For example, a single exon of the Rankl (Tnfsf11, tumour necrosis factor ligand superfamily, member 11) gene was humanised to recapitulate the region of human RANKL targeted by the monoclonal antibody drug Denosumab, which inhibits osteoclastogenesis and increases bone density; the resulting mice were important for preclinical testing of the efficacy of the drug (non-humanised mice do not respond) in treating specific bone disorders in humans37. Here, TNFSF11 is linked to bone disorder.