[5] Mutations in CTNS are responsible for cystinosis, an autosomal recessive lysosomal storage disease.

[8] An international collaborative effort finally succeeded in isolating CTNS by positional cloning in 1998.

[11] Cystinosin has seven N-glycosylation sites in the N-terminus region, spanning a range of 128 amino acid residues.

[14] Cystinosin functions as a symporter which actively transports protons and cystine, the oxidized cysteine dimer, out of the lysosome.

[16] Variation in the encoded cystinosin protein results in an inhibition or loss in its ability to transport cystine out of the lysosome.

[21] For example, mild cystinosis is typically associated with mutations that do not affect the amino acids in the transmembrane domains of cystinosin.

[7] In contrast, infantile nephropathic cystinosis, the most severe form of the disease, is most commonly associated with a total loss of activity.

[24][12] Human models for cystinosin are typically derived from cystinotic renal tubular cell lines.