ApoE -491A/T promoter polymorphism is not an independent risk factor, but associated with the epsilon4 allele in Hungarian Alzheimer's dementia population

Abstract

Apolipoprotein E gene (Apo(epsilon)) has three common alleles (epsilon2, epsilon3, and epsilon4), of which epsilon4 has been shown to be associated with an increased risk for Alzheimer's disease (AD). Possible additional genetic factors, like the -491A variant of ApoE promoter may modify the development of AD, independently of the ApoE allele status. The objective of this study was to investigate whether A/T allelic polymorphism at site-491 of the ApoE promoter is associated with AD in a Hungarian population. The genomic DNA isolated from peripheral blood lymphocytes of 52 late-onset AD and 53 control individuals was used as a template for the two examined polymorphisms and PCR assay was applied. The epsilon4 allele was significantly over-represented in the AD group (28%) as compared with the control population (7%). No significant differences have been found between the control and the AD populations regarding the occurrence of the promoter A allele frequencies (control: 77%, AD: 70%). However, the AA genotype was more frequent in the AD group (48%) than in the control (10%) when the presence of epsilon4 allele was also considered. It is unlikely therefore that the -491A variant of the ApoE promoter gene is an independent risk factor in the Hungarian AD population, but a linkage disequilibrium exists between the two examined mutations.