‘The technique remains nevertheless an intervention on the germ line’
This possible new technique to prevent mitochondrial disease transmission , while it has major advantages, remains nevertheless an intervention on the germ line, and therefore should be carefully evaluated before use in humans, as any changes produced will not only be present in the individual born, but will be transmitted to their offspring.
There is currently no cure for diseases due to alterations in mitochondrial DNA (mtDNA).However, there are a number of techniques, more or less developed, that could prevent mother-to-child transmission of these hereditary diseases; these are known as mitochondrial donation techniques.Among these are pronuclear transfer (PNT) and maternal spindle transfer (MST), recently approved by the British Parliament for use in clinical trials.These techniques mean that children born using them will be genetically linked to three people: their parents (from which the nuclear DNA wouldcome), and a female donor of healthy mtDNA, which raises ethical, medical and safety issues.
Preventing mother to child transmission of hereditary deseases
However, a technique has recently been described that opens a new possibility for preventing mitochondrial disease transmission to offspring (Cell. 2015; 161: p. 459-69), known as mito-TALENs, from the acronym “mitochondria-targeted transcription activator-like effector nucleases”. This consists of the production of artificial restriction enzymes, the action of which is directed to specific points on the mtDNA to remove fragments affected by a mutation.
Mito-TALENshas two major advantages compared to mitochondrial donation techniques.First of all, it avoids the child being genetically related with three parents, preventing the possible psychological problems that this could have for the child (on perceiving a third parent), and the parents (on seeing their parental causal link violated).Secondly, this technique is much less aggressive with the oocyte (egg), which is safer for the future individual.Thus, mito-TALENs only requires injection of the messenger RNA molecule that will give rise to the specific restriction enzyme, while mitochondrial donation techniques require the extraction of all the nuclear DNA and its transfer to an oocyte or enucleated embryo containing the donor mitochondria.
The technique remains nevertheless an intervention on the germ line, and therefore should be carefully evaluated before use in humans, as the possible changes produced will not only be present in the individual born, but will be transmitted to their offspring.