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. Author manuscript; available in PMC: 2015 Jan 1.
Published in final edited form as: Calcif Tissue Int. 2013 Aug 22;94(1):68–77. doi: 10.1007/s00223-013-9773-z

Figure 1.

Figure 1

Notch signaling in bone homeostasis and bone microenvironment. Notch maintains mesenchymal stem cells (MSCs) in an undifferentiated stage by repressing Runx2. The role of Notch signaling in inhibiting osteoblast differentiation is mediated by Nfatc1 and by inhibition of Wnt/β-catenin. Notch gain of function increases immature pre-osteoblasts (Pre-Ob) pool by up-regulating transcription of Osx, Cyclin D, and Cyclin E. Notch signaling regulates osteoclastogenesis in a non-cell autonomous manner through Opg expression by osteoblasts in vivo. Additionally, osteoclastogenesis is repressed by cell autonomous function of Notch signaling in Pre-osteoclast (Pre-Oc). At the interface of osteoblast and HSC within the bone microenvironment, osteoblasts act as signal sending cells by expressing Jag1 and activate Notch1 signaling in hematopoietic stem cells (HSCs) resulting in an expansion of this cell population.