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Doctors use cloning technique to impregnate an infertile woman.

Chinese researchers announced they had successfully used nuclear transfer, a cloning technique, to impregnate an infertile woman.

Scientists at Sun Yat-Sen University in Guangzhou, assisted by US researchers, removed the nucleus from a woman's egg, fertilized it in vitro with sperm from the father, and then inserted it into an enucleated donor egg. In cloning, the nucleus of an adult somatic (not egg) cell is transferred with the intention of creating a genetic copy of the lone parent.

Shortly after the procedure was completed, it was banned by the Chinese government. In 2001, the US Food and Drug Administration effectively halted such research by requiring regulated scientific studies demonstrating the safety of the procedure.

Some fertility clinics have championed nuclear transfer as a method to help women who are infertile because of defects in the energy-creating mitochondria of their eggs. The vast majority of a human being's genes are housed in the cell nucleus, but mitochondria, which surround the nucleus, have their own set of 13 genes. Normally, all of a person's mitochondrial DNA comes from his or her mother's egg-none comes from the father. This coupling of nuclear transfer with in vitro fertilization (IVF) would result in a child with DNA from the mother's egg, the father's sperm, and the mitochondria of the donor of the enucleated egg.

Presenting their findings at a meeting of the American Society of Reproductive Medicine in San Antonio, TX, the researchers said that while the 30-year-old woman was successfully impregnated, she gave birth prematurely to twins who did not survive. The fetuses were genetically normal but did carry the DNA of the donor eggs, the scientists said.

The nuclear transfer-IVF technique originally was developed by New York University's James Grifo, MD, who is named as an author of the Chinese study. Cytoplasmic transfer, a similar procedure used in the United States, involves injecting only the mitochondria-containing fluid from a donor egg into an infertile woman's egg. In 2001, Drs. Jacques Cohen and Jason Barritt at the Institute for Reproductive Medicine and Science of Saint Barnabas in New Jersey reported that 12 of 30 babies born with the help of cytoplasmic transfer carried donor mitochondria.

FDA spokeswoman Lenore Gelb said the agency could not comment on whether any US fertility clinics or other researchers have filed for clearance to investigate human nuclear transfer due to the confidentiality of such applications.
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Publication:Transplant News
Geographic Code:1USA
Date:Dec 31, 2003
Words:396
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