Dalle Carbonare et al. showed that hypoxia (8% O2 for 10 h) followed by reoxygenation (21% O2 for 3 h) had a profound effect in promoting osteoclastogenesis (as characterized by increased osteoclast number and elevated mRNA expression of osteoclast markers RANK and cathepsin K) in the transgenic mouse model of sickle cell disease used [23]. The gene discussed is CTSK; the disease is sickle cell disease.