No association between an intronic polymorphism in the presenilin-1 gene and Alzheimer's disease

Mutations in the presenilin-1 (PS-1) gene are believed to be responsible for the majority of familial early-onset Alzheimer's disease (AD). The finding of an intronic polymorphism in the PS-1 gene prompted an investigation into its relevance in AD. An association between homozygosity for the most common allele (allele 1) in this intronic polymorphism and late-onset AD has been shown and has been confirmed by others though some studies do not support these findings. We genotyped a large series of sporadic AD cases (n = 120) and age-matched controls (n = 108) for this intronic polymorphism. We then compared both the frequency of allele 1 and allele 1 homozygosity between the AD group as a whole and in early-onset (n = 26) and late-onset (n = 94) groups with age-matched control groups (n = 29 and n = 79, respectively). No increase in the frequency or homozygosity of allele 1 in either the AD group as a whole, or when divided into late- and early-onset cases was found. Increases in the frequency of allele 1 homozygotes and in the number of non-apolipoprotein E epsilon4 carrying allele 1 homozygotes/heterozygotes was demonstrated in the early-onset AD cases although these values did not reach significance. We conclude that there is no relationship between this intronic polymorphism in the PS-1 gene and AD in the homogenous population genotyped in this study.