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Epigenetic Regulation of Cardiac Differentiation of Embryonic Stem Cells and Tissues
Published on: June 3, 2016
Histone signature of metanephric mesenchyme cell lines
Nathan McLaughlin1, Xiao Yao, Yuwen Li
1Department of Pediatrics; The Renal and Hypertension Center of Excellence; Tulane University School of Medicine; New Orleans, LA USA; Department of Biomedical Sciences Program; The Renal and Hypertension Center of Excellence; Tulane University School of Medicine; New Orleans, LA USA.
Abstract:
The metanephric mesenchyme (MM) gives rise to nephrons, the filtering units of the mature kidney. The MM is composed of uninduced (Six2(high)/Lhx1(low)) and induced (Wnt-stimulated, Six2(low)/Lhx1(high)) cells. The global epigenetic state of MM cells is unknown, partly due to technical difficulty in isolating sufficient numbers of homogenous cell populations. We therefore took advantage of two mouse clonal cell lines representing the uninduced (mK3) and induced (mK4) metanephric mesenchyme (based on gene expression profiles and ability to induce branching of ureteric bud). ChIP-Seq revealed that whereas H3K4me3 active region "peaks" are enriched in metabolic genes, H3K27me3 peaks decorate mesenchyme and epithelial cell fate commitment genes. In uninduced mK3 cells, promoters of "stemness" genes (e.g., Six2, Osr1) are enriched with H3K4me3 peaks; these are lost in induced mK4 cells. ChIP-qPCR confirmed this finding and further demonstrated that G9a/H3K9me2 occupy the promoter region of Six2 in induced cells, consistent with the inactive state of transcription. Conversely, genes that mark the induced epithelialized state (e.g., Lhx1, Pax8), transition from a non-permissive to an active chromatin signature in mK3 vs. mK4 cells, respectively. Importantly, stimulation of Wnt signaling in uninduced mK3 cells provokes an active chromatin state (high H3K4me3, low H3K27me3), recruitment of β-catenin, and loss of pre-bound histone methyltransferase Ezh2 in silent induced genes followed by activation of transcription. We conclude that the chromatin signature of uninduced and induced cells correlates strongly with their gene expression states, suggesting a role of chromatin-based mechanisms in MM cell fate.
Insights
Epigenetic changes in kidney development reveal how stem cell states are regulated. Histone modifications like H3K4me3 and H3K27me3 control gene expression in metanephric mesenchyme cells, guiding kidney nephron formation.
Area of Science:
- Developmental Biology
- Epigenetics
- Nephrogenesis
Background:
- The metanephric mesenchyme (MM) is crucial for forming nephrons, the kidney's filtering units.
- Understanding the epigenetic state of MM cells is vital but challenging due to isolation difficulties.
- MM comprises uninduced (Six2high/Lhx1low) and induced (Wnt-stimulated, Six2low/Lhx1high) cell populations.
Purpose of the Study:
- To investigate the global epigenetic state of uninduced and induced metanephric mesenchyme cells.
- To correlate chromatin signatures with gene expression patterns in MM cell fate determination.
- To explore the role of histone modifications in regulating MM cell differentiation.
Main Methods:
- Utilized two mouse clonal cell lines (mK3, mK4) representing uninduced and induced MM.
- Performed Chromatin Immunoprecipitation sequencing (ChIP-Seq) to map histone modifications (H3K4me3, H3K27me3).
- Employed ChIP-qPCR to confirm specific histone modifications and protein occupancy at gene promoters.
Main Results:
- H3K4me3 peaks were enriched in metabolic genes, while H3K27me3 peaks marked cell fate genes.
- Uninduced cells (mK3) showed H3K4me3 enrichment at 'stemness' genes (e.g., Six2), lost in induced cells (mK4).
- Induced genes (e.g., Lhx1, Pax8) transitioned to an active chromatin state (high H3K4me3, low H3K27me3) in mK4 cells.
- Wnt stimulation in mK3 cells induced an active chromatin state, β-catenin recruitment, and gene activation.
Conclusions:
- Chromatin signatures strongly correlate with gene expression states in uninduced and induced MM cells.
- Epigenetic mechanisms, involving histone modifications, play a significant role in MM cell fate decisions.
- This study provides insights into the epigenetic regulation governing kidney development.
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