Stem Cell Experiment FlawedInvestigators have found errors in high-profile research that had suggested a possible way around much of the ethical debate over human embryonic stem cells. The work, conducted five years ago by Catherine Verfaillie of the University of Minnesota at Minneapolis, claimed to prove the existence and value of a unique kind of bone marrow cell that appeared to have many of the traits of embryonic stem cells. Results appeared in two journals, including the prestigious British journal Nature.
Now an independent investigation -- prompted by questions raised by New Scientist magazine -- has concluded that a single diagram was duplicated and then wrongly labeled as two different diagrams in the two journals, and that a cell identification method used in the research was "significantly flawed," university officials acknowledged yesterday.
A spokeswoman said the university had cleared Verfaillie of misconduct and concluded that the errors were "an honest mistake." She said two stem cell experts asked by the university to assess anonymously the scientific impact of the flawed papers have offered conflicting opinions.
The cells showed the potential to morph into many kinds of body cells, suggesting that embryonic cells -- which, controversially, require the destruction of human embryos -- might not be needed for some therapies. Other scientists have long complained that they have been unable to replicate Verfaillie's work. But Verfaillie and colleagues have persevered, and the university plans to start testing them in people soon, the leader of that clinical trial said yesterday.
Verfaillie last year moved back to her home country of Belgium but retains a partial appointment at Minnesota. Chimps, Humans Split Later?A new study maintains that chimpanzees and humans split from a common ancestor just 4 million years ago -- much more recently than prevailing estimates of 5 million to 7 million years ago.
The researchers compared the DNA of chimpanzees, humans and our next-closest ancestor, the gorilla, as well as orangutans.
They used a well-known type of calculation that had not been previously applied to genetics to come up with their own "molecular clock" estimate of when humans became uniquely human.
"Assuming orangutan divergence 18 million years ago, speciation time of human and chimpanzee is consistently around 4 million years ago," they wrote in the journal PLoS Genetics.
Experts agree that humans split off from a common ancestor with chimpanzees several million years ago and that gorillas and orangutans split off much earlier, but it is difficult to date precisely when.
Asger Hobolth of North Carolina State University and colleagues from the University of Aarhus in Denmark and the University of Oxford in Britain looked at four regions of the human, chimpanzee and gorilla genomes, and the results directly contradicted some other recent research. They found evidence that it took only 400,000 years for humans to become a separate species from the common chimp-human ancestor.
-- From Staff Reports
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