Project description:Mitochondrial dynamics and mitophagy are intimately linked physiological processes that are essential for cardiac homeostasis. Here we show that cardiac Klf9 is dysregulated in human and rodent cardiomyopathy. Young adult global Klf9-knockout mice displayed hypertrophic cardiomyopathy that was characterized by depressed systolic function, increased left ventricular mass and pulmonary congestion. Klf9 knockout led to mitochondrial disarray and fragmentation in cardiomyocytes. Biochemical analysis confirmed that mitochondrial respiratory function was impaired in Klf9-knockout cardiomyocytes, with reduced myocardial ATP levels and elevated ROS. Furthermore, cardiac-specific Klf9-deficient mice phenocopied global Klf9-knockout mice, suggesting that cardiac Klf9 is essential for mitochondrial homeostasis and heart function. Moreover, cardiac Klf9 deficiency inhibited mitophagy induced by angiotensin II (ANGII), thereby leading to accumulation of dysfunctional mitochondria and acceleration of heart failure in mice in response to ANGII treatment. In contrast, cardiac-specific Klf9 transgene improved cardiac systolic function via promoting mitophagy in mice in response to ANGII treatment. Molecular mechanism studies indicated that Klf9 knockout decreased the expression of PGC-1α and its target genes involved in mitochondrial energy metabolism. Moreover, Klf9 controlled the expression of Mfn2 by directly binding to its promoter region, thereby regulating mitochondrial dynamics and mitophagy. Finally, we performed Mfn2 rescue experiments in Klf9-CKO mice and found that AAV-mediated Mfn2 rescue in heart improved cardiac mitochondrial and systolic function in Klf9-CKO mice treated with or without ANGII. Thus, Klf9 integrates cardiac energy metabolism, mitochondrial dynamics and mitophagy. Modulating Klf9 activity may have therapeutic potential in the treatment of heart failure.
Project description:DEAD box 17 (DDX17) is a typical member of the DEAD box family with transcriptional cofactor activity. Although DDX17 is abundantly expressed in the myocardium, its role in the heart is not fully understood. We generated cardiomyocyte-specific Ddx17-knockout mice and cardiomyocyte-specific Ddx17 transgenic mice and explored the function of DDX17 using various cardiomyocyte injury and heart failure (HF) models. We also validated the correlation between DDX17 expression and cardiac function in myocardial biopsy samples from HF patients. DDX17 was downregulated in myocardial samples from HF mouse models and cardiomyocyte injury models. We found that the cardiomyocyte-specific knockout of DDX17 promotes autophagic flux blockage and cardiomyocyte apoptosis in pathological conditions, resulting in progressive heart dysfunction, thereby leading to maladaptive remodeling and progression of HF. The replenishment of DDX17 in cardiomyocytes protected heart function in pathological conditions. Further studies showed that DDX17 can bind to the transcriptional repressor BCL6 and inhibit the expression of the mitochondrial fission protein DRP1. When DDX17 expression was decreased, the transcriptional repression of BCL6 was reduced, resulting in increased DRP1 expression and mitochondrial fission, which caused autophagy flux blockage and apoptosis in cardiomyocytes, leading to impaired mitochondrial homeostasis and HF. We also verified the clinical correlation of DDX17 expression with cardiac function and DRP1 expression in endomyocardial biopsies from patients with HF. These findings suggest that DDX17 protects cardiac function by promoting mitochondrial homeostasis through the BCL6-DRP1 pathway during HF.
Project description:Endothelial cell dysfunction plays an essential role in the process of cardiac ischemia-reperfusion (I/R) injury. Mitochondria damage, which can trigger inflammasome activation and subsequent pyroptosis, perturbs endothelial homeostasis, leading to aggravated cardiac I/R injury. Sphingosine 1-phosphate (S1P), a bioactive lipid molecule, exerts multifaceted effect on I/R injury via its different S1P receptors. However, the effect of EC-expressing S1P receptors on endothelial dysfunction, mitochondrial damage-induced inflammasome activation and consequent pyroptosis during cardiac I/R injury remain unclear. Our findings suggest a pivotal role of EC-expressing S1PR2 to control EC mitochondrial homeostasis and demonstrate that S1PR2-meidated mitochondrial dysfunction can trigger inflammasome activation and pyroptosis in ECs, which significantly influences inflammatory responses and heart injuries following I/R.
Project description:Adult-onset diseases can be associated with in utero events, but mechanisms for such temporally distant dysregulation of organ function remain unknown. The polycomb histone methyltransferase, Ezh2, stabilizes transcription by depositing repressive histone marks during development that persist into adulthood, but the function of Ezh2-mediated transcriptional stability in postnatal organ homeostasis is not understood. Here, we show that Ezh2 stabilizes the postnatal cardiac gene expression program and prevents cardiac pathology, primarily by repressing the homeodomain transcription factor Six1 in differentiating cardiac progenitors. Loss of Ezh2 in embryonic cardiac progenitors, but not in differentiated cardiomyocytes, resulted in postnatal cardiac pathology, including cardiomyocyte hypertrophy and fibrosis. Loss of Ezh2 caused broad derepression of skeletal muscle genes, including the homeodomain transcription factor Six1, which is expressed in cardiac progenitors but is normally silenced upon cardiac differentiation. Many of the deregulated genes are direct Six1 targets, implying a critical requirement for stable repression of Six1 in cardiac myocytes. Indeed, upon de-repression, Six1 promotes cardiac pathology, as it was sufficient to induce cardiac hypertrophy. Furthermore, genetic reduction of Six1 levels almost completely rescued the pathology of Ezh2-deficient hearts. Thus, repression of a single transcription factor in cardiac progenitors by Ezh2 is essential for stability of the adult heart gene expression program and homeostasis. Our results suggest that epigenetic dysregulation during discrete developmental windows can predispose to adult disease and dysregulated stress responses. Global gene expression profiles of Ezh2-deficient hearts. The right ventricle and the interventricular septum of five wild type (Ezh2f/f) and four Ezh2-deficient (Ezh2f/f;Mef2cAHF::Cre) mice were analyzed.
Project description:Endothelial cell dysfunction plays an essential role in the process of cardiac ischemia-reperfusion (I/R) injury. Mitochondria damage, which can trigger inflammasome activation and subsequent pyroptosis, perturbs endothelial homeostasis, leading to aggravated cardiac I/R injury. Sphingosine 1-phosphate (S1P), a bioactive lipid molecule, exerts multifaceted effect on I/R injury via its different S1P receptors. However, the effect of EC-expressing S1P receptors on endothelial dysfunction, mitochondrial damage-induced inflammasome activation and consequent pyroptosis during cardiac I/R injury remain unclear. Our findings suggest a pivotal role of EC-expressing S1PR2 to control EC mitochondrial homeostasis and demonstrate that S1PR2-meidated mitochondrial dysfunction can trigger inflammasome activation and pyroptosis in ECs, which significantly influences inflammatory responses and heart injuries following I/R.
Project description:Clinically, cardiac dysfunction is a key component of sepsis-induced multi-organ failure. Mitochondrial function is essential for cardiomyocyte homeostasis as disrupted mitochondrial dynamics enhances mitophagy and apoptosis. However, therapies targeted to improve mitochondrial function in septic patients have not been explored. Our research is helpful to understand the role of cardiomyocyte PPARα in LPS-induced cardiac dysfunction
Project description:To identify putative target genes of the transcription factor Klf9 in primary keratinocytes we over-expressed Klf9 in these cells using a lentiviral delivery system. We detected several hundred genes that show differential expression levels following ectopic Klf9 expression including several genes that are involved in proliferation and cell cycle control. These results allow insights into the mechanisms by which Klf9 regulates proliferation in primary keratinocytes. Primary human neonatal foreskin keratinocytes were infected with equal viral titers of a GFP and KLF9 expression construct, respectively. Cells were harvested 2,4 and 7 days after infection and total RNA was used to perform whole genome microarray analysis.
Project description:Kruppel-like factor 9 (Klf9), a zinc-finger transcription factor, is implicated in the control of cell proliferation, cell differentiation and cell fate in brain and uterus. Using Klf9 null mutant mice, we have investigated the involvement of Klf9 in small intestine crypt-villus cell renewal and lineage determination. We report the predominant expression of Klf9 gene in small intestine smooth muscle (muscularis externa). Jejunums null for Klf9 have shorter villi, reduced crypt stem/transit cell proliferation, and altered lineage determination as indicated by decreased and increased numbers of Goblet and Paneth cells, respectively. A stimulatory role for Klf9 in villus cell migration was demonstrated by BrdU labeling. Results suggest that Klf9 controls the elaboration, from small intestine smooth muscle, of molecular mediator(s) of crypt cell proliferation and lineage determination, and of villus cell migration. Experiment Overall Design: Total RNA was extracted in parallel from the jejunums of five WT and five Klf9-/- male mice (PND 30) using TRIzol reagent (Invitrogen, Carlsbad, CA). Conversion of each RNA preparation to corresponding fragmented cRNA. Fifteen ug of each cRNA was hybridized for 16 hours to an Affymetrix mouse 430A GeneChip. Ten GeneChips (each corresponding to a single animal) were hybridized, washed and scanned in parallel. Following the wash, signal amplification, and signal detection steps, GeneChips were scanned (Agilent GeneArray laser scanner) and the resultant images quantified using Affymetrix MAS 5.0 software.
Project description:Mitochondrial and lysosomal functions are intimately linked and are critical for cellular homeostasis, as evidenced by the fact that cellular senescence, aging, and multiple prominent diseases are associated with concomitant dysfunction of both organelles. However, it is not well understood how the two important organelles are regulated. Transcription factor EB (TFEB) is the master regulator of lysosomal function and is also implicated in regulating mitochondrial function; however, the mechanism underlying the maintenance of both organelles remains to be fully elucidated. Here, by comprehensive transcriptome analysis and subsequent chromatin immunoprecipitation sequencing (ChIP)-quantitative PCR (qPCR), we identified hexokinase domain containing 1 (HKDC1), which is known to function in the glycolysis pathway as a direct TFEB target. Moreover, HKDC1 was upregulated in both mitochondrial and lysosomal stress in a TFEB-dependent manner, and its function was critical for the maintenance of both organelles under stress conditions. Mechanistically, the TFEB–HKDC1 axis was essential for PINK1/Parkin-dependent mitophagy via its initial step, PINK1 stabilization. In addition, the functions of HKDC1 and voltage-dependent anion channels (VDACs), with which HKDC1 interacts, were essential for the clearance of damaged lysosomes and mitochondria-lysosome contact.Interestingly, the kinase regulated mitophagy and lysosomal repair independently from its function in glycolysis. Furthermore, loss function of HKDC1 accelerated DNA damage–induced cellular senescence with the accumulation of hyperfused mitochondria and damaged lysosomes. Our results show that HKDC1, a novel factor downstream of TFEB, maintains both mitochondrial and lysosomal homeostasis, which is critical to prevent cellular senescence.