Recent Publications from Jon Brown Lab
Work from Jon Brown Lab has recently been published in JCI Insight, JACC:BTS and Proceedings of the National Academy of Sciences.
COMPARATIVE TRANSCRIPTOMICS OF EX VIVO, PATIENT-DERIVED ENDOTHELIAL CELLS REVEALS NOVEL PATHWAYS ASSOCIATED WITH TYPE 2 DIABETES MELLITUS
JACC: Basic to Translational Science, September 23, 2019
In this study we used low-input RNA-sequencing to annotate the molecular identity of human endothelial cells (ECs) isolated and immunopurified with CD144 microbeads. After validating this technique, comparative gene expression profiling of ECs from healthy subjects and patients with type 2 diabetes mellitus identified both known and novel pathways linked with EC dysfunction. Modeling of diabetes by treating cultured ECs with high glucose identified shared changes in gene expression in diabetic cells. Overall, the data demonstrate how purified ECs from patients can be used to generate new hypotheses about mechanisms of human vascular disease.
IMAGING MASS SPECTROMETRY REVEALS HETEROGENEITY OF PROLIFERATION AND METABOLISM IN ATHEROSCLEROSIS
JCI Insight, June 6th, 2019
Atherosclerotic plaques feature local proliferation of leukocytes and vascular smooth muscle cells (VSMCs) and changes in cellular metabolism. We used Multi-isotope Imaging Mass spectrometry (MIMS), a quantitative imaging platform, to measure coincident cell division and glucose utilization at suborganelle resolution in atherosclerotic plaques. In established plaques, 65% of intimal foam cells but only 4% of medial VSMCs were labeled with 15N-thymidine after 1 week of isotope treatment. Dividing cells demonstrated heightened glucose labeling. MIMS detected 2H-glucose label in multiple subcellular compartments within foam cells including lipid droplets, the cytosol and chromatin. Unexpectedly, we identified an intensely focal region of 2H-label in VSMCs underlying plaques. This signal diminished in regions of aorta without atherosclerosis. In advanced plaques, 15N-thymidine and 2H-glucose labeling in foam cells and VSMCs significantly decreased. These data demonstrate marked heterogeneity in VSMC glucose metabolism that was dependent on both proliferative status and proximity of VSMCs to plaques. These results reveal how quantitative mass spectrometry coupled with isotope imaging can complement other methods used to study cell biology directly in the growing atherosclerotic plaque in vivo.
BET BROMODOMAIN PROTEINS REGULATE ENHANCER FUNCTION DURING ADIPOGENESIS
PNAS, February 14th, 2018
Transcriptional cascades orchestrate activation of the adipocyte gene expression program during adipogenesis. However, the coactivators controlling expression of PPARg and C/EBPa are less well characterized. In this work we demonstrated that BRD4 regulates transcription of PPARg and C/EBPa. During adipogenesis in 3T3L1 cells BRD4 dynamically redistributes to de novo super enhancers that are in close proximity to key genes controlling adipocyte differentiation. BET bromodomain inhibition impedes BRD4 occupancy at these new enhancer regions and thereby disrupts transcription of Pparg and Cebpa,. As a result, adipogenesis is blocked. Furthermore, silencing of super enhancer sites at the Pparg locus by CRISPR-interference inhibits gene expression, demonstrating a functional role for these enhancers in Pparg gene expression and adipogenesis. Together, these data establish BETs and BRD4 as time- and context-dependent coactivators of the adipocyte cell state transition.
Jon Brown Lab | VUMC