Science - 31 January 2020

sciencemag.org SCIENCE

RESEARCH

NEUROSCIENCE

A learning mechanism in

the striatum

An intriguing characteristic of the
striatum is the random spatial
distribution and high degree of
intermingling between expression
of dopamine receptor types 1
(D1) and 2 (D2) within striatal
projection neurons (SPNs). The
resulting highly entropic mosaic
extends through a homogeneous
space and is mostly devoid of
histological boundaries. The rules
established locally by D1- and
D2-expressing SPNs (D1-SPNs
and D2-SPNs) are thus likely
critical in defining how functional
territories develop throughout
the striatum. Matamales et al.
found that activated D2-SPNs
access and modify developing
behavioral programs encoded by
regionally defined ensembles of
transcriptionally active D1-SPNs.
This process is slow because
it depends on the molecular
integration of additive neuro-
modulatory signals. However,
with time, it creates the regional
functional boundaries that are
necessary to identify and shape
specific learning in the striatum.
—PRS
Science, this issue p. 549

SYSTEMS BIOLOGY

Single-cell protein profiling
Single-cell DNA and RNA
sequencing can describe
numerous aspects of cell state,
but such techniques cannot
assess the functional effec-
tors of cells: proteins. In a
Perspective, Slavlov discusses
the advances in single-cell mass
spectrometry techniques that
allow protein profiling, includ-
ing characterization of protein
modifications and potentially
complex composition and sub-
cellular localization. Although
there are limitations to this
emerging technology, single-
cell proteomics may add to the
characterization of cellular com-
ponents and provide functional
information about signaling

networks in homeostasis and

disease. —GKA

Science, this issue p. 512

CANCER IMMUNOTHERAPY

Presurgical immune

checkpoint blockade

Checkpoint blockade immu-

notherapy using antibodies

that inhibit the programmed

cell death 1 (PD-1) or cytotoxic

T lymphocyte–associated

protein 4 (CTLA-4) pathways

has resulted in unprecedented

clinical outcomes for certain

cancers such as melanoma.

Topalian et al. review advances in

neoadjuvant (presurgical) immu-

notherapy as an important next

step for enhancing the response

of early-stage tumors to immune

checkpoint blockade. They high-

light the mechanistic rationale

for neoadjuvant immunotherapy

and recent neoadjuvant clinical

trials based on anti–PD-1 or

anti–PD-1 ligand 1 (anti–PD-L1)

therapy. Pathological assess-

ment criteria that may provide

early on-treatment biomarkers

to predict patient response are

also discussed. —PNK

Science, this issue p. 525

NEUROSCIENCE

Monosomes translate

proteins in neurons

Like all other cells, neurons use

different proteins to process infor-

mation and respond to stimuli. To

meet the huge demands for new

proteins in their large and com-

plex cell volume, neurons have

moved the protein templates—

messenger RNAs (mRNAs)—and

the protein synthesis machines—

ribosomes—out to synapses to

make proteins locally. During

protein synthesis, multiple

ribosomes can form a structure

known as a polysome, which

produces multiple protein

copies from a single mRNA.

Working in rodent preparations,

Biever et al. found that solitary,

mRNA-associated ribosomes, or

monosomes, are a substantial

source of proteins in neuro-

nal processes. Many synaptic

proteins are made on single

ribosomes, which may solve the

problem of limited space in tiny

synaptic compartments. —SMH

Science, this issue p. 526

CELL BIOLOGY

ER regulates stress

granule fission

A hallmark of eukaryotic cells is

the ability to compartmentalize

essential reactions into mem-

brane-bound and membraneless

organelles. Membrane-bound

organelles form networks

through transport vesicles and

interorganellar contact sites. The

endoplasmic reticulum (ER) has

emerged as a network hub and

forms physical connections with

nearly every membrane-bound

organelle. Lee et al. now identify

another class of ER contact sites

that appear to help regulate

the biogenesis and fission of

membraneless ribonucleopro-

tein (RNP) granules (see the

Perspective by Kornmann and

Weis). Live-cell fluorescence

microscopy of human cells

revealed that ER tubule dynam-

ics are spatially and temporally

coupled to the fission site of two

types of RNP granules, process-

ing bodies (P-bodies) and stress

granules. —SMH

Science, this issue p. 527;

see also p. 507

CATA LYS I S

Charging up cobalt for

hydroformylation

Hydroformylation reactions are

applied at massive scale in the

chemical industry to transform

olefins into aldehydes. The

original catalysts were neutral

cobalt complexes. Hood et

al. now report that positively

charged cobalt complexes,

stabilized by chelating phos-

phine ligands, show higher

activities at lower pressures

than their neutral counterparts,

approaching the activities of

precious rhodium catalysts.

These charged catalysts are

particularly adept at accelerating

the reactions of internal olefins

while avoiding decomposition.

Spectroscopic studies implicate

the involvement of 19-electron

intermediates in the catalytic

cycle. —JSY

Science, this issue p. 542

NANOMATERIALS

Growing coaxial

nanotubes

Heterostructures of highly

crystalline two-dimensional

materials such as graphene,

hexagonal boron nitride (hBN),

and molybdenum disulfide

(MoS 2 ) are now routinely

assembled from films or grown

as layers. Xiang et al. report

the growth of one-dimensional

analogs of these heterostruc-

tures on single-walled carbon

nanotubes (SWCNTs) through a

chemical vapor deposition (see

the Perspective by Gogotsi and

Yakobson). Single-crystalline

monolayers or multilayers

of hBN or MoS 2 were grown

that maintained the electrical

conductivity of the SWCNT. A

monolayer of MoS 2 was grown

on a trilayer of hBN that encap-

sulated a SWCNT. —PDS

Science, this issue p. 537;

see also p. 506

BEE HEALTH

Inducing immune

bee genes

Honey bees are prone to

parasitism by the Va r ro a mite,

which is a vector for several bee

pathogens. However, honey bees

are also host to the symbiotic

gut bacterium Snodgrasella alvi.

Leonard et al. engineered S. alvi

to produce double-stranded

RNA (dsRNA)—a stimulus for

insect RNA interference defense

responses—from a plasmid con-

taining two inverted promoters

Edited by Michael Funk

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524-B 31 JANUARY 2020 • VOL 367 ISSUE 6477

Published by AAAS