A Mutation in the Dmp1 Gene Alters Phosphate Responsiveness in Mice.

Autor:	Ichikawa S; Department of Medicine, Indiana University School of Medicine, 1120 West Michigan St, CL459, Indianapolis, IN, USA., Gerard-O'Riley RL; Department of Medicine, Indiana University School of Medicine, 1120 West Michigan St, CL459, Indianapolis, IN, USA., Acton D; Department of Medicine, Indiana University School of Medicine, 1120 West Michigan St, CL459, Indianapolis, IN, USA., McQueen AK; Department of Medicine, Indiana University School of Medicine, 1120 West Michigan St, CL459, Indianapolis, IN, USA., Strobel IE; Department of Medicine, Indiana University School of Medicine, 1120 West Michigan St, CL459, Indianapolis, IN, USA., Witcher PC; Department of Medicine, Indiana University School of Medicine, 1120 West Michigan St, CL459, Indianapolis, IN, USA., Feng JQ; Department of Biomedical Sciences, Texas A&M College of Dentistry, Dallas, Texas., Econs MJ; Department of Medicine, Indiana University School of Medicine, 1120 West Michigan St, CL459, Indianapolis, IN, USA.; Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana.
Jazyk:	angličtina
Zdroj:	Endocrinology [Endocrinology] 2017 Mar 01; Vol. 158 (3), pp. 470-476.
DOI:	10.1210/en.2016-1642
Abstrakt:	Mutations in the dentin matrix protein 1 (DMP1) gene cause autosomal recessive hypophosphatemic rickets (ARHR). Hypophosphatemia in ARHR results from increased circulating levels of the phosphaturic hormone, fibroblast growth factor 23 (FGF23). Similarly, elevated FGF23, caused by mutations in the PHEX gene, is responsible for the hypophosphatemia in X-linked hypophosphatemic rickets (XLH). Previously, we demonstrated that a Phex mutation in mice creates a lower set point for extracellular phosphate, where an increment in phosphorus further stimulates Fgf23 production to maintain low serum phosphorus levels. To test the presence of the similar set point defect in ARHR, we generated 4- and 12-week-old Dmp1/Galnt3 double knockout mice and controls, including Dmp1 knockout mice (a murine model of ARHR), Galnt3 knockout mice (a murine model of familial tumoral calcinosis), and phenotypically normal double heterozygous mice. Galnt3 knockout mice had increased proteolytic cleavage of Fgf23, leading to low circulating intact Fgf23 levels with consequent hyperphosphatemia. In contrast, Dmp1 knockout mice had little Fgf23 cleavage and increased femoral Fgf23 expression, resulting in hypophosphatemia and low femoral bone mineral density (BMD). However, introduction of the Galnt3 null allele to Dmp1 knockout mice resulted in a significant increase in serum phosphorus and normalization of BMD. This increased serum phosphorus was accompanied by markedly elevated Fgf23 expression and circulating Fgf23 levels, an attempt to reduce serum phosphorus in the face of improving phosphorus levels. These data indicate that a Dmp1 mutation creates a lower set point for extracellular phosphate and maintains it through the regulation of Fgf23 cleavage and expression. (Copyright © 2017 by the Endocrine Society.)
Databáze:	MEDLINE
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