Science 28Feb2020

988 28 FEBRUARY 2020 • VOL 367 ISSUE 6481 sciencemag.org SCIENCE

PHOTO: ISTOCK.COM/STEVEALLENPHOTO

W

ith one phone call, Magdalena

Zernicka-Goetz’s life as a scien-

tist collided with her personal

life in the most dramatic way. As

Zernicka-Goetz stood at her desk

at the University of Cambridge, a

genetic counselor explained that some cells

derived from the placenta supporting her fe-

tus carried a serious chromosomal anomaly.

But her knowledge of how embryos develop

suggested that the fetus might be able to ex-

clude the cells with the genetic abnormality

or that it may not contain the damaged DNA

at all. Further testing confirmed that the fe-

tus was genetically normal, and her son was

born in perfect health. “At that time,” how-

ever, she writes, “I couldn’t possibly be sure.”

In The Dance of Life, Zernicka-Goetz

and science writer Roger Highfield weave

Zernicka-Goetz’s personal memoir together

with an accessible introduction to contem-

porary mouse and human embryonic re-

search and with a discussion of the clinical,

ethical, and societal implications of this re-

search and related areas. This is a lofty goal

for a relatively slim volume, and it succeeds

better in some parts than in others.

Developmental biologists have studied

the progression of the fertilized mammalian

egg through its early cleavage divisions to

the formation of the 100-cell blastocyst for

many years. Such studies have suggested

that there is a gradual segregation of cell

fate influenced by cell polarity, cell position

(inside or outside), and mechanical signals

and that the embryo is able to regulate for

loss, gain, or rearrangement of cells right

up to the blastocyst stage. However, none of

these studies really addressed the question

of whether there might be asymmetries in

the egg or early embryo that could bias later

cell fate.

Zernicka-Goetz, who has long been fasci-

nated with patterning in the early embryo,

took on this challenge when she began

her own research lab at the University of

Cambridge. She describes her work on defin-

ing early asymmetries in the mouse embryo

DEVELOPMENTAL BIOLOGY

By Janet Rossant

When life meets research

and their role in informing later develop-

ment in careful detail, recounting how she

used tools such as cell marking, live imag-

ing, and gene manipulation to determine

that early blastomeres show a bias toward

different regions and cell types of the blas-

tocyst. However, other researchers—using

different techniques—found less

evidence for early differences,

leading to some vigorous de-

bates, as described in the book.

This controversy compelled re-

searchers who had set aside work

on the early embryo to reenter

the fray, bringing new tools and

ideas. And, although it is still not

clear what initiates asymmetries

after fertilization, it is increas-

ingly clear that by the four-cell

stage, there are differences in

chromatin modification and transcription

factor activity among the cells that, while not

permanently specifying cell fate, may bias

their future lineage contributions.

The book does not shy away from discuss-

ing the moral and ethical implications inher-

ent in such research, tackling prenatal testing,

the ongoing quest to create synthetic embryos,

and the question of whether human embryos

should be used in research. “Although an

early embryo is not a person, I believe that

it deserves protection, and I fully appreciate

that balancing that protection with scientific

research is not easy,” writes Zernicka-Goetz of

the latter issue. Her attitude has been to tread

carefully, weighing potential concerns against

potential value to humanity. “I believe in tak-

ing a measured approach to enable research

that is fully consistent with our values.”

The authors do their best to describe ex-

periments on the early embryo and stem

cell–based embryo models in simple terms,

but the book would have been greatly en-

hanced by the inclusion of some illustra-

tions. The early embryo is truly beautiful,

especially when the complexity of gene ex-

pression patterns is revealed by fluorescent

imaging. Also, some of the science may be

hard for the uninitiated to follow. In the

fifth chapter, for example, the embryonic

cleavage divisions from one cell

to four cells are described using

a two-tone soccer ball analogy.

This takes two full paragraphs

to explain a concept that could

have been easily conveyed with a

simple diagram.

The most engaging parts of

The Dance of Life are the per-

sonal stories about the trials and

tribulations Zernicka-Goetz has

faced during her life in science.

Scientific disagreements occur,

papers get rejected, grants are not funded,

and balancing family and work is never easy.

Those of us who, like Zernicka-Goetz, are de-

velopmental biologists are in the fortunate

position of being in a field where many lead-

ing scientists are women (no all-male panels

for us!), but female scientists still struggle to

overcome the persistent biases and societal

and institutional barriers that block their

progress. At the end of the day however—as

Zernicka-Goetz and Highfield so ably show—

the thrill of scientific discovery is what keeps

us coming back to the bench. j

10.1126/science.aba2771

The personal and professional collide in a scientist’s

story of early human development

Four factors—fire, language,

beauty, and time—were key to

humankind’s ascension, argues

science writer Gaia Vince. This

week on the Science podcast,

Vince examines our evolution

through the lens of deep time,

revealing how our genes, culture,

and environment combined to

create modern humans.

sciencemag.org/podcasts

10.1126/science.aba9449

Transcendence: How Humans

Evolved Through Fire,

Language, Beauty, and Time

Gaia Vince

Basic Books, 2020. 352 pp.

Public clocks like the 14th-century Wells clock made time a commodity.

INSIGHTS | BOOKS

The reviewer is president and scientific director of the

Gairdner Foundation, Toronto, ON M5G 1L7, Canada,

and a senior scientist at the Hospital for Sick Children,

University of Toronto, Toronto, ON M5G 0A4, Canada.

Email: [email protected]

The Dance of Life

Magdalena Zernicka-Goetz

and Roger Highf eld

Basic Books, 2020. 304 pp.

PODCAST

Published by AAAS