Two different groups of scientists have independently found what may be the genetic culprit associated with two neurologic disorders: amyotrophic lateral sclerosis (ALS), probably more familiar to you as Lou Gehrig's disease, and a common dementing illness called frontotemporal dementia (FTD). The teams are from the Mayo Clinic in Florida and the National Institute on Aging in Maryland. Both papers were published in the journal Neuron. (Both are available without charge at that site.)
The possibility of a genetic link between the two conditions was suggested by circumstantial evidence. The diseases share some features, and some people seem to suffer from features of both illnesses. Also, these diseases sometimes run in families, and some families seem to be afflicted with both ALS and FTD. A region of a particular chromosome got on the researchers' radar several years ago, and this week's publications from the two groups seemed to confirm that mutations in the gene C9ORF72 may be involved. While a certain pattern of repeats in this gene may occur occasionally in healthy people, hundreds or thousands of repeats were observed in people with ALS or FTD.
It's important to understand that this is an essential but small first step. The ScienceNow blog had a good post about these studies today, and they put some perspective on the road ahead. Here's an excerpt:
Still, many important questions remain. Neither team has found an explanation for why some people with C9ORF72 mutations get ALS whereas others get FTD. And it's not clear how the mutations would cause either disease. It may be that the protein encoded by C9ORF72 performs some yet-to-be-discovered essential function that gets disrupted, Traynor says. Or maybe the function of C9ORF72 doesn't matter. Another possibility, Traynor says, is that the repeated nucleotides cause a toxic buildup of messenger RNA, a key player in the cellular machinery for reading out DNA to make protein.
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