Reconstitution of Runx2/Cbfa1-null cells identifies a requirement for BMP2 signaling through a Runx2 functional domain during osteoblast differentiation

Bae J.-S.; Gutierrez S. ; Narla R.; Pratap, J; Devados R.; van Wijnen A.J.; Stein J.L.; Stein G.S.; Lian J.B.; Javed, A

Keywords: sequence, acid, proteins, growth, differentiation, induction, mouse, animals, expression, infection, transcription, binding, core, culture, protein, cell, gene, mutant, peptide, nucleus, markers, matrix, alpha, beta, mice, alkaline, embryo, virus, line, transduction, adenovirus, lineage, fragments, subunit, domain, interaction, collagen, osteoblasts, signal, osteopontin, shape, bone, drug, phosphate, article, marker, factor, null, phosphatase, osteocalcin, motifs, analysis, vitamin, function, osteoblast, genetic, glycerol, proteomics, runx2, type, scaffold, adenoviridae, controlled, smad, animal, reverse, knockout, wild, study, 1, amino, priority, nonhuman, journal, Transcription,, 2, biological, Cells,, Cultured, Models,, Ascorbic, Mice,, unclassified, medium, calvaria, carboxy, terminal, Transcriptase, Functional, D, transforming, Mus, morphogenetic, immortalization, sialoprotein, telomerase, Groucho


The Runx2/Cbfa1 transcription factor is a scaffolding protein that promotes osteoblast differentiation; however, the specific Runx2-functional domains required for induction of the osteogenic lineage remain to be identified. We approached this question using a TERT-immortalized cell line derived from calvaria of Runx2-null mice by reconstituting the osteogenic activity with wild-type and deletion mutants of Runx2. The presence or absence of osteogenic media (β-glycerol phosphate and ascorbic acid) and/or with BMP2 did not stimulate osteoblastic gene expression in the Runx2-null cells. However, cells infected with wild-type Runx2 adenovirus showed a robust temporal increase in the expression of osteoblast marker genes and were competent to respond to BMP2. Early markers (i.e., collagen type-1, alkaline phosphatase) were induced (four- to eightfold) at Days 4 and 8 of culture. Genes representing mature osteoblasts (e.g., Runx2, osteopontin, bone sialoprotein, osteocalcin) were temporally expressed and induced from 18-to 36-fold at Days 8 and 12. Interestingly, TGFβ and Vitamin D-mediated transcription of osteoblast genes (except for osteopontin) required the presence of Runx2. Runx2 lacking the C-terminal 96 amino acids (Runx2 Δ432) showed a pattern of gene expression similar to wild-type protein, demonstrating the Groucho interaction and part of the activation domain are dispensable for Runx2 osteogenic activity. Upon further deletion of the Runx2 C-terminus containing the nuclear matrix targeting signal and Smad-interacting domain (Δ391), we find none of the osteoblast markers are expressed. Therefore, the Runx2 391-432 domain is essential for execution of the BMP2 osteogenic signal. © 2006 Wiley-Liss, Inc.

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Título según SCOPUS: Reconstitution of Runx2/Cbfa1-null cells identifies a requirement for BMP2 signaling through a Runx2 functional domain during osteoblast differentiation
Volumen: 100
Número: 2
Editorial: Wiley
Fecha de publicación: 2007
Página de inicio: 434
Página final: 449
Idioma: eng