Mitochondria have their own DNA, which is strictly inherited from the mother. Normal and mutant DNA co-exist in most disease-causing mtDNA mutations, and there is a threshold of mutant mtDNA which must be exceeded before clinical symptoms occur. The mtDNA mutation level inherited by the offspring of a female mutation carrier can vary greatly, and even in twin births, it is possible for one baby to receive considerably more of the mutant mtDNA molecules than the other.
"Being able to find the minimal level of mutant mtDNA below which the chances of passing on a disorder is low was therefore very important", said Dr. Hellebrekers. Currently, there are no effective treatments for mtDNA disorders. Although we cannot guarantee that a mutant mtDNA level of 18% or lower will result in the birth of an unaffected child, we think that the chances of having a healthy child are high enough to make using PGD in this instance morally acceptable.
"Our research enables us to give genetic counselling to women at risk with respect to their reproductive choices and to provide them, for the first time, with the opportunity to give birth to a healthy baby. The prevalence of mtDNA disorders is 1 in 5,000, which means that the families of about 146,000 patients in Europe can now have the option of having a healthy child. This is a choice that they do not currently have", she concluded.
|Contact: Mary Rice|
European Society of Human Genetics