RESUMEN
Hexanucleotide expansion mutations in the chromosome 9 open reading frame 72 (C9orf72) gene is the most common genetic cause for frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). SNP haplotype analyses have suggested that all C9orf72 expansion mutations originate from a common founder. However, not all C9orf72 expansion mutation carriers have the same haplotype. To investigate if the C9orf72 expansion mutation carriers in Sweden share a common founder, we have genotyped SNPs flanking the C9orf72 expansion mutation in cases with FTD, FTD-ALS or ALS to perform haplotype analysis. We have genotyped 57 SNPs in 232 cases of which 45 carried the C9orf72 expansion mutation. Two risk haplotypes consisting of 31 SNPs, spanning 131 kbp, were found to be significantly associated with the mutation. In summary, haplotype analysis on Swedish C9orf72 expansion mutation carriers indicates that the C9orf72 expansion mutation arose on at least two risk haplotypes.
Asunto(s)
Expansión de las Repeticiones de ADN/genética , Haplotipos/genética , Proteínas/genética , Adulto , Anciano , Anciano de 80 o más Años , Esclerosis Amiotrófica Lateral/genética , Proteína C9orf72 , Femenino , Demencia Frontotemporal/genética , Humanos , Masculino , Persona de Mediana Edad , Polimorfismo de Nucleótido Simple/genética , SueciaRESUMEN
OBJECTIVES: The aim of this study was to investigate cognitive performance including preclinical and clinical disease course in carriers and non-carriers of autosomal-dominant Alzheimer's disease (adAD) in relation to multiple predictors, that is, linear and non-linear estimates of years to expected clinical onset of disease, years of education and age. METHODS: Participants from five families with early-onset autosomal-dominant mutations (Swedish and Arctic APP, PSEN1 M146V, H163Y, and I143T) included 35 carriers (28 without dementia and 7 with) and 44 non-carriers. All participants underwent a comprehensive clinical evaluation, including neuropsychological assessment at the Memory Clinic, Karolinska University Hospital at Huddinge, Stockholm, Sweden. The time span of disease course covered four decades of the preclinical and clinical stages of dementia. Neuropsychological tests were used to assess premorbid and current global cognition, verbal and visuospatial functions, short-term and episodic memory, attention, and executive function. RESULTS: In carriers, the time-related curvilinear trajectory of cognitive function across disease stages was best fitted to a formulae with three predictors: years to expected clinical onset (linear and curvilinear components), and years of education. In non-carriers, the change was minimal and best predicted by two predictors: education and age. The trajectories for carriers and non-carriers began to diverge approximately 10 years before the expected clinical onset in episodic memory, executive function, and visuospatial function. CONCLUSIONS: The curvilinear trajectory of cognitive functions across disease stages was mimicked by three predictors in carriers. In episodic memory, executive and visuospatial functions, the point of diverging trajectories occurred approximately 10 years ahead of the clinical onset compared to non-carriers. (JINS, 2017, 23, 195-203).
Asunto(s)
Enfermedad de Alzheimer/complicaciones , Precursor de Proteína beta-Amiloide/genética , Disfunción Cognitiva/diagnóstico , Salud de la Familia , Mutación/genética , Presenilina-1/genética , Adulto , Anciano , Enfermedad de Alzheimer/genética , Disfunción Cognitiva/etiología , Disfunción Cognitiva/genética , Estudios Transversales , Progresión de la Enfermedad , Función Ejecutiva/fisiología , Femenino , Heterocigoto , Humanos , Masculino , Memoria Episódica , Persona de Mediana Edad , Valor Predictivo de las Pruebas , Suecia , Percepción Visual/genéticaRESUMEN
BACKGROUND/AIMS: We have previously reported the results of an extended genome-wide scan of Swedish Alzheimer disease (AD)-affected families; in this paper, we analyzed a subset of these families with autopsy-confirmed AD. METHODS: We report the fine-mapping, using both microsatellite markers and single-nucleotide polymorphisms (SNPs), in the observed maximum logarithm of the odds (LOD)-2 unit (LOD(max)-2) region under the identified linkage peak, linkage analysis of the fine-mapping data with additionally analyzed pedigrees, and association analysis of SNPs selected from candidate genes in the linked interval. The subset was made on the criterion of at least one autopsy-confirmed AD case per family, resulting in 24 families. RESULTS: Linkage analysis of a family subset having at least one autopsy-confirmed AD case showed a significant nonparametric single-point LOD score of 4.4 in 8q24. Fine-mapping under the linkage peak with 10 microsatellite markers yielded an increase in the multipoint (mpt) LOD score from 2.1 to 3.0. SNP genotyping was performed on 21 selected candidate transcripts of the LOD(max)-2 region. Both family-based association and linkage analysis were performed on extended material from 30 families, resulting in a suggestive linkage at peak marker rs6577853 (mpt LOD score = 2.4). CONCLUSION: The 8q24 region has been implicated to be involved in AD etiology.
Asunto(s)
Enfermedad de Alzheimer/epidemiología , Enfermedad de Alzheimer/genética , Cromosomas Humanos Par 8/genética , Adulto , Anciano , Anciano de 80 o más Años , Enfermedad de Alzheimer/patología , Autopsia , Encéfalo/patología , Mapeo Cromosómico , ADN/genética , Femenino , Ligamiento Genético , Estudio de Asociación del Genoma Completo , Genotipo , Humanos , Escala de Lod , Masculino , Repeticiones de Microsatélite , Persona de Mediana Edad , Polimorfismo de Nucleótido Simple , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Suecia/epidemiologíaRESUMEN
This study aimed at identifying novel susceptibility genes for a mixed phenotype of Alzheimer's disease and vascular dementia. Results from a genome scan showed strongest linkage to 20p13 in 18 families, and subsequent fine mapping was performed with both microsatellites and single-nucleotide polymorphisms in 18 selected candidate transcripts in an extended sample set of 30 families. The multipoint linkage peak was located at marker rs2144151 in the ANGPT4 gene, which is a strong candidate gene for vascular disease because of its involvement in angiogenesis. Although the significance of the linkage decreased, we find this result intriguing, considering that we included additional families, and thus the reduced linkage signal may be caused by genetic heterogeneity.
Asunto(s)
Enfermedad de Alzheimer/genética , Angiopoyetinas/genética , Mapeo Cromosómico , Cromosomas Humanos Par 20 , Demencia Vascular/genética , Salud de la Familia , Femenino , Humanos , Escala de Lod , Masculino , Repeticiones de Microsatélite , Fenotipo , Mapeo Físico de Cromosoma , Polimorfismo de Nucleótido SimpleRESUMEN
Frontotemporal dementia (FTD) is the second most common early-onset dementia. Up to half of the cases are familial, and several mutations have been identified as pathogenic. Repeat expansion mutations in C9orf72 are the most common genetic cause of FTD and are particularly frequent in Sweden and Finland. We aimed to determine the mutation frequency in patients with FTD ascertained at a memory clinic in Sweden and assess the inheritance pattern in the families. We screened 132 patients with FTD for mutations in C9orf72, GRN, and MAPT, and the frequency was 34.1%. Two novel variations, not previously published, were found; a pathogenic GRN mutation and a MAPT variation in intron 9 that we report as VUS. The likelihood of finding a mutation was highest in patients with a clear family history of dementia or motor neuron disease (76%), but mutations were also found in apparent sporadic cases. This confirms that FTD cohorts from Sweden have a relatively higher risk of an underlying mutation in all risk categories compared with other reported cohorts.
Asunto(s)
Proteína C9orf72/genética , Demencia Frontotemporal/genética , Mutación , Humanos , Porfiria Intermitente AgudaRESUMEN
Alzheimer's disease (AD) is a neurodegenerative disease that affects approximately 20 million persons all over the world. There are both sporadic and familial forms of AD. We have previously reported a genome-wide linkage analysis on 71 Swedish AD families using 365 genotyped microsatellite markers. In this study, we increased the number of individuals included in the original 71 analysed families besides adding 38 new families. These 109 families were genotyped for 1100 novel microsatellite markers. The present study reports on the linkage data generated from the non-overlapping genotypes from the first genome scan and the genotypes of the present scan, which results in a total of 1289 successfully genotyped markers at an average density of 2.85 cM on 468 individuals from 109 AD families. Non-parametric linkage analysis yielded a significant multipoint LOD score in chromosome 19q13, the region harbouring the major susceptibility gene APOE, both for the whole set of families (LOD=5.0) and the APOE varepsilon4-positive subgroup made up of 63 families (LOD=5.3). Other suggestive linkage peaks that were observed in the original genome scan of 71 Swedish AD families were not detected in this extended analysis, and the previously reported linkage signals in chromosomes 9, 10 and 12 were not replicated.
Asunto(s)
Enfermedad de Alzheimer/genética , Familia , Anciano , Enfermedad de Alzheimer/patología , Apolipoproteínas E/genética , Femenino , Ligamiento Genético , Marcadores Genéticos , Predisposición Genética a la Enfermedad , Genoma Humano , Humanos , Escala de Lod , Masculino , Repeticiones de Microsatélite , SueciaRESUMEN
BACKGROUND: The GGGGCC repeat expansion in the C9orf72 gene was recently identified as a major cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) in several European populations. The objective of this study was to determine the frequency of C9orf72 repeat expansions in a Bulgarian dementia cohort and to delineate the associated clinical features. METHODS AND FINDINGS: PCR-based assessments of the C9orf72 hexanucleotide repeat expansion in all study samples (including 82 FTD, 37 Alzheimer's disease (AD), and 16 other neurodegenerative/dementia disorder cases) were performed. We report the clinical, neuropsychological, and neuroimaging findings obtained for the C9orf72 repeat expansion carriers. Of the 135 cases screened, 3/82 (3.7%) of all FTD cases and 1/37 (2.7%) of all clinical AD cases had a C9orf72 repeat expansion. In this cohort, the C9orf72 pathological expansion was found in clinical diagnoses bridging the FTD, parkinsonism, ALS and AD spectrum. Interestingly, we showed early writing errors without aphasia in two subjects with C9orf72 expansions. CONCLUSIONS: This study represents the first genetic screening for C9orf72 repeat expansions in a Bulgarian dementia cohort. The C9orf72 repeat expansion does not appear to be a common cause of FTD and related disorders. This report confirms the notion that C9orf72 repeat expansions underlie a broad spectrum of neurodegenerative phenotypes. Relatively isolated agraphia in two cases with C9orf72 repeat expansions is a strong motivation to provide detailed and sophisticated oral and written language assessments that can be used to more precisely characterize early cognitive deficits in these heterogeneous conditions.
Asunto(s)
Proteína C9orf72/genética , Expansión de las Repeticiones de ADN/genética , Demencia/genética , Demencia/fisiopatología , Reacción en Cadena de la Polimerasa/métodos , Anciano , Bulgaria , Femenino , Humanos , Lenguaje , Masculino , Persona de Mediana Edad , Pruebas NeuropsicológicasRESUMEN
Alzheimer disease (AD) is a progressive neurodegenerative disorder and the most common form of dementia. The majority of AD cases are sporadic, while up to 5% are families with an early onset AD (EOAD). Mutations in one of the three genes: amyloid beta precursor protein (APP), presenilin 1 (PSEN1) or presenilin 2 (PSEN2) can be disease causing. However, most EOAD families do not carry mutations in any of these three genes, and candidate genes, such as the sortilin-related receptor 1 (SORL1), have been suggested to be potentially causative. To identify AD causative variants, we performed whole-exome sequencing on five individuals from a family with EOAD and a missense variant, p.Arg1303Cys (c.3907C > T) was identified in SORL1 which segregated with disease and was further characterized with immunohistochemistry on two post mortem autopsy cases from the same family. In a targeted re-sequencing effort on independent index patients from 35 EOAD-families, a second SORL1 variant, c.3050-2A > G, was found which segregated with the disease in 3 affected and was absent in one unaffected family member. The c.3050-2A > G variant is located two nucleotides upstream of exon 22 and was shown to cause exon 22 skipping, resulting in a deletion of amino acids Gly1017- Glu1074 of SORL1. Furthermore, a third SORL1 variant, c.5195G > C, recently identified in a Swedish case control cohort included in the European Early-Onset Dementia (EU EOD) consortium study, was detected in two affected siblings in a third family with familial EOAD. The finding of three SORL1-variants that segregate with disease in three separate families with EOAD supports the involvement of SORL1 in AD pathology. The cause of these rare monogenic forms of EOAD has proven difficult to find and the use of exome and genome sequencing may be a successful route to target them.
Asunto(s)
Enfermedad de Alzheimer/genética , Predisposición Genética a la Enfermedad , Variación Genética , Proteínas Relacionadas con Receptor de LDL/genética , Proteínas de Transporte de Membrana/genética , Anciano , Anciano de 80 o más Años , Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/patología , Precursor de Proteína beta-Amiloide/metabolismo , Encéfalo/metabolismo , Encéfalo/patología , Estudios de Casos y Controles , Estudios de Cohortes , Familia , Femenino , Humanos , Inmunohistoquímica , Masculino , Persona de Mediana Edad , Secuenciación del ExomaRESUMEN
BACKGROUND: Frontotemporal dementia is a highly heritable neurodegenerative disorder. In about a third of patients, the disease is caused by autosomal dominant genetic mutations usually in one of three genes: progranulin (GRN), microtubule-associated protein tau (MAPT), or chromosome 9 open reading frame 72 (C9orf72). Findings from studies of other genetic dementias have shown neuroimaging and cognitive changes before symptoms onset, and we aimed to identify whether such changes could be shown in frontotemporal dementia. METHODS: We recruited participants to this multicentre study who either were known carriers of a pathogenic mutation in GRN, MAPT, or C9orf72, or were at risk of carrying a mutation because a first-degree relative was a known symptomatic carrier. We calculated time to expected onset as the difference between age at assessment and mean age at onset within the family. Participants underwent a standardised clinical assessment and neuropsychological battery. We did MRI and generated cortical and subcortical volumes using a parcellation of the volumetric T1-weighted scan. We used linear mixed-effects models to examine whether the association of neuropsychology and imaging measures with time to expected onset of symptoms differed between mutation carriers and non-carriers. FINDINGS: Between Jan 30, 2012, and Sept 15, 2013, we recruited participants from 11 research sites in the UK, Italy, the Netherlands, Sweden, and Canada. We analysed data from 220 participants: 118 mutation carriers (40 symptomatic and 78 asymptomatic) and 102 non-carriers. For neuropsychology measures, we noted the earliest significant differences between mutation carriers and non-carriers 5 years before expected onset, when differences were significant for all measures except for tests of immediate recall and verbal fluency. We noted the largest Z score differences between carriers and non-carriers 5 years before expected onset in tests of naming (Boston Naming Test -0·7; SE 0·3) and executive function (Trail Making Test Part B, Digit Span backwards, and Digit Symbol Task, all -0·5, SE 0·2). For imaging measures, we noted differences earliest for the insula (at 10 years before expected symptom onset, mean volume as a percentage of total intracranial volume was 0·80% in mutation carriers and 0·84% in non-carriers; difference -0·04, SE 0·02) followed by the temporal lobe (at 10 years before expected symptom onset, mean volume as a percentage of total intracranial volume 8·1% in mutation carriers and 8·3% in non-carriers; difference -0·2, SE 0·1). INTERPRETATION: Structural imaging and cognitive changes can be identified 5-10 years before expected onset of symptoms in asymptomatic adults at risk of genetic frontotemporal dementia. These findings could help to define biomarkers that can stage presymptomatic disease and track disease progression, which will be important for future therapeutic trials. FUNDING: Centres of Excellence in Neurodegeneration.
Asunto(s)
Enfermedades Asintomáticas , Encéfalo/patología , Trastornos del Conocimiento/genética , Demencia Frontotemporal/genética , Mutación/genética , Pruebas Neuropsicológicas , Adulto , Trastornos del Conocimiento/diagnóstico , Trastornos del Conocimiento/psicología , Estudios Transversales , Femenino , Demencia Frontotemporal/diagnóstico , Demencia Frontotemporal/psicología , Humanos , Masculino , Persona de Mediana EdadRESUMEN
Amyloid beta-peptide (Abeta) deposition in brain is important in the development of Alzheimer's disease (AD). Neprilysin (NEP) appears to be the major Abeta degrading enzyme in vivo and reduced mRNA levels of NEP correlates with increased plaque density. We hypothesized that alterations in the NEP promoter region may alter NEP expression and thus be involved in the AD process. We investigated three putative important regions in the NEP promoter region; two dinucleotide-repeats (CA and GT) and a 480 base pair fragment. With fragment analysis and sequencing, 164 early-onset and 152 late-onset Swedish AD cases and 109 non-demented controls were investigated. No significant difference in the distribution of promoter polymorphisms between AD cases and controls were found in this study.
Asunto(s)
Enfermedad de Alzheimer/genética , Encéfalo/enzimología , Neprilisina/genética , Polimorfismo Genético , Polimorfismo de Nucleótido Simple , Regiones Promotoras Genéticas , Edad de Inicio , Anciano , Secuencia de Bases , Cartilla de ADN , Repeticiones de Dinucleótido , Humanos , Valores de Referencia , SueciaRESUMEN
Frontotemporal lobar degeneration (FTLD) is a progressive neurodegenerative disease with an age at onset generally below 65 years. Mutations in progranulin (GRN) have been reported to be able to cause FTLD through haploinsufficiency. We have sequenced GRN in 121 patients with FTLD and detected six different mutations in eight patients: p.Gly35Glufs*19, p.Asn118Phefs*4, p.Val200Glyfs*18, p.Tyr294*, p.Cys404* and p.Cys416Leufs*30. Serum was available for five of the mutations, where the serum-GRN levels were found to be >50% reduced compared with FTLD patients without GRN mutations. Moreover, the p.Cys416Leufs*30 mutation segregated in an affected family with different dementia diagnoses. The mutation frequency of GRN mutation was 6.6% in our FTLD cohort.
Asunto(s)
Degeneración Lobar Frontotemporal/sangre , Degeneración Lobar Frontotemporal/genética , Predisposición Genética a la Enfermedad , Péptidos y Proteínas de Señalización Intercelular/sangre , Péptidos y Proteínas de Señalización Intercelular/genética , Mutación/genética , Anciano , Anciano de 80 o más Años , Estudios de Casos y Controles , Corteza Cerebral/patología , Estudios de Cohortes , Proteínas de Unión al ADN/metabolismo , Familia , Degeneración Lobar Frontotemporal/patología , Humanos , Inmunohistoquímica , Repeticiones de Microsatélite/genética , Polimorfismo de Nucleótido Simple/genética , ProgranulinasRESUMEN
The apolipoprotein E (APOE) gene remains the most strongly established risk factor for late onset Alzheimer's disease (LOAD). Recently the gene, TOMM40, which is in linkage disequilibrium with APOE, was identified to be associated with LOAD in genome-wide association studies. One of the identified polymorphisms in TOMM40 is rs10524523, which is located in intron 6 and composed of thymidine repeats varying between 14 to 36 base-pairs in length. Reported results are contradictory in regard to the very long poly-T variant that has been associated with both increased and decreased risk of LOAD. Our study aimed to elucidate the functional implication of rs10524523 in an in vitro model of human fibroblast cells obtained from cognitively healthy APOE ε3/ε4 carriers harboring very long or short poly-T variants coupled to their APOE ε3 allele. We have studied (i) expression levels of TOM40 protein and mRNA, (ii) TOM40 mRNA splicing, and (iii) mitochondrial function and morphology; and we have found no significant differences in regards to very long or short poly-T variant.
Asunto(s)
Enfermedad de Alzheimer/diagnóstico , Enfermedad de Alzheimer/genética , Variación Genética/genética , Proteínas de Transporte de Membrana/genética , Poli T/genética , Adulto , Células Cultivadas , Bases de Datos Factuales , Femenino , Fibroblastos/química , Fibroblastos/fisiología , Humanos , Masculino , Persona de Mediana Edad , Proteínas del Complejo de Importación de Proteínas Precursoras MitocondrialesRESUMEN
Two powerful genome-wide association studies have recently reported significant association between sporadic late-onset Alzheimer's disease (AD) and markers at the CLU locus in chromosome 8p. In this study, we have stratified our previously analyzed 109 Swedish AD families according to range in age at onset and performed whole-genome linkage analysis and subsequent fine-mapping in 8p21. The subgroup analyzed in the fine-mapping consisted of 28 families with AD, having a within-family onset-range not exceeding 8 years and an age at onset between 49 ≤ 70 years. A maximum non-parametric linkage peak (LOD = 3.5) was found between markers D8S1809 and 236c6-1. Intriguingly this linked 9.5cM region contains clusterin (CLU), which is one of the two top susceptibility genes for AD. Our finding may be a reflection of linkage to the CLU susceptibility gene, in the same way as familial AD has previously been linked to the APOE locus.
Asunto(s)
Enfermedad de Alzheimer/genética , Cromosomas Humanos Par 8 , Clusterina/genética , Salud de la Familia , Predisposición Genética a la Enfermedad , Polimorfismo Genético/genética , Edad de Inicio , Anciano , Anciano de 80 o más Años , Apolipoproteínas E/genética , Mapeo Cromosómico/métodos , Susceptibilidad a Enfermedades , Femenino , Ligamiento Genético , Estudio de Asociación del Genoma Completo , Humanos , Masculino , Persona de Mediana Edad , SueciaRESUMEN
The Arctic APP mutation (E693G) leads to dementia with clinical features similar to Alzheimer disease (AD), but little is known about the pathogenic mechanism of this mutation. To address this question, we have generated a transgenic mouse model, TgAPParc, with neuron-specific expression of human APP with the Arctic mutation (hAPParc). Heterozygous mice from two separate founder lines with different levels of expression of hAPParc were analyzed with respect to brain morphology and behavior every 3 months until the age of 18 months. Standard histological stainings and immunohistochemistry using a panel of Aß antibodies showed an age- and dose-dependant progression of amyloid deposition in the brain, starting in the subiculum and spreading to the thalamus. Cognitive behavioral testing revealed deficits in hippocampus-dependent spatial learning and memory in the Barnes maze test. This study demonstrates that the Arctic APP mutation is sufficient to cause amyloid deposition and cognitive dysfunction, and thus the TgAPParc mouse model provides a valuable tool to study the effect of the Arctic mutation in vivo without possible confounding effect of other APP mutations.
Asunto(s)
Alanina/genética , Enfermedad de Alzheimer/complicaciones , Enfermedad de Alzheimer/patología , Encéfalo/patología , Trastornos del Conocimiento/etiología , Glicina/genética , Factores de Edad , Enfermedad de Alzheimer/genética , Péptidos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/genética , Animales , Encéfalo/metabolismo , Trastornos del Conocimiento/genética , Progresión de la Enfermedad , Ensayo de Inmunoadsorción Enzimática/métodos , Reacción de Fuga/fisiología , Conducta Exploratoria/fisiología , Humanos , Discapacidades para el Aprendizaje/etiología , Aprendizaje por Laberinto/fisiología , Ratones , Ratones Transgénicos , Mutación/genética , Fragmentos de Péptidos/metabolismo , Estadísticas no ParamétricasRESUMEN
The COL25A1 gene, located in 4q25, encodes the CLAC protein, which has been implicated in Alzheimer's disease (AD) pathogenesis. CLAC was originally identified in amyloid preparations from AD brain and has been shown to be associated with amyloid plaques, inhibition of Abeta-fibril elongation and increased protease resistance of Abeta-fibrils through direct binding to Abeta. These biochemical data as well as the genomic location of the COL25A1 gene in chromosome 4q25 where we previously have reported a weak linkage-signal in Swedish AD families encouraged us to perform a case-control association study of two LD blocks in COL25A1 using 817 AD cases and 364 controls. The LD blocks cover a putative Abeta-binding motif and the variable 3' end of the gene. The analyses indicated association to three of eight analysed SNPs. We found further support for the association by replication in a Swedish population-based longitudinal sample set (n=926). Thus, in addition to the biochemical data, there is now genetic evidence of association between COL25A1 and risk for Alzheimer's disease.
Asunto(s)
Enfermedad de Alzheimer/genética , Colágenos no Fibrilares/genética , Polimorfismo de Nucleótido Simple , Anciano , Anciano de 80 o más Años , Estudios de Casos y Controles , Femenino , Estudios de Seguimiento , Frecuencia de los Genes , Estudios de Asociación Genética , Genotipo , Haplotipos , Humanos , Desequilibrio de Ligamiento , Estudios Longitudinales , Masculino , Placa Amiloide/genética , Análisis de Secuencia de ADN , Suecia , Población Blanca/genéticaRESUMEN
Alzheimer's disease (AD) is a neurodegenerative disease with an insidious onset and progressive course that inevitably leads to death. The current diagnostic tools do not allow for diagnosis until the disease has lead to irreversible brain damage. Genetic studies of autosomal dominant early onset familial AD has identified three causative genes: amyloid precursor protein (APP), presenilin 1 and 2 (PSEN1 and PSEN2). We performed a global gene expression analysis on fibroblasts from 33 individuals (both healthy and demented mutation carriers as well as wild-type siblings) from three families segregating the APP(SWE), APP(ARC) and PSEN1 H163Y mutations, respectively. The mutations cause hereditary progressive cognitive disorder, including typical autosomal dominant AD. Our data show that the mutation carriers share a common gene expression profile significantly different from that of their wild-type siblings. The results indicate that the disease process starts several decades before the onset of cognitive decline, suggesting that presymptomatic diagnosis of AD and other progressive cognitive disorders may be feasible in the near future.
Asunto(s)
Enfermedad de Alzheimer/genética , Precursor de Proteína beta-Amiloide/metabolismo , Perfilación de la Expresión Génica , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Mutación/genética , Precursor de Proteína beta-Amiloide/genética , Análisis por Conglomerados , Fibroblastos/metabolismo , Genes Dominantes/genética , Pruebas Genéticas/métodos , Humanos , Procesamiento de Imagen Asistido por Computador , Análisis por Micromatrices , Presenilina-1 , Análisis de Componente PrincipalRESUMEN
Disease-associated gene polymorphisms provide both scientific insight into pathophysiological mechanisms and clinical information regarding risk and progression. Of special interest is the epsilon4 allele of the apolipoprotein E gene, which has emerged as a substantial risk factor for late-onset forms of Alzheimer disease and also influences the risk of cardiovascular disease. Genotyping of apolipoprotein E can be performed by several methods; presented here are a quality and cost-benefit analysis of four different protocols on a cohort of 42 clinical samples is included in the unit. Each method resulted in genotyping with a high sensitivity and specificity. The newer microtiter-plate-based high-throughput techniques, fluorescence polarization and SNaPshot analysis, were as reliable as the traditional techniques of restriction fragment length polymorphism analysis and reverse hybridization. The reverse hybridization method tends to be more cost- and time-effective when the number of analyses is limited, although economy of scale favors fluorescence polarization or SNaPshot analysis in larger studies. The latter approaches also provide the flexibility to investigate other polymorphic disease markers.