Estudo do músculo diafragma em ratos com insuficiência cardíaca crônica: composição das miosinas e expressão dos fatores de regulação miogênica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Caracterização morfológica, bioquímica e molecular do músculo esquelético sóleo de ratos espontaneamente hipertensos com insuficiência cardíaca

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influência da alimentação inicial no crescimento muscular e na expressão da MyoD e Miogenina em larvas de pacu

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Adaptações morfofuncionais e respostas moleculares do músculo esquelético de ratos submetidos ao treinamento resistido

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Efeito da temperatura sobre a expressão de fatores miogênicos no músculo estriado esquelético do pacu (Piaractus mesopotamicus)

Pós-graduação em Biologia Geral e Aplicada - IBB

Morphology and expression of genes related to skeletal muscle growth in juveniles of pirarucu (Arapaima gigas, Arapaimatidae, Teleostei)

Skeletal muscle growth in the pirarucu (Arapaima gigas) is highly interesting to fish farmers because it provides information about how the mechanism in muscle mass increase, characteristic of the species, is regulated. Pirarucu has specific muscle growth that highlights the species's significance and commercial value. Current research evaluates the morphology and the growth-related gene expression in the red and white skeletal muscles of the pirarucu. Muscle samples were collected from the lateral anterior region and frozen in liquid nitrogen. Histological sections were performed and stained by HE for morphological analysis. Red and white muscle samples were used to determine MyoD, myogenin, and myostatin genes expression by Real-time Polymerase Chain Reaction. Although MyoD and myogenin were not statistically different in the two types of muscles, myostatin was significantly higher in the white rather than in the red muscle. Results show the muscle growth characteristics of the species and may be helpful for improving aquaculture management programs.

Rearing temperature induces changes in muscle growth and gene expression in juvenile pacu (Piaractus mesopotamicus)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Heart Failure-Induced Diaphragm Myopathy

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Morfologia e expressão dos MRF’s no músculo esquelético de ratos submetidos a estímulo atrófico e recuperação por treinamento físico

Recent research advances in understanding the cellular and molecular mechanisms that underlie the processes of hypertrophy and atrophy. This may contribute to development of effective therapeutic strategies to attenuate or block the loss of muscle tissue associated with aging and pathological conditions. In this context, myogenic factors that control the activity of satellite cells have been studied to better understand the events involved in the recovery of muscle mass. Among them, we highlight the Myogenic Regulatory Factors (MRFs), which have been described as potential mediators of muscle growth. The objectives of this study evaluated the morphofunctional adaptations and gene expression of MRFs (MyoD and myogenin) in skeletal muscle (soleus) subjected to an atrophic stimulus followed by physical training. It was used 64 male Wistar rats (80 days, 250 to 300 g), divided into 8 groups (n = 8): C: control animals a week, I: Animals immobilized a week, C3: control animals 3 days; R3: Animals immobilized and recovered for 3 days, T3: Animals immobilized and submitted to exercise for 3 days; C7: Animals controls 7 days; R7: Animals immobilized and subsequently recovered by 7 days, T7: Animals immobilized and subsequently subjected to exercise for 7 days. Initially, the animals in groups I, R3, R7, T3 and T7, were submitted to 7 days of immobilization of the hind limb. Muscle atrophy was confirmed after a direct statistical comparison of the values of cross-sectional area (CSA) of muscle fibers studied in animals in groups I and C, sacrificed immediately after the immobilization period. Then, the groups T3 and T7 were submitted a rehabilitation program with muscle aerobic exercise (swimming) for 3 and 7 days respectively. The groups C, C3 and C7 were kept without stimulus atrophic and were not subjected to exercise. At the end of the experiment, the animals were sacrified and the soleus muscle removed. The quantitative analysis of gene expression ...

Efeitos do hormônio do crescimento sobre vias de sinalização intracelular na miopatia associada à insuficiência cardíaca de ratos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Mice with a targeted disruption of the Fgfrl1 gene die at birth due to alterations in the diaphragm

FGFRL1 is a recently discovered member of the fibroblast growth factor receptor family that is lacking the intracellular tyrosine kinase domain. To elucidate the function of the novel receptor, we created mice with a targeted disruption of the Fgfrl1 gene. These mice develop normally until term, but die within a few minutes after birth due to respiratory failure. The respiratory problems are explained by a significant reduction in the size of the diaphragm muscle, which is not sufficient to inflate the lungs after birth. The remaining portion of the diaphragm muscle appears to be well developed and innervated. It consists of differentiated myofibers with nuclei at the periphery. Fast and slow muscle fibers occur in normal proportions. The myogenic regulatory factors MyoD, Myf5, myogenin and Mrf4 and the myocyte enhancer factors Mef2A, Mef2B, Mef2C and Mef2D are expressed at normal levels. Experiments with a cell culture model involving C2C12 myoblasts show that Fgfrl1 is expressed during the late stages of myotube formation. Other skeletal muscles do not appear to be affected in the Fgfrl1 deficient mice. Thus, Fgfrl1 plays a critical role in the development of the diaphragm.

Myogenin modulates exercise endurance by altering skeletal muscle metabolism

The function of myogenic regulatory factors (MRFs) during adult life is not well understood. The requirement of one of these MRFs, myogenin (Myog), during embryonic muscle development suggests an equally important role in adult muscle. In this study, we have determined the function of myogenin during adult life using a conditional allele of Myog. In contrast to embryonic development, myogenin is not required for adult viability, and Myog-deleted mice exhibited no remarkable phenotypic changes during sedentary life. Remarkably, sedentary Myog-deleted mice demonstrated enhanced exercise endurance during involuntary treadmill running. Altered blood glucose and lactate levels in sedentary Myog-deleted mice after exhaustion suggest an enhanced glycolytic metabolism and an ability to excessively deplete muscle and liver glycogen stores. Traditional changes associated with enhanced exercise endurance, such as fiber type switching, and increased oxidative potential, were not detected in sedentary Myog-deleted mice. After long-term voluntary exercise, trained Myog-deleted mice demonstrated an enhanced adaptive response to exercise. Trained Myog-deleted mice exhibited superior exercise endurance associated with an increased proportion of slow-twitch fibers and increased oxidative capacity. In a parallel experiment, dystrophin-deficient young adult mice showed attenuated muscle fatigue following the deletion of Myog. These results demonstrate a novel and unexpected role for myogenin in modulating skeletal muscle metabolism.

Isolation, characterization and transcriptional regulation of {\it Xenopus myod\/}

I have cloned cDNAs corresponding to two distinct genes, Xlmf1 and Xlmf25, which encode skeletal muscle-specific, transcriptional regulatory proteins. These proteins are members of the helix-loop-helix family of DNA binding factors, and are most homologous to MyoD1. These two genes have disparate temporal expression patterns during early embryogenesis; although, both transcripts are present exclusively in skeletal muscle of the adult. Xlmf1 is first detected 7 hours after fertilization, shortly after the midblastula transition. Xlmf25 is detected in maternal stores of mRNA, during early cleavage stages of the embryo and throughout later development. Both Xlmf1 and Xlmf25 transcripts are detected prior to the expression of other, previously characterized, muscle-specific genes. The ability of Xlmf1 and Xlmf25 to convert mouse 10T1/2 fibroblasts to a myogenic phenotype demonstrates their activity as myogenic regulatory factors. Additionally, Xlmf1 and Xlmf25 can directly transactivate a reporter gene linked to the muscle-specific, muscle creatine kinase (MCK) enhancer. The functional properties of Xlmf1 and Xlmf25 proteins were further explored by investigating their interactions with the binding site in the MCK enhancer. Analysis of dissociation rates revealed that Xlmf25-E12 dimers had a two-fold lower avidity for this site than did Xlmf1-E12 dimers. Clones containing genomic sequence of Xlmf1 and Xlmf25 have been isolated. Reporter gene constructs containing a lac-z gene driven by Xlmf1 regulatory sequences were analyzed by embryo injections and transfections into cultured muscle cells. Elements within $-$200 bp of the transcription start site can promote high levels of muscle specific expression. Embryo injections show that 3500 bp of upstream sequence is sufficient to drive somite specific expression. EMSAs and DNAse I footprint analysis has shown the discrete interaction of factors with several cis-elements within 200 bp of the transcription start site. Mutation of several of these elements shows a positive requirement for two CCAAT boxes and two E boxes. It is evident from the work performed with this promoter that Xlmf1 is tightly regulated during muscle cell differentiation. This is not surprising given the fact that its gene product is crucial to the determination of cell fate choices. ^

Muscle LIM Proteins Are Associated with Muscle Sarcomeres and Require dMEF2 for Their Expression during Drosophila Myogenesis

A genetic hierarchy of interactions, involving myogenic regulatory factors of the MyoD and myocyte enhancer-binding 2 (MEF2) families, serves to elaborate and maintain the differentiated muscle phenotype through transcriptional regulation of muscle-specific target genes. Much work suggests that members of the cysteine-rich protein (CRP) family of LIM domain proteins also play a role in muscle differentiation; however, the specific functions of CRPs in this process remain undefined. Previously, we characterized two members of the Drosophila CRP family, the muscle LIM proteins Mlp60A and Mlp84B, which show restricted expression in differentiating muscle lineages. To extend our analysis of Drosophila Mlps, we characterized the expression of Mlps in mutant backgrounds that disrupt specific aspects of muscle development. We show a genetic requirement for the transcription factor dMEF2 in regulating Mlp expression and an ability of dMEF2 to bind, in vitro, to consensus MEF2 sites derived from those present in Mlp genomic sequences. These data suggest that the Mlp genes may be direct targets of dMEF2 within the genetic hierarchy controlling muscle differentiation. Mutations that disrupt myoblast fusion fail to affect Mlp expression. In later stages of myogenic differentiation, which are dedicated primarily to assembly of the contractile apparatus, we analyzed the subcellular distribution of Mlp84B in detail. Immunofluorescent studies revealed the localization of Mlp84B to muscle attachment sites and the periphery of Z-bands of striated muscle. Analysis of mutations that affect expression of integrins and α-actinin, key components of these structures, also failed to perturb Mlp84B distribution. In conclusion, we have used molecular epistasis analysis to position Mlp function downstream of events involving mesoderm specification and patterning and concomitant with terminal muscle differentiation. Furthermore, our results are consistent with a structural role for Mlps as components of muscle cytoarchitecture.

Evidence for a Myotomal Hox/Myf Cascade Governing Nonautonomous Control of Rib Specification within Global Vertebral Domains

Hox genes are essential for the patterning of the axial skeleton. Hox group 10 has been shown to specify the lumbar domain by setting a rib-inhibiting program in the presomitic mesoderm (PSM). We have now produced mice with ribs in every vertebra by ectopically expressing Hox group 6 in the PSM, indicating that Hox genes are also able to specify the thoracic domain. We show that the information provided by Hox genes to specify rib-containing and rib-less areas is first interpreted in the myotome through the regional-specific control of Myf5 and Myf6 expression. This information is then transmitted to the sclerotome by a system that includes FGF and PDGF signaling to produce vertebrae with or without ribs at different axial levels. Our findings offer a new perspective of how Hox genes produce global patterns in the axial skeleton and support a redundant nonmyogenic role of Myf5 and Myf6 in rib formation.