Juvenile neuronal ceroid lipofuscinosis (JNCL) is an inherited neurodegenerative disease caused by mutations in the gene encoding CLN3 lysosomal protein. Contrary to late-infantile neuronal ceroid lipofuscinosis (LINCL), caused by mutations in the lysosomal protein tripeptidyl peptidase 1 (TPP1), no animal models or effective treatment exist for JNCL. Previous research characterized mouse models with either mutated Tpp1 or Cln3, but the phenotype of a double Cln3/Tpp1 mutant, as well as the function of CLN3 protein, remain unclear.