By 2015, 13 genes (CLN1/PPT1, CLN2/TPP1, CLN3, CLN4/DNAJC5, CLN5, CLN6, CLN7/MFSD8, CLN8, CLN10/CTSD, CLN11/GRN, CLN12/ATP13A2, CLN13/CTSF, and CLN14/KCTD7) have been identified as being associated with NCL. The gene discussed is TPP1; the disease is neuronal ceroid lipofuscinosis.