Human Stem Cell Research Leads Science's Top Ten List Of The Best Scientific Advances In 1999

This was the pivotal year in which scientists and the public grappled with the ethical and scientific implications of stem cell research. Late last year, two teams of researchers managed to make stem cells from human embryos grow in the laboratory, producing bone, muscle, nerve, and other types of cells. It may someday be possible to use this approach to treat human disease in ways never before thought possible, such as growing new organs or repairing nerve damage. But, for many, using cells from a human embryo to do so is a troubling prospect. Although the debate is sure to continue, new federal rules suggest that the climate for embryonic stem cell research may be beginning to thaw.

And there are few ethical concerns regarding stem cells from adults, which may also provide fodder for important therapies. These cells, which supply new cells to parts of the body with high cellular turnover rates such as the skin, blood, or the nervous system, were the subject of a flurry of astonishing discoveries in 1999. We have now learned that under the right conditions many adult stem cells can shed their old identities and adopt new ones, for example producing blood cells instead of nerve cells-a finding just as surprising as learning that Yo Yo Ma won the Wimbledon Cup.

Science also salutes nine other research advances that made 1999 a banner year for science. After the first runner up, the discoveries are not ranked.

First Runner up, Genomics: The floodgates broke open on genomic research in 1999, releasing a torrent of data that included the complete genome for several microbes, two maps of the malaria parasite genome, and the first sequence for a human chromosome. Sequences for the fruit fly and humans are ahead of schedule, with a rough draft of the human genome due in March 2000. The genomic explosion continues to drive the development of sophisticated tools like DNA "chips" and advanced databases to handle the sequencing, comparison, and analysis of thousands of genes.

Blueprints for the Protein Factory: A grueling, decades-long attempt to solve one of biology's most frustrating puzzles had a eureka moment this year with the creation of the first complete molecular map of the ribosome, the cell's essential protein factory. Several groups of researchers had a hand in sorting out the details of the ribosome's dauntingly complex structure. Energized by this flurry of success, scientists are now hoping to catch a glimpse of the ribosome as it operates its protein assembly line, engaging in the most basic activity performed by all living things.

The Weird World of Quantum Matter: This year scientists created a bizarre new kind of gas that may one day help them probe the basic nature of matter and build the next generation of atomic clocks and lasers. The gas consists of atoms that fall into the category of fermions, one of nature's two types of elementary particles, which by definition are antisocial particles that refuse to occupy the same energy state. Now a team of scientists has coaxed a swarm of fermions into a state where they are precisely arranged in a ladder of energies. This achievement clears the way for the creation of a completely new type of quantum matter-a counterpart to the famous Bose-Einstein condensate (Science's Top Advance of 1995) made from the other type of elementary particle, the boson.

Complex Life Gets a Billion Years Older: This year researchers pushed back the beginnings of complex life by a billion years after finding telltale signs of eukaryotic cells (which contain a nucleus) in 2.7 billion-year old Australian rocks. These primitive inklings of life were unearthed with the help of a technique that searches for the residue of molecules produced by cells. The chemical signatures left by the Australian ancestors indicate that this ancient world was populated by eukaryotes much earlier than scientists had thought.

Mystery Explosions Unveiled: After almost 30 years of wondering, researchers have now discovered that at least some of the intense cosmic explosions known as gamma ray bursts are linked to the collapse of massive stars, or "supernovae." Gamma ray bursts emit more power in a few seconds than the sun does in ten billion years. Details of the link between these colossal explosions and supernovae should come from two NASA satellites, to be launched in January and 2003, whose telescopes will respond immediately to gamma ray bursts.

A Flat Universe: The universe's tally of matter and energy finally added up in 1999 as researchers confirmed their hunch that the cosmos was born in a burst that stretched space flat. A flat universe requires just the right density of matter, and up until this year scientists had searched in vain for enough matter to fit the bill. But last year's discovery (which was Science's Top Advance of 1998) suggested that a mysterious energy pushing the universe's expansion might fill in the missing matter. This year, new information from a variety of locations showed ripples in the microwave background, the afterglow of the Big Bang, that are exactly the right size to imply a flat universe.

Molecules Make a Memory: A series of findings this year has made it easier to comprehend how memories, the most intangible of human experiences, are formed by concrete molecular activities in the brain. Scientists used new methods to film neurons laying the groundwork for memories and gained new insight into the molecules and steps involved in the process. The power of these interactions was dramatically demonstrated when scientists genetically engineered a strain of mice that produced an abundance of one such molecule and were unusually successful at learning mazes.

A Plethora of New Planets: Reports of new planets in neighboring solar systems poured in throughout 1999, increasing the tally of known extra-solar planets to almost 30. And while previous sightings were indirect, this year, astronomers actually caught one crossing the face of its star, confirming the existence of exoplanets. The latest batch of exoplanets even contains worlds that orbit in the habitable zone of their parent stars, where liquid water and life could exist. While none of the planets discovered so far actually has what it takes to support life, theorists think that the universe should be teeming with more planets that await discovery.

Taming Light With Photonic Crystals: Scientists took some significant steps this year in their quest to create photonic devices that will someday harness the power of light the way traditional semiconductors have corralled the energy of electrons. This year several groups of researchers in the U.S. and UK developed photonic crystals that trap and direct specific wavelengths of light. In the near future scientists hope to perfect their manipulations of these crystals and put them to work in high-speed communications networks, powerful lasers, and optical computers.

Best Bets for Hot News in Y2K: As in previous years, the Editors of Science have chosen six hot research areas to watch in the millennial year. This year their choices are: enzymes in Alzheimer's disease, river restoration projects, x-ray astronomy, epigenetics, nanocomputers, and polio eradication. The editors also check in on last year's scorecard to see how well they did with 1998's predictions.

Science's Top Ten section also includes some additional awards. The dubious honor of being the Blunder of the Year goes to NASA's inadvertent use of English instead of metric units in calculations that ultimately caused the demise of the Mars Climate Orbiter. The Kansas Board of Education vote to drop evolution form statewide science teaching standards has been dubbed the Breakdown of the Year, while the Controversy of the Year was the debate over genetically modified foods.

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 described in the next issue's "Breakthrough of the Year" section, which is the eleventh since Science inaugurated the feature. The ten research advances were chosen by the editors, led by Editor-in-Chief Floyd E. Bloom, M.D. of Scripps Research Institute in La Jolla, CA. Bloom writes about the "Breakthrough of the Year" report in the 17 December issue's editorial, which is available upon request.

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A draft of the "Breakthrough of the Year" section is available, under embargo from the AAAS News & Information Office. The cover of the 17 December issue of Science relates to the "Breakthrough of the Year" section and is also available.

For more information about the top research advance, human stem cell research, please contact Heather Singmaster in the News & Information Office at 202-326-6414 or hsingmas@aaas.org. For more information about the rest of the "Breakthrough of the Year" section, please contact Elizabeth Culotta, Contributing News Editor, at 330-678-7700 (phone) or eculotta@compuserve.com (email).

For copies of the "Breakthrough of the Year" section or the editorial, please email scipak@aaas.org or call 202-326-6440. For cover art, please contact Heather Singmaster at 202-326-6414 (phone), or hsingmas@aaas.org (email).