Another homologous cytosine insertion mutation at position 307 in exon 4 is responsible for the generation of a naturally occurring Cln6nclf mouse model [8,9] that recapitulates the human CLN6 disease phenotype and exhibits progressive retinal degeneration, the loss of motor coordination and balance, and memory and learning deficits [20]. Here, CLN6 is linked to retinal degeneration.