Fig. 2.

C/EBPβ as a master switch in osteoclast differentiation. a The LAP isoform of C/EBPβ induces expression of MafB. MafB binds to and inactivates the osteoclastic transcription factors c-Fos, Mitf, and NFATc1. Inactivation of these key transcription factors prevents osteoclast differentiation by inhibition of osteoclast target gene expression of OSCAR and NFATc1, resulting in inhibition of NFATc1 target genes, including the cell fusion genes DC-STAMP, ATP6v0d2, and TNFα (partially derived from [4, 34]). b The LIP isoform of C/EBPβ inhibits MafB expression. As a result, MafB becomes limiting, and lack of MafB permits access of the osteoclast transcription factors (often in conjunction with NFATc1 as a major osteoclast transcription factor) to activate target genes and osteoclast differentiation