Date of Graduation
Genes and Development
Doctor of Philosophy (PhD)
Michelle C. Barton, PhD
Joya Chandra, PhD
Nancy Jenkins, PhD
Guillermina Lozano, PhD
Stephanie Watowich, PhD
DISSECTING THE ROLES OF TRIM24 IN REGULATION OF HEPATIC LIPID
METABOLISM AND INFLAMMATION
Lindsey Cauthen Minter, B.S., B.A.
Advisory Professor: Michelle C. Barton, Ph.D.
In this dissertation, I report the characterization of a new mouse model that recapitulates development of hepatocellular carcinoma (HCC) following spontaneous hepatic lipid accumulation, inflammation, and damage of liver tissue, due to complete loss of Trim24 expression. In human HCC and other cancers, TRIM24 expression is aberrantly high, while deletion of TRIM24 in the mouse has been shown to act as a liver specific tumor suppressor. The hypothesis tested here was that TRIM24, the E3 ubiquitin ligase of p53, regulates genes that impact hepatic lipid inflammation and metabolism. I further dissected whether TRIM24 regulates immune cell populations that are commonly misregulated in nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). In the first part of my dissertation, I establish through global gene expression, chromatin enrichment, biochemical, and immunohistochemical analyses that TRIM24 represses hepatic lipid accumulation, inflammation, and fibrosis and damage in the murine liver. In the second part of my thesis, I show that loss of Trim24 leads to increased hepatic macrophage populations and implicates crosstalk with the hematopoietic niche in the bone marrow. Intersections of RNA-seq and TRIM24 ChIP-seq datasets yielded novel gene targets of TRIM24 in mouse liver. Furthermore, I show that TRIM24 is enriched at promoters of genes involved in oxidative stress control, inflammation, and glucose metabolism, all processes that are misregulated in NAFLD and NASH progression. Further, biochemical analyses showed increased glucose metabolism and insulin sensitivity coupled with a decrease in visceral adipose tissue upon loss of Trim24. These findings recapitulate those found in human studies of lean (non-obese) individuals with NAFLD. Thus, this dissertation shows that complete loss of Trim24 offers a model of nonalcoholic fatty liver disease, steatosis, fibrosis and development of hepatocellular carcinoma in the absence of high-fat diet or obesity. In addition, this model offered an opportunity to identify specific immune cell populations, gene targets and metabolic pathways that are regulated by TRIM24.
Trim24, Non-alcoholic fatty liver disease, Non-alcohlic steatohepatitis, Hepatocellular carcinoma, Hepatic lipid metabolism, Inflammation