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.%目的 探讨阿尔茨海默病(AD)患者早老素-1(PS-1)基因突变情况及PS-1基因起始密码子ATG→GTG突变对PS-1和淀粉样前体蛋白(APP) mRNA水平及PS-1蛋白表达的影响.方法 (1)对2004年7月至2010年6月我院神经内科收治的111例AD患者行PS-1基因突变筛查；(2)将筛查发现的突变型PS-1 c.1A＞G和野生型PS-1基因全长cDNA克隆人增强型绿色荧光蛋白表达载体；以空质粒、野生型和突变型PS-1转染人胚肾(HEK) 293和小鼠成神经瘤(N2a)细胞,利用实时荧光定量PCR检测转染后细胞PS-1和APP mRNA水平及蛋白质印迹检测PS-1蛋白的表达,以研究PS-1基因突变后的功能改变原因.结果 (1)1例患者(编号M766)PS-1基因3号外显子起始密码子发生了杂合突变ATG→GTG；(2) PS-1基因mRNA水平在HEK293细胞和N2a细胞中野生型均明显高于突变型(116.8±3.9与49.5 ±3.3,t=13.27,P＜0.01;69.0±1.9与29.5±1.3,t=17.20,P＜0.01),APP基因mRNA水平突变型和野生型比较差异无统计学意义.蛋白质印迹结果显示野生型和突变型PS-1在HEK293细胞中均表达,且突变型表达量较野生型少,而N2a细胞仅表达野生型PS-1.结论 PS-1基因检测仅发现1个新的杂合突变ATG→GTG,AD患者PS-1基因突变频率很低；PS-1基因起始密码子突变导致PS-1蛋白表达减少,PS-1蛋白部分减少可能不是引起致病的独立因素,但可能是AD的一个危险因子.
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