Project description:Truncating variants in titin can cause dilated cardiomyopathy, however, the role of missense titin variants is less clear. In humans the heterozygous titin A178D variant is associated with dilated cardiomyopathy with left ventricular non-compaction. Using CRISPR-Cas9 mediated homology-directed repair the A178D titin variant was introduced into a mouse model. Homozygous A178D mice showed features of dilated cardiomyopathy. Total RNA was extracted from the left ventricles of WT and homozygous A178D littermate control mice and RNA-sequencing performed. Different patterns of gene expression were identified in wildtype and homozygous A178D left ventricles.
Project description:Left ventricular noncompaction (LVNC) Causes prominent ventricular trabeculations and reduces cardiac systolic function. The clinical presentation of LVNC ranges from asymptomatic to heart failure. We show that germline mutations in human MIB1 (mindbomb homolog 1), which encodes an E3 ubiquitin ligase that promotes endocytosis of the NOTCH ligands DELTA and JAGGED, cause LVNC in autosomal-dominant pedigrees, with affected individuals showing reduced NOTCH1 activity and reduced expression of target genes. Functional studies in cells and zebrafish embryos and in silico modeling indicate that MIB1 functions as a dimer, which is disrupted by the human mutations. Targeted inactivation of Mib1 in mouse myocardium causes LVNC, a phenotype mimicked by inactivation of myocardial Jagged1 or endocardial Notch1. Myocardial Mib1 mutants show reduced ventricular Notch1 activity, expansion of compact myocardium to proliferative, immature trabeculae and abnormal expression of cardiac development and disease genes. These results implicate NOTCH signaling in LVNC and indicate that MIB1 mutations arrest chamber myocardium development, preventing trabecular maturation and compaction. RNA was isolated from the ventricles of 16 WT and 16 Mib1flox; CTnT-cre hearts at E14.5 and then pooled into four replicates.
Project description:Left ventricular noncompaction (LVNC) Causes prominent ventricular trabeculations and reduces cardiac systolic function. The clinical presentation of LVNC ranges from asymptomatic to heart failure. We show that germline mutations in human MIB1 (mindbomb homolog 1), which encodes an E3 ubiquitin ligase that promotes endocytosis of the NOTCH ligands DELTA and JAGGED, cause LVNC in autosomal-dominant pedigrees, with affected individuals showing reduced NOTCH1 activity and reduced expression of target genes. Functional studies in cells and zebrafish embryos and in silico modeling indicate that MIB1 functions as a dimer, which is disrupted by the human mutations. Targeted inactivation of Mib1 in mouse myocardium causes LVNC, a phenotype mimicked by inactivation of myocardial Jagged1 or endocardial Notch1. Myocardial Mib1 mutants show reduced ventricular Notch1 activity, expansion of compact myocardium to proliferative, immature trabeculae and abnormal expression of cardiac development and disease genes. These results implicate NOTCH signaling in LVNC and indicate that MIB1 mutations arrest chamber myocardium development, preventing trabecular maturation and compaction.
Project description:Loss of the PR domain 16 (PRDM16) genetic locus has been suggested as the needed trigger for the development of left ventricular non-compaction cardiomyopathy (LVNC) and dilated cardiomyopathy (DCM) in patients with 1p36 deletion syndrome. Furthermore, lack of Prdm16 in the murine heart has recently been shown to cause a spectrum of cardiomyopathy phenotypes. In spite of these advances, our understanding of the downstream transcriptional pathways regulated by PRDM16 that lead to these cardiac phenotypes is limited. OBJECTIVE: to unveil the downstream transcriptional pathways involved in the development of cardiomyopathy phenotypes associated with PRDM16 mutations/deletion in human and mice. METHODS AND RESULTS: We hypothesized that PRDM16 acts as an upstream regulator of key transcriptional pathways involved in cardiac maturation. Induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from a patient with a PRDM16 variant, cardiac tissue from mice expressing the human variant, mice with cardiac-specific deletion of Prdm16 and in vitro gain and loss of Prdm16 function were employed. Here we show that de novo pathogenic variants in PRDM16 are sufficient to cause LVNC in humans. In contrast, haploinsufficiency or complete deletion of Prdm16 in cardiomyocytes in mice led to pathological hypertrophy and dilated cardiomyopathy respectively. We demonstrated that PRDM16 regulates cardiac maturation through the maintenance of estrogen-related receptors (ERRs) expression. By contrast, PRDM16 acts as a supressor of transforming growth factor beta (TGFB) signaling. CONCLUSIONS: PRDM16 is a novel regulator of cardiac maturation acting upstream of ERRs and their regulators, and a suppressor of fibrotic signaling including TGFB.
Project description:Loss of the PR domain 16 (PRDM16) genetic locus has been suggested as the needed trigger for the development of left ventricular non-compaction cardiomyopathy (LVNC) and dilated cardiomyopathy (DCM) in patients with 1p36 deletion syndrome. Furthermore, lack of Prdm16 in the murine heart has recently been shown to cause a spectrum of cardiomyopathy phenotypes. In spite of these advances, our understanding of the downstream transcriptional pathways regulated by PRDM16 that lead to these cardiac phenotypes is limited. OBJECTIVE: to unveil the downstream transcriptional pathways involved in the development of cardiomyopathy phenotypes associated with PRDM16 mutations/deletion in human and mice. METHODS AND RESULTS: We hypothesized that PRDM16 acts as an upstream regulator of key transcriptional pathways involved in cardiac maturation. Induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from a patient with a PRDM16 variant, cardiac tissue from mice expressing the human variant, mice with cardiac-specific deletion of Prdm16 and in vitro gain and loss of Prdm16 function were employed. Here we show that de novo pathogenic variants in PRDM16 are sufficient to cause LVNC in humans. In contrast, haploinsufficiency or complete deletion of Prdm16 in cardiomyocytes in mice led to pathological hypertrophy and dilated cardiomyopathy respectively. We demonstrated that PRDM16 regulates cardiac maturation through the maintenance of estrogen-related receptors (ERRs) expression. By contrast, PRDM16 acts as a supressor of transforming growth factor beta (TGFB) signaling. CONCLUSIONS: PRDM16 is a novel regulator of cardiac maturation acting upstream of ERRs and their regulators, and a suppressor of fibrotic signaling including TGFB.
Project description:Several inherited arrhythmias primarily affect the right ventricle, including Brugada syndrome and arrhythmogenic cardiomyopathy, however the molecular basis of this chamber predilection is not well understood. Right and left ventricular cardiomyocytes derive from distinct progenitor populations. Here, we show that Hrt2, a gene associated with Brugada syndrome, is a direct target of Wnt signaling in the right ventricle and Notch signaling in the left ventricle. Perturbations of Wnt and Notch signaling during development and in the adult lead to chamber-specific transcriptional effects on Hrt2 expression associated with distinct binding patterns to Hrt2 enhancers. Differential enhancer binding is present at early developmental stages when the signaling pathways are active and persists into adulthood. Consistent with chamber-specific regulation, mice deficient in Wnt transcriptional activity dysregulate only a small fraction of transcripts in common between ventricles. Wnt target gen es important for cellular electrophysiology are differentially regulated, resulting in perturbed cardiac conduction and cellular electrophysiological parameters only within the right ventricle. Ex vivo and in vivo physiologic stimulation of the right ventricle is sufficient to induce ventricular tachycardia in Wnt transcriptionally inactive hearts, while left ventricular stimulation has no effect. Taken together, these data delineate mechanisms underlying ventricular-specific arrhythmia susceptibility due to embryonic programming.
Project description:Several inherited arrhythmias primarily affect the right ventricle, including Brugada syndrome and arrhythmogenic cardiomyopathy, however the molecular basis of this chamber predilection is not well understood. Right and left ventricular cardiomyocytes derive from distinct progenitor populations. Here, we show that Hrt2, a gene associated with Brugada syndrome, is a direct target of Wnt signaling in the right ventricle and Notch signaling in the left ventricle. Perturbations of Wnt and Notch signaling during development and in the adult lead to chamber-specific transcriptional effects on Hrt2 expression associated with distinct binding patterns to Hrt2 enhancers. Differential enhancer binding is present at early developmental stages when the signaling pathways are active and persists into adulthood. Consistent with chamber-specific regulation, mice deficient in Wnt transcriptional activity dysregulate only a small fraction of transcripts in common between ventricles. Wnt target gen es important for cellular electrophysiology are differentially regulated, resulting in perturbed cardiac conduction and cellular electrophysiological parameters only within the right ventricle. Ex vivo and in vivo physiologic stimulation of the right ventricle is sufficient to induce ventricular tachycardia in Wnt transcriptionally inactive hearts, while left ventricular stimulation has no effect. Taken together, these data delineate mechanisms underlying ventricular-specific arrhythmia susceptibility due to embryonic programming.
Project description:Childhood-onset myocardial hypertrophy and cardiomyopathic changes are associated with significant morbidity and mortality early in life, particularly in patients with Noonan syndrome, a multisystemic genetic disorder caused by autosomal dominant mutations in genes of the Ras-MAPK pathway. Although the cardiomyopathy associated with Noonan syndrome (NS-CM) shares certain cardiac features with the hypertrophic cardiomyopathy caused by mutations in sarcomeric proteins (HCM), such as pathological myocardial remodeling, ventricular dysfunction and increased risk for malignant arrhythmias, the clinical course of NS-CM significantly differs from HCM. This suggests a distinct pathophysiology that remains to be elucidated. Here, by analysis of sarcomeric myosin conformational states, histopathology and gene expression in left ventricular myocardial tissue from NS-CM, HCM and normal hearts complemented with disease modeling in cardiomyocytes differentiated from patient-derived PTPN11N308S/+ induced pluripotent stem cells, we demonstrate distinct disease phenotypes between NS-CM and HCM and uncover cell cycle defects as a potential driver of NS-CM.
Project description:Pathogenic variants in MYBPC3 (myosin-binding protein C3) are the leading cause of genetic hypertrophic cardiomyopathy (HCM). Currently, there is no specific and effective treatment for this disease. Base editing is an emerging modality for treating monogenic diseases; however, its effect on MYBPC3 cardiomyopathy remains unexplored. Mybpc3-R946X/R946X mice developed early-onset left ventricular hypertrophy, systolic dysfunction, ventricular dilatation, and arrythmias. SpRY-ABEmax inefficiently corrected the Mybpc3-R946X mutation. In contrast, SpRY-ABE8e increased the efficiency by 3.6-fold and retained low level off-target editing. In vivo administration of SpRY-ABE8e efficiently corrected Mybpc3-R946X mutation in cardiomyocytes and prevented heart function decline, hypertrophic cardiomyopathy, and ventricular dysfunction. The therapeutic efficacy of SpRY-ABE8e-mediated gene correction surmounted AAV-mediated Mybpc3 gene replacement.Our study unveiled the immense potential of base editing to treat fatal inherited cardiomyopathies and opened a new avenue for the therapeutic managements of inherited cardiac diseases.