Genetically Modified…..Babies?
February 6, 2008 by Kristina Chew, PhD
Filed under Health
A team of researchers from Newcastle University has created an embryo from three separate parents by using DNA from one man and two women. The researchers hope that, by using this technique, women with diseases of the mitocondria (”mini organelles that are found within individual cells”) do not pass on diseases such as fatal liver failure, stroke-like episodes, blindness, muscular dystrophy, diabetes and deafness to their children. Reports the BBC:
The Newcastle team have effectively given the embryos a mitochondria transplant.
We believe we could develop this technique and offer treatment in the forseeable future that will give families some hope of avoiding passing these diseases to their children
They experimented on 10 severely abnormal embryos left over from traditional fertility treatment.
Within hours of their creation, the nucleus, containing DNA from the mother and father, was removed from the embryo, and implanted into a donor egg whose DNA had been largely removed.
The only genetic information remaining from the donor egg was the tiny bit that controls production of mitochondria – around 16,000 of the 3billion component parts that make up the human genome.
The embryos then began to develop normally, but were destroyed within six days.
But some wonder: Will this technique lead to the creation of genetically modified “frankenbabies“? Ronald Bailey in Reason describes the creation of a similar technique by an American research team in 2001; one of the children born from this procedure had autism (though how the child was diagnosed with this is not specified):
Back in 2001, an American reseach team did something similar when it injected cellular fluids containing mitochondria from one woman’s eggs into the fertilized eggs of another woman. At a conference in Britain, the lead researcher, Jacques Cohen, told me [Ronald Bailey] that 20 babies were born using this technique–19 of whom are healthy and one of whom has an autism disorder. The FDA ordered the fertility to clinic to stop using the procedure.
For myself, I just have to say, if I had to do it all over again, I would choose Charlie, just as he is.
This is chilling. It sounds like science fiction.
Pretty much all the mitochondria any of us have in our cells are descendents of the mitochondria in our mothers. Mitochondria are cellular organelles that probably at one time were free-living cells themselves. They have double membranes and their own DNA and ribosomes, and make their own proteins. This is all separate from nuclear DNA, which is what makes us who we are. When the sperm meets the egg, the egg sits ready not only with its own nuclear DNA but also all the mitochondria that will be passed onto the new conceptus. Thus, all our mitochondria come from mom.
So…from what I gather from the writeup, they didn’t snag a bit of DNA from one woman and splice it in with some DNA from another woman as much as they used an enucleated egg with intact, functional mitochondria and put the zygotic nucleus in it. That way, you get healthy mitochondria but a child whose nuclear DNA is from the parents. It is, as the article actually says, like a “mitochondria transplant,” except in this case, they brought the organism to the transplant, instead of the transplant to the organism.
Mitochondrial diseases can be global and devastating. In fact, they’re rather rare because so much of what is in the mitochondrial DNA sequence has to stay as-is that there is little room for mutation. We are all very much alike when it comes to our mitochondrial DNA. The places where mutations do happen aren’t coding regions, and these are the regions used in DNA analyses stretching back millennia because they accumulate mutations at a regular rate in these areas because of an absence of selection pressures. When people talk about “haplotypes,” they’re either talking about maternal inheritance via mitochondrial DNA or paternal inheritance via the Y chromosome.
Anyway, maybe I’m just being too practical, but it’s not much different from taking healthy mitchondria from an egg and replacing the bad mitochondria in another egg with it for the purposes of conceiving. It’s not really “Frankengenes.”
I find the BBC writeup to have a couple of pretty egregious errors, so take what you read there with a grain of salt. For example:
‘The technique is intended to help women with diseases of the mitochondria – mini organelles that are found within individual cells…”
–Mitochondria are not “mini-organelles”; they are organelles, period, and pretty major ones at that.
“They are sometimes described as ‘cellular power plants’ because they generate most of the cell’s energy.” Yikes. And in doing so, apparently violate a law of thermodynamics. What they really do is harvest energy in the chemical bonds of glucose and package it into ATP, the energy-carrying molecules of most cells.
Sounds like the BBC writer was reaching a bit too far with the metaphors—-”mini-organelles,” on closer inspection, is a repetitive phrase…..