Dataset Information


Immediate Effects of Extracellular Phosphate on Gene Expression in Primary Murine Osteoblasts

ABSTRACT: That phosphate homeostasis is tightly linked to skeletal mineralization is probably best underscored by the fact that the phosphaturic hormone FGF23 is primarily expressed by terminally differentiated osteoblasts/osteocytes, and that increased circulating FGF23 levels are causative for different types of hypophosphatemic rickets. In contrast, FGF23-inactivation results in hyperphosphatemia, and unexpectedly this phenotype is associated with severe osteomalacia in Fgf23-deficient mice. In this context it is interesting that different types of bone cells have been shown to respond to extracellular phosphate, thereby raising the concept that phosphate can act as a signaling molecule. To identify phosphate-responsive genes in primary murine osteoblasts we performed genome-wide expression analysis with cells maintained in medium containing either 1 mM or 4 mM sodium phosphate for 6 hours. As confirmed by qRT-PCR, this analysis revealed that several known osteoblast differentiation markers (Bglap, Ibsp or Phex) were unaffected by raising extracellular phosphate levels. In contrast, we found that the expression of Enpp1 and Ank, two genes encoding inhibitors of matrix mineralization, was induced by extracellular phosphate, while the expression of Sost and Dkk1, two genes encoding inhibitors of bone formation, was negatively regulated. The ability of osteoblasts to respond to extracellular phosphate was dependent on their differentiation state, and shRNA-dependent repression of the phosphate transporter Slc20a1 in MC3T3-E1 cells partially abolished their molecular response to phosphate. Taken together, our results provide further evidence for a role of extracellular phosphate as a signaling molecule and raise the possibility that severe hyperphosphatemia can negatively affect skeletal mineralization. Overall design: Primary osteoblasts were obtained from the calvariae of 5 days old mice. Cells were isolated by sequential digestion with collagenase/dispase and subsequently cultured in a-MEM (including 10 % FBS) for 3 days, until they were 80 to 90 % confluent. Thereafter, they were cultured in non-modified-a-MEM or phosphate enriched a-MEM. The expression patterns of the modified culture was then compared to the non-modified culture.

INSTRUMENT(S): [Mouse430_2] Affymetrix Mouse Genome 430 2.0 Array

SUBMITTER: Thomas Streichert 

PROVIDER: GSE47505 | GEO | 2015-05-30



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