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1.
Am J Hum Genet ; 109(9): 1692-1712, 2022 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-36055214

RESUMO

Leucine zipper-EF-hand containing transmembrane protein 1 (LETM1) encodes an inner mitochondrial membrane protein with an osmoregulatory function controlling mitochondrial volume and ion homeostasis. The putative association of LETM1 with a human disease was initially suggested in Wolf-Hirschhorn syndrome, a disorder that results from de novo monoallelic deletion of chromosome 4p16.3, a region encompassing LETM1. Utilizing exome sequencing and international gene-matching efforts, we have identified 18 affected individuals from 11 unrelated families harboring ultra-rare bi-allelic missense and loss-of-function LETM1 variants and clinical presentations highly suggestive of mitochondrial disease. These manifested as a spectrum of predominantly infantile-onset (14/18, 78%) and variably progressive neurological, metabolic, and dysmorphic symptoms, plus multiple organ dysfunction associated with neurodegeneration. The common features included respiratory chain complex deficiencies (100%), global developmental delay (94%), optic atrophy (83%), sensorineural hearing loss (78%), and cerebellar ataxia (78%) followed by epilepsy (67%), spasticity (53%), and myopathy (50%). Other features included bilateral cataracts (42%), cardiomyopathy (36%), and diabetes (27%). To better understand the pathogenic mechanism of the identified LETM1 variants, we performed biochemical and morphological studies on mitochondrial K+/H+ exchange activity, proteins, and shape in proband-derived fibroblasts and muscles and in Saccharomyces cerevisiae, which is an important model organism for mitochondrial osmotic regulation. Our results demonstrate that bi-allelic LETM1 variants are associated with defective mitochondrial K+ efflux, swollen mitochondrial matrix structures, and loss of important mitochondrial oxidative phosphorylation protein components, thus highlighting the implication of perturbed mitochondrial osmoregulation caused by LETM1 variants in neurological and mitochondrial pathologies.


Assuntos
Proteínas de Ligação ao Cálcio , Doenças Mitocondriais , Proteínas de Ligação ao Cálcio/genética , Homeostase/genética , Humanos , Proteínas de Membrana/genética , Mitocôndrias/genética , Mitocôndrias/metabolismo , Doenças Mitocondriais/genética , Doenças Mitocondriais/metabolismo , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismo , Sistema Nervoso/metabolismo , Saccharomyces cerevisiae/metabolismo
2.
Brain ; 147(7): 2334-2343, 2024 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-38527963

RESUMO

Heterozygous RTN2 variants have been previously identified in a limited cohort of families affected by autosomal dominant spastic paraplegia (SPG12-OMIM:604805) with a variable age of onset. Nevertheless, the definitive validity of SPG12 remains to be confidently confirmed due to the scarcity of supporting evidence. In this study, we identified and validated seven novel or ultra-rare homozygous loss-of-function RTN2 variants in 14 individuals from seven consanguineous families with distal hereditary motor neuropathy (dHMN) using exome, genome and Sanger sequencing coupled with deep-phenotyping. All affected individuals (seven males and seven females, aged 9-50 years) exhibited weakness in the distal upper and lower limbs, lower limb spasticity and hyperreflexia, with onset in the first decade of life. Nerve conduction studies revealed axonal motor neuropathy with neurogenic changes in the electromyography. Despite a slowly progressive disease course, all patients remained ambulatory over a mean disease duration of 19.71 ± 13.70 years. Characterization of Caenorhabditis elegans RTN2 homologous loss-of-function variants demonstrated morphological and behavioural differences compared with the parental strain. Treatment of the mutant with an endoplasmic/sarcoplasmic reticulum Ca2+ reuptake inhibitor (2,5-di-tert-butylhydroquinone) rescued key phenotypic differences, suggesting a potential therapeutic benefit for RTN2-disorder. Despite RTN2 being an endoplasmic reticulum (ER)-resident membrane shaping protein, our analysis of patient fibroblast cells did not find significant alterations in ER structure or the response to ER stress. Our findings delineate a distinct form of autosomal recessive dHMN with pyramidal features associated with RTN2 deficiency. This phenotype shares similarities with SIGMAR1-related dHMN and Silver-like syndromes, providing valuable insights into the clinical spectrum and potential therapeutic strategies for RTN2-related dHMN.


Assuntos
Linhagem , Humanos , Masculino , Feminino , Criança , Adulto , Adolescente , Adulto Jovem , Pessoa de Meia-Idade , Animais , Extremidade Inferior/fisiopatologia , Caenorhabditis elegans , Espasticidade Muscular/genética , Espasticidade Muscular/fisiopatologia , Paraplegia Espástica Hereditária/genética , Paraplegia Espástica Hereditária/fisiopatologia , Mutação
3.
Am J Hum Genet ; 107(2): 311-324, 2020 08 06.
Artigo em Inglês | MEDLINE | ID: mdl-32738225

RESUMO

Aminoacyl-tRNA synthetases (ARSs) are ubiquitous, ancient enzymes that charge amino acids to cognate tRNA molecules, the essential first step of protein translation. Here, we describe 32 individuals from 21 families, presenting with microcephaly, neurodevelopmental delay, seizures, peripheral neuropathy, and ataxia, with de novo heterozygous and bi-allelic mutations in asparaginyl-tRNA synthetase (NARS1). We demonstrate a reduction in NARS1 mRNA expression as well as in NARS1 enzyme levels and activity in both individual fibroblasts and induced neural progenitor cells (iNPCs). Molecular modeling of the recessive c.1633C>T (p.Arg545Cys) variant shows weaker spatial positioning and tRNA selectivity. We conclude that de novo and bi-allelic mutations in NARS1 are a significant cause of neurodevelopmental disease, where the mechanism for de novo variants could be toxic gain-of-function and for recessive variants, partial loss-of-function.


Assuntos
Aspartato-tRNA Ligase/genética , Mutação com Ganho de Função/genética , Mutação com Perda de Função/genética , Transtornos do Neurodesenvolvimento/genética , Aminoacil-RNA de Transferência/genética , Alelos , Aminoacil-tRNA Sintetases/genética , Linhagem Celular , Feminino , Predisposição Genética para Doença/genética , Humanos , Masculino , Linhagem , RNA de Transferência/genética , Células-Tronco/fisiologia
4.
Eur J Neurol ; 30(2): 399-412, 2023 02.
Artigo em Inglês | MEDLINE | ID: mdl-36303290

RESUMO

BACKGROUND AND PURPOSE: Clinical outcome information on patients with neuromuscular diseases (NMDs) who have been infected with SARS-CoV-2 is limited. The aim of this study was to determine factors associated with the severity of COVID-19 outcomes in people with NMDs. METHODS: Cases of NMD, of any age, and confirmed/presumptive COVID-19, submitted to the International Neuromuscular COVID-19 Registry up to 31 December 2021, were included. A mutually exclusive ordinal COVID-19 severity scale was defined as follows: (1) no hospitalization; (2) hospitalization without oxygenation; (3) hospitalization with ventilation/oxygenation; and (4) death. Multivariable ordinal logistic regression analyses were used to estimate odds ratios (ORs) for severe outcome, adjusting for age, sex, race/ethnicity, NMD, comorbidities, baseline functional status (modified Rankin scale [mRS]), use of immunosuppressive/immunomodulatory medication, and pandemic calendar period. RESULTS: Of 315 patients from 13 countries (mean age 50.3 [±17.7] years, 154 [48.9%] female), 175 (55.5%) were not hospitalized, 27 (8.6%) were hospitalized without supplemental oxygen, 91 (28.9%) were hospitalized with ventilation/supplemental oxygen, and 22 (7%) died. Higher odds of severe COVID-19 outcomes were observed for: age ≥50 years (50-64 years: OR 2.4, 95% confidence interval [CI] 1.33-4.31; >64 years: OR 4.16, 95% CI 2.12-8.15; both vs. <50 years); non-White race/ethnicity (OR 1.81, 95% CI 1.07-3.06; vs. White); mRS moderately severe/severe disability (OR 3.02, 95% CI 1.6-5.69; vs. no/slight/moderate disability); history of respiratory dysfunction (OR 3.16, 95% CI 1.79-5.58); obesity (OR 2.24, 95% CI 1.18-4.25); ≥3 comorbidities (OR 3.2, 95% CI 1.76-5.83; vs. ≤2; if comorbidity count used instead of specific comorbidities); glucocorticoid treatment (OR 2.33, 95% CI 1.14-4.78); and Guillain-Barré syndrome (OR 3.1, 95% CI 1.35-7.13; vs. mitochondrial disease). CONCLUSIONS: Among people with NMDs, there is a differential risk of COVID-19 outcomes according to demographic and clinical characteristics. These findings could be used to develop tailored management strategies and evidence-based recommendations for NMD patients.


Assuntos
COVID-19 , Doenças Neuromusculares , Humanos , Feminino , Pessoa de Meia-Idade , Masculino , SARS-CoV-2 , Doenças Neuromusculares/epidemiologia , Sistema de Registros , Oxigênio
5.
Mol Biol Rep ; 48(3): 2093-2104, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33742325

RESUMO

Mutations in nuclear-encoded protein subunits of the mitochondrial ribosome are an increasingly recognised cause of oxidative phosphorylation system (OXPHOS) disorders. Among them, mutations in the MRPL44 gene, encoding a structural protein of the large subunit of the mitochondrial ribosome, have been identified in four patients with OXPHOS defects and early-onset hypertrophic cardiomyopathy with or without additional clinical features. A 23-year-old individual with cardiac and skeletal myopathy, neurological involvement, and combined deficiency of OXPHOS complexes in skeletal muscle was clinically and genetically investigated. Analysis of whole-exome sequencing data revealed a homozygous mutation in MRPL44 (c.467 T > G), which was not present in the biological father, and a region of homozygosity involving most of chromosome 2, raising the possibility of uniparental disomy. Short-tandem repeat and genome-wide SNP microarray analyses of the family trio confirmed complete maternal uniparental isodisomy of chromosome 2. Mitochondrial ribosome assembly and mitochondrial translation were assessed in patient derived-fibroblasts. These studies confirmed that c.467 T > G affects the stability or assembly of the large subunit of the mitochondrial ribosome, leading to impaired mitochondrial protein synthesis and decreased levels of multiple OXPHOS components. This study provides evidence of complete maternal uniparental isodisomy of chromosome 2 in a patient with MRPL44-related disease, and confirms that MRLP44 mutations cause a mitochondrial translation defect that may present as a multisystem disorder with neurological involvement.


Assuntos
Cromossomos Humanos Par 2/genética , Doenças Mitocondriais/genética , Proteínas Mitocondriais/genética , Proteínas Ribossômicas/genética , Dissomia Uniparental/genética , Adolescente , Sequência de Bases , Encéfalo/diagnóstico por imagem , Encéfalo/patologia , Pré-Escolar , Feminino , Fibroblastos/patologia , Homozigoto , Humanos , Lactente , Recém-Nascido , Imageamento por Ressonância Magnética , Doenças Mitocondriais/patologia , Músculo Esquelético/metabolismo , Mutação/genética , Fosforilação Oxidativa , Biossíntese de Proteínas , Adulto Jovem
6.
Brain ; 143(2): 480-490, 2020 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-32040566

RESUMO

Ataxia, causing imbalance, dizziness and falls, is a leading cause of neurological disability. We have recently identified a biallelic intronic AAGGG repeat expansion in replication factor complex subunit 1 (RFC1) as the cause of cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS) and a major cause of late onset ataxia. Here we describe the full spectrum of the disease phenotype in our first 100 genetically confirmed carriers of biallelic repeat expansions in RFC1 and identify the sensory neuropathy as a common feature in all cases to date. All patients were Caucasian and half were sporadic. Patients typically reported progressive unsteadiness starting in the sixth decade. A dry spasmodic cough was also frequently associated and often preceded by decades the onset of walking difficulty. Sensory symptoms, oscillopsia, dysautonomia and dysarthria were also variably associated. The disease seems to follow a pattern of spatial progression from the early involvement of sensory neurons, to the later appearance of vestibular and cerebellar dysfunction. Half of the patients needed walking aids after 10 years of disease duration and a quarter were wheelchair dependent after 15 years. Overall, two-thirds of cases had full CANVAS. Sensory neuropathy was the only manifestation in 15 patients. Sixteen patients additionally showed cerebellar involvement, and six showed vestibular involvement. The disease is very likely to be underdiagnosed. Repeat expansion in RFC1 should be considered in all cases of sensory ataxic neuropathy, particularly, but not only, if cerebellar dysfunction, vestibular involvement and cough coexist.


Assuntos
Ataxia/fisiopatologia , Ataxia Cerebelar/fisiopatologia , Doenças do Sistema Nervoso Periférico/fisiopatologia , Neuronite Vestibular/fisiopatologia , Idoso , Idoso de 80 Anos ou mais , Ataxia/complicações , Cerebelo/fisiopatologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Exame Neurológico/efeitos adversos , Doenças do Sistema Nervoso Periférico/complicações , Reflexo Anormal/fisiologia , Transtornos de Sensação/etiologia , Transtornos de Sensação/fisiopatologia , Síndrome , Neuronite Vestibular/complicações
7.
Cephalalgia ; 40(9): 959-965, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32295401

RESUMO

BACKGROUND: Epicrania fugax consists of brief paroxysms of pain, which radiate in a line or in zigzag trajectory across the surface of the scalp or the face. METHODS: A prospective, descriptive study was performed in five patients presenting with an epicrania fugax-type pain with extracephalic irradiation. RESULTS: All patients were women, and the mean age at onset was 59.8 (standard deviation, 10.9). They had unilateral paroxysms of electrical pain starting at a particular point in the head (parietal, n = 3; vertex, n = 1; frontal, n = 1) and rapidly radiating downwards in a lineal trajectory to reach extracephalic regions (ipsilateral limbs, n = 2; shoulder, n = 2; low neck, n = 1) in 1-3 seconds. Pain intensity was moderate or severe. Three patients had nummular headache at the point where the paroxysms originated. One patient had spontaneous remission, and four patients achieved complete or almost complete response with therapy (onabotulinumtoxinA, n = 2; indomethacin, n = 1; amitriptyline, n = 1; lamotrigine, n = 1). CONCLUSION: The spectrum of epicrania fugax may include paroxysms with extracephalic irradiation. The propagation of pain beyond the head and the face supports the involvement of central mechanisms in the pathophysiology of this entity.


Assuntos
Cefaleia/fisiopatologia , Idoso , Feminino , Humanos , Pessoa de Meia-Idade
8.
Hum Genet ; 138(11-12): 1313-1322, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31673819

RESUMO

Pyruvate dehydrogenase complex (PDC) deficiency caused by mutations in the X-linked PDHA1 gene has a broad clinical presentation, and the pattern of X-chromosome inactivation has been proposed as a major factor contributing to its variable expressivity in heterozygous females. Here, we report the first set of monozygotic twin females with PDC deficiency, caused by a novel, de novo heterozygous missense mutation in exon 11 of PDHA1 (NM_000284.3: c.1100A>T). Both twins presented in infancy with a similar clinical phenotype including developmental delay, episodes of hypotonia or encephalopathy, epilepsy, and slowly progressive motor impairment due to pyramidal, extrapyramidal, and cerebellar involvement. However, they exhibited clear differences in disease severity that correlated well with residual PDC activities (approximately 60% and 20% of mean control values, respectively) and levels of immunoreactive E1α subunit in cultured skin fibroblasts. To address whether the observed clinical and biochemical differences could be explained by the pattern of X-chromosome inactivation, we undertook an androgen receptor assay in peripheral blood. In the less severely affected twin, a significant bias in the relative activity of the two X chromosomes with a ratio of approximately 75:25 was detected, while the ratio was close to 50:50 in the other twin. Although it may be difficult to extrapolate these results to other tissues, our observation provides further support to the hypothesis that the pattern of X-chromosome inactivation may influence the phenotypic expression of the same mutation in heterozygous females and broadens the clinical and genetic spectrum of PDC deficiency.


Assuntos
Mutação , Piruvato Desidrogenase (Lipoamida)/genética , Doença da Deficiência do Complexo de Piruvato Desidrogenase/genética , Doença da Deficiência do Complexo de Piruvato Desidrogenase/patologia , Inativação do Cromossomo X , Feminino , Humanos , Masculino , Linhagem , Fenótipo , Prognóstico , Piruvato Desidrogenase (Lipoamida)/deficiência , Gêmeos Monozigóticos
9.
Am J Hum Genet ; 98(4): 597-614, 2016 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-27040688

RESUMO

Abnormal protein aggregation is observed in an expanding number of neurodegenerative diseases. Here, we describe a mechanism for intracellular toxic protein aggregation induced by an unusual mutation event in families affected by axonal neuropathy. These families carry distinct frameshift variants in NEFH (neurofilament heavy), leading to a loss of the terminating codon and translation of the 3' UTR into an extra 40 amino acids. In silico aggregation prediction suggested the terminal 20 residues of the altered NEFH to be amyloidogenic, which we confirmed experimentally by serial deletion analysis. The presence of this amyloidogenic motif fused to NEFH caused prominent and toxic protein aggregates in transfected cells and disrupted motor neurons in zebrafish. We identified a similar aggregation-inducing mechanism in NEFL (neurofilament light) and FUS (fused in sarcoma), in which mutations are known to cause aggregation in Charcot-Marie-Tooth disease and amyotrophic lateral sclerosis, respectively. In summary, we present a protein-aggregation-triggering mechanism that should be taken into consideration during the evaluation of stop-loss variants.


Assuntos
Regiões 3' não Traduzidas/genética , Axônios/patologia , Filamentos Intermediários/genética , Neurônios Motores/patologia , Sequência de Aminoácidos , Esclerose Lateral Amiotrófica/genética , Animais , Linhagem Celular , Doença de Charcot-Marie-Tooth/genética , Mutação da Fase de Leitura , Humanos , Filamentos Intermediários/metabolismo , Camundongos , Dados de Sequência Molecular , Neurônios Motores/metabolismo , Mutação , Linhagem , Peixe-Zebra/genética
10.
Brain ; 140(11): 2820-2837, 2017 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-29053833

RESUMO

Brown-Vialetto-Van Laere syndrome represents a phenotypic spectrum of motor, sensory, and cranial nerve neuropathy, often with ataxia, optic atrophy and respiratory problems leading to ventilator-dependence. Loss-of-function mutations in two riboflavin transporter genes, SLC52A2 and SLC52A3, have recently been linked to Brown-Vialetto-Van Laere syndrome. However, the genetic frequency, neuropathology and downstream consequences of riboflavin transporter mutations are unclear. By screening a large cohort of 132 patients with early-onset severe sensory, motor and cranial nerve neuropathy we confirmed the strong genetic link between riboflavin transporter mutations and Brown-Vialetto-Van Laere syndrome, identifying 22 pathogenic mutations in SLC52A2 and SLC52A3, 14 of which were novel. Brain and spinal cord neuropathological examination of two cases with SLC52A3 mutations showed classical symmetrical brainstem lesions resembling pathology seen in mitochondrial disease, including severe neuronal loss in the lower cranial nerve nuclei, anterior horns and corresponding nerves, atrophy of the spinothalamic and spinocerebellar tracts and posterior column-medial lemniscus pathways. Mitochondrial dysfunction has previously been implicated in an array of neurodegenerative disorders. Since riboflavin metabolites are critical components of the mitochondrial electron transport chain, we hypothesized that reduced riboflavin transport would result in impaired mitochondrial activity, and confirmed this using in vitro and in vivo models. Electron transport chain complex I and complex II activity were decreased in SLC52A2 patient fibroblasts, while global knockdown of the single Drosophila melanogaster riboflavin transporter homologue revealed reduced levels of riboflavin, downstream metabolites, and electron transport chain complex I activity. This in turn led to abnormal mitochondrial membrane potential, respiratory chain activity and morphology. Riboflavin transporter knockdown in Drosophila also resulted in severely impaired locomotor activity and reduced lifespan, mirroring patient pathology, and these phenotypes could be partially rescued using a novel esterified derivative of riboflavin. Our findings expand the genetic, clinical and neuropathological features of Brown-Vialetto-Van Laere syndrome, implicate mitochondrial dysfunction as a downstream consequence of riboflavin transporter gene defects, and validate riboflavin esters as a potential therapeutic strategy.


Assuntos
Encéfalo/patologia , Paralisia Bulbar Progressiva/genética , Perda Auditiva Neurossensorial/genética , Proteínas de Membrana Transportadoras/genética , Receptores Acoplados a Proteínas G/genética , Medula Espinal/patologia , Adolescente , Animais , Atrofia , Encéfalo/ultraestrutura , Paralisia Bulbar Progressiva/metabolismo , Paralisia Bulbar Progressiva/patologia , Criança , Pré-Escolar , Citrato (si)-Sintase/metabolismo , Drosophila melanogaster , Complexo I de Transporte de Elétrons/metabolismo , Complexo II de Transporte de Elétrons/metabolismo , Complexo III da Cadeia de Transporte de Elétrons/metabolismo , Feminino , Fibroblastos/metabolismo , Técnicas de Silenciamento de Genes , Perda Auditiva Neurossensorial/metabolismo , Perda Auditiva Neurossensorial/patologia , Humanos , Técnicas In Vitro , Lactente , Locomoção/genética , Longevidade/genética , Masculino , Microscopia Eletrônica , Vias Neurais , Riboflavina , Tratos Espinocerebelares/patologia , Tratos Espinotalâmicos/patologia , Adulto Jovem
11.
Neurogenetics ; 18(1): 63-67, 2017 01.
Artigo em Inglês | MEDLINE | ID: mdl-28005197

RESUMO

Biallelic mutations in the SBF1 gene have been identified in one family with demyelinating Charcot-Marie-Tooth disease (CMT4B3) and two families with axonal neuropathy and additional neurological and skeletal features. Here we describe novel sequence variants in SBF1 (c.1168C>G and c.2209_2210del) as the potential causative mutations in two siblings with severe axonal neuropathy, hearing loss, facial weakness and bulbar features. Pathogenicity of these variants is supported by co-segregation and in silico analyses and evolutionary conservation. Our findings suggest that SBF1 mutations may cause a syndromic form of autosomal recessive axonal neuropathy (AR-CMT2) in addition to CMT4B3.


Assuntos
Doença de Charcot-Marie-Tooth/genética , Doenças dos Nervos Cranianos/genética , Peptídeos e Proteínas de Sinalização Intracelular/genética , Mutação de Sentido Incorreto , Malformações do Sistema Nervoso/genética , Adulto , Atrofia/genética , Axônios/patologia , Doença de Charcot-Marie-Tooth/complicações , Doença de Charcot-Marie-Tooth/patologia , Doenças dos Nervos Cranianos/patologia , Nervos Cranianos/anormalidades , Nervos Cranianos/patologia , Genes Recessivos , Perda Auditiva/genética , Perda Auditiva/patologia , Humanos , Masculino , Linhagem , Irmãos
12.
Am J Hum Genet ; 95(5): 590-601, 2014 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-25439726

RESUMO

Using a combination of exome sequencing and linkage analysis, we investigated an English family with two affected siblings in their 40s with recessive Charcot-Marie Tooth disease type 2 (CMT2). Compound heterozygous mutations in the immunoglobulin-helicase-µ-binding protein 2 (IGHMBP2) gene were identified. Further sequencing revealed a total of 11 CMT2 families with recessively inherited IGHMBP2 gene mutations. IGHMBP2 mutations usually lead to spinal muscular atrophy with respiratory distress type 1 (SMARD1), where most infants die before 1 year of age. The individuals with CMT2 described here, have slowly progressive weakness, wasting and sensory loss, with an axonal neuropathy typical of CMT2, but no significant respiratory compromise. Segregating IGHMBP2 mutations in CMT2 were mainly loss-of-function nonsense in the 5' region of the gene in combination with a truncating frameshift, missense, or homozygous frameshift mutations in the last exon. Mutations in CMT2 were predicted to be less aggressive as compared to those in SMARD1, and fibroblast and lymphoblast studies indicate that the IGHMBP2 protein levels are significantly higher in CMT2 than SMARD1, but lower than controls, suggesting that the clinical phenotype differences are related to the IGHMBP2 protein levels.


Assuntos
Doença de Charcot-Marie-Tooth/genética , Exoma/genética , Modelos Moleculares , Mutação de Sentido Incorreto/genética , Fenótipo , Adulto , Sequência de Bases , Doença de Charcot-Marie-Tooth/patologia , Mapeamento Cromossômico , Feminino , Haplótipos/genética , Humanos , Dados de Sequência Molecular , Linhagem , Mapeamento de Interação de Proteínas , Análise de Sequência de DNA , Nervo Sural/patologia
13.
J Neurol Neurosurg Psychiatry ; 88(7): 575-585, 2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-28501821

RESUMO

OBJECTIVES: To analyse and describe the clinical and genetic spectrum of Charcot-Marie-Tooth disease (CMT) caused by mutations in the neurofilament light polypeptide gene (NEFL). METHODS: Combined analysis of newly identified patients with NEFL-related CMT and all previously reported cases from the literature. RESULTS: Five new unrelated patients with CMT carrying the NEFL mutations P8R and N98S and the novel variant L311P were identified. Combined data from these cases and 62 kindreds from the literature revealed four common mutations (P8R, P22S, N98S and E396K) and three mutational hotspots accounting for 37 (55%) and 50 (75%) kindreds, respectively. Eight patients had de novo mutations. Loss of large-myelinated fibres was a uniform feature in a total of 21 sural nerve biopsies and 'onion bulb' formations and/or thin myelin sheaths were observed in 14 (67%) of them. The neurophysiological phenotype was broad but most patients with E90K and N98S had upper limb motor conduction velocities <38 m/s. Age of onset was ≤3 years in 25 cases. Pyramidal tract signs were described in 13 patients and 7 patients were initially diagnosed with or tested for inherited ataxia. Patients with E90K and N98S frequently presented before age 3 years and developed hearing loss or other neurological features including ataxia and/or cerebellar atrophy on brain MRI. CONCLUSIONS: NEFL-related CMT is clinically and genetically heterogeneous. Based on this study, however, we propose mutational hotspots and relevant clinical-genetic associations that may be helpful in the evaluation of NEFL sequence variants and the differential diagnosis with other forms of CMT.


Assuntos
Doença de Charcot-Marie-Tooth/genética , Doença de Charcot-Marie-Tooth/patologia , Mutação/genética , Proteínas de Neurofilamentos/genética , Axônios/patologia , Ataxia Cerebelar/genética , Ataxia Cerebelar/patologia , Genótipo , Humanos , Linhagem , Fenótipo , Nervo Sural/patologia
14.
J Peripher Nerv Syst ; 22(4): 460-463, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-28834584

RESUMO

Mutations in the kinesin family member 1A (KIF1A) gene have been associated with a wide range of phenotypes including recessive mutations causing hereditary sensory neuropathy and hereditary spastic paraplegia and de novo dominant mutations causing a more complex neurological disorder affecting both the central and peripheral nervous system. We identified by exome sequencing a de novo dominant missense variant, (c.38G>A, p.R13H), within an ATP binding site of the kinesin motor domain in a patient manifesting a complex phenotype characterized by autism spectrum disorder (ASD), spastic paraplegia and axonal neuropathy. The presence of ASD distinguishes this case from previously reported patients with de novo dominant mutations in KIF1A.


Assuntos
Transtorno do Espectro Autista/genética , Cinesinas/genética , Paraplegia/genética , Doenças do Sistema Nervoso Periférico/genética , Adulto , Humanos , Masculino , Mutação de Sentido Incorreto , Paraplegia/fisiopatologia , Doenças do Sistema Nervoso Periférico/fisiopatologia , Fenótipo , Adulto Jovem
15.
Brain ; 137(Pt 12): 3200-12, 2014 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25281868

RESUMO

Progressive external ophthalmoplegia is a common clinical feature in mitochondrial disease caused by nuclear DNA defects and single, large-scale mitochondrial DNA deletions and is less frequently associated with point mutations of mitochondrial DNA. Peripheral neuropathy is also a frequent manifestation of mitochondrial disease, although its prevalence and characteristics varies considerably among the different syndromes and genetic aetiologies. Based on clinical observations, we systematically investigated whether the presence of peripheral neuropathy could predict the underlying genetic defect in patients with progressive external ophthalmoplegia. We analysed detailed demographic, clinical and neurophysiological data from 116 patients with genetically-defined mitochondrial disease and progressive external ophthalmoplegia. Seventy-eight patients (67%) had a single mitochondrial DNA deletion, 12 (10%) had a point mutation of mitochondrial DNA and 26 (22%) had mutations in either POLG, C10orf2 or RRM2B, or had multiple mitochondrial DNA deletions in muscle without an identified nuclear gene defect. Seventy-seven patients had neurophysiological studies; of these, 16 patients (21%) had a large-fibre peripheral neuropathy. The prevalence of peripheral neuropathy was significantly lower in patients with a single mitochondrial DNA deletion (2%) as compared to those with a point mutation of mitochondrial DNA or with a nuclear DNA defect (44% and 52%, respectively; P<0.001). Univariate analyses revealed significant differences in the distribution of other clinical features between genotypes, including age at disease onset, gender, family history, progressive external ophthalmoplegia at clinical presentation, hearing loss, pigmentary retinopathy and extrapyramidal features. However, binomial logistic regression analysis identified peripheral neuropathy as the only independent predictor associated with a nuclear DNA defect (P=0.002; odds ratio 8.43, 95% confidence interval 2.24-31.76). Multinomial logistic regression analysis identified peripheral neuropathy, family history and hearing loss as significant predictors of the genotype, and the same three variables showed the highest performance in genotype classification in a decision tree analysis. Of these variables, peripheral neuropathy had the highest specificity (91%), negative predictive value (83%) and positive likelihood ratio (5.87) for the diagnosis of a nuclear DNA defect. These results indicate that peripheral neuropathy is a rare finding in patients with single mitochondrial DNA deletions but that it is highly predictive of an underlying nuclear DNA defect. This observation may facilitate the development of diagnostic algorithms. We suggest that nuclear gene testing may enable a more rapid diagnosis and avoid muscle biopsy in patients with progressive external ophthalmoplegia and peripheral neuropathy.


Assuntos
Núcleo Celular/genética , DNA Mitocondrial/genética , Predisposição Genética para Doença , Mitocôndrias/genética , Oftalmoplegia Externa Progressiva Crônica/genética , Doenças do Sistema Nervoso Periférico/genética , Adolescente , Adulto , Feminino , Genótipo , Humanos , Masculino , Pessoa de Meia-Idade , Mutação/genética , Adulto Jovem
16.
Neurology ; 102(7): e209174, 2024 Apr 09.
Artigo em Inglês | MEDLINE | ID: mdl-38513194

RESUMO

BACKGROUND AND OBJECTIVES: Germline truncating variants in the DRP2 gene (encoding dystrophin-related protein 2) cause the disruption of the periaxin-DRP2-dystroglycan complex and have been linked to Charcot-Marie-Tooth disease. However, the causality and the underlying phenotype of the genetic alterations are not clearly defined. METHODS: This cross-sectional retrospective observational study includes 9 patients with Charcot-Marie-Tooth disease (CMT) with DRP2 germline variants evaluated at 6 centers throughout Spain. RESULTS: We identified 7 Spanish families with 4 different DRP2 likely pathogenic germline variants. In agreement with an X-linked inheritance, men harboring hemizygous DRP2 variants presented with an intermediate form of CMT, whereas heterozygous women were asymptomatic. Symptom onset was variable (36.6 ± 16 years), with lower limb weakness and multimodal sensory loss producing a mild-to-moderate functional impairment. Nerve echography revealed an increase in the cross-sectional area of nerve roots and proximal nerves. Lower limb muscle magnetic resonance imaging confirmed the presence of a length-dependent fatty infiltration. Immunostaining in intradermal nerve fibers demonstrated the absence of DRP2 and electron microscopy revealed abnormal myelin thickness that was also detectable in the sural nerve sections. DISCUSSION: Our findings support the causality of DRP2 pathogenic germline variants in CMT and further define the phenotype as a late-onset sensory and motor length-dependent neuropathy, with intermediate velocities and thickening of proximal nerve segments.


Assuntos
Doença de Charcot-Marie-Tooth , Mutação em Linhagem Germinativa , Feminino , Humanos , Masculino , Doença de Charcot-Marie-Tooth/genética , Doença de Charcot-Marie-Tooth/patologia , Bainha de Mielina/patologia , Nervos Periféricos/diagnóstico por imagem , Fenótipo , Estudos Transversais , Estudos Retrospectivos , Linhagem , Adulto Jovem , Pessoa de Meia-Idade , Idoso
17.
Mult Scler ; 19(9): 1175-81, 2013 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-23319072

RESUMO

BACKGROUND: Investigation of atrophy data from a pivotal natalizumab trial has demonstrated an increased rate of volume loss, compared to placebo, after the first year of therapy. It was considered to be probably due to a pseudoatrophy effect. OBJECTIVE: To assess grey and white matter volume changes and their relation to global brain volume changes and to baseline inflammation, for patients under natalizumab therapy. METHODS: We selected 45 patients on natalizumab therapy for at least 24 months, with magnetic resonance imaging (MRI) scans at baseline, 12 and 24 months. We calculated the percentage brain volume change (PBVC) for the first and second year, using SIENA software. Grey and white matter fractions (GMF and WMF, respectively) for the first year were calculated with SPM5, using lesion masks. After quality checks, six patients were excluded. We studied the predictive variables of change in brain volumes. RESULTS: The PBVC decrease was faster during the first year (-1.10% ± 1.43%), as compared to the second (-0.51% ± 0.96%) (p = 0.037). These differences were more marked in patients with baseline gadolinium-enhancing lesions (p = 0.005). Mean GMF and WMF changes during the first year of treatment were +1.15% (n.s.) and -1.72% (p = 0.017), respectively. The presence of active lesions at baseline MRI predicted PBVC (p = 0.022) and WMF change (p = 0.026) during the first year of treatment, after adjusting for age and corticosteroid treatment. No predictors were found for GMF volume changes. CONCLUSION: Early brain volume loss during natalizumab therapy is mainly due to WMF volume loss and it is related to the inflammatory activity present at the onset of therapy. We found that the pseudoatrophy effect is mostly due to white matter volume changes.


Assuntos
Anticorpos Monoclonais Humanizados/efeitos adversos , Encéfalo/patologia , Diagnóstico Diferencial , Esclerose Múltipla Recidivante-Remitente/tratamento farmacológico , Esclerose Múltipla Recidivante-Remitente/patologia , Fibras Nervosas Mielinizadas/patologia , Adulto , Atrofia , Feminino , Humanos , Interpretação de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Masculino , Natalizumab
18.
J Neurol ; 270(2): 1141-1146, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36175672

RESUMO

BACKGROUND: Functional Neurological Disorders (FND) are common in clinical practice. It is recognized that FND may present at onset or during the course of other neurological diseases (functional comorbidity). CASES: We report a clinical series of three patients who initially presented positive signs of a functional movement disorder (FMD) and were later diagnosed with a Creutzfeldt-Jakob disease (CJD). All patients presented with unilateral functional tremor, two patients also had functional limb weakness. All patients progressed to an asymmetric corticobasal syndrome, fulfilling clinical criteria of CJD. They had a rapid progression and died within 2-3 months. CONCLUSIONS: FND may be the initial clinical presentation of neurodegenerative diseases reflecting a dysfunction across brain circuits that are involved in the pathophysiology of FND. A positive diagnosis of FND is essential as it is an adequate examination and a close follow-up of these patients in neurology clinics.


Assuntos
Síndrome de Creutzfeldt-Jakob , Humanos , Síndrome de Creutzfeldt-Jakob/diagnóstico , Síndrome de Creutzfeldt-Jakob/diagnóstico por imagem , Encéfalo/diagnóstico por imagem , Diagnóstico Diferencial
19.
Neurol Genet ; 6(1): e381, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32042910

RESUMO

OBJECTIVE: To describe the clinical and functional consequences of 1 novel and 1 previously reported truncating MT-ATP6 mutation. METHODS: Three unrelated probands with mitochondrial encephalomyopathy harboring truncating MT-ATP6 mutations are reported. Transmitochondrial cybrid cell studies were used to confirm pathogenicity of 1 novel variant, and the effects of all 3 mutations on ATPase 6 and complex V structure and function were investigated. RESULTS: Patient 1 presented with adult-onset cerebellar ataxia, chronic kidney disease, and diabetes, whereas patient 2 had myoclonic epilepsy and cerebellar ataxia; both harbored the novel m.8782G>A; p.(Gly86*) mutation. Patient 3 exhibited cognitive decline, with posterior white matter abnormalities on brain MRI, and severely impaired renal function requiring transplantation. The m.8618dup; p.(Thr33Hisfs*32) mutation, previously associated with neurogenic muscle weakness, ataxia, and retinitis pigmentosa, was identified. All 3 probands demonstrated a broad range of heteroplasmy across different tissue types. Blue-native gel electrophoresis of cultured fibroblasts and skeletal muscle tissue confirmed multiple bands, suggestive of impaired complex V assembly. Microscale oxygraphy showed reduced basal respiration and adenosine triphosphate synthesis, while reactive oxygen species generation was increased. Transmitochondrial cybrid cell lines studies confirmed the deleterious effects of the novel m.8782 G>A; p.(Gly86*) mutation. CONCLUSIONS: We expand the clinical and molecular spectrum of MT-ATP6-related mitochondrial disorders to include leukodystrophy, renal disease, and myoclonic epilepsy with cerebellar ataxia. Truncating MT-ATP6 mutations may exhibit highly variable mutant levels across different tissue types, an important consideration during genetic counseling.

20.
Neurol Genet ; 5(2): e322, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31119193

RESUMO

OBJECTIVE: To characterize the phenotype in individuals with OPA3-related autosomal dominant optic atrophy and cataract (ADOAC) and peripheral neuropathy (PN). METHODS: Two probands with multiple affected relatives and one sporadic case were referred for evaluation of a PN. Their phenotype was determined by clinical ± neurophysiological assessment. Neuropathologic examination of sural nerve and skeletal muscle, and ultrastructural analysis of mitochondria in fibroblasts were performed in one case. Exome sequencing was performed in the probands. RESULTS: The main clinical features in one family (n = 7 affected individuals) and one sporadic case were early-onset cataracts (n = 7), symptoms of gastrointestinal dysmotility (n = 8), and possible/confirmed PN (n = 7). Impaired vision was an early-onset feature in another family (n = 4 affected individuals), in which 3 members had symptoms of gastrointestinal dysmotility and 2 developed PN and cataracts. The less common features among all individuals included symptoms/signs of autonomic dysfunction (n = 3), hearing loss (n = 3), and recurrent pancreatitis (n = 1). In 5 individuals, the neuropathy was axonal and clinically asymptomatic (n = 1), sensory-predominant (n = 2), or motor and sensory (n = 2). In one patient, nerve biopsy revealed a loss of large and small myelinated fibers. In fibroblasts, mitochondria were frequently enlarged with slightly fragmented cristae. The exome sequencing identified OPA3 variants in all probands: a novel variant (c.23T>C) and the known mutation (c.313C>G) in OPA3. CONCLUSIONS: A syndromic form of ADOAC (ADOAC+), in which axonal neuropathy may be a major feature, is described. OPA3 mutations should be included in the differential diagnosis of complex inherited PN, even in the absence of clinically apparent optic atrophy.

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