Osterix (OSX)

Sp family proteins are sequence-specific DNA-binding proteins characterized by an amino-terminal trans-activation domain and three carboxy-terminal zinc finger motifs. OSX is a bone specific transcription factor and is required for osteoblast differentiation and bone formation.The deduced 431-amino acid protein has a calculated molecular mass of 45 kD and contains an N-terminal proline-rich domain and 3 consecutive C-terminal C2H2 zinc finger motifs. Mouse and human SP7 share 95% amino acid identity. The lack of a glutamine-rich domain and the presence of a proline-rich domain distinguish SP7 from other SP family proteins. In situ hybridization of human embryonic tissues revealed SP7 expression in osteoblastic cells of the appendicular and craniofacial skeleton.