“Scientists will be ready to create babies from three people in around two years, if it is made legal,” BBC News reports.
The main conclusion of the review is that the proposed techniques appear to be safe, but there are still a number of experiments that should be performed before treatments are offered to suitable patients.
There would also need to be a change to the law, ratified by parliament, before treatments could be legally offered.
What are mitochondrial diseases?
Almost all of the genetic material in our bodies is inside the cell nucleus that contains 23 chromosomes inherited from our mother and 23 inherited from our father. However, there is also a small amount of genetic material contained in cellular structures called mitochondria, which produce the cell’s energy. Unlike the rest of our DNA, this small amount of genetic material is passed to the child only from the mother. There are a number of rare diseases caused by gene mutations in the mitochondria. Women carrying these mutations will pass them directly to their child, with no influence from the father.
The IVF technique being considered aims to prevent these “mitochondrial diseases” by replacing the mother’s mitochondria with healthy mitochondria from a donor, thereby creating a healthy embryo. The child would then have the genetic material of three people – the majority still from the mother and father, but with around 1% of mitochondrial DNA coming from a donor.
What is mitochondria replacement?
There are two IVF mitochondria replacement techniques currently at the research stage, called pronuclear transfer and spindle transfer. These are the techniques under debate.
Pronuclear transfer involves an egg during the process of fertilisation. In the laboratory, the nucleus of the egg and the nucleus of the sperm, which have not yet fused together (the pronuclei), are taken from the fertilised egg cell containing the “unhealthy” mitochondria and placed into the donor-fertilised egg cell that has had its own pronuclei removed. This early stage embryo would then be placed into the mother’s body. The new embryo would contain the transplanted chromosomal DNA from both of its parents, but would have “donor” mitochondria from the other egg cell.
The alternative mitochondria replacement technique of spindle transfer involves egg cells prior to fertilisation. The nuclear DNA from an egg cell with “unhealthy” mitochondria is removed and placed into a donor egg cell that contains healthy mitochondria and has had its own nucleus removed. This “healthy” egg cell can then be fertilised.
Pronuclear transfer and spindle transfer are said to be potentially useful for the few couples whose child may have severe or lethal mitochondrial disease, and who would have no other option for having their own genetic child. It is estimated that in the UK, around 10-20 couples a year could benefit from these treatments.
How many children does mitochondrial disease affect?
It is estimated that around 1 in 200 children are born each year with some form of mitochondrial disease. Some of these children will have mild or no symptoms, but others can be severely affected – with symptoms including muscle weakness, intestinal disorders and heart disease – and have reduced life expectancy.
What ethical concerns have been raised about the techniques?
There are obvious ethical implications from creating an embryo with genetic material from three parents.
Among the questions raised are:
- Should the details of the donor remain anonymous or does the child have the right to know who their “third parent” is?
- What would be the long-term psychological effects on the child knowing it was born using donated genetic tissue?
Opponents of these types of treatments cite what can be broadly summarised as the “slippery slope” argument; this suggests that once a precedent has been set for altering the genetic material of an embryo prior to implantation in the womb, it is impossible to predict how these types of techniques might be used in the future.
Similar concerns were raised, however, when IVF treatments were first used during the 1970s; today, IVF is generally accepted.