NFKB1 and osteopetrosis: Indeed, application of NF-κB inhibitors (Takatsuna et al., 2005) or deficiency in the NF-κB components p50/p52 (Yamashita et al., 2007) leads to impaired NFATc1 induction, while knockout of NF-κB in mice leads to osteopetrosis (Table 1) due to lack of mature OCLs (Franzoso et al., 1997; Iotsova et al., 1997).