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KMID : 1035220100020010007
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Korean Journal of Neuromuscular Disorders
2010 Volume.2 No. 1 p.7 ~ p.13
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The Findings of Nuclear Changes in Skeletal Muscle Laminopathy (AD-EDMD/LGMD1B)
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Park Yeong-Eun
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Abstract
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Laminopathy is a term designed for the diseases caused by mutations in a gene encoding nuclear envelope proteins, lamin A/C (LMNA). Skeletal muscle laminopathy includes autosomal dominant/ recessive Emery-Dreifuss muscular dystrophies (AD/AR-EDMD) and limb-girdle muscular dystrophy type 1B (LGMD1B), which are clinically characterized by progressive muscular weakness, varying degree of joint contractures and cardiac involvement. Since lamin A/C is believed to maintain nuclear integrity by polymerizing into nuclear lamina, the mutations in LMNA might affect nuclear shape and subsequently alter normal gene expression, especially in skeletal muscles. Our observation using electron microscope to analyze skeletal muscle nuclei of laminopathy supports this notion. It has been shown that nuclei are quite altered in their shapes (e.g. nuclear chain formation, sawtooth deformity and serpentine shape) and chromatin is disorganized in majority of nuclei. Chromatin disorganization occurred also in nuclei of satellite cells, which are precursors of skeletal muscle cells, suggesting that muscle regeneration is disturbed in laminopathy. Furthermore, vacuolar formations are frequently detected nearby nuclei, the consistent finding of which implies that nuclear vacuoles may have a role in the pathogenesis. Despite of significant changes in nuclei, myofibrils are relatively well arranged. Thus, it is concluded that nuclear abnormalities and the disturbed muscle regeneration mainly contribute to the pathogenesis of skeletal muscle laminopathy.
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KEYWORD
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Skeletal muscle laminopathy, Lamin A/C, Nucleus, Satellite cell, Vacuole
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