PPT-1 deficient fibroblasts from patients suffering from infantile neuronal ceroid lipofuscinosis (INCL) or murine cells harboring a disrupted Ppt1/Cln1 gene revealed reduced caspase activation, Bid-cleavage, and cytochrome C release by mitochondrial outer membrane permeabilization (MOMP). Here, CYCS is linked to infantile neuronal ceroid lipofuscinosis.