On the Shoulders of Giants: Prof. Doug Turnbull

Today, 3rd February, in a historic decision Members of Parliament have voted in favor of the ‘Three-Person Baby IVF Method’ whereby women with damaged mitochondria can have these removed and replaced by mitochondria from another healthy woman, prior to in vitro fertilization.

Mitochondria are small organelles found in all cells except sperm cells, and which provide us with the energy that we need. They are rod-shaped structures that resemble bacteria; in fact, it’s been established that very early in evolution eukaryotic cells embraced energy-generating bacteria in a form of symbiotic relationship to become more efficient at producing energy, and things have remained so to this day. So these bacteria-shaped structures called mitochondria can only be carried in women’s eggs as the sperm is very small and only carries the paternal part of the DNA. This is called ‘maternal inheritance’ of mitochondria, with the ethical implications being that any altered DNA will be passed on to children in subsequent generations. However, at present there are no specific cures for the many common and crippling mitochondrial diseases (such as epilepsy and heart disease), and this new genetic engineering technique is bound to improve the lives of many for generations. Thus, for women carrying mitochondrial mutations that lead to severe disease, their only option to produce disease-free offspring involves either egg donation or mitochondrial replacement in their unfertilized eggs.

The technique, developed in Prof. Doug Turnbull’s laboratory at Newcastle University is in effect a modification of in vitro fertilization that allows the replacement of damaged mitochondria for healthy ones (Figure 1). Although some scientists have raised the possibility that the new, transplanted, mitochondrial DNA might interfere with the paternal DNA in the nucleus, work in mice and macaques have not shown any adverse effects (Ref. 2). Thus, the potential risks proposed in human associated with mitochondrial replacement are tolerable in the light of the benefit that mitochondrial transfer will bring to millions of families all over the world.

Figure 1. A version of Doug Turnbull’s technique: (1) oocytes (eggs) from a mother with damaged mitochondria and a donor with healthy mitochondria are collected; (2) Most of the genetic material is removed from both eggs; and (3) the mother's genetic material is inserted into the donor egg, which can be fertilized by sperm by standard in vitro fertilization (Ref. 1).

Thus the UK is now set to become the first country to introduce laws regulating the creation of babies from three different people. The first attempt to perform this technique in humans might take place this year, with the first baby being born in 2016.

References

[1] BBC News 3rd February: http://www.bbc.com/news/health-31069173

[2] The Challenges of Mitochondrial Replacement:

http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1004315