3 parent human embryos created in the UK

Why would scientists want to engineer an embryo with the genetic material from 3 people?  To "prevent" the inheritance of mitochondrial disease.  Not all of our DNA that we inherit is in the nuclei of the egg and sperm that join at conception.  In the cytoplasm of our mother's egg are mitochondria.  Mitochondria have their own DNA called mtDNA.  We inherit our mtDNA only from our mother because sperm's mitochondria are dumped at conception.  There are genetic mutations that cause disease in mtDNA and a woman with a such a mutation cannot help but pass this mutation on to her children.

This is where the three parent embryos come in.  Here is how it works.  Scientists took the nucleus out of an embryo had a mutation in its mtDNA and put it into an embryo whose mtDNA was normal, after removing the nucleus of that embryo of course.  The result is one embryo with the nuclear DNA from its mother and father and the mtDNA from another embryo and its mother.  Confused?  Here is a simplified diagram that I made from the one in the Nature paper.  (A zygote is the single celled embryo that results from conception.)

To make this work scientists destroyed one human embryo by removing its nuclear DNA and added the DNA from another human embryo to make a third recombinant embryo.  And they did it 80 times creating 80 embryos with 3 genetic parents. 

But to hear the media talk about it, this is no more than simple tinkering to prevent disease.  From the BBC:

Embryos containing DNA from a man and two women have been created by scientists at Newcastle University.  They say their research, published in the journal Nature, has the potential to help mothers with rare genetic disorders have healthy children.

The aim is to prevent damaged DNA in mitochondria - the "batteries" which power the cell - from being passed on by the mother.

IVF clinics are not currently permitted to carry out the procedure.

Around one in 200 children is born each year with mutations in the mitochondrial DNA.  In most cases this causes only mild disease, sometimes without symptoms.   But around one in 6,500 children is born with mitochondrial disease, which can cause serious and often fatal conditions, including muscular weakness, blindness and heart failure.

The scientists have developed a technique which would potentially allow them to replace defective mitochondria during IVF.  The research, funded by the Muscular Dystrophy Campaign, Medical Research Council and the Wellcome Trust, used newly fertilised eggs left over from IVF treatment.

The nuclei from the father's sperm and the mother's egg, which contain the parents' DNA, were removed, leaving behind the faulty mitochondria.  The nuclei were put into another egg from which the nucleus had been removed, but which retained its mitochondria.  This new embryo contained the genes from both parents plus a tiny amount of mitochondrial DNA from the donor egg.

"What we've done is like changing the battery on a laptop," said lead author Professor Doug Turnbull.  "The energy supply now works properly, but none of the information on the hard drive has been changed.

"A child born using this method would have correctly functioning mitochondria, but in every other respect would get all their genetic information from their father and mother."

There are some very important points to make here.  First and foremost, these scientists ARE NOT manipulating EGGS.  They are manipulating EMBRYOS which are whole members of the human species. This is human experimentation straight up that is being likened to "changing the battery in a laptop."  I ask WHERE IS THE OUTRAGE?

Second, this does not prevent the inheritance of mitochondrial disease.  The embryos created have inherited the defective mitochondria.  Their DNA is implanted in a different embryo that has normal mitochondria.  So this technique doesn't cure mitochondrial disease.  Much like PGD, it doesn't fix the disease, it simply makes sure no embryo with defective mitochondria are born.

Third, there is a ban in the UK on implanting engineered embryos.  To use this technique to produce children in Britain, authorities would have to repeal the ban on implanting engineered embryos.  You know those animal-human hybrid embryos created by cloning with cow and rabbit eggs that they promised would never, ever see the darkness of a womb. 

Needless to say even though the intention of this technique is to produce a disease free child, the Catholic Church would find it morally wrong for many reasons.  First, this technique requires the embryos to be made in a lab through in vitro fertilization instead of in a womb.  Second, this technique essentially destroys two embryos creating a third that is a genetic hybrid.  And finally, it is a genetic manipulation that would continue to be inherited generation after generation.

Hat Tip to David Prentice at the Family Research Council Blog who has some great analysis.