627-B 11 FEBRUARY 2022 • VOL 375 ISSUE 6581 science.org SCIENCE
RESEARCH
CELL BIOLOGY
The making and
removal of a leader
When epithelia are injured, the
remaining cells repair the epithe-
lial sheet by migrating into and
closing the open gap. In many
epithelia, this happens through
a coordinated cell movement
driven by specialized cells called
leaders. However, it is unclear
how epithelial cells become
leaders. Kozyrska et al. reveal
that injury activates the damage
sensor p53, which then pro-
motes the emergence of leaders
through its downstream effector
p21 (see the Perspective by Yun
and Greco). However, leader cells
only live transiently, because
cell competition removes them
once the gap is closed, restoring
epithelial integrity. Localized p53
elevation could drive cell migra-
tion in other contexts in which
damage has been shown to
induce cell migration. —SMH
Science, abl8876, this issue p. 628;
see also abn7411, p. 619
IMMUNOLOGY
CD97 helps DCs fight
going with the flow
A subset of conventional
dendritic cells (DCs) called
cDC2s are found within a
blood-exposed region of the
spleen. These cells efficiently
capture antigens from the
blood and present them to
T cells. However, how cDC2s
sense their location regarding
blood flow remains unclear. Liu
et al. found that in mice, the
N-terminal fragment of the G
protein–coupled receptor CD97
mechanically senses CD55
expressed on red blood cells.
This triggers the Ga 13 signal-
ing required for correct cDC2
positioning. Deficiencies in the
CD55–CD97–Ga 13 pathway
result in a loss of cDC2s into
the circulation and impaired
immune responses to blood-
borne bacteria. —STS
Science, abi5965, this issue p. 629
IMMUNOLOGY
MZ B cells take on
“a-gnaw-ther” role
Marginal zone (MZ) B cells are a
subset of lymphoid tissue–resi-
dent B cells specializing in the
rapid production of polyreactive
immunoglobulin M antibodies.
Schriek et al. found that MZ B
cells can also emulate conven-
tional dendritic cells (cDCs),
which present antigens to T
cells. Complement receptor
2 (CR2) expressed by MZ B
cells recognizes complement
component 3 (C3) bound to
peptide-loaded major histo-
compatibility complex class
II (pMHC II) molecules on the
surface of cDCs. MZ B cells can
then “nibble” pMHCII–C3 com-
plexes from cDCs and display
them on their own membranes
in a process called trogocytosis.
A ubiquitin ligase, MARCH1,
limits the damage to cDCs by
regulating the levels of pMHCII–
C3 complexes expressed on the
surface of cDCs. —STS
Science, abf7470, this issue p. 630CELL BIOLOGY
A missing motor
in human meiosis
Chromosomal errors in human
eggs are a leading cause of mis-
carriages and infertility. These
errors result from chromo-
some missegregations during
the maturation of oocytes into
eggs. Chromosome segrega-
tion is driven by the spindle,
a macromolecular machinery
that pulls chromosomes apart.
However, human oocytes often
assemble unstable spindles,
favoring chromosome misseg-
regations. So et al. discovered
that human oocyte spindles
are unstable because they are
deficient in the molecular motor
KIFC1, which stabilizes spindles
in other mammalian oocytes
and in cancer cells. By intro-
ducing exogenous KIFC1, the
authors were able to increase
the fidelity of spindle assemblyand chromosome segregation in
human oocytes. —SMH
Science, abj3944, this issue p. 631NEUROSCIENCE
How to remember
a sequence of events
How is serial order mentally
encoded and stored in memory?
Xie et al. addressed this ques-
tion using two-photon calcium
imaging to simultaneously
record thousands of prefrontal
neurons in monkeys performing
a delayed visuospatial sequence
reproduction task. The animals
saw a sequence of three loca-
tions and, after a delay, made a
saccade to the corresponding
locations in the appropriate
order. The data obtained using
a mathematical decomposition
technique support a new and
simple type of model: a static
population code with distinct
and near-orthogonal subspaces
for each rank in the sequence,
all superimposed in the same
overlapping groups of prefrontal
neurons. These results open an
important and new perspective
on understanding sequence rep-
resentations in the brain. —PRS
Science, abm0204, this issue p. 632PIEZOELECTRICS
A surprising way
to detect strain
Piezoelectric materials usually
rely on their crystal structure
alone to create electrical charge
in response to strain. This
makes the materials attractive
for a variety of sensing appli-
cations. Park et al. present a
different strategy by introducing
gadolinium into non-piezoelec-
tric cerium dioxide (see the
Perspective by Li). This approach
also creates oxygen vacancies
that turn the material into one
with a frequency-dependent
piezoelectric effect under a
static electric field. The size
of the effect is similar to that
of commercial piezoelectricmaterials, and the strategy
should work more generally for a
wide class of materials. —BG
Science, abm7497, this issue p. 653;
see also abn2903, p. 618MATERIALS SCIENCE
Naturally strong but light
Cellular solids such as foams
or honeycombs can exhibit
excellent stiffness or toughness
with minimal weight. Yang et
al. examined ossicles, calcare-
ous skeletal elements from the
skeletons of knobby starfish (see
the Perspective by Hyde and
Meldrum). The authors show
that the structure consists of
a dual-scale microlattice with
both an atomic-level calcite and
a micro-level diamond-triply
periodic minimal surface, as well
as gradients in composition and
atomic level defects. It is these
combined features that enhance
the damage tolerance of the
ossicles under compression,
giving the starfish remarkable
specific energy absorption capa-
bilities. —MSL
Science, abj9472, this issue p. 647;
see also abn2717, p. 615Y CHROMOSOME ORIGINS
Evolutionary models
of the Y chromosome
A major question in evolution-
ary genetics is how and why
sex chromosomes form from
otherwise undifferentiated
chromosomes. The sexual
antagonism theory posits that
antagonistic alleles that benefit
males but harm females lie on
the same chromosome as an
initial male-determining locus,
resulting in selection against
recombination. Lenormand and
Roze have developed a four-step
model proposing an alterna-
tive evolutionary path (see the
Perspective by Muralidhar and
Veller). Chance fixation of an
inversion leads to recombina-
tion arrest on a portion of the Y
chromosome. This triggers diver-
gence of X and Y cis-regulators,Edited by Michael FunkALSO IN SCIENCE JOURNALS