Batten disease (juvenile-onset neuronal ceroid lipofuscinosis, JNCL), the most 
common neurodegenerative disorder of childhood, is caused by mutations in a 
recently identified gene ( CLN3 ) localized to chromosome 16p11.2-12.1. To 
elucidate the biosynthesis and localization of the CLN3 protein, we expressed 
CLN3 cDNA in COS-1 and HeLa cell lines. In vitro translation, 
immunoprecipitation and Western blotting analyses detected an approximately 43 
kDa polypeptide. Pulse-chase experiments indicated that the CLN3 protein is 
synthesized as an N -glycosylated single-chain polypeptide, which was not 
detected in growth medium. Confocal immunofluorescence microscopy revealed that 
the CLN3 protein is localized to the lysosomal compartment. These results 
provide evidence that Batten disease can be classified as a member of lysosomal 
diseases.