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: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: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:Facioscapulohumeral muscular dystophy (FSHD) is caused by the mis-expression of DUX4 in skeletal muscle cells. DUX4 is a transcription factor that activates genes normally associated with stem cell biology and its mis-expression in FSHD cells results in apoptosis. To identify genes and pathways necessary for DUX4-mediated apoptosis, we performed an siRNA screen in an RD rhabdomyosarcoma cell line with an inducible DUX4 transgene. Our screen identified components of the MYC-mediated apoptotic pathway and the double-stranded RNA (dsRNA) innate immune response pathway as mediators of DUX4-induced apoptosis. Further investigation revealed that DUX4 expression led to increased MYC mRNA, accumulation of nuclear dsRNA foci, and activation of the dsRNA response pathway in both RD cells and human myoblasts. Nuclear dsRNA foci were associated with aggregation of the exon junction complex component EIF4A3. The elevation of MYC mRNA, dsRNA accumulation, and EIF4A3 nuclear aggregates in FSHD muscle cells suggest that these processes might contribute to FSHD pathophysiology.
Project description:Expression profiling of D. melanogaster embryos expressing bagpipe ectopically in the mesoderm, measured in a timecourse of embryogenesis. Three one-hour timepoints were assayed (3.5-4.5, 4.5-5.5, 5.5-6.5 hrs after egg laying). Homozygous ectopically expressing embryos were collected using from a large scale cross of UAS-bin and twist-Gal4, 24B-Gal4 flies, in parallel to stage-matched controls. Four independent collections were performed at each timepoint. Total RNA was extracted and amplified. Ectopically expression and respective reference samples were hybridized together on INDAC oligo-arrays.
Project description:Expression profiling of D. melanogaster embryos expressing biniou ectopically in the mesoderm, measured in a timecourse of embryogenesis. Three one-hour timepoints were assayed (4-5, 5-6, 6-7 hrs after egg laying). Homozygous ectopically expressing embryos were collected using from a large scale cross of UAS-bin and twist-Gal4, 24B-Gal4 flies, in parallel to stage-matched controls. Four independent collections were performed at each timepoint. Total RNA was extracted and amplified. Ectopically expression and respective reference samples were hybridized together on INDAC oligo-arrays.
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 sought to determine the effects of over-expression of Gli1 on gene expression in C2C12 myotube cultures. C2C12 myoblasts were induced to differentiate for 4 days. At that time, when >80% of nuclei were incorporated into multi-nucleated syncitial myotubes, we infected the cultures with recombinant adenovirus expressing GFP alone or GFP and a full length human Gli1. Media was changed 12 hours later. Cultures were lysed 60 hours after the initial infection. Gli1 over-expression induces de-differentiation of myotubes and proliferation of myoblasts.