New gene uncovered for late-onset A...( h Washington Heights and the Dominican ...)

"The Dominican population is very concerned about the increased frequency of disease and was very helpful in forming the basis of this study. From a genetic perspective, Dominicans are a relatively homogenous population, and follow similar diet and living patterns," said Dr. Mayeux. "Because individuals within families stay in touch and remain close to one another even after migrating to the United States, we were able to identify families in this large population that were very similar genetically."

To confirm their preliminary findings, Drs. Mayeux and St. George-Hyslop, his collaborator of more than 25 years, reached out to other colleagues who tapped genetic records of people of from even more diverse ethnic backgrounds.

In total, the initial discovery group included 350 families (representing a total of 1,800 people, half of whom had Alzheimer's), from Columbia University Medical Center and the University of Toronto. The group was divided into two parts: one that was analyzed to help with the discovery of SORL1, and a second that was analyzed to confirm the role of the gene. To this collection, Dr. Farrer, from Boston University School of Medicine, added 500 African-American sibling pairs (representing a total of 1,000 people), where one sibling was diagnosed with Alzheimer's and the other was not. Farrer also enabled the researchers to reconfirm their findings in an examination of data from Israeli-Arabs, while Younkin's data from mostly white Alzheimer's patients provided by the Mayo Clinic also confirmed the findings. Interestingly, the same variant was found in both the Israeli-Arab and Caribbean-Hispanic groups, which indicates that generations ago these two groups may have been genetically or geographically linked.