Putative Mechanism(s) of Action in IVD. While the deletion of RANKL clearly induces osteopetrosis (high bone mass)98 and deletion of RANKL decoy OPG induces bone loss,99 only a couple of studies have investigated the effect of expression and regulation of RANKL/OPG system on the IVD. The gene discussed is TNFSF11; the disease is osteopetrosis.