CFTR (cystic fibrosis transmembrane conductance regulator, ATP-binding cassette (sub-family C, member 7)) is a human gene that provides instructions for making a protein called the cystic fibrosis transmembrane conductance regulator. This protein functions as an ion channel across the cell membrane. Such channels are found in tissues that produce mucus, sweat, saliva, tears and digestive enzymes. Chloride, a component of salt, is transported through the channels in response to cellular signals. The transport of chloride helps control the movement of water (osmosis) in tissues and maintain the fluidity of mucus and other secretions. The CFTR protein also regulates the function of other channels, such as a type of channel that transports sodium across cell membranes. Normal functioning of these channels ensures that organs such as the lungs and pancreas function properly.
Additional recommended knowledge
The CFTR gene is located on the long (q) arm of chromosome 7 at position 31.2, from base pair 116,907,253 to base pair 117,095,955.
- Congenital bilateral absence of vas deferens: Males with congenital bilateral absence of the vas deferens most often have a mild mutation (a change that allows partial function of the gene) in one copy of the CFTR gene and a cystic fibrosis-causing mutation in the other copy of CFTR. As a result of these mutations, the movement of water and salt into and out of cells is disrupted. This disturbance leads to the production of a large amount of thick mucus that blocks the developing vas deferens (a tube that carries sperm from the testes) and causes it to degenerate, resulting in infertility.
- Cystic fibrosis: More than 1,000 mutations in the CFTR gene have been found but the majority of these have not been associated with cystic fibrosis. Most of these mutations either substitute one amino acid (a building block of proteins) for another amino acid in the CFTR protein or delete a small amount of DNA in the CFTR gene. The most common mutation, called ΔF508, is a deletion (Δ) of one amino acid at position 508 in the CFTR protein. This altered protein never reaches the cell membrane because it is degraded shortly after it is made. All disease-causing mutations in the CFTR gene prevent the channel from functioning properly, leading to a blockage of the movement of salt and water into and out of cells. As a result of this blockage, cells that line the passageways of the lungs, pancreas, and other organs produce abnormally thick, sticky mucus. This mucus obstructs the airways and glands, causing the characteristic signs and symptoms of cystic fibrosis.
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