Eugenia Brin was 48 when she first noticed that her left leg was dragging. It took two years for doctors finally to diagnose her with early onset Parkinson's disease, because she didn't have tremors or other easily identifiable symptoms. The diminutive Brin, trained as an applied mathematician in the Soviet Union and then working as a meteorological analyst at NASA's Goddard Space Flight Center in Maryland, knew there was no cure for the degenerative disorder of the central nervous system, which affects about one in every 250 people over 40 and more than one in 100 in people over 65. All she could do was work with her physicians to find the right combination of drugs and dosages to help relieve the symptoms--at least temporarily.
In 2008, she was tested through 23andMe, a start-up launched by Anne Wojcicki, who is married to Brin's eldest son, Sergey, a cofounder of Google. Among the variants the company's basic consumer package tests for is a mutation on the LRRK2 gene that can lead to Parkinson's, because, says Wojcicki, "our scientists recognized that LRRK2 was an important finding." While visiting California, Brin, known to friends and family as Genia, provided a DNA sample. "Our family was one of the first to be tested," she says. "We were trying it out." The result was completely unexpected: She had the mutation on not one but both LRRK2 genes. "When I got the results I thought 'that's why,'" she recalls. "There was some sense of relief to know there was a reason behind the illness."
Parknson's doesn't only strike Jews, but it does have a Jewish connection. Ashkenazi Jews such as Brin, says Susan Bressman, chair of the department of neurology at Beth Israel Medical Center in New York City and professor of neurology at Albert Einstein College of Medicine, do not develop Parkinson's at a higher rate than any other group, but they are more likely to carry the LRRK2 mutation, the most common of the six or so mutations that cause increased incidence of the disease. "Two to five percent of Parkinson's worldwide is due to LRRK2," she says. "If you look at Ashkenazi Jews, 15 percent of Parkinson's is due to LRRK2." She stresses that the mutation does not necessarily mean someone will develop Parkinson's; a variety of environmental factors are also thought to play a role. "All we can say for sure is that LRRK2 mutation as a cause is more prevalent in people who have Parkinson's," she says. "We don't know why 30 percent of LRRK2 mutation carriers get the disease." Nor does the absence of the mutation guarantee not developing the disease: The vast majority of the millions of people who suffer from Parkinson's worldwide do not have a known mutation.
Everyone has two copies of the LRRK2 gene, but it is unlikely that one, let alone both, will have the mutation, says Neil Risch, director of the Institute for Human Genetics at the University of California, San Francisco. "It's really rare, probably in the ballpark of one in 20,000 or 40,000." While the double copy doesn't make Brin's symptoms worse or affect her treatment plan, "the big downside is that it means both of her kids have a copy," Risch says. "Usually they'd have a 50-50 chance but if a parent has two mutations it is 100 percent." As a result, both Sergey, 38, and Brin's younger son Sam, 25, each have a single copy.
The Parkinson's Institute in Sunnyvale, CA, asked the Brins to donate skin cells to a lab at Stanford University. …