E280A PS-1 mutation causes Alzheimer's disease but age of onset is not modified by ApoE alleles

A single base substitution of a glutamic acid to an alanine codon 280 was found in the presenilin-1 (PS-1) gene on chromosome 14 in affected individuals in each of seven Colombian early-onset Alzheimer's disease (AD) kindreds. The mutation segregated with disease in kindreds tested. In the largest kindred (C2), the maximum two-point lod score between the mutation and AD was Z = 8.14 at θ = 0. The presence of a single mutation and the common geographic origin, with all families from the state of Antioquia, suggest a founder effect in this population. This finding is supported by the observation of a rare haplotype inherited with AD in all kindreds. These kindreds form the largest collection of AD cases with the same PS-1 mutation and the same educational, environmental, and ethnic background in which to study the phenotypic effect of putative risk factors, such as the ϵ4 allele of apolipoprotein E (ApoE) or head trauma. Of the few AD cases having a history of head trauma, the age of onset was not lowered. No effect of ApoE genotype on the age of onset was detected. Previous investigations of the effect of ApoE genotype on the age of onset were confounded by small patient numbers, familial clustering of ApoE genotypes, and combining data from unrelated families with different mutations. Hum Mutat 10:186–195, 1997. © 1997 Wiley-Liss, Inc.     

Distinguishable effects of presenilin-1 and APP717 mutations on amyloid plaque deposition

Both APP and PS-1 are causal genes for early-onset familial Alzheimer's disease (AD) and their mutation effects on cerebral Abeta deposition in the senile plaques were examined in human brains of 29 familial AD (23 PS-1, 6 APP) cases and 14 sporadic AD cases in terms of Abeta40 and Abeta42. Abeta isoform data were evaluated using repeated measures analysis of variance which adjusted for within-subject measurement variation and confounding effects of individual APP and PS-1 mutations, age at onset, duration of illness and APOE genotype. We observed that mutations in both APP and PS-1 were associated with a significant increase of Abeta42 in plaques as been documented previously. In comparison to sporadic AD cases, both APP717 and PS-1 mutation cases had an increased density (measured as the number of plaques/mm(2)) and area (%) of Abeta42 plaques. However, we found an unexpected differential effect of PS-1 but not APP717 mutation cases. At least some of PS-1 but not APP717 mutation cases had the significant increase of density and area of Abeta40-plaques as compared to sporadic AD independently of APOE genotype. Our results suggest that PS-1 mutations affect cerebral accumulation of Abeta burden in a different fashion from APP717 mutations in their familial AD brains.     

阿尔茨海默病患者早老素-1基因与ApoE基因关联分析

目的：探讨早老素－１（ｐｒｅｓｅｎｉｌｉｎ－１,ＰＳ－１）基因第８外显子３’端内含子,Ａｐｏｌｉｐｏｐｒｏｔｅｉｎ Ｅ（ＡｐｏＥ）基因等位基因多态性相互作用在散发性阿尔茨海默病（ｓｐｏｒａｄｉｃ Ａｌｚｈｅｉｍｅｒ’ｓ ｄｉｓｅａｓｅ,ＳＡＤ）发病机理中的作用。方法：应用聚合酶链反应－限制性片段长度多态性方法检测了７５例ＳＡＤ患者和７３名正常老年人的ＰＳ－１基因第８外显子３’端内含子、ＡｐｏＥ基因等位基因多态性分布。结果：ＰＳ－１、ＡｐｏＥ基因多态性与ＳＡＤ发病有明显关联：ＳＡＤ发病与ＰＳ－１基因的等位基因２呈明显负关联,等位基因１呈明显正关联。ＳＡＤ发病与Ｅ２等位基因呈明显负关联,与Ｅ３、Ｅ４等位基因无关联。ＡｐｏＥ基因多态性和ＳＰ－１基因多态性相互作用对ＳＡＤ发病无明显影响。结论：ＰＳ－１基因的等位基因２和     

早衰蛋白-1基因内含子多态性与Alzheimer's病的关系

为探讨早衰蛋白－１（ＰＳ－１）基因多态性与Ａｌｚｈｅｉｍｅｒ’ｓ病（ＡＤ０的关系,用聚合酶链反应－限制性片段长度多态性（ＰＣＲ－ＲＦＬＰ）方法检测５１例散发性ＡＤ患者ＰＳ－１外显子８的３‘端内含子基因型,其中４０例晚发性ＡＤ患者,同时检测８７６例健康对照者ＰＳＤ－１基因型。结果发现散发性ＡＤ组１／１基因型和１等位基因频率分别为０．５１０和０．６９６,显著高于对照组的０．２９９和０．５２２;晚发性Ａ     

Missense mutations in the chromosome 14 familial Alzheimer's disease presenilin 1 gene

Mutations in the presenilin genes (PS-1 and PS-2) cause early onset autosomal dominant Alzheimer's disease (AD). Eight early-onset, autopsy-documented familial AD kindreds were screened for mutations in PS-1, and seven different mutations were identified. Three of these were new mutations (G209V, A426P, and E120D), two were previously reported mutations in new families, and three mutations were confirmed in previously published families. Two of these new mutations are found within predicted transmembrane domains (TMDs 4, 7, and 8). The A426P mutation is the most C-terminal PS-1 mutation identified to date. Hum Mutat 11:216–221, 1998. © 1998 Wiley-Liss, Inc.     

Alzheimer's disease associated with mutations in presenilin 2 is rare and variably penetrant

Missense mutations in the presenilin 2 (PS-2) gene on chromosome 1 were sought by direct nucleotide sequence analysis of the open reading frame of 60 pedigrees with familial Alzheimer's disease (FAD). In the majority of these pedigrees, PS-1 and beta-amyloid precursor protein (beta APP) gene mutations had been excluded. While no additional PS-2 pathogenic mutations were detected, four silent nucleotide substitutions and alternative splicing of nucleotides 1338-1340 (Glu325) were observed. Analysis of additional members of a pedigree known to segregate a Met239Val mutation in PS-2 revealed that the age of onset of symptoms is highly variable (range 45-88 years). This variability is not attributable to differences in ApoE genotypes. These results suggest (i) that, in contrast to mutations in PS-1, mutations in PS-2 are a relatively rare cause of FAD; (ii) that other genetic or environmental factor modify the AD phenotype associated with PS-2 mutations; and (iii) that still other FAD susceptibility genes remain to be identified.      

A novel PSEN1 gene mutation (L235R) associated with familial early-onset Alzheimer's disease

Mutations in the presenilin 1 (PSEN1) gene are the most frequent cause of familial Alzheimer's disease (AD), with at least 182 different mutations published to date. We report a 48-year-old woman (age at onset 47 years) who presented a progressive alteration of episodic memory, spatial disorientation, apathy, language disturbances and neglect of personal care. Her MMSE score was 20/30. The patient presented an unusually rapid deterioration and at 6 months follow-up her cognitive and functional status had worsened considerably (MMSE score of 11). Cranial MRI showed a bilateral atrophy with temporal and parietal predominance and the quantification of AD CSF biomarkers showed the typical AD signature. Family history evidenced an autosomal dominant pattern of inheritance. Mutational screening was performed by direct sequencing of exons 3-12 of PSEN1. The patient presented the 3/3 APOE genotype. Genetic analysis revealed a nucleotide substitution in exon 7 of PSEN1 gene, producing a missense mutation in codon 235 from leucine amino acid to arginine (L235R). This amino acid is conserved between presenilin-1 and presenilin-2 proteins. The L235R mutation had not been previously reported, although other mutations in the same residue have also been associated with familial early-onset AD, providing support for the importance of this residue for the presenilin-1 function.     

A mutation screening by DHPLC of PSEN1 and APP genes reveals no significant variation associated with the sporadic late-onset form of Alzheimer's disease

Alzheimer's disease (AD), the most common cause of dementia in the elderly, is usually divided into familial and sporadic forms, according to family history. The familial form has often been reportedly caused by mutations in amyloid precursor protein (APP), presenilin-1 (PSEN1), or presenilin-2 (PSEN2) genes, whereas the genetic component for the sporadic form is less clear. We carried out mutation screening in exons 16 and 17 of APP, and in exons 3, 4, 5, 6, 7, 10 of PSEN1 genes in patients with the sporadic late-onset form of AD (LOAD). The aim of this study was to ascertain whether any variation in these genes, besides that of the well-known apolipoprotein E common polymorphism, could be involved in the onset of the disease. To search for the single nucleotide substitutions, we examined 172 LOAD patients by the denaturing high-performance liquid chromatography (DHPLC) technique. Only one same-sense mutation in exon 4 of PSEN1 gene (N32) was observed in this patient group. We concluded that the variation in the screened exons of the APP and PSEN1 genes, reportedly associated with familial AD, is not present in LOAD.     

Systematic genetic study of Alzheimer disease in Latin America: mutation frequencies of the amyloid beta precursor protein and presenilin genes in Colombia

Nearly all mutations in the presenilin 1 (PSEN1), presenilin 2 (PSEN2), and amyloid beta precursor protein (APP) genes lead to early-onset Alzheimer disease (EOAD, onset age at or before 65 years). In order to assess the genetic contribution of these genes in a series of Colombian AD cases, we performed a systematic mutation analysis in 11 autosomal dominant, 23 familial, and 42 sporadic AD patients (34% with age of onset < or = 65 years). No APP missense mutations were identified. In three autosomal dominant cases (27.2%), two different PSEN1 missense mutations were identified. Both PSEN1 mutations are missense mutations that occurred in early-onset autosomal AD cases: an I143T mutation in one case (onset age 30 years) and an E280A mutation in two other cases (onset ages 35 and 42 years). In addition, a novel PSEN1 V94M mutation was present in one early-onset AD case without known family history (onset age 53 years) and absent in 53 controls. The E318G polymorphism was present in five AD cases and absent in controls. In PSEN2, two different silent mutations were detected, including one not reported elsewhere (P129). The majority of the Colombian AD cases, predominantly late-onset, were negative for PSEN and APP mutations.     

Genetic aspects of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder with a complex etiology and pathogenesis. Mutations in presenilin 1 gene (PSEN1), located on chromosome 14, more rarely in amyloid-beta protein precursor (APP) on chromosome 21, and presenilin 2 genes (PSEN2) on chromosome 1, underlie the pathogenesis of most cases of familial early onset of AD (EOAD). The genetics of late-onset AD (LOAD) have been more enigmatic and the only confirmed risk factor for LOAD remains the apolipoprotein E4 allele (ApoE4) on chromosome 19. In this review, we discuss the genetics of AD with a focus on the role of the APP and presenilins.     

Novel presenilin-1 Y159F sequence variant associated with early-onset Alzheimer's disease

Background

Mutations in the gene for presenilin-1 cause familial, early-onset Alzheimer's disease.

Methods

We report the case of a 43-year-old woman presenting with progressive cognitive decline and a family history of early-onset dementia. Her workup included cerebrospinal fluid amyloid-beta, tau, and phospho-tau levels, as well as genetic sequencing of genes implicated in familial Alzheimer's disease.

Results

Cerebrospinal fluid biomarkers were consistent with a diagnosis of Alzheimer's disease. A novel nucleotide sequence variant (A476T) was discovered in one allele for presenilin-1, corresponding to a missense tyrosine-to-phenylalanine change at codon 159 (Y159F). An affected maternal uncle carried the same allele. The sequence variant occurs in a conserved region of the gene near other previously reported mutations.

Conclusions

This novel presenilin-1 sequence variant cosegregated with early onset dementia in the proband and at least one other affected family member, and likely represents a mutation causing familial, early-onset Alzheimer's disease.     

Novel APP K724M mutation causes Chinese early-onset familial Alzheimer's disease and increases amyloid-β42 to amyloid-β40 ratio

Alzheimer's disease (AD) is the most common neurodegenerative disorder among the elderly individuals. Although there are several million cases of AD estimated in China with the most population in the world, no Chinese early-onset familial AD caused by new APP gene mutation has ever been reported. Here, we first described a Chinese family with early-onset AD that was inherited in autosomal dominant manner, and the age of onset was 46.6 ± 7.7 years (n = 5; range, 40–58 years). By using genetic analysis of 3 collected patients' DNA samples, we identified a heterozygous APP gene mutation (g.275363A>T, K724M according to APP770). Finally, when APP695 with K724M mutation was ectopically expressed in HEK293 cell, the ratio of amyloid-β42 to amyloid-β40 was 2.23-fold higher than that of wild-type control. Together, our data suggest that APP K724M gene mutation may contribute to the cause of this Chinese early-onset familial AD.     

Presenilin 1 and alpha-1-antichymotrypsin polymorphisms in Down syndrome: no effect on the presence of dementia

As people with Down syndrome (DS) age, they are at greater risk for Alzheimer disease (AD) than the general population. It has been suggested that polymorphisms at the genes for presenilin-1 (PS-1) and alpha-1-antichymotrypsin (ACT) confer an increased risk for AD in the general population, and therefore potentially to AD in people with DS. We obtained DNA from 231 individuals with DS and 233 population controls. People with DS were evaluated for dementia. Allele frequencies at PS-1 and ACT polymorphisms in people with DS were compared to those in age-matched controls. There were no frequency differences between the control sample and DS sample for PS-1 or ACT alleles or genotypes. Similarly, there were no differences in allele frequencies between the demented and age-matched non-demented DS samples. However a higher frequency of PS-1 heterozygotes in the demented DS group was noted. We conclude that unlike the general population, neither PS-1 nor ACT polymorphisms appear to have a similar detrimental effect on dementia in DS. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 88:616-620, 1999.     

A transgenic rat model of Alzheimer's disease with extracellular Abeta deposition

Many transgenic mouse models of Alzheimer's disease (AD) that deposit amyloid (Abeta) have been produced, but development of an Abeta-depositing rat model has not been successful. Here, we describe a rat model with extracellular fibrillar Abeta deposition. Two lines of Sprague Dawley rats with transgenes expressing human amyloid precursor protein (APP) with the familial AD (FAD) mutations K670N/M671L and K670N/M671L/V717I were crossed. Abeta production in the double homozygous rats was sufficient for deposition by 17-18 months of age. The age of onset of Abeta deposition was reduced by crossing in a third rat line carrying a human presenilin-1 (PS-1) transgene with the FAD M146V mutation. The triple homozygous line had an onset of Abeta deposition by 7 months of age. Deposits appeared similar to those observed in the mouse models and displayed surrounding glial and phosphorylated tau reactivity. Abeta levels measured by ELISA were comparable to those reported in mouse models, suggesting that substantially greater amounts of soluble Abeta are not required in the rat to generate Abeta deposition.     

Genetic testing in familial and young-onset Alzheimer's disease: mutation spectrum in a Serbian cohort

Alzheimer's disease (AD) is the most common form of dementia. To date, more than 200 mutations in three genes have been identified as cause of early-onset autosomal dominant inherited AD. The aim of this study was to characterize the mutation spectrum and describe genotype-phenotype correlations in Serbian patients with positive family history of AD or/and early-onset AD. We performed a genetic screening for mutations in the coding regions of Presenilins 1 and 2 (PSEN1 and PSEN2), as well as exons 16 and 17 of the Amyloid Precursor Protein gene (APP) in a total of 47 patients from Serbia with a clinical diagnosis of familial and/or early-onset AD (mean age at onset of 60.3 years; range 32-77). We found one novel mutation in PSEN1, one novel variant in PSEN2, and three previously described variants, one in each of the analyzed genes. Interestingly, we identified one patient harboring two heterozygous mutations: one in APP (p.L723P) and one in PSEN1 (p.R108Q).     

Analysis of alpha-1 antichymotrypsin,presenilin-1, angiotensin-converting enzyme,and methylenetetrahydrofolate reductase loci as candidates for dementia

The genetic factors which predispose individuals to dementia in old age have not been fully defined. Although the apolipoprotein E4 allele accounts for a proportion of the genetic risk for late-onset Alzheimer disease (AD), it is neither necessary nor sufficient to cause this disease. Recent suggestions that other loci are involved in dementia risk have been supported by findings of associations of genotypes at the alpha-1 antichymotrypsin (ACT) and presenilin-1 (PS-1) loci with AD. We investigated these loci in two community-based aged Cambridgeshire populations: the rural Ely population (cohort 1) comprised 60 pairs of demented and nondemented elderly individuals, with a mean age of 84.2 years; and the Cambridge city population (cohort 2) comprised 81 pairs all over age 84, with a mean age of 87.3 years. Since vascular risk factors are likely to impact on dementia risk, we also examined the angiotensin-converting enzyme (ACE) and methylenetetrahydrofolate reductase (MTHFR) genes as candidates. ACE, ACT, PS-1, and MTHFR genotype and allele frequencies were not significantly different in cases and matched controls. These data support the doubts which have been raised about the involvement of the PS-1 and ACT polymorphisms in late-onset dementia. Am. J. Med. Genet. 74:207–212, 1997. © 1997 Wiley-Liss, Inc.     

Presenilin 1 and α-1-antichymotrypsin polymorphisms in down syndrome: No effect on the presence of dementia

As people with Down syndrome (DS) age, they are at greater risk for Alzheimer disease (AD) than the general population. It has been suggested that polymorphisms at the genes for presenilin-1 (PS-1) and α-1-antichymotrypsin (ACT) confer an increased risk for AD in the general population, and therefore potentially to AD in people with DS. We obtained DNA from 231 individuals with DS and 233 population controls. People with DS were evaluated for dementia. Allele frequencies at PS-1 and ACT polymorphisms in people with DS were compared to those in age-matched controls. There were no frequency differences between the control sample and DS sample for PS-1 or ACT alleles or genotypes. Similarly, there were no differences in allele frequencies between the demented and age-matched non-demented DS samples. However a higher frequency of PS-1 heterozygotes in the demented DS group was noted. We conclude that unlike the general population, neither PS-1 nor ACT polymorphisms appear to have a similar detrimental effect on dementia in DS. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 88:616–620, 1999. © 1999 Wiley-Liss, Inc.     

Identification of a novel mutation (Leu282Arg) of the human presenilin 1 gene in Alzheimer''s disease

Many different mutations, causative of Alzheimer's disease, have been found in the presenilin-1 gene (PS-1). We have developed a screening method based on denaturing gradient gel electrophoresis (DGGE), which allows the mutational analysis of the whole exon 9 of PS-1. Upon the screening of a Spanish sample of early onset familial Alzheimer disease cases, we have found a novel mutation in the PS-1 gene. The mutation (a T to G transition) results in a change of the amino acid at position 282 of the presenilin protein from leucine to arginine. This mutation is located in the hydrophobic domain number 7 (exon 9) close to the site of physiological cleavage processing. The average of onset of the affected members of this family is 43±5 years, and the average age of exitus of affected members is 56±3 years. The possibility to determine the specific pathologic mechanisms of this mutation is now open.     

FAD mutant PS-1 gene-targeted mice: increased A beta 42 and A beta deposition without APP overproduction

To investigate the consequences of mutant presenilin-1 (PS-1) expression under the control of the normal PS-1 gene, a gene-targeted mouse bearing the FAD mutation P264L was made. Gene-targeted models are distinct from transgenic models because the mutant gene is expressed at normal levels, in the absence of the wild-type protein. PS-1(P264L/P264L) mice had normal expression of PS-1 mRNA, but levels of the N- and C-terminal protein fragments of PS-1 were reduced while levels of the holoprotein were increased. When crossed into Tg(HuAPP695.K670N/M671L)2576 mice, the PS-1(P264L) mutation accelerated the onset of amyloid (Abeta) deposition in a gene-dosage dependent manner. Tg2576/PS-1(P264L/P264L) mice also had Abeta deposition that was widely distributed throughout the brain and spinal cord. APP(NLh/NLh)/PS-1(P264L/P264L) double gene-targeted mice had elevated levels of Abeta42, sufficient to cause Abeta deposition beginning at 6 months of age. Abeta deposition increased linearly over time in APP(NLh/NLh)/PS-1(P264L/P264L) mice, whereas the increase in Tg2576 mice was exponential. The APP(NLh/NLh)/PS-1(P264L/P264L) double gene-targeted mouse represents an animal model that exhibits Abeta deposition without overexpression of APP.     

Gene diagnosis of Alzheimer's disease and Parkinson's disease

Alzheimer's disease(AD) is the most common form of neurodegenerative diseases that causes intellectual dysfunction. AD is a genetically heterogenous disorder. Over 100 mutations have been identified in three causative genes, i.e. amyloid protein precursor(APP), presenilin 1(PS1) and presenilin 2(PS2) genes, for early-onset autosomal dominant familial AD(FAD). Apolipoprotein E(APOE) gene has been identified as susceptibility gene for late-onset FAD. The missense mutations in the causative genes lead to abnormal APP processing with overproduction of total A beta protein or A beta 42(43) isoform. The epsilon 4 allele of APOE gene is a genetic risk factor for sporadic AD as well as FAD. Parkinson's disease(PD) is another common form of neurodegenerative disease that causes movement dysfunction. Three genes, i.e. alpha-synuclein (SNCA), parkin(PARK2), and ubiquitin carboxy-terminal hydrolase L1(UCHL1) genes, have been identified as causative genes for familial PD. The B mutation of CYP2D6 gene(CYP2D6*4 allele) is a genetic risk factor for PD. Lewy body(LB), that is an intracellular inclusion body characteristic of PD, is widely distributed in the cerebral cortex of 20 to 30% of AD patients. This disease entity is called as Lewy body variant(LBV) of AD. LBV shares the genetic risk factor with AD and PD, i.e. APOE epsilon 4 allele and CYP2D6 B mutation. Gene diagnosis is possible for familial AD and PD. APOE and CYP2D6 genotyping is also applicable to the future prediction of AD and PD, respectively.