Neurogenic muscular atrophy simulating facioscapulohumeral muscular dystrophy with particular reference to the heterogeneity of Kugelberg-Welander disease

Morpholino treatment improves muscle function and pathology of Pitx1 transgenic mice

Paired-like homeodomain transcription factor 1 (PITX1) was proposed to be part of the disease mechanisms of facioscapulohumeral muscular dystrophy (FSHD). We generated a tet-repressible muscle-specific Pitx1 transgenic mouse model which develops phenotypes of muscular dystrophy after the PITX1 expression is induced. In this study, we attempted to block the translation of PITX1 protein using morpholinos. Three groups of the transgenic mice received intravenous injections of phosphorodiamidate morpholino oligomers (PMO) (100 mg/kg), octaguanidinium dendrimer-conjugated morpholino (vivo-morpholino) (10 mg/kg), or phosphate-buffered saline (PBS) after the PITX1 expression was induced. Immunoblotting data showed that PITX1 expression in the triceps and quadriceps was significantly reduced 70% and 63% by the vivo-morpholino treatment, respectively. Muscle pathology of the mice treated with the vivo-morpholino was improved by showing 44% fewer angular-shaped atrophic myofibers. Muscle function determined by grip strength was significantly improved by the vivo-morpholino treatment. The study showed that systemic delivery of the vivo-morpholino reduced the PITX1 expression and improved the muscle phenotypes. Aberrant expression of DUX4 from the last unit of the D4Z4 array has been proposed to be the cause of FSHD. The findings of this study suggest that the same principle may be applied to suppress the aberrantly expressed DUX4 in FSHD.

Conditional over-expression of PITX1 causes skeletal muscle dystrophy in mice

Paired-like homeodomain transcription factor 1 (PITX1) was specifically up-regulated in patients with facioscapulohumeral muscular dystrophy (FSHD) by comparing the genome-wide mRNA expression profiles of 12 neuromuscular disorders. In addition, it is the only known direct transcriptional target of the double homeobox protein 4 (DUX4) of which aberrant expression has been shown to be the cause of FSHD. To test the hypothesis that up-regulation of PITX1 contributes to the skeletal muscle atrophy seen in patients with FSHD, we generated a tet-repressible muscle-specific Pitx1 transgenic mouse model in which expression of PITX1 in skeletal muscle can be controlled by oral administration of doxycycline. After PITX1 was over-expressed in the skeletal muscle for 5 weeks, the mice exhibited significant loss of body weight and muscle mass, decreased muscle strength, and reduction of muscle fiber diameters. Among the muscles examined, the tibialis anterior, gastrocnemius, quadricep, bicep, tricep and deltoid showed significant reduction of muscle mass, while the soleus, masseter and diaphragm muscles were not affected. The most prominent pathological change was the development of atrophic muscle fibers with mild necrosis and inflammatory infiltration. The affected myofibers stained heavily with NADH-TR with the strongest staining in angular-shaped atrophic fibers. Some of the atrophic fibers were also positive for embryonic myosin heavy chain using immunohistochemistry. Immunoblotting showed that the p53 was up-regulated in the muscles over-expressing PITX1. The results suggest that the up-regulation of PITX1 followed by activation of p53-dependent pathways may play a major role in the muscle atrophy developed in the mouse model.

Complex repetitive discharges: cause or effect of neurogenic muscle hypertrophy?

We report a patient with adult-onset spinal muscular atrophy (SMA) of the scapulohumeral type with neurogenic muscle hypertrophy (NMH) in markedly weakened biceps muscles in association with continuous complex repetitive discharges (CRDs). This is an apparently unique case due to the bilaterality of the NMH associated with CRDs as well as the well-circumscribed symmetric upper extremity distribution of the hypertrophy. The possible mechanisms of NMH in association with spontaneous motor activity are discussed.

Diagnosis in neuromuscular diseases

The diagnosis of neuromuscular diseases can be challenging and successful in the majority of patients, due to advancements in electrophysiology, muscle and nerve biopsy immunohistochemistry, and cytogenetics. This article reviews diverse topics, highlighting these recent achievements, with an emphasis on how they affect the clinical and laboratory diagnosis of specific neuromuscular disorders.

DNA rearrangements in Japanese facioscapulohumeral muscular dystrophy patients: clinical correlations

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant muscular disorder in which the disease locus has been mapped to chromosome 4q35-qter. In most patients, the DNA rearrangements associated with FSHD have been found in the EcoRI fragment detected by the p13E-11 probe, and deletions of the 3.2 kb repeat units within the fragment are thought to cause the disease. To examine FSHD-associated DNA rearrangements in the Japanese population, we performed Southern blot analysis of the genomic DNA, using the p13E-11 and pFR-1 probes, in 158 Japanese individuals, including 38 FSHD patients from 19 families. We found that all but one (a possible affected recombinant) of the Japanese FSHD patients (97.4%) had specific smaller (< 28 kb) EcoRI fragments which cosegregated with the disease; this included four patients who had severe inflammatory changes in the muscle and eight patients with de novo DNA rearrangements. We found no FSHD patient who had a fragment larger than 28 kb. By contrast, only two of 35 Japanese controls (5.7%) had EcoRI fragments smaller than 28 kb. Our patients showed anticipation, i.e. decreased size of the EcoRI fragment in parallel with earlier onset of the disease (r = 0.531, P = 0.003, with younger age at onset in children (17.8 +/- 7.0) than their affected parents (31.5 +/- 14.8) (P = 0.019). However, since each family had a specific small EcoRI fragment associated with the disease, the differing clinical severity within a family cannot be explained by the size of the fragment alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Facioscapulohumeral muscular dystrophy: muscle fiber type analysis with particular reference to small angular fibers

Muscle biopsies from 14 patients with facioscapulohumeral muscular dystrophy (FSHD) aged from 5 to 45 years were studied histochemically with fiber type analysis, focusing on small angular fibers (SAF) to clarify their significance. There were no duration-related or age-dependent histopathological differences between child and adult patients. Variations in fiber size and SAF were observed in all, myonecrosis with occasional phagocytosis in 10 and regenerating fibers in 12 biopsies. Cellular responses including inflammatory cell infiltration (7 biopsies) and connective tissue proliferation (8 biopsies), and fiber architectural changes (9 biopsies) were additional common findings. Although SAF are also commonly seen in patients with Kugelberg-Welander disease and amyotrophic lateral sclerosis, in FSHD they were mostly type 2C fibers which frequently exhibit alkaline phosphatase-positive activity. Therefore SAF in FSHD are mostly the products of a regeneration rather than denervation process.

Serum pyruvate-kinase (PK) and creatine-phosphokinase (CPK) in progressive muscular dystrophies

PK and CPK have been determined in the serum from 208 individuals including 70 normal controls (61 adults and 9 children) and 138 patients with a variety of neuromuscular disorders. In adult controls the mean activity (+/- SE) for PK is 1.2 +/- 0.05 mumol/ml/h. In normal children PK activity was about twice as high as in normal adults and decreases with increasing age. In 26 patients with Duchenne dystrophy the range of serum PK was 4.0-150.4 and in 17 individuals with the Becker type, 3.0 to 148.7. All had elevated PK and CPK levels. Eighteen of 20 patients with the facio-scapulo-humeral (FSH) from of muscular dystrophy had increased PK while only 9 had elevated CPK. Regression analyses have shown an inverse correlation between PK levels and age (or degree of disability in DMD). Kinetic and electrophoretic studies indicate that the PK isozyme found in the serum from affected patients and from heterozygotes for the DMD gene is mainly the M1 type PK, which is the only PK isozyme found in skeletal muscle and brain and the major component from myocardium.

Chronic spinal muscular atrophy of facioscapulohumeral type

Chronic spinal muscular atrophy of FSH type affecting a mother and her son and daughter is reported. The relevant literature is reviewed and the relation between this conditon and Kugelberg-Welander (K-W) disease is discussed. Chronic spinal muscular atrophy of FSH type is considered to be a different entity from the eponymous K-W disease. Each type of muscular dystrophy, e.g. limb-girdle, FSH, distal, ocular, or oculopharyngeal type, has its counterpart of nuclear origin. A classification of the chronic spinal muscular atrophies is suggested following the classification of muscular dystrophy.

The nosology of the spinal muscular atrophies

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