‘Three parent IVF’, ‘Two mothers one father babies’, ‘A Brave New World?’, ‘Playing God.’
The headlines extended from inspirational to sensational as they always do. As mitochondrial researchers, we waited with bated breath as the UK parliament voted on the three-parent IVF technology. The subsequent elation on their positive decision brought with itself important questions around the implications of this new method and brought public attention to mitochondria- a little organelle with a fascinating history… so let’s talk about it!
When life began on Earth, for millions of years it was in the form of single cell organisms such as bacteria. The tiny structure of single-celled organisms provided the large surface area to volume ratio, which was needed to produce the energy required to sustain function. A key event enabled the existence of multicellular life. This was the fusion of two organisms where one was captured and the resulting captive becoming a dedicated energy producing structure. Only one genome (DNA) sustained in the new organism EXCEPT for a few genes, which were best to be kept within the energy producer. We now know the energy producers as mitochondria. Human mitochondrial DNA codes for thirteen gene products, which form crucial portions of the respiratory chain complex – the seat for producing ATP (the energy molecule).
When an egg and sperm fuse to form a zygote- the beginning of a new life, each parent contributes one-half of a human genome to form one whole. Other than the tiny bit more from mom. Only the mother’s mitochondria become part of the zygote, not the father’s. In terms of a number of genes, this is only 13 more (the whole human genome is 30,000 genes). But the copies matter. We carry two copies of every gene (one from mom and one from dad), but when it comes to mitochondrial genes mom provides 100,000 copies and dad provides none at all.It has been discovered that many chronic degenerative diseases are manifestations of mitochondrial dysfunction. #FactClick To Tweet
As the zygote grows, the mitochondrial DNA replicates and is distributed in new cells. The mitochondrial DNA continues to replicate all throughout our lives even in adult cells, which have ceased to replicate their nuclear DNA. Mitochondrial DNA can accumulate mutations when exposed to oxidative stress. These mutations can overwhelm the respiratory capacity of a cell and lead to dysfunction and even cell death. The scientific community is now discovering that many chronic degenerative diseases are manifestations of mitochondrial dysfunction including, diabetes, multiple sclerosis, Parkinson’s disease, Alzheimer’s disease, muscle dystrophy and motor neuron disease. These chronic conditions are proving to be the greatest unmet medical need of the 21st century.
We also find that several healthy habits, which are known to keep chronic diseases at bay, such as healthy eating and exercise are hugely effective at maintaining mitochondrial function and preventing damage. If we think of our cells as excellent brand new cars, then, our moms have installed in these cars, fantastic engines. But by putting in bad fuel and keeping the car stationary we allow the engine to rust and wither away. Regular maintenance, sustained use, and good fuel extend the functional age of a car…. just like our bodies.
In rare cases, the mitochondria in eggs are faulty which makes it impossible for the fetus to carry on developing. These mothers are unable to carry a pregnancy to term and the three-parent IVF is a way to enable these parents to have a family. The nucleus from a mother is placed into the egg shell containing healthy mitochondria from the donor egg, sort of like placing a brand new engine. This technology is a brave step towards making healthier babies.
If like me, you were born in an old-fashioned way with two parents, the next time you see your mom remember to say ‘thanks for all the mitochondria’!!
Dr Radha Desai is a neuroscientist and works in London. Her research is focused on mitochondria and bioenergetics, with the specific aim of finding cures.