ABSTRACT
Overactivation of the transforming growth factor-ß (TGFß) signaling in Duchenne muscular dystrophy (DMD) is a major hallmark of disease progression, leading to fibrosis and muscle dysfunction. Here, we investigated the role of SETDB1 (SET domain, bifurcated 1), a histone lysine methyltransferase involved in muscle differentiation. Our data show that, following TGFß induction, SETDB1 accumulates in the nuclei of healthy myotubes while being already present in the nuclei of DMD myotubes where TGFß signaling is constitutively activated. Transcriptomics revealed that depletion of SETDB1 in DMD myotubes leads to down-regulation of TGFß target genes coding for secreted factors involved in extracellular matrix remodeling and inflammation. Consequently, SETDB1 silencing in DMD myotubes abrogates the deleterious effect of their secretome on myoblast differentiation by impairing myoblast pro-fibrotic response. Our findings indicate that SETDB1 potentiates the TGFß-driven fibrotic response in DMD muscles, providing an additional axis for therapeutic intervention.
Subject(s)
Histone-Lysine N-Methyltransferase , Muscle Fibers, Skeletal , Muscular Dystrophy, Duchenne , Signal Transduction , Transforming Growth Factor beta , Muscular Dystrophy, Duchenne/metabolism , Muscular Dystrophy, Duchenne/genetics , Muscular Dystrophy, Duchenne/pathology , Histone-Lysine N-Methyltransferase/metabolism , Histone-Lysine N-Methyltransferase/genetics , Muscle Fibers, Skeletal/metabolism , Muscle Fibers, Skeletal/pathology , Transforming Growth Factor beta/metabolism , Humans , Animals , Cell Differentiation , Mice , Myoblasts/metabolism , Fibrosis , Gene Expression RegulationABSTRACT
In mammals, males and females show marked differences in immune responses. Males are globally more sensitive to infectious diseases, while females are more susceptible to systemic autoimmunity. X-chromosome inactivation (XCI), the epigenetic mechanism ensuring the silencing of one X in females, may participate in these sex biases. We perturbed the expression of the trigger of XCI, the noncoding RNA Xist, in female mice. This resulted in reactivation of genes on the inactive X, including members of the Toll-like receptor 7 (TLR7) signaling pathway, in monocyte/macrophages and dendritic and B cells. Consequently, female mice spontaneously developed inflammatory signs typical of lupus, including anti-nucleic acid autoantibodies, increased frequencies of age-associated and germinal center B cells, and expansion of monocyte/macrophages and dendritic cells. Mechanistically, TLR7 signaling is dysregulated in macrophages, leading to sustained expression of target genes upon stimulation. These findings provide a direct link between maintenance of XCI and female-biased autoimmune manifestations and highlight altered XCI as a cause of autoimmunity.
