Project description:By using transgenic zebrafish lines Tg(nxk2.5:GFP) (Witzel et al. 2012) and Tg(myl7:EGFP) (D'Amico et al. 2007), we have characterized transcriptomic profile of FACS-isolated CM (GFP+) from developing zebrafish heart at 24, 48 and 72 hpf, corresponding to heart tube formation, chamber formation and differentiation and heart maturation, respectively. GFP- cells were used as a control. We have identified cardiac regulatory networks playing a crucial role in heart morphogenesis. To validate their importance in heart development, we employed zebrafish mutants of cardiac transciption factors Gata5, Hand2 and Tbx5a, the disruption of which were previously linked to impaired migration of the cardiac primordia to the embryonic midline, reduced number of myocardial precursors and failure of heart looping, respectively (Reiter et al. 1999; Yelon et al. 2000; Garrity et al. 2002). RNA-seq was performed from homozygous gata5tm236a/tm236a, tbx5am21/ m21, hand2s6/s6 mutant 72 hpf embryos in Tg(myl7:EGFP) genetic background. Homozygous mutant embryos for analyses were selected on the basis of their phenotypes of cardia bifida (gata5tm236a/tm236a, hand2s6/s6) or heart-string (tbx5am21/ m21) .
Project description:By using transgenic zebrafish lines Tg(nxk2.5:GFP) (Witzel et al. 2012) and Tg(myl7:EGFP) (D'Amico et al. 2007), we have characterized chromatin accessibility of FACS-isolated CM (GFP+) from developing zebrafish heart at 24, 48 and 72 hpf, corresponding to heart tube formation, chamber formation and differentiation and heart maturation, respectively. GFP- cells were used as a control. We have identified cardiac regulatory networks playing a crucial role in heart morphogenesis. To validate their importance in heart development, we employed zebrafish mutants of cardiac transciption factors Gata5, Hand2 and Tbx5a, the disruption of which were previously linked to impaired migration of the cardiac primordia to the embryonic midline, reduced number of myocardial precursors and failure of heart looping, respectively (Reiter et al. 1999; Yelon et al. 2000; Garrity et al. 2002). ATAC-seq was performed from homozygous gata5tm236a/tm236a, tbx5am21/ m21, hand2s6/s6 mutant 72 hpf embryos in Tg(myl7:EGFP) genetic background. Homozygous mutant embryos for analyses were selected on the basis of their phenotypes of cardia bifida (gata5tm236a/tm236a, hand2s6/s6) or heart-string (tbx5am21/ m21) .
Project description:Ischemic cardiopathy is the leading cause of death in the world, for which efficient regenerative therapy is not currently available. In mammals, after a myocardial infarction episode, the damaged myocardium is replaced by scar tissue featuring collagen deposition and tissue remodelling with negligible cardiomyocyte proliferation. Zebrafish, in contrast, display an extensive regenerative capacity as they are able to restore completely lost cardiac tissue after partial ventricular amputation. Due to the lack of genetic lineage tracing evidence, it is not yet clear if new cardiomyocytes arise from existing contractile cells or from an uncharacterised set of progenitors cells. Nonetheless, several genes and molecules have been shown to participate in this process, some of them being cardiomyocyte mitogens in vitro. Though questions as what are the early signals that drive the regenerative response and what is the relative role of each cardiac cell in this process still need to be answered, the zebrafish is emerging as a very valuable tool to understand heart regeneration and devise strategies that may be of potential value to treat human cardiac disease. Here, we performed a genome-wide transcriptome profile analysis focusing on the early time points of zebrafish heart regeneration and compared our results with those of previously published data. Our analyses confirmed the differential expression of several transcripts, and identified additional genes the expression of which is differentially regulated during zebrafish heart regeneration. We validated the microarray data by conventional and/or quantitative RT-PCR. For a subset of these genes, their expression pattern was analyzed by in situ hybridization and shown to be upregulated in the regenerating area of the heart. The specific role of these new transcripts during zebrafish heart regeneration was further investigated ex vivo using primary cultures of zebrafish cardiomyocytes and/or epicardial cells. Our results offer new insights into the biology of heart regeneration in the zebrafish and, together with future experiments in mammals, may be of potential interest for clinical applications. In order to study zebrafish heart regeneration, a time course experiment was realized where amputated heart regenerating were compared to control heart. Samples in triplicate were extracted at 1, 3, 5 and 7 days post-amputation.
Project description:During heart regeneration in the zebrafish, fibrotic tissue is replaced by newly formed cardiomyocytes derived from pre-existing ones. It is unclear whether the heart is comprised of several cardiomyocyte populations bearing different capacity to replace lost myocardium. Here, using sox10 genetic fate mapping, we identified a subset of pre-existent cardiomyocytes in the adult zebrafish heart with a distinct gene expression profile that expanded massively after cryoinjury. Genetic ablation of sox10+ cardiomyocytes severely impaired cardiac regeneration revealing that they play a crucial role for heart regeneration.
Project description:For a short period of time in mammalian neonates, the mammalian heart can regenerate via cardiomyocyte proliferation. This regenerative capacity is largely absent in adults. In other organisms, including zebrafish, damaged hearts can regenerate throughout their lifespans. Many studies have been performed to understand the mechanisms of cardiomyocyte de-differentiation and proliferation during heart regeneration however, the underlying reason why adult zebrafish and young mammalian cardiomyocytes are primed to enter cell cycle have not been identified. Here we show the primed state of a pro-regenerative cardiomyocyte is dictated by its amino acid profile and metabolic state. Adult zebrafish cardiomyocyte regeneration is a result of amino acid-primed mTOR activation. Zebrafish and neonatal mouse cardiomyocytes display elevated glutamine levels, predisposing them to amino acid-driven activation of mTORC1. Injury initiates Wnt/β-catenin signalling that instigates primed mTORC1 activation, Lin28 expression and metabolic remodeling necessary for zebrafish cardiomyocyte regeneration. These studies reveal a unique mTORC1 primed state in zebrafish and mammalian regeneration competent cardiomyocytes.
Project description:Unlike human hearts, zebrafish hearts efficiently regenerate after injury. Regeneration is driven by the strong proliferation response of its cardiomyocytes to injury. In this study, we show that active telomerase is required for cardiomyocyte proliferation and full organ recovery, supporting the potential of telomerase therapy as a means of stimulating cell proliferation upon myocardial infarction. Heart transcriptomes of WT and telomerase defective adult zebrafish animals were profiled by RNASeq, in control conditions and 3 days after heart cryoinjury.
Project description:Ischemic cardiopathy is the leading cause of death in the world, for which efficient regenerative therapy is not currently available. In mammals, after a myocardial infarction episode, the damaged myocardium is replaced by scar tissue featuring collagen deposition and tissue remodelling with negligible cardiomyocyte proliferation. Zebrafish, in contrast, display an extensive regenerative capacity as they are able to restore completely lost cardiac tissue after partial ventricular amputation. Due to the lack of genetic lineage tracing evidence, it is not yet clear if new cardiomyocytes arise from existing contractile cells or from an uncharacterised set of progenitors cells. Nonetheless, several genes and molecules have been shown to participate in this process, some of them being cardiomyocyte mitogens in vitro. Though questions as what are the early signals that drive the regenerative response and what is the relative role of each cardiac cell in this process still need to be answered, the zebrafish is emerging as a very valuable tool to understand heart regeneration and devise strategies that may be of potential value to treat human cardiac disease. Here, we performed a genome-wide transcriptome profile analysis focusing on the early time points of zebrafish heart regeneration and compared our results with those of previously published data. Our analyses confirmed the differential expression of several transcripts, and identified additional genes the expression of which is differentially regulated during zebrafish heart regeneration. We validated the microarray data by conventional and/or quantitative RT-PCR. For a subset of these genes, their expression pattern was analyzed by in situ hybridization and shown to be upregulated in the regenerating area of the heart. The specific role of these new transcripts during zebrafish heart regeneration was further investigated ex vivo using primary cultures of zebrafish cardiomyocytes and/or epicardial cells. Our results offer new insights into the biology of heart regeneration in the zebrafish and, together with future experiments in mammals, may be of potential interest for clinical applications.