TPP1 and lysosomal storage disease: For example, we are unable to treat late infantile neuronal ceroid lipofuscinosis (LINCL), a lysosomal storage disorder in which a mutation in CLN2 (11p15) causes neurons to fail to produce enzymatically viable tripeptidylpeptidase 1 (TPP1) and store the subunit c of mitochondrial ATP synthase.