Background: Two types of alleles exist within intron 3' and exon 8 in the presenilin 1 (PS1) gene at nucleotide 16: allele 1 (A at site 16) and allele 2 (C at site 16), and three genotypes (1/1, 1/2, and 2/2) are formed with a combination of these alleles. The present study aims to investigate the association between the intronic polymorphism of PS1 gene and the occurrence of sporadic Alzheimer's disease in a northern Chinese population.
Materials and methods: The genotype and allele frequencies of PS1 gene were compared for 90 sporadic Alzheimer's disease patients and 90 healthy controls. The intronic polymorphism of the PS1 gene was determined by the PCR-restriction fragment length polymorphism method.
Result: PS1 alleles (allele 1 [A at site 16] and allele 2 [C at site 16]) and genotypes (1/1, 1/2, and 2/2) were in Hardy-Weinberg equilibrium for both Alzheimer's disease and control subjects. The frequencies of PS1 intronic genotype 1/1 and allele 1 in the sporadic Alzheimer's disease group were significantly higher than those in the control group (P < 0.005). The genotype 2/2 was significantly lower among the patients with sporadic Alzheimer's disease compared with the controls. The onset of sporadic Alzheimer's disease was positively associated with PS1 intronic allele 1 (odds ratio = 2.14) and negatively associated with PS1 intronic allele 2 (odds ratio = 0.48).
Conclusions: A polymorphism of the PS1 gene is associated with sporadic Alzheimer's disease risk in a northern Chinese population. PS1 intronic allele 1 is a risk factor, and PS1 intronic allele 2 is a protective factor for sporadic Alzheimer's disease.