Science - USA (2022-01-14)

157-B 14 JANUARY 2022 • VOL 375 ISSUE 6577 science.org SCIENCE

RESEARCH

CELL BIOLOGY

Animal-free research

products

Cell culture is used throughout
biological research, but how cells
are cultured may influence how
they respond to treatments. Cell
culture experiments for applied
research, such as preclinical
studies in human cells and
testing pharmaceuticals and
chemicals, may be affected by
an ingredient used in cell culture
media: fetal bovine serum
(FBS). Although there are many
potential sources of irreproduc-
ibility in research, the use of
animal-derived materials such
as FBS, which are inherently
variable, may lead to altera-
tions in the morphology, growth,
viability, and responses of cells
in culture. How FBS is sourced
also raises ethical concerns. In
a Perspective, van der Valk dis-
cusses the possible issues with
using FBS in cell culture and the
progress with synthetic media as
an alternative. —GKA
Science, abm1317, this issue p. 143

CANCER

Targeting cyclin-

dependent kinases

Cyclin-dependent kinases
(CDKs), in complex with their
cyclin partners, modulate the
transition through phases of the
cell division cycle. Cyclin D–CDK
complexes are important in can-
cer progression, especially for
certain types of breast cancer.
Fa s s l et al. discuss advances in
understanding the biology of
cyclin D–CDK complexes that
have led to new concepts about
how drugs that target these
complexes induce cancer cell
cytostasis. The authors also
suggest possible combinations
to add to the types of cancer
that can be treated and discuss
progress in overcoming resis-
tance to cyclin D–CDK inhibitors
and their possible application to
diseases beyond cancer. —GKA
Science, abc1495, this issue p. 158

CELL BIOLOGY

Mitochondria shed

their SPOTs

Outer mitochondrial membrane

(OMM) function is essential

for cellular health. How mito-

chondria respond to naturally

occurring OMM stress is

unknown. Li et al. show that,

upon infection with the human

parasite Toxoplasma gondii,

mitochondria shed large struc-

tures positive for OMM (SPOTs).

SPOT formation required the

parasite effector TgMAF1 and

its interaction with the host

mitochondrial receptor TOM70

and translocase SAM50. TOM70-

dependent SPOT formation

mediated a depletion of mito-

chondrial proteins and optimal

parasite growth. SPOT-like struc-

tures also formed after OMM

perturbations independently

of infection. Thus, membrane

remodeling is a feature of cel-

lular responses to OMM stress

that Toxoplasma hijacks during

infection. —SMH

Science, abi4343, this issue p. 159

CORONAVIRUS

Persuading people

to mask

Even in places where it is

obligatory, people tend to

optimistically overstate their

compliance for mask wearing.

How then can we persuade more

of the population at large to act

for the greater good? Abaluck et

al. undertook a large, cluster-

randomized trial in Bangladesh

involving hundreds of thousands

of people (although mostly men)

over a 2-month period. Colored

masks of various construc-

tion were handed out free of

charge, accompanied by a range

of mask-wearing promotional

activities inspired by marketing

research. Using a grassroots

network of volunteers to help

conduct the study and gather

data, the authors discovered that

mask wearing averaged 13.3% in

villages where no interventions

took place but increased to

42.3% in those where in-person

interventions were introduced.

Villages where in-person

reinforcement of mask wearing

occurred also showed a reduc-

tion in reporting COVID-like

illness, particularly in high-risk

individuals. —CA

Science, abi9069, this issue p. 160

CORONAVIRUS

Preparing antiviral

defenses

Antiviral drugs are an impor-

tant tool in the battle against

COVID-19. Both remdesivir

and molnupiravir, which target

the severe acute respiratory

syndrome coronavirus 2 (SARS-

CoV-2) polymerase, were first

developed against other RNA

viruses. This highlights the

importance of broad-spectrum

antivirals that can be rapidly

deployed against related emerg-

ing pathogens. Sourimant et al.

used respiratory syncytial virus

(RSV) as a primary indication

in identifying further drugs

that target the polymerase

enzyme of RNA viruses. The

authors explored derivatives of

molnupiravir and identified 4’

fluorouridine (EIDD-2749) as an

inhibitor of the polymerase of

RSV and SARS-CoV-2. This drug

can be delivered orally and was

effective against RSV in mice and

SARS-CoV-2 in ferrets. —VV

Science, abj5508, this issue p. 161

NEURODEGENERATION

Hi-res view of human

Ab42 filaments

Alzheimer’s disease is charac-

terized by a loss of memory and

other cognitive functions and the

filamentous assembly of Ab and

tau in the brain. The assembly of

Ab peptides into filaments that

end at residue 42 is a central

event. Yang et al. used cryo–elec-

tron microscopy to determine

the structures of Ab42 fila-

ments from human brain (see

the Perspective by Willem

and Fändrich). They identified

two types of related S-shaped

filaments, each consisting of

two identical protofilaments.

These structures will inform the

development of better in vitro

and animal models, inhibitors

of Ab42 assembly, and imaging

agents with increased specificity

and sensitivity. —SMH

Science, abm7285, this issue p. 167;

see also abn5428, p. 147

PLANETARY SCIENCE

Terapascal iron-melting

temperature

The pressure and temperature

conditions at which iron melts

are important for terrestrial plan-

ets because they determine the

size of the liquid metal core, an

important factor for understand-

ing the potential for generating

a radiation-shielding magnetic

field. Kraus et al. used laser-

driven shock to determine the

iron-melt curve up to a pressure

of 1000 gigapascals (see the

Perspective by Zhang and Lin).

This value is about three times

that of the Earth’s inner core

boundary. The authors found

that the liquid metal core lasted

the longest for Earth-like planets

four to six times larger in mass

than the Earth. —BG

Science, abm1472, this issue p. 202;

see also abn2051, p. 146

PHYSICS

Gravitational interference

The Aharonov-Bohm effect is a

quantum mechanical effect in

which a magnetic field affects

the phase of an electron wave as

it propagates along a wire. Atom

interferometry exploits the wave

characteristic of atoms to mea-

sure tiny differences in phase as

they take different paths through

the arms of an interferometer.

Overstreet et al. split a cloud of

cold rubidium atoms into two

atomic wave packets about 25

centimeters apart and subjected

one of the wave packets to

Edited by Michael Funk

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