In a discovery that researchers hope will lead to the development of new treatments for Alzheimer's disease, scientists have found the third -- and what they believe to be the last -- defective gene that causes an inherited form of the disabling neurological illness.
The new gene, reported in today's edition of the journal Science, is particularly important, scientists believe, because it is surprisingly similar to another Alzheimer's gene identified only six weeks ago.
The discovery of two nearly identical genes that cause the same disease is virtually unprecedented, scientists said, and strongly suggests that they play a crucial role in the onset of the disorder.
"It is extremely important that the new gene" is similar to a FTC previously discovered gene, and that the proteins they produce are also similar, said neuroscientist Dennis Selkoe of Harvard Medical School. The existence of two distinct but very similar genes that cause the disease suggests that the genes, or others like them, play a crucial role in other forms of the disease as well, he said.
Inherited Alzheimer's, which strikes victims in their 40s -- 10 to 20 years earlier than noninherited Alzheimer's -- accounts for as much as 10 percent of the 4 million cases of Alzheimer's among Americans.
The research team, headquartered at the University of Washington, also believes that it is the final gene in the puzzle that is responsible for inherited Alzheimer's, and that its discovery will allow them to assemble the pieces into a coherent picture of the disorder.
"This is an incredibly important discovery," said neurologist Marcelle Morrison-Bogorad of the University of Texas, Southwestern Medical School in Dallas, a member of the Alzheimer's Association's Medical and Scientific Advisory Board. "This means that genetics has pretty much solved the mystery of early-onset Alzheimer's disease."
Researchers are now working to figure out the exact function of the two proteins produced by the two genes and how that function is altered by mutations. And if they do, experts believe that they can quickly find drugs that will prevent the progression of Alzheimer's.
