Catherine Demos
BME PhD Defense Presentation

Date:2022-06-08
Time: 11:00 am
Location / Meeting Link: HSRB E-160 / https://emory.zoom.us/j/91726201776

Committee Members:
Dr. Hanjoong Jo (Advisor), Dr. James Dahlman, Dr. Wilbur Lam, Dr. Yuhong Fan, Dr. Changwon Park


Title: Identification of Novel Flow Sensitive Transcription Factors in the Endothelium and Their Role in Atherosclerosis

Abstract:
Atherosclerosis is a chronic inflammatory disease wherein disturbed blood flow induces endothelial dysfunction, inflammation, and plaque accumulation in arterial walls by regulating endothelial gene expression. While Kruppel-like factor (KLF) -2 and KLF4 are known to play a dominant role in flow sensitive gene expression, the role for additional flow sensitive transcription factors remains understudied. Here we tested the hypothesis that there are other flow sensitive transcription factors that play an important role in endothelial function. We identified 30 potential novel flow sensitive transcription factors in arterial endothelial cells in vivo by reanalyzing gene array and single-cell RNAseq datasets using our mouse partial carotid ligation model. These transcription factors were further validated in vivo and in vitro using mice and human aortic endothelial cells (HAECs) at the mRNA and protein levels. From this study we identified seven flow sensitive transcription factors (KLF2, KLF4, SOX4, SOX13, SIX2, ZBTB46, and NFIL3) that are conserved in human and mice in vivo and in vitro. Of these, we selected SOX13 for further studies because of its robust flow sensitivity and its unknown endothelial function. We found that siRNA-mediated knockdown of SOX13 reduced anti-inflammatory function of endothelial cells in response to the anti-atherogenic flow condition ULS (unidirectional high laminar shear stress) as determined by monocyte adhesion and vascular cell adhesion molecule (VCAM1) expression. To define the underlying mechanisms, we carried out RNAsequencing in HAECs treated with SOX13 siRNA and shear stress. We found that 94 genes were downregulated and 40 genes were upregulated in response to shear stress in a SOX13-dependent manner. Interestingly, several chemokines and cytokines including CXCL10, CXCL1, CXCL8, CSF3, CCL2 and CCL5 were the major genes regulated by SOX13 and ULS. These were further validated by qPCR and ELISA. Additionally, both overexpression of SOX13 and treatment with Met-CCL5, a CCL5 antagonist that does not activate immune cell adhesion, prevented siSOX13-driven inflammation. CCL5 and CXCL10 have been independently linked to cardiovascular disease, but induction by loss of SOX13 has not been reported before this study. Taken together, these data show that SOX13 is a novel flow sensitive transcription factor regulating endothelial inflammation, a major flow-dependent proatherogenic pathway.