Abstract 19233: C-myb Regulates Microrna143 and Microrna145 Gene Expression in Embryonic and Adult Vascular Smooth Muscle Cells
Background: MicroRNAs (miR) are small non-coding RNAs. The bicistronic miR-143/145 gene determines cell fate of cardiomyocytes, vascular smooth muscle cells (VSMC) and endothelial cells. The regulation of miR-143/145 remains unclear. Transcription factor c-Myb controls proliferation and differentiation of hematopoiesis progenitors and VSMC.
Hypothesis: c-Myb regulates miR-143/145 expression in VSMC proliferation and differentiation.
Methods & Results: Flow cytometry of d3.75 mouse embryoid bodies (EBs) was used to isolate SMC progenitors with surface markers VEGFR2 (V) and PDGFRα (P). In c-myb knockout EB, V+/P- and V-/P+ progenitor cells had low expression of miR-143/145 suggesting a role for c-Myb in their regulation. Primary carotid VSMC isolated from mice with diminished expression of c-Myb (LoxP) treated with TGFβ have reduced expression of miR-143 and miR-145. Sequence alignment identified c-Myb-binding sites (MBS) in the promoter of the miR-143/145 gene. ChIP assays in EBs and adult VSMC revealed c-Myb binding to MBS. Using site-directed mutagenesis in a promoter-reporter construct, we identified MBS mediate transcriptional regulation of miR-143/145 in VSMC. Immunoblots were used to test whether c-Myb regulated a known target of miR-143, the ETS domain-containing protein-1 (Elk-1). Increased levels of c-Myb inversely correlated with Elk-1, suggesting c-Myb represses Elk-1. This effect was abrogated by miR-143 antagomir, and enhanced by miR-143 mimic.
Conclusion: c-Myb regulates miR-143/145 expression in differentiating embryonic SMC progenitors and TGFβ-stimulated adult VSMC via MBS in the miR-143/145 promoter.
Author Disclosures: M. Chandy: None. M. Ishida: None. E. Shikatani: None. O. El-Mouranyi: None. T. Alfrooze: None. M. Husain: None.
- © 2016 by American Heart Association, Inc.