The job of the CTNS gene is to make cystinosin. Cystinosin transports, or carries, the amino acid cystine out of the lysosomesLysosomes are the organelles within the cells in your body that act as cell digestive system. Lysosomes break apart amino acids such as cystine.
In those with cystinosis, the cystinosin transport process does not work correctly. As a result, cystine builds up inside lysosomes. Over time, the cystine forms into crystals.
Cystine crystals may build up in cells in every organ of your body, including your eyes. The corneathe front layer of the eye is the part of the eye that may be affected the most.
In the cornea, the cystine crystals are usually pointed and needle-shaped and look like shards of glass.