Primary osteoblast-enriched cells were harvested from the parietal bones of 3 to 5 day old wild-type C57BL/6J mice. In panel A, cells were seeded on BSA (white bars) or DLL1 (black bars) and transiently transfected with the 12xCSL-Luc reporter. In panel B, osteoblasts were transiently transfected with pcDNA3.1(−) (pcDNA) or with pcDNA-NICD (NICD) and co-transfected with the 12xCSL-Luc reporter. A CMV/β-galactosidase expression vector was co-transfected to test for transfection efficiency. Cells were allowed to recover for 16 h and subsequently cultured for 6 h in the absence of serum, exposed to vehicle or cortisol 1 μM, and harvested after 24 h. Data represent luciferase/β-galactosidase activity. Values are means ± SD, panel A n = 4; panel B n = 6. *Significantly different between BSA and DLL1 or pcDNA and NICD, p < 0.05; two-way ANOVA with Holm-Šídák post-hoc analysis.