654-B 16 AUGUST 2019 • VOL 365 ISSUE 6454 sciencemag.org SCIENCE
RESEARCH
MITOCHONDRIA
Putting a price
on the powerhouse
Mitochondria—the so-called
powerhouse of the cell—are
derived from bacterial endo-
symbionts. This history provides
opportunities and challenges
for their host cells, particularly
metazoans, including humans.
Youle reviews the interplay
between host and mitochon-
drial biology and highlights
how mitochondrial ancestry
has influenced innate immune
responses. Keeping mitochon-
dria both healthy and in check
is key to organismal health and,
when perturbed, leads to a
variety of pathologies, including
Parkinson’s disease and inflam-
mation. —SMH
Science, this issue p. 655
ASTROCHEMISTRY
Enhanced abundance
of primordial HeH+
Though only recently detected
in space, the helium hydride ion
(HeH+) is thought to be the first
molecule ever to have formed
in the early Universe. Novotný
et al. report state-specific rate
coefficients for the dissociative
reaction of HeH+ with electrons,
obtained using a cryogenic ion
storage ring combined with a
merged electron beam (see
the Perspective by Bovino and
Galli). They detect substantial
rotational dependence and a
decrease of the rates for the
lowest states of HeH+, far below
the values listed in astrochem-
istry databases and those
previously applied in early-
Universe models. These results
suggest high abundance of this
important primordial molecule
at redshifts of first star and
galaxy formation. —YS
Science, this issue p. 676;
see also p. 639
SUPERCONDUCTIVITY
An unusual
superconductor
In conventional, and in many
unconventional, supercon-
ductors, the electrons that
form Cooper pairs have spins
pointing in opposite directions.
An applied magnetic field can
easily “break” such pairs—and
destroy superconductivity—by
aligning both spins in the same
direction. In contrast, spin-
triplet superconductors are
much more resilient to mag-
netic fields. Very few candidates
for such materials have been
discovered. Ran et al. add to
this select group by observ-
ing signatures of spin-triplet
superconductivity, including a
very large and anisotropic upper
critical magnetic field, in the
material UTe 2. Because spin-
triplet superconductors may
naturally exhibit topological
superconductivity, this material
may also be of interest in quan-
tum computing. —JS
Science, this issue p. 684SOLAR CELLS
Strong perovskite
interfaces
The weak bonding in the crystal
lattice of hybrid perovskites
used in solar cells promotes
surface decomposition and
interferes with the formation of
stable heterostructures with the
charge carrier layers. Y. Wang et
al. show that strong bonds are
formed between lead and both
chlorine and oxygen atoms in a
film with a lead-rich surface and
a chlorinated graphene oxide
layer. This interface was used
with common hole-transporting
materials to fabricate solar cells
that maintained 90% of their
initial efficiency of 21% after
operation at 60°C for 1000
hours. —PDS
Science, this issue p. 687NEUROSCIENCE
A newly discovered cell
type for pain perception
Pain has been thought to be initi-
ated by activation of free nerve
endings without end organs in the
skin. In contrast to this paradigm,
Abdo et al. discovered a previ-
ously unknown meshlike organ
covering the skin that senses
dangerous environmental stimuli
(see the Perspective by Doan and
Monk). This organ is built from
specialized glial cells located in
the epidermal-dermal border
and is sufficient and required
for initiation of mechanical pain
transduction. —PRS
Science, this issue p. 695;
see also p. 641CELL BIOLOGY
Active migration renews
gut epithelia
Epithelial tissues are continu-
ously renewed throughout adult
life, and the gut epithelium is
the fastest self-renewing tissue
in mammals. Over 3 days or so,
epithelial cells migrate from the
crypts, where they are born, to
the tips of the villi, where they
die. It is commonly believed that
migration is strictly passive,
driven by mitotic pressure in
crypts—as cells divide, they
push their neighbors upward.
Krndija et al. now challenge this
concept and show that cells
migrate actively, using actin-rich
basal protrusions oriented in the
direction of migration (see the
Perspective by Jansen). —SMH
Science, this issue p. 705;
see also p. 642IMMUNE SIGNALING
A nuclear sensor
of viral DNA?
A signaling pathway in eukary-
otes known as cGAS–STING
recognizes the presence of
cytosolic DNA, which alerts the
immune system to viral infection
or cellular damage. However, themajority of DNA viruses direct
their genomic DNA into nuclei,
suggesting that nuclear-specific
sensing is also needed. L. Wang et
al. find that during herpes simplex
virus–1 infection, heterogeneous
nuclear ribonucleoprotein A2B1
forms a complex with viral DNA,
homodimerizes, and is demeth-
ylated. These events result in
translocation of the complex to
the cytosol and activation of the
immune system through type I
interferon signaling. Additionally,
the complex promotes
N^6 -methyladenosine modification
and translocation of cGAS–
STING–related mRNAs after DNA
virus infection, further amplifying
the immune response. —STS
Science, this issue p. 656ENVIRONMENT
Watch out for river
nutrient imbalances
Input of excess nutrients, such
as nitrogen and phosphorus,
into a body of water can cause
excessive growth of algae. This
eutrophication has occurred in
fresh waters all around the world
as a result of human activities.
Efforts to reduce nutrient inputs
have been effective, but as
Ibáñez and Peñuelas explain in
a Perspective, greater reduc-
tions in phosphorus than in
nitrogen are leading to nutrient
imbalances that can also have
negative ecological impacts.
Most studies have focused on
lakes or smaller streams, but
recent work is beginning to
explore the profound effects of
these changes in rivers. —JFU
Science, this issue p. 637CANCER IMMUNOLOGY
Enhanced inhibitor
Epidermal growth factor recep-
tor tyrosine kinase inhibitors
(EGFR TKIs) block oncogenic
receptor signaling and are
used as a first-line treatment
for EGFR-mutated non–small
cell lung cancer. Resistance
to EGFR TKIs, including theEdited by Michael Funk
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