The ‘three parent’ baby born this September is making global headlines, as it should being a most remarkable event. The baby has the DNA from the sperm of its father and the DNA from the nucleus of its mother, so far so normal. However the egg from which baby developed was from a third party. This egg had its nucleus removed and replaced with the ‘mother’s’. Left behind in the cell were the mitochondria and as mitochondria are semi-autonomous self-replicating organelles within the cell they have their own DNA. This means, in short, that baby has DNA from three sources and a great deal of fuss is being made of this genetic hybrid.
The procedure is to cure diseases inherited from the mother’s mitochondria (sperm provide no mitochondria when they fertilise an egg) which are very nasty debilitating conditions so hopefully, this baby will thrive and live a long happy life. All of the earlier experiments with mice have given no reasons to sound the alarm and indeed the data indicate intriguingly that the chimera live longer, healthier lives than their conventional cousins1.
As mentioned in previous blogs 2, 3 not all mitochondria are created equal. Some, as found in birds and bats are particularly efficient, producing fewer free radicals and delivering high outputs suitable for the flying life. The payback seems to be longer lives (pigeons 20 yrs, parrot 80 yrs, Little Brown bat 30 years) when compared to similar sized mammals ( rats 3 years, mice 2 years): oh to have such mitochondria in my cells.
Maybe this is not so fanciful. We know that inter mammal mitochondrial populations can coexist from of all things panda breeding programs in China4 using rabbit and panda embro hybrids . Essentially, in summary, depending on circumstances the rabbit and panda mitochondria in embryos replicate competitively in their micro-ecosystem and one or the other eventually dominates. They don’t self-destruct or do anything radical, they just swim about doing what mitochondria do and presumably negotiate with the nucleus for the spare parts that it provides to keep them running.
It’s should be clear where this post is going. The labs with the expertise to create chimera in mice could have a go at creating a mouse with bat mitochondria. I know bats are not flying mice and that they branched into an order of their own 50 million years ago... but they are placental mammals and are no more distantly related to mice than the above mentioned rabbit and panda work. Mitochondria don’t seem to produce violent antigenic signalling on the surface of their host cells.
In any case, it is worth a shot, what if you could make a three parent mouse with bat mitochondria, what if it lived for five years instead of the normal two to three years? This would set fire to gerontology. Nobel prizes in 2022 anyone?
- Roberts, Michelle (2016-09-27). "First 'three person baby' born using new method".BBC News. Retrieved 2016-09-28.
4)Biol Reprod. 2002 Aug;67(2):637-42.Interspecies implantation and mitochondria fate of panda-rabbit cloned embryos.
Chen DY1, Wen DC, Zhang YP, Sun QY, Han ZM, Liu ZH, Shi P, Li JS, Xiangyu JG, Lian L, Kou ZH, Wu YQ, Chen YC, Wang PY, Zhang HM.
