Cutting edge

April 2, 1999

Advances in genetic research could mean a cure for Parkinson's disease soon.

Most of us will know someone with Parkinson's disease. It affects 2 per cent of people over 65 in the developed world.

PD is incurable and although we do have a battery of drugs to treat its symptoms, none can retard its relentless course. Many factors may be implicated in its causation, such as environmental chemicals, injury and, of course, our genes. I am looking at the role of genetics in PD to see whether certain genetic factors make some people more susceptible to developing the disease. It is hoped that by identifying the cause, new means of prevention and therapy can be devised.

It was initially thought that genetic factors had little to contribute to our understanding of the disease but this changed with the recent publication of a mutation (pathologically altered DNA) in the first gene, known as alpha synuclein, which was thought to cause PD in an Italian-American family. How the mutation of the gene causes the symptoms in this rare family is not yet known but it has given us an important handle on the kind of chemicals in the brain that may be involved.

I have been able to establish that the mutation in this gene is not the cause of most PD in Europe, but the search has now been extended to related proteins. It is still true that for the majority of people who develop PD later in life genetic factors are likely to be less important in its causation, although they may well give us a better understanding of what actually triggers the disease off, especially in younger patients and those with a family history of PD.

My work has taken me around Britain visiting patients with a family history of PD where there are at least two brothers and sisters alive with the disease, whom I have visited in their own homes. In some cases I have come across families who have been living with the disease where it has obviously been passed down from at least three generations.

Talking with them in their own environment, I have been able to begin to understand what living with a progressive disease is really like as well as becoming skilled in spotting all the subtle signs and symptoms. Understanding the mystery of their disease has been stimulating but nothing compared to the excitement of being part of a process that may mean that their future and that of their children could be wholly different from the suffering of the previous generations.

The last piece of the jigsaw, namely a detailed map of the human genome and the technology to exploit it, is largely in place. Markers (as on a map) have been developed that indicate areas throughout our DNA. Regions of genetic interest can be found by seeing if, in running these markers, affected individuals show excess sharing of certain pieces of DNA. This may then indicate the underlying presence of a mutation in a gene responsible for the condition.

The answer is going to be that although there are a number of families where a single gene probably has a major effect on the development of the disorder, there is a far greater number of affected patients who appear to have inherited a susceptibility to PD by virtue of a number of interactive genes. If, as I suspect, the relevant susceptibility genes can be found it will be much easier to identify the environmental triggers. I now feel that both prevention and cure for Parkinson's disease are realistic possibilities within my lifetime.

Jenny Vaughan, department of neurogenetics, Institute of Neurology, London.

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