Regulation of expression of avian slow myosin heavy-chain isoforms.
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ABSTRACT:
SUBMITTER: Reid SK
PROVIDER: S-EPMC1138689 | biostudies-other | 1989 Jun
REPOSITORIES: biostudies-other
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Project description:Multiple types of fast and slow skeletal muscle fibers form during early embryogenesis in vertebrates. In zebrafish, formation of the earliest slow myofibers in fin muscles requires expression of the zinc-finger transcriptional repressor Prdm1 (also known as Blimp1). To further understand how the role of Prdm1 in early myogenesis may vary through evolution and during development, we have now analyzed Prdm1 expression in the diverse types of myotubes that form in culture from somitic, embryonic, and fetal chicken myoblasts.In cultures of somitic, embryonic limb, and fetal limb chicken cells, we found that Prdm1 was expressed in all of the differentiated muscle cells that formed, including those that expressed only fast myosin heavy chain isoforms, as well as those that co-expressed both fast and slow myosin heavy chain isoforms. Prdm1 was also expressed in Pax7-positive myoblasts, as well as in non-myogenic cells in the cultures. Furthermore, though all differentiated cells in control somite cultures co-expressed fast and slow myosin heavy chains, antisense knockdown of Prdm1 expression inhibited the formation of these co-expressing cells in somite cultures.In chicken myogenic cell cultures, Prdm1 was expressed in most Pax7-positive myoblasts and in all differentiated muscle cells, irrespective of the developmental stage of cell donor or the pattern of fast and slow myosin heavy chains expressed in the differentiated cells that were formed. Thus, Prdm1 was expressed in myogenic cells prior to terminal differentiation; and, after differentiation, Prdm1 expression was not limited to cells that expressed slow myosin heavy chain isoforms. In addition, Prdm1 appeared to be required for differentiation of the somitic myocytes, which are the earliest myocytes to form in the avian embryo.
| S-EPMC2848592 | biostudies-literature
Project description:Avian myogenesis is partly characterized by commitment of distinct myoblast cell lineages to the formation of specific muscle fiber types. Previous studies have identified the transcription factor EMX2 as a regulator of slow myosin heavy chain 2 (MyHC2) gene expression in fast/slow primary muscle fibers. We report here the interaction of EMX2 with the slow MyHC2 transcriptional regulatory region in fast/slow embryonic muscle fibers. Promoter activity and electromobility shift assays localized the site of interaction of EMX2 with the slow MyHC2 gene within a defined binding site located between 3336 and 3326bp from the 3' end of the cloned slow MyHC2 DNA containing the transcriptional regulatory region. Using clonally-derived myoblasts stably committed to the formation of fast/slow muscle fibers, we also report the effect of altered EMX2 gene expression on genome-wide gene expression within these myoblasts. Increased EMX2 gene expression in fast/slow myoblasts caused altered gene expression of 1185 genes, indicating that EMX2 plays a central role in the gene expression profile of embryonic myoblasts.
| S-EPMC5660925 | biostudies-literature
Project description:BackgroundSkeletal muscle function is essential for health, and it depends on the proper activity of myofibers and their innervating motor neurons. Each adult muscle is composed of different types of myofibers with distinct contractile and metabolic characteristics. The proper balance of myofiber types is disrupted in most muscle degenerative disorders, representing another factor compromising muscle function. One promising therapeutic approach for the treatment of these diseases is cell replacement based on the targeted differentiation of pluripotent stem cells (PSCs) towards the myogenic lineage. We have previously shown that transient induction of Pax3 or Pax7 in PSCs allows for the generation of skeletal myogenic progenitors endowed with myogenic regenerative potential, but whether they contribute to different fiber types remains unknown.ResultsHere, we investigate the fiber type composition of mouse PSC-derived myofibers upon their transplantation into dystrophic and non-dystrophic mice. Our data reveal that PSC-derived myofibers express slow and oxidative myosin heavy-chain isoforms, along with developmental myosins, regardless of the recipient background. Furthermore, transplantation of the mononuclear cell fraction re-isolated from primary grafts into secondary recipients results in myofibers that maintain preferential expression of slow and oxidative myosin heavy-chain isoforms but no longer express developmental myosins, thus indicating postnatal composition.ConclusionsConsidering oxidative fibers are commonly spared in the context of dystrophic pathogenesis, this feature of PSC-derived myofibers could be advantageous for therapeutic applications.
| S-EPMC7268645 | biostudies-literature
Project description:BackgroundSkeletal muscles consist of fibers of differing contractility and metabolic properties, which are primarily determined by the content of myosin heavy chain (MYH) isoforms (MYH7, MYH2, MYH1, and MYH4). The regulation of Myh genes transcription depends on three-dimensional chromatin conformation interaction, but the mechanistic details remain to be determined.ResultsIn this study, we characterized the interaction profiles of Myh genes using 4C-seq (circular chromosome conformation capture coupled to high-throughput sequencing). The interaction profile of Myh genes changed between fast quadriceps and slow soleus muscles. Combining chromatin immunoprecipitation-sequencing (ChIP-seq) and transposase accessible chromatin with high-throughput sequencing (ATAC-seq), we found that a 38 kb intergenic region interacting simultaneously with fast Myh genes promoters controlled the coordinated expression of fast Myh genes. We also identified four active enhancers of Myh7, and revealed that binding of MYOG and MYOD increased the activity of Myh7 enhancers.ConclusionsThis study provides new insight into the chromatin interactions that regulate Myh genes expression.
| S-EPMC9288694 | biostudies-literature
Project description:Background:Immunohistochemical studies of hearts from the lesser spotted dogfish, Scyliorhinus canicula (Chondrichthyes) revealed that the pan-myosin heavy chain (pan-MyHC) antibody MF20 homogeneously labels all the myocardium, while the pan-MyHC antibody A4.1025 labels the myocardium of the inflow (sinus venosus and atrium) but not the outflow (ventricle and conus arteriosus) cardiac segments, as opposed to other vertebrates. We hypothesized that the conventional pattern of cardiac MyHC isoform distribution present in most vertebrates, i.e. MYH6 in the inflow and MYH7 in the outflow segments, has evolved from a primitive pattern that persists in Chondrichthyes. In order to test this hypothesis, we conducted protein detection techniques to identify the MyHC isoforms expressed in adult dogfish cardiac segments and to assess the pan-MyHC antibodies reactivity against the cardiac segments of representative species from different vertebrate groups. Results:Western and slot blot results confirmed the specificity of MF20 and A4.1025 for MyHC in dogfish and their differential reactivity against distinct myocardial segments. HPLC-ESI-MS/MS and ESI-Quadrupole-Orbitrap revealed abundance of MYH6 and MYH2 in the inflow and of MYH7 and MYH7B in the outflow segments. Immunoprecipitation showed higher affinity of A4.1025 for MYH2 and MYH6 than for MYH7 and almost no affinity for MYH7B. Immunohistochemistry showed that A4.1025 signals are restricted to the inflow myocardial segments of elasmobranchs, homogeneous in all myocardial segments of teleosts and acipenseriforms, and low in the ventricle of polypteriforms. Conclusions:The cardiac inflow and outflow segments of the dogfish show predominance of fast- and slow-twitch MyHC isoforms respectively, what can be considered a synapomorphy of gnathostomes. The myocardium of the dogfish contains two isomyosins (MYH2 and MYH7B) not expressed in the adult heart of other vertebrates. We propose that these isomyosins lost their function in cardiac contraction during the evolution of gnathostomes, the later acquiring a regulatory role in myogenesis through its intronic miRNA. Loss of MYH2 and MYH7B expression in the heart possibly occurred before the origin of Osteichthyes, being the latter reacquired in polypteriforms. We raise the hypothesis that the slow tonic MYH7B facilitates the peristaltic contraction of the conus arteriosus of fish with a primitive cardiac anatomical design and of the vertebrate embryo.
| S-EPMC6558913 | biostudies-literature
Project description:The myosin II motors are ATP-powered force-generating machines driving cardiac and muscle contraction. Myosin II heavy chain isoform-beta (β-MyHC) is primarily expressed in the ventricular myocardium and in slow-twitch muscle fibers, such as M. soleus. M. soleus-derived myosin II (SolM-II) is often used as an alternative to the ventricular β-cardiac myosin (βM-II); however, the direct assessment of biochemical and mechanical features of the native myosins is limited. By employing optical trapping, we examined the mechanochemical properties of native myosins isolated from the rabbit heart ventricle and soleus muscles at the single-molecule level. We found purified motors from the two tissue sources, despite expressing the same MyHC isoform, displayed distinct motile and ATPase kinetic properties. We demonstrate βM-II was approximately threefold faster in the actin filament-gliding assay than SolM-II. The maximum actomyosin (AM) detachment rate derived in single-molecule assays was also approximately threefold higher in βM-II, while the power stroke size and stiffness of the "AM rigor" crossbridge for both myosins were comparable. Our analysis revealed a higher AM detachment rate for βM-II, corresponding to the enhanced ADP release rates from the crossbridge, likely responsible for the observed differences in the motility driven by these myosins. Finally, we observed a distinct myosin light chain 1 isoform (MLC1sa) that associates with SolM-II, which might contribute to the observed kinetics differences between βM-II and SolM-II. These results have important implications for the choice of tissue sources and justify prerequisites for the correct myosin heavy and light chains to study cardiomyopathies.
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Project description:BackgroundWhile the myosin heavy chain IIb isoform (MyHC-IIb) is the predominant motor protein in most skeletal muscles of rats and mice, the messenger RNA (mRNA) for this isoform is only expressed in a very small subset of specialized muscles in adult large mammals, including humans.ResultsWe identify the DNA sequences limiting MyHC-IIb expression in humans and explore the activation of this gene in human skeletal muscle. We demonstrate that the transcriptional activity of ~1.0 kb of the human MyHC-IIb promoter is greatly reduced compared to that of the corresponding mouse sequence in both mouse and human myotubes in vitro and show that nucleotide differences that eliminate binding sites for myocyte enhancer factor 2 (MEF2) and serum response factor (SRF) account for this difference. Despite these differences, we show that MyHC-IIb mRNA is expressed in fetal human muscle cells and that MyHC-IIb mRNA is significantly up-regulated in the skeletal muscle of Duchene muscular dystrophy patients.ConclusionsThese data identify the genetic basis for a key phenotypic difference between the muscles of large and small mammals, and demonstrate that mRNA expression of the MyHC-IIb gene can be re-activated in human limb muscle undergoing profound degeneration/regeneration.
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Project description:Changes in the myosin phenotype of differentiated muscle are a prominent feature of the adaptation of the tissue to a variety of physiological stimuli. In the present study the molecular basis of changes in the proportion of myosin isoenzymes in rat skeletal muscle which occur during compensatory hypertrophy caused by the combined removal of synergist muscles and spontaneous running exercise was investigated. The relative amounts of sarcomeric myosin heavy (MHC)- and light (MLC)-chain mRNAs in the plantaris (fast) and soleus (slow) muscles from rats was assessed with cDNA probes specific for different MHC and MLC genes. Changes in the proportion of specific MHC mRNA levels were in the same direction as, and of similar magnitude to, changes in the proportion of myosin isoenzymes encoded for by the mRNAs. No significant changes in the proportion of MLC proteins or mRNA were detected. However, high levels of MLC3 mRNA were measured in both normal and hypertrophied soleus muscles which contained only trace amounts of MLC3 protein. Small amounts of embryonic and neonatal MHC mRNAs were induced in both muscles during hypertrophy. We conclude that the change in the pattern of myosin isoenzymes during skeletal-muscle adaptation to work overload is a consequence of changes in specific MHC mRNA levels.
| S-EPMC1135643 | biostudies-other
Project description:We show that a 2.6kb fragment of the muscle myosin heavy-chain gene (Mhc) of Drosophila melanogaster (containing 458 base pairs of upstream sequence, the first exon, the first intron and the beginning of the second exon) drives expression in all muscles. Comparison of the minimal promoter to Mhc genes of 10 Drosophila species identified putative regulatory elements in the upstream region and in the first intron. The first intron is required for expression in four small cells of the tergal depressor of the trochanter (jump) muscle and in the indirect flight muscle. The 3'-end of this intron is important for Mhc transcription in embryonic body wall muscle and contains AT-rich elements that are protected from DNase I digestion by nuclear proteins of Drosophila embryos. Sequences responsible for expression in embryonic, adult body wall and adult head muscles are present both within and outside the intron. Elements important for expression in leg muscles and in the large cells of the jump muscle flank the intron. We conclude that multiple transcriptional regulatory elements are responsible for Mhc expression in specific sets of Drosophila muscles.
| S-EPMC2002476 | biostudies-literature
Project description:Nonmuscle myosin-II is an actin-based motor that converts chemical energy into force and movement, and thus functions as a key regulator of the eukaryotic cytoskeleton. Although it is established that phosphorylation on the regulatory light chain increases the actin-activated MgATPase activity of the motor and promotes myosin-II filament assembly, studies have begun to characterize alternative mechanisms that regulate filament assembly and disassembly. These investigations have revealed that all three nonmuscle myosin-II isoforms are subject to additional regulatory controls, which impact diverse cellular processes. In this review, we discuss current knowledge on mechanisms that regulate the oligomerization state of nonmuscle myosin-II filaments by targeting the myosin heavy chain.
| S-EPMC4201608 | biostudies-literature