NARA, JAPAN--Researchers here have reported the first successful cloning of adult cows. Their findings, to appear in the 11 December Science, reflect the intense effort under way in Japan to build a tastier steak: In recent months, five groups have produced a total of 19 calves cloned from adults as part of an ongoing government campaign to improve the quality of beef cattle.
Setting out to replicate the British researchers who cloned the sheep Dolly, a team at Kinki University used cells taken from the oviducts and cumulus, the tissue that surrounds the oocytes, or egg cells, of a single adult cow. The scientists starved the cells into quiescence, then transferred their DNA-carrying nuclei into egg cells stripped of their own nuclei. After reactivating the cells with an electric shock, the group grew several oocytes in culture to the blastocyst stage. They then selected 10 blastocysts and implanted them in five hosts. All became pregnant.
Despite the deaths of four calves at or soon after birth, the team's success rate with the implanted embryos is far higher than for any other group that has attempted to clone large mammals. Yukio Tsunoda, a professor of animal reproduction at Kinki, refers modestly to "beginner's luck," but most analysts point instead to Japan's extensive support for the latest biotech tools in livestock research. This spring Tsunoda hopes to have the first results from a systematic screening of cells, including a second batch of cloned calves produced using cells from 20 different tissues, including the liver, kidney, and heart.
His success with adult cells is good news for the cattle industry in Japan, where customers dine on $100-a-pound Matsuzaka beef roasts. But genetic quality control of cloned beef is not likely to prove economical in the United States and Europe. "We don't have a market for very high premium beef," says James Robl, professor of veterinary and animal sciences at the University of Massachusetts in Amherst. Scientists in other countries are more likely to work with fetal cells in efforts to modify an animal's genetic makeup so that its milk contains drugs for human use.