Is Britain about to have “three-parent babies”?

Recent press coverage suggests that the UK could be the first country to have three-parent babies.  But what are they, and why go to the effort of making them?

What motivated this story?

The Human Fertilisation and Embryology Authority (or HFEA) has reviewed the efficacy and safety of “mitochondrial replacement techniques”.  On the 3rd of June, the Expert Panel conducting the review released a report.  Quoting from their findings:

the panel reached a view that the evidence it has seen does not suggest that these techniques are unsafe.

But:

there are still experiments – some critical, some desirable – that need to be completed before clinical treatment should be offered.

As you might have guessed, “mitochondrial replacement techniques” is a more appropriate term for “three-parent babies”.  These techniques allow the DNA of three individuals to be inserted into the embryo.  But how?

What are mitochondria, and why replace them?

The cells in your body contain two sources of DNA – the nucleus, and the mitochondria.  Mitochondria are sometimes called “cellular power plants”, as they’re responsible for generating chemical energy for the cell.  The fact that mitochondria have their own DNA appears to be a quirk of evolution.  In the early days of life on Earth, eukaryotic cells engulfed a form of bacteria (the mitochondria), and found the arrangement extremely advantageous (biologists refer to this as a symbiotic relationship).

So we have nuclear DNA (nDNA), and mitochondrial DNA (mtDNA).  Your nDNA is a mix of your mother’s and father’s nDNA, but your mtDNA is exclusively from your mother’s mitochondria.  This also means that if there are genetic imperfections in your mother’s mtDNA, your genome doesn’t have the possibility of using a backup copy from your father.

mtDNA only makes up a small percentage of the DNA total, but faulty mtDNA can cause serious illnesses and genetic diseases (this link has a detailed table of some of these).  Also, because mtDNA is inherited only from the mother, if the mother has a disease inherited through mtDNA, the child is extremely likely to also develop the condition.  Faulty mtDNA can also be responsible for miscarriages.

Mitochondrial replacement techniques replace “defective” mtDNA with mtDNA from another woman, to create genetically healthier offspring.  This can be done in two ways:

maternal spindle transfer takes an egg from the donor with healthy nDNA and mtDNA, and inserts the mother’s nDNA.

pronuclear transfer uses two fertilised eggs, and swaps the nDNA.  This requires the embryo to still be a single cell, and not to have undergone differentiation.

Medical professionals prefer “mitochondrial replacement” to “three-parent children” because the latter suggests that all three DNA donors are represented equally in the offspring’s DNA, which isn’t the case.  The vast majority of the DNA comes from the traditional mother-father pair, and only a very small amount from a donor.

How does the media report the story?

The Telegraph report the story fairly, going to great lengths to obtain quotes from relevant authorities, as well as quoting from the press release accompanying the release of the report.  They note that critics of these techniques claim it will lead to “designer babies“, but they do not name or quote these critics.

The Daily Mail also give a relatively fair assessment of the story, although they suggest that these treatments could be clinically available within 2 years, a figure I couldn’t verify from the report.  This figure gets repeated by the BBC, who attribute it to Professor Robin Lovell-Badge, a member of the expert panel:

I think that [two years] is not a bad estimation. The other sorts of experiments that we thought were necessary, again it will take about two years to complete all of those.

The quote suggests to me that the professor was asked a leading question, so I would take this with a pinch of salt.  Also, this clashes somewhat with the Daily Mail’s “three parent babies could be a reality ‘within two years'” headline.  The BBC also quotes Prof Mary Herbert from Newcastle University, who is an expert in the field, who suggests the process could take up to five years to become available.

The bottom line

This review suggests that the HFEA want to see this procedure available for clinical treatment, as soon as experiments and trials indicate it is safe to do so.  The experimental data so far suggests that mitochondrial replacement is safe for many forms of primate, such as macaques, and it won’t be long before humans have access to this treatment (although possibly not within 2 years).

Some ethical concerns remain: the Nuffield Council reported on this in 2012, concluding that such treatments can be ethical if the right conditions are met (the Council have an excellent page outlining the ethical issues), and the Council is cited by the HFEA review in its report.  There are obvious religious concerns too – some argue that such actions are “playing God”, or the “thin end of the wedge”.  Indeed, the debate is quite similar to the debate regarding IVF in the 1970s (as a side note, men inherit their Y chromosomes along the paternal line, and defects in this case are much harder to correct, even with IVF).

This debate will continue, but the science of mitochondrial replacement also continues, with endorsements from independent regulators and charities encouraging the government to legislate for them.  It seems that three-parent babies are indeed in our future.