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The origin of tubular aggregates in human myopathies
Author(s) -
Chevessier Frédéric,
BauchéGodard Stéphanie,
Leroy JeanPaul,
Koenig Jeanine,
PaturneauJouas Marion,
Eymard Bruno,
Hantaï Daniel,
VerdièreSahuqué Martine
Publication year - 2005
Publication title -
the journal of pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.964
H-Index - 184
eISSN - 1096-9896
pISSN - 0022-3417
DOI - 10.1002/path.1832
Subject(s) - endoplasmic reticulum , calsequestrin , chemistry , biophysics , protein aggregation , fibril , microbiology and biotechnology , sarcoplasm , mitochondrion , biology , biochemistry , ryanodine receptor
Abstract Tubular aggregates are morphological abnormalities characterized by the accumulation of densely packed tubules in skeletal muscle fibres. To improve knowledge of tubular aggregates, the formation and role of which are still unclear, the present study reports the electron microscopic analysis and protein characterization of tubular aggregates in six patients with ‘tubular aggregate myopathy’. Three of the six patients also presented with myasthenic features. A large panel of immunochemical markers located in the sarcoplasmic reticulum, T‐tubules, mitochondria, and nucleus was used. Despite differences in clinical phenotype, the composition of tubular aggregates, which contained proteins normally segregated differently along the sarcoplasmic reticulum architecture, was similar in all patients. All of these proteins, calsequestrin, RyR, triadin, SERCAs, and sarcalumenin, are involved in calcium uptake, storage, and release. The dihydropyridine receptor, DHPR, specifically located in the T‐tubule, was also present in tubular aggregates in all patients. COX‐2 and COX‐7 mitochondrial proteins were not found in tubular aggregates, despite being observed close to them in the muscle fibre. The nuclear membrane protein emerin was found in only one case. Electron microscopy revealed vesicular budding from nuclei, and the presence of SAR‐1 GTPase protein in tubular aggregates shown by immunochemistry, in all patients, suggests that tubular aggregates could arise from endoplasmic reticulum exit sites. Taken together, these results cast new light on the composition and significance of tubular aggregates. Copyright © 2005 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.