Homeobox D3, A Novel Link Between Bone Morphogenetic Protein 9 and Transforming Growth Factor Beta 1 Signaling.
AIMS
Several signaling pathways contribute to endothelial-mesenchymal transitions and vascular calcification, including bone morphogenetic protein (BMP) and transforming growth factor (TGF) β signaling. The transcription factor homeobox D3 (Hoxd3) is known to regulate an invasive endothelial phenotype, and the aim of the study is to determine if HOXD3 modulates BMP and TGFβ signaling in the endothelium.


METHODS AND RESEARCH
We report that the endothelium with high BMP activity due to the loss of BMP inhibitor matrix Gla protein (MGP) shows induction of Hoxd3. HOXD3 is part of a BMP-triggered cascade. When activated by BMP9, activin receptor-like kinase (ALK) 1 induces HOXD3 expression. Hoxd3 promoter is a direct target of phosphorylated (p) SMAD1, a mediator of BMP signaling. High BMP activity further results in enhanced TGFβ signaling due to induction of TGFβ1 and its receptor, ALK5. This is mediated by HOXD3, which directly targets the Tgfb1 promoter. Finally, TGFβ1 and BMP9 stimulate the expression of MGP, which limits the enhanced ALK1 induction by counteracting BMP4. The cascade of BMP9-HOXD3-TGFβ also affects Notch signaling and angiogenesis through induction of Notch ligand Jagged 2 and suppression of Notch ligand delta-like 4 (Dll4).


CONCLUSION
The results suggest that HOXD3 is a novel link between BMP9/ALK1 and TGFβ1/ALK5 signaling.


TRANSLATIONAL PERSPECTIVE
BMP and TGFβ signaling are instrumental in vascular disease such as vascular calcification and atherosclerosis. This study demonstrated a novel type of cross talk between endothelial BMP and TGFβ signaling as mediated by HOXD3. The results provide a possible therapeutic approach to control dysfunctional BMP and TGFβ signaling by regulating HOXD3.
['Wang|Lumin|L|', 'Yao|Jiayi|J|', 'Yu|Tongtong|T|', 'Zhang|Daoqin|D|', 'Qiao|Xiaojing|X|', 'Yao|Zehao|Z|', 'Wu|Xiuju|X|', 'Zhang|Li|L|', 'Boström|Kristina I|KI|', 'Yao|Yucheng|Y|']
D030301:Activin Receptors, Type II D000818:Animals D004268:DNA-Binding Proteins D004730:Endothelium, Vascular D005786:Gene Expression Regulation D055427:Growth Differentiation Factor 2 D061307:Human Umbilical Vein Endothelial Cells D006801:Humans D051379:Mice D008810:Mice, Inbred C57BL D018345:Mice, Knockout D018919:Neovascularization, Physiologic D010766:Phosphorylation D011506:Proteins D051880:Receptors, Notch D015398:Signal Transduction D053773:Transforming Growth Factor beta1
bone morphogenetic protein endothelium Notch activin receptor-like kinase 1 vascular development