For the first time, scientists have cloned monkeys using a technique roughly similar to one reported last week that produced Dolly, the sensational sheep. But experts disagree on whether the research--which was detailed at a press conference yesterday in Beaverton, Oregon, and has not yet been published--is simply a new twist on existing technology or a breakthrough for primate researchers.
Like Dolly's creators in Scotland, Don Wolf of Portland's Oregon Health Sciences University and his colleagues transferred the nuclei from donor cells to eggs whose own DNA had been removed. A key difference, however, is that Dolly's donor cell came from adult udder cells growing in lab dishes (see ScienceNOW, 24 February), while the donor cells used to create the monkey clones came from early embryos. For a decade, scientists have been using such embryonic nuclei to clone livestock. "So to me, [this result] is not such a big deal," says embryologist Richard Tasca of the National Institute of Child Health and Human Development in Bethesda, Maryland.
Wolf's group created the donor embryos using in vitro fertilization. After the fertilized eggs had divided three times to produce eight-celled embryos, the scientists separated the cells and fused each one with either a newly fertilized egg, an egg past its prime fertilization time, or an egg ripe for fertilization. Of the dozens of eggs receiving nuclei, only the ripe ones developed into offspring that survived. According to Wolf, who carried out the work while at the Oregon Regional Primate Research Center in Beaverton, the team now is raising two apparently healthy 8-month-old monkey clones: a male, Ditto, and a female, Neti.
While the cloning technique may be old hat, the fact that it has proven itself in monkeys is drawing applause from some experts. Wolf "has done a tremendous service for primate research," says reproductive physiologist Catherine VandeVoort of the California Regional Primate Research Center in Davis. Monkeys are key models for biomedical research, but individual genetic variation can skew results. "By creating clones," she says, "it opens up entirely new avenues for research."
One such avenue, Wolf says, is that researchers may be able to delete key monkey genes--a procedure commonly done in mice whose populations are more homogeneous--and easily evaluate the effects in clones. However, "given the inefficiency and how [costly] the monkeys are," Tasca says, it could be awhile before knockout monkeys become a common research tool.