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Clones From Aged Cows Have Normal Pregnancies and Calving
(Released: 06/ /01)

By David Bauman, Office of University Communications

STORRS, Conn. -- Researchers at the University of Connecticut announced today (June 5) that a Holstein heifer named "Daisy", cloned two years ago from an aged cow, has given normal birth to a 90-pound male calf.

The calf named "Norm," was born at the UConn Kellog Dairy Center at 9 a.m. on Sunday, June 3, said Dr. Xiangzhong (Jerry) Yang, head of UConn's Transgenic Animal Facility. "Daisy gave birth without any assistance," Yang said. "Both the Mom and calf are doing fine."

Scientists have previously reported on cloned cows giving normal births in Japan, but these clones were made from young donor cows or from unknown slaughterhouse animals.

What makes Norm's birth special, researchers say, is that Daisy was cloned from an aged animal (passed menopause). The fact that Daisy can reproduce normally demonstrates that the cloning process can reverse the physiological age process, similar to conventional reproduction.

Ever since researchers in Scotland electrified the world by cloning "Dolly" the sheep, scientists were concerned that cloned animals might prematurely age, reflecting the age of the DNA of the animals from which they were cloned. Recently, Yang's team reported in the journal Nature Genetics that all clones have normal cells with regard to telomeres (lengths of DNA on the ends of chromosomes), and are indistinguishable from calves produced from conventional reproduction. Their results showed that cloned calves do not have cells that are unnaturally old and do not inherit the cellular genetic age of their donor. Similar results have been found in cattle by the Worcester, Mass.-based company Advanced Cell Technology, and in mice by the Rockefeller University.

"Although it might be anticipated that clones from aged animals may have normal reproductive capacity as those cloned from young animals, the normal birth of 'Norm' and several other normal pregnancies from aged clones here at UConn provides evidence that when you clone from an aged individual, you do not get an aged copy," Yang said.

Despite other reported problems associated with cloning, including high rates of abortion and neonatal death, Yang said research has shown that cloned animals, once they have passed the first few critical days after birth, can live and reproduce like conventionally reproduced animals. Yang notes that his UConn research team and their Japanese collaborators have produced several dozen clones from adult cattle, male and female. Almost all the surviving clones appear as normal as other calves.

"These findings are significant because of their important medical implications," added Yang. He suggested that Norm's successful birth moves science a bit closer to the promise of "Therapeutic cloning," in which human's own cells would be harvested for tissues that could treat diseases such as diabetes or Parkinson's.

"Therapeutic cloning is aimed to convert skin cells or other somatic (body) cells from diseased individuals to embryonic stem cells, which may then be differentiated into any needed cell or tissue types for therapy," Yang said. "Obviously demonstration that clones from aged animals can develop and reproduce normally is important, because when therapeutic cloning is eventually applicable to human therapy, older individuals are likely to be the intended beneficiaries for treatment.

This implies that when cells are harvested from old individuals for therapeutic cloning one can expect that these cells can be converted to fresh young cells as those from young individuals," he said.

"Norm's birth is also significant for agriculture and saving endangered species," Yang added. "Proven valuable animals are desired to be cloned and normal reproductions of the clones are of course desired."

Daisy was cloned from a 13-year-old high-merit cow named "Aspen," and was born at UConn on July 7, 1999.

Daisy is the fourth live-clone produced at UConn. Her other sister - the now famous "Amy" - was born on June10, 1999, becoming the first clone of an adult large animal in North America. A total of 10 clones have been produced from Aspen, the aged cow, including Amy, Betty, Cathy and Daisy, who are still alive. Betty and Cathy are also pregnant and due to calve soon.

Aspen, who also is still alive, is now nearly 15 years old and has long passed her calf-bearing age. Aspen had a high milking record, producing approximately 35,000 pounds of milk per year. It is yet to be determined whether her clones will have the same high milk production ability.

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