Project description:Super-enhancers (SEs) are cis-regulatory elements enriching lineage specific key transcription factors (TFs) to form hotspots. A paucity of identification and functional dissection promoted us to investigate SEs during myoblast differentiation. ChIP-seq analysis of histone marks leads to the uncovering of SEs which remodel progressively during the course of differentiation. Further analyses of TF ChIP-seq enable the definition of SE hotspots co-bound by the master TF, MyoD and other TFs, among which we perform in-depth dissection for MyoD/FoxO3 interaction in driving the hotspots formation and SE activation.
Project description:Super-enhancers (SEs) are cis-regulatory elements enriching lineage specific key transcription factors (TFs) to form hotspots. A paucity of identification and functional dissection promoted us to investigate SEs during myoblast differentiation. ChIP-seq analysis of histone marks leads to the uncovering of SEs which remodel progressively during the course of differentiation. Further analyses of TF ChIP-seq enable the definition of SE hotspots co-bound by the master TF, MyoD and other TFs, among which we perform in-depth dissection for MyoD/FoxO3 interaction in driving the hotspots formation and SE activation.
Project description:Histone chaperones affect chromatin structure and gene expression through interaction with histones and RNA polymerase II (PolII). Here, we report that the histone chaperone Spt6 counteracts H3K27me3, an epigenetic mark deposited by the Polycomb Repressive Complex 2 (PRC2) and associated with transcriptional repression. We found that Spt6 is required for proper engagement and function of the H3K27 demethylase KDM6A (UTX) on muscle genes and regulates muscle gene expression and cell differentiation. ChIP-Seq experiments revealed an extensive genome-wide overlap of Spt6, PolII and KDM6A at transcribed regions that are devoid of H3K27me3. Mammalian cells and zebrafish embryos with reduced Spt6 display increased H3K27me3 and diminished expression of the master regulator MyoD, resulting in myogenic differentiation defects. As a confirmation for an antagonistic relationship between Spt6 and H3K27me3, inhibition of PRC2 permits MyoD re-expression in myogenic cells with reduced Spt6. Our data indicate that, through cooperation with PolII and KDM6A, Spt6 orchestrates removal of H3K27me3, thus effectively controlling developmental gene expression and cell differentiation. Examination of Spt6 and KDM6A levels in a skeletal muscle cells at various developmental stages
Project description:Cell-type specific transcription factors play important roles in lineage specification whereas it is largely unknown whether and how they regulate context-specific 3D chromatin structure. Herein, we comprehensively mapped 3D chromatin organization in muscle cells and uncovered master transcription factor MyoD-mediated myogenic lineage specific chromatin structures in comparison with embryonic stem cells and neuronal cells. We discovered that MyoD is significantly enriched at loop anchor and mediate numerous chromatin loops without CTCF binding. Importantly, we found MyoD-involved interactions were dramatically disrupted when MyoD was absent, implying MyoD is an indispensable factor for loop regulation. Additionally, MyoD mediated shorter, weaker and more dynamic interactions, especially enhancer - enhancer and enhancer - promoter loops. Finally, MyoD mainly regulate cell type-specific contacts which were concomitant to muscle cell specific gene expression. Collectively, we utilized high resolution Hi-C data and genetic model to prove a master transcriptional factor govern lineage specific chromatin loops. We propose that MyoD-mediated interactions are a general feature of lineage specific transcriptional factors-regulated gene expression.
Project description:Forkhead Box O (FOXO) transcription factors are versatile players in diverse cellular processes, affecting tumorigenesis, metabolism, stem cell maintenance and lifespan. To understand the transcriptional output of FOXO3 activation, we investigate features that define the subset of enhancer binding events that actually contribute to gene regulation. We show FOXO3 transcriptional output is determined by the amount of bound FOXO3, which in turn is determined by motif presence, pre-existing enhancer activity and accessibility. In this manner, FOXO3 amplifies pre-existing levels of activity marks and potentiates enhancer RNA transcription. We conclude that not only enhancer presence and sequence content, but also the pre-existing activity dictates FOXO3 binding and transcriptional output. Considering the flexible and cell type specific nature of regulatory regions and their activity, our observations provide a novel explanation for the diversity in FOXO transcriptional programs and introduce chromatin context as a new player in the regulation of FOXO activity in ageing and disease. Examination of histone modifications and transcriptome changes upon FOXO activation
Project description:The physiological functions and downstream effectors of the atypical mitogen-activated protein kinase ERK3 remain to be characterized. We recently reported that mice expressing catalytically-inactive ERK3 (Mapk6KD/KD) exhibit a reduced post-natal growth rate as compared to control mice. Here, we show that genetic inactivation of ERK3 impairs post-natal skeletal muscle growth and adult muscle regeneration after injury. Loss of MK5 phenocopies the muscle phenotypes of Mapk6KD/KD mice. At the cellular level, genetic or pharmacological inactivation of ERK3 or MK5 induces precocious differentiation of C2C12 or primary myoblasts, concomitant with MyoD activation. Reciprocally, ectopic expression of activated MK5 inhibits myogenic differentiation. Mechanistically, we show that MK5 directly phosphorylates FoxO3, promoting its degradation and reducing its association with MyoD. Depletion of FoxO3 rescues in part the premature differentiation of C2C12 myoblasts observed upon inactivation of ERK3 or MK5. Our findings reveal that ERK3 and its substrate MK5 act in a linear signaling pathway to control post-natal myogenic differentiation.
Project description:Evidence of widespread transcription at active enhancers became apparent. However, our understanding about the functions of enhancer RNAs (eRNAs) and their mechanistic roles remains incomplete. Here, we study eRNA regulation and function using skeletal myoblast differentiation as a paradigm. We provide a panoramic view of enhancer transcription and uncover reprogramming in enhancer transcription occurring during myogenic differentiation. We demonstrate the critical role of MyoD in activating eRNAs production. Results from in depth dissection of two eRNAs transcribed from super enhancers (seRNA-1 and -2) suggest that seRNAs can promote myogenic differentiation in vitro and in vivo; the induction of the seRNAs is in coordination with the activation of the neighboring genes and seRNA loss largely impairs their expression. Mechanistically, we elucidate these seRNAs specifically bind to heterogeneous nuclear ribonucleoprotein L (hnRNPL) and modulate hnRNPL binding to the target promoter. A CAAA tract on the seRNA was identified to be essential in mediating the interaction between seRNA-1 and hnRNPL. Disruption of seRNA-hnRNPL interaction attenuates Pol II and H3K36me3 deposition at the target genes, in coincidence with the reduction of their expression. Furthermore, analyses of hnRNPL binding transcriptome-wide reveals its association with eRNAs is a general phenomenon in multiple cells. Collectively, we propose that eRNA-hnRNPL interaction contributes to target mRNA activation.
Project description:Evidence of widespread transcription at active enhancers became apparent. However, our understanding about the functions of enhancer RNAs (eRNAs) and their mechanistic roles remains incomplete. Here, we study eRNA regulation and function using skeletal myoblast differentiation as a paradigm. We provide a panoramic view of enhancer transcription and uncover reprogramming in enhancer transcription occurring during myogenic differentiation. We demonstrate the critical role of MyoD in activating eRNAs production. Results from in depth dissection of two eRNAs transcribed from super enhancers (seRNA-1 and -2) suggest that seRNAs can promote myogenic differentiation in vitro and in vivo; the induction of the seRNAs is in coordination with the activation of the neighboring genes and seRNA loss largely impairs their expression. Mechanistically, we elucidate these seRNAs specifically bind to heterogeneous nuclear ribonucleoprotein L (hnRNPL) and modulate hnRNPL binding to the target promoter. A CAAA tract on the seRNA was identified to be essential in mediating the interaction between seRNA-1 and hnRNPL. Disruption of seRNA-hnRNPL interaction attenuates Pol II and H3K36me3 deposition at the target genes, in coincidence with the reduction of their expression. Furthermore, analyses of hnRNPL binding transcriptome-wide reveals its association with eRNAs is a general phenomenon in multiple cells. Collectively, we propose that eRNA-hnRNPL interaction contributes to target mRNA activation.
Project description:Evidence of widespread transcription at active enhancers became apparent. However, our understanding about the functions of enhancer RNAs (eRNAs) and their mechanistic roles remains incomplete. Here, we study eRNA regulation and function using skeletal myoblast differentiation as a paradigm. We provide a panoramic view of enhancer transcription and uncover reprogramming in enhancer transcription occurring during myogenic differentiation. We demonstrate the critical role of MyoD in activating eRNAs production. Results from in depth dissection of two eRNAs transcribed from super enhancers (seRNA-1 and -2) suggest that seRNAs can promote myogenic differentiation in vitro and in vivo; the induction of the seRNAs is in coordination with the activation of the neighboring genes and seRNA loss largely impairs their expression. Mechanistically, we elucidate these seRNAs specifically bind to heterogeneous nuclear ribonucleoprotein L (hnRNPL) and modulate hnRNPL binding to the target promoter. A CAAA tract on the seRNA was identified to be essential in mediating the interaction between seRNA-1 and hnRNPL. Disruption of seRNA-hnRNPL interaction attenuates Pol II and H3K36me3 deposition at the target genes, in coincidence with the reduction of their expression. Furthermore, analyses of hnRNPL binding transcriptome-wide reveals its association with eRNAs is a general phenomenon in multiple cells. Collectively, we propose that eRNA-hnRNPL interaction contributes to target mRNA activation.