The Role of Liver-Specific Transcription Factor HNF4 in Reprogramming of Fibroblasts

  • Mary Odubote

Student thesis: Master's ThesisMaster of Science (MS)

Abstract

The mammalian liver, a vital organ with complex functions, relies on a network of transcription factors to regulate gene expression. Fusion of hepatoma cells with fibroblasts often leads to gene extinction, silencing approximately 400 liver-enriched genes, including critical transcription factors such as HNF4. Previous studies revealed that ectopic expression of HNF4 in fibroblasts failed to prevent the extinction of SERPINA1, a liver-specific gene, upon subsequent fusion with hepatoma cells. Here, we sought to investigate the extent to which ectopic expression of HNF4 can reprogram fibroblast cells and prevent gene extinction in hybrid cells.

Using whole-genome expression analysis, we compared RAT1 fibroblasts with RAT1 cells expressing ectopic HNF4 (Rn16 cells) and evaluated their extinction profiles upon fusion with hepatoma cells. Results revealed that HNF4 expression activated 394 genes (>2.5-fold), with 73 (20%) classified as liver-enriched. Promoter analysis identified only 9 (12%) liver-enriched genes with direct HNF4 binding sites, highlighting the limited scope of HNF4-mediated activation. Upon fusion of Rn16 cells with hepatoma cells, 529 genes were repressed, a higher number compared to the 355 genes repressed in RAT1-hepatoma hybrids. Notably, all HNF4 and HNF1α target genes activated in Rn16 cells were silenced in the resulting hybrids, indicating that the gene extinction process overrides transcription factor activity.

This study underscores the challenges of reprogramming fibroblasts into hepatocyte-like cells and highlights the dominance of gene extinction mechanisms in hybrid cells. Further analyses are underway to uncover the regulatory networks driving these changes and to explore strategies to enhance the stability and efficacy of liver-specific reprogramming. These findings have significant implications for regenerative medicine, disease modeling, and therapeutic applications.
Date of Award2024
Original languageAmerican English
Awarding Institution
  • Eastern Illinois University
SupervisorGary A. Bulla (Supervisor)

ASJC Scopus Subject Areas

  • Cell Biology

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