Scientists have found evidence that a recessive gene may be involved in the development of Alzheimer's disease (AD). An Arab Community, Wadi Ara, in northern Israel, has been plagued by an unusually high prevalence of AD; of those aged 85 years and older, 61% had AD. The APOE 4 allele is known to increase the risk for AD in genetically diverse populations, so the researchers examined the frequency of this gene in the Wadi Ara population. DNA samples were collected randomly from participants and their APOE genotype was determined. The findings suggest that the APOE 4 allele is relatively uncommon in the Arabs in Wadi Ara and, in fact, they had the lowest frequency of APOE 4 ever recorded. Thus, the presence of this gene cannot explain the observed high prevalence of AD.
Considering the high rate of intermarriage among close relatives--it has been reported that 44% of all Arab marriages in Israel are consanguineous--the authors speculate that recessive genes for AD must exist and are responsible for the high AD prevalence in the region. Further, they suggest that this, and other similar populations, should be ideal for studying recessive genes for AD because of the large family size and the high rates of inbreeding. Currently, the researchers are continuing their search for the causative gene and for environmental factors that may contribute to the development of the disease.
Source
- Bowirrat A et al. Neurology 2000, 55:731.
