Project description:Mammalian hearts had the capability to regenerate cardiomyocyte and completely recover after heart injury within a limited time window after birth. It has been shown that sphingosine 1-phospahte receptor 1 (S1pr1) was highly expressed in cardiomyocytes and played an important role in heart development and pathological cardiac remodeling. Herein, we aim to investigate the role of CM-S1pr1 for cardiac regeneration and tissue repair after heart injury. We generated cardiomyocyte (CM)-specific S1pr1 knock-out mice and showed that CM-specific S1pr1 loss-of-function significantly severely reduced cardiomyocyte proliferation and heart regeneration in neonatal mice after both apex resection and myocardial infarction, whereas S1pr1 gain-of-function by AAV9-mediated CM-specific overexpression of S1pr1 significantly boosted cardiac regeneration and improved cardiac functions after heart injuries. We next identified that S1pr1 activated AKT/mTOR/CyclinD1 and Bcl-2 signaling pathways, and thus promoted cardiomyocyte proliferation and inhibited CM apoptosis, respectively.Of note, we applied CM-targeted gene therapy by AAV9-cTNT to specifically overexpress S1pr1 in cardiomyocytes and achieved an efficient S1pr1 overexpression in CMs in vivo. This CM-targeted strategy to overexpress S1pr1 significantly enhanced cardiac regeneration and improved cardiac functions after myocardial infarction in an adult mouse model, suggesting a potential strategy to boost adult cardiac regeneration in vivo.
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:Aims: Lower vertebrates and some neonatal mammals are known to possess the ability to regenerate cardiomyocyte and fully recover after heart injuries within a limited period. Understanding the molecular mechanisms of heart regeneration and exploring new ways to enhance cardiac regeneration hold significant promise for therapeutic intervention of heart failure. Sphingosine 1-phospahte receptor 1 (S1PR1) is highly expressed in cardiomyocytes and plays a crucial role in heart development and pathological cardiac remodeling. However, the effect of cardiomyocyte-expressing S1PR1 on heart regeneration has not yet been elucidated. This study aims to investigate the role of cardiomyocyte S1PR1 in cardiac regeneration following heart injuries. Methods and Results: We generated cardiomyocyte (CM)-specific S1pr1 knock-out mice and demonstrated that CM-specific S1pr1 loss-of-function severely reduced cardiomyocyte proliferation and inhibited heart regeneration following apex resection in neonatal mice. Conversely, AAV9-mediated CM-specific S1pr1 gain-of-function significantly enhanced cardiac regeneration. We identified that S1PR1 activated the AKT/mTORC1/CYCLIN D1 and BCL2 signaling pathways to promote cardiomyocyte proliferation and inhibit apoptosis. Moreover, CM-targeted gene delivery system via AAV9 to overexpress S1PR1 significantly increased cardiomyocyte proliferation and improved cardiac functions following myocardial infarction in adult mice, suggesting a potential method to enhance cardiac regeneration and improve cardiac function in the injured heart. Conclusions: This study demonstrates that CM-S1PR1 plays an essential role in cardiomyocyte proliferation and heart regeneration. This research provides a potential strategy by CM-targeted S1PR1 overexpression as a new therapeutic intervention for heart failure.
Project description:The mTOR (mammalian Target of Rapamycin) pathway is constitutively activated in Diffuse Large B-Cell Lymphoma (DLBCL). mTOR inhibition has been shown to have clinical activity in patients with DLBCL, although overall response rates remain low. We therefore evaluated differences in the transcriptome between DLBCL cell lines with differential sensitivity to the mTOR inhibitor Rapamycin, to (A) identify gene-expression patterns(GEP) capable of identifying sensitivity to Rapamycin, (B) understand the underlying mechanisms of resistance to Rapamycin in DLBCL and (C) identify bioactive molecules likely to synergize with mTOR inhibitors. Using Affymetrix HuGene ST 1.0 microarrays, we were able to identify a gene expression signature capable of accurately predicting sensitivity and resistance to Rapamycin in DLBCL cell lines. Pathway analysis identified the serine/threonine kinase Akt as central to the differentially-expressed gene network. Connectivity mapping of our datasets identified compounds targeting the AKT pathway with a high likelihood of reversing the GEP associated with resistance to Rapamycin. Specifically, we evaluated the HIV protease inhibitor (PI) Nelfinavir, which is known to have anti-cancer and Akt-inhibitory properties, as well as the small molecule Akt inhibitor MK-2206, for their potential to synergize with to Rapamycin in DLBCL. Nelfinavir and MK-2206 caused profound inhibition of cell viability in combination with Rapamycin in DLBCL cell lines. Low nanomolar concentrations of Rapamycin inhibited phosphorylation of Akt and also downstream targets of activated mTOR when used in combination with these Akt inhibitors. These findings have the potential to significantly improve patient selection for mTOR inhibitor therapy, and to improve rates and depths of response. More broadly, they support the use of global RNA expression and connectivity mapping to improve patient selection and identify synergistic drug combinations for cancer therapy. DLBCL cell lines were tested for Rapamycin sensitivity and classified as "sensitive" or "resistant." Genome-wide analysis of all cell lines were performed using the Affymetrix HuGene ST 1.0 Array Platform. Genes with differential expression between sensitive and resistant cell lines were analyzed using Statistical Analysis of Microarrays (SAM) software, and a signature of genes determnined. This signature was found to accurately predict sensitivity or resistance of other DLBCL cell lines, and to identify the protein kinase Akt as central to resistance.
Project description:The mTOR (mammalian Target of Rapamycin) pathway is constitutively activated in Diffuse Large B-Cell Lymphoma (DLBCL). mTOR inhibition has been shown to have clinical activity in patients with DLBCL, although overall response rates remain low. We therefore evaluated differences in the transcriptome between DLBCL cell lines with differential sensitivity to the mTOR inhibitor Rapamycin, to (A) identify gene-expression patterns(GEP) capable of identifying sensitivity to Rapamycin, (B) understand the underlying mechanisms of resistance to Rapamycin in DLBCL and (C) identify bioactive molecules likely to synergize with mTOR inhibitors. Using Affymetrix HuGene ST 1.0 microarrays, we were able to identify a gene expression signature capable of accurately predicting sensitivity and resistance to Rapamycin in DLBCL cell lines. Pathway analysis identified the serine/threonine kinase Akt as central to the differentially-expressed gene network. Connectivity mapping of our datasets identified compounds targeting the AKT pathway with a high likelihood of reversing the GEP associated with resistance to Rapamycin. Specifically, we evaluated the HIV protease inhibitor (PI) Nelfinavir, which is known to have anti-cancer and Akt-inhibitory properties, as well as the small molecule Akt inhibitor MK-2206, for their potential to synergize with to Rapamycin in DLBCL. Nelfinavir and MK-2206 caused profound inhibition of cell viability in combination with Rapamycin in DLBCL cell lines. Low nanomolar concentrations of Rapamycin inhibited phosphorylation of Akt and also downstream targets of activated mTOR when used in combination with these Akt inhibitors. These findings have the potential to significantly improve patient selection for mTOR inhibitor therapy, and to improve rates and depths of response. More broadly, they support the use of global RNA expression and connectivity mapping to improve patient selection and identify synergistic drug combinations for cancer therapy.
Project description:To investigate the functional and mechanistic roles of mTOR in zebrafish larvae fin regeneration, we firstly examined the spatiotemporal expression of mTOR in larvae fin and established a mTOR knockout (mTOR-KO) transgenic fish line using CRISPER / Cas9 gene editing technology. Moreover, mTOR was essential for the activation of macrophages, which is a key factor in maintaining the regenerative repair process. We also demonstrated that mTOR knockdown attenuated the proliferative capacity of bud embryo cell during the regenerative phase, while cell apoptosis was not affected. RNA-sequence analysis showed changes in mitochondrial function and dnm1l was identified as the main regulatory factor during the fin regeneration stage. We further suggested that mTOR may promote mitochondrial fission to support bud embryo cell regeneration via CaM-mTOR-dnm1l axis.
Project description:Background—YAP, the nuclear effector of Hippo signaling, regulates cellular growth and survival in multiple organs, including the heart, by interacting with TEAD sequence specific DNA-binding proteins. Recent studies showed that YAP stimulates cardiomyocyte proliferation and survival. However, the direct transcriptional targets through which YAP exerts its effects are poorly defined. Methods and Results—To identify genes directly regulated by YAP in cardiomyocytes, we combined differential gene expression analysis in YAP gain- and loss-of-function with genome-wide identification of YAP bound loci using chromatin immunoprecipitation and high throughput sequencing. This screen identified Pik3cb, encoding p110β, a catalytic subunit of phosphoinositol-3-kinase (PI3K), as a candidate YAP effector that promotes cardiomyocyte proliferation and survival. We validated YAP and TEAD occupancy of a conserved enhancer within the first intron of Pik3cb, and show that this enhancer drives YAP-dependent reporter gene expression. Yap gain- and loss-of-function studies indicated that YAP is necessary and sufficient to activate the PI3K-Akt pathway. Like Yap, Pik3cb gain-of-function stimulated cardiomyocyte proliferation, and Pik3cb knockdown dampened the YAP mitogenic activity. Reciprocally, Yap loss-of-function impaired heart function and reduced cardiomyocyte proliferation and survival, all of which were significantly rescued by AAV-mediated Pik3cb expression. Conclusion—Pik3cb is a crucial direct target of YAP, through which the YAP activates PI3K-AKT pathway and regulates cardiomyocyte proliferation and survival. Yap wild type ChIPseq and input
Project description:Zebrafish is capable of endogenously regenerating functional retina pigment epithelium (RPE) after widespread genetic ablation which involves a series of cellular and molecular events that remain to be defined. Here, using the RPE genetic ablation model in zebrafish, we observed that mTOR signaling was activated in the RPE cells post-ablation. Pharmacological and genetic inhibition of mTOR signaling impaired RPE regeneration, while activation of mTOR signaling benefited RPE recovery, suggesting mTOR signaling was required and sufficient for RPE regeneration post-ablation in zebrafish. We further identified an interesting crosstalk between mTOR signaling and microglia/macrophages during RPE regeneration that mTOR acts as an upstream regulator of microglia/macrophage infiltration to the injury site while microglia/macrophage, in turn, rainenforce mTOR activity.