Objective
To continue evaluation of the long‐term efficacy and safety of eteplirsen, a phosphorodiamidate morpholino oligomer designed to skip DMD exon 51 in patients with Duchenne muscular dystrophy ...(DMD). Three‐year progression of eteplirsen‐treated patients was compared to matched historical controls (HC).
Methods
Ambulatory DMD patients who were ≥7 years old and amenable to exon 51 skipping were randomized to eteplirsen (30/50mg/kg) or placebo for 24 weeks. Thereafter, all received eteplirsen on an open‐label basis. The primary functional assessment in this study was the 6‐Minute Walk Test (6MWT). Respiratory muscle function was assessed by pulmonary function testing (PFT). Longitudinal natural history data were used for comparative analysis of 6MWT performance at baseline and months 12, 24, and 36. Patients were matched to the eteplirsen group based on age, corticosteroid use, and genotype.
Results
At 36 months, eteplirsen‐treated patients (n = 12) demonstrated a statistically significant advantage of 151m (p < 0.01) on 6MWT and experienced a lower incidence of loss of ambulation in comparison to matched HC (n = 13) amenable to exon 51 skipping. PFT results remained relatively stable in eteplirsen‐treated patients. Eteplirsen was well tolerated. Analysis of HC confirmed the previously observed change in disease trajectory at age 7 years, and more severe progression was observed in patients with mutations amenable to exon skipping than in those not amenable. The subset of patients amenable to exon 51 skipping showed a more severe disease course than those amenable to any exon skipping.
Interpretation
Over 3 years of follow‐up, eteplirsen‐treated patients showed a slower rate of decline in ambulation assessed by 6MWT compared to untreated matched HC. Ann Neurol 2016;79:257–271
The aim of the study was to assess different outcome measures in a cohort of ambulant boys with Duchenne muscular dystrophy (DMD) over 12 months in order to establish the spectrum of possible changes ...in relation to age and steroid treatment.
The study is a longitudinal multicentric cohort study. A total of 106 ambulant patients with DMD were assessed using the 6-minute walk test (6MWT) and North Star Ambulatory Assessment (NSAA) at baseline and 12 months. Clinical data including age and steroid treatment were collected.
During the 12 months of the study, we observed a mean decline of 25.8 meters in the 6MWT with a SD of 74.3 meters. On NSAA, the mean decline was 2.2 points with a SD of 3.7. Not all the boys with DMD in our cohort showed a decline over the 12 months, with young boys showing some improvement in their 6MWT and NSAA scores up to the age of 7. NSAA and the 6MWT had the highest correlation (r = 0.52, p < 0.001).
This study provides longitudinal data of NSAA and 6MWT over a 12-month period. These data can be useful when designing a clinical trial.
Aims
Pompe disease is an autosomal recessive lysosomal storage disorder resulting from deficiency of acid α‐glucosidase (GAA) enzyme. Histopathological hallmarks in skeletal muscle tissue are fibre ...vacuolization and autophagy. Since 2006, enzyme replacement therapy (ERT) is the only approved treatment with human recombinant GAA alglucosidase alfa. We designed a study to examine ERT‐related skeletal muscle changes in 18 modestly to moderately affected late onset Pompe disease (LOPD) patients along with the relationship between morphological/biochemical changes and clinical outcomes. Treatment duration was short‐to‐long term.
Methods
We examined muscle biopsies from 18 LOPD patients at both histopathological and biochemical level. All patients underwent two muscle biopsies, before and after ERT administration respectively. The study is partially retrospective because the first biopsies were taken before the study was designed, whereas the second biopsy was always performed after at least 6 months of ERT administration.
Results
After ERT, 15 out of 18 patients showed improved 6‐min walking test (6MWT; P = 0.0007) and most of them achieved respiratory stabilization. Pretreatment muscle biopsies disclosed marked histopathological variability, ranging from an almost normal pattern to a severe vacuolar myopathy. After treatment, we detected morphological improvement in 15 patients and worsening in three patients.
Post‐ERT GAA enzymatic activity was mildly increased compared with pretreatment levels in all patients. Protein levels of the mature enzyme increased in 14 of the 18 patients (mean increase = +35%; P < 0.05). Additional studies demonstrated an improved autophagic flux after ERT in some patients.
Conclusions
ERT positively modified skeletal muscle pathology as well as motor and respiratory outcomes in the majority of LOPD patients.
Mutations in the LMNA gene, encoding human lamin A/C, have been associated with an increasing number of disorders often involving skeletal and cardiac muscle, but no clear genotype/phenotype ...correlation could be established to date.
We analyzed the LMNA gene in a large cohort of patients mainly affected by neuromuscular or cardiac disease and clustered mutated patients in two groups to unravel possible correlations.
We identified 28 variants, 9 of which reported for the first time. The two groups of patients were characterized by clinical and genetic differences: 1) patients with childhood onset displayed skeletal muscle involvement with predominant scapuloperoneal and facial weakness associated with missense mutations; 2) patients with adult onset mainly showed cardiac disorders or myopathy with limb girdle distribution, often associated with frameshift mutations presumably leading to a truncated protein.
Our findings, supported by meta-analysis of previous literature, suggest the presence of two different pathogenetic mechanisms: late onset phenotypes may arise through loss of function secondary to haploinsufficiency, while dominant negative or toxic gain of function mechanisms may explain the severity of early phenotypes. This model of patient stratification may help patient management and facilitate future studies aimed at deciphering lamin A/C pathogenesis.
The coexistence of neurogenic and myogenic features in scapuloperoneal syndrome is rarely ascribed to a single gene. Defects in the nuclear envelope protein lamin A/C, encoded by the LMNA gene, have ...been shown to be associated with a variety of disorders affecting mainly the muscular and adipose tissues and, more recently, with autosomal recessive Charcot–Marie–Tooth type 2 neuropathy. This report is about a patient presenting features of myopathy and neuropathy due to a dominant LMNA mutation, suggesting that the peripheral nerve might be affected in primary LMNA myopathy. Our observations further support the marked intrafamilial and interfamilial phenotypic heterogeneity associated with lamin A/C defects.
Non-traumatic acute bilateral compartment syndrome is a rare condition that may lead to limb ischemia. We describe a case of this syndrome occurring after a five-kilometer walk in a young woman ...receiving chronic treatment with lurasidone, leading to a bilateral foot-drop and rhabdomyolysis of the anterolateral compartment of both legs. Due to her late presentation in the emergency department, we opted for a conservative approach, closely monitoring her renal function. We noticed a subsequent clinical and biochemical improvement over the following days, with the patient returning to her daily routine in a matter of weeks, despite a persisting bilateral foot drop. Since atypical antipsychotics are known to be associated with rhabdomyolysis, while possibly exerting a toxic effect on mitochondria, we hypothesize that a mild aerobic physical exertion might have triggered the event, in the context of an iatrogenic muscle susceptibility to oxidative distress.
The acronym IBMPFD denotes a syndrome including inclusion body myopathy, Paget’s disease of the bone (PDB) and frontotemporal dementia (FTD) as cardinal features, which is caused by missense ...mutations in the VCP gene. We studied the clinical characteristics and the histopathological features in two siblings and their mother who presented with adult‐onset myopathy and presenile, rapidly progressive FTD. One sibling also showed PDB. Light and electron microscopy performed on muscle biopsies demonstrated degenerative changes with inclusion bodies and abnormal aggregates. Mutation analysis of the VCP gene on affected siblings revealed a heterozygous missense mutation (R155H) in a hot spot. This is the first Italian family with multiple individuals diagnosed as having IBMPFD and carrying the recurrent R155H mutation. The implications for genetic counselling were also discussed, with regard to the procedures that may be offered to families suffering from a multisystem disorder with high risk of cognitive decline.
Recent evidence in animal models suggests that components of the extracellular matrix (ECM) play a primary role in peripheral nerve degeneration and regeneration.
We investigated the expression of ...several ECM molecules in human sural nerves by immunohistochemistry, Western blot, and reverse transcriptase PCR analysis. To unravel the possible role of these molecules in nerve regeneration, we compared results obtained from nerves with abundant signs of regeneration with those with complete absence of axonal regeneration. The role of some ECM components on neurite extension was further tested in dorsal root ganglion cultures.
We observed that the ECM composition significantly differs in regenerating compared with nonregenerating nerves, independently from their etiologic background. Fibronectin was abundantly expressed in regenerating nerves, whereas vitronectin and fibrin(ogen) prevailed in nonregenerating nerves. Whereas fibronectin is secreted by endoneurial cells, in vivo and vitro studies showed that the source of vitronectin and fibrin(ogen) is the bloodstream.
These data indicate that nerve regeneration is impaired in the presence of breaches in the blood-nerve barrier or impaired extracellular matrix (ECM) degradation that leads to accumulation of plasma vitronectin and fibrin(ogen). The transformation into mature, fibronectin-enriched ECM is necessary for efficient nerve regeneration in humans.
Spinal muscular atrophy (SMA) is an autosomal recessive genetic motor neuron disorder caused by a defect in the survival motor neuron 1 (SMN1) gene resulting from deletions or other mutations. The ...number of copies of SMN2, a gene paralogous to SMN1, modifies clinical course. The homozygous deletion of exon 7 is the most recurrent molecular defect but heterozygous deletions in compound with single nucleotide intragenic mutations have also been reported. We describe the clinical and molecular features of a child born to not consanguineous parents who developed a severe muscle hypotonia at 10 days of age. Clinical diagnosis was compatible with SMA type I (Werdnig–Hoffmann) phenotype. SMA locus genotype by quantitative PCR analysis revealed one copy of both SMN1 and SMN2 genes. Sequence analysis in the proband disclosed the heterozygous novel c.888+1G>C substitution affecting the donor splice site between exon 7 and intron 7. The deletion and the point mutation are independently inherited from the parents. Standard and quantitative RT-PCR experiments on proband’s cDNA disclosed a severe reduction of the full-length/delta7 ratio of SMN isoforms as well as the presence of a transcript originating from SMN1 but lacking exon 7. Approximately 3–5% of patients with SMA retain at least one copy of the SMN1 gene carrying pathogenic insertions, deletions, or point mutations on the other allele. The number of intragenic mutations affecting splicing is even narrower. Our findings demonstrate that the novel c.888+1G>C mutation is highly deleterious, resulting in the almost total exclusion of exon 7. Sequence analysis is helpful to identify these defects whose effects might be highly detrimental on SMN stability and function.
How membrane biosynthesis and homeostasis is achieved in myelinating glia is mostly unknown. We previously reported that loss of myotubularin-related protein 2 (MTMR2) provokes autosomal recessive ...demyelinating Charcot-Marie-Tooth type 4B1 neuropathy, characterized by excessive redundant myelin, also known as myelin outfoldings. We generated a Mtmr2-null mouse that models the human neuropathy. We also found that, in Schwann cells, Mtmr2 interacts with Discs large 1 (Dlg1), a scaffold involved in polarized trafficking and membrane addition, whose localization in Mtmr2-null nerves is altered. We here report that, in Schwann cells, Dlg1 also interacts with kinesin 13B (kif13B) and Sec8, which are involved in vesicle transport and membrane tethering in polarized cells, respectively. Taking advantage of the Mtmr2-null mouse as a model of impaired membrane formation, we provide here the first evidence for a machinery that titrates membrane formation during myelination. We established Schwann cell/DRG neuron cocultures from Mtmr2-null mice, in which myelin outfoldings were reproduced and almost completely rescued by Mtmr2 replacement. By exploiting this in vitro model, we propose a mechanism whereby kif13B kinesin transports Dlg1 to sites of membrane remodeling where it coordinates a homeostatic control of myelination. The interaction of Dlg1 with the Sec8 exocyst component promotes membrane addition, whereas with Mtmr2, negatively regulates membrane formation. Myelin outfoldings thus arise as a consequence of the loss of negative control on the amount of membrane, which is produced during myelination.
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