Clcn7 as a new mouse model of Albers-Schönberg disease.

Dominant negative mutations in CLCN7, which encodes a homodimeric chloride channel needed for matrix acidification by osteoclasts, cause Albers-Schönberg disease (also known as autosomal dominant osteopetrosis type 2). More than 25 different CLCN7 mutations have been identified in patients affected with Albers-Schönberg disease, but only one mutation (Clcn7) has been introduced in mice to create an animal model of this disease. Here we describe a mouse with a different osteopetrosis-causing mutation (Clcn7). Compared to Clcn7 mice, 12-week-old Clcn7 mice have significantly increased trabecular bone volume, consistent with Clcn7 acting as a dominant negative mutation. Clcn7 and Clcn7 mice die by 1month of age and resemble Clcn7 knockout mice, which indicate that p.F318L mutant protein is non-functional and p.F318L and p.G213R mutant proteins do not complement one another. Since it has been reported that treatment with interferon gamma (IFN-G) improves bone properties in Clcn7 mice, we treated Clcn7 mice with IFN-G and observed a decrease in osteoclast number and mineral apposition rate, but no overall improvement in bone properties. Our results suggest that the benefits of IFN-G therapy in patients with Albers-Schönberg disease may be mutation-specific.