Myogenin can substitute for Myf5 in promoting myogenesis but less efficiently

Development ◽  
1997 ◽  
Vol 124 (13) ◽  
pp. 2507-2513 ◽  
Author(s):  
Y. Wang ◽  
R. Jaenisch
Keyword(s):  
Muscle Development ◽  
Mutant Mice ◽  
Regulatory Sequences ◽  
Functional Protein ◽  
Helix Loop Helix ◽  
Myogenic Lineage ◽  
Muscle Formation ◽  
Myogenic Factor ◽  
Temporal And Spatial

The myogenic basic Helix-Loop-Helix transcription factors, including Myf5, MyoD, myogenin (myg) and MRF4, play important roles in skeletal muscle development. The phenotypes of mutant mice deficient in either gene are different, suggesting that each gene may have a unique function in vivo. We previously showed that targeting myogenin into the Myf5 locus (Myf5(myg-ki)) rescued the rib cage truncation in the Myf5-null mutant, hence demonstrating functional redundancy between Myf5 and myogenin in skeletal morphogenesis. Here we present the results of crossing myogenin knock-in (myg-ki) mice with either MyoD-null or myogenin-null mutants. The Myf5(myg-ki) allele rescued early myogenesis, but Myf5(myg-ki/myg-ki);MyoD(−/−) mutant mice died immediately after birth owing to reduced muscle formation. Therefore, myogenin, expressed from the Myf5 locus, is not able to completely replace the function of Myf5 in muscle development although it is capable of determining and/or maintaining myogenic lineage. Myf5(myg-ki/myg-ki);myg(−/−) mutant mice displayed the same phenotype as myg(−/−) mutants. This indicates that the earlier expression of myogenin cannot promote myogenic terminal differentiation, which is normally initiated by the endogenous myogenin. Thus, our results are consistent with the notion that Myf5 and myogenin are functionally interchangeable in determining myogenic lineage and assuring normal rib formation. Our experiment revealed, however, that some aspects of myogenesis may be unique to a given myogenic factor and are due to either different regulatory sequences that control their temporal and spatial expression or different functional protein domains.

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 Accelerated Response of the myogenin Gene to Denervation in Mutant Mice Lacking Phosphorylation of Myogenin at Threonine 87

2004 ◽  
Vol 24 (5) ◽  
pp. 1983-1989 ◽  
Author(s):  
Chris S. Blagden ◽  
Larry Fromm ◽  
Steven J. Burden
Keyword(s):  
Gene Expression ◽  
Skeletal Muscle ◽  
Electrical Activity ◽  
Muscle Development ◽  
Mutant Mice ◽  
Threonine Residue ◽  
E Boxes ◽  
Bhlh Proteins

ABSTRACT Gene expression in skeletal muscle is regulated by a family of myogenic basic helix-loop-helix (bHLH) proteins. The binding of these bHLH proteins, notably MyoD and myogenin, to E-boxes in their own regulatory regions is blocked by protein kinase C (PKC)-mediated phosphorylation of a single threonine residue in their basic region. Because electrical stimulation increases PKC activity in skeletal muscle, these data have led to an attractive model suggesting that electrical activity suppresses gene expression by stimulating phosphorylation of this critical threonine residue in myogenic bHLH proteins. We show that electrical activity stimulates phosphorylation of myogenin at threonine 87 (T87) in vivo and that calmodulin-dependent kinase II (CaMKII), as well as PKC, catalyzes this reaction in vitro. We find that phosphorylation of myogenin at T87 is dispensable for skeletal muscle development. We show, however, that the decrease in myogenin (myg) expression following innervation is delayed and that the increase in expression following denervation is accelerated in mutant mice lacking phosphorylation of myogenin at T87. These data indicate that two distinct innervation-dependent mechanisms restrain myogenin activity: an inactivation mechanism mediated by phosphorylation of myogenin at T87, and a second, novel regulatory mechanism that regulates myg gene activity independently of T87 phosphorylation.

Differential regulation of epaxial and hypaxial muscle development by paraxis

Development ◽  
1999 ◽  
Vol 126 (23) ◽  
pp. 5217-5229 ◽  
Author(s):  
J. Wilson-Rawls ◽  
C.R. Hurt ◽  
S.M. Parsons ◽  
A. Rawls
Keyword(s):  
Progenitor Cell ◽  
Muscle Development ◽  
Trunk Muscles ◽  
Developmentally Regulated ◽  
Myogenic Lineage ◽  
Important Regulator ◽  
Myogenic Factor ◽  
Myogenic Progenitor Cells ◽  
Different Origins ◽  
Myod Expression

In vertebrates, skeletal muscle is derived from progenitor cell populations located in the epithelial dermomyotome compartment of the each somite. These cells become committed to the myogenic lineage upon delamination from the dorsomedial and dorsolateral lips of the dermomyotome and entry into the myotome or dispersal into the periphery. Paraxis is a developmentally regulated transcription factor that is required to direct and maintain the epithelial characteristic of the dermomyotome. Therefore, we hypothesized that Paraxis acts as an important regulator of early events in myogenesis. Expression of the muscle-specific myogenin-lacZ transgene was used to examine the formation of the myotome in the paraxis−/− background. Two distinct types of defects were observed that mirrored the different origins of myoblasts in the myotome. In the medial myotome, where the expression of the myogenic factor Myf5 is required for commitment of myoblasts, the migration pattern of committed myoblasts was altered in the absence of Paraxis. In contrast, in the lateral myotome and migratory somitic cells, which require the expression of MyoD, expression of the myogenin-lacZ transgene was delayed by several days. This delay correlated with an absence of MyoD expression in these regions, indicating that Paraxis is required for commitment of cells from the dorsolateral dermomyotome to the myogenic lineage. In paraxis−/−/myf5−/− neonates, dramatic losses were observed in the epaxial and hypaxial trunk muscles that are proximal to the vertebrae in the compound mutant, but not those at the ventral midline or the non-segmented muscles of the limb and tongue. In this genetic background, myoblasts derived from the medial (epaxial) myotome are not present to compensate for deficiencies of the lateral (hypaxial) myotome. Our data demonstrate that Paraxis is an important regulator of a subset of the myogenic progenitor cells from the dorsolateral dermomyotome that are fated to form the non-migratory hypaxial muscles.

The Mef2c gene is a direct transcriptional target of myogenic bHLH and MEF2 proteins during skeletal muscle development

Development ◽  
2001 ◽  
Vol 128 (22) ◽  
pp. 4623-4633 ◽  
Author(s):  
Da-Zhi Wang ◽  
M. Renee Valdez ◽  
John McAnally ◽  
James Richardson ◽  
Eric N. Olson
Keyword(s):  
Gene Expression ◽  
Skeletal Muscle ◽  
Transcription Factors ◽  
Binding Site ◽  
Control Region ◽  
Muscle Development ◽  
Regulatory Elements ◽  
Skeletal Muscle Development ◽  
Helix Loop Helix

Members of the MEF2 family of transcription factors are upregulated during skeletal muscle differentiation and cooperate with the MyoD family of myogenic basic helix-loop-helix (bHLH) transcription factors to control the expression of muscle-specific genes. To determine the mechanisms that regulate MEF2 gene expression during skeletal muscle development, we analyzed the mouse Mef2c gene for cis-regulatory elements that direct expression in the skeletal muscle lineage in vivo. We describe a skeletal muscle-specific control region for Mef2c that is sufficient to direct lacZ reporter gene expression in a pattern that recapitulates that of the endogenous Mef2c gene in skeletal muscle during pre- and postnatal development. This control region is a direct target for the binding of myogenic bHLH and MEF2 proteins. Mutagenesis of the Mef2c control region shows that a binding site for myogenic bHLH proteins is essential for expression at all stages of skeletal muscle development, whereas an adjacent MEF2 binding site is required for maintenance but not for initiation of Mef2c transcription. Our findings reveal the existence of a regulatory circuit between these two classes of transcription factors that induces, amplifies and maintains their expression during skeletal muscle development.

Differential activation of Myf5 and MyoD by different Wnts in explants of mouse paraxial mesoderm and the later activation of myogenesis in the absence of Myf5

Development ◽  
1998 ◽  
Vol 125 (21) ◽  
pp. 4155-4162 ◽  
Author(s):  
S. Tajbakhsh ◽  
U. Borello ◽  
E. Vivarelli ◽  
R. Kelly ◽  
J. Papkoff ◽  
...  
Keyword(s):  
Neural Tube ◽  
Muscle Development ◽  
Early Embryo ◽  
Paraxial Mesoderm ◽  
Dorsal Neural Tube ◽  
Muscle Formation ◽  
Correct Pattern ◽  
Dorsal Ectoderm ◽  
Dependent Pathway

Activation of myogenesis in newly formed somites is dependent upon signals derived from neighboring tissues, namely axial structures (neural tube and notochord) and dorsal ectoderm. In explants of paraxial mesoderm from mouse embryos, axial structures preferentially activate myogenesis through a Myf5-dependent pathway and dorsal ectoderm preferentially through a MyoD-dependent pathway. Here we report that cells expressing Wnt1 will preferentially activate Myf5 while cells expressing Wnt7a will preferentially activate MyoD. Wnt1 is expressed in the dorsal neural tube and Wnt7a in dorsal ectoderm in the early embryo, therefore both can potentially act in vivo to activate Myf5 and MyoD, respectively. Wnt4, Wnt5a and Wnt6 exert an intermediate effect activating both Myf5 and MyoD equivalently in paraxial mesoderm. Sonic Hedgehog synergises with both Wnt1 and Wnt7a in explants from E8.5 paraxial mesoderm but not in explants from E9.5 embryos. Signaling through different myogenic pathways may explain the rescue of muscle formation in Myf5 null embryos, which do not form an early myotome but later develop both epaxial and hypaxial musculature. Explants of unsegmented paraxial mesoderm contain myogenic precursors capable of expressing MyoD in response to signaling from a neural tube isolated from E10.5 embryos, the developmental stage when MyoD is present throughout the embryo. Myogenic cells cannot activate MyoD in response to signaling from a less mature neural tube. Together these data suggest that different Wnt molecules can activate myogenesis through different pathways such that commitment of myogenic precursors is precisely regulated in space and time to achieve the correct pattern of skeletal muscle development.

scholarly journals The Cell Adhesion Molecule M-Cadherin Is Not Essential for Muscle Development and Regeneration

2002 ◽  
Vol 22 (13) ◽  
pp. 4760-4770 ◽  
Author(s):  
Angela Hollnagel ◽  
Christine Grund ◽  
Werner W. Franke ◽  
Hans-Henning Arnold
Keyword(s):  
Cell Adhesion ◽  
Adhesion Molecule ◽  
Satellite Cells ◽  
Cell Adhesion Molecule ◽  
Muscle Development ◽  
Mutant Mice ◽  
Wild Type ◽  
Essentially Normal

ABSTRACT M-cadherin is a classical calcium-dependent cell adhesion molecule that is highly expressed in developing skeletal muscle, satellite cells, and cerebellum. Based on its expression pattern and observations in cell culture, it has been postulated that M-cadherin may be important for the fusion of myoblasts to form myotubes, the correct localization and function of satellite cells during muscle regeneration, and the specialized architecture of adhering junctions in granule cells of cerebellar glomeruli. In order to investigate the potential roles of M-cadherin in vivo, we generated a null mutation in mice. Mutant mice were viable and fertile and showed no gross developmental defects. In particular, the skeletal musculature appeared essentially normal. Moreover, muscle lesions induced by necrosis were efficiently repaired in mutant mice, suggesting that satellite cells are present, can be activated, and are able to form new myofibers. This was also confirmed by normal growth and fusion potential of mutant satellite cells cultured in vitro. In the cerebellum of M-cadherin-lacking mutants, typical contactus adherens junctions were present and similar in size and numbers to the equivalent junctions in wild-type animals. However, the adhesion plaques in the cerebellum of these mutants appeared to contain elevated levels of N-cadherin compared to wild-type animals. Taken together, these observations suggest that M-cadherin in the mouse serves no absolutely required function during muscle development and regeneration and is not essential for the formation of specialized cell contacts in the cerebellum. It seems that N-cadherin or other cadherins can largely compensate for the lack of M-cadherin.

scholarly journals Regulation of Skeletal Muscle Sarcomere Integrity and Postnatal Muscle Function by Mef2c

2007 ◽  
Vol 27 (23) ◽  
pp. 8143-8151 ◽  
Author(s):  
Matthew J. Potthoff ◽  
Michael A. Arnold ◽  
John McAnally ◽  
James A. Richardson ◽  
Rhonda Bassel-Duby ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Transcription Factors ◽  
Muscle Development ◽  
Skeletal Muscle Development ◽  
Postnatal Maturation ◽  
Helix Loop Helix ◽  
Specific Proteins ◽  
Perinatal Lethality ◽  
Bhlh Transcription Factors

ABSTRACT Myocyte enhancer factor 2 (MEF2) transcription factors cooperate with the MyoD family of basic helix-loop-helix (bHLH) transcription factors to drive skeletal muscle development during embryogenesis, but little is known about the potential functions of MEF2 factors in postnatal skeletal muscle. Here we show that skeletal muscle-specific deletion of Mef2c in mice results in disorganized myofibers and perinatal lethality. In contrast, neither Mef2a nor Mef2d is required for normal skeletal muscle development in vivo. Skeletal muscle deficient in Mef2c differentiates and forms normal myofibers during embryogenesis, but myofibers rapidly deteriorate after birth due to disorganized sarcomeres and a loss of integrity of the M line. Microarray analysis of Mef2c null muscles identified several muscle structural genes that depend on MEF2C, including those encoding the M-line-specific proteins myomesin and M protein. We show that MEF2C directly regulates myomesin gene transcription and that loss of Mef2c in skeletal muscle results in improper sarcomere organization. These results reveal a key role for Mef2c in maintenance of sarcomere integrity and postnatal maturation of skeletal muscle.

scholarly journals In vivo interactome profiling by enzyme‐catalyzed proximity labeling

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yangfan Xu ◽  
Xianqun Fan ◽  
Yang Hu
Keyword(s):  
State Of The Art ◽  
Catalytic Efficiency ◽  
Biological Processes ◽  
Protein Protein Interaction ◽  
Current State ◽  
Protein Interactome ◽  
Potential Applications ◽  
Protein Protein Interaction Networks ◽  
Temporal And Spatial

AbstractEnzyme-catalyzed proximity labeling (PL) combined with mass spectrometry (MS) has emerged as a revolutionary approach to reveal the protein-protein interaction networks, dissect complex biological processes, and characterize the subcellular proteome in a more physiological setting than before. The enzymatic tags are being upgraded to improve temporal and spatial resolution and obtain faster catalytic dynamics and higher catalytic efficiency. In vivo application of PL integrated with other state of the art techniques has recently been adapted in live animals and plants, allowing questions to be addressed that were previously inaccessible. It is timely to summarize the current state of PL-dependent interactome studies and their potential applications. We will focus on in vivo uses of newer versions of PL and highlight critical considerations for successful in vivo PL experiments that will provide novel insights into the protein interactome in the context of human diseases.

scholarly journals Ectopic Expression of Inhibitors of Protein Phosphatase Type 1 (PP1) Can Be Used to Analyze Roles of PP1 in Drosophila Development

Genetics ◽  
2003 ◽  
Vol 164 (1) ◽  
pp. 235-245
Author(s):  
Daimark Bennett ◽  
Balázs Szöőr ◽  
Sascha Gross ◽  
Natalia Vereshchagina ◽  
Luke Alphey
Keyword(s):  
Protein Phosphatase ◽  
Muscle Development ◽  
Ectopic Expression ◽  
High Specificity ◽  
Type I ◽  
Protein Phosphatase Type 1 ◽  
Mitotic Figures ◽  
Protein Phosphatase Type

Abstract We have identified two proteins that bind with high specificity to type 1 serine/threonine protein phosphatase (PP1) and have exploited their inhibitory properties to develop an efficient and flexible strategy for conditional inactivation of PP1 in vivo. We show that modest overexpression of Drosophila homologs of I-2 and NIPP1 (I-2Dm and NIPP1Dm) reduces the level of PP1 activity and phenotypically resembles known PP1 mutants. These phenotypes, which include lethality, abnormal mitotic figures, and defects in muscle development, are suppressed by coexpression of PP1, indicating that the effect is due specifically to loss of PP1 activity. Reactivation of I-2Dm:PP1c complexes suggests that inhibition of PP1 activity in vivo does not result in a compensating increase in synthesis of active PP1. PP1 mutants enhance the wing overgrowth phenotype caused by ectopic expression of the type II TGFβ superfamily signaling receptor Punt. Using I-2Dm, which has a less severe effect than NIPP1Dm, we show that lowering the level of PP1 activity specifically in cells overexpressing Punt is sufficient for wing overgrowth and that the interaction between PP1 and Punt requires the type I receptor Thick-veins (Tkv) but is not strongly sensitive to the level of the ligand, Decapentaplegic (Dpp), nor to that of the other type I receptors. This is consistent with a role for PP1 in antagonizing Punt by preventing phosphorylation of Tkv. These studies demonstrate that inhibitors of PP1 can be used in a tissue- and developmental-specific manner to examine the developmental roles of PP1.

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