Changes in Muscle Cell Metabolism and Mechanotransduction Are Associated with Myopathic Phenotype in a Mouse Model of Collagen VI Deficiency

Abstract

This study identifies metabolic and protein phenotypic alterations in gastrocnemius, tibialis anterior and diaphragm muscles of Col6a1−/− mice, a model of human collagen VI myopathies. All three muscles of Col6a1−/− mice show some common changes in proteins involved in metabolism, resulting in decreased glycolysis and in changes of the TCA cycle fluxes. These changes lead to a different fate of α-ketoglutarate, with production of anabolic substrates in gastrocnemius and tibialis anterior, and with lipotoxicity in diaphragm. The metabolic changes are associated with changes of proteins involved in mechanotransduction at the myotendineous junction/costameric/sarcomeric level (TN-C, FAK, ROCK1, troponin I fast) and in energy metabolism (aldolase, enolase 3, triose phosphate isomerase, creatine kinase, adenylate kinase 1, parvalbumin, IDH1 and FASN). Together, these change may explain Ca2+ deregulation, impaired force development, increased muscle-relaxation-time and fiber damage found in the mouse model as well as in patients. The severity of these changes differs in the three muscles (gastrocnemius<tibialis anterior<diaphragm) and correlates to the mass-to-tendon (myotendineous junction) ratio and to muscle morphology.

Deep RNA profiling identified CLOCK and molecular clock genes as pathophysiological signatures in collagen VI myopathy

“…We found that the expression profiles of Col6a1 −/− and WT gastrocnemius were clustered together and therefore similar. Indeed this supports the existing knowledge about muscle involvement in the Col6a1 −/− mouse model, where gastrocnemius is very mildly affected, whereas tibialis and even more diaphragm are severely affected (De Palma et al, 2013). In contrast, diaphragm and tibialis anterior Col6a1 −/− muscles clustered together and were clearly separate from their WT counterparts, suggesting that ColVI deficiency severely and similarly affects these muscle types (Fig.…”

“…We show major transcriptional changes in the diaphragm and tibialis anterior, accordingly to the proteomic findings (De Palma et al, 2013). All muscles shared similar alterations in genes involved in the inflammatory response, cell proliferation, −/− and wild-type (Ctrl) mice revealed a significant upregulation (*P<0.05, t-test) of CLOCK protein levels in the diaphragm and tibialis anterior, whereas the MAT2a protein level was significantly altered in tibialis anterior and gastrocnemius, which showed an increase and decrease, respectively.…”

“…The CLOCK gene deregulation, we also confirmed at the protein level in Col6a1 −/− mice, suggests a previously unreported relationship between circadian rhythms, the molecular clock and myopathy. The Col6a1 −/− model shows both muscle and osteotendinous junction damage (Izu et al, 2011(Izu et al, , 2012, reflecting defective costamerogenesis and altered mechanotransduction (De Palma et al, 2013). Specific activation of both myocardinrelated transcription factors (MRTFs) and ternary complex factors (TCFs), whose targets are regulators of cytoskeleton dynamics and mechanosensing, have potential to reset the molecular clock through regulation of PER1, PER2, BMAL1 and other CLOCK genes (Esnault et al, 2014).…”

“…Moreover, in Col6a1 −/− mice, changes in metabolic proteins resulting in decreased glycolysis and affecting the tricarboxylic acid (TCA) cycle fluxes lead to a different fate of α-ketoglutarate triggering lipotoxicity. The metabolic changes are associated with changes of proteins involved in mechanotransduction at the myotendineous junction, costameric or sarcomeric level, and in energy metabolism (De Palma et al, 2013). Recently, a strong depletion of the α6(VI) chain in skeletal muscle has been reported as potential biomarker of ColVI myopathies (Tagliavini et al, 2014a).…”

Changes in muscle proteomics in the course of the Caudwell Research Expedition to Mt. Everest

“…Summarizing, after subacute exposure to hypobaric hypoxia, the muscle starts controlling HIF‐1α hydroxylation and behaves as a producer of substrates controlling de novo protein synthesis, sarcoplasmic reticulum Ca 2+ release, ROS generation as well as the activation of detrimental pathways known to drive the metabolic machinery toward accumulation of lipogenic citrate . Thus, in this phase, energy‐sparing mechanisms contribute mainly to the maintenance of energetic and redox homeostasis.…”