Regulation of alkaline phosphatase promoter activity by forkhead transcription factor FKHR.

Alkaline phosphatase (ALP) is a basic marker of osteoblast maturation and osteogenesis. However, the mechanisms of the ALP gene regulation in osteoblasts remain elusive. In this study, we examined the expression of forkhead transcription factor FKHR, a regulator of hepatic glucose metabolic and proapoptotic genes, in osteogenic cells and the effect of FKHR on transcription of the ALP gene. RT-PCR and immunoblot analyses revealed the expression of FKHR in osteogenic MC3T3-E1, SaOS2, and UMR 106 cells. Reporter assays demonstrated that the overexpression of FKHR stimulated ALP promoter activity through the forkhead response element in its promoter. These results suggest that ALP is a target gene regulated by FKHR and that FKHR contributes to osteoblast maturation and osteogenesis.