RESUMO
Myotonic dystrophy type 1 (DM1) is a form of muscular dystrophy causing progressive muscle loss and weakness. Although clinical features can manifest at any age, it is the most common form of muscular dystrophy with onset in adulthood. DM1 is an autosomal dominant condition, resulting from an unstable CTG expansion in the 3'-untranslated region of the myotonic dystrophy protein kinase (DMPK) gene. The age of onset and the severity of the phenotype are roughly correlated with the size of the CTG expansion. Multiple methodologies can be used to diagnose affected individuals with DM1, including polymerase chain reaction, Southern blot, and triplet repeat-primed polymerase chain reaction. Recently, triplet repeat interruptions have been described, which may affect clinical outcomes of a fully-variable allele in DMPK. This document supersedes the Technical Standards and Guidelines for Myotonic Dystrophy originally published in 2009 and reaffirmed in 2015. It is designed for genetic testing professionals who are already familiar with the disease and the methods of analysis.
Assuntos
Testes Genéticos , Genética Médica , Genômica , Distrofia Miotônica , Miotonina Proteína Quinase , Expansão das Repetições de Trinucleotídeos , Distrofia Miotônica/genética , Distrofia Miotônica/diagnóstico , Humanos , Miotonina Proteína Quinase/genética , Testes Genéticos/normas , Testes Genéticos/métodos , Genética Médica/normas , Genética Médica/métodos , Expansão das Repetições de Trinucleotídeos/genética , Genômica/métodos , Genômica/normas , Estados UnidosRESUMO
Congenital myotonic dystrophy (CDM) is a genetic disease caused by an abnormally long CTG repeat expansion in the DMPK gene, which generally increases in size following intergenerational transmission. CDM is the rarest and most severe form of myotonic dystrophy type 1, yet an important number of patient-derived cells are needed to study this heterogeneous disease. Therefore, we have reprogrammed lymphoblastoid cells derived from a 3-year-old male with CDM into induced pluripotent stem cells (iPSCs; CBRCULi015-A) featuring 1800 CTG repeats and characterized their pluripotent state. This cell line constitutes an important resource to study CDM and potential treatments in vitro.
Assuntos
Células-Tronco Pluripotentes Induzidas , Distrofia Miotônica , Humanos , Distrofia Miotônica/patologia , Distrofia Miotônica/genética , Células-Tronco Pluripotentes Induzidas/metabolismo , Masculino , Pré-Escolar , Linhagem Celular , Diferenciação Celular , Miotonina Proteína Quinase/genéticaRESUMO
Myotonic dystrophy type 1 is an autosomal dominant condition due to a CTG repeat expansion in the myotonic dystrophy protein kinase (DMPK) gene. This multisystem disorder affects multiple organ systems. Hypogonadism in males affected by myotonic dystrophy is commonly reported; however, the effect on female hypogonadism remains controversial. A 19-year-old female was referred to our genetics clinic due to primary amenorrhea without any family history of similar symptoms. Initial genetics evaluation identified a variant of uncertain significance in IGSF10, c.2210T>C (p.Phe737Ser). Follow-up genetic evaluation via whole genome sequencing identified at least 100 CTG repeats in the DMPK gene, thus resulting in the diagnosis of myotonic dystrophy type 1. The patient remains otherwise asymptomatic from myotonic dystrophy. This is the first report that demonstrates primary amenorrhea as a possible presenting feature of myotonic dystrophy type 1, thus providing evidence supporting female hypogonadism in myotonic dystrophy type 1.
Assuntos
Amenorreia , Achados Incidentais , Distrofia Miotônica , Miotonina Proteína Quinase , Sequenciamento Completo do Genoma , Humanos , Distrofia Miotônica/genética , Distrofia Miotônica/diagnóstico , Distrofia Miotônica/complicações , Amenorreia/genética , Amenorreia/diagnóstico , Feminino , Miotonina Proteína Quinase/genética , Adulto Jovem , Adulto , Expansão das Repetições de Trinucleotídeos/genética , Hipogonadismo/genética , Hipogonadismo/patologia , Hipogonadismo/diagnósticoRESUMO
The tumor-associated macrophages (TAMs) play multifaceted roles in the progression of hepatocellular carcinoma (HCC). However, the involvement of circular RNAs in the interplay between TAMs and HCC remains unclear. Based on Transwell co-culturing and circular RNA sequencing, this study revealed that TAMs enhanced tumor glycolysis and progression by upregulating circMRCKα in HCC cells. Patients with HCC who exhibited elevated circMRCKα levels presented significantly reduced overall survival and greater cumulative recurrence. Notably, we identified a novel functional peptide of 227 amino acids named circMRCKα-227aa, encoded by circMRCKα. Mechanistically, circMRCKα-227aa bound to USP22 and enhanced its protein level to obstruct HIF-1α degradation via the ubiquitin-proteasome pathway, thereby augmenting HCC glycolysis and progression. In clinical HCC samples, a positive correlation was observed between the expression of circMRCKα and the number of infiltrating CD68+ TAMs and expression of USP22. Furthermore, circMRCKα emerged as an independent prognostic risk factor both individually and in conjunction with CD68+ TAMs and USP22. This study illustrated that circMRCKα-227aa, a novel TAM-induced peptide, promotes tumor glycolysis and progression via USP22 binding and HIF-1α upregulation, suggesting that circMRCKα and TAMs could be combined as therapeutic targets in HCC.
Assuntos
Carcinoma Hepatocelular , Glicólise , Neoplasias Hepáticas , RNA Circular , Macrófagos Associados a Tumor , Animais , Feminino , Humanos , Masculino , Camundongos , Carcinoma Hepatocelular/genética , Carcinoma Hepatocelular/patologia , Carcinoma Hepatocelular/metabolismo , Linhagem Celular Tumoral , Progressão da Doença , Regulação Neoplásica da Expressão Gênica , Subunidade alfa do Fator 1 Induzível por Hipóxia/genética , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Neoplasias Hepáticas/patologia , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/metabolismo , Peptídeos/metabolismo , Prognóstico , RNA Circular/genética , RNA Circular/metabolismo , Macrófagos Associados a Tumor/metabolismo , Macrófagos Associados a Tumor/imunologia , Ubiquitina Tiolesterase/genética , Ubiquitina Tiolesterase/metabolismo , Miotonina Proteína Quinase/genéticaRESUMO
Myotonic dystrophy type 1 (DM1) is the most prevalent adult-onset muscular dystrophy affecting 1 in 8,000 individuals. It is characterized by multisystemic symptoms, primarily myopathy. The root cause of DM1 is a heterozygous CTG triplet expansion beyond the normal size threshold in the non-coding region of the DM1 protein kinase gene (DMPK). In our study, we generated and characterized three distinct DM1 induced pluripotent stem cell (iPSC) lines with CTG repeat expansions ranging from 900 to 2000 in the DMPK gene. These iPSC lines maintained normal karyotypes, exhibited distinctive colony morphology, robustly expressed pluripotency markers, differentiated into the three primary germ layers, and lacked residual viral vectors.
Assuntos
Células-Tronco Pluripotentes Induzidas , Distrofia Miotônica , Adulto , Humanos , Distrofia Miotônica/genética , Distrofia Miotônica/metabolismo , Células-Tronco Pluripotentes Induzidas/metabolismo , Expansão das Repetições de Trinucleotídeos , Experimentação Humana Terapêutica , Linhagem Celular , Miotonina Proteína Quinase/genéticaRESUMO
Myotonic dystrophy type 1 (DM1) is an autosomal dominant disorder caused by an unstable expanded CTG repeat located in the 3'-UTR of the DM1 protein kinase (DMPK) gene. The pathogenic mechanism results in misregulated alternative splicing of hundreds of genes, creating the dilemma of establishing which genes contribute to the mechanism of DM1 skeletal muscle pathology. In this issue of the JCI, Cisco and colleagues systematically tested the combinatorial effects of DM1-relevant mis-splicing patterns in vivo and identified the synergistic effects of mis-spliced calcium and chloride channels as a major contributor to DM1 skeletal muscle impairment. The authors further demonstrated the therapeutic potential for calcium channel modulation to block the synergistic effects and rescue myopathy.
Assuntos
Distrofia Miotônica , Humanos , Distrofia Miotônica/metabolismo , Splicing de RNA , Músculo Esquelético/metabolismo , Processamento Alternativo , Canais Iônicos/metabolismo , Miotonina Proteína Quinase/genética , Miotonina Proteína Quinase/metabolismo , Expansão das Repetições de TrinucleotídeosRESUMO
Congenital myotonic dystrophy (CDM) is an autosomal dominant multisystemic disorder attributed to a large expansion of CTG trinucleotide repeats within the myotonic dystrophy protein kinase (DMPK) gene. In this study, we successfully reprogrammed dermal fibroblasts derived from two pediatric CDM patients and two age-matched individuals into induced pluripotent stem cells (iPSCs) using a non-integrating viral vector. The resulting CDM iPSC lines harbored approximately 2000 CTG repeats in the mutated DMPK allele. These iPSC lines expressed pluripotency markers and exhibited the capacity to differentiate into cells representing all three germinal layers, confirming their reliability as a research tool for investigating CDM and therapeutic strategies.
Assuntos
Células-Tronco Pluripotentes Induzidas , Distrofia Miotônica , Humanos , Criança , Distrofia Miotônica/genética , Distrofia Miotônica/metabolismo , Células-Tronco Pluripotentes Induzidas/metabolismo , Expansão das Repetições de Trinucleotídeos , Reprodutibilidade dos Testes , Miotonina Proteína Quinase/genéticaRESUMO
Myotonic dystrophy type 1 (DM1) is a genetic neuromuscular disorder that affects many organs, including the heart. DM1 is caused by a heterozygous CTG triplet expansion exceeding the normal size threshold in the non-coding region of the DM1 protein kinase gene (DMPK). We generated and characterized a DM1 iPSC line carrying a 700 CTG repeat expansion as well as a control iPSC line from a healthy individual. The two iPSC lines expressed several pluripotency markers, had the capacity to differentiate into the three primary germ layers, had no residual viral vectors, had normal karyotypes, and had a typical colony morphology.
Assuntos
Células-Tronco Pluripotentes Induzidas , Distrofia Miotônica , Humanos , Distrofia Miotônica/genética , Distrofia Miotônica/metabolismo , Expansão das Repetições de Trinucleotídeos/genética , Células-Tronco Pluripotentes Induzidas/metabolismo , Linhagem Celular , Miotonina Proteína Quinase/genéticaRESUMO
Myotonic dystrophy type 1 (DM1) is an autosomal dominant multisystemic disease caused by a CTG repeat expansion in the 3'-untranslated region (UTR) of DMPK gene. DM1 alleles containing non-CTG variant repeats (VRs) have been described, with uncertain molecular and clinical consequences. The expanded trinucleotide array is flanked by two CpG islands, and the presence of VRs could confer an additional level of epigenetic variability. This study aims to investigate the association between VR-containing DMPK alleles, parental inheritance and methylation pattern of the DM1 locus. The DM1 mutation has been characterized in 20 patients using a combination of SR-PCR, TP-PCR, modified TP-PCR and LR-PCR. Non-CTG motifs have been confirmed by Sanger sequencing. The methylation pattern of the DM1 locus was determined by bisulfite pyrosequencing. We characterized 7 patients with VRs within the CTG tract at 5' end and 13 patients carrying non-CTG sequences at 3' end of the DM1 expansion. DMPK alleles with VRs at 5' end or 3' end were invariably unmethylated upstream of the CTG expansion. Interestingly, DM1 patients with VRs at the 3' end showed higher methylation levels in the downstream island of the CTG repeat tract, preferentially when the disease allele was maternally inherited. Our results suggest a potential correlation between VRs, parental origin of the mutation and methylation pattern of the DMPK expanded alleles. A differential CpG methylation status could play a role in the phenotypic variability of DM1 patients, representing a potentially useful diagnostic tool.
Assuntos
Distrofia Miotônica , Humanos , Distrofia Miotônica/genética , Alelos , Miotonina Proteína Quinase/genética , Expansão das Repetições de Trinucleotídeos , Ilhas de CpGRESUMO
BACKGROUND AND PURPOSE: Myotonic dystrophy type 1 (DM1) is the most common form of adult-onset muscular dystrophy and is caused by an repeat expansion [r(CUG)exp] located in the 3' untranslated region of the DMPK gene. Symptoms include skeletal and cardiac muscle dysfunction and fibrosis. In DM1, there is a lack of established biomarkers in routine clinical practice. Thus, we aimed to identify a blood biomarker with relevance for DM1-pathophysiology and clinical presentation. METHODS: We collected fibroblasts from 11, skeletal muscles from 27, and blood samples from 158 DM1 patients. Moreover, serum, cardiac, and skeletal muscle samples from DMSXL mice were included. We employed proteomics, immunostaining, qPCR and ELISA. Periostin level were correlated with CMRI-data available for some patients. RESULTS: Our studies identified Periostin, a modulator of fibrosis, as a novel biomarker candidate for DM1: proteomic profiling of human fibroblasts and murine skeletal muscles showed significant dysregulation of Periostin. Immunostaining on skeletal and cardiac muscles from DM1 patients and DMSXL mice showed an extracellular increase of Periostin, indicating fibrosis. qPCR studies indicated increased POSTN expression in fibroblasts and muscle. Quantification of Periostin in blood samples from DMSXL mice and two large validation cohorts of DM1 patients showed decreased levels in animals and diseased individuals correlating with repeat expansion and disease severity and presence of cardiac symptoms identified by MRI. Analyses of longitudinal blood samples revealed no correlation with disease progression. CONCLUSIONS: Periostin might serve as a novel stratification biomarker for DM1 correlating with disease severity, presence of cardiac malfunction and fibrosis.
Assuntos
Cardiomiopatias , Distrofia Miotônica , Adulto , Humanos , Camundongos , Animais , Distrofia Miotônica/genética , Expansão das Repetições de Trinucleotídeos , Proteômica , Músculo Esquelético , Células Musculares/metabolismo , Cardiomiopatias/genética , Cardiomiopatias/metabolismo , Gravidade do Paciente , Miotonina Proteína Quinase/genéticaRESUMO
Reduced brain volume including atrophy in grey and white matter is commonly seen in myotonic dystrophy type 1 (DM1). DM1 is caused by an expansion of CTG trinucleotide repeats in the 3' untranslated region (UTR) of the Dystrophia Myotonica Protein Kinase (DMPK) gene. Mutant DMPK mRNA containing expanded CUG RNA (DMPK-CUGexp) sequesters cytoplasmic MBNL1, resulting in morphological impairment. How DMPK-CUGexp and loss of MBNL1 cause histopathological phenotypes in the DM1 brain remains elusive. Here, we show that BDNF-TrkB retrograde transport is impaired in neurons expressing DMPK-CUGexp due to loss of cytoplasmic MBNL1 function. We reveal that mature BDNF protein levels are reduced in the brain of the DM1 mouse model EpA960/CaMKII-Cre. Exogenous BDNF treatment did not rescue impaired neurite outgrowth in neurons expressing DMPK-CUGexp, whereas overexpression of the cytoplasmic MBNL1 isoform in DMPK-CUGexp-expressing neurons improved their responsiveness to exogenous BDNF. We identify dynein light chain LC8-type 2, DYNLL2, as an MBNL1-interacting protein and demonstrate that their interaction is RNA-independent. Using time-lapse imaging, we show that overexpressed MBNL1 and DYNLL2 move along axonal processes together and that MBNL1-knockdown impairs the motility of mCherry-tagged DYNLL2, resulting in a reduced percentage of retrograde DYNLL2 movement. Examination of the distribution of DYNLL2 and activated phospho-TrkB (pTrkB) receptor in EpA960/CaMKII-Cre brains revealed an increase in the postsynaptic membrane fraction (LP1), indicating impaired retrograde transport. Finally, our neuropathological analysis of postmortem DM1 tissue reveals that reduced cytoplasmic MBNL1 expression is associated with an increase in DYNLL2 and activated pTrkB receptor levels in the synaptosomal fraction. Together, our results support that impaired MBNL1-mediated retrograde BDNF-TrkB signaling may contribute to the histopathological phenotypes of DM1.
Assuntos
Distrofia Miotônica , Animais , Camundongos , Distrofia Miotônica/genética , Distrofia Miotônica/metabolismo , Distrofia Miotônica/patologia , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Expansão das Repetições de Trinucleotídeos , Miotonina Proteína Quinase/genética , Miotonina Proteína Quinase/metabolismo , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/genética , RNA/genética , Encéfalo/patologia , Proteínas de Ligação a DNA/metabolismo , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a RNA/metabolismoRESUMO
Myotonic dystrophy Type 1 (DM1) is a severe inherited neuromuscular disease and is the most prevalent form of muscular dystrophy in adults. DM1 involves not only the striated muscles including skeletal, and cardiac but also other organs such as the eye, brain and gonads. We have generated and characterized 4 adult heterozygous DM1 iPSC lines carrying between 1300 and 1600 CTG repeat expansion in the DM1 protein kinase gene, and a control from an apparently healthy individual. They all show strong pluripotency markers, differentiation capacity, the absence of residual viral vectors as well as normal karyotypes and colony morphologies.
Assuntos
Células-Tronco Pluripotentes Induzidas , Distrofia Miotônica , Adulto , Humanos , Distrofia Miotônica/metabolismo , Células-Tronco Pluripotentes Induzidas/metabolismo , Expansão das Repetições de Trinucleotídeos , Linhagem Celular , Músculo Esquelético/metabolismo , Miotonina Proteína Quinase/genéticaRESUMO
Protein kinases of the dystonia myotonica protein kinase (DMPK) family are critical regulators of actomyosin contractility in cells. The DMPK kinase MRCK1 is required for the activation of myosin, leading to the development of cortical tension, apical constriction, and early gastrulation. Here, we present the structure, conformation, and membrane-binding properties of Caenorhabditis elegans MRCK1. MRCK1 forms a homodimer with N-terminal kinase domains, a parallel coiled coil of 55 nm, and a C-terminal tripartite module of C1, pleckstrin homology (PH), and citron homology (CNH) domains. We report the high-resolution structure of the membrane-binding C1-PH-CNH module of MRCK1 and, using high-throughput and conventional liposome-binding assays, determine its binding to specific phospholipids. We further characterize the interaction of the C-terminal CRIB motif with Cdc42. The length of the coiled-coil domain of DMPK kinases is remarkably conserved over millions of years of evolution, suggesting that they may function as molecular rulers to position kinase activity at a fixed distance from the membrane.
Assuntos
Distrofia Miotônica , Proteínas Serina-Treonina Quinases , Animais , Proteínas Serina-Treonina Quinases/química , Miotonina Proteína Quinase/genética , Miotonina Proteína Quinase/metabolismo , Sequência de Aminoácidos , Proteínas Quinases/metabolismo , Caenorhabditis elegans/metabolismoRESUMO
Myotonic dystrophy type 1 (DM1) is a multi-systemic disorder caused by expansion of CTG microsatellite repeats within DMPK. The most severe form, congenital myotonic dystrophy (CDM), has symptom onset at birth due to large intergenerational repeat expansions. Despite a common mutation, CDM individuals present with a distinct clinical phenotype and absence of common DM1 symptoms. Given the clinical divergence, it is unknown if the hallmark of DM1 pathology, dysregulation of alternative splicing (AS) due to sequestration of MBNL proteins within toxic CUG repeat RNAs, contributes to disease throughout pediatric development. To evaluate global transcriptomic dysregulation, RNA-seq was performed on 36 CDM skeletal muscle biopsies ages 2 weeks to 16 years, including two longitudinal samples. Fifty DM1 and adult/pediatric controls were also sequenced as comparative groups. Despite a large CTG expansion and shared age of onset, CDM individuals presented with a heterogenous, MBNL-dependent mis-splicing signature. Estimation of intracellular MBNL concentrations from splicing responses of select events correlated with total spliceopathy and revealed a distinct, triphasic pattern of AS dysregulation across pediatric development. CDM infants (< 2 years) possess severe mis-splicing that significantly improves in early childhood (2-8 years) independent of sex or CTG repeat load. Adolescent individuals (8-16 years) stratified into two populations with a full range of global splicing dysregulation. DMPK expression changes correlated with alterations in splicing severity during development. This study reveals the complex dynamics of the CDM muscle transcriptome and provides insights into new therapeutic strategies, timing of therapeutic intervention, and biomarker development.
Assuntos
Distrofia Miotônica , Pré-Escolar , Humanos , Distrofia Miotônica/patologia , Transcriptoma/genética , Miotonina Proteína Quinase/genética , Miotonina Proteína Quinase/metabolismo , Músculo Esquelético/metabolismo , Splicing de RNA/genética , Expansão das Repetições de Trinucleotídeos/genéticaRESUMO
Myotonic dystrophy type 1 is a complex disease caused by a genetically unstable CTG repeat expansion in the 3'-untranslated region of the DMPK gene. Age-dependent, tissue-specific somatic instability has confounded genotype-phenotype associations, but growing evidence suggests that it also contributes directly toward disease progression. Using a well-characterized clinical cohort of DM1 patients from Costa Rica, we quantified somatic instability in blood, buccal cells, skin and skeletal muscle. Whilst skeletal muscle showed the largest expansions, modal allele lengths in skin were also very large and frequently exceeded 2000 CTG repeats. Similarly, the degree of somatic expansion in blood, muscle and skin were associated with each other. Notably, we found that the degree of somatic expansion in skin was highly predictive of that in skeletal muscle. More importantly, we established that individuals whose repeat expanded more rapidly than expected in one tissue (after correction for progenitor allele length and age) also expanded more rapidly than expected in other tissues. We also provide evidence suggesting that individuals in whom the repeat expanded more rapidly than expected in skeletal muscle have an earlier age at onset than expected (after correction for the progenitor allele length). Pyrosequencing analyses of the genomic DNA flanking the CTG repeat revealed that the degree of methylation in muscle was well predicted by the muscle modal allele length and age, but that neither methylation of the flanking DNA nor levels of DMPK sense and anti-sense transcripts could obviously explain individual- or tissue-specific patterns of somatic instability.
Assuntos
Distrofia Miotônica , Humanos , Distrofia Miotônica/genética , Expansão das Repetições de Trinucleotídeos/genética , Mucosa Bucal , Alelos , DNA/genética , Miotonina Proteína Quinase/genéticaRESUMO
Myotonic dystrophy type 1 (DM1) is a dominant genetic disease in which the expansion of long CTG trinucleotides in the 3' UTR of the myotonic dystrophy protein kinase (DMPK) gene results in toxic RNA gain-of-function and gene mis-splicing affecting mainly the muscles, the heart, and the brain. The CUG-expanded transcripts are a suitable target for the development of antisense oligonucleotide (ASO) therapies. Various chemical modifications of the sugar-phosphate backbone have been reported to significantly enhance the affinity of ASOs for RNA and their resistance to nucleases, making it possible to reverse DM1-like symptoms following systemic administration in different transgenic mouse models. However, specific tissue delivery remains to be improved to achieve significant clinical outcomes in humans. Several strategies, including ASO conjugation to cell-penetrating peptides, fatty acids, or monoclonal antibodies, have recently been shown to improve potency in muscle and cardiac tissues in mice. Moreover, intrathecal administration of ASOs may be an advantageous complementary administration route to bypass the blood-brain barrier and correct defects of the central nervous system in DM1. This review describes the evolution of the chemical design of antisense oligonucleotides targeting CUG-expanded mRNAs and how recent advances in the field may be game-changing by forwarding laboratory findings into clinical research and treatments for DM1 and other microsatellite diseases.
Assuntos
Distrofia Miotônica , Camundongos , Humanos , Animais , Distrofia Miotônica/tratamento farmacológico , Distrofia Miotônica/genética , Miotonina Proteína Quinase/genética , Oligonucleotídeos Antissenso/genética , Oligonucleotídeos Antissenso/uso terapêutico , Camundongos Transgênicos , Oligonucleotídeos/uso terapêutico , Regiões 3' não Traduzidas , Expansão das Repetições de TrinucleotídeosRESUMO
Myotonic dystrophy type 1 (DM1) exhibits highly heterogeneous clinical manifestations caused by an unstable CTG repeat expansion reaching up to 4000 CTG. The clinical variability depends on CTG repeat number, CNG repeat interruptions, and somatic mosaicism. Currently, none of these factors are simultaneously and accurately determined due to the limitations of gold standard methods used in clinical and research laboratories. An amplicon method for targeting the DMPK locus using single-molecule real-time sequencing was recently developed to accurately analyze expanded alleles. However, amplicon-based sequencing still depends on PCR, and the inherent bias toward preferential amplification of smaller repeats can be problematic in DM1. Thus, an amplification-free long-read sequencing method was developed by using CRISPR/Cas9 technology in DM1. This method was used to sequence the DMPK locus in patients with CTG repeat expansion ranging from 130 to >1000 CTG. We showed that elimination of PCR amplification improves the accuracy of measurement of inherited repeat number and somatic repeat variations, two key factors in DM1 severity and age at onset. For the first time, an expansion composed of >85% CCG repeats was identified by using this innovative method in a DM1 family with an atypical clinical profile. No-amplification targeted sequencing represents a promising method that can overcome research and diagnosis shortcomings, with translational implications for clinical and genetic counseling in DM1.
Assuntos
Distrofia Miotônica , Humanos , Distrofia Miotônica/diagnóstico , Distrofia Miotônica/genética , Miotonina Proteína Quinase/genética , Alelos , Expansão das Repetições de Trinucleotídeos/genética , Aconselhamento GenéticoRESUMO
Objective In myotonic dystrophy type 1 (DM1), the CTG repeat size in the dystrophia myotonica protein kinase gene has been shown to correlate with disease severity and is a potential predictive marker for respiratory decline. However, genetic testing can be challenging in some clinical situations. We developed a simple formula for estimating the CTG repeat size using a single spirometry test in patients with DM1. Methods In this single-center retrospective study, we reviewed 50 consecutive patients with genetically confirmed DM1 whose follow-up visits were at our hospital. The patients were randomly assigned to training and test analysis subsets. By applying a linear mixed model to the longitudinal spirometry results of the training set, we calculated the fixed effects on the annual respiratory decline. Subsequently, we derived a prediction formula to calculate the repeat size that incorporated %vital capacity (%VC) and the patient's age at the time of the spirometry evaluation; the results were validated by the test set. Results A total of 157 spirometry tests were recorded. The fixed effects on the annual %VC decline were =-0.90. The derived formula [repeat size=-16.8× (age+%VC/0.90) +2663] had a moderate predictive performance with a mean coefficient of determination
of 0.41. Conclusion The CTG repeat size in patients with DM1 can be potentially predicted using a simple formula based on a single spirometry test conducted at any time over the disease course. It can be useful as a supportive tool for advance care planning when genetic testing is not available.
Assuntos
Distrofia Miotônica , Progressão da Doença , Humanos , Distrofia Miotônica/diagnóstico , Distrofia Miotônica/genética , Miotonina Proteína Quinase/genética , Ensaios Clínicos Controlados Aleatórios como Assunto , Estudos Retrospectivos , Espirometria , Expansão das Repetições de Trinucleotídeos/genéticaRESUMO
RNA regulation in mammalian cells requires complex physical compartmentalisation, using structures thought to be formed by liquid-liquid phase separation. Disruption of these structures is implicated in numerous degenerative diseases. Myotonic dystrophy type 1 (DM1) is a multi-systemic trinucleotide repeat disorder resulting from an expansion of nucleotides CTG (CTGexp) in the DNA encoding DM1 protein kinase (DMPK). The cellular hallmark of DM1 is the formation of nuclear foci that contain expanded DMPK RNA (CUGexp) (with thymine instead of uracil). We report here the deregulation of stress granules (SGs) and processing bodies (P-bodies), two cytoplasmic structures key for mRNA regulation, in cell culture models of DM1. Alterations to the rates of formation and dispersal of SGs suggest an altered ability of cells to respond to stress associated with DM1, while changes to the structure and dynamics of SGs and P-bodies suggest that a widespread alteration to the biophysical properties of cellular structures is a consequence of the presence of CUGexp RNA.
Assuntos
Distrofia Miotônica , Animais , Mamíferos/metabolismo , Distrofia Miotônica/genética , Miotonina Proteína Quinase/genética , Miotonina Proteína Quinase/metabolismo , Corpos de Processamento , RNA , Grânulos de Estresse , Expansão das Repetições de Trinucleotídeos/genéticaRESUMO
Myotonic dystrophy type 1 (DM1) is a multisystemic neuromuscular disorder caused by the expansion of a CTG repeat in the 3'-UTR of DMPK, which is transcribed to a toxic gain-of-function RNA that affects splicing of a range of genes. The expanded repeat is unstable in both germline and somatic cells. The variable age at disease onset and severity of symptoms have been linked to the inherited CTG repeat length, non-CTG interruptions, and methylation levels flanking the repeat. In general, the genetic biomarkers are investigated separately with specific methods, making it tedious to obtain an overall characterisation of the repeat for a given individual. In the present study, we employed Oxford nanopore sequencing in a pilot study to simultaneously determine the repeat lengths, investigate the presence and nature of repeat interruptions, and quantify methylation levels in the regions flanking the CTG-repeats in four patients with DM1. We determined the repeat lengths, and in three patients, we observed interruptions which were not detected using repeat-primed PCR. Interruptions may thus be more common than previously anticipated and should be investigated in larger cohorts. Allele-specific analyses enabled characterisation of aberrant methylation levels specific to the expanded allele, which greatly increased the sensitivity and resolved cases where the methylation levels were ambiguous.