Tag Archives: Dolly

Closeup of Dolly. Credit: Geographic.

Dolly the cloned sheep did not age prematurely, suggesting cloning hazards have been exagerated

When the world’s first cloned animal died in 2003 at the age of six, many suspected the cloning process put Dolly into an early grave. A new investigation of the cloned sheep’s bones by scientists at the Universities of Glasgow and Nottingham suggests Dolly showed no signs of abnormal aging.

Closeup of Dolly. Credit: Geographic.

Closeup of Dolly. Credit: Geographic.

In 2004, researchers found that Dolly’s telomers — stretches of DNA at the end of our chromosomes which protect our genetic data like shoelace caps, allow cells to divide and hold some secrets to how we age and get cancer — were shorter than they should have been. This has prompted suspicions that the process of cloning itself might reduce lifespan, or that the famous clone’s painful osteoarthritis was the result of some inherent flaws with cloning.

Researchers gained access to the bones of Dolly, now housed at the National Museum of Scotland, but also those of her offspring Bonnie, as well as two other cloned sheep, Megan and Morag (two sheep cloned from non-adult cells who were prototypes for Dolly). All the bones were X-rayed for signs of arthritis. Megan and Bonnie died at the ripe old ages of 13 and nine, respectively, and showed some signs of arthritis, as is normal for their age. Morag died at age four due to the same lung virus that killed Dolly but did not show any signs of arthritis. Ultimately, the researchers concluded that arthritis is no more common among clones than ordinary sheep.

“We found that the prevalence and distribution of radiographic osteoarthritis were similar to that observed in naturally conceived sheep, and our healthy aged cloned sheep,” said Sandra Corr, professor of small animal orthopaedic surgery at Glasgow University.

“As a result we conclude that the original concerns that cloning had caused early-onset osteoarthritis in Dolly were unfounded.”

A researchers prepares a cloned sheep's bones for X-ray. Credit: University of Nottingham.

Researchers prepare a cloned sheep’s bones for X-ray. Credit: University of Nottingham.

Previously, Kevin Sinclair, a developmental biologist at the University of Nottingham and co-author of the new study, studied 13 cloned sheep — including four derived from the same DNA strand as Dolly — and concluded that there didn’t seem to be any evidence that indicates cloning has any long-term health risks. Dolly’s ‘four sisters’ all lived to be at least eight years old, which is the approximate equivalent of 70 in human years, and all lived a healthy life.  “They’re old ladies,” said Kevin Sinclair, a developmental biologist and lead author of the study of the 2016 study published in Nature Communications. “They’re very healthy for their age,” he added.

The Atlantic reports that since Dolly was cloned, a whole menagerie of other animals has been cloned as well: pigs, dogs, cats, monkeys etc. Studies that followed such clones found that their telomeres were shorter, normal or even longer. It all depended on the species and cloning technique.

That being said, this doesn’t mean that cloning is 100% safe. Scientists are still learning and more research is needed to investigate the full scope of cloning. For instance, a team from South Korea has recloned the world’s first cloned dog to investigate whether or not cloning shortens or affects lifespan in any way. So far, the nine-month-old pups are healthy and seem normal.

Dolly sheep clones show no long-term health issues

The four Nottingham Dollies. Credit: The University of Nottingham

The four Nottingham Dollies. Credit: The University of Nottingham

In an age where cloning animals is becoming more common and human genetic modification is right around the corner, scientists are still trying to figure out how safe the cloning process is. Now, three weeks after the 20th anniversary of the birth of Dolly the sheep, a study by researchers from The University of Nottingham suggests that four genomic clones of Dolly reached their 8th birthdays – around 65 in human years – with no health problems.

The four Finn Dorset sheep – also referred to as the Nottingham Dollies – are named Debbie, Denise, Dianna and Daisy. They were born in 2007 during the research of the late Keith Campbell, who was attempting to improve the efficiency of the somatic-cell nuclear transfer (SCNT) technique. Using the mammary gland cell line that led to the birth of Dolly, Campbell successfully cloned the Finn Dorsets.

The new research is the first detailed examination of age-related non-communicable disease in cloned offspring and was led by Kevin Sinclair, a close colleague of Campbell’s from The University of Nottingham.

“Despite technological advances in recent years’ efficiency of SCNT remains low but there are several groups across the world working on this problem at present and there is reason to be optimistic that there will be significant improvements in future,” Sinclair said.

“These improvements will stem from a better understanding of the underlying biology related to the earliest stages of mammalian development,” he added. “In turn this could lead to the realistic prospect of using SCNT to generate stem cells for therapeutic purposes in humans as well as generating transgenic animals that are healthy, fertile and productive. However, if these biotechnologies are going to be used in future we need to continue to test their safety.”

During the course of the study, the four clones underwent a series of comprehensive assessments for non-communicable diseases such as obesity, hypertension, and osteoarthritis. These assessments included X-rays, magnetic resonance imaging (MRI) scans, tests for glucose tolerance and insulin sensitivity, radio-telemetric assessments to determine heart rate and blood pressure and musculoskeletal examinations.

The results showed that the four clones showed no major health issues and no signs of premature aging – one of the early concerns of the cloned offspring. Although more research will need to be conducted until SCNT’s safety is certain, the current results are promising.

“It is well established that prior to conception and in the early stages of pregnancy during natural or assisted reproduction subtle chemical changes can affect the human genome leading to development and late-onset chronic diseases,” Sinclair said. “Given that SCNT requires the use of assisted reproductive procedures it is important to establish if similar diseases or disorders exist in apparently healthy aged cloned offspring.”

Journal Reference: Healthy ageing of cloned sheep. 26 July 2016. 10.1038/ncomms12359