CLC-3 deficiency leads to phenotypes similar to human neuronal ceroid lipofuscinosis

Background: CLC-3 is a member of the CLC chloride channel family and is widely expressed in mammalian tissues. To determine the physiological role of CLC-3, we generated CLC-3-deficient mice (Clcn3(-/-)) by targeted gene disrupt-ion. Results: Together with developmental retardation and higher mortality, the Clcn3(-/-) mice showed neurological manifestations such as blindness, motor coordination deficit, and spontaneous hyperlocomotion. In histological analysis, the Clcn3(-/-) mice showed a pattern of progressive degeneration of the retina, hippocampus and ileal mucosa, which resembled the phenotype observed in cathepsin D knockout mice. The defect of cathepsin D results in a lysosomal accumulation of ceroid lipofuscin containing the mitochondrial F1F0 ATPase subunit c. In immunohistochemistry and Western blot analysis, we found that the subunit c was heavily accumulated in the lysosome of Clcn3(-/-) mice. Furthermore, we detected an elevation in the endosomal pH of the Clcn3(-/-) mice. Conclusions: These results indicated that the neurodegeneration observed in the Clcn3(-/-) mice was caused by an abnormality in the machinery which degrades the cellular protein and was associated with the phenotype of neuronal ceroid lipofuscinosis (NCL). The elevated endosomal pH could be an important factor in the pathogenesis of NCL.