试管受精新技术可能规避新生儿先天疾病

 

A new technology aimed at eliminating genetic² disease in newborns would combine the DNA³ of three people, instead of just two, to create a child, potentially redrawing ethical⁴ lines for designer babies.

 

The process works by replacing potentially variant⁵ DNA in the unfertilized eggs of a hopeful mother with disease-free genes⁷ from a donor⁸. US regulators today will begin weighing whether the procedure, used only in monkeys so far, is safe enough to be tested in humans.

 

Because the process would change only a small, specific part of genetic code, scientists say a baby would largely retain the physical characteristics of the parents. Still, DNA from all three -- mother, father and donor -- would remain with the child throughout a lifetime, opening questions about long-term effects for this generation, and potentially the next. Ethicists worry that allowing pre-birth gene¹ manipulation may one day lead to build-to-order designer babies.

 

"Once you make this change, if a female arises from the process and goes on to have children, that change is passed on, so it's forever," Phil Yeske, chief science officer of the United Mitochondrial Disease Foundation, said by telephone. "That's uncharted territory; we just don't know what it means. Permanent change of the human germline has never been done before, and we don't know what will happen in future generations."

 

 

The Food and Drug Administration is scheduled today and tomorrow to explore the issue at a meeting, with doctors and researchers scheduled to talk. The FDA will then decide whether to allow scientists at Oregon Health & Science University in Portland, who engineered the approach, to move their testing program from macaque monkeys to woman.

 

Potentially, the procedure may cut off mitochondrial diseases that are passed down through females and occur in about 1 in 4,000 people. One example is Melas syndrome⁹, which causes a person to have continuing small strokes that damage their brains, leading to vision loss, problems with movement, dementia and death, according to the National Institutes of Health.

 

"What the FDA needs to think about is that this isn't a procedure to repair mitochondrial disease," said Vamsi Mootha, a professor of systems biology and medicine at Harvard Medical School inBoston who studies mitochondrial disorders¹⁰. "It's designed to prevent disease. It's designed to offer a woman who's a carrier for disease more options."

 

Shoukhrat Mitalipov, the researcher heading the Oregon team's work, declined to comment before the FDA meeting.

 

 

From 1997 to 2003, about 30 children worldwide were born using a method that injected donor mitochondria DNA into eggs after they were fertilized⁶. The first baby born with this technique wasreported in 1997. In 2003, though, the FDA told fertility clinics that genetically¹¹ manipulated embryos¹² were considered a biological product, and subject to regulation, essentially¹³ halting the technique in humans.

 

The lives of those children should be thoroughly¹⁴ investigated before the new procedure is cleared for use in a human trial, said Sheldon Krimsky, a professor of Urban & Environmental Policy & Planning at Tufts University in Boston.

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