988 4 MARCH 2022 • VOL 375 ISSUE 6584 science.org SCIENCE
RESEARCH | IN SCIENCE JOURNALS
observed in embryonic stem
cells (ESCs). Gene bivalency
has been widely thought to
be a priming mechanism
to facilitate gene induction
kinetics during differentiation.
However, loss of H3K4me3 at
bivalent promoters by delet-
ing the methyltransferase
Mll2 has little effect on gene
induction kinetics. Zhang et
al. report that the protein
BEND3 is required for optimal
H3K27me3 occupancy at
hundreds of bivalent promot-
ers, and deletion of the Bend3
gene in ESC causes premature
activation of bivalent genes
and the failure of differen-
tiation. The authors propose
BEND3-mediated Polycomb
stabilization as a mechanism to
prevent premature activation
and to safeguard the differen-
tiation process. —DJ
Science, abm0730, this issue p. 1053
ASTEROIDS
Obtaining and returning
samples of Ryugu
The Hayabusa2 mission
investigated the nearby carbo-
naceous asteroid Ryugu and
collected samples for return to
Earth. Tachibana et al. describe
Hayabusa2’s second sample col-
lection, which picked up material
that was excavated from Ryugu’s
subsurface by an earlier impact
experiment. By analyzing footage
from both touchdown events,
the authors determined the mor-
phological properties of small
pebbles on the asteroid. After
the sample return capsule was
opened on Earth, they found that
SOCIOLOGY
Developing infant brains
by reducing poverty
The Baby’s First Years study
is a randomized controlled
trial that investigates whetherpoverty reduction can
cause noticeable changes in
children’s early brain develop-
ment. After giving either $333
per month or $20 per month
to 1000 low-income mothers
from four different metro areasthe chambers contained pebbles
with properties consistent with
the touchdown locations, indicat-
ing that they are representative
samples of Ryugu’s surface and
subsurface. —KTS
Science, abj8624, this issue p. 1011CORONAVIRUS
Omicron’s defenses
and vulnerabilities
The Omicron variant of severe
acute respiratory syndrome
coronavirus 2 quickly became
dominant across the world
partly because of its ability
to evade existing immune
defenses. Yin et al. provide
structural data showing how
the Omicron spike protein
maintains and even strength-
ens binding to the human ACE2
receptor, whereas binding to
most existing therapeutic anti-
bodies is inhibited. JMB2002,
an antibody that has completed
phase 1 clinical trials, effec-
tively neutralizes Omicron as
well as variants Alpha, Beta,
and Gamma, but not Delta. A
structure shows the basis for
this breadth. —VV
Science, abn8863, this issue p. 1048QUANTUM SIMULATION
Time crystal in
quantum computer
One of the most promising
applications of quantum com-
puters is to simulate quantum
phenomena that are difficult
to efficiently simulate using
classical computers. A time
crystal is a unique quantum
phase of matter that repeats
in time and never reaches
thermal equilibrium. Frey and
Rachel used a state-of-the-art
quantum computer involving
57 qubits to realize this state,
and their experiments show
that the true dynamics of a
discrete time crystal appear in
the quantum computer. This
study highlights the power of a
quantum computer to explore
quantum phenomena for siz-
able quantum systems. — RO
S c i. Ad v. 10.1126/
sciadv.abm7652 (2022).A small pebble returned from
the asteroid Ryugu to Earth by
the Hayabusa2 mission
Extinct giant lemurs helped distribute the fruit
of extant palm trees in Madagascar.Edited by Caroline Ash
and Jesse SmithIN OTHER JOURNALS
PHOTOS: (LEFT TO RIGHT TACHIBANAET AL.; WORLD HISTORY ARCHIVE/ALAMY STOCK PHOTOPLANT ECOLOGYIsland seed dispersal
M
adagascar’s large fruit eaters, including elephant
birds and giant lemurs, went extinct about 1000
years ago. As a result, seed dispersal for some
large-fruited plant species is inefficient. The modern
distributions of some plant species may therefore
reflect past distributions of extinct animals. Méndez et al.
examined the roles of environmental conditions and extinct
and extant frugivores on the occurrences of 190 palm spe-
cies in Madagascar. Living frugivores, including birds and
lemurs, had the strongest influence on palm composition
across the island. However, palm distributions still showed a
small but distinct signature of extinct megafauna dispersal.
—BEL Ecography 10.1111/ecog.05885 (2022).