Nucleosome maps in skeletal muscle in response to diet in vivo
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ABSTRACT: The nucleosome signature reflects the cellular epigenetic memory and contributes to the cellular phenotype and function. Obesity and type 2 diabetes pathogenesis is largely dependent on environmentally-induced epigenetic modifications and is marked by skeletal muscle insulin resistance; however, no in vivo skeletal muscle nucleosome maps exist to date. Herein, whole genome nucleosome maps via MNase-seq in skeletal muscle of mice on a low fat, high fat or high fat diet with the chromatin modifier sodium butyrate show that complex interactions among mitochondrial function, the tissue microenvironment, cellular phenotype and nucleosome landscape determine whole body phenotype and insulin resistance. Skeletal muscle samples (n=5 per group) were pooled after homogenization under liquid nitrogen with a motar and pestle to give one sample per group for MNase-seq
Project description:We performed ChIP-Seq for hallmark TFs (Ets1, Runx1), histone modification marks (H3K4me1, H3K4me2, H3K4me3, H3K27me3, H3K36me3), total RNA Pol II, short RNA-Seq as well as nucleosome mapping mainly in murine Rag2 -/- thymocytes. We also performed ChIP-Seq for E47 as well as nucleosome mapping, gene expression microarray analysis in CD4+ CD8+ DP thymocytes. Overall, we find a key role for the transcription factor Ets1, contributing towards alpha beta T cell lineage commitment via differential transactivation of stage-specific genes orchestrated by dynamic, co-association -mediated chromatin remodeling, as well as transcription dependent generation of a specialized chromatin structure at the TCR beta locus. Genome-wide analysis via ChIP-Seq for Ets1, Runx1, total RNA Pol II binding, H3K4me1, H3K4me2, H3K4me3, H3K27me3, H3K36me3, short RNA-Seq, Mnase-Seq in murine Rag2 -/- thymocytes, ChIP-Seq for E47, Mnase-Seq and gene expression microarray analysis in DP thymocytes This Series represents ChIP-Seq data.
Project description:The nucleosome signature reflects the cellular epigenetic memory and contributes to the cellular phenotype and function. Obesity and type 2 diabetes pathogenesis is largely dependent on environmentally-induced epigenetic modifications and is marked by skeletal muscle insulin resistance; however, no in vivo skeletal muscle nucleosome maps exist to date. Herein, whole genome nucleosome maps via MNase-seq in skeletal muscle of mice on a low fat, high fat or high fat diet with the chromatin modifier sodium butyrate show that complex interactions among mitochondrial function, the tissue microenvironment, cellular phenotype and nucleosome landscape determine whole body phenotype and insulin resistance.
Project description:We performed ChIP-Seq for hallmark TFs (Ets1, Runx1), histone modification marks (H3K4me1, H3K4me2, H3K4me3, H3K27me3, H3K36me3), total RNA Pol II, short RNA-Seq as well as nucleosome mapping mainly in murine Rag2 -/- thymocytes. We also performed ChIP-Seq for E47 as well as nucleosome mapping, gene expression microarray analysis in CD4+ CD8+ DP thymocytes. Overall, we find a key role for the transcription factor Ets1, contributing towards alpha beta T cell lineage commitment via differential transactivation of stage-specific genes orchestrated by dynamic, co-association -mediated chromatin remodeling, as well as transcription dependent generation of a specialized chromatin structure at the TCR beta locus. Genome-wide analysis via ChIP-Seq for Ets1, Runx1, total RNA Pol II binding, H3K4me1, H3K4me2, H3K4me3, H3K27me3, H3K36me3, short RNA-Seq, Mnase-Seq in murine Rag2 -/- thymocytes, ChIP-Seq for E47, Mnase-Seq and gene expression microarray analysis in DP thymocytes This Series represents Mnase-Seq data.
Project description:Nucleosome structure directly influences gene transcription. However, the function of each histone residue remains largely unknown. Here we profiled gene expression changes upon the mutation of individual residues of histone H3 and H4. Histone residues grouped by expression change similarity displayed overall structural relevance. This regulatory functional map of the core histones led to novel findings. First, the residues specific to each histone family tend to be more influential than those commonly found among different histones. Second, unlike histone acetylations, H3K4 trimethylation does not appear to be prerequisite for gene activation. Third, H3Q5 has been newly identified for its putative interactions with many chromatin regulators for transcription control. Lastly, the nucleosome lateral surface seems to play a key role through interactions with the surrounding DNA. Remarkably, we discovered a novel role for H3K56 in chromatin dynamics. The deletion of this residue, but not the alteration of acetylation states, caused a genome-wide decrease in nucleosome mobility and stabilized nucleosome positioning near transcription start and end sites. Occupying the DNA entry/exit site, H3K56 is thought to modulate nucleosome sliding along DNA. Taken together, genomics approaches such as microarray and deep sequencing prove valuable for mapping the function of histone residues. Performing Mnase-seq for six histone mutants and two wild-types in Saccharomyces cerevisiae
Project description:C18ORF25 is a homolog of Arkadia (RNF111), an E3 ubiquitin ligase with SUMO-interaction motifs (SIMs) (PMID: 31417085). However, C18ORF25 lacks the entire C-terminal RING domain of RNF111 which is required for ubiquitin binding suggesting it lacks ubiquitination activity and may therefore act as an adaptor or signalling scaffold (PMID: 26283374). We have previously shown that mice lacking C18Orf25 throughout the entire body have increased adiposity, decreased lean mass, lower exercise capacity and significantly reduced ex vivo skeletal muscle force production (PMID: 35882232). Skeletal muscle isolated from C18Orf25 knockout (KO) mice have reduced cAMP-dependent protein kinase A (PKA) levels, and reduced phosphorylation of several contractile proteins and proteins involved in calcium handling. Furthermore, analysis of single muscle fibres from C18Orf25 KO mice revealed impaired SR calcium cycling in fast-twitch fibres only (PMID: 35882232). We also previously showed that the exercise-regulated phosphorylation of S67 on C18ORF25 is directly catalysed by AMPK. This phosphorylation site plays an important role in the function of C18ORF25 as re-expression of a phospho-mimetic S66/67D but not phospho-dead S66/67A in C18Orf25 KO mice is able to rescue skeletal muscle contractile defects PMID: 35882232). In the present study, we further investigated the potential molecular functions of C18ORF25. We performed affinity purification coupled to tandem mass spectrometry (AP-MS) to probe the protein:protein interaction (PPI) landscape of C18ORF25. Included in this analysis was also an investigation of potential S67 phosphorylation-dependent PPIs.
Project description:Background Three-dimensional (3D) bioengineered models of human skeletal muscle are a promising approach for studying muscle development, function and disease in vitro. These models more closely resemble the complexity of native muscle tissue than two-dimensional (2D) monolayer culture and allow for functional measurements to be performed. However, a more complete understanding of how culture condition and duration impacts the myotube maturity and function is required to validate the transition from 2D to 3D culture of muscle cells. Methods Human skeletal muscle cells were cultured as either 2D monolayers or within 3D fibrin-based hydrogels as muscle constructs for up to 21 days. Quantitative proteomic analysis and functional assessments, including contractile force and cross-sectional area measurements, were conducted to evaluate the impact of culture conditions and duration on muscle cell differentiation. Results Proteomic analysis revealed myoblasts differentiated into myotubes by 8 days of differentiation in both 2D and 3D environments. However, the proteomic profiles of myotubes varied significantly between the two culture environments. At day 8 of differentiation, myosin heavy chain isotype abundance indicated a predominantly slow-twitch phenotype in 3D constructs, compared to a mixed fibre type phenotype in 2D monolayers. By day 21 of differentiation, 3D muscle constructs displayed improved mitochondrial maturity, extracellular matrix remodelling, and signs of transitioning towards a fast-twitch phenotype. This prolonged culture duration also resulted in increased passive tension but decreased peak contractile force in 3D muscle constructs. Conclusions This study demonstrates that 3D culture promotes maturity in human skeletal muscle cells, mimicking the biochemical cues and energy demands seen in native muscle tissue. The data highlights the importance of selecting appropriate culture conditions and durations when studying skeletal muscle cells in vitro and suggests 8 days of differentiation as optimal for achieving peak contractile force in 3D muscle constructs.
Project description:Skeletal muscle atrophy is a serious and highly prevalent condition that remains poorly understood at the molecular level. Previous work found that skeletal muscle atrophy involves an increase in skeletal muscle Gadd45a expression, which is necessary and sufficient for skeletal muscle fiber atrophy. However, the direct mechanism by which Gadd45a promotes skeletal muscle atrophy was unknown. To address this question, we biochemically isolated skeletal muscle fiber proteins that associate with Gadd45a as it induces skeletal muscle atrophy in living mice. We found that Gadd45a interacts with multiple proteins in skeletal muscle fibers, including, most prominently, the MAP kinase kinase kinase MEKK4. Furthermore, by forming a complex with MEKK4 in skeletal muscle fibers, Gadd45a increases MEKK4 protein kinase activity, which is sufficient to induce skeletal muscle fiber atrophy and required for Gadd45a-mediated skeletal muscle fiber atrophy. Together, these results identify a direct biochemical mechanism by which Gadd45a induces skeletal muscle atrophy and provide new insight into way that skeletal muscle atrophy occurs at the molecular level.
Project description:Recent studies have revealed a myriad of non-coding transcripts in different organisms. For instances, the presence of short bidirectional transcripts is a hallmark of active promoters in mammals, while upstream non-coding transcripts can be detected at most expressed genes in conditions where the RNA degradation machinery is inhibited. Here, we used RNA-seq with very high sequencing depth to characterize strand-specific transcripts from primary mouse tissues. We found that a substantial fraction of gene promoters sustain expression of long non-coding antisense transcripts. These transcripts have an average size of 6 kb, have features of mature transcripts, but remain associated with the chromatin. We named this new class of non-coding RNAs Long Upstream Antisense Transcripts (LUAT). Strikingly, the LUAT and coding gene pairs are usually co-regulated, with the associated genes often/generally coding for transcriptional regulators functioning during development and cell differentiation. Indeed, these bidirectional promoters share several characteristics of developmental gene promoters, including large CpG islands and high degree of conservation, and display symetrical GC skews. Finally, we found that bidirectional promoters have enlarged platforms of Pol II initiation, associated with an intensified rate of early transcriptional elongation. We concluded that promoters of developmental regulators are characterized by a specialized mechanism of Pol II transcription, whereby Pol II poising is directly coupled to relaxed bidirectional transcription. Runx1 ChIP-seq in CD4+,CD8+ double-positive (DP) mice thymocytes using single-end sequencing on AB SOLiD Systems.
Project description:To begin to validate potential causal regulators of muscle function, we targeted genes containing novel skeletal muscle pQTLs and molecular/phenotypic associations, and performed a functional genomic screen in human skeletal muscle organoids (PMID: 30527761). We focused on proteins with negative associations to lean mass, grip strength or other metabolic associations, and generated a total of 27 individual rAAV6:shRNAs. Organoids were grown around contraction posts to monitor contractile force production during electrical stimulation, and transduced following differentiation and maturation to limit effects on the myogenic program (Figure 3A). Electrical stimulation was performed to induce either a tetanic contraction for assessment of maximum force production or stimulated with sustained lower frequency for assessment of fatigue. Following the protocol, organoids were analysed by proteomics which quantified 17/27 targets with 13 targets significantly reduced in abundance by rAAV6:shRNA.