Inhibitor of DNA binding/differentiation helix-loop-helix proteins mediate bone morphogenetic protein-induced osteoblast differentiation of mesenchymal stem cells.
Bone morphogenetic proteins (BMPs) belong to the TGF-beta superfamily and play an important role in development and in many cellular processes. We have found that BMP-2, BMP-6, and BMP-9 induce the most potent osteogenic differentiation of mesenchymal stem cells. Expression profiling analysis has revealed that the Inhibitors of DNA binding/differentiation (Id)-1, Id-2, and Id-3 are among the most significantly up-regulated genes upon BMP-2, BMP-6, or BMP-9 stimulation. Here, we sought to determine the functional role of these Id proteins in BMP-induced osteoblast differentiation. We demonstrated that the expression of Id-1, Id-2, and Id-3 genes was significantly induced at the early stage of BMP-9 stimulation and returned to basal levels at 3 days after stimulation. RNA interference-mediated knockdown of Id expression significantly diminished the BMP-9-induced osteogenic differentiation of mesenchymal progenitor cells. Surprisingly, a constitutive overexpression of these Id genes also inhibited osteoblast differentiation initiated by BMP-9. Furthermore, we demonstrated that BMP-9-regulated Id expression is Smad4-dependent. Overexpression of the three Id genes was shown to promote cell proliferation that was coupled with an inhibition of osteogenic differentiation. Thus, our findings suggest that the Id helix-loop-helix proteins may play an important role in promoting the proliferation of early osteoblast progenitor cells and that Id expression must be down-regulated during the terminal differentiation of committed osteoblasts, suggesting that a balanced regulation of Id expression may be critical to BMP-induced osteoblast lineage-specific differentiation of mesenchymal stem cells.
Peng
Ying
Y
Molecular Oncology Laboratory, Department of Surgery, and Committe on Genetics, University of Chicago, IL 60637, USA.
Kang
Quan
Q
Luo
Qing
Q
Jiang
Wei
W
Si
Weike
W
Liu
Bernard A
BA
Luu
Hue H
HH
Park
Jong Kyung
JK
Li
Xinmin
X
Luo
Jeffrey
J
Montag
Anthony G
AG
Haydon
Rex C
RC
He
Tong-Chuan
TC
D000256:Adenoviridae / Q000235:genetics; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D055396:Bone Morphogenetic Protein 2; D055418:Bone Morphogenetic Protein 6; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D002454:Cell Differentiation; D002455:Cell Division; D002460:Cell Line; D019070:Cell Lineage; D002478:Cells, Cultured; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D020868:Gene Silencing; D055427:Growth Differentiation Factor 2; D051379:Mice; D008809:Mice, Inbred C3H; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D020411:Oligonucleotide Array Sequence Analysis; D010006:Osteoblasts / Q000378:metabolism*; D011485:Protein Binding; D012313:RNA / Q000378:metabolism; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051901:Smad4 Protein; D013234:Stem Cells / Q000378:metabolism; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism; D016212:Transforming Growth Factor beta; D015854:Up-Regulation
C525719:Bmp2 protein, mouse; C525817:Bmp6 protein, mouse; D055396:Bone Morphogenetic Protein 2; D055418:Bone Morphogenetic Protein 6; D019485:Bone Morphogenetic Proteins; D004268:DNA-Binding Proteins; C526108:Gdf2 protein, mouse; D055427:Growth Differentiation Factor 2; D051901:Smad4 Protein; C490810:Smad4 protein, mouse; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D012313:RNA; D004247:DNA; D000469:Alkaline Phosphatase