OSTM1 and osteopetrosis: During the first electrophysiological analysis of osteopetrosis-causing ClC-7 missense mutations, it was surprisingly found that, besides loss-of-function mutations due to impaired ER exit or reduced ion transport, several pathogenic ClC-7 mutations accelerated the voltage-dependent activation of ClC-7PM/Ostm1 (Leisle et al., 2011).