Science - USA (2020-01-17)

sciencemag.org SCIENCE

RESEARCH

MICROBIOLOGY

A communicable

component?

Noncommunicable diseases—
such as metabolic disorders,
cardiovascular disease, and
cancer—are increasingly preva-
lent. Data suggest that these
disorders are often associated
with dysregulated gut microbiota
(dysbiosis). In a Perspective,
Finlay et al. propose that
dysbiosis may be transmissible
between individuals and that the
etiology of noncommunicable
diseases may actually have a
communicable component.
Although much more research
is needed to ascertain whether
microbes have a causative role in
noncommunicable diseases, it is
an important avenue of research
that could have substantial
implications for disease preven-
tion and treatment. —GKA
Science, this issue p. 250

QUANTUM MATERIALS

An overview of an exotic

type of liquid

Materials with interacting
quantum spins that neverthe-
less do not order magnetically
down to the lowest temperatures
are candidates for a materials
class called quantum spin liquids
(QSLs). QSLs are characterized
by long-range quantum entan-
glement and are tricky to study
theoretically; an even more
difficult task is to experimen-
tally prove that a material is a
QSL. Broholm et al. take a broad
view of the state of the field and
comment on the upcoming chal-
lenges. —JS
Science, this issue p. 263

T CELLS

A VISTA on naïve

T cell fate

T cell quiescence and tolerance
restrain the immune system
from becoming overactive
and attacking healthy tissue.

Negative checkpoint regulators

normally limit T cell responses to

help safeguard against condi-

tions such as autoimmunity.

ElTanbouly et al. report that

the checkpoint regulator VISTA

(V-type immunoglobulin domain-

containing suppressor of T cell

activation) restricts early stages

of T cell activation by shaping

the inherent heterogeneity of the

naïve CD4+ T cell compartment

to one that is more uniformly

quiescent and silent (see the

Perspective by Brown and

Rudensky). Therapeutic target-

ing of VISTA using an agonistic

antibody in mice curbed the

development of graft-versus-

host disease and promoted the

death of naïve T cells abnormally

activated by self-antigen. VISTA

thus represents a distinctive

immunoregulatory molecule that

controls naïve T cell function

by maintaining quiescence and

peripheral tolerance. —PNK

Science, this issue p. 264;

see also p. 247

ADVANCED IMAGING

Visualizing whole

cells at many scales

Cells need to compartmentalize

thousands of distinct proteins,

but the nanoscale spatial

relationship of many proteins to

overall intracellular ultrastruc-

ture remains poorly understood.

Correlated light and electron

microscopy approaches can

help. Hoffman et al. combined

cryogenic super-resolution

fluorescence microscopy and

focused ion beam–milling scan-

ning electron microscopy to

visualize protein-ultrastructure

relationships in three dimen-

sions across whole cells. The

fusion of the two imaging

modalities enabled identifica-

tion and three-dimensional

segmentation of morphologically

complex structures within the

crowded intracellular environ-

ment. The researchers observed

unexpected relationships within

a variety of cell types, including

a web-like protein adhesion

network between juxtaposed

cerebellar granule neurons.

—SMH

Science, this issue p. 265

PALEONTOLOGY

A finer record

of biodiversity

We have pressing, human-

generated reasons to explore

the influence of environmental

change on biodiversity. Looking

into the past can not only

inform our understanding of

this relationship but also help us

to understand current change.

Paleontological records depend

on fossil availability and predic-

tive modeling, however, and thus

tend to give us a picture with

large temporal jumps, millions of

years wide. Such a scale makes

it difficult to truly understand the

action of environmental forces

on ecological processes. Enabled

by a supercomputer, Fan et

al. used machine learning to

analyze a large marine Paleozoic

dataset, creating a record with

time intervals of only ~26,000

years (see the Perspective by

Wagner). This fine-scale resolu-

tion revealed new events and

important details of previously

described patterns. —SNV

Science, this issue p. 272;

see also p. 249

OPTICS

Enhancing optical

nonlinearity

Intense pulses of light interact-

ing with a dielectric material

can induce optical nonlinear

behavior, whereby the frequency

of the output light can be

doubled or tripled or excited to

even higher harmonics of the

input light. Usually this interac-

tion is weak and occurs over

many thousands of wavelengths,

typically requiring the combina-

tion of bulk volumes of material

with a confining cavity. Using a

mechanism of light confinement

called bound states in the

continuum, Koshelev et al. show

that enhanced second-harmonic

generation can be obtained in

nanoscale subwavelength cylin-

ders of a dielectric material. The

results on these optical nano-

antennas offer a platform for

developing integrated nonlinear

nanophotonic devices. —ISO

Science, this issue p. 288

ORGANIC CHEMISTRY

Sourcing nitrogen from

nitromethane

Nitromethane is produced in

bulk quantities for use as a

solvent. Its applications as a

reagent have focused mainly on

the acidity of the methyl protons

en route to modifying the carbon

center. Liu et al. now report

an alternative protocol that

activates the nitrogen center to

produce an aminating agent. An

in situ reductive reaction with

triflic anhydride, formic acid, and

acetic acid yields an acetylated

hydroxylamine, characterized

by mass spectrometry. This

nitrogen donor conveniently

transforms a variety of ketones

and aldehydes into amides.

—JSY

Science, this issue p. 281

MARTIAN ATMOSPHERE

Water reaches Mars’

upper atmosphere

Mars once hosted abun-

dant water on its surface but

subsequently lost most of it

to space. Small amounts of

water vapor are still present

in the atmosphere, which can

escape if they reach sufficiently

high altitudes. Fedorova et al.

used data from the ExoMars

Trace Gas Orbiter spacecraft

to determine the distribution

of water in Mars’ atmosphere

and investigate how it varies

over seasons. Water vapor is

sometimes heavily saturated,

and its distribution is affected by

the planet’s large dust storms.

Edited by Michael Funk

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262-B 17 JANUARY 2020 • VOL 367 ISSUE 6475

Published by AAAS