I
n an imaginary universe, you have discovered a set
of planets, each with its own complex civilization
with many culturally distinct nations. You face the
daunting task of exploring each planet, mapping
national boundaries, and characterizing different
cultural features. In discussing this challenge with
your colleagues, you come up with an alternative
plan. You can divide each planet into small sectors,
tag each sector for identification, send out many small
probes to land in random locations and send back data,
and then use the tagging information to computation-
ally assemble the informa-
tion into detailed atlases
and travel guides. Science’s
Breakthrough of the Year
recognizes the application
of this tag-analyze-assemble
approach to one of the most
fundamental and fascinat-
ing processes in biology—the
seemingly miraculous trans-
formation of single cells into
complex organisms—provid-
ing rich information about
cell-type inventories and lay-
ing the foundation for many
future studies.
This achievement builds
on the 2002 Nobel Prize–win-
ning work of John Sulston
and colleagues who had
mapped the development of
the roundworm Caenorhab-
ditis elegans by painstakingly
watching larvae mature cell by cell through micro-
scopes. This revealed the sequence of cell divisions that
resulted in elaborate structures, which led to the char-
acterization of important processes. With today’s tech-
nologies, especially massively parallel DNA sequencing
and advanced fluorescence microscopy, the cells that
comprise C. elegans have been mapped again using tag-
analyze-assemble methods based on gene expression
patterns within each cell. The same approaches have
been used to map the cellular anatomy of organisms
of increasing complexity and size. An additional ben-
efit is that the gene expression signals that define each
cell type also provide fundamental information about
the biochemistry and biology of each cell. The large
and rich datasets that have been generated, and the
techniques that will produce more, constitute exciting
breakthroughs in developmental biology.Nucleic acid–based technologies also underlie some
of this year’s runners-up, including advanced methods
in forensics that combine sequence and other databases,
elucidation of the breeding habits of earlier hominids,
and long-awaited advances in RNA-based therapies. A
range of technologies has also led to important concep-
tual advances in the organizational principles within
cells. Technologies that elucidated large biological molec-
ular structures have been applied to smaller molecules,
resulting in a remarkable advance in analytical chem-
istry. Exploration has revealed insights into the ancient
history of our planet. Strange
lifeforms, known from fos-
sils hundreds of millions of
years old, now appear to be
ancestors of modern animals
rather than lines that went
extinct. A crater discovered
under the ice in Greenland
likely resulted from a large
meteorite impact. One source
of other cosmic visitors, high-
energy neutrinos, has been
found to be types of galaxies
with a massive black hole at
their centers.
Other events have high-
lighted cultural issues. The
#MeTooSTEM movement has
brought much needed atten-
tion to sexual harassment
within the scientific com-
munity. Further progress is
essential to allow individuals
of all genders to pursue their training and careers with-
out dealing with the realities of substantially unchecked
harassment. The announcement of the birth of babies
with genomes that had been intentionally modified in
a manner that appears to violate many long-standing
ethical principles reminds us that scientific results,
no matter how exciting and full of potential, must be
applied with appropriate care and respect for ethical
international norms. Finally, we are challenged by the
changing climate of our own planet. Powerful storms as-
sociated with large amounts of rainfall and other events
are occurring with increasing frequency, illustrating the
considerable urgency for appropriate actions. We must
work together across global borders and cultures to
drive effective steps to arrest harmful climate change.–Jeremy BergExploring organisms cell by cell
Editor-in-Chief,
Science Journals.
[email protected]10.1126/science.aawA zebrafish embryo, 30 hours postfertilization, reveals
descendants (fluorescently labeled) of cells that were
transplanted 22 hours earlier.CREDITS: (INSET) JEFFREY FARRELL (ZEBRAFISH DEVELOPMENT AND GENETICS COURSE, MARINE BIOLOGICAL LABORATORY & SCHIER LAB, HARVARD UNIVERSITY); (TOP RIGHT) TERRY CLARK
SCIENCE sciencemag.org 21 DECEMBER 2018 • VOL 362 ISSUE 6421 1333EDITORIAL
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