EGR1 plays an important role in BMP9-mediated osteoblast differentiation by promoting SMAD1/5 phosphorylation.

Bone morphogenetic proteins (BMPs) are essential regulators of skeletal homeostasis, and BMP9 is the most potently osteogenic among them. Here, we found that BMP9 and BMP2 rapidly induced early growth response 1 (EGR1) protein expression in osteoblasts through MEK/ERK pathway-dependent transcriptional activation. Knock-down of EGR1 using siRNA significantly inhibited BMP9-induced matrix mineralization and osteogenic marker gene expression in osteoblasts.