Genetic variants linked to start of Huntington's symptoms

A genome-wide study of over 4000 people with Huntington's disease has identified the location several new gene variants that influence the onset of disease symptoms.

Huntington's disease is caused by a single gene and is characterised by uncontrolled movements, cognitive decline and psychiatric symptoms. These symptoms usually develop in middle age, but the age of onset varies between individuals.

'By understanding the mechanisms by which nature influences the age of onset of this devastating condition, we have identified a target for potential treatments. If we can develop a way to interfere with these processes, then we could possibly delay or even prevent the onset of the disease,' said Professor Lesley Jones of Cardiff University, who led the UK arm of the multicentre study.

It has been known for more than 20 years that variations in the Huntington's disease gene itself influences the timing of symptoms, but this did not explain all of the variation. So the scientists analysed the entire genomes of over 4000 Huntington's disease patients from the United States and Europe to search for other genes responsible.

They identified two gene variants on chromosome 15 — one was associated with a 1.4-year delay in disease onset while the other accelerated disease onset by approximately six years. Another variant on chromosome 8 was also associated with an earlier disease onset.

'Figuring out the exact DNA sequence variations responsible and how they influence the disease process should provide us with a guide for developing drugs that we hope could have a much larger effect than the one to six years produced by the natural variations, possibly even preventing symptom onset altogether,' said Dr James Gusella, Director of Massachusetts General Hospital's Center for Human Genetic Research and corresponding author of the study, which was published in the journal Cell.

Professor Jones stressed that treatments based on this research may still be a decade or more away. 'Our findings may not be able to help those already affected by Huntington's disease, but this could prove to be a turning point in how we treat the disease in future generations,' she said.