Given the worldwide attention for the 1997 announcement of the world’s first mammal clone, Dolly the sheep, the rarity of any mention of cloning these days could make you think nobody’s out there doing it (except, maybe, for those scientists insisting they can clone a mammoth dug up from the Siberian tundra).
Cloning didn’t go away, though. There is still a small community of scientists around the world using the technology. A handful are trying to make money at it—not very successfully—but most are using it as a science research tool.
How it works
Scientists use the term “somatic cell nuclear transfer” (SCNT) when they talk about cloning because the phrase is both technically correct and a lot less controversial. The process involves removing a nucleus from a somatic, or body, cell, and inserting it into an egg, or oocyte, that has had its own nucleus removed. After being activated by electricity or a chemical, the egg begins to divide as if it had been fertilized with a sperm cell. It forms a blastocyst with an inner cell mass of stem cells, the raw material that turns into a body. Placed in a womb, the blastocyst develops into a baby. The baby would be, for all practical purposes, a genetic twin of the donor. Only the DNA in cell mitochondria, contributed by the egg, would be different.
Dolly’s birth was a milestone. The problem, though, is that cloning was, and still is, wildly inefficient. The process fails far more often than it succeeds. So most nuclear transfer these days is aimed at understanding what’s inside the egg that transforms a single cell into something that can make an entire creature. Answers to that question could improve in-vitro fertilization (IVF), elucidate infertility, or provide clues to diseases and conditions related to development errors. “At this point,” says Shoukhrat Mitalipov, whose lab announced in 2013 that it had created human stem cells via SCNT, “nuclear transfer is a pure science project.”
One form of nuclear transfer has moved beyond science project. The United Kingdom recently approved a procedure in which the nucleus of one woman’s egg is placed into another’s egg that has had its nucleus removed as a way to avoid heritable mitochondrial diseases. It’s not cloning because the egg would be fertilized with a sperm cell, but cloning research established the viability of the technique.
No commercial need
Other than its role in academic biology’s toolkit, there’s very little cloning going on. Grant money is difficult to come by—no federal money can be used for human SCNT in the United States—and drug companies have zero interest in it.
The commercial agricultural market is tiny and shrinking. Gabor Vajta, a cloning pioneer and consultant based in Australia, told me that his country “had at least seven productive cloning units with commercial aspirations before and around the birth of Dolly. Now there is only one.”
That trend has been mirrored around the world. Vajta consults for a company in China called BGI Ark Biotechnology that makes pig clones for both agriculture and as models for human disease. And a U.S. company called Viagen clones cattle, horses, and goats, including bucking bulls for rodeos. But few people want, or need, to make clones of agricultural animals.
Some scientists are using cloning to preserve the genetics of endangered species. Martha Gomez, senior scientist at the Audubon Center for Research in New Orleans, has been making clones of endangered felines by using the eggs and wombs of domestic cats. So far she has succeeded in cloning the African wild cat, the sand cat, and caracals, though, in an example of cloning’s uncertainties, the caracal kittens died two months after birth. The clones are then bred with other members of the species to enrich and preserve the gene pool.
Ultimately, though, cloning isn’t what she really wants to do. Instead she hopes to use what she’s learned from SCNT to help create gametes—eggs and sperm—from stem cells.
Once we got over the fantasy of making copies of people, cloning settled into its real value as a research tool. Cloning is not an end in itself; it’s a path toward learning how a cell can make an entire living animal and where the process can go wrong. That research could affect the course of regenerative medicine, tissue engineering, embryology, and treatments for infertility and cancer.
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