CTSD and Cognitive impairment: Importantly, in vivo studies with Clcn6-/- mice recapitulate some of the histological and clinical features of late-onset NCL, characterized by the accumulation of storage material (saposinB, lamp-1, cathepsin D and lysosomal acid phosphatase) in the lysosomal system, leading to mild cognitive impairment and behavioral abnormalities46.