The discovery that molecules called "small RNAs" control much of a gene's behavior--which may further research on cancer and stem cells--was named this year's top scientific achievement by the journal Science and its publisher, the American Association for the Advancement of Science (AAAS).
The importance of small RNAs, named the Breakthrough of the Year by Science's editors, leads their list of the top ten scientific developments in 2002. Science's Top Ten, chosen for their profound implications for society and the Advancement of science, appear in the journal's 20 December issue.
RNA was long thought to do little more than carry out DNA's commands for building proteins. The new picture, which came sharply into focus this year, shows small RNAs at the helm of many of the cell's genetic workings. In response, biologists are rethinking their understanding of the cell and its evolution, and uncovering new leads for treating diseases, such as cancer, caused by errors in the genome.
An array of recent studies has revealed how small RNAs can switch various genes on and off, and even trim away unwanted sections of DNA. One of the field's most electrifying discoveries this year was that small RNAs take charge during cell division, shepherding the material in chromosomes into the right configuration (Science Express 22 August 2002 and 5 September 2002).
This year's insights led to the tantalizing possibility that these processes, which include a type of cellular machinery known as "RNA interference," may go awry in certain diseases, producing cancer-causing mutations, for example. With this improved understanding of RNA's role, it may be possible someday to use RNA in cancer therapies.
Small RNAs may also be a boon to stem cell research, providing scientists with a tool for manipulating stem cells as they differentiate into the body's various cell types.
Science also salutes nine other scientific achievements of 2002. Except for the first runner up, the others are in no particular order.
How Neutrinos Escaped Notice: Research this year laid to rest a longstanding mystery about some of the least understood particles in the universe, the neutrinos. These elusive wisps come in three varieties, including "electron neutrinos" that are produced in the sun's nuclear furnace. For decades, scientists have scratched their heads over why the number of electron neutrinos reaching Earth is so much smaller than expected. This year, new evidence from the Sudbury Neutrino Observatory in Canada confirmed that the "missing" electron neutrinos are in fact morphing into the other neutrino types en route to Earth. New research from Earth-based experiments in Japan also provided some of the first clues about the conditions under which neutrinos switch guises.
Genomes for the Global Good: 2002 marked the first year that scientists announced genome sequence drafts for organisms with major agriculture and public health relevance for the developing world. The sequences of the indica rice subspecies and the short grain japonica subspecies may help efforts to improve rice's nutritional quality and crop yield, and to make cultivation methods more sustainable. The simultaneous publication of the malaria parasite, Plasmodium falciparum, and the mosquito that carries it, Anopheles gambiae, provided information that may make it possible to develop malaria-fighting tools, such as new mosquito repellants, insecticides, and mosquito vaccines.
Infant Universe in View: Newly-discovered features of the leftover energy from just after the Big Bang shed light, so to speak, on the universe's past and future. The Cosmic Microwave Background (CMB) appears to us now as faint microwave static coming from all regions of the sky, but just 400,000 years after the Big Bang, it was high energy light, emitted as free-streaming nuclei and electrons cooled and formed atoms. In 2002, the Cosmic Background Imager, a microwave telescope in Chile, detected patterns in the CMB structure that revealed structures far smaller than any seen before. Researchers also detected another type of pattern, or signal, that may yield new insights into the motion of matter during the early universe.
Spicy Hot and Minty Cool: New discoveries this year helped explain why spicy food feels hot, and breath mints give the mouth a chill. Researchers identified several proteins, embedded in the surfaces of certain cells, that respond to both chemical "flavors" and changes in temperature. One so-called "TRP channel" in mouth and skin nerves reacts when exposed to cold temperature or menthol, triggering the feeling of coolness. The discovery of a heat-sensing channel in skin cells suggested that warmth is sensed first by the skin itself, which then notifies the nervous system. A third channel may produce a different sort of heat, at least in the male mouse nose, where it seems to detect the pheromones of lady mice.
The Fastest Films: This year, researchers caught a glimpse of electrons whizzing around atoms, and made it into a movie. This high-speed film-making technique relies on ultra short pulses of laser light to freeze motion in frames just attoseconds (billionths of a billionth of a second) apart. While researchers were getting their techniques up to attosecond shutter speeds last year, in 2002 they trained their lasers on individual atoms, tracking electrons as they jumped up and down different energy levels. A whole new look at life inside the atom is coming soon to a laser physics lab near you.
Look Into the Eyes. Look Deep Into the Eyes. In 2002, several research teams took this advice and the results, a new class of light-responsive cells in the retinas of mammals, mesmerized the field. This photoreceptor system helps resets the body's daily, or "circadian," clock, making it a critical part of human physiology. It may even lead to new insights on countering the effects of jet lag or winter depression. The once-elusive cells turned out to be wired to the very area of the brain where the body clock resides, and contain a pigment called melanopsin. Two studies this month confirmed that melanopsin responds chemically to light, though other compounds may be involved.
Sharpened View of Space: New technology erased the blurring effect of Earth's atmosphere on telescopes' view of the heavens in 2002. The result, enabled by the flexing of thin mirrors hundred of times each second, was a suite of space images crisper than any taken before. Telescopes in Hawaii and Chile used this "adaptive optics" technology to look deep inside the Milky Way, finding the best evidence yet of a supermassive black hole. Other images this year included a volcanic eruption on Jupiter's moon, Io, and ultra-clear pictures of the sun's surface.
Cells in 3-D: A technology for taking three-dimensional pictures of a cell overcame key technical obstacles in 2002, providing insights into how the cell's machinery carries out some of the basic processes of life. "Cryoelectron tomography" works essentially like a doctor's CT scan; a computer constructs a 3-D image of a flash-frozen cell from a series of image "slices" created by penetrating electron beams.
Our Oldest Ancestor Yet: Researchers overturned some fundamental ideas about humans' earliest ancestors in July, when they reported the startling discovery of a primate skull between six and seven million years old. The fossil is almost 3 million years older than any known hominid, the lineage that includes humans but not other apes. The location of the skull, by the ancient Lake Chad in western Africa, was a surprise. Until now, humans' earliest ancestors had been found in east Africa. The skull's features look like a mix of chimpanzee, gorilla, and human, leading the researchers to classify their discovery as an altogether new genus and species of hominid--although debate on this issue continues.
Bioterrorism--Hurry up and Wait: The bioterror threat was a topic of much discussion but little direct action in 2002. In a special section on "the calm after the storm," Science looks at how major decisions on research funding, regulation, and smallpox vaccination were stalled by politics and technical debate.
The flip side of Science's Top Ten is its Breakdowns of the Year, spotlighting scientific misconduct in 2002. Separate investigations concluded that Hendrik Schön, a physicist at Bell Laboratories, and Victor Ninov, a physicist at Lawrence Berkeley National Laboratory, committed fraud.
Best Bets for Hot News in 2003: As in previous years, Science has chosen six hot topics to watch in 2003. This year, their choices include ice sheet movement, solar variability and climate change, science funding, genomics and evolutionary relationships, space observations using non-optical wavelengths, and antihydrogen. The editors also check in on the 2001 scorecard to see how well they did with last year's predictions.
AAAS' Top Ten List of Science Policy Stories: The "scientific balancing act"--that is, preventing safety fears from stifling life-changing discoveries--was cited by AAAS as the key science-policy issue to emerge in 2002. For additional information on the AAAS list, see www.eurekalert.org, or contact the AAAS Office of Public Programs at 202-326-6440, or firstname.lastname@example.org
As the world's leading peer-reviewed general science journal, Science is uniquely suited to compile the most authoritative list of the year's scientific accomplishments. The top ten list is the fourteenth since Science inaugurated the feature. Editor-In-Chief Donald Kennedy writes about the Breakthrough of the Year report in the 20 December issue's editorial, which is available upon request.
Founded in 1880 by Thomas A. Edison, Science has been the official journal of the American Association for the Advancement of Science (AAAS) since 1900. The nonprofit AAAS is the world's largest scientific organization.