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Hoxd genes and fiber type-specific markers specify adult mouse muscle type in a diet-independent way

ABSTRACT: Introduction: The mouse skeletal muscle is composed of four distinct fiber types that differ in contractile function, number of mitochondria and metabolism. Every muscle group has a specific composition and distribution of the four fiber types. Until now, three genes (CnA, PGC1α and PPARδ) are identified that are involved in the generation of more oxidative muscle types. In the present study we searched for novel genes that are involved in specifying different muscle types. Methods: Gastrocnemius and quadriceps muscles were dissected from 20-week old C57BL/6J mice. Gene expression profiles were compared at the level of the whole-transcriptome. The diet-sensitivity of genes differentially expressed between muscle types was explored by comparing mice fed a low fat diet with mice fed a high fat diet. Results: We identified 162 differentially expressed genes in the gastrocnemius as compared with the quadriceps. Genes with the strongest regulations were markers for oxidative fiber types, Hoxd8, Hoxd9 and Hoxd10 and others involved in embryogenesis. Additionally, diet did not influence the expression levels of genes specifying muscle types. Finally, when extrapolating our data to the soleus we could not find a corresponding gene expression pattern between Hoxd8, Hoxd9 and any of the fiber-type specific markers. However, based on these gene expression patterns we could distinguish the gastrocnemius, quadriceps and soleus from each other. Conclusion: Hoxd genes and genes that are markers for the different fiber types specify muscle type in a diet-independent way

ORGANISM(S): Mus musculus

PROVIDER: GSE18127 | GEO | 2010/09/03

SECONDARY ACCESSION(S): PRJNA119457

REPOSITORIES: GEO

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Project description:Introduction: The mouse skeletal muscle is composed of four distinct fiber types that differ in contractile function, number of mitochondria and metabolism. Every muscle group has a specific composition and distribution of the four fiber types. Until now, three genes (CnA, PGC1α and PPARδ) are identified that are involved in the generation of more oxidative muscle types. In the present study we searched for novel genes that are involved in specifying different muscle types. Methods: Gastrocnemius and quadriceps muscles were dissected from 20-week old C57BL/6J mice. Gene expression profiles were compared at the level of the whole-transcriptome. The diet-sensitivity of genes differentially expressed between muscle types was explored by comparing mice fed a low fat diet with mice fed a high fat diet. Results: We identified 162 differentially expressed genes in the gastrocnemius as compared with the quadriceps. Genes with the strongest regulations were markers for oxidative fiber types, Hoxd8, Hoxd9 and Hoxd10 and others involved in embryogenesis. Additionally, diet did not influence the expression levels of genes specifying muscle types. Finally, when extrapolating our data to the soleus we could not find a corresponding gene expression pattern between Hoxd8, Hoxd9 and any of the fiber-type specific markers. However, based on these gene expression patterns we could distinguish the gastrocnemius, quadriceps and soleus from each other. Conclusion: Hoxd genes and genes that are markers for the different fiber types specify muscle type in a diet-independent way The aim of the present study was to find novel genes that may play a role in specifying muscle types. Therefore we compared gene expression profiles of the gastrocnemius with the quadriceps at the level of the whole-transcriptome. Functional implications were assessed by the analyses of predefined gene sets based on Gene Ontology, biochemical, metabolic and signaling pathways. muscle-type comparison

Project description:Background: skeletal muscle is a complex, versatile tissue composed of a variety of functionally diverse fiber types. Although the biochemical, structural and functional properties of myofibers have been the subject of intense investigation for the last decades, understanding molecular processes regulating fiber type diversity is still complicated by the heterogeneity of cell types present in the whole muscle organ. Methodology/Principal Findings: we have produced a first catalogue of genes expressed in mouse slow-oxidative (type 1) and fast-glycolytic (type 2B) fibers through transcriptome analysis at the single fiber level (microgenomics). Individual fibers were obtained from murine soleus and EDL muscles and initially classified by myosin heavy chain isoform content. Gene expression profiling on high density DNA oligonucleotide microarrays showed that both qualitative and quantitative improvements were achieved, compared to results with standard muscle homogenate. First, myofiber profiles were virtually free from non-muscle transcriptional activity. Second, thousands of muscle-specific genes were identified, leading to a better definition of gene signatures in the two fiber types as well as the detection of metabolic and signaling pathways that are differentially activated in specific fiber types. Several regulatory proteins showed preferential expression in slow myofibers. Discriminant analysis revealed novel genes that could be useful for fiber type functional classification. Conclusions/Significance: as gene expression analyses at the single fiber level significantly increased the resolution power, this innovative approach would allow a better understanding of the adaptive transcriptomic transitions occurring in myofibers under physiological and pathological conditions. EDL and soleus muscles were incubated with type I collagenase to dissociate intact myofibres that were separated under stereo microscope from the bulk of hyper contracted fibres. Isolated myofibres were divided in two parts: one was immersed in Laemmli buffer for fibre typing; the other was placed in RNA extraction buffer for RNA amplification. We analyzed the transcription profiles of 10 biological replicas of type 2B single muscle fibres from EDL and 10 biological replicas of type 1 single muscle fibres from soleus. Microarray competitive hybridizations were carried out against an artificial control with a balanced composition of type 1 and type 2B fibres (20 hybridizations). Each oligonucleotide is spotted in two replicates on the glass slide, so for every data two intra-slide replicas are present. The control was created as follows: three couples of soleus and EDL muscles were removed from 3 different mice and treated with collagenase. Total RNA was extracted separately from EDL and soleus muscles. By mixing about 1/3 RNA from EDL and 2/3 RNA from soleus muscles the control had approximately the same contributions of type 1 and type 2B fibres. Purified RNA samples from single fibres and from control were amplified twice using the Amino Allyl MessageAmpM-bM-^DM-" II aRNA Amplification Kit (Ambion).

Project description:Epidemiological studies reveal a strong link between low aerobic capacity and metabolic and cardiovascular diseases. Two-way artificial selection of rats based on low and high intrinsic exercise capacity has produced two strains that also differ in risk for metabolic syndrome (Koch LG, Britton SL. Artificial selection for intrinsic aerobic endurance running capacity in rats. Physiol Genomics 5:45-52, 2001). Here we investigated skeletal muscle characteristics and genotype-phenotype relationships behind high and low inherited aerobic exercise capacity and the link between oxygen metabolism and metabolic disease risk factors in rats derived from generation 18. This population (n=24) of high capacity runners (HCR) and low capacity runners (LCR) differed by 615% in maximal treadmill running capacity. LCR were significantly significantly heavier and had increased blood glucose, serum insulin and triglyceride concentration. HCR had higher resting metabolic rate than LCR. Capillaries/mm2 and capillary-to-fiber ratio were significantly greater in HCR rats in soleus and gastrocnemius and capillary-to-fiber ratio in extensor digitorum longus (EDL) muscle. Subsarcolemmal mitochondrial area was 96% (p<0.01) and intermyofibrillar area was 32% (p<0.05) larger in HCR soleus. Microarray results showed that 126 genes were significantly up-regulated and 113 genes were down-regulated in HCR (p<0.05). Functional clustering and unbiased correlation analysis of muscle microarray data revealed that genes up-regulated in HCR were related to mitochondria, carboxylic acid and lipid metabolism, and oxidoreductase activity. In conclusion, our data show that aerobic capacity is strongly linked to the architecture of energy transfer and corroborate the importance of oxygen metabolism as the determinant of metabolic health and complex metabolic diseases such as metabolic syndrome and type 2 diabetes. Total RNA obtained from gastrocnemius muscle was compared between rat strains of low and high inherited aerobic exercise capacity.

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Hoxd genes and fiber type-specific markers specify adult mouse muscle type in a diet-independent way

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