Cystic Fibrosis is caused by a mutated gene that encodes the cystic fibrosis transmembrane conductance regulator (CFTR). This gene is passed from the parent to the child. A copy of the mutated gene must be inherited from each parent in order to have the disease. The picture to the left shows the possible outcomes for two carrier parents. There is a 25% chance of having an unaffected child, 50% of having a child that is a carrier, and 25% of having a child with cystic fibrosis. The carriers do not have the symptoms of cystic fibrosis. This is because they still did receive one non-mutated gene. The only child that will show symptoms is represented by the red child who received to r's.
The CFTR gene provides instructions for making a protein called the cystic fibrosis transmembrane conductance regulator. The picture on the left is what the protein looks like when folded and placed in the cell's membrane. This protein functions as a channel across the membrane of cells that produce mucus, sweat, saliva, tears, and digestive enzymes. The main job of this channel is to transport chloride ions (Cl-). There is another closely related channel called the ENaC that transports sodium (Na+). These two particles help control the movement of water in these cells, which is necessary for the production of thin, freely flowing mucus.
Disease-causing mutations in the CFTR gene alter the production, structure, or stability of the CFTR protein. Any change that prevents the channel from functioning properly impairs the transport of chloride ions in and out of the cell. This lack of transport then affects the movement of water. As a result, cells that line the passageways of the lungs, pancreas, and other organs, don't have the necessary amount of water to keep the mucus thin and flowing. The mucus gets thick and sticky, therefore unable to move. It then obstructs the airways or glands, leading to the characteristic signs and symptoms of cystic fibrosis.
Click on the link "CFTR Video" to see an animation of how the CFTR is made and how it works.
There are over 1,000 gene mutations that cause Cystic fibrosis. These mutations are then divided into six different classes. If you are interested in the different classes, click here.
No comments:
Post a Comment