Can gene therapy alter reproductive cells?

14 October 2012

Question

Dear Chris,

I guess it is already possible to identify that a person has a genetic disease that he/she would pass on to descendents. Is it likely that it will be possible, in the future, to genetically treat his/her reproductive cells to correct them and supress the transmission of said disease?

Best regards again!

Or, how we say here: Abraços,

Ricardo Santiago

Answer

Answered by Professor Jo Poulton from Oxford University.

Jo:: It is actually already possible to alter genes in germ line cells and this has already been done in several species including mice, sheep, and cows. That's what would be needed to prevent a mutated version of a gene from being passed on and causing disease. The problem is, we don't know what the long term consequences of germ line gene therapy would be for children born as a result.

It's possible that you might have mistargeted [the gene] and that other genes would be affected in the process when you were correcting an initial mutation. Many people also feel that this sort of therapy would be contravening a child's human rights as they would have no choice whether their genetic material was altered or not and actually also, that they would need to be followed up for long term into adult life to check up on the actual type of correction that's been done. There's also some concern that correcting genetic diseases this way could be the thin end of the wedge leading to designer babies.

But there is a group of diseases, inherited defects, where the defect isn't in the main nuclear genome itself. It's mitochondrial diseases where mitochondrial DNA is affected. So mitochondria, the powerhouses of the cell, they provide energy. They're actually descended from bacteria which paired up with cells about 2 billion years ago and became intracellular power supplies. Importantly, that event means that they have their own genome and many mitochondrial diseases are caused by defects in mitochondrial DNA. Mitochondria are inherited in egg cells, and because of this, the technology now exists to replace the damaged mitochondria that are maternally inherited carrying a disease with an IVF-type technique and this would prevent the baby from inheriting a disease. It would also mean that the child would have genetic material from both parents and from the egg then, so that's a 3-parent family. There's currently public consultation under way in the UK to discuss whether or not this will be ethically sound which I personally think it is. The problem is that because there are other options available which we already know are safe, which we don't know about nuclear transfer, it's likely to be many years before mitochondrial replacement would be offered outside very closely regulated clinical trials.

Kat:: That was Professor Jo Poulton from the University of Oxford. And if you've got any questions about genes, DNA, and genetics that you'd like us to answer, just email them to genetics@thenakedscientists.com, tweet us @nakedgenetics, or post on our Facebook page, and we'll do our best to answer them.

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