Project description:Matrix stiffness is a central regulator of fibroblast function. However, the transcriptional mechanisms linking matrix stiffness to changes in fibroblast phenotype are incompletely understood. Here, we evaluated the effect of matrix stiffness on genome-wide chromatin accessibility in freshly-isolated lung fibroblasts using ATAC-seq. We found higher matrix stiffness profoundly increased global chromatin accessibility relative to lower matrix stiffness, and these alterations were in close genomic proximity to known pro-fibrotic gene programs. Motif analysis of these regulated genomic loci identified ZNF416 as a putative mediator of fibroblast stiffness responses. Genome occupancy analysis using ChIP-seq confirmed that ZNF416 occupies a broad range of genes implicated in fibroblast activation and tissue-fibrosis, with relatively little overlap in genomic occupancy with other mechanoresponsive and pro-fibrotic transcriptional regulators. Using loss and gain of function studies we demonstrated that ZNF416 plays a critical role in fibroblast proliferation, extracellular matrix synthesis and contractile function. Together these observations identify ZNF416 as novel mechano-activated transcriptional regulator of fibroblast biology.
Project description:Matrix stiffness is a central regulator of fibroblast function. However, the transcriptional mechanisms linking matrix stiffness to changes in fibroblast phenotype are incompletely understood. Here, we evaluated the effect of matrix stiffness on genome-wide chromatin accessibility in freshly-isolated lung fibroblasts using ATAC-seq. We found higher matrix stiffness profoundly increased global chromatin accessibility relative to lower matrix stiffness, and these alterations were in close genomic proximity to known pro-fibrotic gene programs. Motif analysis of these regulated genomic loci identified ZNF416 as a putative mediator of fibroblast stiffness responses. Genome occupancy analysis using ChIP-seq confirmed that ZNF416 occupies a broad range of genes implicated in fibroblast activation and tissue-fibrosis, with relatively little overlap in genomic occupancy with other mechanoresponsive and pro-fibrotic transcriptional regulators. Using loss and gain of function studies we demonstrated that ZNF416 plays a critical role in fibroblast proliferation, extracellular matrix synthesis and contractile function. Together these observations identify ZNF416 as novel mechano-activated transcriptional regulator of fibroblast biology.
Project description:In diseased organs, stress-activated signaling cascades alter chromatin, triggering maladaptive cell state transitions. Fibroblast activation is a common tissue stress response that worsens lung, liver, kidney and heart disease, yet its mechanistic basis remains obscure. Pharmacologic BET inhibition alleviates cardiac dysfunction, providing a tool to interrogate and modulate cardiac cell states as a potential therapeutic approach. Here, we leverage single-cell epigenomic interrogation of hearts dynamically exposed to BET inhibitors to reveal a reversible transcriptional switch underlying fibroblast activation. Resident cardiac fibroblasts demonstrated robust toggling between the quiescent and activated state in a manner directly correlating with BET inhibitor exposure and cardiac function. Single-cell chromatin accessibility revealed novel DNA elements whose accessibility dynamically correlated with cardiac performance. Among the most dynamic elements was an enhancer regulating the transcription factor MEOX1, which was specifically expressed in activated fibroblasts, occupied putative regulatory elements of a broad fibrotic gene program, and was required for TGFβ-induced fibroblast activation. Selective CRISPR inhibition of the single most dynamic cis-element within the enhancer blocked TGFβ-induced Meox1 activation. We identify MEOX1 as a central regulator of fibroblast activation associated with cardiac dysfunction, and also demonstrate its upregulation upon activation of human lung, liver and kidney fibroblasts. The plasticity and specificity of BET-dependent regulation of MEOX1 in tissue fibroblasts provide new trans- and cis- targets for treating fibrotic disease.
Project description:<p>Renal fibrosis, a hallmark of chronic kidney diseases, is driven by the activation of renal fibroblasts. Recent studies have highlighted the role of glycolysis in this process. Nevertheless, one critical glycolytic activator, 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), remains unexplored in renal fibrosis. Upon reanalyzing the single-cell sequencing data from Dr. Humphreys' lab, we noticed an upregulation of glycolysis, gluconeogenesis, and TGFβ signaling pathway in myofibroblasts from fibrotic kidneys after unilateral ureter obstruction (UUO) or kidney ischemia/reperfusion. Furthermore, our experiments showed significant induction of PFKFB3 in mouse kidneys following UUO or kidney ischemia/reperfusion. To delve deeper into the role of PFKFB3, we generated mice with Pfkfb3 deficiency specifically in myofibroblasts (Pfkfb3f/fPostnMCM). Following UUO or kidney ischemia/reperfusion, a substantial decrease of fibrosis in injured kidneys of Pfkfb3f/fPostnMCM mice was identified compared to their wild-type littermates. Additionally, in cultured renal fibroblast NRK-49F cells, PFKFB3 was elevated upon exposure to TGFβ1, accompanied by the increase of α-SMA and fibronectin. Notably, this upregulation was significantly diminished with PFKFB3 knockdown, correlated with a glycolysis suppression. Mechanistically, the glycolytic metabolite lactate promoted the fibrotic activation of NRK-49F. In conclusion, our study demonstrates the critical role of PFKFB3 in driving fibroblast activation and subsequent renal fibrosis.</p>
Project description:Tissue fibrosis is a chronic disease driven by persistent fibroblast activation that has recently been linked to epigenetic modifications. Here, we screened a small library of epigenetic small-molecule modulators to identify compounds capable of inhibiting or reversing TGFβ-mediated fibroblast activation. We identified pracinostat, an HDAC inhibitor, as a potent attenuator of lung fibroblast activation and confirmed its efficacy in patient-derived fibroblasts isolated from fibrotic lung tissue. Mechanistically, we found that HDAC-dependent transcriptional repression was an early and essential event in TGFβ-mediated fibroblast activation. Treatment of lung fibroblasts with pracinostat broadly attenuated TGFβ-mediated epigenetic repression and promoted fibroblast quiescence. We confirmed a specific role for HDAC-dependent histone deacetylation in the promoter region of the anti-fibrotic gene PPARGC1A (PGC1α) in response to TGFβ stimulation. Finally, we identified HDAC7 as a key factor whose RNAi-mediated knockdown attenuates fibroblast activation without altering global histone acetylation. Together these results provide novel mechanistic insight into the essential role HDACs play in TGFβ-mediated fibroblast activation via targeted gene repression.