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1.
Eur J Hum Genet ; 32(7): 770-778, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38433266

RESUMO

Huntington disease (HD) is a neurodegenerative disorder caused by ≥36 CAGs in the HTT gene. Intermediate alleles (IAs) (27-35 CAGs) are not considered HD-causing, but their potential association with neurocognitive symptoms remains controversial. As HTT somatic CAG expansion influences HD onset, we hypothesised that IAs are somatically unstable, and that somatic CAG expansion may drive phenotypic presentation in some IA carriers. We quantified HTT somatic CAG expansions by MiSeq sequencing in the blood DNA of 164 HD subjects and 191 IA (symptomatic and control) carriers, and in the brain DNA of a symptomatic 33 CAG carrier. We also performed genotype-phenotype analysis. The phenotype of symptomatic IA carriers was characterised by motor (85%), cognitive (27%) and/or behavioural (29%) signs, with a late (58.7 ± 18.6 years), but not CAG-dependent, age at onset. IAs displayed somatic expansion that were CAG and age-dependent in blood DNA, with 0.4% and 0.01% of DNA molecules expanding by CAG and year, respectively. Somatic expansions of +1 and +2 CAGs were detected in the brain of the individual with 33 CAGs, with the highest expansion frequency in the putamen (10.3%) and the lowest in the cerebellum (4.8%). Somatic expansion in blood DNA was not different in symptomatic vs. control IA carriers. In conclusion, we show that HTT IAs are somatically unstable, but we found no association with HD-like phenotypes. It is plausible, however, that some IAs, close to the HD pathological threshold and with a predisposing genetic background, could manifest with neurocognitive symptoms.


Assuntos
Alelos , Proteína Huntingtina , Doença de Huntington , Fenótipo , Expansão das Repetições de Trinucleotídeos , Humanos , Doença de Huntington/genética , Doença de Huntington/patologia , Proteína Huntingtina/genética , Pessoa de Meia-Idade , Masculino , Feminino , Adulto , Idoso , Heterozigoto , Encéfalo/patologia , Encéfalo/metabolismo
2.
Neuromuscul Disord ; 33(8): 660-669, 2023 08.
Artigo em Inglês | MEDLINE | ID: mdl-37419717

RESUMO

Myotonic dystrophy type 1 is characterized by neuromuscular degeneration. Our objective was to compare change in white matter microstructure (fractional anisotropy, radial and axial diffusivity), and functional/clinical measures. Participants underwent yearly neuroimaging and neurocognitive assessments over three-years. Assessments encompassed full-scale intelligence, memory, language, visuospatial skills, attention, processing speed, and executive function, as well as clinical symptoms of muscle/motor function, apathy, and hypersomnolence. Mixed effects models were used to examine differences. 69 healthy adults (66.2% women) and 41 DM1 patients (70.7% women) provided 156 and 90 observations, respectively. There was a group by elapsed time interaction for cerebral white matter, where DM1 patients exhibited declines in white matter (all p<0.05). Likewise, DM1 patients either declined (motor), improved more slowly (intelligence), or remained stable (executive function) for functional outcomes. White matter was associated with functional performance; intelligence was predicted by axial (r = 0.832; p<0.01) and radial diffusivity (r = 0.291, p<0.05), and executive function was associated with anisotropy (r = 0.416, p<0.001), and diffusivity (axial: r = 0.237, p = 0.05 and radial: r = 0.300, p<0.05). Indices of white matter health are sensitive to progression in DM1. These results are important for clinical trial design, which utilize short intervals to establish treatment efficacy.


Assuntos
Distrofia Miotônica , Substância Branca , Humanos , Adulto , Feminino , Masculino , Imagem de Tensor de Difusão , Substância Branca/diagnóstico por imagem , Distrofia Miotônica/complicações , Função Executiva , Anisotropia , Encéfalo/diagnóstico por imagem
3.
Neuromuscul Disord ; 32(5): 377-389, 2022 05.
Artigo em Inglês | MEDLINE | ID: mdl-35361525

RESUMO

Abnormalities of sleep are common in myotonic dystrophy type 1 (DM1), but few previous studies have combined polysomnography with detailed clinical measures and brain imaging. In the present study, domiciliary polysomnography, symptom questionnaires and cognitive evaluation were undertaken in 39 DM1-affected individuals. Structural brain MRI was completed in those without contra-indication (n = 32). Polysomnograms were adequate for analysis in 36 participants. Sleep efficiency was reduced, and sleep architecture altered in keeping with previous studies. Twenty participants (56%) had moderate or severe sleep-disordered breathing (apnoea-hypopnoea index [AHI] ≥ 15). In linear modelling, apnoeas were positively associated with increasing age and male sex. AHI ≥ 15 was further associated with greater daytime pCO2 and self-reported physical impairment, somnolence and fatigue. Percentage REM sleep was inversely associated with cerebral grey matter volume, stage 1 sleep was positively associated with occipital lobe volume and stage 2 sleep with amygdala volume. Hippocampus volume was positively correlated with self-reported fatigue and somnolence. Linear relationships were also observed between measures of sleep architecture and cognitive performance. Findings broadly support the hypothesis that changes in sleep architecture and excessive somnolence in DM1 reflect the primary disease process in the central nervous system.


Assuntos
Distúrbios do Sono por Sonolência Excessiva , Distrofia Miotônica , Distúrbios do Sono por Sonolência Excessiva/complicações , Distúrbios do Sono por Sonolência Excessiva/etiologia , Fadiga/complicações , Fadiga/etiologia , Humanos , Masculino , Distrofia Miotônica/complicações , Distrofia Miotônica/diagnóstico por imagem , Sono , Sonolência
4.
Front Neurol ; 12: 700796, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34276551

RESUMO

Myotonic dystrophy type 1 is the most common form of muscular dystrophy in adults, and is primarily characterized by muscle weakness and myotonia, yet some of the most disabling symptoms of the disease are cognitive and behavioral. Here we evaluated several of these non-motor symptoms from a cross-sectional time-point in one of the largest longitudinal studies to date, including full-scale intelligence quotient, depression, anxiety, apathy, sleep, and cerebral white matter fractional anisotropy in a group of 39 adult-onset myotonic dystrophy type 1 participants (27 female) compared to 79 unaffected control participants (46 female). We show that intelligence quotient was significantly associated with depression (P < 0.0001) and anxiety (P = 0.018), but not apathy (P < 0.058) or hypersomnolence (P = 0.266) in the DM1 group. When controlling for intelligence quotient, cerebral white matter fractional anisotropy was significantly associated with apathy (P = 0.042) and hypersomnolence (P = 0.034), but not depression (P = 0.679) or anxiety (P = 0.731) in the myotonic dystrophy type 1 group. Finally, we found that disease duration was significantly associated with apathy (P < 0.0001), hypersomnolence (P < 0.001), IQ (P = 0.038), and cerebral white matter fractional anisotropy (P < 0.001), but not depression (P = 0.271) or anxiety (P = 0.508). Our results support the hypothesis that cognitive deficits, hypersomnolence, and apathy, are due to the underlying neuropathology of myotonic dystrophy type 1, as measured by cerebral white matter fractional anisotropy and disease duration. Whereas elevated symptoms of depression and anxiety in myotonic dystrophy type 1 are secondary to the physical symptoms and the emotional stress of coping with a chronic and debilitating disease. Results from this work contribute to a better understanding of disease neuropathology and represent important therapeutic targets for clinical trials.

5.
Neurol Genet ; 7(2): e577, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33912661

RESUMO

OBJECTIVE: The goal of the study was to identify brain and functional features associated with premanifest phases of adult-onset myotonic dystrophy type 1 (i.e., PreDM1). METHODS: This cross-sectional study included 68 healthy adults (mean age = 43.4 years, SD = 12.9), 13 individuals with PreDM1 (mean age: 47.4 years, SD = 16.3), and 37 individuals with manifest DM1 (mean age = 45.2 years, SD = 9.3). The primary outcome measures included fractional anisotropy (FA), motor measures (Muscle Impairment Rating Scale, Grooved Pegboard, Finger-Tapping Test, and grip force), general cognitive abilities (Wechsler Adult Intelligence Scales), sleep quality (Scales for Outcomes in Parkinson's Disease-Sleep), and apathy (Apathy Evaluation Scale). RESULTS: Individuals with PreDM1 exhibited an intermediate level of white matter FA abnormality, where whole-brain FA was lower relative to healthy controls (difference of the estimated marginal mean [EMMdifference] = 0.02, 95% confidence interval (CI) 0.01-0.03, p < 0.001), but the PreDM1 group had significantly higher FA than did individuals with manifest DM1 (EMMdifference = 0.02, 95% CI 0.009-0.03, p < 0.001). Individuals with PreDM1 exhibited reduced performance on the finger-tapping task relative to control peers (EMMdifference = 5.70, 95% CI 0.51-11.00, p = 0.03), but performance of the PreDM1 group was better than that of the manifest DM1 group (EMMdifference = 5.60, 95% CI 0.11-11.00, p = 0.05). Hypersomnolence in PreDM1 was intermediate between controls (EMMdifference = -1.70, 95% CI -3.10-0.35, p = 0.01) and manifest DM1 (EMMdifference = -2.10, 95% CI -3.50-0.60, p = 0.006). CONCLUSIONS: Our findings highlight key CNS and functional deficits associated with PreDM1, offering insight in early disease course.

6.
Neurol Genet ; 7(2): e572, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33884298

RESUMO

OBJECTIVE: To assess the association between variant repeat (VR) interruptions in patients with myotonic dystrophy type 1 (DM1) and clinical symptoms and outcome measures after cognitive behavioral therapy (CBT) intervention. METHODS: Adult patients with DM1 were recruited within the OPTIMISTIC trial (NCT02118779). Disease-related history, current clinical symptoms and comorbidities, functional assessments, and disease- and health-related questionnaires were obtained at baseline and after 5 and 10 months. After genetic analysis, we assessed the association between the presence of VR interruptions and clinical symptoms' long-term outcomes and compared the effects of CBT in patients with and without VR interruptions. Core trial outcome measures analyzed were: 6-minute walking test, DM1-Activ-C, Checklist Individual Strength Fatigue Score, Myotonic Dystrophy Health Index, McGill-Pain questionnaire, and Beck Depression inventory-fast screen. Blood samples for DNA testing were obtained at the baseline visit for determining CTG length and detection of VR interruptions. RESULTS: VR interruptions were detectable in 21/250 patients (8.4%)-12 were assigned to the standard-of-care group (control group) and 9 to the CBT group. Patients with VR interruptions were significantly older when the first medical problem occurred and had a significantly shorter disease duration at baseline. We found a tendency toward a milder disease severity in patients with VR interruptions, especially in ventilation status, mobility, and cardiac symptoms. Changes in clinical outcome measures after CBT were not associated with the presence of VR interruptions. CONCLUSIONS: The presence of VR interruptions is associated with a later onset of the disease and a milder phenotype. However, based on the OPTIMISTIC trial data, the presence of VR interruptions was not associated with significant changes on outcome measures after CBT intervention. TRIAL REGISTRATION INFORMATION: ClinicalTrials.gov NCT02118779.

7.
Sci Rep ; 11(1): 4886, 2021 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-33649422

RESUMO

Deficits in white matter (WM) integrity and motor symptoms are among the most robust and reproducible features of myotonic dystrophy type 1 (DM1). In the present study, we investigate whether WM integrity, obtained from diffusion-weighted MRI, corresponds to quantifiable motor outcomes (e.g., fine motor skills and grip strength) and patient-reported, subjective motor deficits. Critically, we explore these relationships in the context of other potentially causative variables, including: disease duration, elapsed time since motor symptom onset; and genetic burden, the number of excessive CTG repeats causing DM1. We found that fractional anisotropy (a measure of WM integrity) throughout the cerebrum was the strongest predictor of grip strength independently of disease duration and genetic burden, while radial diffusivity predicted fine motor skill (peg board performance). Axial diffusivity did not predict motor outcomes. Our results are consistent with the notion that systemic degradation of WM in DM1 mediates the relationship between DM1 progression and genetic burden with motor outcomes of the disease. Our results suggest that tracking changes in WM integrity over time may be a valuable biomarker for tracking therapeutic interventions, such as future gene therapies, for DM1.


Assuntos
Distrofia Miotônica , Substância Branca/patologia , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Distrofia Miotônica/genética , Distrofia Miotônica/patologia
8.
Neuromuscul Disord ; 31(3): 232-238, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33546847

RESUMO

We report the case of a male patient presenting in his 50s with ptosis, facial and distal limb muscle weakness, clinical and electrical myotonia, and a prior history of cataract extraction. He had a dominant family history in keeping with a similar phenotype. Myotonic dystrophy type 1 was clinically suspected. Triplet-primed polymerase chain reaction in a diagnostic laboratory did not identify a typical CTG repeat expansion on two separate blood samples. However, subsequent genetic testing on a research basis identified a heterozygous repeat expansion containing CCG variant repeats. Our case highlights the point that variant repeats are not detectable on triplet-primed polymerase chain reaction and result in a milder phenotype of myotonic dystrophy. It is crucial to maintain a high clinical index of suspicion of this common neuromuscular condition.


Assuntos
Distrofia Miotônica/diagnóstico , Repetições de Trinucleotídeos , Alelos , Humanos , Masculino , Pessoa de Meia-Idade , Distrofia Miotônica/genética , Miotonina Proteína Quinase , Linhagem , Fenótipo , Reação em Cadeia da Polimerase , Expansão das Repetições de Trinucleotídeos
9.
J Huntingtons Dis ; 10(1): 53-74, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33579864

RESUMO

BACKGROUND: Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by the expansion of the HTT CAG repeat. Affected individuals inherit ≥36 repeats and longer alleles cause earlier onset, greater disease severity and faster disease progression. The HTT CAG repeat is genetically unstable in the soma in a process that preferentially generates somatic expansions, the proportion of which is associated with disease onset, severity and progression. Somatic mosaicism of the HTT CAG repeat has traditionally been assessed by semi-quantitative PCR-electrophoresis approaches that have limitations (e.g., no information about sequence variants). Genotyping-by-sequencing could allow for some of these limitations to be overcome. OBJECTIVE: To investigate the utility of PCR sequencing to genotype large (>50 CAGs) HD alleles and to quantify the associated somatic mosaicism. METHODS: We have applied MiSeq and PacBio sequencing to PCR products of the HTT CAG repeat in transgenic R6/2 mice carrying ∼55, ∼110, ∼255 and ∼470 CAGs. For each of these alleles, we compared the repeat length distributions generated for different tissues at two ages. RESULTS: We were able to sequence the CAG repeat full length in all samples. However, the repeat length distributions for samples with ∼470 CAGs were biased towards shorter repeat lengths. CONCLUSION: PCR sequencing can be used to sequence all the HD alleles considered, but this approach cannot be used to estimate modal allele size or quantify somatic expansions for alleles ⪢250 CAGs. We review the limitations of PCR sequencing and alternative approaches that may allow the quantification of somatic contractions and very large somatic expansions.


Assuntos
Proteína Huntingtina/genética , Doença de Huntington/genética , Mosaicismo , Reação em Cadeia da Polimerase/normas , Análise de Sequência de DNA/normas , Expansão das Repetições de Trinucleotídeos/genética , Animais , Camundongos , Camundongos Transgênicos
10.
Front Neurol ; 12: 791065, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-35126292

RESUMO

INTRODUCTION: The present study had four aims. First, neuronal injury markers, including neurofilament light (NF-L), total tau, glial fibrillary acidic protein (GFAP) and ubiquitin C-terminal hydrolase (UCH-L1), were compared between individuals with and without adult-onset myotonic dystrophy type 1 (DM1). Second, the impact of age and CTG repeat on brain injury markers was evaluated. Third, change in brain injury markers across the study period was quantified. Fourth, associations between brain injury markers and cerebral white matter (WM) fractional anisotropy (FA) were identified. METHODS: Yearly assessments, encompassing blood draws and diffusion tensor imaging on a 3T scanner, were conducted on three occasions. Neuronal injury markers were quantified using single molecule array (Simoa). RESULTS: The sample included 53 patients and 70 controls. NF-L was higher in DM1 patients than controls, with individuals in the premanifest phases of DM1 (PreDM1) exhibiting intermediate levels ( χ ( 2 ) 2 = 38.142, P < 0.001). Total tau was lower in DM1 patients than controls (Estimate = -0.62, 95% confidence interval [CI] -0.95: -0.28, P < 0.001), while GFAP was elevated in PreDM1 only (Estimate = 30.37, 95% CI 10.56:50.19, P = 0.003). Plasma concentrations of UCH-L1 did not differ between groups. The age by CTG interaction predicted NF-L: patients with higher estimated progenitor allelege length (ePAL) had higher NF-L at a younger age, relative to patients with lower CTG repeat; however, the latter exhibited faster age-related change (Estimate = -0.0021, 95% CI -0.0042: -0.0001, P = 0.045). None of the markers changed substantially over the study period. Finally, cerebral WM FA was significantly associated with NF-L (Estimate = -42.86, 95% CI -82.70: -3.02, P = 0.035). INTERPRETATION: While NF-L appears sensitive to disease onset and severity, its utility as a marker of progression remains to be determined. The tau assay may have low sensitivity to tau pathology associated with DM1.

11.
Genes (Basel) ; 11(11)2020 11 07.
Artigo em Inglês | MEDLINE | ID: mdl-33171734

RESUMO

Myotonic Dystrophy type 1 (DM1) is characterized by a high genetic and clinical variability. Determination of the genetic variability in DM1 might help to determine whether there is an association between CTG (Cytosine-Thymine-Guanine) expansion and the clinical manifestations of this condition. We studied the variability of the CTG expansion (progenitor, mode, and longest allele, respectively, and genetic instability) in three tissues (blood, muscle, and tissue) from eight patients with DM1. We also studied the association of genetic data with the patients' clinical characteristics. Although genetic instability was confirmed in all the tissues that we studied, our results suggest that CTG expansion is larger in muscle and skin cells compared with peripheral blood leukocytes. While keeping in mind that more research is needed in larger cohorts, we have provided preliminary evidence suggesting that the estimated progenitor CTG size in muscle could be potentially used as an indicator of age of disease onset and muscle function impairment.


Assuntos
Distrofia Miotônica/genética , Expansão das Repetições de Trinucleotídeos/genética , Adolescente , Adulto , Alelos , Sangue/metabolismo , Citosina/metabolismo , Feminino , Variação Genética/genética , Guanina/metabolismo , Humanos , Masculino , Pessoa de Meia-Idade , Músculo Esquelético/metabolismo , Proteínas Serina-Treonina Quinases/genética , Pele/metabolismo , Timina/metabolismo , Expansão das Repetições de Trinucleotídeos/fisiologia
12.
Neurol Genet ; 6(5): e504, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32851192

RESUMO

OBJECTIVE: We tested the hypothesis that variant repeat interruptions (RIs) within the DMPK CTG repeat tract lead to milder symptoms compared with pure repeats (PRs) in myotonic dystrophy type 1 (DM1). METHODS: We evaluated motor, neurocognitive, and behavioral outcomes in a group of 6 participants with DM1 with RI compared with a case-matched sample of 12 participants with DM1 with PR and a case-matched sample of 12 unaffected healthy comparison participants (UA). RESULTS: In every measure, the RI participants were intermediate between UA and PR participants. For muscle strength, the RI group was significantly less impaired than the PR group. For measures of Full Scale IQ, depression, and sleepiness, all 3 groups were significantly different from each other with UA > RI > PR in order of impairment. The RI group was different from unaffected, but not significantly different from PR (UA > RI = PR) in apathy and working memory. Finally, in finger tapping and processing speed, RI did not differ from UA comparisons, but PR had significantly lower scores than the UA comparisons (UA = RI > PR). CONCLUSIONS: Our results support the notion that patients affected by DM1 with RI demonstrate a milder phenotype with the same pattern of deficits as those with PR indicating a similar disease process.

13.
Genes (Basel) ; 11(7)2020 07 07.
Artigo em Inglês | MEDLINE | ID: mdl-32645888

RESUMO

The number of cytosine-thymine-guanine (CTG) repeats ('CTG expansion size') in the 3'untranslated region (UTR) region of the dystrophia myotonica-protein kinase (DMPK) gene is a hallmark of myotonic dystrophy type 1 (DM1), which has been related to age of disease onset and clinical severity. However, accurate determination of CTG expansion size is challenging due to its characteristic instability. We compared five different approaches (heat pulse extension polymerase chain reaction [PCR], long PCR-Southern blot [with three different primers sets-1, 2 and 3] and small pool [SP]-PCR) to estimate CTG expansion size in the progenitor allele as well as the most abundant CTG expansion size, in 15 patients with DM1. Our results indicated variability between the methods (although we found no overall differences between long PCR 1 and 2 and SP-PCR, respectively). While keeping in mind the limited sample size of our patient cohort, SP-PCR appeared as the most suitable technique, with an inverse significant correlation found between CTG expansion size of the progenitor allele, as determined by this method, and age of disease onset (r = -0.734, p = 0.016). Yet, in light of the variability of the results obtained with the different methods, we propose that an international agreement is needed to determine which is the most suitable method for assessing CTG expansion size in DM1.


Assuntos
Testes Genéticos/métodos , Distrofia Miotônica/genética , Reação em Cadeia da Polimerase/métodos , Expansão das Repetições de Trinucleotídeos , Regiões 3' não Traduzidas , Idade de Início , Testes Genéticos/normas , Humanos , Distrofia Miotônica/diagnóstico , Miotonina Proteína Quinase/genética , Reação em Cadeia da Polimerase/normas , Padrões de Referência
14.
PLoS One ; 15(4): e0231000, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32287265

RESUMO

Myotonic dystrophy type 1 (DM1) is a rare genetic disorder, characterised by muscular dystrophy, myotonia, and other symptoms. DM1 is caused by the expansion of a CTG repeat in the 3'-untranslated region of DMPK. Longer CTG expansions are associated with greater symptom severity and earlier age at onset. The primary mechanism of pathogenesis is thought to be mediated by a gain of function of the CUG-containing RNA, that leads to trans-dysregulation of RNA metabolism of many other genes. Specifically, the alternative splicing (AS) and alternative polyadenylation (APA) of many genes is known to be disrupted. In the context of clinical trials of emerging DM1 treatments, it is important to be able to objectively quantify treatment efficacy at the level of molecular biomarkers. We show how previously described candidate mRNA biomarkers can be used to model an effective reduction in CTG length, using modern high-dimensional statistics (machine learning), and a blood and muscle mRNA microarray dataset. We show how this model could be used to detect treatment effects in the context of a clinical trial.


Assuntos
Distrofia Miotônica/genética , Distrofia Miotônica/terapia , RNA Mensageiro/genética , Processamento Alternativo , Bioestatística , Ensaios Clínicos como Assunto/métodos , Ensaios Clínicos como Assunto/estatística & dados numéricos , Bases de Dados de Ácidos Nucleicos/estatística & dados numéricos , Marcadores Genéticos , Humanos , Análise dos Mínimos Quadrados , Aprendizado de Máquina , Modelos Genéticos , Músculos/metabolismo , Distrofia Miotônica/metabolismo , Miotonina Proteína Quinase/genética , Análise de Sequência com Séries de Oligonucleotídeos/estatística & dados numéricos , Poliadenilação , RNA Mensageiro/metabolismo , Resultado do Tratamento , Expansão das Repetições de Trinucleotídeos
15.
Hum Mutat ; 41(2): 420-431, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31608518

RESUMO

Carriage of interruptions in CTG repeats of the myotonic dystrophy protein kinase gene has been associated with a broad spectrum of myotonic dystrophy type 1 (DM1) phenotypes, mostly mild. However, the data available on interrupted DM1 patients and their phenotype are scarce. We studied 49 Spanish DM1 patients, whose clinical phenotype was evaluated in depth. Blood DNA was obtained and analyzed through triplet-primed polymerase chain reaction (PCR), long PCR-Southern blot, small pool PCR, AciI digestion, and sequencing. Five patients of our registry (10%), belonging to the same family, carried CCG interruptions at the 3'-end of the CTG expansion. Some of them presented atypical traits such as very late onset of symptoms ( > 50 years) and a severe axial and proximal weakness requiring walking assistance. They also showed classic DM1 symptoms including cardiac and respiratory dysfunction, which were severe in some of them. Sizes and interrupted allele patterns were determined, and we found a contraction and an expansion in two intergenerational transmissions. Our study contributes to the observation that DM1 patients carrying interruptions present with atypical clinical features that can make DM1 diagnosis difficult, with a later than expected age of onset and a previously unreported aging-related severe disease manifestation.


Assuntos
Estudos de Associação Genética , Predisposição Genética para Doença , Distrofia Miotônica/diagnóstico , Distrofia Miotônica/genética , Miotonina Proteína Quinase/genética , Fenótipo , Expansão das Repetições de Trinucleotídeos , Alelos , Feminino , Humanos , Masculino , Linhagem , Reação em Cadeia da Polimerase , Análise de Sequência de DNA
16.
EBioMedicine ; 48: 568-580, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31607598

RESUMO

BACKGROUND: Huntington disease (HD) is caused by an unstable CAG/CAA repeat expansion encoding a toxic polyglutamine tract. Here, we tested the hypotheses that HD outcomes are impacted by somatic expansion of, and polymorphisms within, the HTT CAG/CAA glutamine-encoding repeat, and DNA repair genes. METHODS: The sequence of the glutamine-encoding repeat and the proportion of somatic CAG expansions in blood DNA from participants inheriting 40 to 50 CAG repeats within the TRACK-HD and Enroll-HD cohorts were determined using high-throughput ultra-deep-sequencing. Candidate gene polymorphisms were genotyped using kompetitive allele-specific PCR (KASP). Genotypic associations were assessed using time-to-event and regression analyses. FINDINGS: Using data from 203 TRACK-HD and 531 Enroll-HD participants, we show that individuals with higher blood DNA somatic CAG repeat expansion scores have worse HD outcomes: a one-unit increase in somatic expansion score was associated with a Cox hazard ratio for motor onset of 3·05 (95% CI = 1·94 to 4·80, p = 1·3 × 10-6). We also show that individual-specific somatic expansion scores are associated with variants in FAN1 (pFDR = 4·8 × 10-6), MLH3 (pFDR = 8·0 × 10-4), MLH1 (pFDR = 0·004) and MSH3 (pFDR = 0·009). We also show that HD outcomes are best predicted by the number of pure CAGs rather than total encoded-glutamines. INTERPRETATION: These data establish pure CAG length, rather than encoded-glutamine, as the key inherited determinant of downstream pathophysiology. These findings have implications for HD diagnostics, and support somatic expansion as a mechanistic link for genetic modifiers of clinical outcomes, a driver of disease, and potential therapeutic target in HD and related repeat expansion disorders. FUNDING: CHDI Foundation.


Assuntos
Reparo do DNA , Predisposição Genética para Doença , Proteína Huntingtina/genética , Doença de Huntington/genética , Expansão das Repetições de Trinucleotídeos , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Alelos , Criança , Éxons , Feminino , Genótipo , Humanos , Doença de Huntington/diagnóstico , Doença de Huntington/metabolismo , Masculino , Pessoa de Meia-Idade , Polimorfismo de Nucleotídeo Único , Locos de Características Quantitativas , Adulto Jovem
17.
Neurology ; 93(10): e995-e1009, 2019 09 03.
Artigo em Inglês | MEDLINE | ID: mdl-31395669

RESUMO

OBJECTIVE: To evaluate the role of genetic variation at the DMPK locus on symptomatic diversity in 250 adult, ambulant patients with myotonic dystrophy type 1 (DM1) recruited to the Observational Prolonged Trial in Myotonic Dystrophy Type 1 to Improve Quality of Life-Standards, a Target Identification Collaboration (OPTIMISTIC) clinical trial. METHODS: We used small pool PCR to correct age at sampling biases and estimate the progenitor allele CTG repeat length and somatic mutational dynamics, and AciI digests and repeat primed PCR to test for the presence of variant repeats. RESULTS: We confirmed disease severity is driven by progenitor allele length, is further modified by age, and, in some cases, sex, and that patients in whom the CTG repeat expands more rapidly in the soma develop symptoms earlier than predicted. We revealed a key role for variant repeats in reducing disease severity and quantified their role in delaying age at onset by approximately 13.2 years (95% confidence interval 5.7-20.7, 2-tailed t test t = -3.7, p = 0.0019). CONCLUSIONS: Careful characterization of the DMPK CTG repeat to define progenitor allele length and presence of variant repeats has increased utility in understanding clinical variability in a trial cohort and provides a genetic route for defining disease-specific outcome measures, and the basis of treatment response and stratification in DM1 trials.


Assuntos
Distrofia Miotônica/genética , Distrofia Miotônica/psicologia , Miotonina Proteína Quinase/genética , Qualidade de Vida/psicologia , Índice de Gravidade de Doença , Adulto , Estudos de Coortes , Feminino , Humanos , Masculino , Distrofia Miotônica/diagnóstico , Reação em Cadeia da Polimerase/métodos
18.
Neurology ; 92(24): e2803-e2814, 2019 06 11.
Artigo em Inglês | MEDLINE | ID: mdl-31118244

RESUMO

OBJECTIVE: To determine the value of quantitative MRI in providing imaging biomarkers for disease in 20 different upper and lower leg muscles of patients with myotonic dystrophy type 1 (DM1). METHODS: We acquired images covering these muscles in 33 genetically and clinically well-characterized patients with DM1 and 10 unaffected controls. MRIs were recorded with a Dixon method to determine muscle fat fraction, muscle volume, and contractile muscle volume, and a multi-echo spin-echo sequence was used to determine T2 water relaxation time (T2water), reflecting putative edema. RESULTS: Muscles in patients with DM1 had higher fat fractions than muscles of controls (15.6 ± 11.1% vs 3.7 ± 1.5%). In addition, patients had smaller muscle volumes (902 ± 232 vs 1,097 ± 251 cm3), smaller contractile muscle volumes (779 ± 247 vs 1,054 ± 246 cm3), and increased T2water (33.4 ± 1.0 vs 31.9 ± 0.6 milliseconds), indicating atrophy and edema, respectively. Lower leg muscles were affected most frequently, especially the gastrocnemius medialis and soleus. Distribution of fat content per muscle indicated gradual fat infiltration in DM1. Between-patient variation in fat fraction was explained by age (≈45%), and another ≈14% was explained by estimated progenitor CTG repeat length (r 2 = 0.485) and somatic instability (r 2 = 0.590). Fat fraction correlated with the 6-minute walk test (r = -0.553) and muscular impairment rating scale (r = 0.537) and revealed subclinical muscle involvement. CONCLUSION: This cross-sectional quantitative MRI study of 20 different lower extremity muscles in patients with DM1 revealed abnormal values for muscle fat fraction, volume, and T2water, which therefore may serve as objective biomarkers to assess disease state of skeletal muscles in these patients. CLINICALTRIALSGOV IDENTIFIER: NCT02118779.


Assuntos
Tecido Adiposo/diagnóstico por imagem , Músculo Esquelético/diagnóstico por imagem , Distrofia Miotônica/diagnóstico por imagem , Tecido Adiposo/patologia , Adulto , Estudos Transversais , Feminino , Humanos , Extremidade Inferior/diagnóstico por imagem , Extremidade Inferior/patologia , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Músculo Esquelético/patologia , Distrofia Miotônica/genética , Miotonina Proteína Quinase/genética , Tamanho do Órgão
19.
Eur J Hum Genet ; 26(11): 1635-1647, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-29967337

RESUMO

Myotonic dystrophy type 1 (DM1) is a multisystem disorder, caused by expansion of a CTG trinucleotide repeat in the 3'-untranslated region of the DMPK gene. The repeat expansion is somatically unstable and tends to increase in length with time, contributing to disease progression. In some individuals, the repeat array is interrupted by variant repeats such as CCG and CGG, stabilising the expansion and often leading to milder symptoms. We have characterised three families, each including one person with variant repeats that had arisen de novo on paternal transmission of the repeat expansion. Two individuals were identified for screening due to an unusual result in the laboratory diagnostic test, and the third due to exceptionally mild symptoms. The presence of variant repeats in all three expanded alleles was confirmed by restriction digestion of small pool PCR products, and allele structures were determined by PacBio sequencing. Each was different, but all contained CCG repeats close to the 3'-end of the repeat expansion. All other family members had inherited pure CTG repeats. The variant repeat-containing alleles were more stable in the blood than pure alleles of similar length, which may in part account for the mild symptoms observed in all three individuals. This emphasises the importance of somatic instability as a disease mechanism in DM1. Further, since patients with variant repeats may have unusually mild symptoms, identification of these individuals has important implications for genetic counselling and for patient stratification in DM1 clinical trials.


Assuntos
Distrofia Miotônica/genética , Fenótipo , Expansão das Repetições de Trinucleotídeos , Adulto , Idoso , Alelos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Distrofia Miotônica/patologia , Miotonina Proteína Quinase/genética , Linhagem
20.
Mol Ther ; 25(1): 24-43, 2017 01 04.
Artigo em Inglês | MEDLINE | ID: mdl-28129118

RESUMO

Myotonic dystrophy type 1 (DM1) is caused by (CTG⋅CAG)n-repeat expansion within the DMPK gene and thought to be mediated by a toxic RNA gain of function. Current attempts to develop therapy for this disease mainly aim at destroying or blocking abnormal properties of mutant DMPK (CUG)n RNA. Here, we explored a DNA-directed strategy and demonstrate that single clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9-cleavage in either its 5' or 3' unique flank promotes uncontrollable deletion of large segments from the expanded trinucleotide repeat, rather than formation of short indels usually seen after double-strand break repair. Complete and precise excision of the repeat tract from normal and large expanded DMPK alleles in myoblasts from unaffected individuals, DM1 patients, and a DM1 mouse model could be achieved at high frequency by dual CRISPR/Cas9-cleavage at either side of the (CTG⋅CAG)n sequence. Importantly, removal of the repeat appeared to have no detrimental effects on the expression of genes in the DM1 locus. Moreover, myogenic capacity, nucleocytoplasmic distribution, and abnormal RNP-binding behavior of transcripts from the edited DMPK gene were normalized. Dual sgRNA-guided excision of the (CTG⋅CAG)n tract by CRISPR/Cas9 technology is applicable for developing isogenic cell lines for research and may provide new therapeutic opportunities for patients with DM1.


Assuntos
Sistemas CRISPR-Cas , Edição de Genes , Instabilidade Genômica , Distrofia Miotônica/genética , Miotonina Proteína Quinase/genética , Expansão das Repetições de Trinucleotídeos , Repetições de Trinucleotídeos , Animais , Proteínas de Bactérias/genética , Sequência de Bases , Proteína 9 Associada à CRISPR , Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas , Códon , Modelos Animais de Doenças , Endonucleases/genética , Fibroblastos/metabolismo , Expressão Gênica , Ordem dos Genes , Loci Gênicos , Humanos , Camundongos , RNA Guia de Cinetoplastídeos , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Deleção de Sequência
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