Evidence includes, but is not limited to: (1) Clcn7−/− mice that specifically and exogenously express CLC7 in osteoblasts and macrophages that do not have osteopetrosis but have severe retinal and CNS degeneration similar to whole knockout mice; (2) CLC7-targeted mice that express an alternative transcript only in bone exhibit neurodegeneration but no osteopetrosis [95]. This evidence concerns the gene CLCN7 and osteopetrosis.