Dementia gene identified

Two groups of scientists have identified a gene which, when faulty or missing, causes a common type of dementia. Teams based at the Mayo Clinic College of Medicine, US, and the University of Antwerp in Belgium report that mutations affecting the progranulin gene cause familial frontotemporal dementia (FTD). The gene makes a growth factor protein important in many different processes, which appears to be crucial to brain nerve cells. The discovery should help shed light on the underlying causes of dementia, say the researchers, whose findings were published early online in the journal Nature.

FTD usually affects people aged between 40-64 years old, and accounts for around 15 per cent of all dementia cases. As its name suggests, the condition affects the frontal and temporal lobes of the brain, causing socially inappropriate behaviour, personality changes and eventually loss of speech and motor skills. Although in many cases FTD is not inherited, an estimated 35-50 per cent of affected people have a family history of the condition. In 1998, the Mayo Clinic scientists, along with others, found that mutations affecting the gene for a protein called 'tau' cause some of these familial cases. Since then, the search has continued for the genetic trigger responsible for the others.

In the latest study, the researchers discovered that mutations the progranulin gene - located in the same section of chromosome 17 as the tau protein gene - appear to account for all the remaining cases of familial FTD that have been linked to this chromosome. The progranulin gene makes a growth factor protein involved in cell division and movement during many different body processes, including wound repair, embryonic development and inflammation. Although it is not yet known exactly what role progranulin plays in the brain, the scientists say that that lack of the protein eventually causes neurons to die.

'This new finding is an important advance in our understanding of frontotemporal dementia', said Richard Hodes, director of the US National Institute on Aging, which funded the research. The scientists hope that the discovery will lead to new treatments for FTD, as well as new genetic tests to offer affected families. In addition, they now want to investigate whether the gene is involved in other degenerative disorders, such as amyotrophic lateral sclerosis (ALS).