COL4A3 and chronic kidney disease: FGF23 is regulated by an incompletely understood interplay between systemic factors that control mineral metabolism and local bone factors that modulate turnover and mineralization, including DMP1.18,21,23,24 In this study, we show in the 129 Sv and B6 Col4a3−/− mouse models of CKD, that DMP1 expression is reduced, and that upstream DMP1 deficiency contributes to FGF23 elevation in CKD.