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Genetically modified human babies?

Australian scientists have criticised as "gung-ho" an experimental US infertility treatment which has set off a controversy surrounding the genetic modification of humans.

The comments follow widespread media publicity of a recent article in the journal Human Reproduction by Jason A. Barritt and colleagues which reports the technique has led to the birth of 30 babies.

Barritt and team reasoned that a certain type of infertility, in which embryos die before they can implant in the uterus, was caused by defective mitochondria - parts of the egg's cytoplasm that create energy for the cell. Based on this assumption, they used a technique called ooplasmic transfer, which involves replacing the cytoplasm of an old egg with the cytoplasm from a young egg.

"It's like putting new batteries in to the cells," said Professor Gab Kovacs of Monash IVF. "But we don't really know enough to know its implications."

Mitochondrial biologist Dr David Thorburn of Melbourne's Murdoch Institute agreed not enough was known to support its use in humans.

"It's unlikely that it would have an adverse effect on the child, but I think they have been rather gung-ho about it," he said.

Dr Thorburn said it was not clear that the so-called success of the technique could even be put down to the mitochondria specifically and that most IVF specialists were not convinced of the treatment's success.

Reproductive specialist, Dr Roger Short of Melbourne's Royal Women's Hospital agreed there was no evidence that mitochondria were the cause of the infertility in these cases or that adding new mitochondria would overcome the problem.

"It think it's a bit silly to jump into doing a human experiment by injecting mitochondrial DNA prior to fertilisation," he said. "Surely, they could have waited until they got some more conclusive results from animal experiments."

Genetically modified humans?

The twist is that mitochondria also contain DNA and Barritt and colleagues report the children born after the treatment carried mitochondrial DNA from the donor which could be passed on to future generations through the female line.

"This report is the first case of human germline genetic modification resulting in normal healthy children," the authors write.

Germline therapy usually refers to the manipulation of DNA in the nucleus of the egg or sperm for desired outcomes. Such "gene therapy" is currently used experimentally to treat diseases like haemophilia in adults. However, there has been significant debate about the ethics of using such techniques to engineer what some are callling "designer babies"

Over the weekend a frenzy of media reports claimed that the world's first genetically modified babies had been created using ooplasmic transfer. However, co-author Jaques Cohen of the Institute for Reproductive Medicine in New Jersey, has denied the claim.

"We haven't changed any genes," Reuters quotes Cohen as saying. "That's a huge step compared to the little thing that we did. But you could say there would have normally been mitochondria from only one source (the mother). Now there's mitochondria from two sources, and therefore there's two different types of mitochondria DNA there."

According to Dr David Thorburn, "it's a matter of semantics."

Dr Trevor Mudge of the Australian Medical Association's ethic's committee told the ABC he had reservations about the the procedure.

"It's venturing into territory which has enormous implications for future generations and over which there are too many quesion marks," he said.