Figure 5.

Proximal regulatory region‒mediated genomic regulation of Fgf23 expression by 1,25(OH)₂D₃. (A) FGF23-PKO (PKO), FGF23-16KO (16KO), FGF23-38KO (38KO), and FGF23-IKO (IKO) mice and their wild-type (WT) littermates were treated with either vehicle (Veh) or 10 ng/g bw of 1,25(OH)₂D₃ for 6 h. Serum P and iFGF23 levels and Fgf23 expression level in bone are presented. Gene expression level represents relative quantitation (RQ) normalized to Gapdh (ΔΔCT). Each value is the average of six to eight mice per group, and error bars represent SEM. *P < 0.05 compared with vehicle controls; ^#P < 0.05 compared with WT littermates that received the same treatments. (B) FGF23-PKO and WT littermates were treated with 10 ng/g bw 1,25(OH)₂D₃ for 0, 1, 3, 6, 12, and 24 h. Serum P and iFGF23 levels and expression levels of the indicated genes in bone are presented. Gene expression level represents RQ normalized to Gapdh (ΔΔCT). Each value is the average of four to eight mice per group, and error bars represent SEM. *P < 0.05 compared with 0-h groups; ^#P < 0.05 compared with WT littermates that received the same treatments.