Although localized to the mineralized matrix of bone, osteocytes are able to respond to systemic factors such as the calciotropic hormones 1,25(OH)2D3 and PTH. In the present studies, we examine the transcriptomic response to PTH in an osteocyte cell model and found that this hormone regulated an extensive panel of genes. Surprisingly, PTH uniquely modulated two cohorts of genes, one that was expressed and associated with the osteoblast to osteocyte transition and the other a cohort that was expressed only in the mature osteocyte. Interestingly, PTH's effects were largely to oppose the expression of differentiation-related genes in the former cohort, while potentiating the expression of osteocyte-specific genes in the latter cohort. A comparison of the transcriptional effects of PTH with those obtained previously with 1,25(OH)2D3 revealed a subset of genes that was strongly overlapping. While 1,25(OH)2D3 potentiated the expression of osteocyte-specific genes similar to that seen with PTH, the overlap between the two hormones was more limited. Additional experiments identified the PKA-activated phospho-CREB (pCREB) cistrome, revealing that while many of the differentiation-related PTH regulated genes were apparent targets of a PKA-mediated signaling pathway, a reduction in pCREB binding at sites associated with osteocyte-specific PTH targets appeared to involve alternative PTH activation pathways. That pCREB binding activities positioned near important hormone-regulated gene cohorts were localized to control regions of genes was reinforced by the presence of epigenetic enhancer signatures exemplified by unique modifications at histones H3 and H4. These studies suggest that both PTH and 1,25(OH)2D3 may play important and perhaps cooperative roles in limiting osteocyte differentiation from its precursors while simultaneously exerting distinct roles in regulating mature osteocyte function. Our results provide new insight into transcription factor-associated mechanisms through which PTH and 1,25(OH)2D3 regulate a plethora of genes important to the osteoblast/osteocyte lineage. Overall design: Fully differentiated IDG-SW3 cells were treated in biological triplicate with 100nM PTH for 24 hours prior to mRNA isolation and sequencing. Vehicle treated samples were previously published in GSE54783: http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSM1323967 http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSM1323968 http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSM1323969
The parathyroid hormone-regulated transcriptome in osteocytes: parallel actions with 1,25-dihydroxyvitamin D3 to oppose gene expression changes during differentiation and to promote mature cell function.
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View SamplesWe differentiated the murine IDG-SW3 cell line for 28 days until the cells displayed a mature osteocyte-like phenotype. Triplicate cultures of the IDG-SW3 cells were then treated with 50nM PTH (1-34) or vehicle control (PBS) for 24 hours. RNA was harvested from the cultures and used to perform RNA Seq analysis. We found that many genes previously shown to be markers of the osteocyte phenotype were strongly downregulated in response to PTH treatment. Furthermore, we found that genes known to inhibit cell motility were downregulated in response to PTH, whereas genes promoting motility were upregulated. This corresponds to the increased cell motility observed in PTH-treated IDG-SW3 cell cultures. Therefore, PTH induces a switch in mature IDG-SW3 cells from a osteocyte-like cell to a more motile phenotype. Overall design: RNA expression profiles of control and PTH-treated 28 day differentiated IDG-SW3 cells.
Parathyroid Hormone Induces Bone Cell Motility and Loss of Mature Osteocyte Phenotype through L-Calcium Channel Dependent and Independent Mechanisms.
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View SamplesEstrogens are well known steroid hormones necessary to maintain bone health. In addition, mechanical loading, which estrogen signaling may intersect with the Wnt/-catenin pathway, is also essential for bone health. As osteocytes are known as the major mechanosensory cells embedded in mineralized bone matrix, osteocyte ER deletion mice (EROcy/Ocy) were generated by mating ER floxed mice with Dmp1-Cre mice to determine functions of ER in osteocytes. Trabecular bone mineral density of female, but not male EROcy/Ocy mice was significantly decreased. Bone formation parameters in EROcy/Ocy were significantly decreased while osteoclast parameters were unchanged. This suggests that ER in osteocytes exerts osteoprotective function by positively controlling bone formation. To identify potential targets of ER, gene array analysis of Dmp1-GFP osteocytes FACS sorted from EROcy/Ocy and control mice was performed. Expression of Mdk and Sostdc1, both known inhibitors of Wnt, were significantly increased without alteration of the mature osteocyte marker Sost or -catenin. Hindlimb unloading exacerbated the trabecular bone loss, but surprisingly cortical bone was resistant. These studies show that ER in osteocytes has osteoprotective effects in trabecular bone through regulating expression of Wnt antagonists, but conversely plays a negative role in cortical bone loss due to unloading.
Estrogen receptor α in osteocytes regulates trabecular bone formation in female mice.
Sex, Specimen part
View SamplesPurpose of arrays were to determine what the effect of deletion of Mbtps1 gene was on gene expression of osteocytes in bone in vivo. DMP1 cre driver was used to delete the Mbtps1 gene in osteocytes and osteoblasts in bone. We then isolated osteocyte enriched bone particles from 40 week old male mice to determine the effect of this deletion on gene expression. We have previously shown that Mbtps1 is needed for transcription of Phex, DMP1, and MEPE genes in osteoblasts in culture. Arrays showed these genes were reduced as expected in osteocytes in vivo. Controls represent osteocyte enriched bone from 40 week old littermates. Also, as expected, Mbtps1 expression was reduced in these knockout mice
Deletion of Mbtps1 (Pcsk8, S1p, Ski-1) Gene in Osteocytes Stimulates Soleus Muscle Regeneration and Increased Size and Contractile Force with Age.
Sex
View SamplesTranscriptional profiling of an Fd-GOGAT1/GLU1 mutant in Arabidopsis thaliana reveals a multiple stress response and extensive reprogramming of the transcriptome
Transcriptional profiling of an Fd-GOGAT1/GLU1 mutant in Arabidopsis thaliana reveals a multiple stress response and extensive reprogramming of the transcriptome.
Specimen part
View SamplesThis SuperSeries is composed of the SubSeries listed below.
Targeting fibroblast growth factor receptors blocks PI3K/AKT signaling, induces apoptosis, and impairs mammary tumor outgrowth and metastasis.
Specimen part
View Samples4T1 mouse mammary carcinoma cells have an autocrine FGFR active loop leading to constitutive activation of downstream signaling pathways. We found that FGFR inhibitors have a strong effect on the proliferation and survival of these cells.
Targeting fibroblast growth factor receptors blocks PI3K/AKT signaling, induces apoptosis, and impairs mammary tumor outgrowth and metastasis.
Specimen part
View Samples4T1 mouse mammary carcinoma cells have an autocrine FGFR active loop leading to constitutive activation of downstream signaling pathways. We found that FGFR inhibitors have a strong effect on 4T1 tumors in-vivo.
Targeting fibroblast growth factor receptors blocks PI3K/AKT signaling, induces apoptosis, and impairs mammary tumor outgrowth and metastasis.
Specimen part
View SamplesThis SuperSeries is composed of the SubSeries listed below.
Transcription factor Runx3 regulates interleukin-15-dependent natural killer cell activation.
Sex, Age, Specimen part
View SamplesNK cells are innate immune cells that recognize and kill foreign, virally-infected and tumor cells without the need for prior immunization. NK expansion following viral infection is IL-2 or IL-15-dependent.
Transcription factor Runx3 regulates interleukin-15-dependent natural killer cell activation.
Sex, Age, Specimen part
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