GO:0030016 myofibril: Components, Assembly and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0030016 myofibril is the contractile element of skeletal and cardiac muscle, defined as a long, highly organized bundle of actin, myosin, and other proteins that contracts by a sliding filament mechanism.
• Myofibril assembly is a stepwise process involving actin and myosin filament formation, Z-disc assembly, and sarcomere organization, regulated by mechanical feedback and the ubiquitin-proteasome system.
• Myofibril morphogenesis is coordinated with mitochondria transport and morphogenesis through mechanical feedback mechanisms.
• Key proteins include actin, myosin, titin, myosin-binding protein C, and HDAC6, which modulate myofibril stiffness and relaxation kinetics.
• Dysregulation of myofibril components is linked to cardiac diseases such as hypertrophic cardiomyopathy and diastolic dysfunction.
• CRISPR-based models (knockout, point mutation, knock-in, overexpression) enable functional dissection of myofibril-related genes in skeletal and cardiac muscle research.
Description
The myofibril (GO:0030016) is the fundamental contractile apparatus of skeletal and cardiac muscle, defined as a long, highly organized bundle of actin, myosin, and other proteins that contracts by a sliding filament mechanism. This cellular component is essential for muscle contraction, force generation, and mechanical signaling. Myofibrils are composed of repeating sarcomeres, the basic contractile units, and their precise assembly and organization are critical for normal muscle function. Research into myofibril biology has revealed that myofibril assembly is not a static process but is dynamically regulated by mechanical forces, molecular chaperones, and proteolytic systems. The myofibril is also a hub for signaling events that coordinate mitochondrial distribution and energy production, ensuring that the high metabolic demands of muscle contraction are met. Understanding myofibril structure, assembly, and regulation is therefore central to muscle physiology and to the pathophysiology of cardiac and skeletal muscle diseases.
myofibril At A Glance
| GO ID | GO:0030016 |
|---|---|
| GO term | myofibril |
| Ontology | cellular_component |
| Synonym | none |
| Major function | Contractile element of skeletal and cardiac muscle; contracts by a sliding filament mechanism |
| Composition | Actin, myosin, and other proteins organized into sarcomeres |
| Location | Cytoplasm of muscle cells (skeletal and cardiac) |
| Associated processes | Muscle contraction, myofibril assembly, sarcomere organization, mechanotransduction |
What Is GO:0030016?
The myofibril is the contractile element of skeletal and cardiac muscle; it is a long, highly organized bundle of actin, myosin, and other proteins that contracts by a sliding filament mechanism. This definition, based on the Gene Ontology cellular component term GO:0030016, captures the structural and functional essence of the myofibril as the machinery responsible for muscle contraction.
Why Is myofibril Important in Cell Biology?
The myofibril is the ultimate effector of muscle contraction, converting chemical energy into mechanical force. Its precise assembly and regulation are essential for normal cardiac and skeletal muscle function, and defects in myofibril components or assembly lead to severe human diseases, including cardiomyopathies and muscle weakness. Moreover, myofibril morphogenesis is tightly coordinated with mitochondrial dynamics to meet energy demands, highlighting its integrative role in muscle cell biology.
• Myofibrils are the contractile units of skeletal and cardiac muscle, enabling voluntary and involuntary movement.
• Proper myofibril assembly is critical for heart development and function; defects cause congenital heart disease and cardiomyopathies.
• Myofibril stiffness and relaxation kinetics are modulated by proteins such as myosin-binding protein C and HDAC6, affecting diastolic function.
• The ubiquitin-proteasome system regulates myofibril assembly and turnover, linking protein quality control to muscle health.
• Mechanical feedback between myofibrils and mitochondria ensures energy supply matches contraction demand.
• Myofibril disorganization is a hallmark of muscle atrophy and dystrophies.
• Studying myofibril biology informs regenerative medicine and tissue engineering for muscle repair.
• Myofibril components are targets for therapeutic intervention in heart failure and arrhythmias.
• CRISPR screens can identify novel regulators of myofibril assembly and function.
• Myofibril research benefits from advanced imaging and proteomics to dissect sarcomere dynamics.
What Happens During myofibril?
Myofibril Assembly and Sarcomere Organization
In simple terms: Muscle cells build long protein cables called myofibrils by putting together repeating units called sarcomeres.
Myofibril assembly is a highly ordered process that begins with the formation of premyofibrils, which mature into mature myofibrils through the addition of sarcomeric proteins. This process involves the coordinated assembly of actin thin filaments and myosin thick filaments, along with structural proteins such as titin and Z-disc proteins. The ubiquitin-proteasome system plays a crucial role in regulating the levels and turnover of these proteins during assembly. Mechanical forces generated by the contracting myofibril provide feedback that guides proper alignment and maturation.
Mechanical Feedback and Mitochondrial Coordination
In simple terms: The growing myofibril sends mechanical signals that help position mitochondria, the cell's power plants, to meet energy needs.
During muscle development, myofibril morphogenesis is coordinated with mitochondria transport and morphogenesis through a mechanical feedback mechanism. This ensures that mitochondria are strategically positioned near myofibrils to supply ATP for contraction. Disruption of this coordination leads to energy deficits and muscle dysfunction. The mechanical coupling between myofibrils and mitochondria involves cytoskeletal elements such as microtubules.
Regulation of Myofibril Relaxation Kinetics
In simple terms: After contraction, myofibrils must relax quickly; certain proteins control how fast this happens.
Myosin-binding protein C (MyBP-C) is a key regulator of cardiac myofibril relaxation kinetics. Studies using gene-edited models have shown that MyBP-C slows relaxation, and its phosphorylation modulates this effect. HDAC6, a tubulin deacetylase, also influences myofibril stiffness and diastolic function, with implications for heart failure with preserved ejection fraction. These regulatory mechanisms are critical for proper cardiac filling and output.
Myofibril Turnover and Protein Quality Control
In simple terms: Old or damaged myofibril proteins are removed and replaced to keep muscle healthy.
The ubiquitin-proteasome system (UPS) mediates the degradation of myofibrillar proteins, allowing for turnover and replacement. This quality control is essential for maintaining myofibril integrity and function. Dysregulation of UPS components can lead to myofibril disorganization and muscle disease. Additionally, chaperones assist in the proper folding and assembly of myofibrillar proteins.
Key Genes Involved in GO:0030016 myofibril
The following genes encode key proteins that constitute or regulate the myofibril, and they are frequently studied in muscle biology and disease research.
| Gene | Major Role | Research Relevance |
|---|---|---|
| ACTC1 | Actin thin filament component | Mutations cause hypertrophic and dilated cardiomyopathy |
| MYH7 | Myosin heavy chain, thick filament | Mutations linked to hypertrophic cardiomyopathy |
| MYBPC3 | Myosin-binding protein C, regulates relaxation | Mutations cause hypertrophic cardiomyopathy; target for relaxation studies |
| TTN | Titin, giant sarcomeric protein | Mutations associated with dilated cardiomyopathy and muscular dystrophy |
| TNNT2 | Troponin T, thin filament regulatory protein | Mutations cause familial hypertrophic cardiomyopathy |
| TNNI3 | Troponin I, inhibits actomyosin ATPase | Mutations linked to restrictive cardiomyopathy |
| TPM1 | Tropomyosin, thin filament regulation | Mutations associated with hypertrophic cardiomyopathy |
| MYL2 | Myosin regulatory light chain | Mutations cause hypertrophic cardiomyopathy |
| MYL3 | Myosin essential light chain | Mutations linked to hypertrophic cardiomyopathy |
| ACTN2 | Alpha-actinin-2, Z-disc component | Mutations cause cardiomyopathy and skeletal myopathy |
| DES | Desmin, intermediate filament | Mutations cause desmin-related myopathy |
| HDAC6 | Tubulin deacetylase, regulates myofibril stiffness | Modulates diastolic function; target for heart failure |
| MTOR | Kinase regulating protein synthesis | Controls muscle hypertrophy and myofibril growth |
| FBXO32 | Atrogin-1, E3 ubiquitin ligase | Mediates myofibril protein degradation in atrophy |
| TRIM63 | MuRF1, E3 ubiquitin ligase | Targets myofibrillar proteins for degradation |
| BAG3 | Co-chaperone, regulates protein quality control | Mutations cause myofibrillar myopathy |
| CRYAB | Alpha-B crystallin, chaperone | Mutations cause myofibrillar myopathy |
How Is myofibril Regulated?
Myofibril assembly and function are regulated at multiple levels. Mechanical feedback mechanisms coordinate myofibril morphogenesis with mitochondrial dynamics. The ubiquitin-proteasome system controls the turnover of myofibrillar proteins, influencing assembly and degradation. Signaling pathways such as mTOR regulate protein synthesis necessary for myofibril growth and hypertrophy. Additionally, post-translational modifications, including phosphorylation of myosin-binding protein C, modulate relaxation kinetics. HDAC6-mediated deacetylation of tubulin affects myofibril stiffness and diastolic function.
myofibril and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| MYBPC3 | Hypertrophic cardiomyopathy, diastolic dysfunction | Knock-in mouse with patient mutation; hiPSC-derived cardiomyocytes |
| MYH7 | Hypertrophic cardiomyopathy | Knockout or point-mutation in hiPSCs; zebrafish |
| HDAC6 | Heart failure with preserved ejection fraction | Overexpression and knockout mouse models |
| DES | Desmin-related myopathy | Knock-in mouse; patient-derived myoblasts |
| FBXO32 | Muscle atrophy | Knockout mouse; skeletal muscle cell lines |
Cardiomyopathies
Mutations in genes encoding myofibrillar proteins are a major cause of hypertrophic, dilated, and restrictive cardiomyopathies. For example, mutations in MYBPC3, MYH7, and TNNT2 lead to sarcomeric dysfunction and heart failure. Myosin-binding protein C mutations specifically alter relaxation kinetics, contributing to diastolic dysfunction. HDAC6 dysregulation has been implicated in heart failure with preserved ejection fraction.
Skeletal Myopathies and Muscular Dystrophies
Defects in myofibril assembly or structural proteins cause skeletal muscle diseases such as myofibrillar myopathies and muscular dystrophies. Mutations in DES, CRYAB, and BAG3 lead to myofibril disorganization and muscle weakness. The ubiquitin-proteasome system is also involved in muscle atrophy, where excessive degradation of myofibrillar proteins contributes to muscle wasting.
Metabolic and Mitochondrial Myopathies
Disruption of the coordination between myofibrils and mitochondria can lead to energy deficits and muscle dysfunction. Defects in mechanical feedback between these organelles are associated with mitochondrial myopathies and exercise intolerance.
From myofibril-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does a candidate gene regulate myofibril assembly? | Knockout in C2C12 myoblasts or hiPSC-derived cardiomyocytes |
| Does a specific mutation alter sarcomere function? | Point mutation knock-in in hiPSCs or mouse |
| How does a protein localize within the myofibril? | Tagged knock-in (e.g., GFP) in muscle cells |
| Does overexpression of a gene cause hypertrophy? | Overexpression in mouse heart or cultured myotubes |
| What genes are essential for myofibril formation? | CRISPR library screening in muscle differentiation models |
| How does mechanical feedback affect mitochondria? | Knockout of mechanosensing genes in Drosophila or zebrafish |
How to Study the myofibril Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Confocal microscopy | Sarcomere organization and myofibril morphology | Assessment of myofibril assembly in fixed cells |
| Super-resolution microscopy | Nanoscale structure of sarcomeres | Visualization of Z-disc and filament alignment |
| Mass spectrometry | Protein composition and modifications | Identification of myofibril-associated proteins |
| Traction force microscopy | Contractile force | Functional assessment of engineered muscle |
| Calcium imaging | Calcium transients | Excitation-contraction coupling studies |
| CRISPR knockout | Gene function | Testing essentiality of myofibril genes |
| CRISPR knock-in | Protein localization and dynamics | Tagging endogenous sarcomeric proteins |
| RNA-seq | Transcriptional changes | Profiling muscle differentiation and disease models |
Imaging Myofibril Structure
Advanced microscopy techniques, including confocal and super-resolution microscopy, allow visualization of sarcomere organization and myofibril assembly in fixed and live cells. Fluorescent tagging of sarcomeric proteins enables dynamic tracking of myofibril formation.
Proteomics and Interactomics
Mass spectrometry-based proteomics can identify myofibril-associated proteins and their post-translational modifications. Proximity labeling and co-immunoprecipitation reveal interactions within the sarcomere.
Functional Assays for Contractility
Traction force microscopy and atomic force microscopy measure the contractile force of myofibrils and single sarcomeres. Calcium transient measurements assess excitation-contraction coupling.
Genome Editing and Screening
CRISPR-Cas9 knockout, point mutation, and knock-in models enable causal testing of gene function in myofibril biology. Pooled CRISPR screens can identify novel regulators of myofibril assembly.
How CRISPR Can Be Used to Study GO:0030016 myofibril
Knockout
CRISPR knockout of myofibril-related genes in cell models (e.g., C2C12, hiPSCs) or animal models (mouse, zebrafish) allows researchers to determine whether a gene is essential for myofibril assembly, structure, and function. For example, knockout of MYBPC3 in hiPSC-derived cardiomyocytes recapitulates hypertrophic cardiomyopathy phenotypes.
Point Mutation
Introducing disease-associated point mutations (e.g., in MYH7 or TNNT2) using CRISPR base editing or homology-directed repair creates isogenic models to study the precise effects of mutations on sarcomere function and disease progression.
Knock-in
Knock-in of fluorescent tags (e.g., GFP, mCherry) into endogenous myofibril genes enables real-time visualization of protein localization and dynamics in living muscle cells. This approach is valuable for studying myofibril assembly and turnover.
Overexpression
CRISPR activation (CRISPRa) or transgenic overexpression of myofibril genes can model gain-of-function states, such as hypertrophy or altered relaxation kinetics. Overexpression of HDAC6, for instance, increases myofibril stiffness and impairs diastolic function.
How EDITGENE Supports myofibril Research
Researchers studying myofibril-related genes often need to determine whether a candidate gene is causally involved in myofibril assembly, function, or disease. EDITGENE provides a comprehensive suite of CRISPR-based services to accelerate this discovery process, from gene knockout to precise point mutations and knock-in models.
Contact EDITGENE today to design your custom CRISPR model for myofibril research.
Frequently Asked Questions About myofibril
What is the myofibril GO:0030016?
GO:0030016 myofibril is a Gene Ontology cellular component term defined as the contractile element of skeletal and cardiac muscle; a long, highly organized bundle of actin, myosin, and other proteins that contracts by a sliding filament mechanism.
What genes are involved in myofibril assembly?
Key genes include ACTC1, MYH7, MYBPC3, TTN, TNNT2, TNNI3, TPM1, MYL2, MYL3, ACTN2, DES, HDAC6, and FBXO32, among others.
How is myofibril structure organized?
Myofibrils are composed of repeating sarcomeres containing actin thin filaments, myosin thick filaments, and structural proteins like titin and Z-disc proteins.
What diseases are linked to myofibril dysfunction?
Myofibril dysfunction is linked to hypertrophic cardiomyopathy, dilated cardiomyopathy, restrictive cardiomyopathy, myofibrillar myopathies, and muscular dystrophies.
How can CRISPR be used to study myofibril genes?
CRISPR knockout, point mutation, knock-in, and overexpression models allow functional dissection of myofibril genes in cell and animal models.
What is the role of HDAC6 in myofibrils?
HDAC6 modulates myofibril stiffness and diastolic function of the heart; its dysregulation is implicated in heart failure with preserved ejection fraction.
How does myosin-binding protein C affect myofibril relaxation?
Myosin-binding protein C slows cardiac myofibril relaxation kinetics, and its phosphorylation modulates this effect.
What methods are used to study myofibril assembly?
Methods include confocal and super-resolution microscopy, proteomics, traction force microscopy, calcium imaging, and CRISPR screening.
What is the role of the ubiquitin-proteasome system in myofibrils?
The ubiquitin-proteasome system regulates myofibril assembly and turnover by degrading myofibrillar proteins, and its dysregulation contributes to muscle atrophy.
How are myofibrils coordinated with mitochondria?
Myofibril morphogenesis is coordinated with mitochondria transport and morphogenesis through a mechanical feedback mechanism, ensuring energy supply matches contraction demand.
Conclusion
The myofibril (GO:0030016) is the contractile engine of skeletal and cardiac muscle, and its precise assembly and regulation are fundamental to muscle physiology. Dysregulation of myofibril components underlies a spectrum of cardiac and skeletal muscle diseases, making it a critical area of biomedical research. Advances in CRISPR gene editing and imaging technologies continue to unravel the complex mechanisms of myofibril biology, offering new therapeutic targets. EDITGENE supports this research with comprehensive CRISPR services tailored to myofibril-related genes.
References
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- 8. Avellaneda J et al.. 2021. Myofibril and mitochondria morphogenesis are coordinated by a mechanical feedback mechanism in muscle.. Nat Commun 12(1):2091 PMID: 33828099
