Abstract 1: Oct4 is Re-activated in Smooth Muscle Cells through KLF4/Hif1α and Hydroxymethylation Mechanisms and Plays a Critical Role in Atherogenesis
The pluripotency factor Oct4 is a protein that regulates embryonic stem cell (ESC) totipotency and is the only gene thought to be indispensable for production of induced pluripotent stem (iPS) cells. Although there is evidence that Oct4 may be expressed in non-ESC, this is controversial and as yet there is no direct evidence that Oct4 plays a functional role within somatic cells.
We demonstrate that Oct4 is markedly induced in cells within atherosclerotic lesions from ApoE-/- mice fed a high-fat diet and within human coronary artery atherosclerotic lesions. We show that smooth muscle cell (SMC)-specific conditional knockout (KO) of Oct4 within Western diet-fed ApoE-/- mice resulted in increased atherosclerotic lesion size and other changes consistent with decreased plaque stability. Moreover, using a novel SMC lineage tracing mouse developed in our lab, we also show that lesions from SMC-specific conditional Oct4 KO mice contained far fewer de-differentiated (Acta2-) SMCs likely as the result of impaired SMC de-differentiation and migration from the media into the intima and not to altered proliferation or apoptosis. Further mechanistic studies using in vitro and in vivo Chromatin Immunoprecipitation assays, glycosylation-coupled methylation sensitive qPCR and hMeDIP show that activation of Oct4 within SMCs and within atherosclerotic lsions was associated with hydroxymethylation of the Oct4 promoter and was Klf4- and Hif1α-dependent. In addition, using in situ hybridization/proximity ligation (ISH-PLA) assay developed in our lab we showed hydroxymethylation of the Oct4 promoter within individual SMC-derived cells in atherosclerotic lesions of our SMC-lineage tracing ApoE-/- mice. These results are the first to show that Oct4 plays a direct functional role in regulating phenotypic transitions in somatic cells, and provide molecular mechanisms required for Oct4 re-activation.
Author Disclosures: O.A. Cherepanova: None. D. Gomez: None. L.S. Shankman: None. J. Williams: None. Y. Geng: None. J.J. Connelly: None. G.K. Owens: None.
This research has received full or partial funding support from the American Heart Association.
- © 2015 by American Heart Association, Inc.