Characteristic expression of cell adhesion molecules in adhalin deficiency

Overexpression of Neural Cell Adhesion Molecule in Regenerative Muscle Fibers in 3-Hydroxy-3-Methylglutaryl Coenzyme: A Reductase Inhibitor-induced Rhabdomyolysis

Skeletal muscle degeneration is a side effect of cholesterol-lowering hydroxymethylglutaryl coenzyme A reductase inhibitors. The expression of the cell-cell adhesion proteins, neural cell adhesion molecule and neural-cadherin was studied in a case of rhabdomyolysis induced by the hydroxymethylglutaryl coenzyme A reductase inhibitor cerivastatin. Neural cell adhesion molecule and N-cadherin participate in the interactions of muscle cells during skeletal myogenesis. In the adult muscle, neural cell adhesion molecule is restricted to neuromuscular sites but is re-expressed in denervated muscle and in rhabdomyolysis. Our results show expression of neural cell adhesion molecule in regenerative skeletal muscle fibers but not in degenerated or unaffected fibers in cerivastatin-induced rhabdomyolysis. In contrast, N-cadherin was not expressed. The presence of apoptotic cells was studied by a fluorescence-based Tdt-mediated dUTP nick-end labeling in the same sections. Apoptosis was detected in degenerative fibers and inflammatory cells but not in regenerative fibers. We hypothesize that the expression of neural cell adhesion molecule in regenerative fibers may have a protective role against apoptosis during rhabdomyolysis. Cerivastatin-induced rhabdomyolysis appears to have common features with rhabdomyolysis of other causes. The immunohistochemical study of neural cell adhesion molecule can serve as an additional tool in the evaluation of muscle regeneration in rhabdomyolysis.

Diagnosis of dystrophinopathy by skin biopsy

We studied the expression of dystrophin in skin biopsy samples from 19 patients with neuromuscular diseases. Immunohistochemical procedures for dystrophin analyses were performed using monoclonal antibodies for three different domains. Arrector pili muscles, which are smooth muscles in the skin, expressed dystrophin in the patients with limb-girdle muscular dystrophy (5), facioscapulohumeral muscular dystrophy (1), and spinal muscular atrophy (3), and in normal controls (2). The C-terminus of dystrophin was slightly expressed in the patients with Duchenne muscular dystrophy, whereas the rod domain and N-terminus were absent. In one patient with Becker muscular dystrophy, the expression of dystrophin was reduced. The mosaic of dystrophin positive and negative smooth muscle fibers was observed in a manifesting carrier of Duchenne muscular dystrophy. Our results suggest that skin biopsy is very useful for the diagnosis of Duchenne/Becker muscular dystrophy and manifesting carrier of Duchenne muscular dystrophy, and can be performed even at an advanced stage of the disease.

Expression of thrombomodulin, caveolin-3, and desmin on muscle fibers in neuromuscular diseases

The expression of thrombomodulin (TM) and caveolin-3 on biopsied muscle fibers from 17 patients with various neuromuscular diseases was studied immunocytochemically. We also compared the expression of TM and caveolin-3 with that of desmin, which is a marker for muscle fiber regeneration. Most TM-positive muscle fibers strongly expressed caveolin-3 and desmin. Our results suggest that TM is expressed and caveolin-3 is upregulated during the process of muscle fiber regeneration.

New missense mutation in the alpha-sarcoglycan gene in a Japanese patient with severe childhood autosomal recessive muscular dystrophy with incomplete alpha-sarcoglycan deficiency

A new homozygous alpha-sarcoglycan (adhalin) gene mutation was found in a Japanese patient with severe childhood autosomal recessive muscular dystrophy (SCARMD). Muscle biopsy specimens from the patient showed marked reduction but not complete deficiency of alpha-sarcoglycan. The sequence of part of exon 3 of the alpha-sarcoglycan gene exhibited a cytosine to thymidine substitution at nucleotide position 220. Since the same mutation was not found in 100 normal control samples, this new alpha-sarcoglycan gene mutation is not a polymorphism but is presumed to be responsible for the marked reduction of alpha-sarcoglycan in skeletal muscle. Most patients with homozygous alpha-sarcoglycan gene mutation were reported to show complete alpha-sarcoglycan deficiency. Present case showed the homozygous missense mutation of alpha-sarcoglycan and associated with incomplete alpha-sarcoglycan deficiency and severe clinical phenotype.