Key Takeaways From Cumulina the Mouse:
- Cumulina followed Dolly the Sheep as a cloned mammal. This mouse demonstrated that mammalian cloning could be achieved more efficiently and repeatedly.
- Cloning could be a potential tool for regenerative medicine.
- Funding restrictions, ethical concerns, and other challenges have slowed human cloning research.
Almost three decades ago, biomedical scientist Ryuzo Yanagimachi had a huge secret. He was presenting at a research conference and wanted to announce a historic scientific breakthrough he had achieved at the University of Hawai‘i.
Scientist Steve Ward was in the audience, and he had previously worked with Yanagimachi.
“I warned him not to because he was under embargo by Nature,” Steve Ward, the interim associate dean for research and a professor at the Yanagimachi Institute for Biogenesis Research at the John A. Burns School of Medicine at the University of Hawai‘i, told Discover.
Yanagimachi heeded his colleague’s warning. But he did offer a teaser.
“So he ended his talk by saying, ‘I can’t tell you anymore. All I can tell you is that Dolly isn’t alone,’” Ward said.
Immediately, the audience understood that Yanagimachi had cloned a mammal. The revolutionary discovery sparked excitement about cloning's medical potential, but ethical debates, funding restrictions, technical challenges, and later advances in stem-cell biology limited its development.
Read More: Over 20 Years, One Mouse Was Cloned for 58 Generations — Until the Line Collapsed
Simplifying the Cloning Process After Dolly
In 1996, scientists first cloned Dolly the sheep in Scotland, making her the first successfully cloned mammal. Experts used a process called somatic cell nuclear transfer (SCNT) to clone her, according to the Cloning Source Book from Oxford University Press.
Explore All OptionsWorking with a cell from a six-year-old sheep, scientists removed the nucleus. They then took an egg cell from another donor, removed its nucleus, and replaced it with the nucleus from the first cell.
The cell advanced to an embryonic stage and was implanted in a surrogate mother. Dolly was then introduced to the world in early 1997 and dominated headlines.
Back in Hawai‘i, Yanagimachi and his research partner, Teruhiko Wakayama, considered how to simplify the process and developed a new technique.
What was the Cumulina Mouse?
Yanagimachi and Wakayama developed a new technique — cloning by nuclear microinjection (CNM), according to a study in Nature. In CNM, they used a micropipette to remove genetic material from a cell's nucleus. They then transferred it into an unfertilized egg whose chromosomes had already been extracted.
The team was successful. Not only did they clone Cumulina, but they also cloned dozens of mice and created a family tree spanning generations. (Cumulina lived a normal lifespan for a mouse and died before her third birthday.)
Scientists saw huge potential for human cloning in regenerative medicine. They imagined someday reversing degenerative diseases or growing new organs to replace failing ones.
“In my skin cells are the instructions to make a kidney,” Ward said. “If I could clone my skin cells and turn on the kidney genes in the lab, it’s possible I could make a kidney that I could replenish myself.”
Why Some Are Wary of Cloning
Researchers saw possibilities for healing, but people both inside and outside the scientific community questioned the morality of cloning human cells. In the early 2000s, politicians were pressured to exclude any project that involved human cloning from Federal funding.
“Real clones would have been the answers to the world’s problems,” Stefan Moisyadi, an associate professor at the Yanagimachi Institute for Biogenesis Research at the John A. Burns School of Medicine at the University of Hawai‘i, told Discover.
Ethical concerns and lack of funding led many researchers to back away from human cloning.
“The kind of promise of cloning ended there, because really, cloning for animals is being done all the time. But for humans, it’s a moot point. Nobody’s going to clone humans,” Moisyadi said.
While funding was one issue, so was failure. Most attempts to clone actually failed. A decade after successfully cloning Cumulina, Wakayama published a follow-up report stating that the success rate was below 5 percent, according to a study in J-Stage.
Although most scientists have stepped away from cloning, Ward hopes that greater public understanding could lead to a return of funding for CNM research for therapeutic purposes, such as organ replacement or the reversal of degenerative diseases.
“Cloning to me says: ‘Fund good research all the time,’” Ward said. “You never know what will come out of it.”
Read More: A Beginner's Guide To Cloning
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from the Cloning Source Book
- This article references information from a study published in Nature: Full-term development of mice from enucleated oocytes injected with cumulus cell nuclei
- This article references information from a study published in J-Stage: Production of Cloned Mice and ES Cells from Adult Somatic Cells by Nuclear Transfer: How to Improve Cloning Efficiency?
