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MYH6 gene

Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

MYH6 gene

The MYH6 gene encodes the cardiac alpha-myosin heavy chain, a protein essential for heart muscle contraction, with mutations linked to various heart rhythm and structural disorders.

Overview

The MYH6 gene provides instructions for making the cardiac alpha (α)-myosin heavy chain. This protein is found in heart muscle cells and is a key component of type II myosin. Type II myosin generates the mechanical force required for the heart to pump blood. It is a major component of sarcomeres, the basic units of muscle contraction, where it interacts with actin to allow muscle fibers to contract.

Health Conditions Related to Genetic Changes

Sick sinus syndrome

A specific variation of the MYH6 gene (Arg721Trp) has been associated with an increased risk of sick sinus syndrome. This condition affects the sino-atrial (SA) node, the heart's natural pacemaker. The variation is thought to alter the structure of the α-myosin heavy chain, disrupting cardiac muscle contraction and leading to an abnormally slow heartbeat (bradycardia) and symptoms such as dizziness and fainting (syncope).

Congenital heart defects

Mutations in the MYH6 gene are also linked to congenital heart defects, most notably atrial-septal defect (ASD), which is a hole in the wall separating the two upper chambers of the heart. These mutations often affect the head domain of the protein, which is responsible for binding to actin. Abnormal interaction between these proteins can disrupt early heart development.

Genomic Location

The MYH6 gene is found on chromosome 14.

Frequently Asked Questions

While many congenital heart defects are detected via prenatal ultrasound, MYH6-related defects like atrial-septal defects (ASD) may present with subtle signs in infancy or early childhood. These can include rapid breathing, fatigue during feeding, poor weight gain, or a heart murmur detected during a routine physical exam. Because ASDs can be asymptomatic for years, regular pediatric check-ups and echocardiograms are crucial for early detection if a family history of heart defects exists.
Management often focuses on preventing symptoms of bradycardia and syncope. Patients are generally advised to avoid activities that require rapid changes in posture, such as standing up quickly from a seated or lying position, to prevent dizziness. Staying well-hydrated and avoiding excessive alcohol consumption, which can further depress heart rate, is also recommended. In many cases, medication adjustments are necessary, as certain heart rate-lowering drugs may worsen the condition, and a pacemaker may be required if symptoms become severe.
The specific Arg721Trp variation in the MYH6 gene alters the structure of the cardiac alpha-myosin heavy chain. This structural change disrupts the normal mechanical contraction of the heart muscle, which can interfere with the function of the sino-atrial node, the heart's natural pacemaker. The result is an abnormally slow heartbeat known as bradycardia, which often manifests as dizziness or fainting spells due to insufficient blood flow to the brain.
MYH6-related conditions typically follow an autosomal dominant inheritance pattern, meaning only one copy of the altered gene is needed to increase the risk of heart rhythm or structural issues. If a parent has a pathogenic MYH6 variant, there is a 50 percent chance of passing it to each child. However, penetrance can be variable, meaning some family members may carry the gene without showing severe symptoms, which makes genetic counseling and family screening important for accurate risk assessment.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.