| Budget Amount *help |
¥3,910,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥510,000)
Fiscal Year 2007: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000)
Fiscal Year 2006: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
The Notch signaling pathway plays a crucial role in specifying cellular fates by interaction between cellular neighbors; however, the molecular mechanism underlying smooth muscle cell (SMC) differentiation by Notch signaling has not been well characterized. Here we demonstrate that Jagged1-Notch signaling promotes SMC differentiation from mesenchymal cells. Overexpression of the Notch intracellular domain (NICD), an activated form of Notch, upregulates the expression of multiple SMC marker genes including SMC-myosin heavy chain (SM-MHC) in mesenchymal 10T1/2 cells, but not in non-mesenchymal cells. Physiological Notch stimulation by its ligand Jagged1, but not Dll4, directly induces SM-MHC expression in 10T1/2 cells without de novo protein synthesis, indicative of a ligand-selective effect. Jagged1-induced expression of SM-MHC was blocked by γ-secretase inhibitor, DAPT, which impedes Notch signaling. Using RBP-Jκ-deficient cells and site-specific mutagenesis of the SM-MHC gene, we show that such an induction is independent of the myocardin/serum response factor/CArG complex, but absolutely dependent on RBP-Jκ, a major mediator of Notch signaling, and its cognate binding sequence. Of importance, Notch signaling and myocardin synergistically activate SM-MHC gene expression. Taken together, these data suggest that the Jagged1-Notch pathway constitutes an instructive signal for SMC differentiation through an RBP-Jκ-dependent mechanism and augments gene expression mediated by myocardin/SRF/CArG complex. Given that Notch pathway components are expressed in vascular SMC during normal development and disease, Notch signaling is likely to play a pivotal role in such situations to modulate the VSMC phenotype.
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