Fig. 2.

Functions of ERRα and γ in mineralizing cells. a Effects of ERRα and ERRγ on mineralizing cells. ERRα exerts early effects on mesenchymal cells inducing commitment to the adipocyte lineage (green arrow), while repressing commitment to the osteoblast one (red arrow). ERRα also acts later in this lineage, inhibiting osteoblast maturation, an activity shared by ERRγ. The two repressive effects of ERRα on osteoblast differentiation contribute to bone loss during aging and hormonal deficiency, respectively. Furthermore ERRγ decreases trabecular bone mass but promotes calcification in vascular smooth muscle cell (VSMC). Note that the effect of ERRγ on hormone deficiency-induced bone loss has not been investigated so far. b Effects of ERRα and γ on Runx2 expression and activity. ERRα activates (green arrow) or repress (red arrow) Runx2 expression in the presence of PGC-1α or β, respectively. Both ERRα and γ inhibit the transcriptional activities of the Runx2 protein. See text for details and references