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Cloning the Clone of a Famed Japanese Bull

By Nancy Touchette

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Sho-zaburo, a clone of a clone, the day after he was born.
Researchers have successfully produced a genetic clone of a bull they cloned several years ago. The bull calf—a clone of a clone—was born in Japan more than four years ago, but the birth was kept a secret until now because the researchers wanted to be sure the calf was healthy.

Xiangzhong Yang of the University of Connecticut in Storrs and Chikara Kubota of the Kagoshima Prefectural Cattle Breeding Institute in Kagoshima, Japan, made the Guiness Book of World Records in 2000 when they reported that they had cloned one of the most famous bulls of all time: Kamitakafuku, a 17-year-old Japanese bull that has been used to inseminate more than 350,000 cows.

The cloning of Kamitakafuku in 1998 resulted in the births of six offspring, and four calves survived.

Now, the researchers have created another success for the record books. They have cloned Saburo, one of Kamitakafuku’s clones. The effort produced two live calves in 200l; one clone died shortly after birth due to anemia, but the second, called Sho-zaburo or “Saburo Junior,” has thrived for the past four years in Japan.

From far to near: original donor bull (Kamitakafuku), first-generation clone (Saburo), and second-generation clone bull (Sho-zaburo).
“We kept it a secret for four years,” says Yang. “It’s a controversial field, and we didn’t want to jump into a big debate if we produced an abnormal clone. We wanted to make sure he would grow normally and have normal fertility.”

Although clones of clones have been produced in mice, this is the first time it has been done in a large animal. Yang and his colleagues have attempted unsuccessfully to produce a third generation clone—the clone of a clone of a clone.

Yang is not sure why his cloning attempts have succeeded. He employs a technique he developed in which the nucleus containing all of the bull’s genetic information is gently squeezed out of the donor cell and then transferred to a waiting egg cell from which the nucleus had been removed.

In the past, most cloning experiments called for aspirating the nucleus, or sucking the nucleus out of the cell, a process that Yang believes causes damage to the chromosomes. Researchers in Korea who announced the cloning of the first human embryo earlier this year used Yang’s more gentle technique for removing the donor nucleus.

Kamitakafuku, the “father” of the first and second set of clones, died in 2001 at the age of 21. His first set of cloned offspring—Saburo, Taro, Jiro, and Shiro—grew to be adults. Saburo and Shiro have fathered offspring through artificial insemination, as well as the old-fashioned way.

Kubota, C. et al. Serial bull cloning by somatic cell nuclear transfer. Published online in Nature Biotechnology (May 23, 2004).

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