Molecular genetics and genetic testing in myotonic dystrophy type 1

Clinical score for early diagnosis of myotonic dystrophy type 2

INTRODUCTION

Myotonic dystrophy type 2 (DM2) is a rare, multisystemic, autosomal dominant disease with highly variable clinical presentation. DM2 is considered to be highly underdiagnosed.

OBJECTIVE

The aim of this study was to determine which symptoms, signs, and diagnostic findings in patients referred to neurological outpatient units are the most indicative to arouse suspicion of DM2. We tried to make a useful and easy-to-administer clinical scoring system for early diagnosis of DM2-DM2 early diagnosis score (DM2-EDS).

PATIENTS AND METHODS

Two hundred ninety-one patients with a clinical suspicion of DM2 were included: 69 were genetically confirmed to have DM2, and 222 patients were DM2 negative. Relevant history, neurological, and paraclinical data were obtained from the electronic medical records.

RESULTS

The following parameters appeared as significant predictors of DM2 diagnosis: cataracts (beta = 0.410, p < 0.001), myotonia on needle EMG (beta = 0.298, p < 0.001), hand tremor (beta = 0.211, p = 0.001), positive family history (beta = 0.171, p = 0.012), and calf hypertrophy (beta = 0.120, p = 0.043). In the final DM2-EDS, based on the beta values, symptoms were associated with the following values: cataracts (present 3.4, absent 0), myotonia (present 2.5, absent 0), tremor (present 1.7, absent 0), family history (positive 1.4, negative 0), and calf hypertrophy (present 1.0, absent 0). A cut-off value on DM2-EDS of 3.25 of maximum 10 points had a sensitivity of 84% and specificity of 81% to diagnose DM2.

CONCLUSION

Significant predictors of DM2 diagnosis in the neurology outpatient unit were identified. We made an easy-to-administer DM2-EDS score for early diagnosis of DM2.

Resistance Exercise Training Rescues Mitochondrial Dysfunction in Skeletal Muscle of Patients with Myotonic Dystrophy Type 1

BACKGROUND

Myotonic dystrophy type 1 (DM1) is a dominant autosomal neuromuscular disorder caused by the inheritance of a CTG triplet repeat expansion in the Dystrophia Myotonica Protein Kinase (DMPK) gene. At present, no cure currently exists for DM1 disease.

OBJECTIVE

This study investigates the effects of 12-week resistance exercise training on mitochondrial oxidative phosphorylation in skeletal muscle in a cohort of DM1 patients (n = 11, men) in comparison to control muscle with normal oxidative phosphorylation.

METHODS

Immunofluorescence was used to assess protein levels of key respiratory chain subunits of complex I (CI) and complex IV (CIV), and markers of mitochondrial mass and cell membrane in individual myofibres sampled from muscle biopsies. Using control's skeletal muscle fibers population, we classified each patient's fibers as having normal, low or high levels of CI and CIV and compared the proportions of fibers before and after exercise training. The significance of changes observed between pre- and post-exercise within patients was estimated using a permutation test.

RESULTS

At baseline, DM1 patients present with significantly decreased mitochondrial mass, and isolated or combined CI and CIV deficiency. After resistance exercise training, in most patients a significant increase in mitochondrial mass was observed, and all patients showed a significant increase in CI and/or CIV protein levels. Moreover, improvements in mitochondrial mass were correlated with the one-repetition maximum strength evaluation.

CONCLUSIONS

Remarkably, 12-week resistance exercise training is sufficient to partially rescue mitochondrial dysfunction in DM1 patients, suggesting that the response to exercise is in part be due to changes in mitochondria.

Identification of a CCG-Enriched Expanded Allele in Patients with Myotonic Dystrophy Type 1 Using Amplification-Free Long-Read Sequencing

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.

Autoimmune Diseases in Patients With Myotonic Dystrophy Type 2

Introduction

Myotonic dystrophy type 2 (DM2) is a rare autosomal dominant multisystemic disease with highly variable clinical presentation. Several case reports and one cohort study suggested a significant association between DM2 and autoimmune diseases (AIDs).

Aim

The aim of this study is to analyze the frequency and type of AIDs in patients with DM2 from the Serbian DM registry.

Patients and Methods

A total of 131 patients with DM2 from 108 families were included, [62.6% women, mean age at DM2 onset 40.4 (with standard deviation 13) years, age at entering the registry 52 (12.8) years, and age at analysis 58.4 (12.8) years]. Data were obtained from Akhenaten, the Serbian registry for DM, and through the hospital electronic data system.

Results

Upon entering the registry, 35 (26.7%) of the 131 patients with DM2 had AIDs including Hashimoto thyroiditis (18.1%), rheumatoid arthritis, diabetes mellitus type 1, systemic lupus, Sjogren's disease, localized scleroderma, psoriasis, celiac disease, Graves's disease, neuromyelitis optica, myasthenia gravis, and Guillain-Barre syndrome. At the time of data analysis, one additional patient developed new AIDs, so eventually, 36 (28.8%) of 125 DM2 survivors had AIDs. Antinuclear antibodies (ANAs) were found in 14 (10.7%) of 63 tested patients, including 12 without defined corresponding AID (all in low titers, 1:40 to 1:160). Antineutrophil cytoplasmic antibodies (ANCAs) were negative in all 50 tested cases. The percentage of women was significantly higher among patients with AIDs (82.9% vs. 55.2%, p <0.01).

Conclusion

AIDs were present in as high as 30% of the patients with DM2. Thus, screening for AIDs in DM2 seems reasonable. Presence of AIDs and/or ANAs may lead to under-diagnosis of DM2.

High Resolution Analysis of DMPK Hypermethylation and Repeat Interruptions in Myotonic Dystrophy Type 1

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.

Outcome measures frequently used to assess muscle strength in patients with myotonic dystrophy type 1: a systematic review

Measurement of muscle strength is fundamental for the management of patients with myotonic dystrophy type 1 (DM1). Nevertheless, guidance on this topic is somewhat limited due to heterogeneous outcome measures used. This systematic literature review aimed to summarize the most frequent outcome measures to assess muscle strength in patients with DM1. We searched on Pubmed, Web of Science and Embase databases. Observational studies using measures of muscle strength assessment in adult patients with DM1 were included. From a total of 80 included studies, 24 measured cardiac, 45 skeletal and 23 respiratory muscle strength. The most common method and outcome measures used to assess cardiac muscle strength were echocardiography and ejection fraction, for skeletal muscle strength were quantitative muscle test, manual muscle test and maximum isometric torque and medical research council and for respiratory muscle strength were manometry and maximal inspiratory and expiratory pressure. We successfully gathered the more consensual methods and measures to evaluate muscle strength in future clinical studies, particularly to test muscle strength response to treatments in patients with DM1. Future consensus on a set of measures to evaluate muscle strength (core outcome set), is important for these patients.

Molecular Pathogenesis and Peripheral Monitoring of Adult Fragile X-Associated Syndromes

Abnormal trinucleotide expansions cause rare disorders that compromise quality of life and, in some cases, lifespan. In particular, the expansions of the CGG-repeats stretch at the 5’-UTR of the Fragile X Mental Retardation 1 (FMR1) gene have pleiotropic effects that lead to a variety of Fragile X-associated syndromes: the neurodevelopmental Fragile X syndrome (FXS) in children, the late-onset neurodegenerative disorder Fragile X-associated tremor-ataxia syndrome (FXTAS) that mainly affects adult men, the Fragile X-associated primary ovarian insufficiency (FXPOI) in adult women, and a variety of psychiatric and affective disorders that are under the term of Fragile X-associated neuropsychiatric disorders (FXAND). In this review, we will describe the pathological mechanisms of the adult “gain-of-function” syndromes that are mainly caused by the toxic actions of CGG RNA and FMRpolyG peptide. There have been intensive attempts to identify reliable peripheral biomarkers to assess disease progression and onset of specific pathological traits. Mitochondrial dysfunction, altered miRNA expression, endocrine system failure, and impairment of the GABAergic transmission are some of the affectations that are susceptible to be tracked using peripheral blood for monitoring of the motor, cognitive, psychiatric and reproductive impairment of the CGG-expansion carriers. We provided some illustrative examples from our own cohort. Understanding the association between molecular pathogenesis and biomarkers dynamics will improve effective prognosis and clinical management of CGG-expansion carriers.

An Overview of Alternative Splicing Defects Implicated in Myotonic Dystrophy Type I

Myotonic dystrophy type I (DM1) is the most common form of adult muscular dystrophy, caused by expansion of a CTG triplet repeat in the 3′ untranslated region (3′UTR) of the myotonic dystrophy protein kinase (DMPK) gene. The pathological CTG repeats result in protein trapping by expanded transcripts, a decreased DMPK translation and the disruption of the chromatin structure, affecting neighboring genes expression. The muscleblind-like (MBNL) and CUG-BP and ETR-3-like factors (CELF) are two families of tissue-specific regulators of developmentally programmed alternative splicing that act as antagonist regulators of several pre-mRNA targets, including troponin 2 (TNNT2), insulin receptor (INSR), chloride channel 1 (CLCN1) and MBNL2. Sequestration of MBNL proteins and up-regulation of CELF1 are key to DM1 pathology, inducing a spliceopathy that leads to a developmental remodelling of the transcriptome due to an adult-to-foetal splicing switch, which results in the loss of cell function and viability. Moreover, recent studies indicate that additional pathogenic mechanisms may also contribute to disease pathology, including a misregulation of cellular mRNA translation, localization and stability. This review focuses on the cause and effects of MBNL and CELF1 deregulation in DM1, describing the molecular mechanisms underlying alternative splicing misregulation for a deeper understanding of DM1 complexity. To contribute to this analysis, we have prepared a comprehensive list of transcript alterations involved in DM1 pathogenesis, as well as other deregulated mRNA processing pathways implications.

MyomiRNAs and myostatin as physical rehabilitation biomarkers for myotonic dystrophy

MiR-1 and myostatin are markers for muscle growth and regeneration. Myostatin has a key role in the regulation of muscle mass. Myotonic dystrophy type 1(DM1) patients have a disease-specific serum miRNA profile characterized by upregulation of miR-1, miR-206, miR-133a, and miR-133b (myomiRNAs).This study aims to evaluate the possible utility of myomiRs and myostatin as biomarkers of rehabilitation efficacy in DM1, supporting clinical outcomes that are often variable and related to the patient's clinical condition.In 9 genetically proven DM1 patients, we collected biological samples before (T0) and after (T1) exercise rehabilitation training as biological measurement. We measured serum myomiRNAs by qRT-PCR and myostatin by ELISA test. The clinical outcomes measures that we utilized during a 3-6 week rehabilitation controlled aerobic exercise period were the 6-min walking test (6MWT) that increased significantly of 53.5 m (p < 0.0004) and the 10-m walk test (10MWT) that decreased of 1.38 s.We observed, after physical rehabilitation, a significant downregulation of myomiRNAs and myostatin that occurred in parallel with the improvement of clinical functional outcome measures assessed as endurance and gait speed, respectively.The modulation of biomarkers may reflect muscle regeneration and increase muscle mass after aerobic exercise. miRNAs and myostatin might be considered as circulating biomarkers of DM1 rehabilitation. The efficacy of physical rehabilitation in counteracting molecular pathways responsible for muscle atrophy and disease progression and the role of these biomarkers in DM1 and other neuromuscular diseases warrant further investigation.

Sleep Disorders in Four Patients With Myotonic Dystrophy Type 1

Sleep disturbances such as excessive daytime sleepiness, central and obstructive sleep apneas, restless legs syndrome, and rapid eye movement sleep dysregulation are prominent in patients with myotonic dystrophy type 1 (DM1). Mild intellectual deficits presented in many patients with DM1. In addition, psychosocial issues caused by neuropsychiatric symptoms are a clinical problem. We herein present the cases of four DM1 patients with sleep disturbances and neuropsychiatric symptoms in the preceding stage of clinically significant muscle symptoms. One of the cases exhibited a sleep disorder and neuropsychiatric symptoms before electromyography showed myotonic discharge, suggesting that careful follow-up is also important. Patients 1 and 2 were first referred to our department due to daytime sleepiness. Patients 3 and 4 were objectively suffering from daytime sleepiness of which they were not subjectively aware of. Patients 1, 3, and 4 obtained high apnea–hypopnea index (AHI) scores, which reflected central and/or obstructive apnea, whereas patient 2 had an AHI score of zero. The daytime cerebrospinal fluid (CSF) orexin levels of all patients ranged from the normal lower limit to low, although they were not as low as those observed in narcolepsy with typical cataplexy. Neuropsychological tests of patients 1 and 2 showed frontal lobe dysfunction. Patients 3 and 4 were diagnosed with mild intellectual disability and autism spectrum disorder, respectively. All patients exhibited indifference toward their own symptoms, which may have resulted from the cognitive decline caused by DM1. Based on family history and/or neurological findings such as myotonia, we suspected DM1 as the cause of their sleep disturbances. Molecular analysis using the triplet repeat-primed polymerase chain reaction (TP PCR) method and Southern blotting, which provided a genetic confirmation of the diagnosis of DM1, were performed. These clinical features of sleep disturbances were unrelated to the length of CTG repeats and are caused by unknown molecular mechanisms. Clinicians should take into account that multisystem involvement in DM1 is hugely variable, and thus, a disabling sleep disorder could overshadow muscle impairment in DM1 patients.

MRI of trunk muscles and motor and respiratory function in patients with myotonic dystrophy type 1

Background

Myotonic Dystrophy 1 (DM1) causes progressive myopathy of extremity muscles. DM1 may also affect muscles of the trunk. The aim of this study was to investigate fat infiltration and muscle size in trunk muscles in DM1 patients, and in an age and gender matched control group. Further, explore how fat infiltration and degree of atrophy in these muscles are associated with motor and respiratory function in DM1 patients.

Method

We measured fat infiltration and trunk muscle size by MRI in 20 patients with genetically confirmed classic form of DM1, and compared these cases with 20 healthy, age and gender matched controls. In the DM1 group, we investigated correlations between MRI findings and clinical measures of muscle strength, mobility and respiration. We used sum scores for fat infiltration and muscle size in trunk flexors and trunk extensors in the analysis of group differences and correlations.

Results

Significant differences between cases and controls were present for fat infiltration in trunk flexors (p = 0.001) and trunk extensors (p = < 0.001), and for muscle size in trunk flexors (p = 0.002) and trunk extensors (p = 0.030). Fat infiltration in trunk flexors were significant correlated to back extension strength (rho = − 0.523 p = 0.018), while muscle size in trunk flexors was significantly correlated to trunk flexion strength (rho = 0.506 p = 0.023). Fat infiltration in trunk flexors was significantly correlated with lower general mobility (rho = − 0.628, p = 0.003), reduced balance (rho = 0.630, p < 0.003) and forced vital capacity (rho − 0.487 p = 0.040).

Conclusions

Trunk muscles in DM1 patients had significant higher levels of fat infiltration and reduced muscle size compared to age and gender matched controls. In DM1 patients, fat infiltration was associated with reduced muscle strength, mobility, balance and lung function, while muscle size was associated with reduced muscle strength and lung function. These findings are of importance for clinical management of the disease and could be useful additional outcome measures in future intervention studies.

Electronic supplementary material

The online version of this article (10.1186/s12883-019-1357-8) contains supplementary material, which is available to authorized users.

Robust and accurate detection and sizing of repeats within the DMPK gene using a novel TP-PCR test

Myotonic dystrophy type 1 is a multisystem disorder caused by the expansion of a trinucleotide repeat in the DMPK gene. In this study we evaluated the performance of the FastDM1^TMDMPK sizing kit in myotonic dystrophy type 1 testing. This commercially available triplet repeat-primed PCR based kit was validated using reference and clinical samples. Based on testing with 19 reference samples, the assay yielded repeat sizes within three repeats from the consensus reference length, demonstrating an accuracy of 100%. Additionally, the assay generated consistent repeat size information with a concentration range of template-DNA, and upon repetition and reproduction (CV 0.36% to 0.41%). Clinical performance was established with 235 archived prenatal and postnatal clinical samples, yielding results of 100% sensitivity (95% CI, 97.29% to 100%) and 100% specificity (95% CI, 96.19% to 100%) in classifying the samples into the respective genotype groups of 5–35 (normal), 36–50 (non-pathogenic pre-expansion), 51–150 (unstable intermediate-sized pathogenic) or >150 (unstable pathogenic) CTG repeats, respectively. Furthermore, the assay identified interrupted repeat expansions in all samples known to have interruptions, and also identified interruptions in a subset of the clinical samples.

Body composition analysis in patients with myotonic dystrophy types 1 and 2

INTRODUCTION

To date, there are only several reports on body composition in myotonic dystrophy type 1 (DM1) and there are no data for myotonic dystrophy type 2 (DM2). The aim was to analyze body composition of patients with DM1 and DM2, and its association with socio-demographic and clinical features of the diseases.

METHODS

There were no statistical differences in sociodemographic features between 20 DM1 patients and 12 DM2 patients. Body composition was assessed by DEXA (dual-energy x-ray absorptiometry). A three-compartment model was used: bone mineral content (BMC), fat mass (FM), and lean tissue mass (LTM).

RESULTS

Patients with DM1 and DM2 had similar total body mass (TBM), BMC, FM, and LTM. Patients with DM1 had higher trunk-limb fat index (TLFI) in comparison to DM2 patients which indicates visceral fat deposition in DM1 (1.16 ± 0.32 for DM1 vs. 0.87 ± 0.23 for DM2, p < 0.05). Right ribs bone mineral density was lower in DM2 group (0.68 ± 0.07 g/cm² vs. 0.61 ± 0.09 g/cm², p < 0.05). Higher percentage of FM in legs showed correlation with lower strength of the upper leg muscles in DM1 (ρ = - 0.47, p < 0.05). Higher muscle strength in DM2 patients was in correlation with higher bone mineral density (ρ = + 0.62, p < 0.05 for upper arm muscles, ρ = + 0.87, p < 0.01 for lower arm muscles, ρ = + 0.72, p < 0.05 for lower leg muscles).

CONCLUSION

DM1 patients had visceral obesity, and percentage of FM correlated with a degree of muscle weakness in upper legs. In DM2 patients, degree of muscle weakness was in correlation with higher FM index and lower bone mineral density.

A game of hide and seq: Identification of parallel Y-STR evolution in deep-rooting pedigrees

Short tandem repeats on the Y-chromosome (Y-STRs) are common DNA polymorphisms useful for genetic genealogy, population and evolutionary genetics, human genetics, pathology and forensic sciences. It is important to identify all Y-STR variants and to have knowledge of Y-STR mutation rates in order to correctly estimate the time to the most recent common ancestor (tMRCA) between paternally related individuals. When capillary electrophoresis (CE) is performed to analyze genealogical pairs, Y-STR sequence variations remain hidden when the number of repeats is identical. These hidden variations could be due to parallel Y-STR changes or modifications (PM) that occur independently in different lineages leading to alleles with identical number of repeats. In this study, we detect for the first time twelve PM by analyzing 133 males (960 meiosis) in extended deep-rooting family pedigrees on 42 Y-STRs. These PM were observed in nine Y-STR loci with mutation rates of at least 5.94 × 10^-3 per generation. Sequencing analysis made it possible to distinguish insertions/deletions in different repeat regions revealing the presence of two unique changes in three PM on rapidly mutating and complex Y-STRs DYS724-ab and DYS518. Sequencing unraveled more information concerning the identity of alleles, and increased allelic discrimination possibilities which is of great importance in population genetics and forensic analysis. Limiting the analysis to CE could lead to wrong ancestral allele assumptions, to false negative interpretations and to tMRCA underestimations. These observations highlight the importance and added value of sequencing analysis and suggest a shift in genotyping methods from CE to next generation sequencing.

Efficient CRISPR/Cas9-mediated editing of trinucleotide repeat expansion in myotonic dystrophy patient-derived iPS and myogenic cells

CRISPR/Cas9 is an attractive platform to potentially correct dominant genetic diseases by gene editing with unprecedented precision. In the current proof-of-principle study, we explored the use of CRISPR/Cas9 for gene-editing in myotonic dystrophy type-1 (DM1), an autosomal-dominant muscle disorder, by excising the CTG-repeat expansion in the 3'-untranslated-region (UTR) of the human myotonic dystrophy protein kinase (DMPK) gene in DM1 patient-specific induced pluripotent stem cells (DM1-iPSC), DM1-iPSC-derived myogenic cells and DM1 patient-specific myoblasts. To eliminate the pathogenic gain-of-function mutant DMPK transcript, we designed a dual guide RNA based strategy that excises the CTG-repeat expansion with high efficiency, as confirmed by Southern blot and single molecule real-time (SMRT) sequencing. Correction efficiencies up to 90% could be attained in DM1-iPSC as confirmed at the clonal level, following ribonucleoprotein (RNP) transfection of CRISPR/Cas9 components without the need for selective enrichment. Expanded CTG repeat excision resulted in the disappearance of ribonuclear foci, a quintessential cellular phenotype of DM1, in the corrected DM1-iPSC, DM1-iPSC-derived myogenic cells and DM1 myoblasts. Consequently, the normal intracellular localization of the muscleblind-like splicing regulator 1 (MBNL1) was restored, resulting in the normalization of splicing pattern of SERCA1. This study validates the use of CRISPR/Cas9 for gene editing of repeat expansions.

Can Human Pluripotent Stem Cell-Derived Cardiomyocytes Advance Understanding of Muscular Dystrophies?

Muscular dystrophies (MDs) are clinically and molecularly a highly heterogeneous group of single-gene disorders that primarily affect striated muscles. Cardiac disease is present in several MDs where it is an important contributor to morbidity and mortality. Careful monitoring of cardiac issues is necessary but current management of cardiac involvement does not effectively protect from disease progression and cardiac failure. There is a critical need to gain new knowledge on the diverse molecular underpinnings of cardiac disease in MDs in order to guide cardiac treatment development and assist in reaching a clearer consensus on cardiac disease management in the clinic. Animal models are available for the majority of MDs and have been invaluable tools in probing disease mechanisms and in pre-clinical screens. However, there are recognized genetic, physiological, and structural differences between human and animal hearts that impact disease progression, manifestation, and response to pharmacological interventions. Therefore, there is a need to develop parallel human systems to model cardiac disease in MDs. This review discusses the current status of cardiomyocytes (CMs) derived from human induced pluripotent stem cells (hiPSC) to model cardiac disease, with a focus on Duchenne muscular dystrophy (DMD) and myotonic dystrophy (DM1). We seek to provide a balanced view of opportunities and limitations offered by this system in elucidating disease mechanisms pertinent to human cardiac physiology and as a platform for treatment development or refinement.

Prospective measurement of quality of life in myotonic dystrophy type 1

INTRODUCTION

Generic patient reported outcome measures have had varied success in tracking QoL in myotonic dystrophy type 1 (DM1).

AIM

To analyze changes of Individualized Neuromuscular Quality of Life questionnaire (INQoL) scores in clinic patients with DM1 over a 6-year period.

METHOD

Patients completed the INQoL at baseline and after a 6-year period through their attendance in a neurology outpatient clinic. Severity of muscular involvement in DM1 was analyzed using the Muscular Impairment Rating Scale (MIRS).

RESULTS

Ninety-nine DM1 patients completed a baseline visit. Sixty-seven of these patients were retested at an interval time. The overall INQoL score improved in our sample of patients (P<.05) as did the following subscales: myotonia (P<.05), pain (P<.05), activities (P<.01), social relationships (P<.01), and body image (P<.05). No changes were observed for the independence and emotions scales. There were no differences in mean change of INQoL scores between patients with worsened MIRS and those with no change in MIRS scale after follow-up (P>.05).

CONCLUSION

Individualized Neuromuscular Quality of Life questionnaire scores improved in our cohort of DM1 patients during a 6-year period. INQoL score did not correlate with progression of muscle weakness. This must be better understood before the selection of the instrument for use in trials to measure therapeutic benefit in DM1 patients.

RNA-binding proteins in neurodegeneration: mechanisms in aggregate

Neurodegeneration is a leading cause of death in the developed world and a natural, albeit unfortunate, consequence of longer-lived populations. Despite great demand for therapeutic intervention, it is often the case that these diseases are insufficiently understood at the basic molecular level. What little is known has prompted much hopeful speculation about a generalized mechanistic thread that ties these disparate conditions together at the subcellular level and can be exploited for broad curative benefit. In this review, we discuss a prominent theory supported by genetic and pathological changes in an array of neurodegenerative diseases: that neurons are particularly vulnerable to disruption of RNA-binding protein dosage and dynamics. Here we synthesize the progress made at the clinical, genetic, and biophysical levels and conclude that this perspective offers the most parsimonious explanation for these mysterious diseases. Where appropriate, we highlight the reciprocal benefits of cross-disciplinary collaboration between disease specialists and RNA biologists as we envision a future in which neurodegeneration declines and our understanding of the broad importance of RNA processing deepens.

Magnetic resonance imaging of leg muscles in patients with myotonic dystrophies

Magnetic resonance imaging (MRI) of muscles has recently become a significant diagnostic procedure in neuromuscular disorders. There is a lack of muscle MRI studies in patients with myotonic dystrophy type 1 (DM1), especially type 2 (DM2). To analyze fatty infiltration of leg muscles, using 3.0 T MRI in patients with genetically confirmed DM1 and DM2 with different disease durations. The study comprised 21 DM1 and 10 DM2 adult patients. Muscle MRI was performed in axial plane of the lower limbs using T1-weighted (T1w) sequence. Six-point scale by Mercuri et al. was used. Fatty infiltration registered in at least one muscle of lower extremities was found in 71% of DM1 and 40% of DM2 patients. In DM1 patients, early involvement of the medial head of gastrocnemius and tibialis anterior muscles was observed with later involvement of other lower leg muscles and of anterior and posterior thigh compartments with relative sparing of the rectus femoris. In DM2, majority of patients had normal MRI findings. Early involvement of lower legs and posterior thighs was found in some patients. Less severe involvement of the medial head of the gastrocnemius compared to other lower leg muscles was also observed, while involvement of proximal muscles was rather diffuse than selective. It seems that both in DM1 and DM2 some muscles may be affected before weakness is clinically noted and vice versa. We described characteristic pattern and way of progression of muscle involvement in DM1 and DM2.

Myotonic dystrophy type 1: role of CCG, CTC and CGG interruptions within DMPK alleles in the pathogenesis and molecular diagnosis

Myotonic dystrophy type 1 (DM1) is a multisystem neuromuscular disease caused by a CTG triplet expansion in the 3'-untranslated region (3'-UTR) of DMPK gene. This CTG array is usually uninterrupted in both healthy and DM1 patients, but recent studies identified pathological variant expansions containing unstable CCG, CTC and CGG interruptions with a prevalence of 3-5% of cases. In this review, we will describe the clinical, molecular and genetic issues related to the occurrence of variant expansions associated with DM1. Indeed, the identification of these complex DMPK alleles leads to practical consequences in DM1 genetic counseling and testing, because these exams can give false negative results. Moreover, DM1 patients carrying interrupted alleles can manifest either additional atypical neurological symptoms or, conversely, mild, late-onset forms. Therefore, the prognosis of the disease in these patients is difficult to determine because of the great uncertainty about the genotype-phenotype correlations. We will discuss the putative effects of the variant DM1 alleles on the pathogenic disease mechanisms, including mitotic and meiotic repeats instability and splicing alteration typical of DM1 tissues. Interruptions within the DMPK expanded alleles could also interfere with the chromatin structure, the transcriptional activity of the DM1 locus and the interaction with RNA CUG-binding proteins.

Five-year study of quality of life in myotonic dystrophy

Background - Myotonic dystrophy type 1 (DM1) is the most common muscular dystrophy in adults. There is a complete lack of studies that assessed quality of life (QoL) trajectory during time in DM1 cohorts. Aim - To analyze changes of QoL in patients with DM1 during a 5-year follow-up period and to assess responsiveness of the SF-36 questionnaire. Patients and Method - At the baseline, this study comprised 84 DM1 patients, of whom 62 were retested after the mean period of 64.2 ± 3.9 months. Severity of muscular weakness was assessed using the Muscular Impairment Rating Scale (MIRS). Patients completed Serbian version of the SF-36 questionnaire as a measure of health-related QoL. Results - After 5 years, MIRS score of our DM1 patients showed significant progression of 0.5 grade (P < 0.01). All mental subdomains, role physical, and total SF-36 scores significantly improved after 5 years (P < 0.01). Unexpectedly, worsening of muscular weakness from mild to severe was in association with improvement of QoL. Conclusion - QoL improved in our cohort of DM1 patients during a 5-year period despite the progression of the disease. SF-36 should be used with caution as a patient-reported outcome measure in DM1 clinical trials.

Quality of life in patients with myotonic dystrophy type 2

AIM

To analyze quality of life (QoL) in a large cohort of myotonic dystrophy type 2 (DM2) patients in comparison to DM1 control group using both generic and disease specific questionnaires. In addition, we intended to identify different factors that might affect QoL of DM2 subjects.

PATIENTS AND METHOD

49 DM2 patients were compared with 42 adult-onset DM1 patients. Patients completed SF-36 questionnaire and individualized neuromuscular quality of life questionnaire (INQoL). Following measures were also included: Medical Research Council 0-5 point scale for muscle strength, Addenbrooke's cognitive examination revised for cognitive status, Hamilton rating scale for depression, Krupp's fatigue severity scale and daytime sleepiness scale (DSS) RESULTS: SF-36 total score and physical composite score did not differ between DM1 and DM2 patients (p>0.05). However, role emotional and mental composite score were better in DM2 (p<0.05). INQoL total score was similar in both groups (p>0.05), although DM2 patients showed less impairment in independence (p<0.05) and body image domains (p<0.01). Regarding symptoms assessed by INQoL, DM2 patients showed less severe complaint of myotonia (p<0.01). Multiple linear regression analysis showed that significant predictors of worse QoL in DM2 patients were older age, worse muscle strength and higher level of fatigue.

CONCLUSION

QoL reports of DM2 patients with the most severe form of the disease are comparable to those of DM1 patients. Special attention of clinicians should be paid to DM2 patients with older age, more severe muscle weakness and higher level of fatigue since they may be at higher risk to have worse QoL.

Spinocerebellar ataxia type 36 in the Han Chinese

Objective:

To ascertain the genetic and clinical characteristics of the GGCCTG hexanucleotide repeat expansion in the nucleolar protein 56 gene (NOP56) in patients with spinocerebellar ataxia (SCA), sporadic ataxia, or amyotrophic lateral sclerosis (ALS) in Taiwan.

Methods:

We conducted clinical and molecular genetic studies of 109 probands with molecularly unassigned SCA from 512 SCA pedigrees, 323 healthy controls, 502 patients with sporadic ataxia syndromes, and 144 patients with ALS. Repeat-primed PCR assays and PCR-fragment analysis for the number of short hexanucleotide repeats (<40 units) were performed to ascertain NOP56 hexanucleotide repeat expansion. Genotyping included 8 microsatellite markers and 17 single nucleotide polymorphisms flanking NOP56 and covering a region of 1.8 Mb to assess a possible founder effect.

Results:

Eleven individuals from 3 SCA pedigrees have the NOP56 repeat expansions. The 3 pedigrees share a common haplotype spanning 5.3 kb flanking the NOP56 repeat expansions, suggesting a founder effect of spinocerebellar ataxia type 36 (SCA36) in the Han Chinese. The average age at symptom onset was 44.8 ± 3.8 years with truncal ataxia as the initial manifestation. Common features included slowly progressive truncal/limb ataxia, dysarthria, generalized hyperreflexia, and hearing impairment. Evidence of lower motor neuron involvement, including atrophy and fasciculation in the limb muscles and tongue, was mostly found in patients with prolonged disease duration. NOP56 repeat expansion was not detected in controls or patients with sporadic ataxic syndromes or ALS.

Conclusions:

SCA36 is an uncommon subtype, which accounted for 0.6% (3/512) of SCA cases in the Han Chinese population.

Clinical, pathological and genetic characteristics of a pedigree with myotonic dystrophy type 1

The aim of the present study was to investigate the clinical, pathological and molecular genetic characteristics of a pedigree with myotonic dystrophy type 1 (DM1). A series of clinical data from a pedigree with DM1 were collected. Muscle biopsy revealed a typical nuclear ingression within numerous muscle fibers following hematoxylin and eosin staining. Genomic DNA was extracted from the venous blood of two patients and the triplet-primed polymerase chain reaction method was performed to amplify the dystrophia myotonic protein kinase (DMPK) gene. The amplified products were subjected to gene sequencing by capillary fluorescence electrophoresis, and a pathogenic mutation in the DMPK gene comprising >50 cytosine-thymine-guanine repeat sequences was found. DM1 includes multi-system damage, as well as skeletal muscle involvement, and can affect the central nervous system, endocrine glands, skin and heart. A skeletal muscle biopsy and genetic testing can confirm the diagnosis and clarify the severity of the disease. In addition, it is necessary to distinguish DM1 from DM2.

Elevated Muscle-Specific miRNAs in Serum of Myotonic Dystrophy Patients Relate to Muscle Disease Progress

The discovery of reliable and sensitive blood biomarkers is useful for the diagnosis, monitoring and potential future therapy of diseases. Recently, microRNAs (miRNAs) have been identified in blood circulation and might have the potential to be used as biomarkers for several diseases and clinical conditions. Myotonic Dystrophy type 1 (DM1) is the most common form of adult-onset muscular dystrophy primarily characterized by muscle myotonia, weakness and atrophy. Previous studies have shown an association between miRNAs and DM1 in muscle tissue and, recently, in plasma. The aim of this study was to detect and assess muscle-specific miRNAs as potential biomarkers of DM1 muscle wasting, an important parameter in the disease’s natural history. Disease stable or progressive DM1 patients with muscle weakness and wasting were recruited and enrolled in the study. RNA isolated from participants’ serum was used to assess miRNA levels. Results suggest that the levels of muscle-specific miRNAs are correlated with the progression of muscle wasting and weakness observed in the DM1 patients. Specifically, miR-1, miR-133a, miR133b and miR-206 serum levels were found elevated in DM1 patients with progressive muscle wasting compared to disease stable DM1 patients. Based on these results, we propose that muscle-specific miRNAs might be useful molecular biomarkers for monitoring the progress of muscle atrophy in DM1 patients.

Significant impact of behavioral and cognitive impairment on quality of life in patients with myotonic dystrophy type 1

OBJECTIVE

To assess an impact of cognitive and behavioral impairment on QoL in a larger cohort of patients with DM1.

METHODS

Sixty six genetically confirmed DM1 patients (22 with juvenile (jDM1) and 44 with adult form (aDM1) of the disease) were recruited. Following behavioral tests were used: Hamilton scales for depression and anxiety (HamD and HamA), Daytime Sleepiness Scale (DSS), and Krupp's Fatigue Severity Scale (FSS). Patients also underwent detailed classic neuropsychological investigation and Cambridge Neuropsychological Test Automated Battery (CANTAB). Individualized Neuromuscular Quality of Life questionnaire (INQoL) was used as a measure of QoL.

RESULTS

Patients with jDM1 scored lower than aDM1 patients regarding total INQoL score and all INQoL subdomains, except for myotonia. Significant predictors of total INQoL score in patients with jDM1 were severity of fatigue (β=+0.60, p<0.01) and percentage of correct responses on Spatial Recognition Memory test from CANTAB that measures visuospatial abilities (β=-0.38, p<0.05). The most important predictors of total INQoL score in patients with aDM1 were severity of fatigue (β=+0.36, p<0.05) and level of education (β=-0.29, p<0.05).

CONCLUSION

Our results showed clear influence of different central manifestations on QoL in patients with both aDM1 and jDM1.

Fuchs endothelial corneal dystrophy in patients with myotonic dystrophy: a case series

PURPOSE

The aim was to report 4 cases of Fuchs endothelial corneal dystrophy (FECD) in patients with an established diagnosis of myotonic dystrophy (DM) and suggest a mechanism for their association based on the known molecular genetics and potential pathophysiological parallels of DM and FECD.

METHODS

We reviewed all available medical records and pathology slides for the 4 reported cases from the Department of Ophthalmology at Oregon Health and Science University's Casey Eye Institute and Devers Eye Institute at the Legacy Good Samaritan Medical Center in Portland, OR.

RESULTS

Four patients were found to have DM and bilateral corneal guttae, consistent with the diagnosis of FECD. All the identified patients were female and were aged between 34 and 63, and 2 patients were related (mother and daughter). The corneal specimens from 2 of the 4 patients who had undergone a corneal transplant were pathologically confirmed to be consistent with the diagnosis of FECD.

CONCLUSIONS

To our knowledge, FECD has not been previously reported in association with DM. Because both diseases are somewhat prevalent in the United States, it is possible that their coexistence is merely a coincidence in these patients. However, recent studies into the pathogenesis of each disease have shown more parallels between FECD and DM, suggesting the possibility of a noncoincidental association. Potential mutual pathogenic mechanisms may involve altered protein expression causing the deregulation of ion homeostasis, an unstable intronic trinucleotide repeat expansion, or activation of the unfolded protein response and oxidative stress pathways.

Molecular testing for fragile X: analysis of 5062 tests from 1105 fragile X families--performed in 12 clinical laboratories in Spain

Fragile X syndrome is the most common inherited form of intellectual disability. Here we report on a study based on a collaborative registry, involving 12 Spanish centres, of molecular diagnostic tests in 1105 fragile X families comprising 5062 individuals, of whom, 1655 carried a full mutation or were mosaic, three cases had deletions, 1840 had a premutation, and 102 had intermediate alleles. Two patients with the full mutation also had Klinefelter syndrome. We have used this registry to assess the risk of expansion from parents to children. From mothers with premutation, the overall rate of allele expansion to full mutation is 52.5%, and we found that this rate is higher for male than female offspring (63.6% versus 45.6%; P < 0.001). Furthermore, in mothers with intermediate alleles (45–54 repeats), there were 10 cases of expansion to a premutation allele, and for the smallest premutation alleles (55–59 repeats), there was a 6.4% risk of expansion to a full mutation, with 56 repeats being the smallest allele that expanded to a full mutation allele in a single meiosis. Hence, in our series the risk for alleles of <59 repeats is somewhat higher than in other published series. These findings are important for genetic counselling.

Impaired pre-mRNA processing and altered architecture of 3' untranslated regions contribute to the development of human disorders

The biological fate of each mRNA and consequently, the protein to be synthesised, is highly dependent on the nature of the 3' untranslated region. Despite its non-coding character, the 3' UTR may affect the final mRNA stability, the localisation, the export from the nucleus and the translation efficiency. The conserved regulatory sequences within 3' UTRs and the specific elements binding to them enable gene expression control at the posttranscriptional level and all these processes reflect the actual state of the cell including proliferation, differentiation, cellular stress or tumourigenesis. Through this article, we briefly outline how the alterations in the establishment and final architecture of 3' UTRs may contribute to the development of various disorders in humans.