DLK1/FA1 (delta-like 1/fetal antigen-1) is a negative regulator of bone mass that acts to inhibit osteoblast differentiation and stimulate osteoclast differentiation. However, the molecular mechanisms underlying these effects are not known. Thus, we studied the effect of DLK1/FA1 on different osteogenic factors-induced osteoblast differentiation. We identified DLK1/FA1 as an inhibitor of BMP2-induced osteogenesis in mouse myoblast C2C12 cells. Stable overexpression of DLK1/FA1 in C2C12 cells or the addition of its soluble form protein FA1 significantly inhibited BMP2-induced osteogenesis as assessed by reduced Alp activity and osteogenic gene expression including Alp, Col1a1, Runx2 and Bglap. In addition, DLK1/FA1 inhibited BMP signaling as demonstrated by reduced gene expression of BMP-responsive genes: Junb and Id1, reduced BMP2 induced luciferase activity in C2C12 BMP luciferase reporter cells, and reduced BMP2-induced Smad1/5/8 phosphorylation by western blot. Follow up studies revealed that DLK1/FA1 affected the expression of many components involved in BMP pathway including both positive (Bmpr1a, Bmpr1b, Bmpr2 and Smad4) and negative (Smad6,Smad7, Smur1 and Smurf2) regulators. Besides, we observed that DLK1/FA1 induced strong NFκB activity evidenced by NFκB responsive luciferase reporter assay and real-time RT-PCR analysis of NFκB target genes. The inhibitory effect of NFκB signaling on BMP signaling was confirmed by luciferase assay in C2C12 BMP luciferase reporter cells. In conclusion, we propose a novel mechanism where DLK1/FA1 inhibits BMP2 induced osteoblast differentiation by inhibiting BMP signaling directly through regulation of BMP components and indirectly through modulation of NFκB signaling. Our results provide new insight into molecular control of DLK1 on osteoblast differentiation and possibly on bone formation.
|Status||Udgivet - 2016|
|Begivenhed||43rd Annual European Calcified Tissue Society Congress - Rome , Italien|
Varighed: 14. maj 2016 → 17. maj 2016
|Konference||43rd Annual European Calcified Tissue Society Congress|
|Periode||14/05/2016 → 17/05/2016|
Qiu, W., Abdallah, B., & Kassem, M. (2016). Delta-like 1/fetal antigen 1(DLK1/FA1) inhibits BMP2 induced osteoblast differentiation through modulation of NFκB signaling pathway: a novel mechanism for effects on skeletal homeostasis. Poster session præsenteret på 43rd Annual European Calcified Tissue Society Congress, Rome , Italien. https://doi.org/10.1530/boneabs.5.P137