Dolly the sheep’s clones looking good, good, good and good at 9
When Dolly the sheep was born 20 years ago, the University of Edinburgh’s famous girl was the first mammal created by way of true cloning. Her embryo was created not using the sex or stem cells of another sheep, but from mature cells taken straight from the donor’s mammary tissue.
Then, at age five — middle age, for a sheep living the good life in a research facility — Dolly developed osteoarthritis. She died at the age of six, riddled with joint and lung problems reminiscent of old age. When researchers examined the length of her telomeres — structures at the end of DNA that shorten with each replication, creating cells with shorter telomeres as the body ages — they found that her biological age surpassed her chronological age; her cells looked as if they’d been ticking for longer than she’d been alive. Some worried that this meant clones would age prematurely, carrying the same biological clock as the adult cells they’d been created from. From a biomedical standpoint, this would spell disaster, with any tissues or or- gans created from the cells of healthy adults running on a shortened biological clock.
But according to research published Tuesday in Nature Communications, Dolly’s premature aging isn’t likely to extend to all clones or tissues formed using adult cells. In fact, four sheep clones formed from the same cell line as Dolly seem to be in perfect health and are now pushing nine years of age.
“When we did the study, these clones were already two-and-a-half years older than Dolly was when she died,” lead study author Kevin Sinclair of the University of Nottingham told the Washington Post. “And they appeared to be perfectly healthy, but we wanted to see if they might be harbouring subtle defects.”
Sinclair and his colleagues failed to measure the telomere lengths of these Dollies (and another nine cloned sheep from other cell lines that they studied along with them). They’ll investigate molecular aging in about a year, when the sheep — which will then have reached the truly impressive sheep age of 10, a milestone rarely seen in farm animals — are humanely put down.