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1.
Acta Neuropathol ; 148(1): 21, 2024 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-39150562

RESUMO

Neuronal intranuclear inclusion disease (NIID) is a neurodegenerative disorder caused by the expansion of GGC trinucleotide repeats in NOTCH2NLC gene. Despite identifying uN2CpolyG, a toxic polyglycine (polyG) protein translated by expanded GGC repeats, the exact pathogenic mechanisms of NIID remain unclear. In this study, we investigated the role of polyG by expressing various forms of NOTCH2NLC in mice: the wild-type, the expanded form with 100 GGC repeats (either translating or not translating into uN2CpolyG), and the mutated form that encodes a pure polyG without GGC-repeat RNA and the C-terminal stretch (uN2CpolyG-dCT). Both uN2CpolyG and uN2CpolyG-dCT induced the formation of inclusions composed by filamentous materials and resulted in neurodegenerative phenotypes in mice, including impaired motor and cognitive performance, shortened lifespan, and pathologic lesions such as white-matter lesions, microgliosis, and astrogliosis. In contrast, expressing GGC-repeat RNA alone was non-pathogenic. Through bulk and single-nuclei RNA sequencing, we identified common molecular signatures linked to the expression of uN2CpolyG and uN2CpolyG-dCT, particularly the upregulation of inflammation and microglia markers, and the downregulation of immediate early genes and splicing factors. Importantly, microglia-mediated inflammation was visualized in NIID patients using positron emission tomography, correlating with levels of white-matter atrophy. Furthermore, microglia ablation ameliorated neurodegenerative phenotypes and transcriptional alterations in uN2CpolyG-expressing mice but did not affect polyG inclusions. Together, these results demonstrate that polyG is crucial for the pathogenesis of NIID and highlight the significant role of microglia in polyG-induced neurodegeneration.


Assuntos
Corpos de Inclusão Intranuclear , Microglia , Doenças Neurodegenerativas , Animais , Microglia/patologia , Microglia/metabolismo , Corpos de Inclusão Intranuclear/patologia , Corpos de Inclusão Intranuclear/metabolismo , Doenças Neurodegenerativas/patologia , Doenças Neurodegenerativas/genética , Doenças Neurodegenerativas/metabolismo , Camundongos , Camundongos Transgênicos , Expansão das Repetições de Trinucleotídeos/genética , Humanos , Masculino , Feminino
2.
BMC Neurol ; 24(1): 154, 2024 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-38714961

RESUMO

BACKGROUND: Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder caused by CGG repeat expansion of FMR1 gene. Both FXTAS and neuronal intranuclear inclusion disease (NIID) belong to polyglycine diseases and present similar clinical, radiological, and pathological features, making it difficult to distinguish these diseases. Reversible encephalitis-like attacks are often observed in NIID. It is unclear whether they are presented in FXTAS and can be used for differential diagnosis of NIID and FXTAS. CASE PRESENTATION: A 63-year-old Chinese male with late-onset gait disturbance, cognitive decline, and reversible attacks of fever, consciousness impairment, dizziness, vomiting, and urinary incontinence underwent neurological assessment and examinations, including laboratory tests, electroencephalogram test, imaging, skin biopsy, and genetic test. Brain MRI showed T2 hyperintensities in middle cerebellar peduncle and cerebrum, in addition to cerebellar atrophy and DWI hyperintensities along the corticomedullary junction. Lesions in the brainstem were observed. Skin biopsy showed p62-positive intranuclear inclusions. The possibilities of hypoglycemia, lactic acidosis, epileptic seizures, and cerebrovascular attacks were excluded. Genetic analysis revealed CGG repeat expansion in FMR1 gene, and the number of repeats was 111. The patient was finally diagnosed as FXTAS. He received supportive treatment as well as symptomatic treatment during hospitalization. His encephalitic symptoms were completely relieved within one week. CONCLUSIONS: This is a detailed report of a case of FXTAS with reversible encephalitis-like episodes. This report provides new information for the possible and rare features of FXTAS, highlighting that encephalitis-like episodes are common in polyglycine diseases and unable to be used for differential diagnosis.


Assuntos
Ataxia , Encefalite , Síndrome do Cromossomo X Frágil , Tremor , Humanos , Ataxia/diagnóstico , Ataxia/genética , Diagnóstico Diferencial , Encefalite/diagnóstico , Encefalite/complicações , Encefalite/genética , Encefalite/patologia , Proteína do X Frágil da Deficiência Intelectual/genética , Síndrome do Cromossomo X Frágil/genética , Síndrome do Cromossomo X Frágil/diagnóstico , Síndrome do Cromossomo X Frágil/complicações , Corpos de Inclusão Intranuclear/patologia , Doenças Neurodegenerativas/diagnóstico , Doenças Neurodegenerativas/genética , Doenças Neurodegenerativas/complicações , Tremor/diagnóstico , Tremor/genética , Tremor/etiologia
3.
Seizure ; 111: 122-129, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37625192

RESUMO

PURPOSE: The RELN gene encodes the secreted glycoprotein Reelin and has important functions in both developing and adult brains. In this study, we aimed to explore the association between the RELN and genetic generalized epilepsy (GGE). METHODS: We performed whole-exome sequencing on a cohort of 92 patients with GGE. Based on amino acid sequence alignments, allele frequency, pedigree validation and computational modeling, the RELN variants were identified and clinical features of cases were summarized. Cell-based Reelin secretion assays were examined by Western blotting. Alterations of mutant Reelin transport through the secretion pathway were detected by immunofluorescence staining. RESULTS: Three novel pathogenic RELN variants (3.26%; c.2260C>T/p.R754W, c.2914C>G/p.P972A and c.3029G>A/p.R1010H) were identified. All probands showed adolescence-onset generalized seizures characterized by generalized epileptiform discharges with normal EEG backgrounds, no or mild cognitive impairment, and responded well to anti-seizure medications. All these variants were located in the central regions from 1B to 2A consecutive repeats, and protein modeling demonstrated structural alterations in Reelin. Moreover, we found that these heterozygous missense variants significantly decreased the secretion of mutant proteins in HEK-293T cells, and this impairment was due to the altered transport of mutant Reelin in the secretion pathway. CONCLUSION: These results suggest that RELN is potentially associated with GGE. The phenotype of GGE caused by RELN variants is relatively mild, and the pathogenic mechanism may involve a loss-of-function.

4.
Acta Neuropathol ; 142(6): 1003-1023, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-34694469

RESUMO

Neuronal intranuclear inclusion disease (NIID) is neurodegenerative disease characterized by widespread inclusions. Despite the identification of GGC repeat expansion in 5'UTR of NOTCH2NLC gene in adult-onset NIIDs, its pathogenic mechanism remains unclear. Gain-of-function poly-amino-acid proteins generated by unconventional translation have been revealed in nucleotide repeat expansion disorders, inspiring us to explore the possibility of unconventional translation in NIID. Here we demonstrated that NOTCH2NLC 5'UTR triggers the translation of a polyglycine (polyG)-containing protein, N2NLCpolyG. N2NLCpolyG accumulates in p62-positive inclusions in cultured cells, mouse models, and NIID patient tissues with NOTCH2NLC GGC expansion. Translation of N2NLCpolyG is initiated by an upstream open reading frame (uORF) embedding the GGC repeats. N2NLCpolyG tends to aggregate with the increase of GGC repeat units, and displays phase separation properties. N2NLCpolyG aggregation impairs nuclear lamina and nucleocytoplasmic transport but does not necessarily cause acute death on neuronal cells. Our study suggests a similarity of pathogenic mechanisms between NIID and another GGC-repeat disease, fragile X-associated tremor ataxia syndrome. These findings expand our knowledge of protein gain-of-function in NIID, and further highlight evidence for a novel spectrum of diseases caused by aberrant polyG protein aggregation, namely the polyG diseases.


Assuntos
Transporte Ativo do Núcleo Celular/fisiologia , Peptídeos e Proteínas de Sinalização Intercelular/genética , Proteínas do Tecido Nervoso/genética , Doenças Neurodegenerativas/metabolismo , Peptídeos/genética , Expansão das Repetições de Trinucleotídeos/genética , Animais , Humanos , Corpos de Inclusão Intranuclear/genética , Corpos de Inclusão Intranuclear/metabolismo , Camundongos , Doenças Neurodegenerativas/genética , Fases de Leitura Aberta , Biossíntese de Proteínas
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