Project description:Skeletal muscle fiber type distribution has implications for human health, muscle function and performance. This knowledge has been gathered using labor intensive and costly methodology that limited these studies. Here we present a method based on muscle tissue RNA sequencing data (totRNAseq) to estimate the distribution of skeletal muscle fiber types from frozen human samples, allowing for larger number of individuals to be tested. By using single-nuclei snRNA sequencing (snRNAseq) data as a reference, cluster expression signatures were produced by averaging gene expression of cluster gene markers and then applying these to totRNAseq data and inferring muscle fiber nuclei type via linear matrix decomposition. This estimate was then compared with fiber type distribution measured by ATPas staining or myosin heavy chain protein isoform distribution of 62 muscle samples in two independent cohorts (n = 39 and 22). The correlation between the sequencing-based method and the other two were rATPas = 0.65 [0.46 – 0.84], [95% CI] and rmyosin = 0.80 [0.71 – 0.89], with p = 7.96 x 10-6 and 8.06 x 10-6 respectively. The deconvolution inference of fiber type composition was accurate even for very low totRNAseq sequencing depths, i.e., down to an average of ~5.000 paired end reads. This new method consequently allows for measurement of fiber type distribution of a larger number of samples using totRNAseq in a cost and labor efficient way. For the first time it is now feasible to study the association between fiber type distribution and health outcomes in large well-powered studies.
Project description:Skeletal muscles are composed of a heterogeneous collection of fiber types with different physiological adaption in response to a stimulus and disease-related conditions. Each fiber has a specific molecular expression of myosin heavy chain molecules (MyHC). So far MyHCs are currently the best marker proteins for characterization of individual fiber types and several proteome profiling studies have helped to dissect the molecular signature of whole muscles and individual fibers. Herein, we describe a mass spectrometric workflow to measure skeletal muscle fiber type-specific proteomes. To bypass the limited quantities of protein in single fibers, we developed a Proteomics high-throughput Fiber Typing (ProFiT) approach enabling profiling of MyHC in single fibers. Aliquots of protein extracts from separated muscle fibers were subjected to capillary LC-MS gradients to profile MyHC isoforms in a 96-well format. Muscle fibers with the same MyHC protein expression were pooled and subjected to proteomic, pulsed-SILAC and phosphoproteomic analysis. Our fiber type-specific quantitative proteome analysis confirmed the distribution of fiber types in the soleus muscle, substantiates metabolic adaptions in oxidative and glycolytic fibers, and highlighted significant differences between the proteomes of type IIb fibers from different muscle groups, including a differential expression of desmin and actinin-3. A detailed map of the Lys-6 incorporation rates in muscle fibers showed an increased turnover of slow fibers compared to fast fibers. In addition, labeling of mitochondrial respiratory chain complexes revealed a broad range of Lys-6 incorporation rates, depending on the localization of the subunits within distinct complexes.
Project description:BackgroundSkeletal muscle fiber type distribution has implications for human health, muscle function, and performance. This knowledge has been gathered using labor-intensive and costly methodology that limited these studies. Here, we present a method based on muscle tissue RNA sequencing data (totRNAseq) to estimate the distribution of skeletal muscle fiber types from frozen human samples, allowing for a larger number of individuals to be tested.MethodsBy using single-nuclei RNA sequencing (snRNAseq) data as a reference, cluster expression signatures were produced by averaging gene expression of cluster gene markers and then applying these to totRNAseq data and inferring muscle fiber nuclei type via linear matrix decomposition. This estimate was then compared with fiber type distribution measured by ATPase staining or myosin heavy chain protein isoform distribution of 62 muscle samples in two independent cohorts (n = 39 and 22).ResultsThe correlation between the sequencing-based method and the other two were rATPas = 0.44 [0.13-0.67], [95% CI], and rmyosin = 0.83 [0.61-0.93], with p = 5.70 × 10-3 and 2.00 × 10-6, respectively. The deconvolution inference of fiber type composition was accurate even for very low totRNAseq sequencing depths, i.e., down to an average of ~ 10,000 paired-end reads.ConclusionsThis new method ( https://github.com/OlaHanssonLab/PredictFiberType ) consequently allows for measurement of fiber type distribution of a larger number of samples using totRNAseq in a cost and labor-efficient way. It is now feasible to study the association between fiber type distribution and e.g. health outcomes in large well-powered studies.
Project description:Skeletal muscle is a key tissue in human aging, which affects different muscle fiber types unequally. We developed a highly sensitive single muscle fiber proteomics workflow to study human aging and show that the senescence of slow and fast muscle fibers is characterized by diverging metabolic and protein quality control adaptations. Whereas mitochondrial content declines with aging in both fiber types, glycolysis and glycogen metabolism are upregulated in slow but downregulated in fast muscle fibers. Aging mitochondria decrease expression of the redox enzyme monoamine oxidase A. Slow fibers upregulate a subset of actin and myosin chaperones, whereas an opposite change happens in fast fibers. These changes in metabolism and sarcomere quality control may be related to the ability of slow, but not fast, muscle fibers to maintain their mass during aging. We conclude that single muscle fiber analysis by proteomics can elucidate pathophysiology in a sub-type specific manner.
Project description:Skeletal muscle fiber composition and muscle energetics are not static and change in muscle disease. This study was performed to determine if a mitochondrial myopathy is associated with adjustments in skelatal fiber type composition. These effects of drug induced mitochondrial dysfunction on skeletal muscle fiber type composition were analyzed in an animal model.
Project description:BackgroundSkeletal muscles are composed of a heterogeneous collection of fiber types with different physiological adaption in response to a stimulus and disease-related conditions. Each fiber has a specific molecular expression of myosin heavy chain molecules (MyHC). So far, MyHCs are currently the best marker proteins for characterization of individual fiber types, and several proteome profiling studies have helped to dissect the molecular signature of whole muscles and individual fibers.MethodsHerein, we describe a mass spectrometric workflow to measure skeletal muscle fiber type-specific proteomes. To bypass the limited quantities of protein in single fibers, we developed a Proteomics high-throughput fiber typing (ProFiT) approach enabling profiling of MyHC in single fibers. Aliquots of protein extracts from separated muscle fibers were subjected to capillary LC-MS gradients to profile MyHC isoforms in a 96-well format. Muscle fibers with the same MyHC protein expression were pooled and subjected to proteomic, pulsed-SILAC, and phosphoproteomic analysis.ResultsOur fiber type-specific quantitative proteome analysis confirmed the distribution of fiber types in the soleus muscle, substantiates metabolic adaptions in oxidative and glycolytic fibers, and highlighted significant differences between the proteomes of type IIb fibers from different muscle groups, including a differential expression of desmin and actinin-3. A detailed map of the Lys-6 incorporation rates in muscle fibers showed an increased turnover of slow fibers compared to fast fibers. In addition, labeling of mitochondrial respiratory chain complexes revealed a broad range of Lys-6 incorporation rates, depending on the localization of the subunits within distinct complexes.ConclusionOverall, the ProFiT approach provides a versatile tool to rapidly characterize muscle fibers and obtain fiber-specific proteomes for different muscle groups.
Project description:Skeletal muscle is a complex heterogeneous tissue comprised of diverse muscle fiber and non-fiber cell types that, in addition to movement, influences other systems such as immunity, metabolism and cognition. We investigated gene expression patterns of resident human skeletal muscle cells using both single-cell RNA-seq and RNA-seq of single muscle fiber dissections from vastus lateralis. We generated transcriptome profiles of the major multinucleated human skeletal muscle fiber-types as well as 11 human skeletal muscle mononuclear cell types, including immune, endothelial, pericyte and satellite cells. We delineated two fibro-adipogenic progenitor cell subtypes that may contribute to heterotopic ossification and muscular dystrophy fibrosis under pathological conditions. An important application of cell type signatures is for computational deconvolution of cell type specific gene expression changes using data from bulk transcriptome experiments. Analysis of transcriptome data from a 12 week resistance exercise training study using these human skeletal muscle cell-type signatures revealed significant changes in specific mononuclear cell-type proportions related to age, sex, acute exercise and training. This characterization of human skeletal muscle cell types will resolve cell-type specific changes in large-scale physical activity muscle transcriptome studies and can further the understanding of the diverse effects of exercise and the pathophysiology of muscle disease.
Project description:Skeletal muscle is a heterogeneous tissue consisting of blood vessels, connective tissue, and muscle fibers. The last are highly adaptive and can change their molecular composition depending on external and internal factors, such as exercise, age, and disease. Thus, examination of the skeletal muscles at the fiber type level is essential to detect potential alterations. Therefore, we established a protocol in which myosin heavy chain isoform immunolabeled muscle fibers were laser microdissected and separately investigated by mass spectrometry to develop advanced proteomic profiles of all murine skeletal muscle fiber types. Our in-depth mass spectrometric analysis revealed unique fiber type protein profiles, confirming fiber type-specific metabolic properties and revealing a more versatile function of type IIx fibers. Furthermore, we found that multiple myopathy-associated proteins were enriched in type I and IIa fibers. To further optimize the assignment of fiber types based on the protein profile, we developed a hypothesis-free machine-learning approach (available at: https://github.com/mpc-bioinformatics/FiPSPi), identified a discriminative peptide panel, and confirmed our panel using a public data set.
Project description:Spaceflight causes loss of muscle mass and strength, metabolic remodeling and insulin resistance, contributing to severe challenges for astronaut health. We used highly sensitive proteomics to detail single fiber type-specific molecular remodeling caused by muscle unloading in subjects undergoing prolonged bed rest. We then measured the muscle proteome of astronauts before and after a mission on the ISS. Our combined datasets show downregulation of complexes involved in fiber-matrix interaction, force transmission and insulin receptor stabilization on the sarcolemma. Unloading upregulated anti-oxidant responses in slow but not in fast fibers, markers of neuromuscular damage and the hypusination pathway that uniquely modifies translation initiation factor 5A. These muscle intrinsic changes in adhesion, protein turnover and redox balance may contribute to the whole-body detrimental effects caused by prolonged unloading. We conclude that single muscle fiber analysis by proteomics can support the development of advanced countermeasures targeting the mechano-metabolic molecular axis.
Project description:Skeletal muscle function is vital to movement, thermogenesis and metabolism. Muscle fibers differ in contractile ability, mitochondrial content and metabolic properties and muscle fiber transition influences muscle function. However, the molecular mechanisms regulating muscle fiber transition in muscle function are unclear. Here, in over 150 human muscle samples, we observed that markers of oxidative muscle fiber and mitochondria correlate positively with PPARGC1 and CDK4, and, negatively with CDKN2A, a locus significantly associated with type 2 diabetes. Mice expressing an overactive Cdk4 that cannot bind its inhibitor p16INK4a, a product of the CDKN2A locus, are longer, leaner, exhibit increased oxidative myofibers with superior mitochondrial energetics, display enhanced muscle glucose uptake, and are protected from obesity and diabetes. In contrast, Cdk4-deficiency, or skeletal muscle-specific deletion of Cdk4’s transcriptional target, E2F3, reduces oxidative myofiber numbers, deteriorates mitochondrial function and exercise capacity, while increasing diabetes susceptibility. E2F3 activates the PPARGC1 promoter and CDK4/E2F3/PPARGC1 levels correlate positively with exercise and fitness, and negatively with adiposity, insulin resistance and lipid accumulation in muscle. These findings provide insight into oxidative muscle fiber transition and function that is of relevance to metabolic and muscular diseases.