Expression profiling data of RD and C2C12 cells ectopically expressing DUX4
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ABSTRACT: Transcriptomic changes induced by DUX4 expression were compared between human and mouse cell lines of muscle lineage. We used microarrays to compare transcripts induced in human rhabdmyosarcoma and mouse C2C12 cells ectopically expressing DUX4.
Project description:Transcriptomic changes induced by DUX4 expression were compared between human and mouse cell lines of muscle lineage. We used microarrays to compare transcripts induced in human rhabdmyosarcoma and mouse C2C12 cells ectopically expressing DUX4. Human rhabdomyosarcoma and mouse C2C12 cells were transfected with DUX4 expression vectors (n=4). Cells transfected with insertless vectors were used as controls. Samples were processed for RNA extraction 16 hours following transfection.
Project description:DUX4 is a double homeodomain transcription factor whose misexpression in the muscle causes facioscapulohumeral muscular dystrophy (FSHD). The transcriptional activity of DUX4 has been extensively characterized, and is thought to be the primary driver of FSHD pathogenesis. Yet, DUX4 expression lowers the protein level of an RNA quality control factor, UPF1, without affecting its transcript level, hinting at post-transcriptional regulatory activity downstream of DUX4 expression. How extensive the post-transcriptional activity of DUX4 is, and how relevant it is to FSHD pathogenesis, is unknown. In order to gain insight into DUX4-induced post-transcriptional gene regulation, we measured transcript and protein levels in DUX4 expressing cells via RNA-seq and SILAC-based quantitative mass spectrometry, respectively. We show that DUX4 transcriptional targets are robustly translated, including those genes previously identified as potential FSHD biomarkers. However, comparing the overall pattern of gene expression changes for RNA versus protein reveals striking differences in the most highly activated pathways, with the former showing changes in RNA processing and splicing, and the latter affecting the humoral immune response, proteolysis and exocytosis, among other pathways. Consistent with a misregulation of exocytosis, fluorescence imaging shows fragmented golgi apparatus in DUX4-expressing cells. Of the genes that showed discordant RNA and protein expression levels, post-transcriptional buffering was particularly evident for genes involved in stress response and may explain why DUX4-expressing cells succumb to toxicity despite robust transcriptional activation of stress response genes. Moreover, several genes involved in RNA decay including UPF1, UPF3B, SMG6 and XRN1 showed downregulation at the protein level, which may explain the massive inhibition of RNA quality control in DUX4-expressing cells. These results highlight the importance of considering post-transcriptional gene regulation in DUX4-expressing cells in order to fully understand the FSHD disease process.
Project description:All types of facioscapulohumeral muscular dystrophy (FSHD) are caused by the aberrant myogenic activation of the somatically silent DUX4 gene, which initiates a cascade of cellular events ultimately leading to FSHD pathophysiology. Therefore, FSHD is a dominant gain-of-function disease that is amenable to modeling by DUX4 overexpression. However, there is large variability in the patient population. Typically, progressive skeletal muscle weakness becomes noticeable in the second or third decade of life, yet there are many genetically FSHD individuals who develop symptoms much later in life or remain relatively asymptomatic throughout their lives. Conversely, in rare cases, FSHD may present clinically prior to 5-10 yrs of age, ultimately manifesting as a very severe early onset form of the disease. Thus, there is a need to control the timing and severity of pathology in FSHD-like models. Methods: We have recently described a line of conditional DUX4 transgenic mice, FLExDUX4, that develop a myopathy upon induction of human DUX4-fl expression in skeletal muscle. Here, we use the FLExDUX4 mouse crossed with the skeletal muscle-specific and tamoxifen inducible line ACTA1-MerCreMer to generate a highly versatile bi-transgenic mouse model with chronic, low-level DUX4-fl expression and mild pathology, that can be induced to develop more severe FSHD-like pathology in a dose-dependent response to tamoxifen. We identified conditions to reproducibly generate models exhibiting mild, moderate, or severe DUX4-dependent pathophysiology, and characterized their progression. Results: We assayed DUX4-fl mRNA and protein levels, fitness, strength, global gene expression, histopathology, and immune response, all of which are consistent with an FSHD-like myopathic phenotype. Importantly, we identified sex-specific and muscle-specific differences that should be considered when using these models for preclinical studies. Conclusions: The ACTA1-MCM;FLExDUX4 bi-transgenic mouse model expresses a chronic low level of DUX4-fl and has mild pathology and detectable muscle weakness. The onset and progression of moderate to severe pathology can be controlled via tamoxifen injection to provide consistent and readily screenable phenotypes for assessing therapies targeting DUX4-fl mRNA and protein. Thus, these FSHD-like mouse models can be used to study a range of DUX4-fl expression and pathology dependent upon investigator need, through controlled mosaic expression of DUX4.
Project description:The human double-homeodomain retrogene DUX4 is normally expressed at high levels in germ cells of the testis. When aberrantly expressed in muscle its protein product causes facioscapulohumeral muscular dystrophy (FSHD), perhaps partly by inducing inappropriate expression of germline genes. DUX4 can bind >60,000 locations in the human genome that contain a strongly enriched sequence motif. Numerous long terminal repeat (LTR) class repetitive elements are enriched among DUX4 binding sites, including many from the mammalian apparent LTR-retrotransposon (MaLR) family as well as some ERVL and ERVK types, with MaLRs comprising ~1/3 of DUX4’s binding sites. We performed RNA-seq on myoblasts over-expressing DUX4 and find that DUX4 binding activates transcription of some but not all bound repeat types. Some of these activated repetitive elements comprise novel promoters for genes, long non-coding RNAs and antisense transcripts. We show that some of these chimeric repeat-initiated transcripts are expressed in testis and FSHD patient myotubes. The acquisition of MaLR-LTR elements during mammalian evolution may therefore have allowed rewiring of the transcriptional network. We also find that the pericentromeric satellite HSATII can be bound by DUX4 and that its transcription is massively induced by DUX4 over-expression. Our findings suggest a role for repetitive element transcripts in muscle disease and in the biology of normal testis. RNA-seq of two myoblast cell lines transduced with lentivirus carrying DUX4, and two control myoblast lines
Project description:We determined the effects of short pulses of DUX4 expression on genome-wide transcription, mimicking the embryonic expression of this gene, using a DUX4-inducible cell culture model of FSHD (MB135iDUX4). We found that a second pulse of DUX4 has a synergistic effect and shows greater induction of DUX4 targets. Knockdown of DUX4-induced histone variants H3.X and H3.Y has no effect on DUX4 targets with a single pulse of DUX4 but eliminates the superinduction seen with a second pulse, showing that these histones are required for this increase in expression.
Project description:We determined the effects of short pulses of DUX4 expression on genome-wide transcription, mimicking the embryonic expression of this gene, using a DUX4-inducible cell culture model of FSHD (MB135iDUX4). We found that a second pulse of DUX4 has a synergistic effect and shows greater induction of DUX4 targets. Knockdown of DUX4-induced histone variants H3.X and H3.Y has no effect on DUX4 targets with a single pulse of DUX4 but eliminates the superinduction seen with a second pulse, showing that these histones are required for this increase in expression.
Project description:Facioscapulohumoral muscular dystrophy (FSHD) is caused by misexpression of the DUX4 transcription factor in skeletal muscle that results in transcriptional alterations, abnormal phenotypes, and cell death. To gain insight into the kinetics of DUX4-induced stresses, we activated DUX4 expression in myoblasts and performed longitudinal RNA sequencing paired with proteomics and phosphoproteomics. This analysis revealed changes in cellular physiology including DNA damage and altered mRNA splicing. Phosphoproteomic analysis uncovered widespread changes in protein phosphorylation rapidly following DUX4 induction indicating that alterations in kinase signaling may play a role in DUX4-mediated stress and cell death. Indeed, we demonstrate that two stress-responsive MAP kinase pathways, JNK and p38, are activated in response to DUX4 expression. Inhibition of each of these pathways ameliorated DUX4-mediated cell death in myoblasts. These findings uncover JNK as a novel pathway involved in DUX4-mediated cell death as well as provide additional insights into the role of the p38 pathway, a clinical target for the treatment of FSHD.
Project description:The aim of this study is to define the molecular mechanisms underlying DUX4-associated toxicity in the context of facioscapulohumeral muscular dystrophy (FSHD). DUX4 is a transcription factor, which induces cell death by activating the transcription of its targets. No molecule able to directly control DUX4 activity is currently known. By using a tandem affinity purification protocol combined to mass spectrometry analysis, we identified Matrin 3 (MATR3), as the first cellular factor able to directly block DUX4 toxic activity. We found that MATR3 binds to the DNA binding domain of DUX4 blocking the activation of its genomic targets.