A novel presenilin-1 mutation (Leu85Pro) in early-onset Alzheimer disease with spastic paraparesis

BACKGROUND: Early-onset familial Alzheimer disease is caused by mutations in the amyloid precursor protein (APP), presenilin-1 (PSEN1), or presenilin-2 (PSEN2) genes. Phenotypic diversity has been reported to be associated with various mutations in PSEN1. Various mutations of PSEN1 have been reported in cases of early-onset Alzheimer disease with spastic paraparesis. OBJECTIVE: To describe a novel mutation in the PSEN1 gene associated with early-onset Alzheimer disease with spastic paraparesis. PATIENT AND METHODS: The patient was a 27-year-old man who developed early-onset dementia with spastic paraparesis. We examined sequences of the PSEN1, PSEN2, and APP genes from the patient and his family. To detect a possible mutation effect on the production of amyloid-beta peptide (Abeta), transfected HEK293 cells were examined for Abeta42 and Abeta40 production. RESULTS: We found a novel mutation (Leu85Pro) in PSEN1. This mutation influenced the production of Abeta, resulting in a 2-fold elevation of Abeta42 production and of the Abeta42/40 ratio. CONCLUSION: To our knowledge, this is the first report of very early-onset Alzheimer disease with spastic paraparesis and with the visual variant form of the disease, which is associated with visuospatial cognitive disorder. The Leu85Pro mutation in PSEN1 was pathogenic.     

One novel presenilin-1 gene mutation in a Chinese pedigree of familial Alzheimer's disease

This study is to explore whether there is presenilin 1 (PS1) gene mutation in Chinese familial Alzheimer's disease (FAD). There has been no such systemic research before in China. Using polymerase chain reaction, single strand conformation polymorphism (PCR-SSCP), followed by denaturing high performance liquid chromatograph (DHPLC) and DNA sequencing, we analyzed a Chinese family with early onset AD. The patients in this family showed a novel missense mutation in exon 4 of the PS1 gene (G to T change in codon 97), altering valine to leucine acid substitution. Because the change occurred in conserved domains of this gene, and is not present in normal controls, this novel mutation is likely to be causative of Chinese FAD.     

家族性阿尔茨海默病的早老素-1基因突变三例报告

目的 探讨早老素-1基因突变在家族性阿尔茨海默病(FAD)发病机制中的作用。方法采用美国国立神经病、语言机能障碍和卒中研究所及阿尔茨海默病和相关疾病协会(NINCDSADRDA)AD诊断标准对AD家系的三代人共23名进行筛查和诊断，并应用聚合酶链反应-单链构象多态性(PCR-SSCP)、变性高效液相(DHPLC)和DNA序列分析技术对该家系以及对照组的早老素-1(PS-1)基因第4、5号外显子进行检测。结果 家系23名中有3例被确诊为FAD。研究发现这3例FAD患者的PCR-SSCP泳动发生异常，又经DHPLC检测有双峰出现，提示有突变存在的可能。最后经DNA序列分析确认，PS-1基因第4号外显子的97号密码子发生了GTG→TTG错义突变(289位点发生G→T突变)，此密码子的氨基酸由缬氨酸变为亮氨酸(Val 97Leu)，第5号外显子未发现突变。家系内健康人及对照组的第4、5号外显子经以上检测也未发现突变。结论 该AD家系中的AD患者存在早老素-1第4号外显子的突变，此突变点与中国人FAD发病有关。     

Autopsy-confirmed familial early-onset Alzheimer disease caused by the l153V presenilin 1 mutation

BACKGROUND: Three affected individuals are described from a small English kindred with early-onset autosomal dominant familial Alzheimer disease (FAD) caused by a leucine-to-valine change at codon 153 (L153V) of the presenilin 1 (PSEN1) gene. METHODS: Clinical information on the pedigree was collected directly from family members and from hospital records. Samples of DNA were screened by means of direct sequencing of all coding exons of PSEN1. One patient underwent neuropathological examination. RESULTS: Mean age at onset of symptoms was 35.3 years (95% confidence interval [CI], 34.6-36.0 years); at death, 44.0 years (95% CI, 39.1-48.9 years). Mean duration of illness was 8.3 years (95% CI, 4.7-11.9 years). Myoclonus was a late feature in 1 patient; seizures were not reported in any subjects. Spastic paraparesis and extrapyramidal signs were absent. The neuropsychometric profile of 1 patient showed relatively preserved naming skills in the setting of global cognitive deficits. Results of neuropathological examination demonstrated the signature lesions of Alzheimer disease and the presence of occasional cortical Lewy bodies. CONCLUSIONS: The PSEN1 L153V mutation lies in the main mutation cluster of PSEN1 in the second transmembrane domain. It causes early-onset FAD with clinical features similar to those of other reported FAD pedigrees.     

Identification of new presenilin gene mutations in early-onset familial Alzheimer disease

BACKGROUND: Mutations in the presenilin 1 (PS1) and presenilin 2 (PS2) genes, and more rarely in beta-amyloid precursor protein (betaAPP), underlie the pathogenesis of most cases of familial Alzheimer disease (FAD). OBJECTIVE: To screen the entire coding region of the PS1 and PS2 genes and exons 16 and 17 of the betaAPP to find pathogenetic mutations in FAD.Patients Patients with FAD were consecutively enrolled from among the outpatients from the neurology departments at the Universities of Florence and Parma and the Santa Maria Nuova Hospital in Reggio Emilia, Italy. DESIGN AND METHODS: Polymerase chain reaction-single-strand conformation polymorphism and DNA se-quencing were used to investigate the affected members of families with FAD. RESULTS: We identified a family carrying a novel Ser130Leu mutation in the PS2 gene. Moreover, we found 2 novel PS1 mutations: Cys92Ser in exon 4 in 2 unrelated families and Leu174Met in exon 6 in the PS1 gene. We also found a fourth Italian family with the betaAPP Val717Ile mutation. CONCLUSIONS: One novel PS2 mutation associated with highly penetrant but variable age at onset (35-85 years) and 2 novel PS1 missense mutations associated with early-onset Alzheimer disease at age 49 to 54 years have been identified in Italian families. Screening for new mutations in presenilin and betaAPP genes was beneficial in characterizing gene function in FAD.     

散发性阿尔茨海默病早老素-1基因第5号和第8号外显子突变研究

目的　探讨散发性阿尔茨海默病 (SAD)与早老素 1(PS 1)基因突变的关系。方法　采用多聚酶链反应 单链构象多态性 (PCR SSCP)分析技术对 6 8例SAD患者的PS 1基因第 5号和第 8号外显子进行突变检测。结果　所有病例PS 1基因第 5号和第 8号外显子的PCR SSCP分析结果均显示两条单链和一条双链 ,未发现异常泳动 ,推断没有存在突变。结论　SAD和家族性AD(FAD)的致病原因存在差异 ,在SAD中PS 1基因第 5号和第 8号外显子不存在突变或突变率极低 ,并非SAD致病的重要因素     

Alzheimer病患者淀粉样前体蛋白基因16、17外显子突变的研究

目的 探讨淀粉样β-蛋白(β/A_4)基因突变与Alzheimer病(AD)的关系。方法 运用限制性片段长度多态性(RFLP)和单链构象多态性(SSCP),检测分析20例散发性AD患者和8例正常老年人的淀粉样前体蛋白(APP)基因16、17外显子的多态性。结果 AD患者和正常对照的β/A_4基因均未发现C→T突变及其它异常SSCP泳动变位。结论 APP基因β/A_4编码区突变不是一突变“热点”,在AD不具有普遍意义。     

散发性Alzheimer病早老素-1基因第8号和第10号外显子突变研究

目的 :探讨散发性 Alzheimer病 (SAD)与早老素 - 1(PS- 1)基因突变的关系。方法 :采用聚酶链反应 -单链构象多态性 (PCR- SSCP)分析技术对 6 8例 SAD患者的 PS- 1基因第 8号和第 10号外显子进行突变检测。结果 :所有病例 PS- 1基因第 8号外显子的 PCR- SSCP分析结果均两条单链和一条双链 ,第 10号外显子的 PCR- SSCP分析结果均显示三条单链和一条双链 ,未发现异常泳动 ,推断没有存在突变。结论 :SAD的致病原因与 FAD不同 ,PS- 1基因第 8号和第 10号外显子突变并非 SAD致病的重要原因     

痴呆患者早老素-1基因第6号外显子突变研究

目的探讨痴呆患者早老素-1基因第6号外显子的突变特点。方法应用聚合酶链反应一单链构象多态性(PCR-SSCP)和DNA测序技术检测53例SAD患者、60例VD患者及90名健康老年人早老素-1基因第6号外显子。结果DNA测序在SSCP泳动异常标本中发现1123位点和1300位点发生错义突变，其中，SAD组2例在1123位点发生突变、2例在1300位点突变，VD组1例在1123位点发生突变；1123位点发生C→G突变(cys23Trp)，1300位点发生A→C突变(Asp 200Ala)。结论SAD患者存在早老素-1基因第6号外显子突变，本实验结果显示的2个突变位点均处在早老素蛋白的重要功能区，考虑此突变为病理性突变。     

Very early-onset familial Alzheimer's disease: a novel presenilin 1 mutation

BACKGROUND: Early-onset familial Alzheimer's disease (EOFAD) is linked to mutations in three autosomal dominant genes: PS1, PS2 and APP. The clinical presentation and age of onset of mutations is variable. OBJECTIVES: The aim of this report is to describe a novel PS1 mutation believed to be causal for a very early onset of AD. METHODS: This is a case history using information from medical records, relative interviews and genetic testing results to describe the pre-clinical prodrome and clinical course of a patient with EOFAD. RESULTS: A previously undescribed G206V mutation in PS1 was found in the proband. CONCLUSION: The G206V mutation in PS1 is probably causal of a case of EOFAD with significant premorbid features.     

Association between presenilin-1 Glu318Gly mutation and familial Alzheimer's disease in the Australian population

Mutations in the presenilin-1 (PS-1) gene on chromosome 14 account for the majority of early-onset familial Alzheimer's disease (FAD) cases. To date, more than 90 mutations have been identified and, while most of these mutations are completely penetrant, the Glu318Gly mutation has been suggested to be partially penetrant. These findings indicate that it may play a similar role to apolipoprotein E (APOE)-epsilon4 by acting as a genetic risk factor for AD. In the current study, a total of 682 subjects were tested to assess the frequency of the Glu318Gly mutation in AD in the Australian population. The Glu318Gly mutation was identified in six sporadic late-onset AD patients, four FAD patients (unrelated) and in nine control subjects. The frequency of this mutation was highest in the familial AD group (8.7%) and lowest in control subjects (2.2%). When the mutation frequencies were compared, we found a statistically significant difference between the latter two groups (Fisher's exact test, P < 0.05). The genotype frequency of the Glu318Gly mutation in all AD cases and controls in the Australian population was 2.8%. This frequency is comparable to that observed for the Dutch population (3.2%), but not for the Finnish population (6.8% and 6.0%) or the Spanish population (5.3%). These findings show that the frequency of the Glu318Gly mutation is increased in FAD patients, suggesting a potential role as a genetic risk factor contributing to the pathogenesis of familial AD.     

Microglia and neuritic plaques in familial Alzheimer's disease induced by a new mutation of presenilin-1 gene. An ultrastructural study

The results of the ultrastructural study of the brains of two sisters with familial Alzheimer's disease (AD) induced by a new mutation of presenilin-1 (PS-1) gene who died at the young age (35 and 37 years) are presented. In both cases, the changes typical of AD with particularly large number of neuritic plaques (NPs) were found. Microglial cells were located between amyloid core and neurites. At the ultrastructural level, the content of microglial cytoplasm was differentiated (amyloid fibrils or/and phagocytic bodies). This may suggest that microglial cells participate in forming of amyloid fibrils and/or phagocytosis of amyloid.     

Novel PS1 mutation in a Bavarian kindred with familial Alzheimer disease

We describe a novel Leu174Arg PS1 mutation in two members of a Bavarian family which were initially diagnosed with frontotemporal dementia. Intriguingly, there is the possibility that there is an 18th century founder effect and that this family is related to original kindreds with familial Alzheimer disease described in the early 20th century.     

Mutation negative "early-onset familial Alzheimer disease": consider screening for tau gene mutations

Mutations in 3 genes are known to be deterministic for early-onset familial Alzheimer disease. The genes are presenilin-1, presenilin-2, and amyloid precursor protein. As these genes prove to be negative in patients with a clinical diagnosis of early-onset familial Alzheimer disease, a search for tau gene mutations may be appropriate, as illustrated by the following case.     

The presenilin-1 familial Alzheimer disease mutant P117L impairs neurogenesis in the hippocampus of adult mice

The functions of presenilin 1 (PS1) and how PS1 mutations cause familial Alzheimer's disease (FAD) are incompletely understood. PS1 expression is essential for neurogenesis during embryonic development and may also influence neurogenesis in adult brain. We examined how increasing PS1 expression or expressing an FAD mutant would affect neurogenesis in the adult hippocampus. A neuron-specific enolase (NSE) promoter was used to drive neuronal overexpression of either wild-type human PS1 or the FAD mutant P117L in transgenic mice, and the animals were studied under standard-housing conditions or after environmental enrichment. As judged by bromodeoxyuridine (BrdU) labeling, neural progenitor proliferation rate was mostly unaffected by increasing expression of either wild-type or FAD mutant PS1. However, in both housing conditions, the FAD mutant impaired the survival of BrdU-labeled neural progenitor cells leading to fewer new beta-III-tubulin-immunoreactive neurons being generated in FAD mutant animals during the 4-week postlabeling period. The effect was FAD mutant specific in that neural progenitor survival and differentiation in mice overexpressing wild-type human PS1 were similar to nontransgenic controls. Two additional lines of PS1 wild-type and FAD mutant transgenic mice showed similar changes indicating that the effects were not integration site-dependent. These studies demonstrate that a PS1 FAD mutant impairs new neuron production in adult hippocampus by decreasing neural progenitor survival. They also identify a new mechanism whereby PS1 FAD mutants may impair normal neuronal function and may have implications for the physiological functioning of the hippocampus in FAD.     

家族性Alzheimer病淀粉样蛋白前体基因第16、17外显子的突变分析

目的:了解中国家族性Alzheimer病(familial Alzheimer disease,FAD)患者中21号染色体上淀粉样蛋白前体(amyloid precursor protein,APP)基因第16、17外显子的突变情况。方法:应用限制性片段长度多态性(restrictionfragment length polymorphism,RFLP)、聚合酶链反应-单链构象多态性(polymerase chain reaction-single strand con-formation polymorphsim,PCR-SSCP)及DNA直接测序技术,对两个FAD家系以及20例正常对照组进行了APP基因第16、17外显子检测。结果:全部家系成员及正常对照组经RFLP分析均存在EcoR Ⅰ酶切位点、BclⅠ消化后无Bcl Ⅰ多态性。经PCR-SSCP分析均未见异常泳动带。两个家系的全部成员及正常对照组经DNA序列分析也未见APP基因的缺失、插入和置换。结论:本研究中的两个家系中未发现APP基因第16、17外显子的突变,证实了APP基因突变所引起的FAD并不多见。