Cloning Mice

It's a boy! Scientists clone first male mouse

May 31, 1999 - AP - Wash.

The small club of clones, restricted until now to females like Dolly the sheep and Cumulina the mouse, has gone co-ed with the cloning of a male mouse, researchers said on Monday.

"Fibro" is also the first documented, live mammal cloned from adult cells that do not originate in the reproductive system, which suggests that adult animals can be cloned from any cell in the body at all.

Ryuzo Yanagimachi and Teruhiko Wakayama at the University of Hawaii say the technique is still tricky -- they only got one living mouse out of 274 tries -- but Fibro seems healthy and normal.

"He fathered two perfectly normal litters as of Monday (Thursday)," Yanagimachi said in an interview conducted by e-mail. "He is active and healthy."

Male animals have been cloned before, but only using fetal cells, which are much easier to clone because of their early stage of development.

A Japanese agricultural research institute also said it cloned a calf from the ear of an adult, but the research was not published in a peer-reviewed scientific journal -- the standard for science.

It is much harder to clone animals from adult cells -- Dolly, some Japanese heifers and Cumulina, the cloned mouse presented to the world by Yanagimachi and Wakayama last year, are rare examples.

They were made using cells related to reproduction -- Dolly from the mammary gland cell of a ewe and Cumulina from so-called cumulus cells, which nurture developing eggs inside the ovaries.

So many scientists had believed that there might be something unique about females, or perhaps even female reproductive cells, that made them amenable to cloning.

Wakayama and Yanagimachi, writing in the journal Nature Genetics, said it is now clear this is not the case. "Our results demonstrate that cloning using adult somatic cells is not restricted to female or reproductive cells," they wrote.

Using their "Honolulu technique", which differs slightly from the method that scientists in Scotland used to make Dolly, they created 274 mouse embryos using skin clipped from the tail of a male mouse and implanted them into surrogate mother mice.

"Only three of 274 transferred embryos reached full term," they wrote. "Three mice from tail-tip cells were born alive, all of them males with black eyes." Two died but one lived to adulthood and was the same reddish-brown color as the mouse whose tail was clipped.

The experiment means it might be possible to store an animal's complete genome, its collection of genes, using a tail snip or other cell instead of having to freeze an embryo, the researchers said. "Moreover, precious animals of either sex, for example endangered species and transgenic animals, can be propagated by cloning irrespective of their fertility status."

Much of the cloning research going on is part of commercial and scientific programs to create genetically engineered, or transgenic, animals. Mice are bred to carry human genes, for example, so that drugs can be tested on them.

PPL Therapeutics, the commercial arm of the Scottish laboratory where Dolly was made, breed animals that produce human proteins in their blood or milk and has teamed up with Geron to try to breed transgenic pigs whose organs contain human proteins for use in transplants.

Genetic engineering is hit-and-miss but researchers say they can create an animal that carries and expresses the genes just the way they want, and then clone it to get exact copies.

Hawaii Scientists Clone more than 50 mice, one after another

July 22, 1998

In what could be a big boost for all sorts of biomedical research, scientists in Hawaii have turned out more than 50 carbon-copy mice using what is believed to be a more reliable cloning technique than the one used to create Dolly the sheep. The scientific potential could be broad because mice are the best-understood and most commonly used animals in biomedical experiments. Having genetically identical copies of the same animal could speed research in fundamental biology and virtually every branch of medicine and drug development.

The University of Hawaii scientists, reporting in Thursday's issue of the journal Nature, describe their work as "the first reproducible cloning of a mammal from adult cells" extending at least three generations. They said it is a marked improvement over the method used to make Dolly, which other laboratories so far have failed to duplicate.

Biologists in the United States and Europe hailed the mice-cloning effort as having much greater potential than the cloning of more complex creatures such as Dolly or a pair of calves that were born earlier this month in Japan.

Researchers said that with the Hawaii cloning method, cattle and pigs could be reprogrammed with human genes to mass-produce proteins essential to treat illnesses such as diabetes and Parkinson's disease. Animals could custom-grow organs for transplantation. And because mice give birth three times a year, experiments employing identical rodents could progress more rapidly than those relying on slower-reproducing barnyard animals. The Hawaii scientists would not discuss whether their technique might make human cloning more feasible.

Researchers introduced four of the cloned mice -- all females -- Wednesday in New York. The original clone was named Cumulina after the type of cell used in its creation; she remained in Hawaii. Working in a windowless lab for 16 hours a day, the Hawaii group used an injection method dubbed the "Honolulu technique" to transfer genetic material from adult mice to an empty egg. In each of four experiments beginning in 1997, the team transferred up to 800 eggs containing adult genes into surrogate mice mothers.

Three survivors from the original group, including Cumulina, grew to adulthood. Those clones eventually yielded cells that by this week had generated more than 50 offspring. DNA testing by an independent laboratoryconfirmed that none of the rodents are carrying stray DNA from other mice.

The Hawaii group's emphasis on repeating the clones is an indirect rebuke of geneticist Ian Wilmut and his colleagues in Scotland who created Dolly in one out of 277 attempts in the lab. Repeating an experiment to verify a discovery is central to scientific research. But at least three other laboratories have failed to duplicate the sheep experiment using Wilmut's method over the past 18 months, prompting scientists to question whether Dolly is truly a clone.

In Thursday's issue of Nature, Wilmut and 17 other researchers in Britain reported that an exhaustive examination of Dolly's genes show that it is "extraordinarily unlikely" that the sheep is anything but a clone. Dolly was created by a technique known as electrofusion, in which the membrane of an egg was breached, the chromosomes were removed and the nucleus of an adult sheep cell with different genetic material was merged inside.

In the Honolulu technique, the nucleus of a cell from one mouse was injected through a tiny needle into an egg donated by a second mouse. The egg's original genetic package was removed. The donor nucleus came from cumulus cells, which surround the developing eggs in the ovaries of female mice. Up to 3 percent of the manipulated eggs developed into surviving clones, a much higher success rate than the electrofusion method had.