RESUMO
Flecked-retina syndromes, including fundus flavimaculatus, fundus albipunctatus, and benign fleck retina, comprise a group of disorders with widespread or limited distribution of yellow-white retinal lesions of various sizes and configurations. Three siblings who have benign fleck retina and were born to consanguineous parents are the basis of this report. A combination of homozygosity mapping and exome sequencing helped to identify a homozygous missense mutation, c.133G>T (p.Gly45Cys), in PLA2G5, a gene encoding a secreted phospholipase (group V phospholipase A(2)). A screen of a further four unrelated individuals with benign fleck retina detected biallelic variants in the same gene in three patients. In contrast, no loss of function or common (minor-allele frequency>0.05%) nonsynonymous PLA2G5 variants have been previously reported (EVS, dbSNP, 1000 Genomes Project) or were detected in an internal database of 224 exomes (from subjects with adult onset neurodegenerative disease and without a diagnosis of ophthalmic disease). All seven affected individuals had fundoscopic features compatible with those previously described in benign fleck retina and no visual or electrophysiological deficits. No medical history of major illness was reported. Levels of low-density lipoprotein were mildly elevated in two patients. Optical coherence tomography and fundus autofluorescence findings suggest that group V phospholipase A(2) plays a role in the phagocytosis of photoreceptor outer-segment discs by the retinal pigment epithelium. Surprisingly, immunohistochemical staining of human retinal tissue revealed localization of the protein predominantly in the inner and outer plexiform layers.
Assuntos
Anormalidades do Olho/genética , Fosfolipases A2 do Grupo V/genética , Homozigoto , Mutação de Sentido Incorreto , Retina/anormalidades , Adulto , Idoso de 80 Anos ou mais , Processamento Alternativo , Sequência de Aminoácidos , Sequência de Bases , Criança , Consanguinidade , Feminino , Estudos de Associação Genética , Fosfolipases A2 do Grupo V/metabolismo , Humanos , Masculino , Dados de Sequência Molecular , Linhagem , Polimorfismo de Nucleotídeo Único , Transporte Proteico , Retina/metabolismoRESUMO
BACKGROUND: Rare TREM2 variants are significant risk factors for Alzheimer's disease (AD). METHODS: We used next generation sequencing of the whole gene (n = 700), exon 2 Sanger sequencing (n = 2634), p.R47H genotyping (n = 3518), and genome wide association study imputation (n = 13,048) to determine whether TREM2 variants are risk factors or phenotypic modifiers in patients with AD (n = 1002), frontotemporal dementia (n = 358), sporadic (n = 2500), and variant (n = 115) Creutzfeldt-Jakob disease (CJD). RESULTS: We confirm only p.R47H as a risk factor for AD (odds ratio or OR = 2.19; 95% confidence interval or CI = 1.04-4.51; P = .03). p.R47H does not significantly alter risk for frontotemporal dementia (OR = 0.81), variant or sporadic CJD (OR = 1.06 95%CI = 0.66-1.69) in our cohorts. Individuals with p.R47H associated AD (n = 12) had significantly earlier symptom onset than individuals with no TREM2 variants (n = 551) (55.2 years vs. 61.7 years, P = .02). We note that heterozygous p.R47H AD is memory led and otherwise indistinguishable from "typical" sporadic AD. CONCLUSION: We find p.R47H is a risk factor for AD, but not frontotemporal dementia or prion disease.
Assuntos
Doença de Alzheimer/genética , Arginina/genética , Predisposição Genética para Doença/genética , Variação Genética , Histidina/genética , Glicoproteínas de Membrana/genética , Receptores Imunológicos/genética , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/patologia , Encéfalo/patologia , Estudos de Coortes , Síndrome de Creutzfeldt-Jakob/genética , Síndrome de Creutzfeldt-Jakob/patologia , Éxons/genética , Feminino , Demência Frontotemporal/genética , Demência Frontotemporal/patologia , Estudo de Associação Genômica Ampla , Genótipo , Humanos , Masculino , Pessoa de Meia-Idade , Fenótipo , Fatores de RiscoRESUMO
Human prion diseases are associated with a range of clinical presentations, and they are classified by both clinicopathological syndrome and etiology, with subclassification according to molecular criteria. Here, we describe procedures that are used within the MRC Prion Unit to determine a molecular diagnosis of human prion disease. Sequencing of the PRNP open reading frame to establish the presence of pathogenic mutations is described, together with detailed methods for immunoblot or immunohistochemical determination of the presence of abnormal prion protein in brain or peripheral tissues.
Assuntos
Técnicas de Diagnóstico Molecular/métodos , Doenças Priônicas/diagnóstico , Doenças Priônicas/metabolismo , Sequência de Bases , Humanos , Immunoblotting , Dados de Sequência Molecular , Mutação/genética , Tonsila Palatina/patologia , Proteínas PrPC/genética , Doenças Priônicas/patologiaRESUMO
BACKGROUND: Variant Creutzfeldt-Jakob disease (vCJD) is an acquired prion disease causally related to bovine spongiform encephalopathy that has occurred predominantly in young adults. All clinical cases studied have been methionine homozygotes at codon 129 of the prion protein gene (PRNP) with distinctive neuropathological findings and molecular strain type (PrP(Sc) type 4). Modeling studies in transgenic mice suggest that other PRNP genotypes will also be susceptible to infection with bovine spongiform encephalopathy prions but may develop distinctive phenotypes. OBJECTIVE: To describe the histopathologic and molecular investigation in a young British woman with atypical sporadic CJD and valine homozygosity at PRNP codon 129. DESIGN: Case report, autopsy, and molecular analysis. SETTING: Specialist neurology referral center, together with the laboratory services of the MRC [Medical Research Council] Prion Unit. Subject Single hospitalized patient. MAIN OUTCOME MEASURES: Autopsy findings and molecular investigation results. RESULTS: Autopsy findings were atypical of sporadic CJD, with marked gray and white matter degeneration and widespread prion protein (PrP) deposition. Lymphoreticular tissue was not available for analysis. Molecular analysis of PrP(Sc) (the scrapie isoform of PrP) from cerebellar tissue demonstrated a novel PrP(Sc) type similar to that seen in vCJD (PrP(Sc) type 4). However, this could be distinguished from the typical vCJD pattern by an altered protease cleavage site in the presence of the metal ion chelator EDTA. CONCLUSIONS: Further studies will be required to characterize the prion strain seen in this patient and to investigate its etiologic relationship with bovine spongiform encephalopathy. This case illustrates the importance of molecular analysis of prion disease, including the use of EDTA to investigate the metal dependence of protease cleavage patterns of PrP(Sc).
Assuntos
Síndrome de Creutzfeldt-Jakob/genética , Príons/genética , Adulto , Autopsia , Encéfalo/patologia , Códon , Síndrome de Creutzfeldt-Jakob/patologia , Feminino , Genótipo , Homozigoto , Humanos , Imuno-Histoquímica , Imageamento por Ressonância Magnética , Valina/genéticaRESUMO
Inherited prion diseases are neurodegenerative disorders caused by autosomal dominant mutations in the human prion protein gene (PRNP). Kindred with inherited prion disease can show remarkable phenotypic variability that has yet to be explained. Here we report analysis of protease resistant disease-related prion protein (PrP(Sc)) isoforms from a range of inherited prion disease cases (point mutations P102L, D178N, E200K and 2-, 4- and 6-octapeptide repeat insertions) and show that the glycoform ratios of PrP(Sc) associated with PRNP point mutations are distinct from those observed in sporadic, iatrogenic and variant Creutzfeldt-Jakob disease. Patients with the same PRNP mutation can also propagate PrP(Sc) with distinct conformations. These data extend the spectrum of recognized PrP(Sc) types seen in human prion diseases and provide further insight into the generation of diverse clinicopathological phenotypes associated with inherited prion disease.
Assuntos
Mutação Puntual , Doenças Priônicas/genética , Príons/genética , Síndrome de Creutzfeldt-Jakob/genética , Síndrome de Creutzfeldt-Jakob/metabolismo , Endopeptidase K , Glicosilação , Humanos , Immunoblotting/métodos , Oligopeptídeos/genética , Tonsila Palatina/química , Fenótipo , Proteínas PrPSc/análise , Proteínas PrPSc/metabolismo , Doenças Priônicas/metabolismo , Baço/químicaRESUMO
Human prion diseases are associated with a range of clinical presentations, and they are classified by both clinicopathological syndrome and etiology, with subclassification according to molecular criteria. Here, we describe updated procedures that are currently used within the MRC Prion Unit at UCL to determine a molecular diagnosis of human prion disease. Sequencing of the PRNP open reading frame to establish the presence of pathogenic mutations is described, together with detailed methods for immunoblot or immunohistochemical determination of the presence of abnormal prion protein in the brain or peripheral tissues.
Assuntos
Sequenciamento de Nucleotídeos em Larga Escala , Imuno-Histoquímica/métodos , Mutação , Doenças Priônicas/diagnóstico , Proteínas Priônicas/genética , Coloração e Rotulagem/métodos , Anti-Infecciosos Locais/química , Sequência de Bases , Encéfalo/metabolismo , Encéfalo/patologia , Química Encefálica , Eletroforese em Gel de Poliacrilamida/métodos , Formiatos/química , Expressão Gênica , Humanos , Immunoblotting/métodos , Microtomia/métodos , Fases de Leitura Aberta , Doenças Priônicas/genética , Doenças Priônicas/metabolismo , Doenças Priônicas/patologia , Proteínas Priônicas/metabolismo , Inclusão do Tecido/métodosRESUMO
While rare in humans, the prion diseases have become an area of intense clinical and scientific interest. The recognition that variant Creutzfeldt-Jakob disease is caused by the same prion strain as bovine spongiform encephalopathy in cattle has dramatically highlighted the need for a precise understanding of the molecular biology of human prion diseases. Detailed clinical, pathological and molecular data from a large number of human prion disease cases have shown that distinct abnormal isoforms of prion protein are associated with prion protein gene polymorphism and neuropathological phenotypes. A molecular classification of human prion diseases seems achievable through characterisation of structural differences of the infectious agent itself.
Assuntos
Polimorfismo Genético , Proteínas PrPSc/genética , Doenças Priônicas/classificação , Doenças Priônicas/genética , Adulto , Idoso , Amiloide/análise , Western Blotting , Química Encefálica , Ataxia Cerebelar/etiologia , Síndrome de Creutzfeldt-Jakob/diagnóstico , Síndrome de Creutzfeldt-Jakob/genética , Demência/etiologia , Doenças Genéticas Inatas , Predisposição Genética para Doença , Humanos , Doença Iatrogênica , Pessoa de Meia-Idade , Mioclonia/etiologia , Tonsila Palatina/química , Proteínas PrPSc/análise , Doenças Priônicas/diagnóstico , Proteínas Priônicas , Príons , Precursores de Proteínas/análise , Instrumentos Cirúrgicos , Distribuição TecidualRESUMO
The major determinant of prion disease incubation time in mice is thought to be the amino acid sequence of the prion protein. Two alleles of the mouse prion gene ( Prnp) have been described, where Prnp(a) (Leu-108, Thr-189) and Prnp(b) (Phe-108, Val-189) are associated with short and long incubation times, to defined prion strains, respectively. As part of a survey of inbred mouse lines, the prion gene open reading frame was sequenced and revealed a new allele, Prnp(c) (Phe-108, Thr-189), in the strain MAI/Pas. To study the influence of Prnp(c) independently of the MAI/Pas genetic background, we generated a congenic line in which Prnp(c) was bred onto the C57BL/6JOlaHsd background. Following intracerebral inoculation with Chandler/RML scrapie prions, the congenic mice showed an increased mean incubation time relative to C57BL/6JOlaHsd, of over 100 days. However, no differences were observed in the intensity and pattern of PrP immunoreactivity deposition or spongiosis. We conclude that the new allele, Prnp(c), modulates incubation time but not neuropathology and that the previous classification of mice into two distinct groups based on incubation time and Prnp genotype should now be revised.
Assuntos
Neurônios/metabolismo , Príons/fisiologia , Scrapie/etiologia , Alelos , Animais , Cruzamentos Genéticos , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Neurônios/patologia , Príons/química , Especificidade da Espécie , Relação Estrutura-Atividade , Fatores de TempoRESUMO
Alzheimer's disease (AD) is the commonest neurodegenerative disease worldwide. Rare familial cases may be caused by mutations in one of three genes-amyloid precursor protein, presenilin-1 and presenilin-2; however, the molecular basis of >99% of AD cases is unknown. Somatic mutation has been considered to be a mechanism that may account for a proportion of sporadic cases of AD, but to date there has been no evidence for this. We now report a sporadic early-onset patient with AD, and show that this individual is a somatic mosaic for a mutation in the presenilin-1 gene, suggesting a novel molecular mechanism for AD. Quantification of the mosaicism demonstrated the degree of mosaicism at 8% in peripheral lymphocytes and 14% in cerebral cortex in the index patient; a clear gene dosage effect on age of presentation and clinical phenotypic presentation is demonstrated. This finding has important implications for the aetiology of sporadic AD, and for other apparently sporadic neurodegenerative diseases such as Parkinson's disease, motor neuron disease and Creutzfeldt-Jakob disease.
Assuntos
Doença de Alzheimer/genética , Mutação em Linhagem Germinativa/genética , Proteínas de Membrana/genética , Mosaicismo , Adulto , Idade de Início , Sequência de Bases , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Linhagem , Presenilina-1RESUMO
Kuru is an acquired prion disease largely restricted to the Fore linguistic group of the Papua New Guinea Highlands, which was transmitted during endocannibalistic feasts. Heterozygosity for a common polymorphism in the human prion protein gene (PRNP) confers relative resistance to prion diseases. Elderly survivors of the kuru epidemic, who had multiple exposures at mortuary feasts, are, in marked contrast to younger unexposed Fore, predominantly PRNP 129 heterozygotes. Kuru imposed strong balancing selection on the Fore, essentially eliminating PRNP 129 homozygotes. Worldwide PRNP haplotype diversity and coding allele frequencies suggest that strong balancing selection at this locus occurred during the evolution of modern humans.