Project description:Runx1 is a transcription factor that plays a key role in determining the proliferative and differential state of multiple cell types, during both development and adulthood. Here, we report how runx1 is specifically upregulated at the injury site during zebrafish heart regeneration, but unexpectedly, absence of runx1 results in enhanced regeneration. Using single cell sequencing, we found that the wild-type injury site consists of Runx1-positive endocardial cells and thrombocytes that express smooth muscle and collagen genes without differentiating into myofibroblasts. Both these populations are absent in runx1 mutants, resulting in a less collagenous and fibrinous scar. The reduction in fibrin in the mutant is further explained by reduced myofibroblast formation and by upregulation of components of the fibrin degradation pathway, including plasminogen receptor Annexin 2A as well as downregulation of plasminogen activator inhibitor serpine1 in myocardium and endocardium, resulting in increased levels of Plasminogen. In addition, this we also find enhanced myocardial proliferation as well as increased myocardial survival in the mutant. Our findings suggest that Runx1 controls the regenerative response of multiple cardiac cell-types and that targeting Runx1 is a novel therapeutic strategy to induce endogenous heart repair.
Project description:Runx1 is a transcription factor that plays a key role in determining the proliferative and differential state of multiple cell types, during both development and adulthood. Here, we report how Runx1 is specifically upregulated at the injury site during zebrafish heart regeneration, and that absence of runx1 results in increased myocardial survival and proliferation, and overall heart regeneration, accompanied by decreased fibrosis. Using single cell sequencing, we found that the wild-type injury site consists of Runx1-positive endocardial cells and thrombocytes that induce expression of smooth muscle and collagen genes. Both these populations cannot be identified in runx1 mutant wounds that contain less collagen and fibrin. The reduction in fibrin in the mutant is further explained by reduced myofibroblast formation and upregulation of components of the fibrin degradation pathway, including plasminogen receptor annexin 2A as well as downregulation of plasminogen activator inhibitor serpine1 in myocardium and endocardium, resulting in increased levels of plasminogen. Our findings suggest that Runx1 controls the regenerative response of multiple cardiac cell types and that targeting Runx1 is a novel therapeutic strategy for inducing endogenous heart repair.
Project description:Hypertrophic scarring (HS) is characterized by excessive extracellular matrix deposition, matrix metalloprotein gene activation, and fibroblast invasive growth. However, the methylation level of hypertrophic scarring is poorly understood. Genome wide DNA methylation profiling of normal skin and hypertrophic scar. The Illumina Infinium Methylation EPIC BeadChip (850K) was used to obtain DNA methylation profiles across approximately 853,307 CpGs in liquid based scar samples. Samples included 6 normal skin, and 6 hypertrophic scar.
Project description:To test the ability of the Automated Spatially Targeted Optical Micro Proteomics (AutoSTOMP) protocol to selectively biotinylate structures of interest within tissue sections we first examined a rat myocardial infarction model. In this model, trauma caused by ligation and infiltrating immune cells causes fibroblast activation and deposition of scar tissue that ultimately impairs cardiac function. Macrophages are thought to play a role in inflammatory regulation and damaged cell turnover in the tissue. We decide to grab the proteome of the macrophage rich regions.
Project description:Aneuploidy and structural aberrations affecting chromosome 21 (Hsa21) are the most frequent in cytogentic events in acute myeloid leukemia. However, it remains unclear why leukemic blasts select for amplifications of Hsa21 or parts of it and why children with Down syndrome (i.e. trisomy 21) are at a high risk of developing leukemia. Here, we propose that disequilibrium of the RUNX1 isoforms and resultant RUNX1A dominance are key to trisomy 21-associated leukemogenesis. Using a Hsa21-focussed CRISPR-Cas9 screen, we uncovered a strong and specific RUNX1 dependency in myeloid leukemia associated with Down syndrome (ML-DS). High levels of RUNX1A – as seen in ML-DS – synergized with the pathognomonic Gata1s mutation in ML-DS pathogenesis, an effect that was reversed upon restoration of the normal RUNX1A:RUNX1C equilibrium. Mechanistically, RUNX1A displaces RUNX1C from its endogenous binding sites and recruits the MYC cofactor MAX to induce oncogenic programs and perturb normal differentiation. This presents a therapeutic vulnerability that can be exploited by interfering with MYC:MAX dimerization. Our study highlights the importance of alternative splicing in leukemogenesis, and paves the way for developing specific and targeted therapies for ML-DS as well as for other leukemias with Hsa21 aneuploidy or RUNX1 isoform disequilibrium.
Project description:The adult mammalian heart heals after myocardial infarction (MI) by deposition of scar tissue, leading to downstream arrhythmia, remodelling and heart failure1. In contrast, adult zebrafish and neonatal mouse hearts are capable of regenerating after injury. Macrophages are key mediators of tissue repair and appear to be required for both regeneration and healing by scar formation, but the mechanisms underlying these distinct roles are poorly understood2-4. Here we investigated how macrophages differentially influence the mode of repair by determining their responses in scar-free versus scar-induced healing, comparing ventricular resection with cryo-injured adult zebrafish hearts and neonatal versus adult mouse hearts after MI. Unbiased transcriptomics revealed molecular programmes implicating macrophages in the initiation and resolution of inflammation to dictate the kinetics of scarring during zebrafish regeneration and the activation of direct and indirect pathways to drive fibrosis in the adult mouse heart. Most notably we observed up-regulation of collagen isoforms in both zebrafish and mouse macrophages following injury. Adoptive transfer of macrophages, from resected zebrafish hearts into cryo-injured hosts and splenic monocyte-derived macrophages from adult mouse donors into neonatal hearts, enhanced scar formation and induced fibrosis, respectively, via cell autonomous production of collagen. In zebrafish, macrophage-specific targeting of collagen 4a binding protein and cognate collagen 4a1 followed by transfer led to significantly reduced scarring in cryo-injured hosts, as further evidence of a direct macrophage contribution to collagen deposition and scar formation. These findings contrast with the current model of scarring, whereby collagen is laid down exclusively by myofibroblasts, and implicate macrophages as critical regulators of heart repair.
Project description:The mammalian heart possesses a poor ability to regenerate after acute ischemic cardiac injury and lost cardiac muscle is replaced by scar tissue. Multiple clinical studies demonstrate that the size of scar tissue following myocardial infarction is an independent predictor of cardiovascular outcomes, yet little is known about factors that regulate the size of scar after ischemic cardiac injury. In this report, we demonstrate that collagen V, a fibrillar collagen and a minor constituent of heart scars regulates the size of heart scars after ischemic cardiac injury. Depletion of collagen V in heart scars in two independent animal models led to a significant and paradoxical increase in post infarction scar tissue size with worsening of heart function. A systems genetics approach analyzing genes versus traits across 100 in-bred strains of mice independently demonstrated that collagen V is a critical driver of post injury heart function. We show that collagen V deficiency alters the ultra-structure and mechanical properties of scar tissue that make it more vulnerable to expansion. There is altered reciprocal feedback between matrix and cells that induce expression of specific mechanosensitive integrins which drive fibroblast activation and increased ECM gene expression. Scar size increases. Administration of cilengitide, an inhibitor of specific integrins, completely rescues the phenotype of increased post injury scarring, myofibroblast formation and cardiac dysfunction in collagen V deficient mice. These observations demonstrate that collagen V, a structural constituent of heart scar tissue regulates scar size in an integrin dependent manner.
Project description:The mammalian heart possesses a poor ability to regenerate after acute ischemic cardiac injury and lost cardiac muscle is replaced by scar tissue. Multiple clinical studies demonstrate that the size of scar tissue following myocardial infarction is an independent predictor of cardiovascular outcomes, yet little is known about factors that regulate the size of scar after ischemic cardiac injury. In this report, we demonstrate that collagen V, a fibrillar collagen and a minor constituent of heart scars regulates the size of heart scars after ischemic cardiac injury. Depletion of collagen V in heart scars in two independent animal models led to a significant and paradoxical increase in post infarction scar tissue size with worsening of heart function. A systems genetics approach analyzing genes versus traits across 100 in-bred strains of mice independently demonstrated that collagen V is a critical driver of post injury heart function. We show that collagen V deficiency alters the ultra-structure and mechanical properties of scar tissue that make it more vulnerable to expansion. There is altered reciprocal feedback between matrix and cells that induce expression of specific mechanosensitive integrins which drive fibroblast activation and increased ECM gene expression. Scar size increases. Administration of cilengitide, an inhibitor of specific integrins, completely rescues the phenotype of increased post injury scarring, myofibroblast formation and cardiac dysfunction in collagen V deficient mice. These observations demonstrate that collagen V, a structural constituent of heart scar tissue regulates scar size in an integrin dependent manner.
Project description:Canonical roles for macrophages in mediating the fibrotic response after a heart attack (myocardial infarction) include turnover of the extracellular matrix and activation of cardiac fibroblasts to initiate collagen deposition. Here we reveal through studying the functional kinetics of fibrosis during zebrafish heart regeneration and mouse heart repair that macrophages can directly contribute collagen to the forming scar. Unbiased transcriptomics revealed an up-regulation of collagen isoforms in both zebrafish and mouse macrophages following injury. Adoptive transfer of macrophages from collagen-tagged transgenic zebrafish and splenic monocyte-derived macrophages from adult mouse GFPtpz-collagen donors, enhanced scar formation and induced fibrosis, respectively, via cell autonomous production of collagen. In zebrafish, macrophage-specific targeting of collagen 4a binding protein and cognate collagen 4a1 followed by transfer led to significantly reduced scarring in cryo-injured hosts. These findings contrast with the current model of scarring whereby collagen deposition is exclusively attributed to myofibroblasts, and implicate macrophages as direct contributors to fibrosis during heart repair.