Happy Birthday! Dolly the first cloned mammal turns 15

In February 1997, a friend and fellow science writer had been assigned to write a story about why mammals were unlikely to ever be cloned. A few days later that assignment changed with the February 22, 1997 announcement of Dolly the sheep — the first cloned mammal.

Although the announcement from the Roslin Institute in Scotland came in February, Dolly's actual birthday was 15 years ago today, July 5. According to Wikipedia, there are now 19 species of mammals that have been cloned, including — this one came as a surprise to me — water buffalo. The Roslin has posted a timeline of Dolly's life.

Cloning animals such as horses, cattle and pigs is now seen as a valuable way of propagating valuable livestock, and cloning endangered animals could help prevent their extinction.

The critical first step in animal cloning is to inject the nucleus of a cell from an adult animal into an egg that has had the DNA from its nucleus removed. The first step is called "somatic cell nuclear transfer" or SCNT. (The nucleus is the core of any cell and contains all the DNA.) In the lab, scientists stimulate the resulting egg to divide and begin forming an embryo.

Here is where reproductive cloning and stem cell research diverge. In reproductive cloning, that several day old embryo is placed in the womb of an animal and allowed to mature normally. In stem cell research, the cells of that several day old embryo are removed and used to generate animal embryonic stem cell lines.

I say animal lines because to date this process has not been reproduced using human DNA. All human embryonic stem cell lines come from embryos left over after in vitro fertilization.

The birth of Dolly sparked a national dialogue about the possibility of human reproductive cloning. In California, the legislature declared a five-year moratorium on any attempt at human reproductive cloning (SB 1344), and the California State Advisory Committee on Human Cloning was convened. This Committee strongly recommended against allowing any human reproductive cloning, as did the National Academies of Science, the International Society for Stem Cell Research and other state, federal and international agencies.

California is now one of a handful of states (listed here) with laws expressly prohibiting human reproductive cloning, and CIRM regulations also prohibit human reproductive cloning with our funds. As of yet, there is no federal law making human reproductive cloning illegal.

Even though all scientific organization that have weighed in on the topic strongly encourage laws against human reproductive cloning, those opposed to stem cell research still raise the specter of stem cell scientists trying to create new humans. In Minnesota right now there is proposed legislation that would ban both reproductive cloning and that first step, SCNT, which could lead to new stem cell lines. Scientists in Minnesota have argued that such legislation could slow the entire field of stem cell research in the state.

CIRM has funded three awards to scientists who are hoping to generate new stem cell lines through SCNT — the step in which an adult nucleus is placed in an egg. Here's a list of those awards. Renee Reijo Pera, who is one of those grantees, has argued that the technique would allow scientists to better understand the critical first few days of development, in which she says some diseases and birth defects originate.

Dolly died in February 2003 due to an infection, six years after the announcement of her existence shook up the scientific community and began a dialogue about human reproductive cloning that has yet to end. Hopefully by her 20th birthday we'll see a federal ban on human reproductive cloning that will put the conversation to rest.

A.A.