Gene expression profiling of diaphragm muscle in alpha2-laminin (merosin)-deficient dy/dy dystrophic mice.
ABSTRACT Deficiency of alpha2-laminin (merosin) underlies classical congenital muscular dystrophy in humans and dy/dy muscular dystrophy in mice and causes severe muscle dysfunction in both species. To gain greater insight into the biochemical and molecular events that link alpha2-laminin deficiency with muscle fiber necrosis, and the associated compensatory responses, gene expression profiles were characterized in diaphragm muscle from 8-wk-old dy/dy mice using oligonucleotide microarrays. Compared with age-matched normal muscle, dystrophic diaphragm was characterized by predominantly augmented gene expression, irrespective of the fold-change threshold. Among the 69 genes with at least plus or minus twofold significantly altered expression, 30 belonged to statistically overrepresented Gene Ontology (GO) biological process groups. These covered four specific themes: development including muscle development, cell motility with an emphasis on muscle contraction, defense/immune response, and cell adhesion. An additional 11 gene transcripts were assigned to more general overrepresented GO biological process groups (e.g., cellular process, organismal physiological process); the remaining 28 did not belong to any overrepresented groups. GO cellular constituent assignment resulted in the highest degree of overrepresentation in extracellular and muscle fiber locations, whereas GO molecular function assignment was most notable for various types of binding. RT-PCR was performed on 38 of 41 genes with at least plus or minus twofold significantly altered expression that were assigned to overrepresented GO biological process groups, with expression changes verified for 36 of 38 genes. These results indicate that several specific groups of genes have altered expression in response to genetic alpha2-laminin deficiency, with both similarities and differences compared with data reported for dystrophin-deficient muscular dystrophies.
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ABSTRACT: Congenital muscular dystrophy type 1A, a severe neuromuscular disease characterized by early-onset muscle weakness and degeneration, is caused by insufficient levels of laminin α2 (LAMA2) in the basal lamina surrounding muscle fibers and other cells. A better understanding of the molecular mechanisms leading to muscle loss is needed to develop therapeutic interventions for this disease. Here, the authors show that inflammation is an early feature of pathogenesis in Lama2-deficient mouse muscle, indicated by elevated expression of tenascin C in the endomysium around muscle fibers, infiltration of macrophages, and induction of the inflammatory cytokines tumor necrosis factor α (TNFα) and IL-1β. In addition, the expression of lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1), a specific marker for lymphatic vessel endothelial cells, is dramatically reduced early in Lama2-deficient muscle pathogenesis. LYVE-1 expression, which is inhibited by TNFα, is also decreased in muscles undergoing degeneration due to dystrophin deficiency and cardiotoxin damage. LYVE-1 expression thus provides a useful biomarker to monitor the onset of muscle pathogenesis, likely serving as an indicator of inflammatory signals present in muscles. Together, the data show that inflammatory pathways are activated in the earliest stages of Lama2-deficient disease progression and could play a role in early muscle degeneration.Journal of Histochemistry and Cytochemistry 09/2010; 59(2):167-79. · 2.26 Impact Factor
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ABSTRACT: To increase our understanding of profibrotic mechanisms in dystrophic muscle. Extracellular matrix, fibrosis-related molecules and histopathology were assessed in skeletal muscle of patients with Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD), and congenital muscular dystrophy type 1A (MDC1A).Osteopontin expression was much higher in DMD and MDC1A than in BMD and control muscle. Osteopontin was expressed in mononuclear cell infiltrates, on some muscle fibre surfaces, in regenerating fibres, and in calcified fibres. In all pathological muscles, matrix metalloproteinase (MMP)-1 was increased around groups of fibres that were also characterized by absence of collagen 1. The amounts of MMP-2, MMP-9 and tissue inhibitor of MMP -1 transcripts were also increased, whereas their proteins were variably expressed in muscle fibres (surface or cytoplasm) and at foci of necrosis and regeneration. Inflammatory cells, fibroblasts and myofibroblasts were more numerous in DMD and MDC1A than in BMD muscle. Several fibrosis-related factors are greatly altered in severely dystrophic skeletal muscle. Osteopontin was the most conspicuously upregulated, both as transcript and as protein, in muscle fibres and infiltrating cells, indicating an intimate involvement in fibrosis, and also in inflammation and muscle regeneration, although its precise roles in these processes remain to be elucidated.Histopathology 12/2011; 59(6):1215-28. · 2.86 Impact Factor
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ABSTRACT: Contractile properties of upper airway muscles influence upper airway patency, an issue of particular importance for subjects with obstructive sleep apnea. Expression of genes related to cellular energetics is, in turn, critical for the maintenance of contractile integrity over time during repetitive activation. We tested the hypothesis that sternohyoid has lower expression of genes related to lipid and carbohydrate energetic pathways than the diaphragm. Sternohyoid and diaphragm from normal adult rats were examined with gene expression arrays. Analysis focused on genes belonging to Gene Ontology (GO) groups carbohydrate metabolism and lipid metabolism. There were 433 genes with at least +/- 2-fold significant differential expression between sternohyoid and diaphragm, of which 192 had sternohyoid > diaphragm and 241 had diaphragm > sternohyoid expression. Among genes with higher sternohyoid expression, there was over-representation of the GO group carbohydrate metabolism (P = 0.0053, n = 13 genes, range of differential expression 2.1- to 6.2-fold) but not lipid metabolism (P = 0.44). Conversely, among genes with higher diaphragm expression, there was over-representation of the GO group lipid metabolism (P = 0.0000065, n = 32 genes, range of differential expression 2.0- to 37.9-fold) but not carbohydrate metabolism (P = 0.23). Nineteen genes with diaphragm > sternohyoid expression were related to fatty acid metabolism (P = 0.000000058), in particular fatty acid beta oxidation and biosynthesis in the mitochondria. Sternohyoid has much lower gene expression than diaphragm for mitochondrial enzymes that participate in fatty acid oxidation and biosynthesis. This likely contributes to the lower fatigue resistance of pharyngeal upper airway muscles compared with the diaphragm.Sleep 03/2010; 33(3):363-70. · 5.10 Impact Factor