Organic phosphate but not inorganic phosphate regulates Fgf23 expression through MAPK and TGF-ꞵ signaling
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE245758 | GEO | 2024/03/18
REPOSITORIES: GEO
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Project description: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.
2015-05-30 | GSE47505 | GEO
Project description:Fibroblast growth factor 23 (FGF23), a hormone, mainly produced by osteocytes, regulates phosphate and vitamin D metabolism. By contrast, 1,25-dihydroxyvitamin D3, the active form of vitamin D, has been shown to enhance FGF23 production. While it is likely that osteocytes are heterogenous in terms of gene expression profiles, specific subpopulations of Fgf23-expressing osteocytes have not been identified. Single-cell RNA sequencing (scRNA-seq) technology can characterize the transcriptome of an individual cell. Recently, scRNA-seq has been used for bone tissue analysis. However, owing to technical difficulties associated with isolation of osteocytes, studies using scRNA-seq analysis to characterize FGF23-producing osteocytes are lacking. In this study, we characterized osteocytes secreting FGF23 from murine femurs in response to calcitriol (1,25-dihydroxyvitamin D3) using scRNA-seq. We first detected Dmp1, Mepe, and Phex expression in murine osteocytes by in situ hybridization and used these as marker genes of osteocytes. After decalcification, enzyme digestion, and removal of CD45+ cells, femoral bone cells were subjected to scRNA-seq. We identified cell clusters containing osteocytes using marker gene expression. While Fgf23 expression was observed in some osteocytes isolated from femurs of calcitriol-injected mice, no Fgf23 expression was detected in untreated mice. In addition, the expression of several genes which are known to be changed after 1,25-dihydroxyvitamin D3 treatment such as Ccnd2, Fn1, Igfbp7, Pdgfa, and Timp1 was also affected by calcitriol treatment in Fgf23-expressing osteocytes, but not in those lacking Fgf23 expression, even after calcitriol administration. Furthermore, box-and-whisker plots indicated that Fgf23 expression was observed in osteocytes with higher expression levels of the Fam20c, Dmp1, and Phex genes, whose inactivating mutations have been shown to cause FGF23-related hypophosphatemic diseases. These results indicate that osteocytes are heterogeneous with respect to their responsiveness to 1,25-dihydroxyvitamin D3, and sensitivity to 1,25-dihydroxyvitamin D3 is one of the characteristics of osteocytes with Fgf23 expression. It is likely that there is a subpopulation of osteocytes expressing several genes, including Fgf23, involved in phosphate metabolism.
2022-12-17 | GSE220836 | GEO
Project description:Fibroblast growth factor 23 (FGF23) is produced and secreted by osteocytes and is essential for maintaining phosphate homeostasis. One of the main regulators of FGF23, 1,25-dihydroxyvitamin D (1,25(OH)2D3), is primarily synthesized in the kidney from 25-hydroxyvitamin D (25(OH)D) by 1α-hydroxylase (encoded by CYP27B1). Hitherto, it is unclear whether osteocytes can convert 25(OH)D and thereby allow for 1,25(OH)2D3 to induce FGF23 production and secretion locally. Here, we differentiated MC3T3-E1 cells towards osteocyte-like cells expressing and secreting FGF23. Treatment with 10-6 M 25(OH)D resulted in conversion of 25(OH)D to 150 pmol/L 1,25(OH)2D3 and increased FGF23 expression and secretion but the converted amount of 1,25(OH)2D3 was insufficient to trigger an FGF23 response, so the effect on FGF23 was most likely directly caused by 25(OH)D. Interestingly, combining phosphate with 25(OH)D resulted in a synergistic increase in FGF23 expression and secretion, likely due to activation of additional signaling pathways by phosphate. Blockage of the vitamin D receptor (VDR) only partially abolished the effects of 25(OH)D or 25(OH)D combined with phosphate on Fgf23, while completely inhibiting the upregulation of cytochrome P450 family 24 subfamily A member 1 (Cyp24a1), encoding for 24-hydroxylase. RNA sequencing and in silico analyses showed that this could potentially be mediated by the nuclear receptors Retinoic Acid Receptor b (RARB) and Estrogen Receptor 2 (ESR2). Taken together, we demonstrate that osteocytes are able to convert 25(OH)D to 1,25(OH)2D3, but this is insufficient for FGF23 activation, implicating a direct effect of 25(OH)D in the regulation of FGF23, which occurs at least partially independent from its cognate vitamin D receptor Moreover, phosphate and 25(OH)D synergistically increase expression and secretion of FGF23, which warrants investigating consequences in patients receiving a combination of vitamin D analogues and phosphate supplements. These observations help us to further understand the complex relations between, phosphate, vitamin D and FGF23.
2024-08-01 | GSE239761 | GEO
Project description:Fibroblast growth factor-23 (FGF23), a circulating protein produced in bone, causes renal inorganic phosphate (Pi) wasting by down-regulation of sodium phosphate co-transporter 2a (Npt2a). The mechanism behind this action is unknown. We have previously generated transgenic mice (TG) expressing human wild-type FGF23 under the control of the α1 (I) collagen promoter. In this study we performed a large scale gene expression study of kidneys from TG mice and wild-type littermates. Several genes that play a role in Pi regulation had decreased expression levels, such as Npt2a, but also Pdzk1 which is a scaffolding protein known to interact with NPT2a. Importantly, the Klotho gene, a suggested crucial co-factor for FGF23 receptor binding and activation, was the most affected decreased gene. However, other genes proposed to regulate Pi levels, such as secreted Frizzled Related Protein 4 (sFRP4), Na+/H+ exchanger regulatory factor 1 (NHERF1) and the FGF-receptors 1-4, revealed no changes. Interestingly, expression levels of inflammatory response genes were increased and histological analysis revealed tubular nephropathy in the TG mice kidneys. In conclusion, FGF23 TG mice have altered kidney gene expression levels of several genes thought to be part of Pi homeostasis and an increase in inflammatory response genes, data supported by histological analysis. These findings may lead to further understanding of how FGF23 mediates its actions on renal Pi regulation. Experiment Overall Design: Five kidneys from FGF23 TG mice and five kidneys from WT littermates was used for Affymetrix Genechip analysis. One Genechip was used/animal. Animals were 8 weeks old when kidneys were collected.
2008-06-15 | E-GEOD-6979 | biostudies-arrayexpress
Project description:FGF23 is a bone-derived hormone that mediates renal phosphate reabsorption and 1,25(OH)2 vitamin D metabolism via its required co-receptor alpha-Klotho (KL). The functional pathways guiding this hormone’s activity in kidney have not been studied extensively, and whether using other factors with overlapping signaling profiles to produce FGF23-like responses is unclear. To map FGF23-related genes, gene array and single-cell RNA sequencing were utilized on wild type mouse kidneys. After identifying Heparin-binding EGF-like growth factor (HBEGF) as an up-regulated gene in response to FGF23 delivery, KL-null and phosphate-deficient diet fed mouse models and in vitro experiments were utilized to further test HBEGF bioactivity in kidney. Gene array demonstrated that HBEGF was significantly up-regulated following FGF23 delivery to wild type (WT) mice. Next, mice injected with HBEGF had phenotypes consistent with partial FGF23-mimetic activity including robust induction of EGR1, and increased CYP24A1 mRNAs. Single cell RNA sequencing showed overlapping HBEGF and EGFR expression in the proximal tubule (PT), and KL expression in PT and distal tubule (DT) segments. In KL-null mice devoid of canonical FGF23 signaling, HBEGF injections significantly increased EGR1 and CYP24A, and correction of basally-elevated CYP27B1 was observed. In addition, mice placed on a phosphate deficient diet to suppress FGF23 had endogenously increased CYP27B1 mRNA, which was rescued in mice receiving HBEGF. In HEK293 renal epithelial cells, HBEGF and FGF23 increased CYP24A1 mRNA. Targeting pathways known to be downstream of FGF23 in kidney may help to control renal phosphate handling in diseases of altered FGF23 bioactivity.
2020-10-01 | GSE138992 | GEO
Project description:Fibroblast growth factor-23 (FGF23), a circulating protein produced in bone, causes renal inorganic phosphate (Pi) wasting by down-regulation of sodium phosphate co-transporter 2a (Npt2a). The mechanism behind this action is unknown. We have previously generated transgenic mice (TG) expressing human wild-type FGF23 under the control of the α1 (I) collagen promoter. In this study we performed a large scale gene expression study of kidneys from TG mice and wild-type littermates. Several genes that play a role in Pi regulation had decreased expression levels, such as Npt2a, but also Pdzk1 which is a scaffolding protein known to interact with NPT2a. Importantly, the Klotho gene, a suggested crucial co-factor for FGF23 receptor binding and activation, was the most affected decreased gene. However, other genes proposed to regulate Pi levels, such as secreted Frizzled Related Protein 4 (sFRP4), Na+/H+ exchanger regulatory factor 1 (NHERF1) and the FGF-receptors 1-4, revealed no changes. Interestingly, expression levels of inflammatory response genes were increased and histological analysis revealed tubular nephropathy in the TG mice kidneys. In conclusion, FGF23 TG mice have altered kidney gene expression levels of several genes thought to be part of Pi homeostasis and an increase in inflammatory response genes, data supported by histological analysis. These findings may lead to further understanding of how FGF23 mediates its actions on renal Pi regulation. Keywords: Genetic Modification
2007-11-29 | GSE6979 | GEO
Project description:These data represent the global gene expression profile of Mycobacterium tuberculosis after 24 hrs and 72 hrs of inorganic phosphate starvation. Differentially regulated genes appear to include those encoding proteins involved in adaptation to phosphate starvation, namely those involved in phosphate regulation and phosphate assimilation, as well as those involved in the stringent response.
2009-09-22 | GSE14840 | GEO
Project description:Bacillus subtilis responds to phosphate starvation stress by inducing the PhoP and SigB regulons. While the PhoP regulon provides a specific response to phosphate starvation stress, maximizing the acquisition of phosphate (Pi) from the environment and reducing the cellular requirement for this essential nutrient, the SigB regulon provide non-specific resistance to stress by protecting essential cellular components such as DNA and membranes. We have characterized the phosphate starvation stress response of B. subtilis at a genome-wide level using DNA macroarrays. A combination of outlier and cluster analyses identified putatively new members of the PhoP regulon, namely yfkN (2',3'-cyclic-nucleotide 2'-phosphodiesterase), yurI (ribonuclease), yjdB (unknown) and vpr (extracellular serine protease). YurI is thought to be responsible for the non-specific degradation of RNA, whilst the activity of YfkN on various nucleotide phosphates suggests that it could act on substrates liberated by YurI which produces 3` or 5` phosphoribonucleotides. The putative new PhoP regulon members are either known or predicted to be secreted and are likely to be important for the recovery of inorganic phosphate from a variety of organic sources of phosphate in the environment. Keywords: other
2005-11-16 | GSE2667 | GEO
Project description:In bacteria, the availability of environmental inorganic phosphate is typically sensed by the conserved PhoRB two-component signaling pathway, which uses the flux through the Pst phosphate transporter as a readout of the extracellular phosphate level to control a variety of phosphate-responsive genes. While the sensing of environmental phosphate is well-established, the regulatory effects of cytoplasmic phosphate are still unclear. Here, we disentangle the physiological and transcriptional responses of Caulobacter crescentus to changes in the environmental and cytoplasmic phosphate levels. To this end, we are uncoupling phosphate uptake from the activity of the Pst system by producing an additional, heterologous phosphate transporter. This approach reveals a bi-pronged response of C.crescentus to phosphate limitation, in which the PhoRB signaling mostly facilitates the utilization of alternative phosphate sources, whereas the cytoplasmic phosphate level controls the morphological and physiological adaptation of cells to growth in conditions of global phosphate limitation. These findings open the door to a more comprehensive understanding of phosphate signaling in bacteria.
2023-10-20 | GSE244776 | GEO
Project description:In E. coli the phosphate homeostasis is regulated by the Pst system and the two-component system PhoB/R. Pathogens like E. coli O157:H7 are responsible for many outbreaks and can be found and survive in poor inorganic phosphate (Pi) environments. To understand global EHEC O157:H7 EDL933 strain responses to Pi-starvation, we compared the transcriptomes of EDL933 the WT strain grown in MOPS Pi rich medium and that grown in MOPS Pi poor medium, using the Affymetrix GeneChip® E. coli Genome 2.0 Array. Also we investigated the EDL933 global response to the absence of PhoB by comparing the transcriptomes of the WT strain the ΔphoB mutant both grown in Low Pi
2014-03-15 | GSE50529 | GEO