Mutation analysis of presenilin-1 gene in Alzheimer' s disease patients and the effects of its mutation on expression of presenilin-1 and amyloid precursor protein / 中华神经科杂志

ABSTRACT

Objective To analyze the resenilin-1 (PS-1) gene mutations in Alzheimer' s disease (AD) patients and investigate the influence of the initiation codon mutation on the mRNA expression of PS-1 and amyloid precursor protein (APP) genes and the expression of PS-1 proteins.Methods (1) All 111 AD patients were enrolled by the Department of Neurology,Second Affiliated Hospital,College of Medicine,Zhejiang University from July 2004 to June 2010.Mutations in the 13 exons and flanking regions of PS-1 gene were examined by direct sequencing.(2) cDNAs encoding full-length wild-type and mutant (c.1A ＞G) PS-1 were subcloned into enhanced green fluorescent protein.Levels of the mRNA expression of PS-1 and APP genes and PS-1 proteins expression in the transfected cells were detected by quantitative real-time PCR and Western blot,respectively.Results A new heterozygous initiation codon mutation changing from ATG to GTG in one individual was identified.Compared to the control groups,the mRNA expression of the mutant PS-1 gene in HEK293 and N2a was significantly lower than the normal PS-1 gene(116.8 ± 3.9 vs 49.5 ±3.3,t =13.27,P ＜0.01 ;69.0 ± 1.9 vs 29.5 ± 1.3,t =17.20,P ＜0.01) and the APP gene was not obviously altered.The proteins were detected by Western blot analysis in HEK293 cells but not in N2a cells.Conclusions Since we only identified one novel heterozygous initiation codon mutation (from ATG to GTG),mutations in PS-1 are likely to be rare in AD patients.Initiation codon mutation would reduce the expression of PS-1 proteins.Inactivation of some of the PS-1 proteins could be insufficient to lead to AD and could be more likelv to act as a risk factor.