Wednesday, March 25, 2015

The science of three-parent children

2015 has already been a significant year in the field of human medicine as February saw the UK become the first country in the world to legalise the generation of so-called 'three-parent' children. This marks a milestone for preventative genetics and embryology and offers hope to many people around the UK and beyond who would be unable to have healthy children otherwise. The votes to bring this into law were fairly comfortably won by those in favour - 382 vs 128 in the House of Commons (the lower house) and 280 vs 48 in the House of Lords (the upper house) - however there have been a number of vocal opponents to the measure. In this post I hope to explain just what the process involves, and why it is considered necessary by the majority of British MPs.

A cellular energy crisis

Mitochondria, as you may recall from a previous post, are the powerhouses of our cells. They metabolise a range of molecules derived from food at use them to generate energy in the form of another molecule, ATP. You would not last long without them - just try holding your breath for a few minutes, since anaerobic respiration is all a cell without mitochondria would be able to manage. It is not surprising, therefore, that problems with mitochondrial function can be fairly nasty. Mitochondrial diseases are a range of genetic disorders in which the proper role of the mitochondria is disrupted due to mutations in one of the genes responsible for making mitochondrial proteins. These diseases never completely knock out mitochondrial function (since an embryo with such a disease could never survive to full development) but still cause severe symptoms in sufferers. Depending on the exact mutation, these can include blindness, deafness, diabetes, muscle weakness, cardiac problems, and problems with the central nervous system. Prognoses vary from one disorder to the next, but they invariably shorten lifespan, often severely. Sufferers of Leigh's disease, for example, rarely live past 7 years of age, and spend their short lives experiencing muscle weakness, lack of control over movement (particularly of the eyes), vomiting, diarrhea, an inability to swallow, and heart problems, among others.