MYH7
MYH7 encodes the beta-myosin heavy chain, the primary motor protein of the human heart and slow-twitch skeletal muscle. Mutations in MYH7 are the most common cause of hypertrophic cardiomyopathy (HCM), driving the structural and mechanical changes that lead to heart failure.
Key Takeaways
- •MYH7 is the "engine" of the heart, converting chemical energy into physical beats.
- •It is the definitive gene for slow-twitch (Type I) muscle fibers.
- •Mutations in MYH7 cause Hypertrophic Cardiomyopathy (HCM), where the heart muscle becomes dangerously thick.
- •Novel cardiac myosin inhibitors (e.g., Mavacamten) work by slowing down the over-active MYH7 engine.
Basic Information
- Gene Symbol
- MYH7
- Full Name
- Myosin Heavy Chain 7
- Also Known As
- CMD1SCMH1MPD1MYHCBSPRD1
- Location
- 14q11.2
- Protein Type
- Motor Protein (Myosin Heavy Chain)
- Protein Family
- Myosin family
Related Isoforms
The predominant isoform in the adult human ventricle and slow-twitch skeletal muscle.
Key SNPs
The "founder" mutation for HCM; located in the actin-binding head, it significantly alters the motor kinetics and is associated with a high risk of heart failure.
A well-characterized pathogenic mutation in the converter domain of the myosin head; drives severe cardiac hypertrophy and arrhythmias.
Common marker used in GWAS to identify the MYH7 locus and its association with variations in skeletal muscle fiber composition.
Overview
MYH7 (Myosin Heavy Chain 7) encodes the beta-myosin heavy chain (β-MyHC), the fundamental motor protein responsible for the contraction of the human ventricles and slow-twitch (Type I) skeletal muscle fibers. β-MyHC is an ATPase that converts the chemical energy of ATP into mechanical force, driving the "power stroke" that pulls actin filaments and shortens the muscle sarcomere. Because the heart must beat billions of times without failure, the structural and enzymatic integrity of MYH7 is a requirement for human life.
The significance of MYH7 in cardiology is unparalleled. It was the first gene identified as a cause of Hypertrophic Cardiomyopathy (HCM), a condition where the heart wall becomes thick and stiff. While most heart diseases are caused by "weak" engines, HCM is often a disease of "over-active" engines. Mutations in MYH7 frequently increase the force and duration of the power stroke, leading to a state of chronic mechanical stress that forces the heart to remodel and thicken, often resulting in sudden cardiac death in young athletes.
Conceptual Model
A simplified mental model for the pathway:
MYH7 turns the "potential" of ATP into the "reality" of a heartbeat.
Core Health Impacts
- • Cardiac Contraction: Generates the majority of the systolic force required to pump blood to the body
- • Sarcomere Assembly: Provides the structural backbone for the organization of the thick filament
- • Energy Metabolism: The primary consumer of ATP in the heart; activity levels dictate myocardial oxygen demand
- • Slow-Twitch Power: Defines the endurance and metabolic efficiency of skeletal muscle fibers
- • Skeletal Development: Essential for the maturation of the musculature during late fetal and neonatal life
Protein Domains
Myosin Head (S1)
The catalytic motor domain containing the ATP-binding pocket and the actin-interaction site.
Converter Domain
A flexible joint that amplifies the small structural changes in the head into the large "power stroke" movement.
Coiled-Coil Tail
A long alpha-helical region that allows myosin molecules to twist together and form the thick filament.
Upstream Regulators
Thyroid Hormone (T3) Activator
The master regulator of myosin isoforms; T3 promotes the transition from fetal to adult MYH7 levels.
Beta-Adrenergic Signaling Activator
Adrenaline surges increase the phosphorylation of myosin-associated proteins, boosting MYH7 force.
Mechanical Stress Activator
Increased heart load (hypertension) triggers the transcriptional upregulation of fetal-like MYH7 patterns.
Calcineurin / NFAT Activator
Calcium-dependent signaling pathway that drives the hypertrophic gene program involving MYH7.
GATA4 Activator
Transcription factor essential for the basal and stress-induced expression of the MYH7 gene in the heart.
Downstream Targets
Sarcomere Contraction Activates
The physical sliding of filaments that results in muscle shortening.
ATP Hydrolysis Activates
The chemical breakdown of fuel that powers the molecular motor.
Force Generation Activates
The production of tension required for ventricular ejection and skeletal movement.
Myocardial Remodeling Activates
Chronic over-activity of MYH7 mutants forces the heart muscle to grow larger (hypertrophy).
Myofibril Assembly Activates
Proper MYH7 protein is required for the stable construction of the muscle contractile machinery.
Role in Aging
MYH7 is the "odometer" of the human heart. Over a century of life, the MYH7 motors must remain functional and efficient. The age-related decline in cardiac power and the stiffening of the ventricles are directly linked to the accumulation of damage and changes in the regulation of the MYH7 protein.
Motor Efficiency Decay
Aging involves a natural decline in the ATPase speed of MYH7, leading to a slower and less powerful heartbeat.
Hypertrophic Drift
The cumulative effect of blood pressure on the MYH7 axis drives the "left ventricular hypertrophy" of aging.
Oxidative Modification
Lifelong ROS exposure can damage the MYH7 head, impairing its ability to bind actin and consume ATP efficiently.
Isoform Reversion
Failing hearts often revert to "fetal" MYH7 expression patterns, a maladaptive response that further reduces power.
Sarcopenia Link
In skeletal muscle, age-related loss of MYH7-positive fibers reduces endurance and metabolic health in the elderly.
Mitochondrial Synergy
The high energy demand of the MYH7 motor requires tight coupling with mitochondria, a link that breaks down with age.
Disorders & Diseases
Hypertrophic Cardiomyopathy (HCM)
The primary genetic heart disease. MYH7 mutations (40%) cause the heart to become thick and prone to lethal arrhythmias.
Dilated Cardiomyopathy
A subset of DCM cases are caused by MYH7 mutations that result in a "weak" motor rather than an over-active one.
Laing Distal Myopathy
Mutations in the tail region of MYH7 cause this skeletal muscle disorder, characterized by weakness in the hands and feet.
Left Ventricular Non-compaction
A structural heart defect present from birth that is frequently linked to variants in the MYH7 motor protein.
Myosin Storage Myopathy
Rare mutations prevent the proper assembly of the tail domain, causing myosin to clump and damage muscle fibers.
The Power Stroke Paradox
In many HCM cases, the "disease" is actually caused by the heart being *too strong*. The mutated MYH7 motors spend more time in the active state, burning too much ATP and pulling too hard. This over-activity is what eventually triggers the heart to grow thick and fail, proving that in cardiac biology, "more" is not always better.
Interventions
Supplements
Supports the mitochondrial energy production required to fuel the high ATP demand of the MYH7 motors.
An absolute requirement for the ATPase activity of myosin and the subsequent relaxation of the sarcomere.
Reported to support the myocardial membrane health and potentially dampen the inflammatory signals of hypertrophy.
Aide in fatty acid transport to provide the preferred fuel source for the MYH7-rich slow-twitch fibers.
Lifestyle
The single most important factor for MYH7 carriers; preventing hypertension stops the "over-load" that triggers hypertrophy.
Supports the endurance capacity of MYH7-positive fibers while avoiding the extreme stress of competitive sports in HCM.
Critical for individuals with HCM, as low blood volume can worsen the outflow obstruction caused by a thick MYH7-rich wall.
The repair and turnover of sarcomeric proteins like MYH7 occur primarily during deep sleep phases.
Medicines
A first-in-class cardiac myosin inhibitor; it "quiets" the over-active MYH7 engine to reduce heart thickness and improve symptoms.
The traditional standard of care; they reduce the heart rate and the force of contraction to shield the MYH7 motors from stress.
Prevent the systemic signaling (Angiotensin II) that upregulates the MYH7-mediated hypertrophic program.
Ensures the hormonal environment required for the healthy maintenance of adult MYH7 levels in the heart.
Lab Tests & Biomarkers
Genetic Screening
The first-line genetic test for families with hypertrophic cardiomyopathy. Covers all 40 coding exons.
Assesses MYH7 alongside MYBPC3 and TTN to identify the molecular cause of heart thickening or weakness.
Cardiac Imaging
The primary clinical measure of MYH7-driven remodeling. A septum thickness >15mm is a major sign of HCM.
Detects the fibrosis (scarring) that occurs when the MYH7-rich muscle is chronically over-worked.
Biomarkers
Measures heart wall stress; used to track the severity of the MYH7-driven "outflow obstruction" in HCM.
Monitored to detect the low-level cell death that often accompanies severe hypertrophic remodeling.
Hormonal Interactions
Thyroid Hormone (T3) Primary Regulator
Sets the baseline expression of MYH7; hypothyroidism causes a shift toward less efficient "fetal" myosin patterns.
Adrenaline (Epinephrine) Stress Driver
Signals through beta-receptors to maximize the force and speed of the MYH7-mediated power stroke.
Estrogen Protective
Inhibits the hypertrophic signaling pathways, explaining the later onset of MYH7-driven heart disease in women.
Growth Hormone / IGF-1 Anabolic Signal
Drives the growth of muscle fibers and the synthesis of new MYH7 proteins during repair and development.
Deep Dive
Network Diagrams
MYH7: The Cardiac Piston
The Molecular Piston: MYH7 and Contraction
To understand MYH7, one must view the heart as a high-precision engine and the muscle fiber as a cylinder. MYH7 is the piston.
The Motor Protein: MYH7 produces the beta-myosin heavy chain, the motor protein that does the actual work of pumping. It uses the chemical energy of ATP to perform a mechanical “power stroke.” The myosin head reaches out, grabs the actin track, and pulls. This shortening of billions of molecular units simultaneously is what causes your heart to beat.
Endurance Specialist: MYH7 is the motor used for endurance. It is slower and more efficient than the “sprint” myosins found in fast-twitch muscle. This makes it perfect for the heart, which must beat 100,000 times a day without ever stopping for rest.
Hypertrophic Cardiomyopathy: The Over-Active Engine
The most significant clinical fact about MYH7 is its role in Hypertrophic Cardiomyopathy (HCM).
The “Super-Power” Mutation: In many cases of HCM, a single mutation in the MYH7 head (like Arg403Gln) makes the motor too good at its job.
- The Over-contraction: The mutated motors spend more time pulling and less time resting. They generate massive amounts of force and consume too much energy.
- The Remodeling: The heart muscle, feeling this constant “over-work,” tries to adapt by growing thicker and thicker. Eventually, the heart wall becomes so thick that it blocks the flow of blood and disrupts the electrical signals, leading to sudden cardiac arrest.
Mavacamten: Slowing Down to Save the Heart
The discovery that HCM is a disease of “over-active” MYH7 led to a revolutionary new treatment. For decades, we could only treat the symptoms of HCM.
The Myosin Brake: Researchers developed Mavacamten, a drug that acts as a precision brake for the MYH7 motor.
- Restoring Balance: Mavacamten tells the myosin heads to spend more time in their “resting” state. This reduces the excessive pulling force and lowers the energy demand of the heart.
- Reversing Disease: In clinical trials, this drug didn’t just stop the disease—it actually allowed the thick heart walls to start shrinking back to normal size. This proved that by targeting the motor itself, we can fix the structural damage of genetic heart disease at its molecular root.
Practical Note: The Strong-Heart Paradox
HCM is not a "weakness" at first. In the early stages, a person with an MYH7 mutation often has superior athletic performance because their heart is genetically "over-tuned." This is why HCM is the leading cause of sudden death in young athletes—the heart is so powerful that it ignores the body's safety signals until the electrical rhythm finally breaks.
Screening saves lives. If a family member has HCM, every relative must be screened for MYH7 variants. Because the thickening can be "silent" for years, a genetic test is the only definitive way to know if an individual is at risk before they start high-intensity training.
Relevant Research Papers
Links go to PubMed (abstracts are public); some papers also offer free full text via PMC or the publisher.
The foundational study that first identified MYH7 as the genetic cause of HCM, starting the field of cardiac molecular genetics.
Elucidated the atomic-level mechanics of the power stroke and the essential role of MYH7 in force generation.
The EXPLORER-HCM trial results proving that a targeted MYH7 inhibitor can reverse the pathophysiology of genetic heart disease.
Characterized the age-related shifts in MYH7 expression and their contribution to the reduced diastolic filling of old age.
Provided the first high-resolution insights into the conformational changes that allow MYH7 to convert ATP into force.