Unknown,Transcriptomics,Genomics,Proteomics

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Genomic profiling of a RYR1-deficient skeletal muscle

ABSTRACT: In differentiated skeletal muscle, intracellular Ca2+ concentrations rise dramatically upon membrane depolarization, constituting the link between excitation and contraction (EC). Transient rises in [Ca2+]i mainly emerge from Ca2+ released by the type 1 ryanodine receptor (RYR1) and, in non-adult muscle, by the inositol 1,4,5-triphosphate receptor (IP3R) of the sarcoplasmic reticulum (SR), the dominant Ca2+ store in skeletal muscle. While the IP3R-mediated, slow Ca2+ transients, have been implicated in cell signaling and development, RYR1’s non-contractile role(s) remain obscure. We used a homozygous mouse RyR1 knockout model (dyspedic) to investigate the effects of the absence of a functional RYR1 and, consequently, the lack of RyR1-mediated Ca2+ signaling during embryogenesis. While heterozygous mice of the model are undistinguishable from WT littermates, homozygous dyspedic mice die at birth from asphyxia, since their skeletal muscle does not support EC coupling. Furthermore, they display abnormal spine curvature, subcutaneous hematomas, small limbs, and enlarged neck. Skeletal muscles from front and hind limbs of dyspedic embryos (day E18.5) were subjected to microarray analyses, revealing 318 genes, significantly regulated by at least 50 % compared to control heterozygous littermates.

INSTRUMENT(S): Maxwell 16 Instrument (Cat. #AS2000, Promega, Madison, WI), Affymetrix Gene-Chip Scanner-3000-7G, Genechip Hybridization Oven-645 (Affymetrix); Geneechip Fluidics Station-450 (Affymetrix)

ORGANISM(S): Mus musculus

SUBMITTER: Dilyana Filipova

PROVIDER: E-MTAB-3608 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Background: Niemann-Pick disease type A (NPDA), a disease caused by mutations in acid sphingomyelinase (ASM), involves severe neurodegeneration and early death. Intracellular lipid accumulation and plasma membrane alterations are implicated in the pathology. ASM is also linked to the mechanism of plasma membrane repair, so we investigated the impact of ASM deficiency in skeletal muscle, a tissue that undergoes frequent cycles of injury and repair in vivo. Methods: Utilizing the NPDA/B mouse model ASM−/− and wild type (WT) littermates, we performed excitation- contraction coupling/Ca2+ mobilization and sarcolemma injury/repair assays with isolated flexor digitorum brevis fibers, proteomic analyses with quadriceps femoris, flexor digitorum brevis, and tibialis posterior muscle and in vivo tests of the contractile force (maximal isometric torque) of the quadriceps femoris muscle before and after eccentric contraction-induced muscle injury. Results: ASM−/− flexor digitorum brevis fibers showed impaired excitation-contraction coupling compared to WT, a defect expressed as reduced tetanic [Ca2+]i in response to electrical stimulation and early failure in sustaining [Ca2+]i during repeated tetanic contractions. When injured mechanically by needle passage, ASM−/− flexor digitorum brevis fibers showed susceptibility to injury similar to WT, but a reduced ability to reseal the sarcolemma. Proteomic analyses revealed changes in a small group of skeletal muscle proteins as a consequence of ASM deficiency, with downregulation of calsequestrin occurring in the three different muscles analyzed. In vivo, the loss in maximal isometric torque of WT quadriceps femoris was similar immediately after and 2 min after injury. The loss in ASM−/− mice immediately after injury was similar to WT, but was markedly larger at 2 min after injury. Conclusions: Skeletal muscle fibers from ASM−/− mice have an impairment in intracellular Ca2+ handling that results in reduced Ca2+ mobilization and a more rapid decline in peak Ca2+ transients during repeated contraction-relaxation cycles. Isolated fibers show reduced ability to repair damage to the sarcolemma, and this is associated with an exaggerated deficit in force during recovery from an in vivo eccentric contraction- induced muscle injury. Our findings uncover the possibility that skeletal muscle functional defects may play a role in the pathology of NPDA/B disease.

Project description:Background Loss of skeletal muscle mass in advanced cancer is recognized as an independent predictor of mortality. Mechanisms involved in this wasting process and parameters for early diagnosis are still lacking. As skeletal muscle is considered as a secretory organ, the aim of this present experimental work was to characterize the changes in muscle proteome and secretome associated with cancer-induced cachexia to better understand cellular mechanisms involved in this wasting process and to identify secreted proteins which might reflect the ongoing muscle atrophy process. Methods We investigated first the changes in the muscle proteome associated with cancer-induced cachexia by using differential label-free proteomic analysis on muscle of the C26 mouse model. The differentially abundant proteins were submitted to sequential bioinformatic secretomic analysis in order to identify potentially secreted proteins. Selected reaction monitoring and Western blotting were used to verify the presence of candidate proteins at the circulating level. Their muscle source was demonstrated by assessing their gene expression in skeletal muscle and in cultured myotubes. Finally, we also investigated their regulation in muscle cells. Alterations in several molecular pathways potentially involved in muscle atrophy were highlighted using Gene ontology enrichment analyses. Results Our results revealed a dramatic increased production (2-to 25-fold) by the muscle of several acute phase reactants (APR: Haptoglobin, Serpina3n, Complement C3, Serum amyloid A1) which are also released in the circulation during C26 cancer cachexia. Their production was confirmed in other preclinical models of cancer cachexia as well as in cancer patients. The muscular origin of these APR was demonstrated by their increased expression in skeletal muscle and myotubes. Glucocorticoids and pro-inflammatory cytokines contribute directly to their increased expression in muscle cells in vitro, while the role of IL-6 in the muscular induction of these APR was demonstrated in vivo. Conclusions Cancer is associated with marked changes in muscle secretome during muscle wasting. Our study demonstrates a marked increased production of APR by skeletal muscle in pre-clinical models of cancer cachexia and in cancer patients. Further studies are required to unravel the potential role of these proteins in muscle atrophy and their interest as biomarkers of cancer cachexia.

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Genomic profiling of a RYR1-deficient skeletal muscle

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