Imatinib modulates the expression of genes involved in both osteogenic and adipogenic differentiation. Bone trephine explant cultures grown under osteoinductive conditions were treated with (■) or without (▴) 3 μM imatinib, and RNA was harvested on days 0, 1, 7, and 14. Quantitative real-time PCR was used to examine mRNA levels of key genes involved in osteoblast and adipocyte development. Treatment of cultures with imatinib up-regulated expression of osteoblast specific transcription factor osterix (OSX) and bone morphogenic protein 2 (BMP-2). Imatinib also up-regulated expression of adipocyte-specific transcription factors C/EBPα and PPARγ2 and the adipocyte-specific lipid transporter ALBP. For quantitative real-time analysis, expression levels were normalized to values obtained for β-actin. Mean values are shown; error bars represent the standard error of triplicate measurements.