emerin and Myositis--Inclusion-Body

UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) is a key molecule in the pathogenesis of distal myopathy with rimmed vacuoles (DMRV) and hereditary inclusion body myopathy (HIBM) and almost all such patients have some mutations in GNE. However, subcellular localization of GNE and the mechanism of muscular damage have not been clarified.. A rabbit polyclonal antibody for GNE was prepared. Immunohistochemistry was performed using anti-GNE and anti-nuclear protein antibodies. Western blotting with subcellular fractionated proteins was performed to determine subcellular localization of GNE. The sizes of myonuclei were quantified in muscle biopsies from patients with DMRV and amyotrophic lateral sclerosis (ALS).. In DMRV muscles, immunohistochemistry identified GNE in sarcoplasm and specifically in myonuclei and rimmed vacuoles (RV). Nuclear proteins were also found in RVs. Immunohistochemistry showed colocalization of GNE and emerin in C2C12 cells. Western blotting revealed the presence of GNE in nuclear fractions of human embryonic kidney (HEK) 293T cells. The mean size of myonuclei of DMRV was significantly larger than that of ALS.. GNE is present in myonuclei near nuclear membrane. Our results suggest that myonuclei are involved in RV formation in DMRV, and that mutant GNE in myonuclei seems to play some role in this process.

Topics: Asian People; Blotting, Western; Carbohydrate Epimerases; Cell Nucleus; Cells, Cultured; Distal Myopathies; Humans; Immunohistochemistry; Japan; Membrane Proteins; Muscles; Myositis, Inclusion Body; Nuclear Proteins; Phosphotransferases (Alcohol Group Acceptor); Sarcoplasmic Reticulum; Vacuoles

The rimmed vacuoles within muscle in inclusion-body myositis (IBM) are structures of uncertain origin. Two hypotheses have been proposed for their formation: that they develop as a consequence of abnormal lysosomal function or in association with the breakdown of myonuclei. We tested the latter hypothesis by studying muscle samples from 14 patients with IBM and 18 controls using immunohistochemistry for nuclear membrane proteins, examining semithin sections, and performing electron microscopy. We found that in IBM muscle vacuoles were immunoreactive for the inner nuclear membrane proteins emerin and lamin A/C. Myonuclei with fragmented or focally absent nuclear membranes were present in immunohistochemical and electron microscopy studies. The association of nuclear membrane proteins with rimmed vacuoles confirms the hypotheses that rimmed vacuoles in IBM form in association with myonuclear pathology and that IBM differs from other inflammatory myopathies in that abnormalities of myonuclei are more prominent.

Topics: Dystrophin; Gene Expression Regulation; Humans; Immunohistochemistry; Lamin Type A; Membrane Proteins; Microscopy, Electron; Myositis, Inclusion Body; Nuclear Proteins; Vacuoles

We reported three cases (two familial and one sporadic) of X-linked Emery-Dreifuss muscular dystrophy (EDMD), genetically documented. Two patients demonstrated a typical inclusion body myositis (IBM)-like morphology. The third patient had only minor changes. Patients had elbow and ankle contractures, progressive wasting of humeroperoneal muscles and cardiac failure (pacemaker implantation in all). There was a mutation within the Xq28 gene and complete absence of emerin in the nuclear membrane. Mononuclear cell infiltrations, rimmed vacuoles, amyloid deposits, as well as cytoplasmic and nuclear tubulofilamentous muscle inclusions were most unusual findings. Coexistence of IBM-like morphology and X-linked recessive EDMD might indicate that pathological features of IBM are nonspecific and may be present in other neuromuscular disorders.

Topics: Adult; Chromosomes, Human, X; DNA Mutational Analysis; Family Health; Genetic Linkage; Humans; Immunohistochemistry; Male; Membrane Proteins; Microscopy, Electron; Muscle, Skeletal; Muscular Dystrophy, Emery-Dreifuss; Mutation; Myositis, Inclusion Body; Nuclear Proteins; Thymopoietins