Controversial three-parent pregnancy revealed

[Guest guest]

http://www.newscientist.com/news/news.jsp?id=ns99994266

 

 

Controversial three-parent pregnancy revealed

12:55 14 October 03 NewScientist.com news service

A human pregnancy involving fetuses with three genetic parents was reported by

US and Chinese scientists on Tuesday. None were born, but the researchers say

this was due to obstetric complications rather than the fertility technique

used, and that it would work in future.

 

However, the approach is now reported to have been banned in China, where the

pregnancy was created. It was already banned in the US and UK, and the news of

the attempt has led to renewed criticism of fertility research by anti-abortion

groups.

 

Some children have already been born with three genetic parents, but the new

research has prompted additional controversy because the method used shares a

technical step, called nuclear transfer, with cloning procedures. However, the

US scientist who developed in animals the technique used by the Chinese

researchers says: " It's nothing to do with human cloning. "

 

Jamie Grifo, director of reproductive medicine at New York University, told New

Scientist that making such false links is detrimental to his patients. " This

fear of cloning has created a regulatory environment that has stopped a lot of

research in the area of fertility, and the problem is that patients who need it

will not get it. "

 

 

Egg swap

 

 

The work in China was led by John Zhang and colleagues at the Sun Yat-Sen

University of Medical Science in Guangzhou, China, and presented at the American

Society for Reproductive Medicine's meeting in San Antonio, Texas, US. They

removed the fertilised nuclei (pronuclei) from one set of eggs and implanted

them into another set of emptied eggs.

 

The eggs produced by this nuclear transfer had genetic material from three

people - nuclear DNA from the man and woman who created the pronuclei and

mitochondrial DNA from the woman donating the second egg.

 

Problems with mitochondrial DNA can cause infertility or disease and it was to

try to solve this problem that the research was done. The patient was a

30-year-old woman who could not have children despite repeated IVF attempts

because all her embryos arrested at the two-day stage of development.

 

Following nuclear transfer and " electrofusion " to reconstruct the nuclei in its

new egg, the researchers had five embryos that survived to the four-cell stage

after 48 hours. These were transplanted into the patient's womb and three

developed into pregnancies.

 

One fetus was then aborted, in an attempt to increase the survival chance of the

others. But one of the remaining pair died at 24 weeks of respiratory distress

due to premature rupture of the membranes. The other died at 29 weeks due to

cord prolapse.

 

" We don't consider this a success because of the outcome, " says Grifo. " But we

were happy to see that the embryos created a viable pregnancy. " He adds the

foetuses were " normal genetically and morphologically " .

 

 

Reprogramming required

 

 

Previous work, revealed in May 2001, did lead to successful births of babies

with genetic material from three people. But the approach used by led by Jacques

Cohen and Jason Barritt, at the St Barnabas Medical Center in New Jersey, did

not use nuclear transfer. Instead, the cytoplasmic fluid surrounding the nucleus

of cells - and containing mitochondrial DNA - was taken from healthy eggs and

injected into the eggs of women with fertility problems.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Grifo is upset that the approach he developed has been described as " very, very

close " to human cloning. In reproductive human cloning, the mature nucleus of an

adult cell is transferred to empty egg and requires " reprogramming " to start

developing like a newly fertilised zygote. Many of the health problems of cloned

animals have been attributed to faulty reprogramming.

 

The nuclear transfer technique used in the new Chinese work requires no

reprogramming, as the pronucleus transferred is from a normally fertilised egg

cell and is ready to develop naturally.

 

Azim Surani, at the University of Cambridge, UK, has carried out the technique

in mice and agrees it is " not comparable " with human cloning. He points out that

a commonly used IVF technique in which a sperm is injected directly into an egg

(ICSI) could be considered as a form of nuclear transfer.

 

And Sean Tipton, from the American Society for Reproductive Medicine, says: " I

don't think it's fair to be so frightened of the remote possibility of cloning

that we choke off the means of advancing infertility treatments. "

 

Shaoni Bhattacharya in San Antonio and Sylvia Pagán Westphal

 

 

 

 

 

The New with improved product search