Qld team on the pulse of migraine genetics

What causes those headaches that keep on thumping after you've exceeded your recommended daily allowance of garden-variety analgesics?

The 85 per cent of Australians who suffer occasional to frequent splitting headaches would love to know -- as would pharmaceutical companies seeking to parlay their pain into profits.

Dr Dale Nyholt, of the Queensland Institute for Medical Research, went trawling in the gene pool of some 12,000 non-identical twins for susceptibility genes for the 'thumper' headache-cum-migraine phenotype, and caught something interesting on chromosome 5, that had apparently eluded his peers.

Using 10 criteria defined by the International Headache Society, Nyholt's team generated an empirical clustering of symptoms defining a particular type of migraine characterised by pulsating headaches -- the type that thumps in synchrony with the heartbeat.

They detected a strong linkage signal from a locus on chromosome 5, defining a 10-centimorgan 'ballpark'. When he tightened his criteria, the locus accounted for about 35 per cent of pulsating migraines.

Nyholt said none of the several dozen genes in the region has obvious credentials as a migraine-susceptibility gene.

"That makes searching somewhat difficult, but it's also an advantage because we won't be searching the gene databases with preconceived notions about the type of gene involved," he said.

His team is planning to repeat the screening procedure for another cohort of patients with pulsating headaches.

The linkage signal from chromosome 5 is quite strong. Nyholt, who is nearing the end of a three-year NHMRC grant for migraine research, said that surprisingly, the screen did not highlight any of the three migraine-susceptibility loci previously identified by Griffith University molecular geneticist Prof Lyn Griffiths, on chromosomes 2, 19 and the X.

Nyholt said he has not yet determined whether the 35 per cent of migraine patients who appear to share the unidentified susceptibility gene form part of the majority of migraine sufferers who obtain no relief, or only temporary relief, from the revolutionary anti-migraine drug Sumatriptan, marketed by GlaxoSmithKline.

He said if his team can locate and characterise the gene, it should lead immediately to a diagnostic test, and in time, for a targeted treatment for migraine.