CLCN7 and autosomal recessive osteopetrosis: In humans, autosomal recessive osteopetrosis (ARO) is mainly (in >70% cases) associated with mutations in two genes: TCIRG1, encoding the α3 subunit of v-ATPase [76], and CLCN7, encoding anion transporter CLC-7 that works with v-ATPase to acidify the bone while maintaining electroneutrality [77].