First baby with DNA of 3 parents born to overcome faulty genes

28 Sep 2016

In vitro fertilisation in progress. Image: nevodka/Shutterstock

A ‘revolutionary’ new DNA splicing technique has resulted in the birth of the first child containing the DNA of three parents, in a procedure to control the passing on of harmful genetic conditions.

At no other point in time has science had such control over human DNA, with breakthroughs like the development of the CRISPR/Cas9 method, which allows a researcher to edit the DNA of embryos.

Now, a US team has achieved the feat of producing the first child born with the DNA of three parents, as part of a procedure to eliminate a harmful hereditary condition found in one of the parents.

Future Human

First two children died from condition

According to New Scientist, the baby’s mother carries the genes for a condition called Leigh syndrome, a fatal neurological disorder that gives the affected child a life span of only a year or two.

While the mother carries the faulty genes with no harm to herself, the genetic condition led to the death of her first two children.

From what researchers know of the disease, it resides in DNA in the parent’s mitochondria that carry only 37 genes.

In this mother’s case, over 25pc of her mitochondria were found to have the Leigh syndrome gene.

To overcome this, a team from the New Hope Fertility Center in New York, led by John Zhang, decided to use the three parent method.

Complications of faith

The most likely choice of method with this procedure would involve fertilising both a mother’s egg and donor egg with the father’s sperm.

Once both eggs are fertilised and progressing to early-stage embryos, the mitochondrial DNA in the healthy donor egg is transferred into the mother’s egg.

However in this instance, the Muslim parents were against the destruction of one embryo, and so opted for a method called spindle nuclear transfer. The resulting egg contained nuclear DNA from the mother and mitochondrial DNA from the donor that were then fertilised with the father’s sperm.

Five embryos were grown as part of the procedure but just one successfully developed, resulting in the birth of the child with DNA from three parents.

The procedure remains controversial however, with Zhang and his team having to travel to Mexico to perform it where “there are no rules”. They defended the decision to go ahead with the procedure, stating that “to save lives is the ethical thing to do”.

Tests on the child to see whether it carried genetic condition showed that only 1pc of its genes carry the mutation, putting it significantly below the threshold of 18pc typically associated with passing the condition on.

Update, 4.20pm, 29 September 2016: This article was amended to clarify that it is the donor mitochondrial DNA inserted into the mother’s egg, not the donor nucleus.

Colm Gorey was a senior journalist with Silicon Republic