Figure 1.

Temporal expression pattern of markers typical of osteoblast development in MC3T3-E1 cells. The cells progress through three general phases: (i) proliferation, (ii) extracellular matrix deposition and maturation, and (iii) mineralization. High-level expression of genes thought to contribute to the differentiated state of osteoblasts occurs at discrete time points during the differentiation process. Alkaline phosphatase (ALP), α1-collagen (COL), and osteonectin (OSN) are expressed at high levels near the end of the proliferative period and during the period of extracellular matrix deposition and maturation. Genes expressed at or near the time of mineralization include osteopontin (OPN) and osteocalcin (OSC).