Critical regulation of bone morphogenetic protein-induced osteoblastic differentiation by Delta1/Jagged1-activated Notch1 signaling.
Functional involvement of the Notch pathway in osteoblastic differentiation has been previously investigated using the truncated intracellular domain, which mimics Notch signaling by interacting with the DNA-binding protein CBF-1. However, it is unclear whether Notch ligands Delta1 and Jagged1 also induce an identical cellular response in osteoblastic differentiation. We have shown that both Delta1 and Jagged1 were expressed concomitantly with Notch1 in maturating osteoblastic cells during bone regeneration and that overexpressed and immobilized recombinant Delta1 and Jagged1 alone did not alter the differentiated state of MC3T3-E1 and C2C12 cells. However, they augmented bone morphogenetic protein-2 (BMP2)-induced alkaline phosphatase activity and the expression of several differentiation markers, except for osteocalcin, and ultimately enhanced calcified nodule and in vivo ectopic bone formation of MC3T3-E1. In addition, both ligands transmitted signal through the CBF-1-dependent pathway and stimulated the expression of HES-1, a direct target of Notch pathway. To test the necessity of Notch signaling in BMP2-induced differentiation, Notch signaling was inhibited by the dominant negative extracellular domain of Notch1, specific inhibitor, or small interference RNA. These treatments decreased alkaline phosphatase activity as well as the expression of other differentiation markers and inhibited the promoter activity of Id-1, a target gene of the BMP pathway. These results indicate the functional redundancy between Delta1 and Jagged1 in osteoblastic differentiation whereby Delta1/Jagged1-activated Notch1 enhances BMP2-induced differentiation through the identical signaling pathway. Furthermore, our data also suggest that functional Notch signaling is essential not only for BMP2-induced osteoblast differentiation but also for BMP signaling itself.
Nobta
Masuhiro
M
Divisions of Orthopaedic Pathomechanism, Department of Developmental and Reconstructive Medicine, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki 852-8588, Japan.
Tsukazaki
Tomoo
T
Shibata
Yasuaki
Y
Xin
Chang
C
Moriishi
Takeshi
T
Sakano
Seiji
S
Shindo
Hiroyuki
H
Yamaguchi
Akira
A
D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D001861:Bone Regeneration / Q000502:physiology; D002135:Calcium-Binding Proteins; D002454:Cell Differentiation / Q000502:physiology*; D036341:Intercellular Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins; D000072100:Jagged-1 Protein; D008024:Ligands; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D010006:Osteoblasts / Q000166:cytology / Q000502:physiology*; D015675:Osteocalcin / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D034741:RNA, Small Interfering; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000072099:Serrate-Jagged Proteins; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
D019485:Bone Morphogenetic Proteins; D002135:Calcium-Binding Proteins; D036341:Intercellular Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins; C000606274:Jag1 protein, mouse; D000072100:Jagged-1 Protein; D008024:Ligands; D008565:Membrane Proteins; C497762:Notch1 protein, mouse; D011506:Proteins; D034741:RNA, Small Interfering; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface; D000072099:Serrate-Jagged Proteins; D014157:Transcription Factors; C064045:delta protein; D015675:Osteocalcin; D000469:Alkaline Phosphatase