The Ctns gene encodes a seven-transmembrane domain-containing protein that functions to transport cystine out of lysosomes, and it has been reported that nephropathic cystinosis is caused by CTNS gene mutations in humans (Attard et al. 1999; Kalatzis et al. 2004; Town et al. 1998). The gene discussed is CTNS; the disease is cystinosis.