NFKB2 and osteopetrosis: Similarly, deficiency of c-Fos abrogates NFATc1 induction and osteoclastogenesis in vitro (Takayanagi et al., 2002) and results in marked osteopetrosis in vivo (Wang et al., 1992) (Table 1), while overexpression of c-Fos can rescue NFATc1 expression in p50/p52 deficient cells (Yamashita et al., 2007).