SCIENCE science.org 12 NOVEMBER 2021 • VOL 374 ISSUE 6569 837
after the cell division phase has
ended and while new cells are
enlarging. Asymmetric signal-
ing cascades subsequently
prime the developing leaf with
differing sensitivities to light on
its shady side versus the side
exposed to light. —PJH
Plant Physiol.
10.1093/plphys/kiab410 (2021).
MECHANICAL BONDS
Clipped in place
In rotaxanes, bulky end groups
on a molecular axle keep a
threaded ring from sliding
off. Peris et al. now report a
distinct type of interlocked
compound, which they call a
clippane. The building block
is a tweezer-shaped molecule
in which a polycyclic aromatic
spacer connects two arms
capped by polycyclic aromatics
perpendicular to the spacer.
Two tweezer molecules can
interlock at right angles as the
arms form, but bulky tert-butyl
substituents then prevent them
from sliding back apart. The
clippanes were characterized
in crystalline, solution, and gas
phases and were stable up to
100°C. —JSY
Angew. Chem. Int. Ed.
10.1002/anie.202112513 (2021).LUNAR FORMATION
Did Theia impact
Earth twice?
Geophysical and geochemi-
cal evidence indicates that
the Moon formed from debris
ejected by a giant impact
between Earth and a proto-
planet, referred to as Theia,
which was mostly accreted into
Earth. Simulations support this
model if the impact velocity is
close to the minimum possible,
the mutual escape velocity,but this requires fine tuning.
Asphaug et al. propose that
Theia collided with Earth twice,
first in a grazing “hit-and-run”
that left both objects intact but
modified their orbits, and then,
less than a million years later, in
a giant impact that destroyed
Theia and formed the Moon.
They argue that a range of
initial velocities for the first
collision produced a second
collision at the escape velocity.
—KTS
Planet. Sci. J.
10.3847/PSJ/ac19b2 (2021).SCIENTIFIC WORKFORCE
Exacerbated inequalities
in publishing
During the initial pandemic
lockdowns, academics submit-
ted scientific manuscripts at
an increased rate. Squazzoni
et al. analyzed data on morethan 5 million authors and
referees related to submit-
ted manuscripts for Elsevier
journals between February and
May of 2018–2020 as a way
of investigating the demo-
graphics behind the increased
submissions. Results revealed
an unsurprising gender pat-
tern, with women submitting
fewer manuscripts than men.
Unfortunately, more junior
cohorts of women, likely
women without permanent
positions who are competing
for tenure, promotion, and
grants, experienced the lowest
rates of submission. Perhaps
most upsetting is the finding
that women took on a greater
service responsibility for jour-
nals. Collectively, these data
contribute to a growing number
of studies suggesting that the
pandemic exacerbated cumula-
tive advantages for men. —MMc
PLoS ONE 10.1371/
journal.pone.0257919 (2021).NEUROSCIENCE
Spiny neurons are diverse
The striatum is the major input
nucleus for the basal ganglia.
Striatal information processing
is dependent on cell-type-
specific circuits. Medium spiny
neurons account for most stria-
tal neurons and are traditionally
classified as direct- or indirect-
pathway neurons. However, this
traditional model does not do
justice to the complexity and
diversity of these cells. He et
al. used single-nucleus RNA
sequencing and fluorescence
in situ hybridization to charac-
terize the transcriptional and
anatomical diversity of rhesus
monkey striatal medium spiny
neurons. The authors identi-
fied five distinct subtypes in
the dorsal striatum, whereas
the ventral striatum contained
at least four distinct neuronal
subtypes, including the known
D1 and D2 subtypes. These
neuronal subtypes provide a
framework for studying cell-
type-specific functions during
sophisticated primate behav-
iors. —PRS
Curr. Biol. 10.1016/
j.cub.2021.10.015 (2021).DEVELOPMENTContacts determine
cell fate
D
uring embryonic development,
differentiation processes trans-
form a ball of homogeneous cells
into multicellular complexity. A
neuronal cell acquires its unique
identity because of its neighbors within
the early embryo. Studies have sug-
gested that the size of the contact areas
and the strengths of the signals work in
concert to direct this transformation.
Williaume et al. attempted a quantita-
tive understanding of this process in the
development of the sea squirt, a proto-
chordate model animal. When sea squirt
embryos grow to 32 cells, two cells
adopt a neuronal fate. The authors found
that the strength of the instructional
signal that directs the cells to become
a neuron is proportional to the area of
cell-cell contact. Cells convert the result-
ing gradual signal into a bimodal gene
expression output, which is fine-tuned
by inhibitory signals from the cells’ other
neighbors. —DJ
Dev Cell. 10.1016/j.devcel.2021.09.025 (2021).Development of the protochordate sea squirt Ciona
reveals how cell fate is directed by a cell’s neighbors.