57 research outputs found

    Análise de alterações de sequência nos genes associados à Doença de Niemann-Pick tipo C e avaliação de genes candidatos a modificadores de fenótipo

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    A doença de Niemann-Pick tipo C (NP-C) é uma doença autossômica recessiva causada por mutações nos genes NPC1 ou NPC2 e se caracteriza principalmente pelo acúmulo do colesterol não esterificado no lisossomo/endossomo tardio. Aproximadamente 95% dos pacientes apresentam mutação no gene NPC1 enquanto 5% em NPC2. O gene NPC1 codifica uma glicoproteína transmembrânica de 1278 aminoácidos, com 13 domínios que reside na membrana do lisossomo/endossomo tardio. O produto do gene NPC2 é uma glicoproteína de 132 aminoácidos expressa em todos os tecidos, sendo uma proteína solúvel que se liga ao colesterol. A incidência de NP-C é estimada em 0,95 casos para cada 100.000 nascidos vivos. O objetivo geral deste trabalho foi identificar o genótipo de pacientes com NP-C, determinando a frequência de mutações comuns e caracterizando mutações novas nos genes associados à doença, e analisar variantes de sequência em genes candidatos a modificadores de fenótipo dessa doença. As mutações mais frequentemente encontradas foram p.Ala1035Val (27,3%), p.Pro1007Ala (17,0%) e p.Phe1221Serfs*20 (14,8%). Na identificação das variantes de sequência, foram identificadas 5 novas variantes potencialmente patogênicas, sendo 1 deleção pequena (p.Lys38_Tyr40del), 1 mutação do (p.Asn195Lysfs*2) e 3 mutações de ponto (p.Cys238Arg, p.Ser365Pro e p.Val694Met). Um outro subgrupo de amostras (n=34), proveniente de indivíduos com um único alelo mutante, foram submetidos a uma análise molecular mais abrangente visando a identificação de possíveis rearranjos gênicos. Os resultados obtidos confirmam os relatos que indicam uma frequência muito baixa de rearranjos gênicos associados à NP-C, pois não foi identificado nenhum paciente com perfil anormal através desse protocolo abrangente. Considerando que chaperonas diferentes foram associadas à expressão do gene NPC1, polimorfismos de nucleotídeos únicos (SNPs) nos genes que codificam a chaperona DNAJB6 e a cochaperona CHIP, ambas proteínas do sistema de controle de qualidade proteica, foram selecionados e analisados para investigar uma possível associação com variações fenotípicas de pacientes com NP-C. Essa avaliação permitiu estabelecer as frequências alélicas e genotípicas dos SNPs rs9647660, rs12668448, rs4716707 e rs6459770 (no gene DNAJB6) e o rs6597 (no gene CHIP) nos pacientes e em amostras de indivíduos normais. Os resultados obtidos permitiram comparar os grupos (pacientes e controles) e, dentro do grupo de pacientes, comparar os diferentes fenótipos, mas não foram encontradas diferenças estatisticamente significativas. Além disso, foi avaliado o gene que codifica a apolipoproteína E (ApoE), uma lipoproteína envolvida no metabolismo do colesterol, que se caracteriza por apresentar 3 alelos distintos a partir de dois polimorfismos específicos (rs429358 e rs7412) no gene ApoE. As frequências alélicas de ApoE ε2, ApoE ε3 e ApoE ε4 no grupo de pacientes foi estabelecida em 6,3%, 82,9% e 10,8%, respectivamente. O genótipo mais frequente foi o ApoE ε3/ε3 (63,8%). Apesar de não terem sido encontradas diferenças estatisticamente significativas, não podemos descartar completamente o efeito da ApoE no fenótipo dos pacientes, considerando que esta proteína está presente no metabolismo do colesterol. Por fim, os dados produzidos através desse trabalho contribuem para o melhor conhecimento das bases moleculares da NP-C.Niemann-Pick type C (NP-C) disease is an autosomal recessive disease caused by mutations in the NPC1 or NPC1 genes and is mainly characterized by the storage of non-esterified cholesterol in lysosome/late endosome. Approximately 95% of patients carry mutations in the NPC1 gene while 5% in NPC2. The NPC1 gene encodes a 1278 amino acid transmembrane glycoprotein with 13 domains placed in the membrane of the lysosome/late endosome membrane. The product of NPC2 gene is a 132 amino acid glycoprotein expressed in all tissues, being a soluble protein that binds to cholesterol. The incidence of NP-C is estimated to be 0.95 cases per 100,000 live births. The general aim of this work was to identify the genotype of patients with NP-C, determining the frequency of common mutations and characterizing novel mutations in the genes associated with the disease, and analyzing sequence variants in candidate genes of phenotypic modifiers of the disease. More frequently found mutations were p.Ala1035Val (27.3%), pPro1007Ala (17.0%) and p.Phe1221Serfs*20 (14.8%). In the identification of sequence variants, 5 new potentially pathogenic variants were identified, 1 small deletion (p.Lys38_Tyr40del), 1 mutation (p.Asn195Lysfs*2) and 3 point mutations (p.Cys238Arg, p.Ser365Pro and p.Val694Met). A further subgroup of samples, from individuals with a single mutant allele, were subjected to a more comprehensive molecular analysis to identify possible gene rearrangements. Results of this work confirms previous reports that indicate a very low frequency of gene rearrangements associated with NP-C, since no patient with an abnormal profile was identified through this protocol. Considering that different chaperones were associated with NPC1 gene expression, single nucleotide polymorphisms (SNPs) in the genes encoding the chaperone DNAJB6 and cochaperone CHIP, both proteins of the protein quality control system, were selected and analyzed to investigate a possible association with phenotypic variations of NP-C patients. This evaluation allowed to establish allelic and genotype frequencies of SNPs rs9647660, rs12668448, rs4716707 and rs6459770 (in the DNAJB6 gene) and rs6597 (in the CHIP gene) in samples of NP-C patients and in samples from normal individuals. Results allowed to compare both groups (patients and controls) and, within the group of patients, to compare different clinical phenotypes, but no statistically significant differences were found. In addition, the gene encoding apolipoprotein E (ApoE), a lipoprotein involved in cholesterol metabolism, was evaluated, which is characterized by 3 distinct alleles from two specific polymorphisms (rs429358 and rs7412) in the ApoE gene. The allelic frequencies of ApoE ε2, ApoE ε3 and ApoE ε4 in patient group were established as 6.3%, 82.9%, and 10.8%, respectively. The most frequent genotype was ApoE ε3/ε3 (63.8%). No statistically significant difference was found in the analysis performed. However, we cannot rule out the effect of ApoE on phenotype of patients, considering that this protein is related to cholesterol metabolism. Finally, the data produced through this work contribute to a better understanding of the molecular basis of NP-C

    Are cognitive changes in hereditary spastic paraplegias restricted to complicated forms?

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    Background: Little is known about the cognitive profile of Hereditary Spastic Paraplegias (HSP), where most scientific attention has been given to motor features related to corticospinal tract degeneration. Objectives: We aimed to perform a broad characterization of the cognitive functions of patients with pure and complicated HSP as well as to determine the frequency of abnormal cognitive performances in the studied subtypes. Methods: A two-center cross-sectional case-control study was performed. All individuals underwent cognitive assessment through screening tests (Mini Mental State Examination—MEEM and Montreal Cognitive Assessment—MOCA) and tests to assess specific cognitive functions (Verbal fluency with phonological restriction—FAS; Verbal categorical fluency—FAS-cat and Rey's Verbal Auditory Learning Test -RAVLT). Results: Fifty four patients with genetically confirmed HSP diagnosis, 36 with spastic paraplegia type 4 (SPG4), 5 SPG11, 4 SPG5, 4 cerebrotendinous xanthomatosis (CTX), 3 SPG7 and 2 SPG3A, and 10 healthy, unrelated control subjects, with similar age, sex, and education participated in the study. SPG4 patients had worse performances in MOCA, FAS, FAS-cat, and RAVLT when compared to controls. Most SPG4 patients presented cognitive changes not compatible with dementia, performing poorly in memory, attention and executive functions. SPG5 patients scored lower in executive functions and memory, and SPG7 patients performed poorly on memory tasks. All evaluated cognitive functions were markedly altered in CTX and SPG11 patients. Conclusions: Cognitive abnormalities are frequent in HSP, being more severe in complicated forms. However, cognitive impairments of pure HSPs might impact patients' lives, decreasing families' socioeconomic status and contributing to the overall disease burden

    Prevalência de disfagia orofaríngea nas paraparesias espásticas hereditárias

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    Hereditary spastic paraplegias (HSP) are a group of genetic diseases characterized by lower limb spasticity with or without additional neurological features. Swallowing dysfunction is poorly studied in HSP and its presence can lead to significant respiratory and nutritional complications. Objectives: The aim of this study was to evaluate the frequency and clinical characteristics of dysphagia in different types of HSP. Methods: A two-center cross-sectional prevalence study was performed. Genetically confirmed HSP patients were evaluated using the Northwestern Dysphagia Patient Check Sheet and the Functional Oral Intake Scale. In addition, self-perception of dysphagia was assessed by the Eat Assessment Tool-10 and the Swallowing Disturbance Questionnaire. Results: Thirty-six patients with spastic paraplegia type 4 (SPG4), five with SPG11, four with SPG5, four with cerebrotendinous xanthomatosis (CTX), three with SPG7, and two with SPG3A were evaluated. Mild to moderate oropharyngeal dysphagia was present in 3/5 (60%) of SPG11 and 2/4 (50%) of CTX patients. A single SPG4 (2%) and a single SPG7 (33%) patient had mild oropharyngeal dysphagia. All other evaluated patients presented with normal or functional swallowing. Conclusions: Clinically significant oropharyngeal dysphagia was only present in complicated forms of HSP Patients with SPG11 and CTX had the highest risks for dysphagia, suggesting that surveillance of swallowing function should be part of the management of patients with these disorders.As paraparesias espásticas hereditárias (PEH) são um grupo de doenças genéticas caracterizado por espasticidade dos membros inferiores com ou sem características neurológicas adicionais. A disfunção da deglutição é pouco estudada nas PEH e sua presença pode levar a complicações respiratórias e nutricionais significativas. Objetivo: O objetivo deste estudo foi avaliar a frequência e a caracterização clínica da disfagia em diferentes tipos de PEH. Métodos: Foi realizado um estudo transversal em dois centros. Os pacientes com PEH confirmados geneticamente foram avaliados pelo Northwestern Dysphagia Patient Check Sheet e pela Escala Funcional de Ingestão Oral. Além disso, a autopercepção da disfagia foi avaliada pelo Eat Assessment Tool-10 e pelo Swallowing Disturbance Questionnaire. Resultados: Trinta e seis pacientes com paraplegia espástica tipo 4 (SPG4), cinco com SPG11, quatro com SPG5, quatro com xantomatose cerebrotendinosa (CTX), três com SPG7 e dois com SPG3A foram avaliados. Disfagia orofaríngea leve a moderada estava presente em 3/5 (60%) dos pacientes com SPG11 e 2/4 (50%) dos pacientes com CTX. Um único SPG4 (2%) e um único SPG7 (33%) apresentaram disfagia orofaríngea leve. Todos os outros pacientes avaliados apresentaram deglutição normal ou funcional. Conclusão: Disfagia orofaríngea clinicamente significativa estava presente apenas nas formas complicadas de PEH. A SPG11 e CTX apresentaram maiores riscos de disfagia, sugerindo que a avaliação da deglutição deve fazer parte do manejo dos pacientes com essas condições
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