Scientists have shown for the first time how a particular family of diseases are passed down from mother to child and how this can lead to the severity of the disease differing widely. The research, funded by the Wellcome Trust, offers hope of being able to predict a child's risk of developing a mitochondrial disease which can cause muscle weakness, diabetes, strokes, heart failure and epilepsy.
All human and animal cells contain many mitochondria, which are involved in energy production within the body. Mitochondria have their own genetic information, known as mitochondrial DNA, or mtDNA, which is inherited. However, whereas a child inherits one copy of DNA from each parent, a child may inherit many copies of mtDNA, which are only passed down from the mother.
Mutations in mtDNA can affect energy production within cells and therefore lead to disease. However, mitochondrial diseases differ both in location and severity depending on where and at what levels the mutations are distributed. Defective mitochondria cause most damage in muscles, nerves and the brain, the parts of the body which consume the most energy.
"Inheritance of mitochondrial diseases within families has proved incredibly difficult to predict," says Professor Patrick Chinnery, a Wellcome Trust Senior Clinical Research Fellow at Newcastle University. "A mother can pass on a small proportion of mutant mtDNA, or a very high proportion, and this can make the difference between a child being born without disease and another having a very severe form of the disease."
A womans eggs are formed at a very early stage in her development. As a precursor cell divides into a number of eggs, so the mitochondria from that cell are distributed randomly throughout these eggs. Hence different eggs can contain very different amounts of mutant mtDNA, which determine the amount of mutant genetic material that is passed on to the next generation. This difference is thought to explain
|Contact: Craig Brierley|