Evaluation of Index of Cardiac Electrophysiological Balance in Patients With Myotonic Dystrophy Type 1

BACKGROUND

Myotonic dystrophy type 1(MD1), which is characterized by decreased muscle tone, progressive muscle weakness, and cardiac involvement, is an autosomal dominant and progressive congenital muscle disease. Cardiac involvement more often manifests as conduction abnormalities and arrhythmias (such as supraventricular or ventricular). Approximately one-third of MD1-related deaths occur due to cardiac causes. The index of cardiac-electrophysiological balance (ICEB) is a current parameter calculated as QT interval/QRS duration. The increase in this parameter has been associated with malignant ventricular arrhythmias. In this study, our aim was to compare the ICEB values ​​of MD1 patients and the normal population.

MATERIAL AND METHOD

A total of 62 patients were included in our study. They were divided into two groups - 32 MD patients and 30 controls. The demographic, clinical, laboratory, and electrocardiographic parameters of the two groups were compared.

RESULTS

The median age of the study population was 24 (20-36 IQR), and 36 (58%) of these patients were female. Body mass index was higher in the control group (p = 0.037). While in the MD1 group creatinine kinase was significantly higher (p <0.001), In the control group creatinine, aspartate aminotransferase, alanine aminotransferase, calcium, and lymphocyte levels were significantly higher (p=0.031, p= 0.003, p=0.001, p=0.002, p=0.031, respectively). ICEB [3.96 (3.65-4.46) vs 3.74 (3.49-3.85) p=0.015] and corrected ICEB (ICEBc) [4.48 (4.08-4.92) vs 4.20 (4.03-4.51) p = 0.048] were significantly higher in the MD1 group.

CONCLUSION

In our study, ICEB was found to be higher in MD1 patients than in the control group. Increased ICEB and ICEBc values ​​in MD1 patients may precipitate ventricular arrhythmias in the future. Close monitoring of these parameters can be helpful in predicting possible ventricular arrhythmias and in risk stratification.

Automatic Text-Mining Approach to Identify Molecular Target Candidates Associated with Metabolic Processes for Myotonic Dystrophy Type 1

Myotonic dystrophy type 1 (DM1) is an autosomal dominant hereditary disease caused by abnormal expansion of unstable CTG repeats in the 3' untranslated region of the myotonic dystrophy protein kinase (DMPK) gene. This disease mainly affects skeletal muscle, resulting in myotonia, progressive distal muscle weakness, and atrophy, but also affects other tissues and systems, such as the heart and central nervous system. Despite some studies reporting therapeutic strategies for DM1, many issues remain unsolved, such as the contribution of metabolic and mitochondrial dysfunctions to DM1 pathogenesis. Therefore, it is crucial to identify molecular target candidates associated with metabolic processes for DM1. In this study, resorting to a bibliometric analysis, articles combining DM1, and metabolic/metabolism terms were identified and further analyzed using an unbiased strategy of automatic text mining with VOSviewer software. A list of candidate molecular targets for DM1 associated with metabolic/metabolism was generated and compared with genes previously associated with DM1 in the DisGeNET database. Furthermore, g:Profiler was used to perform a functional enrichment analysis using the Gene Ontology (GO) and REAC databases. Enriched signaling pathways were identified using integrated bioinformatics enrichment analyses. The results revealed that only 15 of the genes identified in the bibliometric analysis were previously associated with DM1 in the DisGeNET database. Of note, we identified 71 genes not previously associated with DM1, which are of particular interest and should be further explored. The functional enrichment analysis of these genes revealed that regulation of cellular metabolic and metabolic processes were the most associated biological processes. Additionally, a number of signaling pathways were found to be enriched, e.g., signaling by receptor tyrosine kinases, signaling by NRTK1 (TRKA), TRKA activation by NGF, PI3K-AKT activation, prolonged ERK activation events, and axon guidance. Overall, several valuable target candidates related to metabolic processes for DM1 were identified, such as NGF, NTRK1, RhoA, ROCK1, ROCK2, DAG, ACTA, ID1, ID2 MYOD, and MYOG. Therefore, our study strengthens the hypothesis that metabolic dysfunctions contribute to DM1 pathogenesis, and the exploitation of metabolic dysfunction targets is crucial for the development of future therapeutic interventions for DM1.

Fluid Biomarkers of Central Nervous System (CNS) Involvement in Myotonic Dystrophy Type 1 (DM1)

Myotonic dystrophy type 1 (DM1), commonly known as Steinert's disease (OMIM #160900), is the most common muscular dystrophy among adults, caused by an unstable expansion of a CTG trinucleotide repeat in the 3' untranslated region (UTR) of DMPK. Besides skeletal muscle, central nervous system (CNS) involvement is one of the core manifestations of DM1, whose relevant cognitive, behavioral, and affective symptoms deeply affect quality of life of DM1 patients, and that, together with muscle and heart, may profoundly influence the global disease burden and overall prognosis. Therefore, CNS should be also included among the main targets for future therapeutic developments in DM1, and, in this regard, identifying a cost-effective, easily accessible, and sensitive diagnostic and monitoring biomarker of CNS involvement in DM1 represents a relevant issue to be addressed. In this mini review, we will discuss all the papers so far published exploring the usefulness of both cerebrospinal fluid (CSF) and blood-based biomarkers of CNS involvement in DM1. Globally, the results of these studies are quite consistent on the value of CSF and blood Neurofilament Light Chain (NfL) as a biomarker of CNS involvement, with less robust results regarding levels of tau protein or amyloid-beta.

Nuclear envelope transmembrane proteins involved in genome organization are misregulated in myotonic dystrophy type 1 muscle

Myotonic dystrophy type 1 is a multisystemic disorder with predominant muscle and neurological involvement. Despite a well described pathomechanism, which is primarily a global missplicing due to sequestration of RNA-binding proteins, there are still many unsolved questions. One such question is the disease etiology in the different affected tissues. We observed alterations at the nuclear envelope in primary muscle cell cultures before. This led us to reanalyze a published RNA-sequencing dataset of DM1 and control muscle biopsies regarding the misregulation of NE proteins. We could identify several muscle NE protein encoding genes to be misregulated depending on the severity of the muscle phenotype. Among these misregulated genes were NE transmembrane proteins (NETs) involved in nuclear-cytoskeletal coupling as well as genome organization. For selected genes, we could confirm that observed gene-misregulation led to protein expression changes. Furthermore, we investigated if genes known to be under expression-regulation by genome organization NETs were also misregulated in DM1 biopsies, which revealed that misregulation of two NETs alone is likely responsible for differential expression of about 10% of all genes being differentially expressed in DM1. Notably, the majority of NETs identified here to be misregulated in DM1 muscle are mutated in Emery-Dreifuss muscular dystrophy or clinical similar muscular dystrophies, suggesting a broader similarity on the molecular level for muscular dystrophies than anticipated. This shows not only the importance of muscle NETs in muscle health and disease, but also highlights the importance of the NE in DM1 disease progression.

Shedding light on motor premanifest myotonic dystrophy type 1: A molecular, muscular and central nervous system follow-up study

BACKGROUND AND PURPOSE

Myotonic dystrophy type 1 (DM1) is a hereditary and multisystemic disease that is characterized by heterogeneous manifestations. Although muscular impairment is central to DM1, a premanifest DM1 form has been proposed for those characterized by the absence of muscle signs in precursory phases. Nevertheless, subtle signs and/or symptoms related to other systems, such as the central nervous system (CNS), may emerge and progress gradually. This study aimed to validate the premanifest DM1 concept and to characterize and track affected individuals from a CNS centred perspective.

METHODS

Retrospective data of 120 participants (23 premanifest DM1, 25 manifest DM1 and 72 healthy controls) were analysed transversally and longitudinally (over 11.17 years). Compiled data included clinical, neuropsychological and neuroradiological (brain volume and white matter lesion, WML) measures taken at two time points.

RESULTS

Manifest DM1 showed significantly more molecular affectation, worse performance on neuropsychological domains, lower grey and white matter volumes and a different pattern of WMLs than premanifest DM1. The latter was slightly different from healthy controls regarding brain volume and WMLs. Additionally, daytime sleepiness and molecular expansion size explained 50% of the variance of the muscular deterioration at follow-up in premanifest individuals.

CONCLUSIONS

Premanifest DM1 individuals showed subtle neuroradiological alterations, which suggests CNS involvement early in the disease. Based on follow-up data, a debate emerges around the existence of a 'non-muscular DM1' subtype and/or a premanifest phase, as a precursory stage to other DM1 manifestations.

Parkinsonism may aggravate dysphagia in myotonic dystrophy type 1: two case reports

Introduction

Weakness of trunk muscles, fatigue and reduced mobility are features of myotonic dystrophy type 1 (DM1) and may also characterize patients with extrapyramidal disorders.Dysphagia is common in DM1 and parkinsonism and can be predominant compared to other symptom, often requiring surgical tratment.

Methods

We describe two cases of patients with DM1 and parkinsonism who arrived at our Center for worsening dysphagia and who showed very similar and peculiar clinical features.

Case reports

The first patient presented initially at the outpatient clinic reporting a 7 year history of progressive difficulties in swallowing and movement slowness. Neurologic examination showed a general bradykinesia, plastic rigidity of upper limbs, diffuse hypotrophy and deep tendon reflexes weakness. MRI scan of brain and spine was unremarkable, but neurophysiological evaluation revealed diffuse myotonic discharges on distal limb muscles. Genetic testing confirmed DM1 diagnosis (CTG range E1).The second patient, presented with an initial diagnosis of parkinsonism due to a 10 years history of gait impairment, generalized weakness and dysphagia. Due to low back pain a neurophysiological study was performed after 5 years from diagnosis of parkinsonism detecting diffuse myotonic discharges and genetic testing confirmed diagnosis of DM1 (CTG range E2).Percutaneous endoscopic gastrostomy (PEG) was severe and burdensome for both patients.To date, only one case of molecularly confirmed DM1 along with parkinsonism has been described. We have described two cases of DM1 and parkinsonism in which swallowing function has been affected by a synergic effect triggered by both muscle condition and extrapyramidal disease.

Open Bite Malocclusion and Orofacial Dysfunction in Patients with Myotonic Dystrophy Type 1 and Duchenne Muscular Dystrophy

Open bite (OB) is a common malocclusion in individuals with orofacial dysfunction and syndromes, especially in neuromuscular diseases.

OBJECTIVES

The objectives were to explore the prevalence of OB in myotonic dystrophy type 1 (DM1) and Duchenne muscular dystrophy (DMD) and to create and compare orofacial dysfunction profiles.

METHODS

In this database study, 143 individuals with DM1 and 99 with DMD were included. The Mun-H-Center questionnaire and observation chart were used together with the Nordic Orofacial Test -Screening (NOT-S) to create orofacial dysfunction profiles. OB was categorised as: lateral (LOB); anterior (AOB); severe anterior (AOBS); or both types of anterior OB (AOBTot). Descriptive and multivariate statistics were used to compare the OB prevalence and to study associations with orofacial variables, respectively.

RESULTS

There was a statistically significant difference in OB prevalence between the DM1 (37%) and DMD (49%) groups (p = 0.048). LOB was seen in < 1% of DM1 and 18% of DMD. LOB was associated with macroglossia and closed mouth posture, AOB with hypotonic lips, and open mouth posture and AOBS with hypotonic jaw muscles. The orofacial dysfunction profiles showed similar patterns, although the mean NOT-S total scores for DM1 and DMD were 4.2±2.8 (median 4.0, min-max 1-8) and 2.3±2.0 (median 2.0, min-max 0-8), respectively.

LIMITATIONS

The two groups were not age- or gender-matched.

CONCLUSION

OB malocclusion is common in patients with DM1 and DMD and is associated with different types of orofacial dysfunction. This study highlights the need for multi-disciplinary assessments to support tailored treatment strategies that improve or sustain orofacial functions.

[Sleep disorders and fatigue in patients with different forms of myotonic dystrophy type 1]

OBJECTIVE

To characterize sleep disorders in children and adults with different forms of myotonic dystrophy type 1 (DM1), to assess their impact on cognitive functions, excessive daytime sleepiness (EDS) and fatigue, to determine the relationship of EDS, fatigue, and sleep disorders with the quality of life of patients.

MATERIAL AND METHODS

The study included 48 adults and 9 children with confirmed DM1. Patients underwent an assessment of clinical and anamnestic data, neurological, cognitive status, severity of EDS, fatigue, quality of life according to international scales and questionnaires. Polysomnography was performed to identify sleep disorders.

RESULTS

Obstructive sleep apnea syndrome (OSAS) was found in 78% of children and 79.2% of adults. The severity of OSAS in adults, in contrast to children, was influenced by obesity (p<0.001), the severity of muscle weakness (p=0.033), especially the neck muscles (p=0.018). In patients with OSAS and nocturnal hypoxemia, an increase in the duration of the 1st stage of sleep (p=0.008) and in the microactivation index (p=0.005) was revealed. EDS and fatigue were present in 31 (64.6%) and 34 (70.8%) adults, respectively, in 9 (18.8%) they emerged at the onset of the disease. The greater severity of muscle symptoms, anxiety, depression contributed to increased fatigue in adults and the presence of obesity and type 2 diabetes mellitus contributed to EDS. Increased fatigue affects the quality of life to a greater extent than EDS and sleep disturbances.

CONCLUSION

OSAS, the development of which is facilitated by the presence of muscle weakness and obesity, is the leading syndrome among the spectrum of sleep disorders in all age groups. Cognitive and emotional impairments are not the result of sleep apnea, but rather develop because of a primary CNS lesion. The presence of increased fatigue reduced the quality of life of patients.

Recent Progress and Challenges in the Development of Antisense Therapies for Myotonic Dystrophy Type 1

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.

Pneumonia and de novo atrial fibrillation in a patient with myotonic dystrophy type 1: A case report

INTRODUCTION

Myotonic dystrophy type 1 is a rare genetic disorder that mainly affects the musculoskeletal system; However, it may cause several complications in other body systems representing challenges for health care providers.

PATIENT CONCERNS

We present the case of a patient with a history of previously diagnosed type 1 myotonic dystrophy who presented to the emergency department with cough dyspnea, and thoracic pain.

DIAGNOSIS

Differential diagnoses included pulmonary embolism with a moderate probability according to the Wells score, acute coronary syndrome, acute heart failure, and pneumonia. Diagnostic workup involved chest radiography, EKG, and a CTPA which revealed pneumonia, posteriorly the patient presented de novo atrial fibrillation.

INTERVENTIONS

The patient was successfully treated with empiric antibiotic therapy and amiodarone, respiratory and physical therapy.

OUTCOMES

The patient was discharged on day 34, however oxygen weaning was not possible.

CONCLUSION

Treatment of MD1 patients is challenging due to the various mechanisms of the disease; patients with new-onset deterioration should be screened for the most common complications such as cardio-respiratory events.The authors suggest pneumonia as a risk factor for basal respiratory function deterioration and a contributing factor for triggering cardiac events for further research in prospective studies.

A patent and literature review of CDK12 inhibitors

INTRODUCTION

Cyclin-dependent kinase 12 (CDK12) belongs to the CDK family of serine/threonine protein kinases and associates with cyclin K to exert its biological functions, including regulating gene transcription, mRNA processing and translation. Increasing evidences demonstrate the importance of CDK12 in various human cancers, illustrating its potential as both biomarker and therapeutic target. In addition, CDK12 is also a promising target for the treatment of myotonic dystrophy type 1. Efforts have been taken to discover small molecule inhibitors to validate this important therapeutic target.

AREAS COVERED

This review covers the patented CDK12 inhibitors from 2016 to present, as well as these from peer-reviewed literature. It provides the reader an update of the discovery strategies, chemical structures and molecular profiling of all available CDK12 inhibitors.

EXPERT OPINION

CDK12 inhibitors with various mechanism of actions have been discovered and it is a great set of tools to evaluate the therapeutic potential of CDK12 in different disease models. CDK12 inhibitors have shown promising results in myotonic dystrophy type 1 mouse model and several preclinical cancer models either as single agent or combination with other anti-cancer agents. Its therapeutic value awaits more rigorous preclinical testing and further clinical investigation.

Selective and Reversible Ligand Assembly on the DNA and RNA Repeat Sequences in Myotonic Dystrophy

Small molecule targeting of DNA and RNA sequences has come into focus as a therapeutic strategy for diseases such as myotonic dystrophy type 1 (DM1), a trinucleotide repeat disease characterized by RNA gain-of-function. Herein, we report a novel template-selected, reversible assembly of therapeutic agents in situ via aldehyde-amine condensation. Rationally designed small molecule targeting agents functionalized with either an aldehyde or an amine were synthesized and screened against the target nucleic acid sequence. The assembly of fragments was confirmed by MALDI-MS in the presence of DM1-relevant nucleic acid sequences. The resulting hit combinations of aldehyde and amine inhibited the formation of r(CUG)exp in vitro in a cooperative manner at low micromolar levels and rescued mis-splicing defects in DM1 model cells. This reversible template-selected assembly is a promising approach to achieve cell permeable and multivalent targeting via in situ synthesis and could be applied to other nucleic acid targets.

Increased functional connectivity of white-matter in myotonic dystrophy type 1

Background

Myotonic dystrophy type 1 (DM1) is the most common and dominant inherited neuromuscular dystrophy disease in adults, involving multiple organs, including the brain. Although structural measurements showed that DM1 is predominantly associated with white-matter damage, they failed to reveal the dysfunction of the white-matter. Recent studies have demonstrated that the functional activity of white-matter is of great significance and has given us insights into revealing the mechanisms of brain disorders.

Materials and methods

Using resting-state fMRI data, we adopted a clustering analysis to identify the white-matter functional networks and calculated functional connectivity between these networks in 16 DM1 patients and 18 healthy controls (HCs). A two-sample t-test was conducted between the two groups. Partial correlation analyzes were performed between the altered white-matter FC and clinical MMSE or HAMD scores.

Results

We identified 13 white-matter functional networks by clustering analysis. These white-matter functional networks can be divided into a three-layer network (superficial, middle, and deep) according to their spatial distribution. Compared to HCs, DM1 patients showed increased FC within intra-layer white-matter and inter-layer white-matter networks. For intra-layer networks, the increased FC was mainly located in the inferior longitudinal fasciculus, prefrontal cortex, and corpus callosum networks. For inter-layer networks, the increased FC of DM1 patients is mainly located in the superior corona radiata and deep networks.

Conclusion

Results demonstrated the abnormalities of white-matter functional connectivity in DM1 located in both intra-layer and inter-layer white-matter networks and suggested that the pathophysiology mechanism of DM1 may be related to the white-matter functional dysconnectivity. Furthermore, it may facilitate the treatment development of DM1.

Pharmacological and exercise-induced activation of AMPK as emerging therapies for myotonic dystrophy type 1 patients

Myotonic dystrophy type 1 (DM1) is a multisystemic disorder with variable clinical features. Currently, there is no cure or effective treatment for DM1. The disease is caused by an expansion of CUG repeats in the 3' UTR of DMPK mRNAs. Mutant DMPK mRNAs accumulate in nuclei as RNA foci and trigger an imbalance in the level and localization of RNA-binding proteins causing the characteristic missplicing events that account for the varied DM1 symptoms, a disease mechanism referred to as RNA toxicity. In recent years, multiple signalling pathways have been identified as being aberrantly regulated in skeletal muscle in response to the CUG expansion, including AMPK, a sensor of energy status, as well as a master regulator of cellular energy homeostasis. Converging lines of evidence highlight the benefits of activating AMPK signalling pharmacologically on RNA toxicity, as well as on muscle histology and function, in preclinical DM1 models. Importantly, a clinical trial with metformin, an activator of AMPK, resulted in functional benefits in DM1 patients. In addition, exercise, a known AMPK activator, has shown promising effects on RNA toxicity and muscle function in DM1 mice. Finally, clinical trials involving moderate-intensity exercise also induced functional benefits for DM1 patients. Taken together, these studies clearly demonstrate the molecular, histological and functional benefits of AMPK activation and exercise-based interventions on the DM1 phenotype. Despite these advances, several key questions remain; in particular, the extent of the true implication of AMPK in the observed beneficial improvements, as well as how, mechanistically, activation of AMPK signalling improves the DM1 pathophysiology.

Orofacial Manifestations Associated with Muscular Dystrophies: A Review

The aim of this review is to evaluate the developmental, functional, and morphological aspects of the craniofacial complex in patients with myotonic dystrophy type 1 (DM1), Facioscapulohumeral muscular dystrophy (FSHD), and Duchenne muscular dystrophy (DMD). The degree of disease onset and severity varied from patient to patient, and most parameters indicated a greater degree of deterioration in older patients. It was found that all the muscular dystrophies studied showed altered craniofacial morphology, with malocclusion as the most consistent clinical characteristic. Particularly DM1 patients, who are the most studied, showed significant vertical aberration and post-normal occlusion. DMD patients are reported mainly with altered dental arch dimensions which influence functional capacities. Data for FSHD patients are very limited, but facial asymmetry and muscular weakness appear to be the most prominent findings. Patients with muscular dystrophies present deviations in growth and development as well as in orofacial morphology. Increased prevalence of malocclusions, of both skeletal and dental origins, characterize patients with muscular dystrophies. Different dentofacial characteristics are reported among patients with different types of muscular dystrophies. Further research is needed to clarify the orofacial phenotypic expression of muscular dystrophies.

Pseudo-pheochromocytoma due to obstructive sleep apnea: a case report

SUMMARY

Obstructive sleep apnea (OSA) is a condition of intermittent nocturnal upper airway obstruction. OSA increases sympathetic drive which may result in clinical and biochemical features suggestive of pheochromocytoma. We present the case of a 65-year-old male with a 2.9-cm left adrenal incidentaloma on CT, hypertension, symptoms of headache, anxiety and diaphoresis, and persistently elevated 24-h urine norepinephrine (initially 818 nmol/day (89-470)) and normetanephrine (initially 11.2 µmol/day (0.6-2.7)). He was started on prazosin and underwent left adrenalectomy. Pathology revealed an adrenal corticoadenoma with no evidence of pheochromocytoma. Over the next 2 years, urine norepinephrine and normetanephrine remained significantly elevated with no MIBG avid disease. Years later, he was diagnosed with severe OSA and treated with continuous positive airway pressure. Urine testing done once OSA was well controlled revealed complete normalization of urine norepinephrine and normetanephrine with substantial symptom improvement. It was concluded that the patient never had a pheochromocytoma but rather an adrenal adenoma with biochemistry and symptoms suggestive of pheochromocytoma due to untreated severe OSA. Pseudo-pheochromocytoma is a rare presentation of OSA and should be considered on the differential of elevated urine catecholamines and metanephrines in the right clinical setting.

LEARNING POINTS

Obstructive sleep apnea (OSA) is a common condition among adults. OSA may rarely present as pseudo-pheochromocytoma with symptoms of pallor, palpitations, perspiration, headache, or anxiety. OSA should be considered on the differential of elevated urine catecholamines and metanephrines, especially in patients with negative metaiodobenzylguanidine (MIBG) scan results.

Nuclear Envelope Alterations in Myotonic Dystrophy Type 1 Patient-Derived Fibroblasts

Myotonic dystrophy type 1 (DM1) is a hereditary and multisystemic disease characterized by myotonia, progressive distal muscle weakness and atrophy. The molecular mechanisms underlying this disease are still poorly characterized, although there are some hypotheses that envisage to explain the multisystemic features observed in DM1. An emergent hypothesis is that nuclear envelope (NE) dysfunction may contribute to muscular dystrophies, particularly to DM1. Therefore, the main objective of the present study was to evaluate the nuclear profile of DM1 patient-derived and control fibroblasts and to determine the protein levels and subcellular distribution of relevant NE proteins in these cell lines. Our results demonstrated that DM1 patient-derived fibroblasts exhibited altered intracellular protein levels of lamin A/C, LAP1, SUN1, nesprin-1 and nesprin-2 when compared with the control fibroblasts. In addition, the results showed an altered location of these NE proteins accompanied by the presence of nuclear deformations (blebs, lobes and/or invaginations) and an increased number of nuclear inclusions. Regarding the nuclear profile, DM1 patient-derived fibroblasts had a larger nuclear area and a higher number of deformed nuclei and micronuclei than control-derived fibroblasts. These results reinforce the evidence that NE dysfunction is a highly relevant pathological characteristic observed in DM1.

Predicting the CTG Repeat Size from a Single Spirometry Test Performed at Any Time during the Disease Course of Myotonic Dystrophy Type 1

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 <img align="middle" src="./Graphics/abst-61_2281_1.jpg"/>=-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 <img align="middle" src="./Graphics/abst-61_2281_2.jpg"/> 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.

Molecular and Clinical Implications of Variant Repeats in Myotonic Dystrophy Type 1

Myotonic dystrophy type 1 (DM1) is one of the most variable monogenic diseases at phenotypic, genetic, and epigenetic level. The disease is multi-systemic with the age at onset ranging from birth to late age. The underlying mutation is an unstable expansion of CTG repeats in the DMPK gene, varying in size from 50 to >1000 repeats. Generally, large expansions are associated with an earlier age at onset. Additionally, the most severe, congenital DM1 form is typically associated with local DNA methylation. Genetic variability of DM1 mutation is further increased by its structural variations due to presence of other repeats (e.g., CCG, CTC, CAG). These variant repeats or repeat interruptions seem to confer an additional level of epigenetic variability since local DNA methylation is frequently associated with variant CCG repeats independently of the expansion size. The effect of repeat interruptions on DM1 molecular pathogenesis is not investigated enough. Studies on patients indicate their stabilizing effect on DMPK expansions because no congenital cases were described in patients with repeat interruptions, and the age at onset is frequently later than expected. Here, we review the clinical relevance of repeat interruptions in DM1 and genetic and epigenetic characteristics of interrupted DMPK expansions based on patient studies.

Three-dimensional assessment of pharyngeal airway in individuals with myotonic dystrophy type 1

Background/aim

The objectives of this study were to assess pharyngeal airway volume (PAV) in patients with myotonic dystrophy type 1 (DM1) by cone-beam computerized tomography (CBCT) and to evaluate the impact of diaphragm thickness and pulmonary function tests on PAV.

Materials and methods

Thirty DM1 patients (10 female and 20 male; mean age 42.40 ± 12.07) were included in the study. Age and sex-matched thirty patients were participated as control group. In DM1 group pulmonary function tests (PFT) were performed. Independent t-test was used to compare PAV values of patients with DM1 and control group. The Mann–Whitney U test was used to compare the parameters according to sex ( p < 0.05). Pearson and Spearman correlation tests were used to evaluate the relationships between parameters of DM1 patients (p < 0.05). A multiple linear regression analysis was performed to explain the PAV with parameters that showed positive correlation with PAV.

Results

Age of onset and disease duration were 22.37 ± 8.45 and 20.03 ± 12.08, respectively, in patients with DM1. PAV values of control group were significantly lower than DM1 group ( p < 0.001). Forced expiratory volume in 1 s and forced volume vital capacity values were higher in males than females in DM1 group according to sex ( p < 0.001). PAV values were greater in male patients than females of the DM1 group ( p = 0.022). Diaphragm thickness in DM1 group after inspiration and expiration were 2.60 ± 0.65 and 1.94 ± 0.40, respectively. According to the regression analysis, DTai and FVC were significantly explained the PAV.

Conclusion

PAV was higher in DM1 group. There was a significant positive correlation between diaphragm thickness, pulmonary functions, and PAVs of DM1 patients. The amount of the PAV was mostly influenced by DTai and FVC. It is recommended to evaluate the PAV in patients with DM1 because of impaired respiratory functions and pharyngeal muscle involvement.

Altered Local Brain Amplitude of Fluctuations in Patients With Myotonic Dystrophy Type 1

This study is aimed at investigating the characteristics of the spontaneous brain activity in patients with myotonic dystrophy type 1 (DM1). A total of 18 patients with DM1 and 18 healthy controls (HCs) were examined by resting-state functional MRI. Combined methods include amplitude of low-frequency fluctuations (ALFFs), the fractional amplitude of low-frequency fluctuations (fALFFs), and Wavelet transform-based ALFFs (Wavelet-ALFFs) with standardization, percent amplitude of fluctuation (PerAF) with/without standardization were applied to evaluate the spontaneous brain activity of patients with DM1. Compared with HCs, patients with DM1 showed decreased ALFFs and Wavelet-ALFFs in the bilateral precuneus (PCUN), angular gyrus (ANG), inferior parietal, but supramarginal and angular gyri (IPL), posterior cingulate gyrus (PCG), superior frontal gyrus, medial (SFGmed), middle occipital gyrus (MOG), which were mainly distributed in the brain regions of default mode network (DMN). Decreased ALFFs and Wavelet-ALFFs were also seen in bilateral middle frontal gyrus (MFG), inferior frontal gyrus, opercular part (IFGoperc), which were the main components of the executive control network (ECN). Patients with DM1 also showed decreased fALFFs in SFGmed.R, the right anterior cingulate and paracingulate gyri (ACGR), bilateral MFG. Reduced PerAF in bilateral PCUN, ANG, PCG, MOG, and IPLL as well as decreased PerAF without standardization in PCUNR and bilateral PCG also existed in patients with DM1. In conclusion, patients with DM1 had decreased activity in DMN and ECN with increased fluctuations in the temporal cortex and cerebellum. Decreased brain activity in DMN was the most repeatable and reliable with PCUN and PCG being the most specific imaging biomarker of brain dysfunction in patients with DM1.

Drosophila Heart as a Model for Cardiac Development and Diseases

The Drosophila heart, also referred to as the dorsal vessel, pumps the insect blood, the hemolymph. The bilateral heart primordia develop from the most dorsally located mesodermal cells, migrate coordinately, and fuse to form the cardiac tube. Though much simpler, the fruit fly heart displays several developmental and functional similarities to the vertebrate heart and, as we discuss here, represents an attractive model system for dissecting mechanisms of cardiac aging and heart failure and identifying genes causing congenital heart diseases. Fast imaging technologies allow for the characterization of heartbeat parameters in the adult fly and there is growing evidence that cardiac dysfunction in human diseases could be reproduced and analyzed in Drosophila, as discussed here for heart defects associated with the myotonic dystrophy type 1. Overall, the power of genetics and unsuspected conservation of genes and pathways puts Drosophila at the heart of fundamental and applied cardiac research.