Science - USA (2022-05-27)

TRANSCRIPTION

Lampbrush loops

in the nucleus

RNA polymerase II in the

nucleus transcribes the instruc-

tion in a gene into a messenger

RNA. In any given moment, it

has been proposed that thou-

sands of genes are transcribed

in transcription factories. In

these factories, RNA poly-

merases II remain stationary,

and active genes approach

the enzyme to be transcribed.

Contrary to this hypothesis,

Leidescher et al. has found that

very long but highly expressed

genes form transcription loops

decorated by RNA polymerase

II. The enzyme moves along

the gene axis, carrying newly

synthesized messenger RNAs

undergoing co-transcriptional

splicing. These transcription

loops look like lateral loops

of lampbrush chromosomes

observed more than 100 years

ago in the oocytes of many non-

mammalian animals. It is not

yet clear how general this mode

of transcription is or how it

contributes to nuclear organiza-

tion. —DJ

Nat. Cell Biol. 24 , 327 (2022).

CONSERVATION

A new hope

The vast negative impact of

humanity on other species

tends to lead to extinction.

However, our manipulations

have also led to a wide variety

of less-recognized species

alterations. Chinese giant

salamanders (Andrias spp.) are

the victims of a combination of

incomplete knowledge, com-

mercial enterprise, and poorly

informed conservation actions.

This genus is now mostly

represented by thousands of

individuals in farms (they are

consumed for food and used

in traditional Chinese medi-

cine). Most of these animals

are hybrids of as many as eight

previously unrecognized spe-

cies, and many of these hybrids

sciencemag.org SCIENCE

RESEARCH | IN SCIENCE JOURNALS

survival and repertoire diversity.

Quiescence is actively maintained

by T cell–myeloid cell cross-talk

through cell surface CD8a–PILRa

interactions. Disruption of this

interaction leads to spontane-

ous activation and subsequent

loss of naïve and memory CD8+ T

cell pools in peripheral lymphoid

organs. —STS

Science, aaz8658, this issue p. 996

PHYSIOLOGY

Joints degenerate

with a lncRNA

Nuclear factor kB (NF-kB)

signaling contributes to the

development and progression

of osteoarthritis by promoting

cartilage degradation and joint

inflammation. Tang et al. found

that the long noncoding RNA

(lncRNA) PILA exacerbated

inflammation-induced joint dam-

age in osteoarthritis. In human

articular chondrocytes, PILA

stimulated the modification of

the RNA helicase DHX9 by the

protein arginine methyltrans-

ferase PRMT1, which resulted in

increased levels of an upstream

activator of NF-kB. Expression of

PILA in mouse knee joints elicited

spontaneous cartilage degrada-

tion and enhanced experimentally

induced osteoarthritis. —AMV

Sci. Signal. 15 , eabm6265 (2022).

PLANETARY SCIENCE

Tracking the greenhouse

effect on Mars

Mars was far warmer and wetter

in the past than it is today, but the

when and why of this transition

is actively debated. One popular

model holds that this transition

was driven by a loss of atmo-

spheric carbon dioxide (CO 2 ),

lowering the radiation-forcing

effect of that greenhouse gas.

Previous studies indicated that

other greenhouse gases may

also have played a role, but their

importance remains unclear. Kite

et al. tracked the spatial distribu-

tion of rivers through time on

Mars using remote sensing data

as a proxy for how the green-

house effect may have changed.

The authors were able to con-

strain climate models that provide

insights into the relative impor-

tance of CO 2 forcing and forcing

by other gases during the wet-dry

transition. Unexpectedly, their

models suggest that a reduc-

tion in non-CO 2 gases may have

played the primary role in cooling

and drying the planet. —KVH

Sci. Adv. 10.1126/

sciadv.abo5894 (2022).

MATERIALS SCIENCE

Untwisted heterobilayers

Stacking two-dimensional

materials can lead to a range of

interesting and useful properties.

For example, the emergence of

piezoelectricity and ferroelec-

tricity can occur by twisting the

layers relative to each other.

Rogée et al. used a different

strategy for obtaining these

sorts of properties by stacking

alternating layers of molybdenum

disulfide and tungsten disulfide,

which breaks symmetry without

requiring twisting. The authors

show that these vapor-deposited

heterobilayers can be made into

a ferroelectric tunnel junction

device. —BG

Science, abm5734, this issue p. 973

Edited by Caroline Ash

and Jesse Smith

PHOTOS (LEFT TO RIGHT: NASA/JPLCALTECH/UNIV. OF ARIZO

MORPHOGENESIS

From ordered cells

to patterned tissues

I

n developing animal skin, cells

self-organize to generate different

structures such as sweat glands, hair,

and feather follicles. But what comes

first, patterning or gene expression?

Palmquist et al. show that follicle forma-

tion in bird skin depends on mechanical

self-organization. The authors made a

reconstituted system of embryonic avian

dermal cells on a substrate that mimics

the extracellular matrix. In this model,

dermal cells initially formed a ring but

separated into regularly spaced aggre-

gates because of feedback between cell

contractility and rearrangements of the

extracellular membrane that further

align the cells. —VV and SMH

Cell 10.1016/j.cell.2022.04.023 (2022).

IN OTHER JOURNALS

Water shaped the surface geography of Mars, seen here in a high-resolution

satellite image, in different ways as the planet cooled.

Mechanical forces in embryonic bird skin

determine the formation of feather follicles.

958 27 MAY 2022 • VOL 376 ISSUE 6596