STAT3 is critical for skeletal development and bone homeostasis by regulating osteogenesis

AbstractSkeletal deformities are typical AD-HIES manifestations, which are mainly caused by heterozygous and loss-of-function mutations in Signal transducer and activator of transcription 3 (STAT3). However, the mechanism is still unclear and the treatment strategy is limited. Herein, we reported that the mice with Stat3 deletion in osteoblasts, but not in osteoclasts, induced AD-HIES-like skeletal defects, including craniofacial malformation, osteoporosis, and spontaneous bone fracture. Mechanistic analyses revealed that STAT3 in cooperation with Msh homeobox 1(MSX1) drove osteoblast differentiation by promoting Distal-less homeobox 5(Dlx5) transcription. Furthermore, pharmacological activation of STAT3 partially rescued skeletal deformities in heterozygous knockout mice, while inhibition of STAT3 aggravated bone loss. Taken together, these data show that STAT3 is critical for modulating skeletal development and maintaining bone homeostasis through STAT3-indcued osteogenesis and suggest it may be a potential target for treatments.

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Tumor Suppressor LKB1 Inhibits Activation of Signal Transducer and Activator of Transcription 3 (STAT3) by Thyroid Oncogenic Tyrosine Kinase Rearranged in Transformation (RET)/Papillary Thyroid Carcinoma (PTC)

Molecular Endocrinology ◽

10.1210/me.2007-0269 ◽

2007 ◽

Vol 21 (12) ◽

pp. 3039-3049 ◽

Cited By ~ 21

Author(s):

Dong Wook Kim ◽

Hyo Kyun Chung ◽

Ki Cheol Park ◽

Jung Hwan Hwang ◽

Young Suk Jo ◽

...

Keyword(s):

Papillary Thyroid Carcinoma ◽

Tumor Suppressor ◽

Thyroid Carcinoma ◽

Malignant Tumors ◽

Kinase Domain ◽

Signal Transducer ◽

Papillary Thyroid ◽

Loss Of Function ◽

Amino Acid Region ◽

Transcription 3

Abstract The tumor suppressor LKB1 (STK11) is a cytoplasmic/nuclear serine/threonine kinase, defects in which cause Peutz-Jeghers syndrome (PJS) in humans and animals. Recent studies showed that loss of function of LKB1 is associated with sporadic forms of lung, pancreatic, and ovarian cancer. In cancer cells, LKB1 is inactivated by two mechanisms: mutations in its central kinase domain or complete loss of LKB1 expression. Inactivation of LKB1 is associated with progression of PJS and transformation of benign polyps into malignant tumors. This study examines the effect of LKB1 on regulation of STAT3 and expression of transcriptional targets of STAT3. The results show that LKB1 inhibits rearranged in transformation (RET)/papillary thyroid carcinoma (PTC)-dependent activation of signal transducer and activator of transcription 3 (STAT3), which is mediated by phosphorylation of STAT3 tyrosine 705 by RET/PTC. Suppression of STAT3 transactivation by LKB1 requires the kinase domain but not the kinase activity of LKB1. The centrally located kinase domain of LKB1 is an approximately 260-amino-acid region that binds to the linker domain of STAT3. Chromatin immunoprecipitation studies indicate that expression of LKB1 reduces the binding of STAT3 to its target promoters and suppresses STAT3-mediated expression of Cyclin D1, VEGF, and Bcl-xL. Knockdown of LKB1 by specific small interfering RNA led to an increase in STAT3 transactivation activity and promoted cell proliferation in the presence of RET/PTC. Thus, this study suggests that LKB1 suppresses tumor growth by inhibiting RET/PTC-dependent activation of oncogenic STAT3.

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Stat3 loss in mesenchymal progenitors causes Job syndrome–like skeletal defects by reducing Wnt/β-catenin signaling

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2020100118 ◽

2021 ◽

Vol 118 (26) ◽

pp. e2020100118

Author(s):

Prem Swaroop Yadav ◽

Shuhao Feng ◽

Qian Cong ◽

Hanjun Kim ◽

Yuchen Liu ◽

...

Keyword(s):

Osteoblast Differentiation ◽

Clinical Symptoms ◽

Bone Development ◽

Skeletal Development ◽

Genetic Disorder ◽

Long Bones ◽

Multiple Fractures ◽

Osteoprogenitor Cells ◽

Skeletal Defects ◽

Job Syndrome

Job syndrome is a rare genetic disorder caused by STAT3 mutations and primarily characterized by immune dysfunction along with comorbid skeleton developmental abnormalities including osteopenia, recurrent fracture of long bones, and scoliosis. So far, there is no definitive cure for the skeletal defects in Job syndrome, and treatments are limited to management of clinical symptoms only. Here, we have investigated the molecular mechanism whereby Stat3 regulates skeletal development and osteoblast differentiation. We showed that removing Stat3 function in the developing limb mesenchyme or osteoprogenitor cells in mice resulted in shortened and bow limbs with multiple fractures in long bones that resembled the skeleton symptoms in the Job Syndrome. However, Stat3 loss did not alter chondrocyte differentiation and hypertrophy in embryonic development, while osteoblast differentiation was severely reduced. Genome-wide transcriptome analyses as well as biochemical and histological studies showed that Stat3 loss resulted in down-regulation of Wnt/β-catenin signaling. Restoration of Wnt/β-catenin signaling by injecting BIO, a small molecule inhibitor of GSK3, or crossing with a Lrp5 gain of function (GOF) allele, rescued the bone reduction phenotypes due to Stat3 loss to a great extent. These studies uncover the essential functions of Stat3 in maintaining Wnt/β-catenin signaling in early mesenchymal or osteoprogenitor cells and provide evidence that bone defects in the Job Syndrome are likely caused by Wnt/β-catenin signaling reduction due to reduced STAT3 activities in bone development. Enhancing Wnt/β-catenin signaling could be a therapeutic approach to reduce bone symptoms of Job syndrome patients.

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Osteoblast differentiation and skeletal development are regulated by Mdm2–p53 signaling

The Journal of Cell Biology ◽

10.1083/jcb.200508130 ◽

2006 ◽

Vol 172 (6) ◽

pp. 909-921 ◽

Cited By ~ 171

Author(s):

Christopher J. Lengner ◽

Heather A. Steinman ◽

James Gagnon ◽

Thomas W. Smith ◽

Janet E. Henderson ◽

...

Keyword(s):

Osteoblast Differentiation ◽

Bone Development ◽

Skeletal Development ◽

Critical Role ◽

Mouse Development ◽

P53 Signaling ◽

Absolute Requirement ◽

Tumorigenic Potential ◽

Skeletal Defects ◽

Early Mouse

Mdm2 is required to negatively regulate p53 activity at the peri-implantation stage of early mouse development. However, the absolute requirement for Mdm2 throughout embryogenesis and in organogenesis is unknown. To explore Mdm2–p53 signaling in osteogenesis, Mdm2-conditional mice were bred with Col3.6-Cre–transgenic mice that express Cre recombinase in osteoblast lineage cells. Mdm2-conditional Col3.6-Cre mice die at birth and display multiple skeletal defects. Osteoblast progenitor cells deleted for Mdm2 have elevated p53 activity, reduced proliferation, reduced levels of the master osteoblast transcriptional regulator Runx2, and reduced differentiation. In contrast, p53-null osteoprogenitor cells have increased proliferation, increased expression of Runx2, increased osteoblast maturation, and increased tumorigenic potential, as mice specifically deleted for p53 in osteoblasts develop osteosarcomas. These results demonstrate that p53 plays a critical role in bone organogenesis and homeostasis by negatively regulating bone development and growth and by suppressing bone neoplasia and that Mdm2-mediated inhibition of p53 function is a prerequisite for Runx2 activation, osteoblast differentiation, and proper skeletal formation.

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Neutralisation of Dkk-1 protects from systemic bone loss during inflammation and reduces sclerostin expression

Annals of the Rheumatic Diseases ◽

10.1136/ard.2010.132852 ◽

2010 ◽

Vol 69 (12) ◽

pp. 2152-2159 ◽

Cited By ~ 130

Author(s):

Gisela Ruiz Heiland ◽

Karin Zwerina ◽

Wolfgang Baum ◽

Trayana Kireva ◽

Jörg H Distler ◽

...

Keyword(s):

Bone Loss ◽

Bone Formation ◽

Osteoblast Differentiation ◽

Bone Architecture ◽

Bone Homeostasis ◽

Osteocyte Death ◽

Primary Osteoblasts ◽

Systemic Bone Loss

IntroductionInflammation is a major risk factor for systemic bone loss. Proinflammatory cytokines like tumour necrosis factor (TNF) affect bone homeostasis and induce bone loss. It was hypothesised that impaired bone formation is a key component in inflammatory bone loss and that Dkk-1, a Wnt antagonist, is a strong inhibitor of osteoblast-mediated bone formation.MethodsTNF transgenic (hTNFtg) mice were treated with neutralising antibodies against TNF, Dkk-1 or a combination of both agents. Systemic bone architecture was analysed by bone histomorphometry. The expression of β-catenin, osteoprotegerin and osteocalcin was analysed. In vitro, primary osteoblasts were stimulated with TNF and analysed for their metabolic activity and expression of Dkk-1 and sclerostin. Sclerostin expression and osteocyte death upon Dkk-1 blockade were analysed in vivo.ResultsNeutralisation of Dkk-1 completely protected hTNFtg mice from inflammatory bone loss by preventing TNF-mediated impaired osteoblast function and enhanced osteoclast activity. These findings were accompanied by enhanced skeletal expression of β-catenin, osteocalcin and osteoprotegerin. In vitro, TNF rapidly increased Dkk-1 expression in primary osteoblasts and effectively blocked osteoblast differentiation. Moreover, blockade of Dkk-1 not only rescued impaired osteoblastogenesis but also neutralised TNF-mediated sclerostin expression in fully differentiated osteoblasts in vitro and in vivo.ConclusionsThese findings indicate that low bone formation and expression of Dkk-1 trigger inflammatory bone loss. Dkk-1 blocks osteoblast differentiation, induces sclerostin expression and leads to osteocyte death. Inhibition of Dkk-1 may thus be considered as a potent strategy to protect bone from inflammatory damage.

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Runx1 is a central regulator of osteogenesis for bone homeostasis by orchestrating BMP and WNT signaling pathways

PLoS Genetics ◽

10.1371/journal.pgen.1009233 ◽

2021 ◽

Vol 17 (1) ◽

pp. e1009233

Author(s):

Chen-Yi Tang ◽

Mengrui Wu ◽

Dongfeng Zhao ◽

Diep Edwards ◽

Abigail McVicar ◽

...

Keyword(s):

Bone Loss ◽

Wnt Signaling ◽

Signaling Pathways ◽

Signaling Pathway ◽

Skeletal Development ◽

Bmp Signaling ◽

Conditional Knockout ◽

Sequencing Analysis ◽

Bone Homeostasis ◽

Promoter Regions

Runx1 is highly expressed in osteoblasts, however, its function in osteogenesis is unclear. We generated mesenchymal progenitor-specific (Runx1f/fTwist2-Cre) and osteoblast-specific (Runx1f/fCol1α1-Cre) conditional knockout (Runx1 CKO) mice. The mutant CKO mice with normal skeletal development displayed a severe osteoporosis phenotype at postnatal and adult stages. Runx1 CKO resulted in decreased osteogenesis and increased adipogenesis. RNA-sequencing analysis, Western blot, and qPCR validation of Runx1 CKO samples showed that Runx1 regulates BMP signaling pathway and Wnt/β-catenin signaling pathway. ChIP assay revealed direct binding of Runx1 to the promoter regions of Bmp7, Alk3, and Atf4, and promoter mapping demonstrated that Runx1 upregulates their promoter activity through the binding regions. Bmp7 overexpression rescued Alk3, Runx2, and Atf4 expression in Runx1-deficient BMSCs. Runx2 expression was decreased while Runx1 was not changed in Alk3 deficient osteoblasts. Atf4 overexpression in Runx1-deficient BMSCs did not rescue expression of Runx1, Bmp7, and Alk3. Smad1/5/8 activity was vitally reduced in Runx1 CKO cells, indicating Runx1 positively regulates the Bmp7/Alk3/Smad1/5/8/Runx2/ATF4 signaling pathway. Notably, Runx1 overexpression in Runx2-/- osteoblasts rescued expression of Atf4, OCN, and ALP to compensate Runx2 function. Runx1 CKO mice at various osteoblast differentiation stages reduced Wnt signaling and caused high expression of C/ebpα and Pparγ and largely increased adipogenesis. Co-culture of Runx1-deficient and wild-type cells demonstrated that Runx1 regulates osteoblast−adipocyte lineage commitment both cell-autonomously and non-autonomously. Notably, Runx1 overexpression rescued bone loss in OVX-induced osteoporosis. This study focused on the role of Runx1 in different cell populations with regards to BMP and Wnt signaling pathways and in the interacting network underlying bone homeostasis as well as adipogenesis, and has provided new insight and advancement of knowledge in skeletal development. Collectively, Runx1 maintains adult bone homeostasis from bone loss though up-regulating Bmp7/Alk3/Smad1/5/8/Runx2/ATF4 and WNT/β-Catenin signaling pathways, and targeting Runx1 potentially leads to novel therapeutics for osteoporosis.

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Spop promotes skeletal development and homeostasis by positively regulating Ihh signaling

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1612520114 ◽

2016 ◽

Vol 113 (51) ◽

pp. 14751-14756 ◽

Cited By ~ 24

Author(s):

Hongchen Cai ◽

Aimin Liu

Keyword(s):

Osteoblast Differentiation ◽

Target Genes ◽

Skeletal Development ◽

Ubiquitin Ligase Complex ◽

Skeletal Defects ◽

Cullin 3 ◽

Hh Signaling ◽

Patched 1 ◽

Null Mutant Mice

Indian Hedgehog (Ihh) regulates chondrocyte and osteoblast differentiation through the Glioma-associated oncogene homolog (Gli) transcription factors. Previous in vitro studies suggested that Speckle-type POZ protein (Spop), part of the Cullin-3 (Cul3) ubiquitin ligase complex, targets Gli2 and Gli3 for degradation and negatively regulates Hedgehog (Hh) signaling. In this study, we found defects in chondrocyte and osteoblast differentiation inSpop-null mutant mice. Strikingly, both the full-length and repressor forms of Gli3, but not Gli2, were up-regulated inSpopmutants, and Ihh target genesPatched 1(Ptch1) and parathyroid hormone-like peptide (Pthlh) were down-regulated, indicating compromised Hh signaling. Consistent with this finding, reducing Gli3 dosage greatly rescued theSpopmutant skeletal defects. We further show that Spop directly targets the Gli3 repressor for ubiquitination and degradation. Finally, we demonstrate in a conditional mutant that loss ofSpopresults in brachydactyly and osteopenia, which can be rescued by reducing the dosage of Gli3. In summary, Spop is an important positive regulator of Ihh signaling and skeletal development.

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Pulmonary Infections and Surgical Complications in a Young Girl with Signal Transducer and Activator of Transcription 3 Loss-of-Function Mutation Hyperimmunoglobulin E Syndrome: A Case Report

Pediatric Allergy Immunology and Pulmonology ◽

10.1089/ped.2020.1225 ◽

2021 ◽

Vol 34 (1) ◽

pp. 33-37

Author(s):

Crhistian Toribio-Dionicio ◽

Dania Cubas-Guzmán ◽

Pedro Guerra-Canchari ◽

Vanuza García-Sánchez ◽

Wilmer Córdova-Calderón

Keyword(s):

Case Report ◽

Surgical Complications ◽

Young Girl ◽

Signal Transducer ◽

Pulmonary Infections ◽

Loss Of Function ◽

Hyperimmunoglobulin E Syndrome ◽

Transcription 3

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RhoA/Rock activation represents a new mechanism for inactivating Wnt/β-catenin signaling in the aging-associated bone loss

Cell Regeneration ◽

10.1186/s13619-020-00071-3 ◽

2021 ◽

Vol 10 (1) ◽

Author(s):

Wei Shi ◽

Chengyun Xu ◽

Ying Gong ◽

Jirong Wang ◽

Qianlei Ren ◽

...

Keyword(s):

Bone Loss ◽

Rho Kinase ◽

Small Gtpase ◽

Limb Bud ◽

Nuclear Accumulation ◽

Bone Homeostasis ◽

Loss Of Function ◽

Elderly Male ◽

Gain Of Function ◽

Embryonic Limb

AbstractThe Wnt/β-catenin signaling pathway appears to be particularly important for bone homeostasis, whereas nuclear accumulation of β-catenin requires the activation of Rac1, a member of the Rho small GTPase family. The aim of the present study was to investigate the role of RhoA/Rho kinase (Rock)-mediated Wnt/β-catenin signaling in the regulation of aging-associated bone loss. We find that Lrp5/6-dependent and Lrp5/6-independent RhoA/Rock activation by Wnt3a activates Jak1/2 to directly phosphorylate Gsk3β at Tyr216, resulting in Gsk3β activation and subsequent β-catenin destabilization. In line with these molecular events, RhoA loss- or gain-of-function in mouse embryonic limb bud ectoderms interacts genetically with Dkk1 gain-of-function to rescue the severe limb truncation phenotypes or to phenocopy the deletion of β-catenin, respectively. Likewise, RhoA loss-of-function in pre-osteoblasts robustly increases bone formation while gain-of-function decreases it. Importantly, high RhoA/Rock activity closely correlates with Jak and Gsk3β activities but inversely correlates with β-catenin signaling activity in bone marrow mesenchymal stromal cells from elderly male humans and mice, whereas systemic inhibition of Rock therefore activates the β-catenin signaling to antagonize aging-associated bone loss. Taken together, these results identify RhoA/Rock-dependent Gsk3β activation and subsequent β-catenin destabilization as a hitherto uncharacterized mechanism controlling limb outgrowth and bone homeostasis.

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