- The promoter of a lysosomal membrane transporter gene, CTNS, binds Sp-1, shares sequences with the promoter of an adjacent gene, CARKL, and causes cystinosis if mutated in a critical region. Phornphutkul, C., Anikster, Y., Huizing, M., Braun, P., Brodie, C., Chou, J.Y., Gahl, W.A. Am. J. Hum. Genet. (2001)