ABSTRACT
Osterix (or Sp7) is an important transcription factor that promotes osteoblast differentiation by modulating the expression ofa range of target genes. Although many studies have focused on Osterix/Sp7 regulatory mechanisms, the detailed functionshave not been fully elucidated. Toward this end, in this study, we used CRISPR/Cas9 technology to knock out the zebrafishsp7 gene, and then analyzed its phenotype and biological function. Two knockout sp7 mutant lines were successfullyobtained. The bone mineralization level was significantly reduced in the zebrafish sp7-/- homozygote, resulting inabnormal tooth development in the larvae. Quantitative real-time polymerase chain reaction showed that loss of sp7 led todown-regulated expression of the dlx2b and bglap genes related to tooth development and bone mineralization, respectively. Moreover, cell transfection experiments demonstrated that Sp7 directly regulates the expression of dlx2b and bglapthrough Sp7-binding sites on the promoter regions of these two genes. Overall, this study provides new insight into the roleof Sp7 in bone mineralization and tooth development.