Smad function and intranuclear targeting share a Runx2 motif required for osteogenic lineage induction and BMP2 responsive transcription

Afzal, Faiza; Pratap, Jitesh; Ito, Kosei; Ito, Yoshiaki; Stein, Janet L.; Wijnen, André J. van; Lian, Jane B.; Javed, Amjad

doi:10.1002/jcp.20258

Cited by 146 publications

(158 citation statements)

References 44 publications

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“…A reduction in activated p-Smad and Runx2 expression occurs, but the reduced Runx2 was not a consequence of direct miR-135 targeting to Runx2 3Ј UTR (data not shown). Decreased Runx2 levels and functional activity can occur, resulting from decreased phosphorylated Smad1/5, which is necessary for Runx2-Smad5 interactions (29). Cooperation between Runx2 and sustained p-Smad5 is clearly established for osteoblastspecific gene expression (10,11).…”

Section: Discussionmentioning

confidence: 99%

A microRNA signature for a BMP2-induced osteoblast lineage commitment program

Hassan

Volinia

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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Bone morphogenetic proteins (BMPs) are potent morphogens that activate transcriptional programs for lineage determination. How BMP induction of a phenotype is coordinated with microRNAs (miRNAs) that inhibit biological pathways to control cell differentiation, remains unknown. Here, we show by profiling miRNAs during BMP2 induced osteogenesis of C2C12 mesenchymal cells, that 22 of 25 miRNAs which significantly changed in response to BMP2 are down-regulated. These miRNAs are each predicted to target components of multiple osteogenic pathways. We characterize two representative miRNAs and show that miR-133 directly targets Runx2, an early BMP response gene essential for bone formation, and miR-135 targets Smad5, a key transducer of the BMP2 osteogenic signal, controlled through their 3UTR sequences. Both miRNAs functionally inhibit differentiation of osteoprogenitors by attenuating Runx2 and Smad5 pathways that synergistically contribute to bone formation. Although miR-133 is known to promote MEF-2-dependent myogenesis, we have identified a second complementary function to inhibit Runx2-mediated osteogenesis. Our key finding is that BMP2 controls bone cell determination by inducing miRNAs that target muscle genes but mainly by down-regulating multiple miRNAs that constitute an osteogenic program, thereby releasing from inhibition pathway components required for cell lineage commitment. Thus, our studies establish a mechanism for BMP morphogens to selectively induce a tissuespecific phenotype and suppress alternative lineages.S keletal development requires stringent control of a program for gene activation and suppression in response to physiological cues. The potent osteogenic bone morphogenetic proteins (BMPs) (BMP2/7) and canonical Wnt signaling activate skeletal-related genes for formation of cartilage and bone (1-3). BMPs regulate the differentiation of multiple cell types (4-6) but will also drive commitment of mesenchymal stem cells into a specific lineage. BMP2, for example, supports osteoblastogenesis (7, 8). There has been a principal focus on identifying the mechanisms by which only one cell phenotype is activated by BMP2. BMP2 intracellular receptor Smads, particularly Smad5, activates osteoblast-essential genes, including the transcription factors required for in vivo bone formation Runx2 (Cbfa1/ AML3) and Osterix (9-11). The contribution of global mechanisms for suppression of alternative lineages is equally important for understanding tissue development and diseases.MicroRNAs (miRNAs) have emerged as key negative regulators of diverse biological and pathological processes, including developmental timing, organogenesis, apoptosis, cell proliferation, and differentiation (reviewed in ref. 12) and in the control of tumorigenesis (13,14). miRNAs are small (22-nt) endogenous noncoding RNAs that anneal to the 3Ј UTR of target mRNAs to mediate inhibition of translation and lower protein levels. It remains to be established how specific miRNAs contribute to regulate the onset of a tissue-specific phenotype i...

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Section: Discussionmentioning

confidence: 99%

A microRNA signature for a BMP2-induced osteoblast lineage commitment program

Hassan

Volinia

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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506

437

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“…Adenoviral Transduction of Cells. Adenovirus expressing WT and mSTDs were generated by Adenovator system (BIOgene) and have been reported previously (39). Runx2-null cells were plated at a density of 1 ϫ 10 5 cells per well of a six-well plate or 1 ϫ 10 6 cells per 100-mm plate.…”

Section: Methodsmentioning

confidence: 99%

Runx2 deficiency and defective subnuclear targeting bypass senescence to promote immortalization and tumorigenic potential

Zaidi

Pande

Pratap

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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The osteogenic Runt-related (Runx2) transcription factor negatively regulates proliferation and ribosomal gene expression in normal diploid osteoblasts, but is up-regulated in metastatic breast and prostate cancer cells. Thus, Runx2 may function as a tumor suppressor or an oncogene depending on the cellular context. Here we show that Runx2-deficient primary osteoblasts fail to undergo senescence as indicated by the absence of ␤-gal activity and p16 INK4a tumor suppressor expression. Primary Runx2-null osteoblasts have a growth advantage and exhibit loss of p21 WAF1/CIP1 and p19 ARF expression. Reintroduction of WT Runx2, but not a subnuclear targeting-defective mutant, induces both p21 WAF/CIP1 and p19 ARF mRNA and protein resulting in cell-cycle inhibition. Accumulation of spontaneous phospho-H2A.X foci, loss of telomere integrity and the Mre11/Rad50/Nbs1 DNA repair complex, and a delayed DNA repair response all indicate that Runx2 deficiency leads to genomic instability. We propose that Runx2 functions as a tumor suppressor in primary diploid osteoblasts and that subnuclear targeting contributes to Runx2-mediated tumor suppression.cancer ͉ genomic instability ͉ growth control ͉ nuclear organization ͉ osteoblast W hen exposed to inappropriate growth signals, mammalian cells engage in elaborate mechanisms that provide alternative fates to prevent tumorigenesis. These defenses include apoptosis and senescence, which guard against unrestrained proliferation. Several tumor suppressors, including the retinoblastoma protein (pRb), p53, and the products of the INK4b-ARF-INK4a locus (p15-p19-p16), control telomere integrity, cellular senescence, and genomic stability (1-4). Tumors arise when cells override these intrinsic defenses. Cancer cells typically exhibit independence from extrinsic growth signals, lack of senescence or apoptosis, compromised telomeric integrity, and genomic instability, as well as changes in nuclear organization (2, 4-6). However, mice with genetic ablations of tumor suppressors are prone to tumorigenesis that is often lineage-restricted (7, 8). These observations suggest that lineage-specific mechanisms contribute to tumorigenesis.Runt-related (Runx) transcription factors determine cell fate and regulate lineage-specific proliferation and differentiation (9-11). Genetic studies reveal that Runx1 is essential for definitive hematopoiesis, Runx2 is required for osteogenesis, and Runx3 is involved in gut development as well as neurogenesis (12-16). Runx proteins support epigenetic regulation at mitosis and control ribosomal gene expression during the cell cycle (9)(10)(11)(17)(18)(19). Runx transcription factors are nuclear-scaffolding proteins that integrate signaling pathways by organizing macromolecular complexes in nuclear microenvironments and facilitating chromatin remodeling (20). Mice with gene replacements expressing subnuclear targeting defective mutants (mSTDs) of Runx1 or Runx2 from the native loci exhibit phenotypes identical to mice in which the gene has been ablated (21, 22), sugge...

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“…In addition to transcriptional regulation by BMP2, Runx2 physically interacts with Smad proteins to form active transcriptional complexes for osteogenic gene expression, resulting in the synergy between Runx2 and BMP2. 62,63 Therefore, we hypothesize that NELL-1 may augment BMP2/Smad osteogenesis by stimulating canonical Wnt signaling and promoting Runx2.…”

Section: Proposed Molecular Mechanisms Of Nell-1 and Bmp2 Effects On mentioning

confidence: 99%

Novel Wnt Regulator NEL-Like Molecule-1 Antagonizes Adipogenesis and Augments Osteogenesis Induced by Bone Morphogenetic Protein 2

Shen

James

Zhang

et al. 2016

The American Journal of Pathology

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The differentiation factor NEL-like molecule-1 (NELL-1) has been reported as osteoinductive in multiple in vivo preclinical models. Bone morphogenetic protein (BMP)-2 is used clinically for skeletal repair, but in vivo administration can induce abnormal, adipose-filled, poorquality bone. We demonstrate that NELL-1 combined with BMP2 significantly optimizes osteogenesis in a rodent femoral segmental defect model by minimizing the formation of BMP2-induced adipose-filled cystlike bone. In vitro studies using the mouse bone marrow stromal cell line M2-10B4 and human primary bone marrow stromal cells have confirmed that NELL-1 enhances BMP2-induced osteogenesis and inhibits BMP2-induced adipogenesis. Importantly, the ability of NELL-1 to direct BMP2-treated cells toward osteogenesis and away from adipogenesis requires intact canonical Wnt signaling. Overall, these studies establish the feasibility of combining NELL-1 with BMP2 to improve clinical bone regeneration and provide mechanistic insight into canonical Wnt pathway activity during NELL-1 and BMP2 osteogenesis. The novel abilities of NELL-1 to stimulate Wnt signaling and to repress adipogenesis may highlight new treatment approaches for bone loss in osteoporosis. NEL-like molecule-1 (NELL-1) is an osteoinductive growth factor first identified through its overexpression in pathologically fusing suture specimens from patients with craniosynostosis. 1,2 Transgenic Nell1-overexpressing mice recapitulate craniosynostosis-like phenotypes, exhibiting gross calvarial bone overgrowth and increased osteoblast differentiation. 3 Conversely, Nell1 deficiency severely disrupts bone growth, as mice with nonsense mutations in Nell1 die perinatally with major skeletal anomalies in the craniofacial complex, spine, and long bones. 4e6 Highlighting the central role of NELL-1 in skeletal development, NELL-1 mediates key downstream effects of the master osteogenic regulator runt-related transcription factor 2 (RUNX2) 7 and can partially rescue RUNX2 loss of function. 8 NELL-1 can also transiently activate mitogen-activated protein kinase signaling to induce RUNX2 phosphorylation and osteogenic differentiation. 9 Recently, we

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Smad function and intranuclear targeting share a Runx2 motif required for osteogenic lineage induction and BMP2 responsive transcription

Cited by 146 publications

References 44 publications

A microRNA signature for a BMP2-induced osteoblast lineage commitment program

A microRNA signature for a BMP2-induced osteoblast lineage commitment program

Runx2 deficiency and defective subnuclear targeting bypass senescence to promote immortalization and tumorigenic potential

Novel Wnt Regulator NEL-Like Molecule-1 Antagonizes Adipogenesis and Augments Osteogenesis Induced by Bone Morphogenetic Protein 2

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