Importantly, these experiments do not take into account whether the poor bone quality observed in young oc/oc mice is due to expression of the a3 subunit of the V-ATPase in non-hematopoietic cells, i.e. gastric the parietal cells which are involved in calcium homeostasis [52]; however, as the fragility of osteopetrotic bone is common to multiple types of osteopetrosis this does not appear to be likely. Here, TCIRG1 is linked to osteopetrosis.