Ankyrin-B syndrome is associated with a variety of heart problems related to disruption of the heart's normal rhythm (arrhythmia). Heart rhythm is controlled by electrical signals that move through the heart in a highly coordinated way. In ankyrin-B syndrome, disruption of different steps of electrical signaling can lead to arrhythmia, and the resulting heart problems vary among affected individuals.

Individuals with ankyrin-B syndrome may have problems with the sinoatrial (SA) node, which generates the electrical impulses that start each heartbeat. If the SA node is not functioning properly, the heartbeat can be too slow (bradycardia). In a small number of people with ankyrin-B syndrome, the heart takes longer than usual to recharge between beats, which is known as a prolonged QT interval (long QT). Some affected individuals have impaired progression (conduction) of electrical impulses between the chambers of the heart, which can cause a problem called heart block. Other heart problems that occur in ankyrin-B syndrome include irregular and uncoordinated electrical activity in the heart's upper chambers (atrial fibrillation) or lower chambers (ventricular fibrillation) and an abnormality called catecholaminergic polymorphic ventricular tachycardia (CPVT), in which an increase in the heart rate can trigger an abnormally fast and irregular heartbeat called ventricular tachycardia. In people with ankyrin-B syndrome, arrhythmia can lead to fainting (syncope) or cardiac arrest and sudden death.

When associated with a prolonged QT interval, the condition is sometimes classified as long QT syndrome 4. However, because additional heart problems can result from changes in the same gene, long QT syndrome 4 is usually considered part of ankyrin-B syndrome.

Ankyrin-B syndrome is caused by mutations in the ANK2 gene, which provides instructions for making a protein called ankyrin-B. This protein is active in many cell types, including heart (cardiac) muscle cells. The ankyrin-B protein inserts certain structures called ion channels into their proper locations in the cell membrane. Ion channels are complexes of proteins that transport charged atoms (ions) across cell membranes. In the heart, the flow of ions (such as sodium, potassium, and calcium) through ion channels generates the electrical signals that control the heartbeat and maintain a normal heart rhythm.

Mutations in the ANK2 gene lead to production of an altered ankyrin-B protein that cannot target ion channels to their correct locations in cardiac muscle cells. The loss of functional ion channels in the heart disrupts the normal flow of ions, which alters the heart's normal rhythm and causes the heart problems associated with ankyrin-B syndrome.

Not everyone with an ANK2 gene mutation has heart problems related to ankyrin-B syndrome. Researchers speculate that other genes or environmental factors may play a role in development of the condition.

Normal Function

The ANK2 gene provides instructions for making a protein called ankyrin-B. Ankyrin-B is part of a family of ankyrin proteins, which interact with many other types of proteins in cells throughout the body. Ankyrins help organize the cell's structural framework (the cytoskeleton) and link certain proteins that span the cell membrane to this framework. Additionally, ankyrins play key roles in important functions including cell movement (migration) and cell growth and division (proliferation).

The ankyrin-B protein is active in many cell types, particularly in the brain and in heart (cardiac) muscle. This protein mainly interacts with ion channels and ion transporters, which are complexes of proteins that move charged atoms (ions) across cell membranes. In the heart, the flow of ions (such as sodium, potassium, and calcium) through ion channels and ion transporters generates the electrical signals that control the heartbeat and maintain a normal heart rhythm. Ankyrin-B ensures these channels and transporters are in their proper locations in the cell membrane so they can regulate the flow of ions into and out of cardiac muscle cells. In addition, ankyrin-B helps ensure that signaling molecules that regulate the activity of ion channels and ion transporters are in the proper location.

Health Conditions Related to Genetic Changes

Ankyrin-B syndrome

At least ten mutations in the ANK2 gene have been found to cause ankyrin-B syndrome, a condition characterized by a variety of heart problems. Most often, mutations in the ANK2 gene lead to abnormalities of the heart's natural pacemaker (the sinoatrial node), a heart rate that is slower than normal (bradycardia), a disruption in the rhythm of the heart (arrhythmia), and an increased risk of fainting (syncope) and sudden death.

Each of the identified mutations in the ANK2 gene changes a single protein building block (amino acid) in the ankyrin-B protein. Most of these mutations alter a region of the ankyrin-B protein important for its function. At least one ANK2 gene mutation prevents ankyrin-B from getting to the cell membrane where it is needed to function. As a result of these genetic changes, the ankyrin-B protein cannot target ion channels and ion transporters to their correct locations in cardiac muscle cells. Although the channels and transporters are produced normally by the cell, they are unable to function if they are not inserted correctly into the cell membrane. This loss of functional channels and transporters in the heart disrupts the normal flow of ions, which alters the heart's normal rhythm and leads to the heart problems that can be a part of ankyrin-B syndrome.

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Other Names for This Gene

• ANK2_HUMAN
• ankyrin 2, neuronal
• ankyrin B
• ankyrin, brain
• ankyrin, nonerythroid
• ankyrin-2, nonerythrocytic
• brank-2
• LQT4

Genomic Location

Ankyrin-B syndrome is inherited in an autosomal dominant pattern, which means one copy of the altered ANK2 gene in each cell is sufficient to cause the disorder. In most cases, an affected person has one parent with the condition.

Some people who have an altered ANK2 gene never develop heart problems, a situation known as reduced penetrance.

Ankyrin-B syndrome is a rare disorder. Its prevalence is unknown.