Associated Press | January 5, 2000 | By Rich Harris, Associated Press Writer
STORRS, Conn. - Ear cells from a prize Japanese bull, frozen and then cultured in a lab over several months, have produced successful clones, challenging the notion that cells become too stale to duplicate.
To date, cells used in cloning have generally been implanted either fresh or after fewer than 10 "passages," or periods in a culture medium, the researchers said.
But in the new study, ear cells from 17-year-old Kamitakafuku the bull went through up to 15 "passages" over three months before they were used to create calves.
The experiment at the University of Connecticut and the Kogashima Cattle Breeding Development Institute in Japan suggests that a library of cells could eventually be used to create clones at any time, even long after the original animals are dead.
It also means clones could be made from cells that have been kept in the laboratory long enough to do the meticulous - and slow - process of manipulating genes.
"This is very powerful stuff," said Dr. Thomas Wagner, the head of a cancer research center at Clemson University. "The approach ... is infinitely more valuable scientifically and commercially than that which has been done before."
Wagner was not involved in the study but has reviewed the findings, which were published Tuesday in the Proceedings of the National Academy of Sciences.
George E. Seidel of the animal reproduction center at Colorado State University was less impressed. He said the study is a "genuine advance" with implications for genetic research, but called the study "way oversold."
In the study, scientists led by Connecticut's Xiangzhong Yang collected Kamitakafuku's cells from an "ear punch" - a routine marking procedure similar to piercing a human earlobe.
The cells were cultured for two or three months, then their genetic material was placed in cow embryos and implanted in a surrogate mother.
Four calves were born from cells cultured for two months, two of which later died - one at birth, the other from a viral infection. Two more clones were born from cells cultured for three months.
The research suggests that scientists could decipher gene functions by knocking out specific genes and then studying the effects.
"If the embryo does not develop, we could say, 'Aha, that gene is vital for development,'" Yang said, "If the animal gets cancer or some other disease, we could say, 'Aha, that gene is integral to cancer.'"
This research has commonly been done with mice, which have limited value as models for humans and other animals.
In theory, the study is also another step toward manipulating genes "on the vine." Animals such as cows, which produce huge amounts of the milk protein casein every day, could be modified to produce a similarly large quantity of another protein or a drug, Wagner said.
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