The cystic fibrosis transmembrane conductance regulator (CFTR) gene codes for a protein also known as CFTR. The CFTR protein resides in the surface of epithelial cells which line the lungs, digestive system and sweat glands. The symptoms of CF are caused by the inability of the CFTR to release chloride leading to the production of thick, sticky mucus in specific organs.
Since its discovery in 1989, more than 1,000 mutations of this single gene that can cause CF have been identified. Often, these mutations either substitute one DNA base – the building material of DNA – for another or delete a small number of DNA bases. The most common mutation, present in about 70 percent of patients with CF, is called F508del. In this mutation, three base pairs of the CFTR gene are deleted leading to the loss of an amino acid called phenylalanine (abbreviated F) at position 508 of the CFTR protein.
In normal cells, the CFTR protein acts as a channel that transports chloride into and out of cells, and regulates the passage of salts. The CFTR can also transport other ions and chemicals such as bicarbonate.