Genetic clues to ALS

US scientists hunting for possible causes of amyotrophic lateral sclerosis (ALS) have identified 34 possible genetic variations that may contribute to the disease. A team based at the Johns Hopkins School of Medicine in Baltimore pinpointed the regions after studying DNA from 276 patients and 271 unaffected people. The results, published in the journal Lancet Neurology, could shed light on the disease process and help develop new treatments.

ALS is a form of motor neurone disease that causes progressive, incurable paralysis. The symptoms are the result of gradual damage to motor neurones - nerve cells in the brain and spine that control movement. It affects around one in 20,000 people, including the UK astrophysicist Stephen Hawking. Around five per cent of cases are caused by alterations in a gene called SOD1, but most occur in people with no family history of the condition.

In the latest study, the scientists looked at more than half a million different single genetic variations, called  SNPs (single nucleotide polymorphisms), using a 'SNP chip'. They found evidence that 34 of the SNPs were linked to ALS. 'Although we haven't located the exact gene responsible for sporadic ALS, our results seriously narrow the search and bring us that much closer to finding what we need to start developing treatments for the disease', said team leader Bryan J Traynor.

Traynor highlighted the need for further research, since some of the associations may simply be statistical fluke. 'If you roll the dice 555,352 times, you are bound to get lucky by chance alone on some of those throws', he said, adding 'the next step is to go back and figure out which of those 'hits' are real and which are false'. A follow-up study is planned, which will look at samples from a similar number of patients and controls.