Project description:Spontaneous cellular reprogramming is rare, but has been observed in adult cells. This is most evident in the mammalian liver, where hepatocytes undergo physiological reprogramming to generate functional biliary epithelial cells (BECs) in response to injury. The underlying mechanisms driving this cell fate switch remain unclear, however. Here, we characterize epigenetic changes occurring during this transition at the single cell level, and show that reprogramming occurs synchronously and deterministically, though reprogrammed cells retain epigenetic hepatocyte memory. An in vivo CRISPR screen reveals the histone acetyltransferase-HBO1 functions as a critical barrier to hepatocyte reprogramming via acetylation of H3K14. HBO1 depletion accelerates BEC-specific chromatin remodeling and allows for the full resolution of the hepatocyte chromatin landscape. Mechanistically, HBO1 is recruited by the YAP to TEAD target sites to negatively its modulate chromatin-accessibility, DNA-binding, and transcriptional-output, thus acting as an epigenetic brake for YAP/TEAD function. Our work here delineates epigenetic trajectories of a physiological reprogramming process and identifies HBO1 as potential target for hepatocyte trans-differentiation therapeutic strategies.
Project description:Expression profiling of hepatocytes-derived ductal cells with properties intermediate between mature hepatocytes and cholangiocytes. Chimeric adult mice were generated where mature hepatocytes were marked with a fluorescent red marker. Chronic injury was induced for ~6weeks and three cell types were isolated by FACS (Influx, BD) for expression analysis by RNAseq based on cell surface phenotype and origin: hepatocytes (n=3), hepatocyte-derived oval cells (1c3+, n=5), and cholangiocyte-derived oval cells (1c3+, n=5).
Project description:PR-SET7-mediated histone-4 lysine-20 methylation has been implicated in mitotic condensation, DNA damage response and replication licencing. Here we show that PR-SET7 function in the liver is pivotal for maintaining genome integrity. Hepatocyte-specific deletion of PR-SET7 in mouse embryos resulted in G2 arrest followed by massive cell death and defect in liver organogenesis. Inactivation at postnatal stages caused cell duplication-dependent hepatocyte necrosis with unusual features of autophagy, termed "endonucleosis". Necrotic death was accompanied by inflammation, fibrosis and compensatory growth induction of neighboring hepatocytes and resident ductal progenitor cells. Prolonged necrotic-regenerative cycles coupled with oncogenic STAT3 activation replaced pre-existing hepatocytes with hepatocellular carcinoma derived entirely from ductal progenitor cells. Hepatocellular carcinoma in these mice displays a cancer stem cell gene signature specified by the co-expression of ductal progenitor markers and oncofetal genes. Mice carrying hepatocyte specific inactivation of PR-SET7 were generated in order to investigate the function of PR-SET7 histone methyl transferase in liver organogenesis, hepatocyte proliferation and liver regeneration. P15 WT mice were injected intra-peritoneally (ip) with 25ml per kg DEN (diethyl nitrosamine). Mice were examined for RNA expression at 8 months old.
Project description:Backgruound and aims: Loss of hepatocyte identity is associated with impaired liver function in alcohol-related hepatitis (AH). However, the mechanisms and the impact of hepatocyte reprogramming in liver disease are poorly understood. Here we show that both hepatocytes expressing KRT7 (hepatobiliary (HB) cells) and ductular reaction cells were increased in decompensated cirrhotic patients and AH, but only HB cells correlated with poor liver function, reduced liver synthetic capacity and poor outcome. Transcriptomic analysis of microdissected HB cells revealed the expression of biliary-specific genes and a mild reduction of hepatocyte metabolism. Functional analysis identified pathways involved in hepatocyte reprogramming together with inflammatory, stemness and cancer gene programs. In this context, CXCR4 pathway was highly enriched in HB cells, and CXCR4 correlated with disease severity and reduced expression of hepatocyte transcription factors and albumin. Mechanistically, TGFβ induced the expression of CXCR4 in primary hepatocytes, and its ligand CXCL12 promoted hepatocyte reprogramming. Liver overexpression of CXCR4 in chronic liver injury decreased hepatocyte gene expression and promoted liver injury. Pharmacological inhibition of CXCR4 reverted hepatocyte loss of identity and reduced ductular reaction and fibrosis progression. Conclusions: This study shows the association of hepatocyte reprogramming with disease progression and poor outcome in AH. Moreover, we identify CXCR4 as a driver of hepatocyte reprogramming as well as a potential therapeutic target in chronic liver injury.
Project description:We used ChIP-seq technology in order to map chromatin binding sites of the HBO1 MYST complex in the RKO cell line. We obtained a significant enrichment of the HBO1 signal right after TSS regions of genes and also In the proximal promoter region, with no signal on TSS. This enrichment also correlates with gene expression level. HBO1 signal in RKO cell line.
Project description:We find that 499 genes are up-regulated and 457 are down-regulated in response to over-expression of JADE1, while 397 genes are up-regulated and 385 are down-regulated after HBO1 knock-down. For each condition - HBO1 siRNA treatment or JADE1 over-expression - two biological replicates were analyzed in duplicate.
Project description:Lysine benzoylation (Kbz) is a newly discovered protein post-translational modification (PTM). This PTM can be stimulated by benzoate and contributes to gene expression. However, its regulatory enzymes and substrate proteins remain largely unknown, hindering further functional studies. Here we identified and validated the lysine acetyltransferase (KAT) HBO1 as a “writer” of Kbz in mammalian cells. In addition, we report the first benzoylome in mammalian cells, identifying 1747 Kbz sites, among them at least 77 are the HBO1-targeted Kbz substrates. Bioinformatics analysis showed that HBO1-targeted Kbz sites were involved in multiple processes, including chromatin remodeling, transcription regulation, immune regulation, and tumor growth. Our results thus identify key regulatory elements of the Kbz pathway, and reveal new enzymatic activity and functions of HBO1 in cellular physiology.
Project description:The liver is a pivotal organ possessing remarkable regenerative capacity. By employing murine liver injury models and lineage tracing strategy, recent studies have demonstrated that differentiated hepatocytes undergo reprogramming to SOX9+HNF4α+ liver progenitor-like cells (LPLCs), and serve as a totally new cell source for mammalian liver regeneration. However, it is largely unknown how hepatocyte reprogramming is regulated. In this study, we focus on analyzing the microenvironment cues in triggering hepatocyte reprogramming in liver injuries. By performing single-cell RNA sequencing (scRNA-seq) of hepatocyte reprogramming in liver injury, we find immune response is significantly activated. Notably, by lineage depletion, macrophages, especially kupffer cells, but not T cells, B cells, natural killer cells or neutrophils, are found essential for hepatocyte reprogramming and liver regeneration. IL-6, derived specifically from activated kupffer cells, triggers hepatocyte reprogramming via gp130/STAT3 signaling. Furthermore, STAT3 triggers gene expression by binding to Arid1a-dependent pre-opened regeneration-responsive enhancers (RREs) of reprogramming genes. Collectively, this study provides key insights into kupffer cells/IL-6/STAT3-mediated hepatocyte reprogramming and liver regeneration, which may serve as the base for new therapeutic strategies in facilitating endogenous repair mechanisms.
Project description:The liver is a pivotal organ possessing remarkable regenerative capacity. By employing murine liver injury models and lineage tracing strategy, recent studies have demonstrated that differentiated hepatocytes undergo reprogramming to SOX9+HNF4α+ liver progenitor-like cells (LPLCs), and serve as a totally new cell source for mammalian liver regeneration. However, it is largely unknown how hepatocyte reprogramming is regulated. In this study, we focus on analyzing the microenvironment cues in triggering hepatocyte reprogramming in liver injuries. By performing single-cell RNA sequencing (scRNA-seq) of hepatocyte reprogramming in liver injury, we find immune response is significantly activated. Notably, by lineage depletion, macrophages, especially kupffer cells, but not T cells, B cells, natural killer cells or neutrophils, are found essential for hepatocyte reprogramming and liver regeneration. IL-6, derived specifically from activated kupffer cells, triggers hepatocyte reprogramming via gp130/STAT3 signaling. Furthermore, STAT3 triggers gene expression by binding to Arid1a-dependent pre-opened regeneration-responsive enhancers (RREs) of reprogramming genes. Collectively, this study provides key insights into kupffer cells/IL-6/STAT3-mediated hepatocyte reprogramming and liver regeneration, which may serve as the base for new therapeutic strategies in facilitating endogenous repair mechanisms.
Project description:PR-SET7-mediated histone-4 lysine-20 methylation has been implicated in mitotic condensation, DNA damage response and replication licencing. Here we show that PR-SET7 function in the liver is pivotal for maintaining genome integrity. Hepatocyte-specific deletion of PR-SET7 in mouse embryos resulted in G2 arrest followed by massive cell death and defect in liver organogenesis. Inactivation at postnatal stages caused cell duplication-dependent hepatocyte necrosis with unusual features of autophagy, termed "endonucleosis". Necrotic death was accompanied by inflammation, fibrosis and compensatory growth induction of neighboring hepatocytes and resident ductal progenitor cells. Prolonged necrotic-regenerative cycles coupled with oncogenic STAT3 activation replaced pre-existing hepatocytes with hepatocellular carcinoma derived entirely from ductal progenitor cells. Hepatocellular carcinoma in these mice displays a cancer stem cell gene signature specified by the co-expression of ductal progenitor markers and oncofetal genes.