The secreted form is a binding and antagonizing protein for members of the TGF-beta family, such us activin, BMP2 and MSTN. Inhibits activin A-, activin B-, BMP2- and MSDT-induced cellular signaling; more effective on activin A than on activin B. Involved in bone formation; inhibits osteoclast differentiation. Involved in hematopoiesis; involved in differentiation of hemopoietic progenitor cells, increases hematopoietic cell adhesion to fibronectin and seems to contribute to the adhesion of hematopoietic precursor cells to the bone marrow stroma. The nuclear form is probably involved in transcriptional regulation via interaction with MLLT10 (By similarity). Interacts with INHBA and INHBB. Interacts with FN1. Interacts with ADAM12. Interacts with MLLT10; the interaction enhances MLLT10 in vitro transcriptional activity and self-association. Interacts with MSTN (By similarity).