Polynucleotides and polypeptide sequences involved in the process of bone remodeling

Pharmaceutical composition for use in the modulation of osteoclast differentiation in vivo, in the prevention of bone disease or in the treatment of bone disease comprising an isolated polypeptide comprising a sequence selected from the group consisting of: a) SEQ ID No. 48, b) a polypeptide encoded by SEQ ID No. 1, c) a fragment of either a) or b) that is capable of promoting or inhibiting osteoclast differentiation, and d) an analog of either a) or b) that is capable of promoting or inhibiting osteoclast differentiation, wherein said analog has at least 90% sequence similarity to the polypeptide of a) or b), and a pharmaceutically acceptable carrier.