Myelin Basic Protein in Oligodendrocyte-Derived Extracellular Vesicles as a Diagnostic and Prognostic Biomarker in Multiple Sclerosis: A Pilot Study.

Approximately 15% of multiple sclerosis (MS) patients develop a progressive form of disease from onset; this condition (primary progressive-PP) MS is difficult to diagnose and treat, and is associated with a poor prognosis. Extracellular vesicles (EVs) of brain origin isolated from blood and their protein cargoes could function as a biomarker of pathological conditions. We verified whether MBP and MOG content in oligodendrocytes-derived EVs (ODEVs) could be biomarkers of MS and could help in the differential diagnosis of clinical MS phenotypes. A total of 136 individuals (7 clinically isolated syndrome (CIS), 18 PPMS, 49 relapsing remitting (RRMS)) and 70 matched healthy controls (HC) were enrolled. ODEVs were enriched from serum by immune-capture with anti-MOG antibody; MBP and MOG protein cargoes were measured by ELISA. MBP concentration in ODEVs was significantly increased in CIS (p < 0.001), RRMS (p < 0.001) and PPMS (p < 0.001) compared to HC and was correlated with disease severity measured by EDSS and MSSS. Notably, MBP concentration in ODEVs was also significantly augmented in PPMS compared to RRMS (p = 0.004) and CIS (p = 0.03). Logistic regression and ROC analyses confirmed these results. A minimally invasive blood test measuring the concentration of MBP in ODEVs is a promising tool that could facilitate MS diagnosis.

Acute and chronic synaptic pathology in multiple sclerosis gray matter.

OBJECTIVES: To investigate the extent of synaptic loss, and the contribution of gray matter (GM) inflammation and demyelination to synaptic loss, in multiple sclerosis (MS) brain tissue. METHODS: This study was performed on two different post-mortem series of MS and control brains, including deep GM and cortical GM. MS brain samples had been specifically selected for the presence of active demyelinating GM lesions. Over 1,000,000 individual synapses were identified and counted using confocal microscopy, and further characterized as glutamatergic/GABAergic. Synaptic counts were also correlated with neuronal/axonal loss. RESULTS: Important synaptic loss was observed in active demyelinating GM lesions (-58.9%), while in chronic inactive GM lesions, synaptic density was only mildly reduced compared to adjacent non-lesional gray matter (NLGM) (-12.6%). Synaptic loss equally affected glutamatergic and GABAergic synapses. Diffuse synaptic loss was observed in MS NLGM compared to control GM (-21.2% overall). CONCLUSION: This study provides evidence, in MS brain tissue, of acute synaptic damage/loss during active GM inflammatory demyelination and of synaptic reorganization in chronically demyelinated GM, affecting equally glutamatergic and GABAergic synapses. Furthermore, this study provides a strong indication of widespread synaptic loss in MS NLGM also independently from focal GM demyelination.

Dietary habits, nutritional status and risk of a first demyelinating event: an incident case-control study in a southern European cohort.

BACKGROUND: The relationship between dietary habits and multiple sclerosis (MS) risk is still controversial. Most studies have involved populations from Scandinavia, North America, and Australia. Data on populations from southern Europe (an area of high MS prevalence) are scarce. OBJECTIVE: To examine the association between dietary habits/nutritional status and risk of a first demyelinating event, in a southern European incident cohort. METHODS: In this incident case-control study, a detailed nutritional assessment was performed by a registered dietitian in patients with a first demyelinating event, and in age-/sex-matched controls. Body composition analysis, anthropometric evaluation, and blood tests for nutritional status were also performed. RESULTS: Eighty-three patients with a first demyelinating event were prospectively recruited over a 1-year period. Low intake of fibers (OR 0.846, p = 0.014), vitamin D (OR 0.730, p < 0.0001), and alpha-linolenic acid (OR 0.283, p = 0.014), high BMI (OR 1.132, p = 0.028), and ever smoker status (OR 4.472, p = 0.003) were all independently associated with risk of a first demyelinating event. Higher intake of rapid absorption carbohydrates, lower intake of vegetal proteins, and higher intake of animal proteins were observed in patients with a first demyelinating event. CONCLUSIONS: Significant differences between patients and controls are observed in the dietary habits at the time of a first demyelinating event, suggesting low intake of fibers, vitamin D and alpha-linolenic acid as the main dietary risk factors. Furthermore, high cardiovascular risk dietary habits are frequent at the time of MS onset, suggesting the usefulness of nutritional intervention as part of the activities of MS centers.

Two Single Nucleotide Polymorphisms in the Purinergic Receptor P2X7 Gene Are Associated with Disease Severity in Multiple Sclerosis.

Multiple sclerosis (MS) is a chronic autoimmune inflammatory disease of the central nervous system (CNS) that leads to progressive physical disability. Recent evidence has suggested that P2X7 receptor (P2X7R)-mediated purinergic signalling pathways play a role in MS-associated neuroinflammation, possibly contributing to disease pathogenesis. To evaluate possible associations between P2X7R polymorphisms and MS disease severity, we performed an association study of five non-synonymous SNPs coding variants of the P2X7R gene: rs1718119 Ala348Thr, rs2230911 Thr357Ser, rs2230912 Gln460Arg, rs3751143 Glu496Ala, and rs28360457 Arg307Gln, modulating P2X7R expression in 128 MS patients (relapsing remitting MS, RRMS: n = 94; secondary progressive, SPMS: n = 34). All patients were genotyped, and multiple sclerosis severity score (MSSS) was evaluated in every case; 189 healthy subjects were enrolled as well as controls. Results showed that P2X7R rs1718119(A) 348Thr and rs22390912(G) 464Arg, two SNPs of minor allele frequency (MAF) known to confer gain of function to the P2X7R protein, were associated with significantly higher MSSS in RRMS patients alone (SMRR (p < 0.001, p = 0.01, respectively)). Interestingly, two whole haplotypes resulted in having significant association with MSSS in these same patients. Thus: (1) the P2X7R-4 "ACGAG" haplotype, characterized by the co-presence of the rs1718119-rs2230912 AG MAF alleles, was associated with higher MSSS (Beta: 1.11 p = 0.04), and (2) the P2X7R-1 "GCAAG" complementary haplotype, which contains the rs1718119 and rs2230912 GA wild-type alleles, was more frequently carried by patients with lower MSSS and less severe disease (Beta: −1.54 p < 0.001). Although being preliminary and needing confirmation in an ampler cohort, these results suggest that 348Thr and 464Arg variants have a role as modulators of disease severity in RRMS patients.

Mutations in INPP5K Cause a Form of Congenital Muscular Dystrophy Overlapping Marinesco-Sjögren Syndrome and Dystroglycanopathy.

Congenital muscular dystrophies display a wide phenotypic and genetic heterogeneity. The combination of clinical, biochemical, and molecular genetic findings must be considered to obtain the precise diagnosis and provide appropriate genetic counselling. Here we report five individuals from four families presenting with variable clinical features including muscular dystrophy with a reduction in dystroglycan glycosylation, short stature, intellectual disability, and cataracts, overlapping both the dystroglycanopathies and Marinesco-Sjögren syndrome. Whole-exome sequencing revealed homozygous missense and compound heterozygous mutations in INPP5K in the affected members of each family. INPP5K encodes the inositol polyphosphate-5-phosphatase K, also known as SKIP (skeletal muscle and kidney enriched inositol phosphatase), which is highly expressed in the brain and muscle. INPP5K localizes to both the endoplasmic reticulum and to actin ruffles in the cytoplasm. It has been shown to regulate myoblast differentiation and has also been implicated in protein processing through its interaction with the ER chaperone HSPA5/BiP. We show that morpholino-mediated inpp5k loss of function in the zebrafish results in shortened body axis, microphthalmia with disorganized lens, microcephaly, reduced touch-evoked motility, and highly disorganized myofibers. Altogether these data demonstrate that mutations in INPP5K cause a congenital muscular dystrophy syndrome with short stature, cataracts, and intellectual disability.

Aging-associated genes and let-7 microRNAs: a contribution to myogenic program dysregulation in oculopharyngeal muscular dystrophy.

Oculopharyngeal muscular dystrophy (OPMD) is a late-onset muscle disease caused by an abnormal (GCN) triplet expansion within the polyadenylate-binding protein nuclear 1 gene and consequent mRNA processing impairment and myogenic defects. Because a reduced cell proliferation potential and the consequent regeneration failure of aging muscle have been shown to be governed by lethal-7 (let-7) microRNA-mediated mechanisms, in the present study, we evaluated the role of let-7 in the pathogenesis of OPMD. By a multidisciplinary approach, including confocal microscopy, Western blot, and quantitative PCR analyses on muscle biopsies from patients and unaffected individuals, we found a significant increase in let-7 expression in OPMD muscles associated with an unusual high percentage of paired box 7-positive satellite cells. Furthermore, IL-6, a cytokine involved in the regulation of satellite cell proliferation and differentiation and a potential target of let-7, was found strongly down-regulated in OPMD compared with control muscles. The decrease in IL-6 transcript levels and protein content was also confirmed in vitro during differentiation of patients' and controls' muscle cells. Overall, our data suggest a key role of let-7 in the regeneration and degeneration process in OPMD muscle and pointed to IL-6 as a potential target molecule for new therapeutic approaches for this disorder.-Cappelletti, C., Galbardi, B., Bruttini, M., Salerno, F., Canioni, E., Pasanisi, M. B., Rodolico, C., Brizzi, T., Mora, M., Renieri, A., Maggi, L., Bernasconi, P., Mantegazza, R. Aging-associated genes and let-7 microRNAs: a contribution to myogenic program dysregulation in oculopharyngeal muscular dystrophy.

Longitudinal evaluation of SMN levels as biomarker for spinal muscular atrophy: results of a phase IIb double-blind study of salbutamol.

BACKGROUND: Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder, due to the loss of function of the survival motor neuron (SMN1) gene. The first treatment for the condition, recently approved, is based on the reduction of exon 7 skipping in mRNAs produced by a highly homologous gene (SMN2). The primary objective of the present study was to evaluate the applicability of the dosage of SMN gene produts in blood, as biomarker for SMA, and the safety of oral salbutamol, a beta2-adrenergic agonist modulating SMN2 levels. METHODS: We have performed a 1-year multicentre, double-blind, placebo-controlled study with salbutamol in 45 adult patients with SMA. Patients assumed 4 mg of salbutamol or placebo/three times a day. Molecular tests were SMN2 copy number, SMN transcript and protein levels. We have also explored the clinical effect, by the outcome measures available at the time of study design. RESULTS: Thirty-six patients completed the study. Salbutamol was safe and well tolerated. We observed a significant and progressive increase in SMN2 full-length levels in peripheral blood of the salbutamol-treated patients (p<0.00001). The exploratory analysis of motor function showed an improvement in most patients. CONCLUSIONS: Our data demonstrate safety and molecular efficacy of salbutamol. We provide the first longitudinal evaluation of SMN levels (both transcripts and protein) in placebo and in response to a compound modulating the gene expression: SMN transcript dosage in peripheral blood is reliable and may be used as pharmacodynamic marker in clinical trials with systemic compounds modifying SMN2levels. TRIAL REGISTRATION NUMBER: EudraCT no. 2007-001088-32.

Perceived efficacy of salbutamol by persons with spinal muscular atrophy: A mixed methods study.

INTRODUCTION: The aim of this study was to assess the perceived effect of salbutamol in adult patients with spinal muscular atrophy and to evaluate the usefulness of the World Health Organization Disability Assessment Schedule II (WHODAS II) and Fatigue Severity Scale (FSS) for its measurement. METHODS: A longitudinal mixed methods study was performed. Ten patients were interviewed and completed WHODAS II and FSS questionnaires to assess disability and fatigue at 2 time-points. Inductive thematic analysis was used for qualitative data. The non-parametric Wilcoxon test was performed for quantitative analysis. RESULTS: All participants reported an improvement in their condition after salbutamol consumption. WHODAS II and FSS reliably captured changes in patients' disability and fatigue. CONCLUSIONS: The mixed methods design allowed us to identify the functional domains in which participants experienced effects of salbutamol. Patients were satisfied with the treatment as shown by decreased fatigue, improved functioning, and infrequent side effects. Muscle Nerve, 2016 Muscle Nerve 54: 843-849, 2016.

A chaperone enhances blood α-glucosidase activity in Pompe disease patients treated with enzyme replacement therapy.

Enzyme replacement therapy is currently the only approved treatment for Pompe disease, due to acid α-glucosidase deficiency. Clinical efficacy of this approach is variable, and more effective therapies are needed. We showed in preclinical studies that chaperones stabilize the recombinant enzyme used for enzyme replacement therapy. Here, we evaluated the effects of a combination of enzyme therapy and a chaperone on α-glucosidase activity in Pompe disease patients. α-Glucosidase activity was analyzed by tandem-mass spectrometry in dried blood spots from patients treated with enzyme replacement therapy, either alone or in combination with the chaperone N-butyldeoxynojirimycin given at the time of the enzyme infusion. Thirteen patients with different presentations (3 infantile-onset, 10 late-onset) were enrolled. In 11 patients, the combination treatment resulted in α-glucosidase activities greater than 1.85-fold the activities with enzyme replacement therapy alone. In the whole patient population, α-glucosidase activity was significantly increased at 12 hours (2.19-fold, P = 0.002), 24 hours (6.07-fold, P = 0.001), and 36 hours (3.95-fold, P = 0.003). The areas under the curve were also significantly increased (6.78-fold, P = 0.002). These results suggest improved stability of recombinant α-glucosidase in blood in the presence of the chaperone.

Quantitative Muscle MRI Protocol as Possible Biomarker in Becker Muscular Dystrophy.

PURPOSE: Aim of this study is to compare Quantitative Magnetic Resonance Imaging (qMRI) measures between Becker Muscular Dystrophy (BMD) and Healthy Subjects (HS) and to correlate these parameters with clinical scores. METHODS: Ten BMD patients (mean age ±standard deviation: 38.7 ± 15.0 years) and ten age-matched HS, were investigated through magnetic resonance imaging (MRI) at thigh and calf levels, including: 1) a standard axial T1-weighted sequence; 2) a volumetric T2-weighted sequence; 3) a multiecho spin-echo sequence; 4) a 2-point Dixon sequence; 5) a Diffusion Tensor Imaging (DTI) sequence. RESULTS: Mean Fat Fraction (FF), T2-relaxation time and Fractional Anisotropy (FA) DTI at thigh and calf levels were significantly higher in BMD patients than in HS (p-values < 0.01). FF at thigh and calf levels significantly correlated with North Star Ambulatory Assessment (NSAA) score (p-values < 0.01) and6 Minutes Walking Test (6MWT) (p-values < 0.01), whereas only calf muscle FF was significantly associated with time to get up from floor (p-value = 0.01). T2 significantly correlated with NSAA score (p-value < 0.01), 6MWT (p-value = 0.02) and time to get up from floor (p-value < 0.01) only at calf level. Among DTI values, only FA in thigh and calf muscles significantly correlated with NSAA score, 6MWT and 10-m walk (all p-values < 0.05); only FA in calf muscles significantly correlated with time to get up from floor (p = 0.01). CONCLUSIONS: Muscle FF, T2-relaxometry and DTI, seem to be a promising biomarker to assess BMD disease severity, although further studies are needed to evaluate changes over the time.

SMA-miRs (miR-181a-5p, -324-5p, and -451a) are overexpressed in spinal muscular atrophy skeletal muscle and serum samples.

Background: Spinal muscular atrophy (SMA) is a neuromuscular disorder characterized by the degeneration of the second motor neuron. The phenotype ranges from very severe to very mild forms. All patients have the homozygous loss of the SMN1 gene and a variable number of SMN2 (generally 2-4 copies), inversely related to the severity. The amazing results of the available treatments have made compelling the need of prognostic biomarkers to predict the progression trajectories of patients. Besides the SMN2 products, few other biomarkers have been evaluated so far, including some miRs. Methods: We performed whole miRNome analysis of muscle samples of patients and controls (14 biopsies and 9 cultures). The levels of muscle differentially expressed miRs were evaluated in serum samples (51 patients and 37 controls) and integrated with SMN2 copies, SMN2 full-length transcript levels in blood and age (SMA-score). Results: Over 100 miRs were differentially expressed in SMA muscle; 3 of them (hsa-miR-181a-5p, -324-5p, -451a; SMA-miRs) were significantly upregulated in the serum of patients. The severity predicted by the SMA-score was related to that of the clinical classification at a correlation coefficient of 0.87 (p<10-5). Conclusions: miRNome analyses suggest the primary involvement of skeletal muscle in SMA pathogenesis. The SMA-miRs are likely actively released in the blood flow; their function and target cells require to be elucidated. The accuracy of the SMA-score needs to be verified in replicative studies: if confirmed, its use could be crucial for the routine prognostic assessment, also in presymptomatic patients. Funding: Telethon Italia (grant #GGP12116).

Exercise training alone or in combination with high-protein diet in patients with late onset Pompe disease: results of a cross over study.

BACKGROUND: Late onset Pompe disease (LOPD) is a lysosomal neuromuscular disorder which can progressively impair the patients' exercise tolerance, motor and respiratory functions, and quality of life. The available enzyme replacement therapy (ERT) does not completely counteract disease progression. We investigated the effect of exercise training alone, or associated with a high-protein diet, on the exercise tolerance, muscle and pulmonary functions, and quality of life of LOPD patients on long term ERT. METHODS: The patients were asked to participate to a crossover randomized study comprehending a control period (free diet, no exercise) followed by 2 intervention periods: exercise or exercise + diet, each lasting 26 weeks and separated by 13 weeks washout periods. Exercise training included moderate-intensity aerobic exercise on a cycle ergometer, stretching and balance exercises, strength training. The diet was composed by 25-30% protein, 30-35% carbohydrate and 35-40% fat. Before and after each period patients were assessed for: exercise tolerance test on a cycle-ergometer, serum muscle enzymes, pulmonary function tests and SF36 questionnaire for quality of life. Compliance was evaluated by training and dietary diaries. Patients were contacted weekly by researchers to optimize adherence to treatments. RESULTS: Thirteen LOPD patients, median age 49 ± 11 years, under chronic ERT (median 6.0 ± 4.0 years) were recruited. Peak aerobic power (peak pulmonary O2 uptake) decreased after control, whereas it increased after exercise, and more markedlyafter exercise + diet. Serum levels of lactate dehydrogenase (LDH) significantly decreased after exercise + diet; both creatine kinase (CK) and LDH levels were significantly reduced after exercise + diet compared to exercise. Pulmonary function showed no changes after control and exercise, whereas a significant improvement of forced expiratory volume in 1 sec (FEV1) was observed after exercise + diet. SF36 showed a slight improvement in the "mental component" scale after exercise, and a significant improvement in "general health" and "vitality" after exercise + diet. The compliance to prescriptions was higher than 70% for both diet and exercise. CONCLUSIONS: Exercise tolerance (as evaluated by peak aerobic power) showed a tendency to decrease in LOPD patients on long term ERT. Exercise training, particularly if combined with high-protein diet, could reverse this decrease and result in an improvement, which was accompanied by improved quality of life. The association of the two lifestyle interventions resulted also in a reduction of muscle enzyme levels and improved pulmonary function.

Amifampridine phosphate in the treatment of muscle-specific kinase myasthenia gravis: a phase IIb, randomized, double-blind, placebo-controlled, double crossover study.

OBJECTIVE: The aim of this study is to determine the safety and the efficacy of amifampridine phosphate in muscle-specific kinase antibody-positive myasthenia gravis, in a 1:1 randomized, double-blind, placebo-controlled, switchback, double crossover study. METHODS: Eligible patients had muscle-specific kinase myasthenia gravis, >18 years of age, and Myasthenia Gravis Foundation of America class II-IV with a score of ⩾9 on Myasthenia Gravis Composite scale. After the run-in phase, during which amifampridine phosphate was titrated to a tolerable and effective dosage, patients were randomized to receive placebo-amifampridine-placebo sequence or amifampridine-placebo-amifampridine sequence daily for 7 days. Then, patients switched treatment arms twice, for a total of 21 days of double-blind treatment. Safety was determined by serial assessments of adverse events/serious adverse events, physical examinations, and clinical and laboratory tests. The co-primary outcome measures included changes from baseline of Quantitative Myasthenia Gravis score and Myasthenia Gravis-specific Activities of Daily Living Profile score. The secondary outcome measures comprised changes from baseline of Myasthenia Gravis Composite score, Myasthenia Gravis Quality of Life scale-15 questions, Fatigue Severity Scale, and Carlo Besta Neurological Institute-Myasthenia Gravis scale. Statistical analyses were assessed using a switchback model for three-period, two-treatment crossover design. RESULTS: A total of 10 patients were screened, enrolled, and treated. Transient paresthesias (60%) were the only amifampridine phosphate-related adverse events reported. Four patients were randomized to receive placebo-amifampridine-placebo sequence and three patients to receive amifampridine-placebo-amifampridine sequence. The co-primary objectives were statistically met (Quantitative Myasthenia Gravis score: p = 0.0003 and Myasthenia Gravis-specific Activities of Daily Living Profile score: p = 0.0006), as well as all the secondary endpoints (Myasthenia Gravis Composite score: p < 0.0001, Myasthenia Gravis Quality of Life scale-15 questions: p = 0.0025, Fatigue Severity Scale: p = 0.0061, and Carlo Besta Neurological Institute-Myasthenia Gravis scale: p = 0.0014). CONCLUSION: Despite the low number of patients, MuSK-001 study provided evidence that amifampridine phosphate, in the range of 30-60 mg daily dose, was safe and effective in treating muscle-specific kinase myasthenia gravis, suggesting the need for a large multi-center trial to confirm these results.

Interpreting Genetic Variants in Titin in Patients With Muscle Disorders.

Importance: Mutations in the titin gene (TTN) cause a wide spectrum of genetic diseases. The interpretation of the numerous rare variants identified in TTN is a difficult challenge given its large size. Objective: To identify genetic variants in titin in a cohort of patients with muscle disorders. Design, Setting, and Participants: In this case series, 9 patients with titinopathy and 4 other patients with possibly disease-causing variants in TTN were identified. Titin mutations were detected through targeted resequencing performed on DNA from 504 patients with muscular dystrophy, congenital myopathy, or other skeletal muscle disorders. Patients were enrolled from 10 clinical centers in April 2012 to December 2013. All of them had not received a diagnosis after undergoing an extensive investigation, including Sanger sequencing of candidate genes. The data analysis was performed between September 2013 and January 2017. Sequencing data were analyzed using an internal custom bioinformatics pipeline. Main Outcomes and Measures: The identification of novel mutations in the TTN gene and novel patients with titinopathy. We performed an evaluation of putative causative variants in the TTN gene, combining genetic, clinical, and imaging data with messenger RNA and/or protein studies. Results: Of the 9 novel patients with titinopathy, 5 (55.5%) were men and the mean (SD) age at onset was 25 (15.8) years (range, 0-46 years). Of the 4 other patients (3 men and 1 woman) with possibly disease-causing TTN variants, 2 (50%) had a congenital myopathy and 2 (50%) had a slowly progressive distal myopathy with onset in the second decade. Most of the identified mutations were previously unreported. However, all the variants, even the already described mutations, require careful clinical and molecular evaluation of probands and relatives. Heterozygous truncating variants or unique missense changes are not sufficient to make a diagnosis of titinopathy. Conclusions and Relevance: The interpretation of TTN variants often requires further analyses, including a comprehensive evaluation of the clinical phenotype (deep phenotyping) as well as messenger RNA and protein studies. We propose a specific workflow for the clinical interpretation of genetic findings in titin.

DNAJB6 Myopathies: Focused Review on an Emerging and Expanding Group of Myopathies.

Mutations in the DNAJB6 gene have been associated with the autosomal dominant limb girdle muscular dystrophy type 1D (LGMD1D), a disorder characterized by abnormal protein aggregates and rimmed vacuoles in muscle fibers. DNAJB6 is a ubiquitously expressed Hsp40 co-chaperone characterized by a J domain that specifies Hsp70 functions in the cellular environment. DNAJB6 is also a potent inhibitor of expanded polyglutamine (polyQ) aggregation preventing aggregate toxicity in cells. In DNAJB6-mutated patients this anti-aggregation property is significantly reduced, albeit not completely lost. To elucidate the pathogenetic mechanisms underlying the DNAJB6-related myopathy, animal models have been created showing that, indeed, conditional muscular expression of a DNAJB6 mutant in the mouse causes a LGMD1D myofibrillary muscle tissue phenotype. Both mutations and phenotypes reported until recently were rather homogeneous, being exclusively missense mutations of a few amino acids of the protein G/F domain, and with a phenotype characterized by adult-onset slowly progressive muscular dystrophy predominantly affecting proximal muscles. Lately, several novel mutations and new phenotypes of DNAJB6 have been described. These mutations once more affect the G/F domain of DNAJB6 with missense changes and a splice site mutation; and the phenotypes include childhood onset and distal involvement of muscles, or childhood-onset LGMD1D with loss of ambulation in early adulthood and respiratory involvement. Thus, the spectrum of DNAJB6-related phenotypes is widening. Although our knowledge about the role of DNAJB6 in the pathogenesis of muscle diseases has made great progression, several questions remain unsolved, including why a ubiquitous protein affects only, or predominantly, skeletal muscle; why only the G/F domain is involved; and what is the possible role of the DNAJB6a isoform. Clarification of these issues will provide clues to implement possible therapeutic strategies for DNAJB6-related myopathies.

Complete loss of the DNAJB6 G/F domain and novel missense mutations cause distal-onset DNAJB6 myopathy.

INTRODUCTION: Protein aggregation is a common cause of neuropathology. The protein aggregation myopathy Limb-Girdle Muscular Dystrophy 1D (LGMD1D) is caused by mutations of amino acids Phe89 or Phe93 of DNAJB6, a co-chaperone of the HSP70 anti-aggregation protein. Another DNAJB6 mutation, Pro96Arg, was found to cause a distal-onset myopathy in one family. RESULTS: We detail the mutational, neuropathological, neurophysiological, neurological and radiological features of five new DNAJB6-myopathy families. One has the known Phe93Leu mutation and classic late-onset slowly progressive LGMD1D. Two have different mutations of Phe91 causing a variant childhood-onset severe limb-girdle myopathy. One has a Phe100Val mutation and distal-onset myopathy, unique early bulbar involvement, and a gender-modified wide age-of-onset range. The last has childhood-onset severe distal-onset myopathy and the first non-missense DNAJB6 mutation, c.346 + 5G > A, causing a splicing defect that entirely eliminates DNAJB6's G/F domain (ΔG/F), the domain that harbours all other mutations. Clinical and imaging examinations reveal that muscles considered uninvolved in DNAJB6-myopathy, e.g. lateral gastrocnemii, are affected in our patients with new mutations. Mutational modelling based on the known structure of the bacterial DNAJ2 protein indicates that all past and present mutated residues cluster within 15 Å in the G/F domain and all disturb the interface of this domain with the protein's J domain that confers the interaction with HSP70. CONCLUSIONS: Our patients expand the phenotypic spectrum of DNAJB6-myopathy and allow tentative genotype-phenotype specifications. Combining with previous studies, the clinical severity spectrum is as follows: ΔG/F and Phe91 mutations, most severe; Phe100, Pro96, Phe89 mutations, intermediate; and Phe93, least severe. As it stands presently, proximal G/F domain mutations (Phe89, Phe91, Phe93) cause proximal limb-girdle myopathy, while distal G/F mutations (Pro96, Phe100) cause distal-onset myopathy. While all mutations affect the G/F-J interaction, each likely does so in different unknown extents or ways. One mutation, ΔG/F, causes its associated severe distal-onset myopathy phenotype in a clear way, through generation of a G/F domain-lacking DNAJB6 protein.

Sleep breathing disorders in 40 Italian patients with Myotonic dystrophy type 1.

The aim of this study was to estimate the prevalence and nature of sleep breathing disorders in Myotonic dystrophy type 1 (DM1). We wanted to determine whether there is a relationship between sleep breathing disorders and clinical parameters such as pulmonary function, degree of neuromuscular impairment, daytime sleepiness, and fatigue. This will help assess the prevalence of DM1 patients requiring nocturnal ventilatory treatments. We studied a random sample of 40 unrelated patients and found that 22/40 patients had obstructive sleep apnoea. Of these 22 patients, five showed also periodic breathing and four showed sleep hypoventilation. Nine patients were put on nocturnal ventilation following clinical and instrumental evaluations. Our study reveals that obstructive sleep apnoea is very common in these patients, but cannot be predicted on the basis of clinical-neurological features and diurnal functional respiratory tests. Our data emphasize that a periodical evaluation by polysomnography should be mandatory to ascertain, and treat if necessary, the presence of obstructive sleep apnoea, periodic breathing or nocturnal hypoventilation.