Spontaneous DNA errors may lead to dementia

Many cases of dementia could be caused by non-inherited, spontaneous DNA mutations early in prenatal life, a new study suggests.

Only one in 20 cases of dementia happens in patients with a family history of the condition. What causes the remaining majority of cases has been difficult to pin down. Research now suggests mutations arising during gestation could account for some of these cases. 

'These spelling errors arise in our DNA as cells divide, and could explain why so many people develop diseases such as dementia when the individual has no family history,' said Professor Patrick Chinnery from the Medical Research Council's Mitochondrial Biology Unit and the Department of Clinical Neurosciences at the University of Cambridge, and an author of the study.

The study, published in Nature Communications, investigated tissue from a total of 54 individuals, including 14 healthy controls, 20 with Alzheimer's disease and 20 with Lewy body dementia. The researchers investigated 102 genes known to be associated with neurodegenerative disease and found non-inherited DNA errors (somatic mutations) in 27 of the 54 tissue samples.

However, the study did not investigate whether spontaneous DNA errors are more common in individuals with neurodegenerative disease compared with healthy individuals. The results from the study cannot currently be used to aid diagnosis or treatment. However, they may inform further research into treatments targeting the mechanisms underlying neurodegenerative diseases. 

Dr David Reynolds, chief scientific officer at Alzheimer's Research UK who was not involved with the research, said the study was of high quality, but emphasised that it was not large enough to draw conclusions about whether somatic mutations directly contribute to development of neurodegenerative disease.

'This well-conducted research using state-of-the-art DNA sequencing technology allowed scientists to look closer than ever at the genetic differences between cells in the brain,' Dr Reynolds told Newsweek.

'Although the researchers found DNA errors in genes associated with neurodegenerative diseases, the study was not sufficiently large enough to reveal if or how these errors might directly contribute to the development of a disease like Alzheimer's.'