PgmNr Z6114: MicroRNA regulation of BMP signaling and its effects on vascular smooth muscle cells.

Authors:
C. G. Watterston; L. Zeng; A. Onabadejo; S. J. Childs


Institutes
University of Calgary, Calgary, Alberta, CA.


Abstract:

Stroke is the third leading cause of death in North America and hemorrhagic stroke accounts for 12% of all stroke. As blood vessels develop it is essential that they are physically supported to ensure to supply blood to peripheral tissues. Vascular smooth muscle cells (vSMC) support the endothelial lining of blood vessels and can switch their phenotypic expressions from contractile (differentiated) to synthetic (undifferentiated). Synthetic vSMCs cannot properly support blood vessels the effects of which can lead to uncontrolled bleeding (hemorrhage). We aim to uncover the relationship between microRNAs (miRNAs) and their target genes using a zebrafish model in vascular stabilization. microRNA26 (miR26) targets smad1 downstream of BMP signaling in vitro.We show that knockdown of miR26 leads to brain hemorrhage in developing zebrafish and that Smad1 is upregulated. Concomitantly overexpression of miR26 leads to decreased Smad1.Overexpression of Smad1 in wild type fish also leads to hemorrhage and double knockdown of miR26 and Smad1 rescues loss of miR26, suggesting that miR26 mediates vascular stabilization via targeting of Smad1. We observe increased pSmad1/5/8 suggesting increased activation of the BMP pathway. A range of other phenotypes are also observed suggesting alterations in the BMP pathway including axial patterning defects.miR26 is expressed in the vicinity of brain blood vessels and loss or gain of miR26 leads to alterations in genes critical for vascular mural cell development including pdgfrβ, acta2, and nmhc-b. We also show decreased acta2 positive cell coverage of blood vessels in miR26 knockdown embryos.To test the role of BMP in vascular smooth muscle development, we applied the BMP receptor kinase inhibitor DMH1 to wild type and miR26 knockdown. DMH1 treatment leads to a reduction in acta2 positive smooth muscle cells in wild type embryos. DMH1is unable to rescue loss of miR26, which is expected if increased Smad1 resulting from miR26 knockdown is unable to be phosphorylated by the BMP receptor.Taken together our results indicate that both loss and gain of pSmad1 leads to defects in vascular smooth muscle differentiation in vivo, and that miR26 controls this fine balance to promote vascular maturation.



ZFIN Genetics Index
1. miR26a
2. smad1
3. acta2
4. pdgfrb
5. nmhc-b
6. bmp