RANKL down-regulates the expression of MafB during osteoclastogenesis. (A) RAW264.7 cells were cultured for the indicated times in the presence of RANKL. RT-PCR was performed for the expression of MafB, NFATc1, OSCAR, TRAP, and HPRT. (B-C) BMMs were cultured for the indicated times in the presence of M-CSF and RANKL. Northern blot analysis (B) and Western blot analysis (C) were performed to assess the expression of the indicated genes. (D) RAW264.7 cells were cultured with RANKL for 2 days in the presence of various inhibitors: mock (DMSO), SB203580 (20 μM), LY294002 (10 μM), PD98059 (20 μM), TPCK (5 μM), or SP600125 (5 μM). RT-PCR was performed for the expression of MafB and HPRT. (E) BMMs were cultured with M-CSF and RANKL for 2 days in the presence of various inhibitors: mock (DMSO), SB203580 (20 μM), or SP600125 (5 μM). RT-PCR was performed for the expression of MafB and HPRT.