Touching Lives - March 2005
New test for mitochondrial DNA diseases
Most of a cell’s genetic material — the DNA — is located in the cell nucleus, but relatively recently it was discovered that these mitochondria also contain a small amount of DNA (mtDNA).
A maternal thing
Unlike DNA in the cell nucleus, which is inherited from both parents, mtDNA is inherited only from the mother. Mistakes in copying this mtDNA may be the cause of a number of rare disorders in children including liver failure, diabetes, and neurodegenerative disorders, which affect about 1 in 11,000 children under the age of 6 and often result in death in infancy.
Some women are known to be carriers of defective mtDNA, and may pass these devastating conditions onto their children. Women who already have a child with mtDNA disease may need to know the risk of recurrence, but this is difficult to estimate because each family is different.
Thanks to a grant of more than £33,000 from Action Medical Research, a team at the University of Oxford has been investigating whether a new technique to test a woman’s egg cells (oocytes) before conception can be used to predict the risk of her baby inheriting faulty mtDNA.
They have pioneered a new application of a technique which is routine in their in vitro fertilisation (IVF) unit.
During the three-year study the team analysed mtDNA from egg cells, taken before conception, from healthy mothers whose children had died in infancy from mtDNA diseases. The resulting information was used successfully to assess the risk of the mothers having another severely affected baby, so that they could be properly advised before becoming pregnant.
Project leader Professor Poulton says,”Oocyte sampling can be used to predict recurrence risk in severe maternally inherited mitochondrial DNA diseases, where there is a clear relationship between the load of mutant mtDNA and the severity of the disease.
“With the help of Action Medical Research ^we have applied an established technique in a new way to assist in the management of devastating mtDNA disorders.^ This is a real advance”.