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Search for ALS Gene Narrows

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"When we see a pattern, and our analysis indicates that the probability is over 1 in 1,000 that it's not just chance, we have a marker," she says. "We then look at the nearby areas [of the chromosome]. When we see the same variations in affected people in 10 markers in a row, that gets our attention." Eventually, with luck, they've found the gene.

But as in all genetic research, Hosler tells WebMD, knowing where the problem lies is just the beginning. Whether or not the findings lead to an effective therapy will ultimately depend on the nature of the genes in question, and what, precisely, has gone wrong with them.

As a sad example, Hosler points to her team's earlier discovery of a link between certain ALS cases and a mutation in a well-researched gene called SOD.

"We thought we could dive right in and do something about it," she says. Because SOD produces a protein that protects cells from damaging free radicals, "we thought that the problems in ALS were due to a loss of that protection, and that we could simply supplement the missing protein product."

But that was not the case.

The mutant proteins were "working just fine at what they were supposed to do," she says. "The problem was that they were doing something in addition to what they were supposed to be doing." And eliminating something extra, she tells WebMD, is much harder than adding in something that's missing.

On average, says Hosler, ALS victims die within five years of their diagnosis. "But some survive up to 30 years," she says, "and there is no way to know how fast a particular patient will progress."

What's more, this kind of variation occurs within families, indicating that much more is at work than any one genetic glitch. Based on mouse studies, she tells WebMD, where different breeds develop symptoms at varying rates, "we're pretty sure that there are outside factors involved." Whether those forces are environmental, genetic, or more likely a combination of both, remains to be seen.

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