In a tumor necrosis factor (TNF)-α transgenic mice rheumatoid arthritis (RA) model, the highly expressed myostatin in the synovial tissue was reported to regulate the SMAD1-nuclear factor of activated t cells 1 (NFATC1) axis, thus drastically promoting RANKL-mediated osteoclastogenic differentiation. The gene discussed is SMAD1; the disease is rheumatoid arthritis.