Clcn7, encoding the chloride/proton-exchanger ClC-7, is crucial for multiple physiological processes. It functions in the biosynthesis of PI(3,5)P2 by its regulation related to the phosphatase FIG4 and the scaffold protein VAC14 [1]. In osteoclasts, it enables efficient proton transport into the resorption lacuna by providing a negative counter-ion [2]. In most cell types other than osteoclasts, ClC-7 is located in late endosomes and lysosomes, participating in intravesicular ion homeostasis [2].

In Fig4 null cell cultures, knockout of Clcn7 corrected lysosomal swelling and partially corrected lysosomal hyperacidification. In the Fig4 null mouse, reduction of ClC-7 by expressing the dominant-negative CLCN7 variant p.Gly215Arg improved growth, neurological function, and increased lifespan by 20% [1]. Also, in Clcn7 knockout mice, an osteopetrosis phenotype was observed, suggesting ClC-7's role in bone resorption as it might be responsible for transporting the negative charge required for efficient proton transport in osteoclasts [2].

In conclusion, Clcn7 is essential for lysosomal function and bone resorption. The gene knockout mouse models have revealed its significant roles in lysosome-related disorders such as those associated with FIG4 and VAC14 deficiencies, and in osteopetrosis. Understanding Clcn7's function provides potential new targets for treating related diseases that lack specific therapies [1,2].