
et al. used cryo–electron
microscopy and molecular
modeling to show how tau
interacts with the outer surface
of the microtubule, stapling
together tubulin subunits and
thus stabilizing the polymer. A
key tau amino acid within the
tightly bound segment between
tubulin subunits corresponds
to a clinically relevant site of
tau phosphorylation, explain-
ing the competition between
microtubule interaction and tau
aggregation. —SMH
Science, this issue p. 1242
NEUROSCIENCE
Shifts in brain regions with brain size Brain size among normal
humans varies as much as
twofold. Reardon et al. surveyed
the cortical and subcortical
structure of more than 3000
human brains by noninvasive
imaging (see the Perspective
by Van Essen). They found that
the scaling of different regions
across the range of brain sizes
is not consistent: Some brain
regions are metabolically costly
and are favored in larger brains.
This shifts the balance between
associative and sensorimotor
brain systems in a brain size–
dependent way. —PJH
Science, this issue p. 1222;
see also p. 1184
OCEANS
Environmental DNA tracks rare speciesMarine animals are often elusive,
making it difficult to establish
their presence in a region or to
estimate population sizes. Many
of these animals are also rare,
making them even more difficult
to study. In a Perspective, Pikitch
highlights the advantages of
environmental DNA studies for
detecting rare marine animals,
particularly to aid conservation
efforts. The method is noninva-
sive and highly sensitive, allowing
detection of the recent presence
of animals such as killer whales.
Edited by Stella Hurtley
1200-B 15 JUNE 2018 • VOL 360 ISSUE 6394
DA_0615ISIO.indd 1201 6/13/18 11:07 AM
Published by AAAS
on June 23, 2018
http://science.sciencemag.org/
Dow
nloaded from
SCIENCE sciencemag.org
However, challenges remain, par-
ticularly for estimating population
sizes, where the approach should
prove useful in combination with
more established methods. —JFU
Science, this issue p. 1180
IMMUNOLOGY
Letting thymocytes goDuring the process of T cell
development, thymocytes
must travel from the
cortex of the thymus to the
medulla, where potentially
autoreactive cells are removed
by negative selection. Duke-
Cohan et al. found that mouse
thymocytes lacking the guano-
sine triphosphatase–activating
protein Tagap failed to detach
from the cortex. Given that in
humans, single-nucleotide poly-
morphisms in the gene encoding
TAGAP are associated with
autoimmune disorders, the data
suggest that this protein facili-
tates the trafficking required for
the efficient negative selection of
autoreactive cells. —JFF
Sci. Signal. 11, eaan8799 (2018).
HIV
Spontaneous HIV controllersA small number of HIV-infected
individuals (<1%) can spontane-
ously control HIV in the absence
of antiretroviral therapy. Because
CD4+ and CD8+ T cell responses
are thought to contribute to
protection, HIV-responsive T cell
receptors (TCRs) from these
individuals are of considerable
interest. Galperin et al. examined
how three class II–restricted
TCRs observed in spontane-
ous controllers are capable of
binding a Gag peptide in the
context of multiple HLA-DR mol-
ecules (HLA, human leukocyte
antigen). The authors solved the
structures of several TCR–
peptide–HLA-DR complexes.
The findings suggest that the
ability of these TCRs to recognize
the Gag peptide in the context
of multiple HLA-DR allomorphs
is shaped by extensive contacts
between the TCRs and the
peptide itself. —AB
Sci. Immunol. 3, eaat0687 (2018).
15 JUNE 2018 • VOL 360 ISSUE 6394 1200-C
DA_0615ISIO.indd 1202 6/13/18 11:07 AM
Published by AAAS
on June 23, 2018
http://science.sciencemag.org/
Dow
nloaded from
Designer bugs as drugsLindsey Pujanandez
DOI: 10.1126/science.360.6394.1198-h (6394), 1198-1199.360Science
ARTICLE TOOLS http://science.sciencemag.org/content/360/6394/1198.8
CONTENTRELATED file:/content/sci/360/6394/twis.full
PERMISSIONS http://www.sciencemag.org/help/reprints-and-permissions
Terms of ServiceUse of this article is subject to the
is a registered trademark of AAAS.Sciencelicensee American Association for the Advancement of Science. No claim to original U.S. Government Works. The title Science, 1200 New York Avenue NW, Washington, DC 20005. 2017 © The Authors, some rights reserved; exclusive
(print ISSN 0036-8075; online ISSN 1095-9203) is published by the American Association for the Advancement ofScience
on June 23, 2018
http://science.sciencemag.org/
Dow
nloaded from