Project description:Thousands of long intergenic noncoding RNAs (lincRNAs) are encoded by the mammalian genome, which were reported to have multiple biological functions as transcriptional activators acting in cis 1 or trans 2, transcriptional repressors 3,4 or miRNAs decoys 5,6. However, the function of most lincRNAs has not yet been identified in vivo. Here, we demonstrate a role for linc-MYH, a novel long intergenic noncoding RNA, in adult fast-type myofibre specialization. Skeletal myofibre fast and slow phenotypes are established through differential expression of numerous fibre-specific genes7. We show linc-MYH and the fast MYH genes share a common enhancer located in the fast MYH genes locus and regulated by the Six1 homeoproteins. Muscle-specific Six1 mutant mice show increased expression of slow-type genes, and downregulation of linc-MYH and fast-type genes. linc-MYH function revealed by in vivo knockdown and wide transcriptomic analysis, is in fine to prevent expression of genes ensuring slow muscle contractile properties, and to increase fast-type muscle gene expression in fast-type myofibres. Thus, formation of efficient fast sarcomeric units and appropriate Ca++ cycling and excitation/contraction/relaxation coupling in fast- myofibres is achieved through the coordiante control of fast MYHs and linc-MYH expression by a Six bound enhancer.
Project description:Thousands of long intergenic noncoding RNAs (lincRNAs) are encoded by the mammalian genome, which were reported to have multiple biological functions as transcriptional activators acting in cis 1 or trans 2, transcriptional repressors 3,4 or miRNAs decoys 5,6. However, the function of most lincRNAs has not yet been identified in vivo. Here, we demonstrate a role for linc-MYH, a novel long intergenic noncoding RNA, in adult fast-type myofibre specialization. Skeletal myofibre fast and slow phenotypes are established through differential expression of numerous fibre-specific genes7. We show linc-MYH and the fast MYH genes share a common enhancer located in the fast MYH genes locus and regulated by the Six1 homeoproteins. Muscle-specific Six1 mutant mice show increased expression of slow-type genes, and downregulation of linc-MYH and fast-type genes. linc-MYH function revealed by in vivo knockdown and wide transcriptomic analysis, is in fine to prevent expression of genes ensuring slow muscle contractile properties, and to increase fast-type muscle gene expression in fast-type myofibres. Thus, formation of efficient fast sarcomeric units and appropriate Ca++ cycling and excitation/contraction/relaxation coupling in fast- myofibres is achieved through the coordiante control of fast MYHs and linc-MYH expression by a Six bound enhancer. Ten μg of shRNA-expressing vector were introduced into TA muscles of 8 week-old mice by electroporation. Two weeks following electroporation, TA myofibres expressing GFP were dissected under a Nikon SMZ1500 stereo microscope and frozen in liquid nitrogen before processing. The efficiency of each shRNA was established by determination of linc-MYH transcript levels in TA muscles transfected by each shlincMYH. The shRNA against 5'- TTCTGCTCACCACCTACAATT-3' sequence was selected for the knockdown experiment. After validation of RNA quality with the Bioanalyzer 2100 (using Agilent RNA6000 nano chip kit), 50 ng of total RNA were reverse transcribed following the Ovation PicoSL WTA System (Nugen). Briefly, the resulting double-strand cDNA was used for amplification based on SPIA technology. After purification according to Nugen protocol, 5 μg of single strand DNA was used for generation of Sens Target DNA using Ovation Exon Module kit (Nugen). 2.5 μg of Sens Target DNA were fragmented and labelled with biotin using Encore Biotin Module kit (Nugen). After control of fragmentation using Bioanalyzer 2100, the cDNA was then hybridized to GeneChip® Mouse Gene 1.0 ST (Affymetrix) at 45°C for 17 hours. After overnight hybridization, the ChIPs were washed using the fluidic station FS450 following specific protocols (Affymetrix) and scanned using the GCS3000 7G. The scanned images were then analyzed with Expression Console software (Affymetrix) to obtain raw data (cel files) and metrics for Quality Controls. The analysis of some of these metrics and the study of the distribution of raw data show no outlier experiment. Gastrocnemius muscles were collected from cSix1 KO and control mice. Total RNAs were extracted by Trizol Reagent (Invitrogen) according to manufacturer's instruction. After validation of RNA quality with the Bioanalyzer 2100 (using Agilent RNA6000 nano chip kit), 50 ng of total RNA were reverse transcribed following the Ovation PicoSL WTA System (Nugen). Briefly, the resulting double-strand cDNA was used for amplification based on SPIA technology. After purification according to Nugen protocol, 5 μg of single strand DNA was used for generation of Sens Target DNA using Ovation Exon Module kit (Nugen). 2.5 μg of Sens Target DNA were fragmented and labelled with biotin using Encore Biotin Module kit (Nugen). After control of fragmentation using Bioanalyzer 2100, the cDNA was then hybridized to GeneChip® Mouse Gene 1.0 ST (Affymetrix) at 45°C for 17 hours. After overnight hybridization, the ChIPs were washed using the fluidic station FS450 following specific protocols (Affymetrix) and scanned using the GCS3000 7G. The scanned images were then analyzed with Expression Console software (Affymetrix) to obtain raw data (cel files) and metrics for Quality Controls. The analysis of some of these metrics and the study of the distribution of raw data show no outlier experiment.
Project description:The contractile properties of adult myofibers are shaped by their Myosin heavy chain (MYH) isoform content. We identify by snATAC-seq a 42kb super-enhancer (SE) at the locus regrouping the fast Myh (fMyh) genes. By 4C-seq we show that active fMyh promoters interact with the SE by DNA looping, leading to the activation of a single promoter per nucleus. A rainbow mouse transgenic model of the locus including the SE recapitulates the endogenous spatio-temporal expression of adult fMyh genes. In situ deletion of the SE by CRISPR/Cas9 editing demonstrates its major role in the control of associated fMyh genes, and deletion of two fMyh genes at the locus reveals an active competition of the promoters for the shared SE. Last, by disrupting the organization of fMyh, we uncover positional heterogeneity within limb skeletal muscles that may underlie selective muscle susceptibility to damage in certain myopathies.
Project description:Skeletal muscle fibers are large syncytia but it is currently unknown whether gene expression is coordinately regulated in their numerous nuclei. By snRNA-seq and snATAC-seq, we showed that slow, fast, myotendinous and neuromuscular junction myonuclei each have different transcriptional programs, associated with distinct chromatin states and combinations of transcription factors. In adult mice, identified myofiber types predominantly express either a slow or one of the three fast isoforms of Myosin heavy chain (MYH) proteins, while a small number of hybrid fibers can express more than one MYH. By snRNA-seq and FISH, we showed that the majority of myonuclei within a myofiber are synchronized, coordinately expressing only one fast Myh isoform with a preferential pane of muscle-specific genes. Importantly, this coordination of expression occurs early during post-natal development and depends on innervation. These findings highlight a unique mechanism of coordination of gene expression in a syncytium.
Project description:Glioblastoma multiforme (GBM) is the most common and aggressive malignant brain tumor among adults, which is characterized by high invasion, migration and proliferation abilities. One important process that contributes to the invasiveness of GBM is the epithelial to mesenchymal transition (EMT). EMT is regulated by a set of defined transcription factors which tightly regulate this process, among them is the basic helix-loop-helix family member, TWIST1. Here we show that TWIST1 is methylated on lysine-33 at chromatin by SETD6, a methyltransferase with expression levels correlating with poor survival in GBM patients. RNA-seq analysis in U251 GBM cells suggested that both SETD6 and TWIST1 regulate cell adhesion and migration processes. We further show that TWIST1 methylation attenuates the expression of the long-non-coding RNA, LINC-PINT, thereby suppressing EMT in GBM. Mechanistically, TWIST1 methylation represses the transcription of LINC-PINT by increasing the occupancy of EZH2 and the catalysis of the repressive H3K27me3 mark at the LINC-PINT locus. Under un-methylated conditions, TWIST1 dissociates from the LINC-PINT locus, allowing the expression of LINC-PINT which leads to increased cell adhesion and decreased cell migration. Together, our findings unravel a new mechanistic dimension for selective expression of LINC-PINT mediated by TWIST1 methylation.
Project description:Long noncoding RNAs regulating diverse cellular processes implicate in many diseases. Here, we report the identification of a novel long intergenic noncoding RNA, Linc-ASEN, expressed in prematurely senescent cells, that associates with UPF1 and represses cellular senescence by reducing p21 production transcriptionally and post-transcriptionally. The Linc-ASEN-UPF1 complex suppressed p21 transcription by recruiting Polycomb Repressive Complex 1 (PRC1) and PRC2 to the p21 locus, and thereby preventing binding of the transcriptional activator p53 on the p21 promoter. Moreover, the Linc-ASEN-UPF1 complex repressed p21 expression post-transcriptionally by lowering p21 mRNA stability in association with DCP1A. Accordingly, Linc-ASEN levels were found inversely correlated with p21 mRNA levels in tumor tissues from patient-derived xenograft mice, in various human cancer tissues, and in aged mice tissues. Our studies reveal that Linc-ASEN prevents cellular senescence by reducing the transcription and stability of p21 mRNA in concert with UPF1, and suggest that Linc-ASEN might be a potential therapeutic target in processes influenced by senescence, including cancer.
Project description:Long noncoding RNAs regulating diverse cellular processes implicate in many diseases. Here, we report the identification of a novel long intergenic noncoding RNA, Linc-ASEN, expressed in prematurely senescent cells, that associates with UPF1 and represses cellular senescence by reducing p21 production transcriptionally and post-transcriptionally. The Linc-ASEN-UPF1 complex suppressed p21 transcription by recruiting Polycomb Repressive Complex 1 (PRC1) and PRC2 to the p21 locus, and thereby preventing binding of the transcriptional activator p53 on the p21 promoter. Moreover, the Linc-ASEN-UPF1 complex repressed p21 expression post-transcriptionally by lowering p21 mRNA stability in association with DCP1A. Accordingly, Linc-ASEN levels were found inversely correlated with p21 mRNA levels in tumor tissues from patient-derived xenograft mice, in various human cancer tissues, and in aged mice tissues. Our studies reveal that Linc-ASEN prevents cellular senescence by reducing the transcription and stability of p21 mRNA in concert with UPF1, and suggest that Linc-ASEN might be a potential therapeutic target in processes influenced by senescence, including cancer.