A study by Pettit, et al showed that tumor necrosis factor-related activation-induced cytokine (TRANCE) knockout mice were deficient in osteoclasts and protected from bone loss in a serum transfer model of arthritis, demonstrating in vivo the importance of RANKL and osteoclastogenesis in bone loss associated with RA [13]. The gene discussed is TNFSF11; the disease is rheumatoid arthritis.