Assessment of functional overlap between mouse Dux and human DUX4 in vitro and in vivo
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ABSTRACT: We report both DUX4 and Dux toxicity depend upon their ability to bind DNA and activate transcription. Chromatin immunoprecipitation of V5 epitope tagged human DUX4 and mouse Dux was performed in human myoblasts was analyzed using ChIP-Seq to identify their subsequent binding sites. We found that DUX4 and Dux bind 4-8% of identical sequences, while majority of the binding sites are unique to either DUX4 or Dux. Although small, this overlap could be due to their conserved abilioty to regualte primordial pathways that were essential for life and therefore maintained in both proteins despite their separate evolutionary paths. We performed ChIP-Seq analysis of human myoblasts transfected with plasmids encoding either epitope tagged human DUX4 (1 sample) and mouse Dux (1 sample). Illumina sequencing libraries were prepared from the ChIP and Input DNA, then resulting DNA libraries were quantified and sequenced and aligned to the human genome (hg19).
Project description:We report the RNA-seq experiments performed in human myoblasts transfected with human DUX4 and mouse Dux. Comparison of genes up- and down-regulated by DUX4 and Dux in human myoblasts to identify pathways similiarly regulated by both transcription factors.
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:Facioscapulohumeral dystrophy (FSHD) is one of the most common inherited muscular dystrophies. The causative gene remains controversial and the mechanism of pathophysiology unknown. Here we identify genes associated with germline and early stem cell development as targets of the DUX4 transcription factor, a leading candidate gene for FSHD. The genes regulated by DUX4 are reliably detected in FSHD muscle but not in controls, providing direct support for the model that misexpression of DUX4 is a causal factor for FSHD. Additionally, we show that DUX4 binds and activates LTR elements from a class of MaLR endogenous primate retrotransposons and suppresses the innate immune response to viral infection, at least in part through the activation of DEFB103, a human defensin that can inhibit muscle differentiation. These findings suggest specific mechanisms of FSHD pathology and identify candidate biomarkers for disease diagnosis and progression. [Overexpression experiment] Quadruplicate total RNA samples were collected from control human primary myoblasts transduced with lentivirus carrying DUX4-fl, DUX4-s or GFP (MOI = 15) for 24 h and from untransduced myoblasts. [Defensin experiment] Quadruplicate samples were also collected from myoblasts and myotubes grown in media containing human beta-defensin 3 peptide or in control media.
Project description:The human double-homeodomain retrogene DUX4 is expressed in the testis and epigenetically repressed in somatic tissues. Facioscapulohumeral muscular dystrophy (FSHD) is caused by mutations that decrease the epigenetic repression of DUX4 in somatic tissues and result in mis-expression of this transcription factor in skeletal muscle. DUX4 binds sites in the human genome that contain a double-homeobox sequence motif, including sites in unique regions of the genome as well as many sites in repetitive elements. Using ChIP-seq and RNA-seq on myoblasts transduced with DUX4 we show that DUX4 binds and activates transcription of mammalian apparent LTR-retrotransposons (MaLRs), endogenous retrovirus (ERVL and ERVK) elements, and pericentromeric satellite HSATII sequences. Some DUX4-activated MaLR and ERV elements create novel promoters for genes, long non-coding RNAs, and antisense transcripts. Many of these novel transcripts are expressed in FSHD muscle cells but not control cells, and thus might contribute to FSHD pathology. For example, HEY1, a repressor of myogenesis, is activated by DUX4 through a MaLR promoter. DUX4-bound motifs, including those in repetitive elements, show evolutionary conservation and some repeat-initiated transcripts are expressed in healthy testis, the normal expression site of DUX4, but more rarely in other somatic tissues. Testis expression patterns are known to have evolved rapidly in mammals, but the mechanisms behind this rapid change have not yet been identified: our results suggest that mobilization of MaLR and ERV elements during mammalian evolution altered germline gene expression patterns through transcriptional activation by DUX4. Our findings demonstrate a role for DUX4 and repetitive elements in mammalian germline evolution and in FSHD muscular dystrophy. RNA-seq of differentiated human primary myotube cell lines for FSHD patients and control samples Raw data not provided due to patient privacy concerns.
Project description:Facioscapulohumeral dystrophy (FSHD) is caused by decreased epigenetic repression of the D4Z4 macrosatellite array and recent studies have shown that this results in the expression of low levels of the DUX4 mRNA in skeletal muscle. Several other mechanisms have been suggested for FSHD pathophysiology and it remains unknown whether DUX4 expression can account for most of the molecular changes seen in FSHD. Since DUX4 is a transcription factor, we used RNA-seq to measure gene expression in muscle cells transduced with DUX4, and in muscle cells and biopsies from control and FSHD individuals. We show that DUX4 target gene expression is the major molecular signature in FSHD muscle together with a gene expression signature consistent with an immune cell infiltration. In addition, one unaffected individual without a known FSHD-causing mutation showed expression of DUX4 target genes. This individual has a sibling with FSHD and also without a known FSHD-causing mutation, suggesting the presence of yet unidentified modifier locus for DUX4 expression and FSHD. These findings demonstrate that expression of DUX4 accounts for the majority of the gene expression changes in FSHD skeletal muscle together with an immune cell infiltration. RNA-seq for muscle cells and biopsies from control and FSHD individuals.
Project description:We have carried out systematic analysis of protein expression changes during differentiation of human myoblasts into myotubes over 6 days period in cell culture.
Project description:Facioscapulohumeral dystrophy (FSHD) is one of the most common inherited muscular dystrophies. The causative gene remains controversial and the mechanism of pathophysiology unknown. Here we identify genes associated with germline and early stem cell development as targets of the DUX4 transcription factor, a leading candidate gene for FSHD. The genes regulated by DUX4 are reliably detected in FSHD muscle but not in controls, providing direct support for the model that misexpression of DUX4 is a causal factor for FSHD. Additionally, we show that DUX4 binds and activates LTR elements from a class of MaLR endogenous primate retrotransposons and suppresses the innate immune response to viral infection, at least in part through the activation of DEFB103, a human defensin that can inhibit muscle differentiation. These findings suggest specific mechanisms of FSHD pathology and identify candidate biomarkers for disease diagnosis and progression. Examine Dux4 full isoform binding sites in human fibroblast.
Project description:Ectopic expression of the double homeodomain transcription factor DUX4 causes facioscapulohumeral muscular dystrophy (FSHD). Mechanisms of action of DUX4 are currently unknown. Using immortalized human myoblasts with a titratable DUX4 transgene, we identify by mass spectrometry an interaction between the DUX4 C-terminus and the histone acetyltransferases p300/CBP. Chromatin immunoprecipitation shows that DUX4 recruits p300 to its target gene, ZSCAN4, displaces histone H3 from the center of its binding site, and induces H3K27Ac in its vicinity, but C-terminal deleted DUX4 does not. We show that a DUX4 minigene, bearing only the homeodomains and C-terminus, is transcriptionally functional and cytotoxic, and that overexpression of a nuclear targeted C-terminus impairs the ability of WT DUX4 to interact with p300 and to regulate target genes. Genomic profiling of DUX4, histone H3, and H3 modifications reveals that DUX4 binds two classes of locus: DNase accessible H3K27Ac-rich chromatin and inaccessible H3K27Ac-depleted MaLR-enriched chromatin. At this latter class, it acts as a pioneer factor, recruiting H3K27 acetyltransferase activity and opening the locus for transcription. In concert with local increased H3K27Ac, the strong H3K27Ac peaks at distant sites are significantly depleted of H3K27Ac, thus DUX4 uses its C-terminus to induce a global reorganization of H3K27 acetylation. Two biological samples were analyzed with 4 antibodies for ChIP-Seq and in triplicate for RNA-Seq.
Project description:We report both DUX4 and Dux toxicity depend upon their ability to bind DNA and activate transcription. Chromatin immunoprecipitation of V5 epitope tagged human DUX4 and mouse Dux was performed in human myoblasts was analyzed using ChIP-Seq to identify their subsequent binding sites. We found that DUX4 and Dux bind 4-8% of identical sequences, while majority of the binding sites are unique to either DUX4 or Dux. Although small, this overlap could be due to their conserved abilioty to regualte primordial pathways that were essential for life and therefore maintained in both proteins despite their separate evolutionary paths.
Project description:GATA4 occupancy on the mouse genome of satellite cell-derived primary myoblasts. Proliferating myoblasts cultured in growth medium were immunoprecipitated with anti-GATA4 antibody or control IgG. Precipitated genomic DNAs were subjected to next generation sequencing. Paired-end 150 bp sequence reads of GATA4-ChIP and IgG-ChIP using mouse skeletal muscle myoblasts.