Scientists Produce Monkeys With DNA From Two Mothers
Thursday, August 27, 2009
Scientists have produced monkeys with genetic material from two mothers, an advance that could help women with some inherited diseases have healthy children but that would raise a host of safety, legal, ethical and social questions if attempted in people.
Using cloning-related techniques, the researchers developed a way to replace most of the genes in the eggs of one rhesus macaque monkey with genes from another monkey. They then fertilized the eggs with sperm, transferred the resulting embryos into animals' wombs and produced four apparently healthy offspring.
The technique was developed for women who have disorders caused by defects in a form of DNA passed only from females to their children, and the researchers said they hope the work will eventually translate into therapies for people.
"We believe this technique can be applied pretty quickly to humans and believe it will work," said Shoukhrat Mitalipov of the Oregon Health & Science University in Portland, who led the work, published online Wednesday by the journal Nature.
Many scientists hailed the research as a technically impressive feat that could help many families rid themselves of a variety of terrible disorders caused by defects in genetic material known as mitochondrial DNA.
"This is of great importance. This approach will be beneficial to many families," said Jan Smeitink, a professor of mitochondrial medicine at Radboud University Nijmegen in the Netherlands.
But the work could also raise thorny ethical and legal issues, including questions surrounding the creation of offspring with DNA from two mothers and a father.
"With this you have potentially three genetic parents," said David Magnus, director of Stanford University's Center for Biomedical Ethics. "This will create the potential for legal and social conflicts."
If applied to people, the work would permanently alter genes for their future generations, violating a long-standing taboo against tinkering with the "germline" because of the chance of unforeseen consequences. Some experts worry, too, that germline genetic manipulation would give rise to a market in expensive elective genetic enhancements.
The researchers acknowledged that the work might raise ethical questions but said those must be balanced against the potential benefits.
"We realize this is not just a simple form of gene therapy. This type of gene therapy involves replacing genes in the germline which of course will be transmitted to next generations, which is a concern," Mitalipov said. "However, we're talking about patients and birth defects that cause terrible diseases due to these gene mutations. So the only way to prevent these birth defects is to replace these genes."
Mitochondrial DNA is found inside structures in cells called mitochondria, which are often referred to as the "power plants" for cells because they provide energy for growth and other functions. But defects in mitochondrial DNA can cause a variety of disorders that may occur in about one of every 5,000 people and that can cause a wide spectrum of health problems, including stunted growth, muscle weakness, blindness, deafness, mental retardation, diabetes, seizures and dementia. Defects in this DNA may also sometimes be involved in more common disorders including Alzheimer's, Parkinson's and Huntington's diseases.