OSTM1 and osteopetrosis: Our data, together with others’ findings that OSTM1-deficient mice and patients with Ostm1 mutations exhibited severe osteopetrosis due to osteoclast dysfunction [20,21,22,53], strongly indicate that OSTM1 phosphorylation and interaction with LRRK1 may play a critical role in the regulation of osteoclast function via modulating lysosomal peripheral movement and acid secretion on the ruffled border.