Mitochondrial dysfunction, which leads to rare genetic disorders in children, some forms of heart disease, and most likely some cases of Parkinson’s disease, is bewildering in the variety and complexity of problems it can cause. 

Mitochondria are, after all, the energy factories contained inside most of our cells, they convert the diverse food we consume into a common energy type. No energy, no life. 

Research has been ongoing since the late 19th century. The prevailing theory, based on the fact that mitochondria have their own genome (yes, you have two, this second one being very narrow in scope) is that they arose as a bacterial intruder in ancient cells, a parasite provided either protection or energy for another and eventually they became entwined and had an evolutionary advantage. They retain a degree of autonomy, and still manufacture some of their most crucial components, which are encoded by the mitochondrial DNA, a relic of the intruder's original genome.

 The goal now is to understand how mitochondria interact with other cellular components to maintain physiological homeostasis, and how mitochondrial defects lead to pathological states. It gets surprisingly little attention or funding compared to diseases with better public relations campaigns, like childhood brain cancer.

"For the past decade our focus has been on a particular 'back-up' system found in the mitochondria of lower organisms, but which has been lost during the evolution of complex animals such as humans or fruit flies. This back-up system kicks in when the regular energy-generating system of the mitochondria is overloaded, damaged or poisoned, protecting the cell against the harmful stresses of having a malfunctioning 'engine'. Indeed, mitochondria can be thought of rather like a car engine, that burns fuel (food molecules), and recovers the energy in a useful form to drive the processes of life. A malfunctioning engine imparts less energy but also creates toxic by-products as a result of incomplete combustion. Mitochondria are very similar," says University of Helsinki Director Howy Jacobs.

Jacob's team has transplanted the back-up or 'alternative' respiratory machinery from the mitochondria of lower organisms to human cells, showing that it can protect against pathological stresses, and even lethal poisons like cyanide, that target the mitochondria.

Obviously the human genome is no longer inviolate, when any direct or permanent manipulation of it has been regarded as unethical. In the UK, mitochondrial transplantation is likely to help over 100 children, a small subset of those who would otherwise be afflicted with mitochondrial disease but an important proof-of-concept. Soon we will acquire the means to prevent disease or reverse disease processes when they occur, by making such changes to the genome.

Is it ethical to engineer 'improvements' to what has evolved naturally, sometimes without being able to predict all the consequences? But equally, is it ethical to withhold life-saving technologies that can prevent suffering?