New technique will screen embryos for almost 6,000 inherited diseases

A powerful new method of testing embryos for inherited diseases, has been developed by fertility specialists in Britain.

The test will allow doctors to test for the first time a vast range of inherited diseases for which the specific genetic mutation is not known, such as Duchenne's muscular dystrophy (DMD) and some forms of cystic fibrosis.

The technique which is more accurate and efficient than current methods, will offer help to hundreds of couples who have a realistic chance of having healthy children and will enhance the number of diseases clinics can test for from about 200 to almost 6,000.

The technique is called preimplantation genetic haplotyping and was pioneered by Ali al-Hellani, a Saudi Arabian fertility specialist in 2004.

It has been developed further by Pamela Renwick at Guy's Hospital Genetics Centre and Professor Peter Braude of King's College London, who runs a fertility centre.

Using the new technique, doctors can examine every embryo created for a couple through IVF, and determine whether each is healthy and unaffected, a carrier of the disease, or destined to develop the full-blown medical condition.

The detailed knowledge of the genetic make-up of embryos will change the way couples at risk of passing on certain diseases are treated.

Professor Braude says it will change what they are able to do.

As some inherited conditions, known as x-linked diseases, are only passed on to boys, and because the mutations that cause the diseases are unknown, clinics can only screen them out by discarding every male embryo created, even if only half are affected.

The new test will allow doctors to see which male embryos are free of the disease-causing mutation, so fewer embryos will be wasted.

In some cases, the test will allow doctors the controversial option of asking couples to choose the sex of the embryos that are transplanted.

Apparently fertility specialists at Guy's hospital in London have already used the technique to "cherry pick" healthy embryos for seven women at risk of passing on inherited diseases and five are already pregnant and past the first trimester.

Two of the pregnant patients carry a rare cystic fibrosis gene, two carry the Duchenne muscular dystrophy gene, and one has had hydatidiform mole, a condition in which the placenta becomes cancerous.

By comparing DNA strands of affected and unaffected family members, the test allows for the the region of a chromosome that is responsible for the disease to be identified and doctors are then able to test embryos to see which have inherited that chromosome and which are disease-free.

The test has been licensed by the Human Fertilisation and Embryology Authority and costs £4,100.

Doctors will have a choice of implanting embryos they know to be male or female for non-medical reasons, though scientists emphasise that this will be rare.

But the test’s potential to eliminate inherited diseases from susceptible families and the prospect of weeding out embryos that would grow into healthy people is new ethical ground and is contentious.

The results are published in the journal Reproductive Biomedicine Online.

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