The CLN3 gene is located on chromosome 16p11.2, where it encodes a highly hydrophobic, multi-spanning transmembrane protein, whose function is not completely known. This protein is expressed in astrocytes, capillary endothelium and neurons of gray matter of the brain in peripheral nerve, pancreatic islet cells and within the seminiferous tubules of the testis. Several potential functions for the CLN3 protein have been proposed, including endocytosis and intracellular protein trafficking, lysosomal homeostasis, mitochondrial function, autophagy and amino-acid transport.