Reviewed April 2015
What is the official name of the SCN5A gene?
The official name of this gene is “sodium channel, voltage gated, type V alpha subunit.”
SCN5A is the gene's official symbol. The SCN5A gene is also known by other names, listed below.
Read more about gene names and symbols on the About page.
What is the normal function of the SCN5A gene?
The SCN5A gene belongs to a family of genes that provide instructions for making sodium channels. These channels open and close at specific times to control the flow of positively charged sodium atoms (sodium ions) into cells. The sodium channels produced from the SCN5A gene are abundant in heart (cardiac) muscle and play key roles in these cells' ability to generate and transmit electrical signals. These channels play a major role in signaling the start of each heartbeat, coordinating the contractions of the upper and lower chambers of the heart, and maintaining a normal heart rhythm.
Does the SCN5A gene share characteristics with other genes?
The SCN5A gene belongs to a family of genes called SC (sodium channels).
A gene family is a group of genes that share important characteristics. Classifying individual genes into families helps researchers describe how genes are related to each other. For more information, see What are gene families? in the Handbook.
How are changes in the SCN5A gene related to health conditions?
Brugada syndrome - caused by mutations in the SCN5A gene
More than 300 mutations in the SCN5A gene have been identified in people with Brugada syndrome, which is a heart condition characterized by an irregular heart rhythm (arrhythmia). SCN5A gene mutations also cause sudden unexpected nocturnal death syndrome (SUNDS), which was originally described in Southeast Asian populations. Researchers have since determined that SUNDS and Brugada syndrome are the same disorder.
Some SCN5A gene mutations change single protein building blocks (amino acids) in the SCN5A protein. These mutations alter the structure of ion channels made with the SCN5A protein and disrupt the flow of sodium ions into cardiac muscle cells. Other mutations prevent the SCN5A gene from producing any functional ion channels, which also reduces the inward flow of sodium ions. A disruption in ion transport changes the way the heart beats, leading to the arrhythmia often found in Brugada syndrome and SUNDS.
progressive familial heart block - caused by mutations in the SCN5A gene
A few mutations in the SCN5A gene have been found to cause progressive familial heart block. This condition alters the normal beating of the heart and can lead to fainting (syncope) or sudden cardiac arrest and death. The SCN5A gene mutations change single protein building blocks (amino acids) in the SCN5A protein. Channels made with this altered protein allow little or no sodium to enter the cell. Cardiac cells with these altered channels have difficulty producing and transmitting electrical signals that coordinate normal heartbeats. Interruption of this signaling causes heart block. Death of these impaired cardiac cells over time can lead to a buildup of scar tissue (fibrosis), worsening the heart block.
Romano-Ward syndrome - caused by mutations in the SCN5A gene
More than 200 mutations in the SCN5A gene are known to cause Romano-Ward syndrome, often called long QT syndrome. This condition causes the cardiac muscle to take longer than usual to recharge between beats, which can lead to arrhythmia.
The SCN5A gene mutations that cause Romano-Ward syndrome include changes in single amino acids and deletions or insertions of a small number of amino acids in the SCN5A protein. Channels made with these altered SCN5A proteins stay open longer than usual, which allows sodium ions to continue flowing into cardiac muscle cells abnormally. This delay in channel closure alters the transmission of electrical signals in the heart, increasing the risk of an irregular heartbeat that can cause fainting (syncope) or sudden death.
sick sinus syndrome - caused by mutations in the SCN5A gene
At least 10 mutations in the SCN5A gene have been found to cause another heart condition called sick sinus syndrome. This condition affects the function of the sino-atrial (SA) node, which is an area of specialized cells in the heart that functions as a natural pacemaker. The SCN5A gene mutations that cause sick sinus syndrome lead to the production of nonfunctional sodium channels or abnormal channels that cannot transport ions properly. The flow of these ions is essential for creating the electrical impulses that start each heartbeat and spread these signals to other areas of the heart. Mutations reduce the flow of sodium ions, which alters the SA node's ability to create and spread electrical signals. These changes increase the risk of abnormally fast or slow heartbeats, which can cause dizziness, light-headedness, syncope, and related symptoms.
- other disorders - associated with the SCN5A gene
Variations in the SCN5A gene are associated with several other heart conditions. These include potentially life-threatening forms of arrhythmia called atrial fibrillation and ventricular fibrillation. The genetic variations associated with these conditions alter the flow of sodium ions through the channel, which can lead to abnormal heart rhythms and affect the heart's ability to pump blood.
SCN5A gene mutations have also been identified in some cases of sudden infant death syndrome (SIDS). SIDS is a major cause of death in babies younger than 1 year. It is characterized by sudden and unexplained death, usually during sleep. Researchers are working to determine how changes in the SCN5A gene could contribute to SIDS. Other genetic and environmental factors, many of which have not been identified, also play a part in determining the risk of this disorder.
Certain drugs, including medications used to treat arrhythmias, infections, seizures, and psychotic disorders, can lead to an abnormal heart rhythm in some people. This drug-induced heart condition, which is known as acquired long QT syndrome, increases the risk of cardiac arrest and sudden death. A small percentage of cases of acquired long QT syndrome occur in people who have an underlying change in the SCN5A gene.
Genetics Home Reference provides information about familial dilated cardiomyopathy, which is also associated with changes in the SCN5A gene.
Where is the SCN5A gene located?
Cytogenetic Location: 3p21
Molecular Location on chromosome 3: base pairs 38,548,058 to 38,649,673
The SCN5A gene is located on the short (p) arm of chromosome 3 at position 21.
More precisely, the SCN5A gene is located from base pair 38,548,058 to base pair 38,649,673 on chromosome 3.
See How do geneticists indicate the location of a gene? in the Handbook.
Where can I find additional information about SCN5A?
You and your healthcare professional may find the following resources about SCN5A helpful.
You may also be interested in these resources, which are designed for genetics professionals and researchers.
What other names do people use for the SCN5A gene or gene products?
- Sodium channel protein, cardiac muscle alpha-subunit
- sodium channel, voltage-gated, type V, alpha (long QT syndrome 3)
- sodium channel, voltage-gated, type V, alpha subunit
Where can I find general information about genes?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding SCN5A?
The resources on this site should not be used as a substitute for
professional medical care or advice. Users seeking information about
a personal genetic disease, syndrome, or condition should consult with a qualified
See How can I find a genetics professional in my area? in the Handbook.