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Many genes have been linked to amyotrophic lateral sclerosis (ALS), including never in mitosis A (NIMA)-related kinase 1 (NEK1), a serine/threonine kinase that plays a key role in several cellular functions, such as DNA damage response and cell cycle regulation. Whole-exome sequencing studies have shown that NEK1 mutations are associated with an increased risk for ALS, where a significant enrichment of NEK1 loss-of-function (LOF) variants were found in individuals with ALS compared to controls. In particular, the p.Arg261His missense variant was associated with significantly increased disease susceptibility. This case series aims to understand the neuropathological phenotypes resulting from NEK1 mutations in ALS. We examined a cohort of three Scottish patients with a mutation in the NEK1 gene and evaluated the distribution and cellular expression of NEK1, as well as the abundance of phosphorylated TDP-43 (pTDP-43) aggregates, in the motor cortex compared to age- and sex-matched control tissue. We show pathological, cytoplasmic TDP-43 aggregates in all three NEK1-ALS cases. NEK1 protein staining revealed no immunoreactivity in two of the NEK1-ALS cases, indicating a LOF and corresponding to a reduction in NEK1 mRNA as detected by in situ hybridisation. However, the p.Arg261His missense mutation resulted in an increase in NEK1 mRNA molecules and abundant NEK1-positive cytoplasmic aggregates, with the same morphologic appearance, and within the same cells as co-occurring TDP-43 aggregates. Here we show the first neuropathological assessment of a series of ALS cases carrying mutations in the NEK1 gene. Specifically, we show that TDP-43 pathology is present in these cases and that potential NEK1 LOF can either be mediated through loss of NEK1 translation or through aggregation of NEK1 protein as in the case with p.Arg261His mutation, a potential novel pathological feature of NEK1-ALS.
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BACKGROUND: Using the Clinical Audit Research and Evaluation of Motor Neuron Disease (CARE-MND) database and the Scottish Regenerative Neurology Tissue Bank, we aimed to outline the genetic epidemiology and phenotypes of an incident cohort of people with MND (pwMND) to gain a realistic impression of the genetic landscape and genotype-phenotype associations. METHODS: Phenotypic markers were identified from the CARE-MND platform. Sequence analysis of 48 genes was undertaken. Variants were classified using a structured evidence-based approach. Samples were also tested for C9orf72 hexanucleotide expansions using repeat-prime PCR methodology. RESULTS: 339 pwMND donated a DNA sample: 44 (13.0%) fulfilled criteria for having a pathogenic variant/repeat expansion, 53.5% of those with a family history of MND and 9.3% of those without. The majority (30 (8.8%)) had a pathogenic C9orf72 repeat expansion, including two with intermediate expansions. Having a C9orf72 expansion was associated with a significantly lower Edinburgh Cognitive and Behavioural ALS Screen ALS-Specific score (p = 0.0005). The known pathogenic SOD1 variant p.(Ile114Thr), frequently observed in the Scottish population, was detected in 9 (2.7%) of total cases but in 17.9% of familial cases. Rare variants were detected in FUS and NEK1. One individual carried both a C9orf72 expansion and SOD1 variant. CONCLUSIONS: Our results provide an accurate summary of MND demographics and genetic epidemiology. We recommend early genetic testing of people with cognitive impairment to ensure that C9orf72 carriers are given the best opportunity for informed treatment planning. Scotland is enriched for the SOD1 p.(Ile114Thr) variant and this has significant implications with regards to future genetically-targeted treatments.
Assuntos
Proteína C9orf72 , Doença dos Neurônios Motores , Fenótipo , Humanos , Escócia/epidemiologia , Doença dos Neurônios Motores/genética , Doença dos Neurônios Motores/epidemiologia , Masculino , Feminino , Pessoa de Meia-Idade , Idoso , Proteína C9orf72/genética , Genótipo , Adulto , Expansão das Repetições de DNA/genética , Estudos de Coortes , Idoso de 80 Anos ou mais , Superóxido Dismutase-1/genéticaRESUMO
BACKGROUND: We investigated the phenotypes and genotypes of a cohort of 'long-surviving' individuals with motor neuron disease (MND) to identify potential targets for prognostication. METHODS: Patients were recruited via the Clinical Audit Research and Evaluation for MND (CARE-MND) platform, which hosts the Scottish MND Register. Long survival was defined as > 8 years from diagnosis. 11 phenotypic variables were analysed. Whole genome sequencing (WGS) was performed and variants within 49 MND-associated genes examined. Each individual was screened for C9orf72 repeat expansions. Data from ancestry-matched Scottish populations (the Lothian Birth Cohorts) were used as controls. RESULTS: 58 long survivors were identified. Median survival from diagnosis was 15.5 years. Long survivors were significantly younger at onset and diagnosis than incident patients and had a significantly longer diagnostic delay. 42% had the MND subtype of primary lateral sclerosis (PLS). WGS was performed in 46 individuals: 14 (30.4%) had a potentially pathogenic variant. 4 carried the known SOD1 p.(Ile114Thr) variant. Significant variants in FIG4, hnRNPA2B1, SETX, SQSTM1, TAF15, and VAPB were detected. 2 individuals had a variant in the SPAST gene suggesting phenotypic overlap with hereditary spastic paraplegia (HSP). No long survivors had pathogenic C9orf72 repeat expansions. CONCLUSIONS: Long survivors are characterised by younger age at onset, increased prevalence of PLS and longer diagnostic delay. Genetic analysis in this cohort has improved our understanding of the phenotypes associated with the SOD1 variant p.(Ile114Thr). Our findings confirm that pathogenic expansion of C9orf72 is likely a poor prognostic marker. Genetic screening using targeted MND and/or HSP panels should be considered in those with long survival, or early-onset slowly progressive disease, to improve diagnostic accuracy and aid prognostication.
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Esclerose Lateral Amiotrófica , Doença dos Neurônios Motores , Paraplegia Espástica Hereditária , Humanos , Proteína C9orf72/genética , Diagnóstico Tardio , Superóxido Dismutase-1/genética , Doença dos Neurônios Motores/epidemiologia , Doença dos Neurônios Motores/genética , Genótipo , Fenótipo , Paraplegia Espástica Hereditária/genética , Esclerose Lateral Amiotrófica/genética , Espastina/genética , DNA Helicases/genética , RNA Helicases/genética , Enzimas Multifuncionais/genéticaRESUMO
OBJECTIVES: Scotland benefits from an integrated national healthcare team for motor neurone disease (MND) and a tradition of rich clinical data capture using the Scottish MND Register (launched in 1989; one of the first national registers). The Scottish register was re-launched in 2015 as Clinical Audit Research and Evaluation of MND (CARE-MND), an electronic platform for prospective, population-based research. We aimed to determine if incidence of MND is changing over time. METHODS: Capture-recapture methods determined the incidence of MND in 2015-2016. Incidence rates for 2015-2016 and 1989-1998 were direct age and sex standardised to allow time-period comparison. Phenotypic characteristics and socioeconomic status of the cohort are described. RESULTS: Coverage of the CARE-MND platform was 99%. Crude incidence in the 2015-2017 period was 3.83/100,000 person-years (95% CI 3.53-4.14). Direct age-standardised incidence in 2015 was 3.42/100,000 (95% CI 2.99-3.91); in 2016, it was 2.89/100,000 (95% CI 2.50-3.34). The 1989-1998 direct standardised annual incidence estimate was 2.32/100,000 (95% CI 2.26-2.37). 2015-2016 standardised incidence was 66.9% higher than Northern European estimates. Socioeconomic status was not associated with MND. CONCLUSIONS: Our data show a changing landscape of MND in Scotland, with a rise in incidence by 36.0% over a 25-year period. This is likely attributable to ascertainment in the context of improved neurological services in Scotland. Our data suggest that CARE-MND is a reliable national resource and findings can be extrapolated to the other Northern European populations.
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Doença dos Neurônios Motores/epidemiologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Incidência , Masculino , Pessoa de Meia-Idade , Prevalência , Estudos Prospectivos , Sistema de Registros , Escócia/epidemiologia , Fatores de Tempo , Adulto JovemRESUMO
Genetic understanding of motor neuron disease (MND) has evolved greatly in the past 10 years, including the recent identification of association between MND and variants in TBK1 and NEK1. Our aim was to determine the frequency of pathogenic variants in known MND genes and to assess whether variants in TBK1 and NEK1 contribute to the burden of MND in the Scottish population. SOD1, TARDBP, OPTN, TBK1, and NEK1 were sequenced in 441 cases and 400 controls. In addition to 44 cases known to carry a C9orf72 hexanucleotide repeat expansion, we identified 31 cases and 2 controls that carried a loss-of-function or pathogenic variant. Loss-of-function variants were found in TBK1 in 3 cases and no controls and, separately, in NEK1 in 3 cases and no controls. This study provides an accurate description of the genetic epidemiology of MND in Scotland and provides support for the contribution of both TBK1 and NEK1 to MND susceptibility in the Scottish population.