Science Questions

Can gene therapy alter reproductive cells?

Sat, 13th Oct 2012

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Question

Ricardo Santiago asked:

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.  Thatís what would be needed to prevent a mutated version of a gene from being passed on and causing disease.  The problem is, we donít know what the long term consequences of germ line gene therapy would be for children born as a result.  

Itís 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 childís 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 thatís 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 isnít in the main nuclear genome itself.  Itís 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 thatís 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 donít 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 youíve got any questions about genes, DNA, and genetics that youíd like us to answer, just email them to genetics@thenakedscientists.com, tweet us @nakedgenetics, or post on our Facebook page, and weíll do our best to answer them.

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Ricardo Santiago asked the Naked Scientists: 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 What do you think? Ricardo Santiago , Sun, 20th Nov 2011

Certainly one option that is being practiced is artificial insemination, which would allow prospective parents to choose donors with the desired characteristics.

Most of the current gene therapies involve viral delivery vectors.  However, the sex organs are somewhat protected from the viral therapies. 

In the future, however, there may be the ability to directly manipulate the genes and chromosomes in an egg, and thus treat a possible disease prior to implantation.  Doing so would certainly be controversial.  If it was done with additive mechanism of inserting new DNA without making a splice, then it could cause problems for second-generation children.

Artificial insemination with donor eggs or sperm would likely be much cheaper, and perhaps more stable. CliffordK, Thu, 1st Dec 2011

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