An additional genetic influence for Alzheimer's disease has been confirmed in families with a high incidence of the disorder, according to a study published in the August 19 issue of the Journal of the American Medical Association.

The study confirms the existence of an Alzheimer's disease susceptibility gene on chromosome 12. The findings also imply there's at least one other gene associated with a risk or susceptibility to late-onset Alzheimer's disease that has not yet been identified.

The 46 chromosomes normally present in every cell of the human body carry hereditary factors encoded in what's estimated to be between 75,000 to 100,000 unique genes. "Defining the gene associated with a family's susceptibility to Alzheimer's will eventually provide researchers with new and otherwise unattainable insight into how the disease occurs," says lead investigator Professor Peter St. George-Hyslop, director of the Centre for Research in Neurodegenerative Diseases at the University of Toronto."

"Although we don't yet know where the Alzheimer's susceptibility gene is precisely located on chromosome 12, there are a number of genes on this chromosome which might be associated with Alzheimer's disease," says St. George-Hyslop. "Our preliminary studies suggest that it is probably not either of two genes on chromosome 12 that have recently been implicated in Alzheimer's disease."

The researchers collected DNA samples from 53 families with two or more individuals affected by Alzheimer's disease. This involved 173 people with Alzheimer's disease and 146 nondemented relatives. Once the samples were checked and showed the Alzheimer's disease was not due to mutations in the known genes, the investigators then studied the samples for a series of DNA markers located on chromosome 12.

"We were able to show these markers were associated with Alzheimer's disease in a family," said co-principal investigat
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Contact: Christina Marshall
christina.marshall@utoronto.ca
(416) 978-5949
University of Toronto
19-Aug-1998