scholarly journals Altered Skeletal Muscle Phenotypes in Calcineurin Aα and Aβ Gene-Targeted Mice

2003 ◽  
Vol 23 (12) ◽  
pp. 4331-4343 ◽  
Author(s):  
Stephanie A. Parsons ◽  
Benjamin J. Wilkins ◽  
Orlando F. Bueno ◽  
Jeffery D. Molkentin
Keyword(s):  
Skeletal Muscle ◽  
Fiber Type ◽  
Critical Role ◽  
Cell Types ◽  
Luciferase Reporter ◽  
Myoblast Differentiation ◽  
Activated T Cells ◽  
Slow Fiber ◽  
Calcineurin Signaling

ABSTRACT Calcineurin is a calcium-regulated serine-threonine protein phosphatase that controls developmental and inducible biological responses in diverse cell types, in part through activation of the transcription factor nuclear factor of activated T cells (NFAT). In skeletal muscle, calcineurin has been implicated in the regulation of myoblast differentiation, hypertrophy of mature myofibers, and fiber type switching in response to alterations in intracellular calcium concentration. However, considerable disagreement persists about the functional role of calcineurin signaling in each of these processes. Here we evaluated the molecular phenotypes of skeletal muscle from both calcineurin Aα and calcineurin Aβ gene-targeted mice. Calcineurin Aα was observed to be the predominant catalytic isoform expressed in nearly all skeletal muscles examined. Neither calcineurin Aα or Aβ null mice showed any gross growth-related alterations in skeletal muscle, nor was fiber size or number altered in glycolytic/fast muscle types. In contrast, both calcineurin Aα and Aβ gene-targeted mice demonstrated an alteration in myofiber number in the soleus, an oxidative/slow-type muscle. More significantly, calcineurin Aα and Aβ gene-targeted mice showed a dramatic down-regulation in the oxidative/slow fiber type program in multiple muscles (both slow and fast). Associated with this observation, NFAT-luciferase reporter transgenic mice showed significantly greater activity in slow fiber-containing muscles than in fast. However, only calcineurin Aα null mice showed a defect in NFAT nuclear occupancy or NFAT-luciferase transgene activity in vivo. Collectively, our results suggest that calcineurin signaling plays a critical role in regulating skeletal muscle fiber type switching but not hypertrophy. Our results also suggest that fiber type switching occurs through an NFAT-independent mechanism.

scholarly journals Creating Interactions between Tissue-Engineered Skeletal Muscle and the Peripheral Nervous System

2016 ◽  
Vol 202 (3-4) ◽  
pp. 143-158 ◽  
Author(s):  
Alec S.T. Smith ◽  
Samantha L. Passey ◽  
Neil R.W. Martin ◽  
Darren J. Player ◽  
Vivek Mudera ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Motor Neurons ◽  
Muscle Development ◽  
Functional Performance ◽  
Cell Types ◽  
Original Data ◽  
Synaptic Proteins ◽  
Myoblast Differentiation

Effective models of mammalian tissues must allow and encourage physiologically (mimetic) correct interactions between co-cultured cell types in order to produce culture microenvironments as similar as possible to those that would normally occur in vivo. In the case of skeletal muscle, the development of such a culture model, integrating multiple relevant cell types within a biomimetic scaffold, would be of significant benefit for investigations into the development, functional performance, and pathophysiology of skeletal muscle tissue. Although some work has been published regarding the behaviour of in vitro muscle models co-cultured with organotypic slices of CNS tissue or with stem cell-derived neurospheres, little investigation has so far been made regarding the potential to maintain isolated motor neurons within a 3D biomimetic skeletal muscle culture platform. Here, we review the current state of the art for engineering neuromuscular contacts in vitro and provide original data detailing the development of a 3D collagen-based model for the co-culture of primary muscle cells and motor neurons. The devised culture system promotes increased myoblast differentiation, forming arrays of parallel, aligned myotubes on which areas of nerve-muscle contact can be detected by immunostaining for pre- and post-synaptic proteins. Quantitative RT-PCR results indicate that motor neuron presence has a positive effect on myotube maturation, suggesting neural incorporation influences muscle development and maturation in vitro. The importance of this work is discussed in relation to other published neuromuscular co-culture platforms along with possible future directions for the field.

scholarly journals Loss of Nup210 results in muscle repair delays and age-associated alterations in muscle integrity

2021 ◽  
Vol 5 (3) ◽  
pp. e202101216
Author(s):  
Stephen Sakuma ◽  
Ethan YS Zhu ◽  
Marcela Raices ◽  
Pan Zhang ◽  
Rabi Murad ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Knockout Mice ◽  
Muscle Function ◽  
Fiber Type ◽  
Myoblast Differentiation ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Muscle Repair ◽  
Pore Complexes

Nuclear pore complexes, the channels connecting the nucleus with the cytoplasm, are built by multiple copies of ∼30 proteins called nucleoporins. Recent evidence has exposed that nucleoporins can play cell type-specific functions. Despite novel discoveries into the cellular functions of nucleoporins, their role in the regulation of mammalian tissue physiology remains mostly unexplored because of a limited number of nucleoporin mouse models. Here we show that ablation of Nup210/Gp210, a nucleoporin previously identified to play a role in myoblast differentiation and Zebrafish muscle maturation, is dispensable for skeletal muscle formation and growth in mice. We found that although primary satellite cells from Nup210 knockout mice can differentiate, these animals show delayed muscle repair after injury. Moreover, Nup210 knockout mice display an increased percentage of centrally nucleated fibers and abnormal fiber type distribution as they age. Muscle function experiments also exposed that Nup210 is required for muscle endurance during voluntary running. Our findings indicate that in mammals, Nup210 is important for the maintenance of skeletal muscle integrity and for proper muscle function providing novel insights into the in vivo roles of nuclear pore complex components.

scholarly journals Effects of sarcolipin deletion on skeletal muscle adaptive responses to functional overload and unload

2017 ◽  
Vol 313 (2) ◽  
pp. C154-C161 ◽  
Author(s):  
Val A. Fajardo ◽  
Bradley A. Rietze ◽  
Paige J. Chambers ◽  
Catherine Bellissimo ◽  
Eric Bombardier ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Fiber Type ◽  
Ectopic Expression ◽  
Oxidative Capacity ◽  
Adaptive Responses ◽  
Slow Fiber ◽  
Fast Fiber ◽  
Fiber Number ◽  
Type Shift ◽  
Calcineurin Signaling

Overexpression of sarcolipin (SLN), a regulator of sarco(endo)plasmic reticulum Ca2+-ATPases (SERCAs), stimulates calcineurin signaling to enhance skeletal muscle oxidative capacity. Some studies have shown that calcineurin may also control skeletal muscle mass and remodeling in response to functional overload and unload stimuli by increasing myofiber size and the proportion of slow fibers. To examine whether SLN might mediate these adaptive responses, we performed soleus and gastrocnemius tenotomy in wild-type (WT) and Sln-null ( Sln−/−) mice and examined the overloaded plantaris and unloaded/tenotomized soleus muscles. In the WT overloaded plantaris, we observed ectopic expression of SLN, myofiber hypertrophy, increased fiber number, and a fast-to-slow fiber type shift, which were associated with increased calcineurin signaling (NFAT dephosphorylation and increased stabilin-2 protein content) and reduced SERCA activity. In the WT tenotomized soleus, we observed a 14-fold increase in SLN protein, myofiber atrophy, decreased fiber number, and a slow-to-fast fiber type shift, which were also associated with increased calcineurin signaling and reduced SERCA activity. Genetic deletion of Sln altered these physiological outcomes, with the overloaded plantaris myofibers failing to grow in size and number, and transition towards the slow fiber type, while the unloaded soleus muscles exhibited greater reductions in fiber size and number, and an accelerated slow-to-fast fiber type shift. In both the Sln−/− overloaded and unloaded muscles, these findings were associated with elevated SERCA activity and blunted calcineurin signaling. Thus, SLN plays an important role in adaptive muscle remodeling potentially through calcineurin stimulation, which could have important implications for other muscle diseases and conditions.

scholarly journals Gastric Hyperplasia and Increased Proliferative Responses of Lymphocytes in Mice Lacking the COOH-terminal Ankyrin Domain of NF-κB2

1997 ◽  
Vol 186 (7) ◽  
pp. 999-1014 ◽  
Author(s):  
Hideaki Ishikawa ◽  
Daniel Carrasco ◽  
Estefania Claudio ◽  
Rolf-Peter Ryseck ◽  
Rodrigo Bravo
Keyword(s):  
T Cells ◽  
Lymphocyte Proliferation ◽  
Cytokine Production ◽  
Cell Types ◽  
Homozygous Deletion ◽  
Binding Activity ◽  
Activated T Cells ◽  
Physiological Relevance

The nfkb2 gene encodes the p100 precursor which produces the p52 protein after proteolytic cleavage of its COOH-terminal domain. Although the p52 product can act as an alternative subunit of NF-κB, the p100 precursor is believed to function as an inhibitor of Rel/NF-κB activity by cytoplasmic retention of Rel/NF-κB complexes, like other members of the IκB family. However, the physiological relevance of the p100 precursor as an IκB molecule has not been understood. To assess the role of the precursor in vivo, we generated, by gene targeting, mice lacking p100 but still containing a functional p52 protein. Mice with a homozygous deletion of the COOH-terminal ankyrin repeats of NF-κB2 (p100−/−) had marked gastric hyperplasia, resulting in early postnatal death. p100−/− animals also presented histopathological alterations of hematopoietic tissues, enlarged lymph nodes, increased lymphocyte proliferation in response to several stimuli, and enhanced cytokine production in activated T cells. Dramatic induction of nuclear κB–binding activity composed of p52-containing complexes was found in all tissues examined and also in stimulated lymphocytes. Thus, the p100 precursor is essential for the proper regulation of p52-containing Rel/NF-κB complexes in various cell types and its absence cannot be efficiently compensated for by other IκB proteins.

scholarly journals Large G protein α-subunit XLαs limits clathrin-mediated endocytosis and regulates tissue iron levels in vivo

2017 ◽  
Vol 114 (45) ◽  
pp. E9559-E9568 ◽  
Author(s):  
Qing He ◽  
Richard Bouley ◽  
Zun Liu ◽  
Marc N. Wein ◽  
Yan Zhu ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
G Protein ◽  
Critical Role ◽  
Hek293 Cells ◽  
Activity Levels ◽  
Α Subunit ◽  
Proteomic Screen ◽  
Protein Levels ◽  
G Protein Α Subunit

Alterations in the activity/levels of the extralarge G protein α-subunit (XLαs) are implicated in various human disorders, such as perinatal growth retardation. Encoded by GNAS, XLαs is partly identical to the α-subunit of the stimulatory G protein (Gsα), but the cellular actions of XLαs remain poorly defined. Following an initial proteomic screen, we identified sorting nexin-9 (SNX9) and dynamins, key components of clathrin-mediated endocytosis, as binding partners of XLαs. Overexpression of XLαs in HEK293 cells inhibited internalization of transferrin, a process that depends on clathrin-mediated endocytosis, while its ablation by CRISPR/Cas9 in an osteocyte-like cell line (Ocy454) enhanced it. Similarly, primary cardiomyocytes derived from XLαs knockout (XLKO) pups showed enhanced transferrin internalization. Early postnatal XLKO mice showed a significantly higher degree of cardiac iron uptake than wild-type littermates following iron dextran injection. In XLKO neonates, iron and ferritin levels were elevated in heart and skeletal muscle, where XLαs is normally expressed abundantly. XLKO heart and skeletal muscle, as well as XLKO Ocy454 cells, showed elevated SNX9 protein levels, and siRNA-mediated knockdown of SNX9 in XLKO Ocy454 cells prevented enhanced transferrin internalization. In transfected cells, XLαs also inhibited internalization of the parathyroid hormone and type 2 vasopressin receptors. Internalization of transferrin and these G protein-coupled receptors was also inhibited in cells expressing an XLαs mutant missing the Gα portion, but not Gsα or an N-terminally truncated XLαs mutant unable to interact with SNX9 or dynamin. Thus, XLαs restricts clathrin-mediated endocytosis and plays a critical role in iron/transferrin uptake in vivo.

scholarly journals In vivo analysis of the myosin heavy chain IIB promoter region

1998 ◽  
Vol 274 (3) ◽  
pp. C681-C687 ◽  
Author(s):  
Steven J. Swoap
Keyword(s):  
Reporter Gene ◽  
Luciferase Activity ◽  
Fiber Type ◽  
Firefly Luciferase ◽  
Renilla Luciferase ◽  
Luciferase Reporter ◽  
Base Pairs ◽  
Specific Expression ◽  
Mhc Iib

The myosin heavy chain (MHC) IIB gene is preferentially expressed in fast-twitch muscles of the hindlimb, such as the tibialis anterior (TA). The molecular mechanism(s) for this preferential expression are unknown. The goals of the current study were 1) to determine whether the cloned region of the MHC IIB promoter contains the necessary cis-acting element(s) to drive fiber-type-specific expression of this gene in vivo, 2) to determine which region within the promoter is responsible for fiber-type-specific expression, and 3) to determine whether transcription off of the cloned region of the MHC IIB promoter accurately mimics endogenous gene expression in a muscle undergoing a fiber-type transition. To accomplish these goals, a 2.6-kilobase fragment of the promoter-enhancer region of the MHC IIB gene was cloned upstream of the firefly luciferase reporter gene and coinjected with pRL-cytomegalovirus (CMV) (CMV promoter driving the renilla luciferase reporter) into the TA and the slow soleus muscle. Firefly luciferase activity relative to renilla luciferase activity within the TA was 35-fold greater than within the soleus. Deletional analysis demonstrated that only the proximal 295 base pairs (pGL3IIB0.3) were required to maintain this muscle-fiber-type specificity. Reporter gene expression of pGL3IIB0.3 construct was significantly upregulated twofold in unweighted soleus muscles compared with normal soleus muscles. Thus the region within the proximal 295 base pairs of the MHC IIB gene contains at least one element that can drive fiber-type-specific expression of a reporter gene.

Abstract P070: NEU3 Sialidase Overexpression Activates Cell Survival in Murine Skeletal Myoblasts C2C12 and Protects Them from Hypoxia

2011 ◽  
Vol 109 (suppl_1) ◽  
Author(s):  
Luigi Anastasia ◽  
Raffaella Scaringi ◽  
Nadia Papini ◽  
Andrea Garatti ◽  
Lorenzo Menicanti ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Egf Receptor ◽  
Day Treatment ◽  
Horse Serum ◽  
Critical Role ◽  
Cell Loss ◽  
Myoblast Differentiation ◽  
Signalling Pathways ◽  
Skeletal Myoblasts ◽  
Culturing Conditions

Membrane-bound sialidase NEU3 increase during skeletal muscle differentiation has been shown to protect myoblasts from apoptosis and drive the differentiation process [1]. Thus, the objective of this study was to assess whether up-regulation of NEU3 would enhance the ability of murine skeletal muscle cells to resist to hypoxia, ultimately opposing cell death. We found that C2C12 myoblasts overexpressing NEU3 (L-NEU3) became highly resistant to 1% oxygen or 200 mM deferoxamine induced hypoxia. Moreover, L-NEU3 myoblasts survived a seven-day treatment of combined hypoxia and low serum (2% horse serum used to induce myoblast differentiation), without any significant cell loss. On the contrary, wild type C2C12 could not resist to these culturing conditions and all died within 48h. Real Time PCR showed NEU3 expression increase during all hypoxic treatments both in C2C12 and L-NEU3 cells, suggesting an endogenous NEU3 activation under these conditions. Moreover, we found that NEU3 over-expression activated pro-survival signalling pathways through up-regulation and activation of EGF receptor. Overall, our data support the hypothesis that NEU3 may play a critical role in the response of skeletal myoblasts to hypoxia and the preservation of cell viability by activating pro-survival signalling pathways. [1] Anastasia L. et al. J.Biol.Chem. 2008, 283 (52): 36265–36271.

Overlapping functions of the myogenic bHLH genes MRF4 and MyoD revealed in double mutant mice

Development ◽  
1998 ◽  
Vol 125 (13) ◽  
pp. 2349-2358 ◽  
Author(s):  
A. Rawls ◽  
M.R. Valdez ◽  
W. Zhang ◽  
J. Richardson ◽  
W.H. Klein ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Double Mutant ◽  
Muscle Development ◽  
Expression Patterns ◽  
Muscle Fibers ◽  
Mutant Mice ◽  
Myoblast Differentiation ◽  
Bhlh Genes ◽  
Bhlh Factors

The myogenic basic helix-loop-helix (bHLH) genes - MyoD, Myf5, myogenin and MRF4 - exhibit distinct, but overlapping expression patterns during development of the skeletal muscle lineage and loss-of-function mutations in these genes result in different effects on muscle development. MyoD and Myf5 have been shown to act early in the myogenic lineage to establish myoblast identity, whereas myogenin acts later to control myoblast differentiation. In mice lacking myogenin, there is a severe deficiency of skeletal muscle, but some residual muscle fibers are present in mutant mice at birth. Mice lacking MRF4 are viable and have skeletal muscle, but they upregulate myogenin expression, which could potentially compensate for the absence of MRF4. Previous studies in which Myf5 and MRF4 null mutations were combined suggested that these genes do not share overlapping myogenic functions in vivo. To determine whether the functions of MRF4 might overlap with those of myogenin or MyoD, we generated double mutant mice lacking MRF4 and either myogenin or MyoD. MRF4/myogenin double mutant mice contained a comparable number of residual muscle fibers to mice lacking myogenin alone and myoblasts from those double mutant mice formed differentiated multinucleated myotubes in vitro as efficiently as wild-type myoblasts, indicating that neither myogenin nor MRF4 is absolutely essential for myoblast differentiation. Whereas mice lacking either MRF4 or MyoD were viable and did not show defects in muscle development, MRF4/MyoD double mutants displayed a severe muscle deficiency similar to that in myogenin mutants. Myogenin was expressed in MRF4/MyoD double mutants, indicating that myogenin is insufficient to support normal myogenesis in vivo. These results reveal unanticipated compensatory roles for MRF4 and MyoD in the muscle differentiation pathway and suggest that a threshold level of myogenic bHLH factors is required to activate muscle structural genes, with this level normally being achieved by combinations of multiple myogenic bHLH factors.

scholarly journals Long non-coding RNA TUG1 promotes cell progression in hepatocellular carcinoma via regulating miR-216b-5p/DLX2 axis

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Qun Dai ◽  
Jingyi Deng ◽  
Jinrong Zhou ◽  
Zhuhong Wang ◽  
Xiao-feng Yuan ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Cancer Progression ◽  
Noncoding Rna ◽  
Critical Role ◽  
Luciferase Reporter ◽  
Migration And Invasion ◽  
Marked Rise ◽  
Hcc Cells

Abstract Background Accumulating evidence indicates that the long noncoding RNA taurine upregulated gene 1(TUG1) plays a critical role in cancer progression and metastasis. However, the overall biological role and clinical significance of TUG1 in hepatocellular carcinoma (HCC) remain largely unknown. Methods The expressions of TUG1, microRNA-216b-5p and distal-less homeobox 2 (DLX2) were detected by Quantitative real-time polymerase chain reaction (qRT-PCR). The target relationships were predicted by StarBase v.2.0 or TargetScan and confirmed by dual-luciferase reporter assay. The cell growth, apoptosis, migration and invasion were detected by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), Flow cytometry and Transwell assays, respectively. All protein expression levels were detected by western blot. Tumor xenografts were implemented to explore the role of TUG1 in vivo. Results We found that there was a marked rise in TUG1 expression in HCC tissues and cells, and knockdown of TUG1 repressed the growth and metastasis and promoted apoptosis of HCC cells. In particular, TUG1 could act as a ceRNA, effectively becoming a sink for miR-216b-5p to fortify the expression of DLX2. Additionally, repression of TUG1 impared the progression of HCC cells by inhibiting DLX2 expression via sponging miR-216b-5p in vitro. More importantly, TUG1 knockdown inhibited HCC tumor growth in vivo through upregulating miR-216b-5p via inactivation of the DLX2. Conclusion TUG1 interacting with miR-216b-5p contributed to proliferation, metastasis, tumorigenesis and retarded apoptosis by activation of DLX2 in HCC.

scholarly journals Function of Native OmtA In Vivo and Expression and Distribution of This Protein in Colonies of Aspergillus parasiticus

2002 ◽  
Vol 68 (11) ◽  
pp. 5718-5727 ◽  
Author(s):  
Li-Wei Lee ◽  
Ching-Hsun Chiou ◽  
John E. Linz
Keyword(s):  
Fusion Protein ◽  
Aspergillus Parasiticus ◽  
Polyclonal Antibodies ◽  
Critical Role ◽  
Immunohistochemical Analysis ◽  
Cell Types ◽  
Temporal Association ◽  
Thin Sections

ABSTRACT The activities of two enzymes, a 168-kDa protein and a 40-kDa protein, OmtA, purified from the filamentous fungus Aspergillus parasiticus were reported to convert the aflatoxin pathway intermediate sterigmatocystin to O-methylsterigmatocystin in vitro. Our initial goal was to determine if OmtA is necessary and sufficient to catalyze this reaction in vivo and if this reaction is necessary for aflatoxin synthesis. We generated A. parasiticus omtA-null mutant LW1432 and a maltose binding protein-OmtA fusion protein expressed in Escherichia coli. Enzyme activity analysis of OmtA fusion protein in vitro confirmed the reported catalytic function of OmtA. Feeding studies conducted with LW1432 demonstrated a critical role for OmtA, and the reaction catalyzed by this enzyme in aflatoxin synthesis in vivo. Because of a close regulatory link between aflatoxin synthesis and asexual sporulation (conidiation), we hypothesized a spatial and temporal association between OmtA expression and conidiospore development. We developed a novel time-dependent colony fractionation protocol to analyze the accumulation and distribution of OmtA in fungal colonies grown on a solid medium that supports both toxin synthesis and conidiation. OmtA-specific polyclonal antibodies were purified by affinity chromatography using an LW1432 protein extract. OmtA was not detected in 24-h-old colonies but was detected in 48-h-old colonies using Western blot analysis; the protein accumulated in all fractions of a 72-h-old colony, including cells (0 to 24 h) in which little conidiophore development was observed. OmtA in older fractions of the colony (24 to 72 h) was partly degraded. Fluorescence-based immunohistochemical analysis conducted on thin sections of paraffin-embedded fungal cells from time-fractionated fungal colonies demonstrated that OmtA is evenly distributed among different cell types and is not concentrated in conidiophores. These data suggest that OmtA is present in newly formed fungal tissue and then is proteolytically cleaved as cells in that section of the colony age.

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