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Elevated Labile Iron Contributes to Membrane Repair Deficits in FSHD

ABSTRACT: Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant muscle disease caused by expression of the transcription factor DUX4, which we previously found to be associated with plasma membrane (PM) repair deficits. However, the molecular mechanisms associated with poor membrane repair are not clear. Here, we show PM injury itself results in mild but significant increase in DUX4 mRNA expression, as well dysregulation of genes enriched in pathways critical for membrane repair. We find these dysregulated genes to be sensitive classifiers of FSHD status in human muscle biopsies, indicating their potential utility as novel biomarkers. In addition, FSHD myoblasts show dysregulation of genes in the ferroptosis cell death signaling pathway in response to membrane damage. Subsequent experiments indicated FSHD myoblasts present with hallmark features of ferroptotic stress, including elevated labile ferrous (Fe2+) iron, and lipid peroxidation at baseline and post-injury. Furthermore, we demonstrate that the expression of ferroptosis biomarkers is elevated in FSHD muscle biopsies, which is predictive of the presence of inflammation and positively correlates with the degree of fatty infiltration in FSHD skeletal muscle. Increasing labile iron and lipid peroxidation worsens membrane repair in FSHD myoblasts, while treatment with the iron chelator 2,2′-Bipyridyl and ferroptosis inhibitor ferrostatin-1 improve repair. These data are the first to identify signs of ferroptotic stress in FSHD myoblasts, and demonstrate the potential therapeutic benefit of iron chelation and ferroptosis inhibition to improve membrane repair capacity in FSHD.

ORGANISM(S): Homo sapiens

PROVIDER: GSE303359 | GEO | 2026/04/02

REPOSITORIES: GEO

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Iron supplementation alleviates pathologies in a mouse model of facioscapulohumeral muscular dystrophy

Project description:Facioscapulohumeral muscular dystrophy (FSHD) is a genetic muscle disease caused by ectopic expression of the toxic protein DUX4, resulting in muscle weakness. However, the mechanism by which DUX4 exerts its toxicity remains unclear. In this study, we observed abnormal iron accumulation in muscles of patients with FSHD and in muscle-specific DUX4-expressing (DUX4-Tg) mice. Treatment with iron chelators, an iron-deficient diet, and genetic modifications inhibiting intracellular uptake of iron did not improve but rather exacerbated FSHD pathology in DUX4-Tg mice. Unexpectedly, however, iron supplementation, either from a high-iron diet or intravenous iron administration, resulted in remarkable improvement in grip strength and running performance in DUX4-Tg mice. Iron supplementation suppressed abnormal iron accumulation and the ferroptosis-related pathway involving increased lipid peroxidation in DUX4-Tg muscle. Muscle-specific DUX4 expression led to retinal vasculopathy, a part of FSHD pathology, which was prevented by iron administration. Furthermore, high-throughput compound screening of the ferroptosis pathway identified drug candidates including Ferrostatin-1 (Fer-1), a potent inhibitor of lipid peroxidation. Treatment with Fer-1 dramatically improved physical function in DUX4-Tg mice. Our findings demonstrate that DUX4-provoked toxicity is involved in the activation of the ferroptosis-related pathway and that supplementary iron could be a promising and readily available therapeutic option for FSHD.

2025-03-31 | GSE261617 | GEO

DUX4 activates germline genes, retroelements and immune-mediators: Implications for facioscapulohumeral dystrophy

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.

2012-01-03 | E-GEOD-33799 | biostudies-arrayexpress

Elevated Labile Iron Contributes to Membrane Repair Deficits in FSHD

Project description:Elevated Labile Iron Contributes to Membrane Repair Deficits in FSHD

| PRJNA1294895 | ENA

Model systems of DUX4 expression recapitulate the transcriptional profile of FSHD cells

Project description:Facioscapulohumeral dystrophy (FSHD) is caused by the mis-expression of the double-homeodomain transcription factor DUX4 in skeletal muscle cells. Many different cell culture models have been developed to study the pathophysiology of FSHD, frequently based on endogenous expression of DUX4 in FSHD cells or by mis-expression of DUX4 in control human muscle cells. Although results generated using each model are generally consistent, differences have also been reported, making it unclear which model(s) faithfully recapitulate DUX4 and FSHD biology. In this study, we systematically compared RNA-seq data generated from three different models of FSHD—lentiviral-based DUX4 expression in myoblasts, doxycycline-inducible DUX4 in myoblasts, and differentiated human FSHD myocytes expressing endogenous DUX4—and show that the DUX4-associated gene expression signatures of each dataset are highly correlated (Pearson’s correlation coefficient, r ~ 0.75-0.85). The few robust differences were attributable to different states of cell differentiation and other differences in experimental design. Our study describes a model system for inducible DUX4 expression that enables reproducible and synchronized experiments and validates the fidelity and FSHD relevance of multiple distinct models of DUX4 expression.

2016-09-21 | GSE85461 | GEO

SMCHD1 activates the expression of genes required for the expansion of human myoblasts (RNA-seq)

Project description:In human muscle, SMCHD1 mutations are associated with the onset of FSHD2, but the mechanism driving the disease onset remains unclear. A commonly accepted explanation is the loss of SMCHD1 binding to the D4Z4 locus activates the expression of DUX4 in FSHD2 muscle. In this study, we used human myoblasts having DUX4 non-permissive 4qB alleles as a model to study DUX4-independent functions of SMCHD1 on myoblast cell growth. Surprisingly, depletion of SMCHD1 in these cells resulted in a cell proliferation defect. Despite the absence of DUX4 target genes’ activation, these cells showed a repression of PAX7 target genes (a hallmark of FSHD) and similar changes in expression profile compared to FSHD myoblasts. Interestingly, downregulation of cell proliferation-related genes and dysregulation of fibroblasts-specific genes were observed in SMCHD1 knockdown myoblasts and FSHD2 myoblasts but not FSHD1 myoblasts. Additionally, we identified LAP2 as direct targets of SMCHD1. Depletion of LAP2 leads to cell proliferation defect similar to the effect after SMCHD1 knockdown. These data imply that DUX4 is not the only driver for the onset of FSHD, and SMCHD1 has DUX4-independent functions in muscle growth and development.

2024-06-25 | GSE190828 | GEO

SMCHD1 activates the expression of genes required for the expansion of human myoblasts (ChIP-seq)

2024-06-25 | GSE190829 | GEO

Analysis of genes regulated by DUX4 via oxidative stress reveals potential therapeutic targets for treatment of facioscapulohumeral dystrophy

Project description:Muscles of patients with facioscapulohumeral dystrophy (FSHD) are characterized by sporadic DUX4 expression and oxidative stress which is at least partially induced by DUX4 protein. Nevertheless, targeting oxidative stress with antioxidants has a limited impact on FSHD patients, and the exact role of oxidative stress in the pathology of FSHD, as well as its interplay with the DUX4 expression, remain unclear. Here we set up a screen for genes that are upregulated by DUX4 via oxidative stress with the aim to target these genes rather than the oxidative stress itself. Immortalized human myoblasts expressing DUX4 (MB135-DUX4) have an increased level of reactive oxygen species (ROS) and exhibit differentiation defects which can be reduced by treating the cells with classic (Tempol) or mitochondria-targeted antioxidants (SkQ1). The transcriptome analysis of antioxidant-treated MB135 and MB135-DUX4 myoblasts allowed us to identify 200 genes with expression deregulated by DUX4 but normalized upon antioxidant treatment. Several of these genes, including PITX1, have been already associated with FSHD and/or muscle differentiation. We confirmed that PITX1 was indeed deregulated in MB135-DUX4 cells and primary FSHD myoblasts and revealed a redox component in PITX1 regulation. PITX1 silencing partially reversed the differentiation defects of MB135-DUX4 myoblasts. Our approach can be used to identify and target redox-dependent genes involved in human diseases.

2021-05-04 | GSE173762 | GEO

DUX4 expression activates JNK and p38 MAP kinases in myoblasts

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.

2022-07-05 | MSV000089812 | MassIVE

DUX4-induced gene expression is the major molecular signature in FSHD skeletal muscle

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.

2014-07-03 | E-GEOD-56787 | biostudies-arrayexpress

DUX4 binding to retroelements creates promoters that are active in FSHD muscle and testis.

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.

2014-03-19 | E-GEOD-51041 | biostudies-arrayexpress

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