This weekend's full moon hangs lower in the sky than any other full moon of 2007, according to NASA, and it's a good time to be fooled.
When low on the horizon, the Moon can appear to be larger than when it's higher in the sky. It's all an illusion, scientists say, and it does not involve any enlarging effects of the atmosphere. Rather, it's all in your mind.
Here's how it works:
Our brains think things on the horizon are farther away than stuff overhead, because we're used to seeing overhead clouds that are close compared to those on the horizon. In the mind's eye, the sky is a flattened dome.
With this dome as a reference, we expect something on the horizon (such as the moon) to be father, and because it is actually no farther than when overhead, our brains goof and imagine that it is larger.
Skeptical? You can test this from home.
When the moon first rises, hold something small like the eraser of a pencil at arms length and compare its size to the moon on the horizon. Do the same a couple hours later when the moon is higher. Or try this: Take a picture of the moon in both positions, then cut, paste and compare. Another trick: Make a tube from rolled-up paper so the opening is just slightly larger than the moon when it rises. Tape the tube so the size stays fixed, then check later to see if the moon has changed sizes.
Officially, the moon will be full Saturday June 30 at 9:49 a.m. ET. Of course, you'll want to do your looking in the evening. Local moonrise times are available from the U.S. Naval Observatory. Keep in mind that mountains and buildings can dramatically alter your actual local moonrise time.
The big-moon-rising effect will be evident Friday, Saturday and Sunday. On each evening, the moon will appear nearly full. Interestingly, the moon is never fully full from our point of view, but that's another story.
While you're out, check out Venus and Saturn, which are snuggling close together in the western sky as darkness falls.
So why is one full moon lower in the sky than another? The moon's orbit around Earth is tilted 5 degrees compared to the plane of Earth's travels around the Sun, and Earth itself is tilted on its rotational axis. All this accounts for the lunar phases, and it also means the moon's path through our sky can be higher or lower depending on the angles on any given night.
The complex orbit of the Earth-moon system is constantly evolving, too. Right now, the moon is moving away from us by more than 1.5 inches every year.
Top 10 Moon Facts
Moon Phases, Moon Names, Lunar Lore
Lunar Image Gallery
Original Story: Saturday's Full Moon Offers Strange Illusion
Visit SPACE.com and explore our huge collection of Space Pictures, Space Videos, Space Image of the Day, Hot Topics, Top 10s, Multimedia, Trivia, Voting and Amazing Images. Follow the latest developments in the search for life in our universe in our SETI: Search for Life section. Join the community, sign up for our free daily email newsletter, listen to our Podcasts, check out our RSS feeds and other Reader Favorites today!
Robert Roy Britt
Senior Science Writer
SPACE.com
Saturday, June 30, 2007
Wednesday, June 27, 2007
Tooth May Have Solved Mummy Mystery
A single tooth and some DNA clues appear to have solved the mystery of the lost mummy of Hatshepsut, one of the great queens of ancient Egypt, who reigned in the 15th century B.C.
Archaeologists who conducted the research, to be announced formally today in Cairo, said this was the first mummy of an Egyptian ruler to be found and “positively identified” since King Tutankhamen’s tomb was opened in 1922.
Zahi Hawass, secretary general of the Supreme Council of Antiquities in Cairo, said Monday in a telephone interview that the mummy was found in 1903 in an obscure, undecorated tomb in the Valley of the Kings, across the Nile from modern Luxor, and had been largely overlooked for more than a century.
Dr. Hawass said the identification of the well-preserved mummy as Hatshepsut (pronounced hat-SHEP-soot) was made a few weeks ago when a CT scan of a wooden box associated with the queen revealed a tooth. The tooth, he said, “fits exactly” into the jaw socket and broken root of the mummy of an obese woman originally found in Tomb 60 at the Valley of the Kings, the necropolis for royalty in the New Kingdom before and after Hatshepsut’s reign.
“We therefore have scientific proof that this is the mummy of Queen Hatshepsut,” Dr. Hawass concluded, citing primarily the tooth but also current DNA analysis suggesting a family relationship between the obese woman and Ahmose Nefertari, the matriarch of 18th dynasty royalty.
Other Egyptologists not involved in the project said that the finding was fascinating, but that they would reserve judgment until they had studied the results of the DNA analysis and had some of the evidence confirmed by other researchers.
“You have to be so careful in reaching conclusions from such data,” said Kathryn Bard, an Egyptologist at Boston University.
Dr. Bard said, however, that it was not surprising that Hatshepsut’s mummy would turn up in a humble tomb, not the more elaborate one presumably intended for her. She noted that the queen’s stepson Thutmose III, after he succeeded to the throne on her death, “tried to destroy every trace of her and her reign,” so it was likely that her preserved body was hidden in another burial chamber for safekeeping.
The search for Hatshepsut’s mummy by Egyptian archaeologists and medical scientists will be described in a television program, “Secrets of Egypt’s Lost Queen,” scheduled for July 15 on the Discovery Channel.
As Dr. Hawass tells the story, he was approached by the Discovery Channel to apply new scientific technology to the search for the lost mummy. He thought the odds of success were slim, but looked upon the project as an opportunity to investigate a collection of unidentified female mummies in tombs and in the Cairo Museum.
To the frustration of archaeologists, royal Egyptian mummies were often moved from their original tombs and hidden in less conspicuous ones to stymie would-be plunderers. Identifying marks were frequently lost in the transfer.
Dr. Hawass and his team began the search at Tomb 60. Howard Carter, the British archaeologist who discovered the King Tut tomb, had excavated these smaller chambers in 1903. He found two mummies there: one in a coffin inscribed for a royal nurse, the other stretched out on the floor.
On a recent visit to Tomb 60, Dr. Hawass examined the mummy that had been on the floor, the obese one. Her left arm was bent at the elbow, with the hand over her chest. Her right arm lay against her side. The fingernails of the left hand were painted red and outlined in black. She was bald in front, with long hair in back.
Seeing the arrangement of her arms, Dr. Hawass said, “I believed at once that she was royal, but had no real opinion as to who she might be.”
Other Egyptologists also saw the left arm on the chest as a royal characteristic. But Dr. Bard of Boston University said that royal mummies were usually laid out with both hands crossed at the chest.
In the search, Dr. Hawass had radiologists make CT scans of six unidentified female mummies as well as some objects associated with them. The last of these examined objects was a wooden box bearing the name Hatshepsut. The box had been recovered from yet another tomb.
The container held some of the viscera removed from the body during embalming. Everything associated with a royal body or its mummification was carefully and ritually preserved. Late one night recently, the box was subjected to the CT scan.
“It turned out that this box held the key to the riddle,” Dr. Hawass said.
The images revealed a well-preserved liver and the tooth. A dentist, Dr. Galal el-Beheri of Cairo University, was called in. He studied the images of the mummy collection, and the tooth seemed to belong to the obese mummy.
Further CT scans led physicians to conclude that the woman was about 50 when she died. She was overweight and had bad teeth. She probably had diabetes and died of bone cancer, which had spread through her body.
Dr. Hawass said the DNA research into the possible Hatshepsut mummy was continuing, and he was vague about when the results would be reported. But early tests of mitochondrial DNA, he said, showed a relationship between the mummy and the matriarch Ahmose Nefertari.
Some archaeologists say they have evidence that this mummy, found in an obscure and unadorned tomb in the Valley of the Kings, is Hatshepsut, one of the great queens of ancient Egypt, who died at about age 50.
By JOHN NOBLE WILFORD
Published: June 27, 2007
Archaeologists who conducted the research, to be announced formally today in Cairo, said this was the first mummy of an Egyptian ruler to be found and “positively identified” since King Tutankhamen’s tomb was opened in 1922.
Zahi Hawass, secretary general of the Supreme Council of Antiquities in Cairo, said Monday in a telephone interview that the mummy was found in 1903 in an obscure, undecorated tomb in the Valley of the Kings, across the Nile from modern Luxor, and had been largely overlooked for more than a century.
Dr. Hawass said the identification of the well-preserved mummy as Hatshepsut (pronounced hat-SHEP-soot) was made a few weeks ago when a CT scan of a wooden box associated with the queen revealed a tooth. The tooth, he said, “fits exactly” into the jaw socket and broken root of the mummy of an obese woman originally found in Tomb 60 at the Valley of the Kings, the necropolis for royalty in the New Kingdom before and after Hatshepsut’s reign.
“We therefore have scientific proof that this is the mummy of Queen Hatshepsut,” Dr. Hawass concluded, citing primarily the tooth but also current DNA analysis suggesting a family relationship between the obese woman and Ahmose Nefertari, the matriarch of 18th dynasty royalty.
Other Egyptologists not involved in the project said that the finding was fascinating, but that they would reserve judgment until they had studied the results of the DNA analysis and had some of the evidence confirmed by other researchers.
“You have to be so careful in reaching conclusions from such data,” said Kathryn Bard, an Egyptologist at Boston University.
Dr. Bard said, however, that it was not surprising that Hatshepsut’s mummy would turn up in a humble tomb, not the more elaborate one presumably intended for her. She noted that the queen’s stepson Thutmose III, after he succeeded to the throne on her death, “tried to destroy every trace of her and her reign,” so it was likely that her preserved body was hidden in another burial chamber for safekeeping.
The search for Hatshepsut’s mummy by Egyptian archaeologists and medical scientists will be described in a television program, “Secrets of Egypt’s Lost Queen,” scheduled for July 15 on the Discovery Channel.
As Dr. Hawass tells the story, he was approached by the Discovery Channel to apply new scientific technology to the search for the lost mummy. He thought the odds of success were slim, but looked upon the project as an opportunity to investigate a collection of unidentified female mummies in tombs and in the Cairo Museum.
To the frustration of archaeologists, royal Egyptian mummies were often moved from their original tombs and hidden in less conspicuous ones to stymie would-be plunderers. Identifying marks were frequently lost in the transfer.
Dr. Hawass and his team began the search at Tomb 60. Howard Carter, the British archaeologist who discovered the King Tut tomb, had excavated these smaller chambers in 1903. He found two mummies there: one in a coffin inscribed for a royal nurse, the other stretched out on the floor.
On a recent visit to Tomb 60, Dr. Hawass examined the mummy that had been on the floor, the obese one. Her left arm was bent at the elbow, with the hand over her chest. Her right arm lay against her side. The fingernails of the left hand were painted red and outlined in black. She was bald in front, with long hair in back.
Seeing the arrangement of her arms, Dr. Hawass said, “I believed at once that she was royal, but had no real opinion as to who she might be.”
Other Egyptologists also saw the left arm on the chest as a royal characteristic. But Dr. Bard of Boston University said that royal mummies were usually laid out with both hands crossed at the chest.
In the search, Dr. Hawass had radiologists make CT scans of six unidentified female mummies as well as some objects associated with them. The last of these examined objects was a wooden box bearing the name Hatshepsut. The box had been recovered from yet another tomb.
The container held some of the viscera removed from the body during embalming. Everything associated with a royal body or its mummification was carefully and ritually preserved. Late one night recently, the box was subjected to the CT scan.
“It turned out that this box held the key to the riddle,” Dr. Hawass said.
The images revealed a well-preserved liver and the tooth. A dentist, Dr. Galal el-Beheri of Cairo University, was called in. He studied the images of the mummy collection, and the tooth seemed to belong to the obese mummy.
Further CT scans led physicians to conclude that the woman was about 50 when she died. She was overweight and had bad teeth. She probably had diabetes and died of bone cancer, which had spread through her body.
Dr. Hawass said the DNA research into the possible Hatshepsut mummy was continuing, and he was vague about when the results would be reported. But early tests of mitochondrial DNA, he said, showed a relationship between the mummy and the matriarch Ahmose Nefertari.
Some archaeologists say they have evidence that this mummy, found in an obscure and unadorned tomb in the Valley of the Kings, is Hatshepsut, one of the great queens of ancient Egypt, who died at about age 50.
By JOHN NOBLE WILFORD
Published: June 27, 2007
Sunday, June 24, 2007
Three thousand year-old mummy discovered in Egypt
CAIRO (AFP) - Archaeologists have discovered the 3,000-year-old mummy of a high priest to the god Amun in the southern city of Luxor, antiquities supremo Zahi Hawass told the official MENA news agency on Saturday.
The 18th Dynasty mummy of Sennefer was unearthed in a tomb in the Valley of the Kings -- one of the most famous archaeological sites in the world -- by a team from Britain's Cambridge University.
"The mummy was found in tomb 99 in the Valley of the Kings on the west bank of Luxor," Hawass said.
A high priest was considered to be the most important man after the king, performing duties, religious rituals and offerings on his behalf.
Other mummies were found during the excavation, including one with a brain tumour, a foetus, a female mummy wrapped in plaster and others which appeared to have suffered from arthritis, Hawass said.
The Valley of the Kings was used as a burial site for royalty and nobles to the west of present day Luxor, some 700 kilometres (450 miles) south of Cairo.
Millions of foreign tourists come to see Egypt's pharaonic treasures each year, including hundreds of thousands making the long journey south from the capital to the Valley of the Kings.
Hawass said a report on the findings would be presented to Culture Minister Faruq Hosni, in order to allocate resources for continued excavations in the area.
The 18th Dynasty mummy of Sennefer was unearthed in a tomb in the Valley of the Kings -- one of the most famous archaeological sites in the world -- by a team from Britain's Cambridge University.
"The mummy was found in tomb 99 in the Valley of the Kings on the west bank of Luxor," Hawass said.
A high priest was considered to be the most important man after the king, performing duties, religious rituals and offerings on his behalf.
Other mummies were found during the excavation, including one with a brain tumour, a foetus, a female mummy wrapped in plaster and others which appeared to have suffered from arthritis, Hawass said.
The Valley of the Kings was used as a burial site for royalty and nobles to the west of present day Luxor, some 700 kilometres (450 miles) south of Cairo.
Millions of foreign tourists come to see Egypt's pharaonic treasures each year, including hundreds of thousands making the long journey south from the capital to the Valley of the Kings.
Hawass said a report on the findings would be presented to Culture Minister Faruq Hosni, in order to allocate resources for continued excavations in the area.
Tuesday, June 19, 2007
Space Station and Shuttle Visible Together in Night Sky
With the Space Shuttle Atlantis scheduled to undock from the International Space Station (ISS) on Tuesday, skywatchers across much of the United States and southern Canada are in for a real treat on Tuesday and Wednesday evenings.
Should weather conditions permit to offer clear skies, there will be a few opportunities to see both the Atlantis orbiter and the ISS flying across the sky from many locations.
The sight should easily be visible to anyone, even from brightly-lit cities.
Other satellites too
The appearance of either the Space Shuttle or the Space Station moving across the sky is not in itself unusual. On any clear evening within a couple of hours of local sunset and with no optical aid, you can usually spot several orbiting Earth satellites creeping across the sky like moving stars. Satellites become visible only when they are in sunlight and the observer is in deep twilight or darkness. This usually means shortly after dusk or before dawn.
What makes the prospective upcoming passages so interesting is that you'll be able to see the two largest orbiting space vehicles in the sky at the same time.
Shuttle Atlantis is expected to undock from the ISS at 10:40 a.m. Eastern Daylight Time on Tuesday. Atlantis will fly around the ISS before finally pulling away from the Station at 12:28 EDT, although it should still remain at a relatively close distance to it until its scheduled return to the Kennedy Space Center in Florida on Thursday, June 21.
What to expect
Both vehicles will be traveling across North America on northwest-to-southeast trajectories.
Appearing as a pair of very "bright 'stars," the ISS should appear as the somewhat brighter object and will appear to be trailing Shuttle Atlantis as they move across the sky. A large telescope would be needed to make out details of the sprawling station. Traveling in their respective orbits at approximately 18,000 mph (29,000 kilometers per hour), both should be visible from about one to four minutes (depending on the particular viewing pass) as they glide with a steady speed across the sky.
Because of its size and configuration of highly reflective solar panels, the Space Station is now, by far, the brightest man-made object currently in orbit around the Earth. On favorable passes, it approaches magnitude -3 in brightness, which would rival the planet Jupiter and is four times brighter than Sirius, the brightest star in the night sky.
On future missions, additional solar arrays will be deployed, making the ISS appear even brighter. When completed in 2010, it might even rival Venus, the brightest planet. And as a bonus, sunlight glinting directly off the solar panels can sometimes make the ISS appear to briefly flare in brilliance.
Region of visibility
Generally speaking, the Shuttle-ISS tandem will be visible across southern Canada and most of the 48 contiguous United States (Hawaii and Alaska, unfortunately will not have favorable viewing passes during this upcoming week).
Locations that are situated above latitude 35-degrees north, will be able to partake in at least a few of the Tuesday/Wednesday evening viewing opportunities. Between roughly 30 and 35-degrees north latitude, however, the viewing options become much fewer, perhaps only one or two chances at best. Meanwhile, localities below roughly latitude 30-degrees north are (with a few exceptions) out of luck, with no visibility expected.
Again, keep in mind again that once undocked, Atlantis should appear to lead the Space Station by some distance as they track across the sky.
When and where to look
So what is the viewing schedule for your particular hometown? You can easily find out by visiting one of these three popular web sites:
NASA's SkyWatch
Science@NASA's J-Pass
Chris Peat's Heavens Above
Each will ask for your zip code or city, and respond with a list of suggested spotting times. Predictions computed a few days ahead of time are usually accurate within a few minutes. However, they can change due to the slow decay of the space station's orbit and periodic reboosts to higher altitudes. Check frequently for updates.
Complete Shuttle Coverage
Online Sky Maps and More
Astrophotography 101
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.
Original Story: Space Station and Shuttle Visible Together in Night Sky
Visit SPACE.com and explore our huge collection of Space Pictures, Space Videos, Space Image of the Day, Hot Topics, Top 10s, Multimedia, Trivia, Voting and Amazing Images. Follow the latest developments in the search for life in our universe in our SETI: Search for Life section. Join the community, sign up for our free daily email newsletter, listen to our Podcasts, check out our RSS feeds and other Reader Favorites today!
Joe Rao
SPACE.com Skywatching Columnist
Should weather conditions permit to offer clear skies, there will be a few opportunities to see both the Atlantis orbiter and the ISS flying across the sky from many locations.
The sight should easily be visible to anyone, even from brightly-lit cities.
Other satellites too
The appearance of either the Space Shuttle or the Space Station moving across the sky is not in itself unusual. On any clear evening within a couple of hours of local sunset and with no optical aid, you can usually spot several orbiting Earth satellites creeping across the sky like moving stars. Satellites become visible only when they are in sunlight and the observer is in deep twilight or darkness. This usually means shortly after dusk or before dawn.
What makes the prospective upcoming passages so interesting is that you'll be able to see the two largest orbiting space vehicles in the sky at the same time.
Shuttle Atlantis is expected to undock from the ISS at 10:40 a.m. Eastern Daylight Time on Tuesday. Atlantis will fly around the ISS before finally pulling away from the Station at 12:28 EDT, although it should still remain at a relatively close distance to it until its scheduled return to the Kennedy Space Center in Florida on Thursday, June 21.
What to expect
Both vehicles will be traveling across North America on northwest-to-southeast trajectories.
Appearing as a pair of very "bright 'stars," the ISS should appear as the somewhat brighter object and will appear to be trailing Shuttle Atlantis as they move across the sky. A large telescope would be needed to make out details of the sprawling station. Traveling in their respective orbits at approximately 18,000 mph (29,000 kilometers per hour), both should be visible from about one to four minutes (depending on the particular viewing pass) as they glide with a steady speed across the sky.
Because of its size and configuration of highly reflective solar panels, the Space Station is now, by far, the brightest man-made object currently in orbit around the Earth. On favorable passes, it approaches magnitude -3 in brightness, which would rival the planet Jupiter and is four times brighter than Sirius, the brightest star in the night sky.
On future missions, additional solar arrays will be deployed, making the ISS appear even brighter. When completed in 2010, it might even rival Venus, the brightest planet. And as a bonus, sunlight glinting directly off the solar panels can sometimes make the ISS appear to briefly flare in brilliance.
Region of visibility
Generally speaking, the Shuttle-ISS tandem will be visible across southern Canada and most of the 48 contiguous United States (Hawaii and Alaska, unfortunately will not have favorable viewing passes during this upcoming week).
Locations that are situated above latitude 35-degrees north, will be able to partake in at least a few of the Tuesday/Wednesday evening viewing opportunities. Between roughly 30 and 35-degrees north latitude, however, the viewing options become much fewer, perhaps only one or two chances at best. Meanwhile, localities below roughly latitude 30-degrees north are (with a few exceptions) out of luck, with no visibility expected.
Again, keep in mind again that once undocked, Atlantis should appear to lead the Space Station by some distance as they track across the sky.
When and where to look
So what is the viewing schedule for your particular hometown? You can easily find out by visiting one of these three popular web sites:
NASA's SkyWatch
Science@NASA's J-Pass
Chris Peat's Heavens Above
Each will ask for your zip code or city, and respond with a list of suggested spotting times. Predictions computed a few days ahead of time are usually accurate within a few minutes. However, they can change due to the slow decay of the space station's orbit and periodic reboosts to higher altitudes. Check frequently for updates.
Complete Shuttle Coverage
Online Sky Maps and More
Astrophotography 101
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.
Original Story: Space Station and Shuttle Visible Together in Night Sky
Visit SPACE.com and explore our huge collection of Space Pictures, Space Videos, Space Image of the Day, Hot Topics, Top 10s, Multimedia, Trivia, Voting and Amazing Images. Follow the latest developments in the search for life in our universe in our SETI: Search for Life section. Join the community, sign up for our free daily email newsletter, listen to our Podcasts, check out our RSS feeds and other Reader Favorites today!
Joe Rao
SPACE.com Skywatching Columnist
Wednesday, June 06, 2007
Technique Raises Hopes of Easing Stem Cell Debate
In a surprising advance that could sidestep the ethical debates surrounding stem cell biology, researchers have come much closer to a major goal of regenerative medicine, the conversion of a patient’s cells into specialized tissues that might replace those lost to disease.
The advance is an easy-to-use technique for reprogramming a skin cell of a mouse back to the embryonic state. Embryonic cells can be induced in the laboratory to develop into many of the body’s major tissues.
If the technique can be adapted to human cells, researchers could use a patient’s skin cell to generate new heart, liver or kidney cells that might be transplantable and would not be rejected by the patient’s immune system. But scientists say they cannot predict when they can overcome the considerable problems in adapting the method to human cells.
Previously, the only way to convert adult cells to embryonic form has been by nuclear transfer, the insertion of an adult cell’s nucleus into an egg whose own nucleus has been removed. The egg somehow reprograms the nucleus back to an embryonic state. That procedure is known as therapeutic cloning when applied to people, but no one has yet succeeded in doing it.
The new technique, developed by Shinya Yamanaka of Kyoto University, depends on inserting just four genes into a skin cell. These accomplish the same reprogramming task as the egg does, or at least one that seems very similar.
The technique, if adaptable to human cells, is much easier to apply than nuclear transfer, would not involve the expensive and controversial use of human eggs, and should avoid all or almost all of the ethical criticism directed at the use of embryonic stem cells.
“From the point of view of moving biomedicine and regenerative medicine faster, this is about as big a deal as you could imagine,” said Irving Weissman, a leading stem cell biologist at Stanford University, who was not involved in the new research.
David Scadden, a stem cell biologist at the Harvard Medical School, said the finding that cells could be reprogrammed with simple biochemical techniques “is truly extraordinary and frankly something most assumed would take a decade to work out.”
The technique seems likely to be welcomed by many who have opposed human embryonic stem cell research. It “raises no serious moral problem, because it creates embryonic-like stem cells without creating, harming or destroying human lives at any stage,” said Richard Doerflinger, the United States Conference of Catholic Bishops’ spokesman on stem cell issues. In themselves, embryonic stem cells “have no moral status,” and the bishops’ objections to embryonic stem cell research rest solely on the fact that human embryos must be harmed or destroyed to obtain them, Mr. Doerflinger said.
Ronald Green, an ethicist at Dartmouth College, said it would be “very hard for people to say that what is created here is a nascent form of human life that should be protected.” The new technique, if adaptable to human cells, “will be one way this debate could end,” Mr. Green said.
Biologists learned how to generate human embryonic stem cells in 1998 from the few-day-old embryos discarded by fertility clinics, a procedure the embryos did not survive. This source proved controversial, and biologists supported by federal financing were unable to explore the new opportunity until August 2001 when President Bush, in a political compromise, decreed that research on human embryonic stem cells could begin, but only with cell lines already in existence by that date.
The restrictions have caused considerable frustration among biologists and other supporters of research on embryonic stem cells. Indeed, the House is expected to vote today to increase federal funds for such research. If approved, the bill, similar to one approved by the Senate, would go to the president. The White House has already said that the president would veto it.
The new technique, when adaptable to human cells, should sidestep all these problems. James Battey, vice chairman of the National Institutes of Health stem cell task force, said he saw “no impediment at all” to federal support of researchers using the new technique on human cells.
Ever since the creation of Dolly, the first cloned mammal, scientists have sought to lay hands on the mysterious chemicals with which an egg will reprogram a mature cell nucleus injected into it and set the cell on the same path of embryonic development as when egg and sperm combine.
Years of patient research have identified many of the genes that are active in the embryonic cell and maintain its pluripotency, or ability to morph into many different tissues. Last year Dr. Yamanaka and his colleague Kazutoshi Takahashi, both at Kyoto University, published a remarkable report relating how they had guessed at 24 genes responsible for maintaining pluripotency in mouse embryonic stem cells.
When they inserted all 24 genes into mouse skin cells, some of the cells showed signs of pluripotency. The Kyoto team then subtracted genes one by one until they had a set of four genes that were essential. The genes are inserted into viruses that infect the cell and become active as the virus replicates. The skin cell’s own copies of these genes are repressed since they would interfere with its function. “We were very surprised” that just four genes are sufficient to reprogram the skin cells, Dr. Yamanaka said.
Dr. Yamanaka’s report riveted the attention of biologists elsewhere. Two teams set out to repeat and extend his findings, one led by Rudolf Jaenisch of the Whitehead Institute and the other by Kathrin Plath of the University of California, Los Angeles, and Konrad Hochedlinger of Massachusetts General Hospital. Dr. Yamanaka, too, set about refining his work.
In articles published today in Nature and a new journal, Cell-Stem Cell, the three teams show that injection of the four genes identified by Dr. Yamanaka can make mouse cells revert to cells indistinguishable from embryonic stem cells. Dr. Yamanaka’s report of last year showed that only some properties of embryonic stem cells were attained.
This clear confirmation of Dr. Yamanaka’s recipe is exciting to researchers because it throws open to study the key process of multicellular organisms, that of committing cells to a variety of different roles, even though all carry the same genetic information.
Recent studies have shown that the chromatin, the complex protein material that clads the DNA in chromosomes, is not passive packaging material but highly dynamic. It contains systems of switches that close down large suites of genes but allow others to be active, depending on the role each cell is assigned to perform.
Dr. Yamanaka’s four genes evidently reset the switch settings appropriate for a skin cell to ones that specify an embryonic stem cell. The technique is easy to use and “should revolutionize the field since every small lab can work on reprogramming,” said Alexander Meissner, a co-author of Dr. Jaenisch’s report.
An immediate issue is whether the technique can be reinvented for human cells. One problem is that the mice have to be interbred, which cannot be done with people. Another is that the cells must be infected with the gene-carrying virus, which is not ideal for cells to be used in therapy. A third issue is that two of the genes in the recipe can cause cancer. Indeed 20 percent of Dr. Yamanaka’s mice died of the disease. Nonetheless, several biologists expressed confidence that all these difficulties will be sidestepped somehow.
“The technical problems seem approachable — I don’t see anyone running into a brick wall,” said Owen Witte, a stem cell biologist at the University of California, Los Angeles. Dr. Jaenisch, in a Webcast about the research, predicted that the problems of adapting the technique to human cells will be solvable but he did not know when.
If a human version of Dr. Yamanaka’s recipe is developed, one important research use, Dr. Weissman said, will be to reprogram diseased cells from patients so as to study the molecular basis of how their disease develops.
Beyond that is the hope of generating cells for therapy. Researchers have learned how to make embryonic cells in the laboratory develop into neurons, heart muscle cells and other tissues. In principle these might be injected into a patient to replace or supplement the cells of the diseased tissue, without fear of immune rejection. No one really knows if the new cells would succumb to the same disease process, or if they would be well behaved, given that they developed in a laboratory dish without recapitulating the exact succession of environments they would have experienced in the embryo.
Still, repairing the body with its own cells should in principle be a superior form of medicine to the surgeon’s knife and the oncologists’ poisons.
But the first fruit of the new technique will be in figuring out how cells work.
This and other methods will lead to an explosion of information that will “open the door for understanding how cells program and re-program their fate,” Dr. Scadden predicted. If and when applicable to human cells, he said, the four-gene approach “will have profound implications for new biology, regenerative medicine and will change the ethical debate around stem cells.”
By NICHOLAS WADE
Published: June 6, 2007
The advance is an easy-to-use technique for reprogramming a skin cell of a mouse back to the embryonic state. Embryonic cells can be induced in the laboratory to develop into many of the body’s major tissues.
If the technique can be adapted to human cells, researchers could use a patient’s skin cell to generate new heart, liver or kidney cells that might be transplantable and would not be rejected by the patient’s immune system. But scientists say they cannot predict when they can overcome the considerable problems in adapting the method to human cells.
Previously, the only way to convert adult cells to embryonic form has been by nuclear transfer, the insertion of an adult cell’s nucleus into an egg whose own nucleus has been removed. The egg somehow reprograms the nucleus back to an embryonic state. That procedure is known as therapeutic cloning when applied to people, but no one has yet succeeded in doing it.
The new technique, developed by Shinya Yamanaka of Kyoto University, depends on inserting just four genes into a skin cell. These accomplish the same reprogramming task as the egg does, or at least one that seems very similar.
The technique, if adaptable to human cells, is much easier to apply than nuclear transfer, would not involve the expensive and controversial use of human eggs, and should avoid all or almost all of the ethical criticism directed at the use of embryonic stem cells.
“From the point of view of moving biomedicine and regenerative medicine faster, this is about as big a deal as you could imagine,” said Irving Weissman, a leading stem cell biologist at Stanford University, who was not involved in the new research.
David Scadden, a stem cell biologist at the Harvard Medical School, said the finding that cells could be reprogrammed with simple biochemical techniques “is truly extraordinary and frankly something most assumed would take a decade to work out.”
The technique seems likely to be welcomed by many who have opposed human embryonic stem cell research. It “raises no serious moral problem, because it creates embryonic-like stem cells without creating, harming or destroying human lives at any stage,” said Richard Doerflinger, the United States Conference of Catholic Bishops’ spokesman on stem cell issues. In themselves, embryonic stem cells “have no moral status,” and the bishops’ objections to embryonic stem cell research rest solely on the fact that human embryos must be harmed or destroyed to obtain them, Mr. Doerflinger said.
Ronald Green, an ethicist at Dartmouth College, said it would be “very hard for people to say that what is created here is a nascent form of human life that should be protected.” The new technique, if adaptable to human cells, “will be one way this debate could end,” Mr. Green said.
Biologists learned how to generate human embryonic stem cells in 1998 from the few-day-old embryos discarded by fertility clinics, a procedure the embryos did not survive. This source proved controversial, and biologists supported by federal financing were unable to explore the new opportunity until August 2001 when President Bush, in a political compromise, decreed that research on human embryonic stem cells could begin, but only with cell lines already in existence by that date.
The restrictions have caused considerable frustration among biologists and other supporters of research on embryonic stem cells. Indeed, the House is expected to vote today to increase federal funds for such research. If approved, the bill, similar to one approved by the Senate, would go to the president. The White House has already said that the president would veto it.
The new technique, when adaptable to human cells, should sidestep all these problems. James Battey, vice chairman of the National Institutes of Health stem cell task force, said he saw “no impediment at all” to federal support of researchers using the new technique on human cells.
Ever since the creation of Dolly, the first cloned mammal, scientists have sought to lay hands on the mysterious chemicals with which an egg will reprogram a mature cell nucleus injected into it and set the cell on the same path of embryonic development as when egg and sperm combine.
Years of patient research have identified many of the genes that are active in the embryonic cell and maintain its pluripotency, or ability to morph into many different tissues. Last year Dr. Yamanaka and his colleague Kazutoshi Takahashi, both at Kyoto University, published a remarkable report relating how they had guessed at 24 genes responsible for maintaining pluripotency in mouse embryonic stem cells.
When they inserted all 24 genes into mouse skin cells, some of the cells showed signs of pluripotency. The Kyoto team then subtracted genes one by one until they had a set of four genes that were essential. The genes are inserted into viruses that infect the cell and become active as the virus replicates. The skin cell’s own copies of these genes are repressed since they would interfere with its function. “We were very surprised” that just four genes are sufficient to reprogram the skin cells, Dr. Yamanaka said.
Dr. Yamanaka’s report riveted the attention of biologists elsewhere. Two teams set out to repeat and extend his findings, one led by Rudolf Jaenisch of the Whitehead Institute and the other by Kathrin Plath of the University of California, Los Angeles, and Konrad Hochedlinger of Massachusetts General Hospital. Dr. Yamanaka, too, set about refining his work.
In articles published today in Nature and a new journal, Cell-Stem Cell, the three teams show that injection of the four genes identified by Dr. Yamanaka can make mouse cells revert to cells indistinguishable from embryonic stem cells. Dr. Yamanaka’s report of last year showed that only some properties of embryonic stem cells were attained.
This clear confirmation of Dr. Yamanaka’s recipe is exciting to researchers because it throws open to study the key process of multicellular organisms, that of committing cells to a variety of different roles, even though all carry the same genetic information.
Recent studies have shown that the chromatin, the complex protein material that clads the DNA in chromosomes, is not passive packaging material but highly dynamic. It contains systems of switches that close down large suites of genes but allow others to be active, depending on the role each cell is assigned to perform.
Dr. Yamanaka’s four genes evidently reset the switch settings appropriate for a skin cell to ones that specify an embryonic stem cell. The technique is easy to use and “should revolutionize the field since every small lab can work on reprogramming,” said Alexander Meissner, a co-author of Dr. Jaenisch’s report.
An immediate issue is whether the technique can be reinvented for human cells. One problem is that the mice have to be interbred, which cannot be done with people. Another is that the cells must be infected with the gene-carrying virus, which is not ideal for cells to be used in therapy. A third issue is that two of the genes in the recipe can cause cancer. Indeed 20 percent of Dr. Yamanaka’s mice died of the disease. Nonetheless, several biologists expressed confidence that all these difficulties will be sidestepped somehow.
“The technical problems seem approachable — I don’t see anyone running into a brick wall,” said Owen Witte, a stem cell biologist at the University of California, Los Angeles. Dr. Jaenisch, in a Webcast about the research, predicted that the problems of adapting the technique to human cells will be solvable but he did not know when.
If a human version of Dr. Yamanaka’s recipe is developed, one important research use, Dr. Weissman said, will be to reprogram diseased cells from patients so as to study the molecular basis of how their disease develops.
Beyond that is the hope of generating cells for therapy. Researchers have learned how to make embryonic cells in the laboratory develop into neurons, heart muscle cells and other tissues. In principle these might be injected into a patient to replace or supplement the cells of the diseased tissue, without fear of immune rejection. No one really knows if the new cells would succumb to the same disease process, or if they would be well behaved, given that they developed in a laboratory dish without recapitulating the exact succession of environments they would have experienced in the embryo.
Still, repairing the body with its own cells should in principle be a superior form of medicine to the surgeon’s knife and the oncologists’ poisons.
But the first fruit of the new technique will be in figuring out how cells work.
This and other methods will lead to an explosion of information that will “open the door for understanding how cells program and re-program their fate,” Dr. Scadden predicted. If and when applicable to human cells, he said, the four-gene approach “will have profound implications for new biology, regenerative medicine and will change the ethical debate around stem cells.”
By NICHOLAS WADE
Published: June 6, 2007
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