Researchers who 5 years ago successfully hunted down a gene for a common form of Alzheimer's disease (AD) announced at a press conference today that they have zeroed in on a second major Alzheimer's gene. Although the two genes appear to function independently, the researchers say, together they are probably responsible for well over 50% of cases of late-onset Alzheimer's, the form that afflicts the vast majority of the 4 million Americans with the disease. But other experts warn that they are having trouble confirming the findings, which are described in the 15 October Journal of the American Medical Association.
A team led by Margaret Pericak-Vance of Duke University, Jonathan Haines of Vanderbilt University in Nashville, Tennessee, and Allen Roses--a former Duke researcher now in charge of genetics research at the Glaxo Wellcome Company in Research Triangle Park, North Carolina--scanned the DNA of members of 16 large families with a high rate of Alzheimer's, looking at 280 genetic markers that might help identify candidate genes. After winnowing out the best candidates, the researchers extended the project to include 38 additional AD families. A statistical analysis pinpointed a small region at the midpoint of chromosome 12 as the probable location of the suspect gene.
"What we have identified is only a location," says Haines. "We need to follow up with additional work to find the gene." He says it is too early to predict any clinical applications for this discovery, which must be confirmed by other researchers.
Meanwhile, some of the group's rivals say they have been unable so far to confirm the finding. Rudolph Tanzi of Massachusetts General Hospital in Boston and Ellen Wijsman of the University of Washington, Seattle, both say that they have checked large databases and have found "no evidence" of an AD gene on chromosome 12. Wijsman says this makes the Duke announcement "interesting," but adds, "I'm not holding my breath" that it will be confirmed anytime soon.