Required for osteoclast and melanocyte maturation and function. Chloride channel 7 are heteromers of alpha (CLCN7) and beta (OSTM1) subunits. Requires CLCN7 to travel to lysosomes. Expressed primarily in osteoclasts and melanocytes as well as brain, kidney and spleen. Found at lower levels in the thymus, testis, heart and liver. Expression was detected in fetal liver neuronal and bone tissues (12.5 dpc and 15.5 dpc). High expression was detected in thymus and gut at 18.5 dpc and continued postnatally. Expression in bone (mandible and vertebrae) and brain tissues (cerebellum, hippocampus and cortex) remained high after birth. In addition high expression was detected in kidney, spleen and skin at P5 and P10. Undergoes proteolytic cleavage in the luminal domain, the cleaved fragments might be linked by disulfide bonds with the remnant of the protein. Highly N-glycosylated. Defects in Ostm1 are the cause of the spontaneous gray-lethal (gl) mutant, which is responsible for a coat color defect and for the development of the most severe autosomal recessive form of osteopetrosis. Osteopetrosis is a rare genetic disease characterized by abnormally dense bone, due to defective resorption of immature bone. The disorder occurs in two forms: a severe autosomal recessive form occurring in utero, infancy, or childhood, and a benign autosomal dominant form occurring in adolescence or adulthood. Belongs to the OSTM1 family.