MFSD8 and neuronal ceroid lipofuscinosis 7: Although the genetic mutations in the MFSD8 gene resulting in CLN7 disease are well documented and the MFSD8 protein is a member of the major facilitator superfamily (MFS), the function, nature of metabolite(s) transported by MFSD8 protein (3), and therefore disease mechanisms of this progressive neurodegenerative disease are unknown.