Project description:During development the fetal heart undergoes a rapid and dramatic transition to adult function through transcriptional and post-transcriptional mechanisms, including alternative splicing (AS). We performed deep RNA-sequencing for high-resolution analysis of transcriptome changes during postnatal mouse heart development using RNA from ventricles and freshly isolated cardiomyocytes (CM) and cardiac fibroblasts (CF). Extensive changes in gene expression and AS occur primarily between postnatal days 1 and 28. CM and CF showed reciprocal regulation of gene expression during postnatal development reflecting differences in proliferative capacity, cell adhesion functions, and mitochondrial metabolism. We found that AS plays a novel role in vesicular trafficking and membrane organization during postnatal CM development. Interestingly, these AS transitions are enriched among targets of two RNA-binding proteins, Celf1 and Mbnl1, which undergo developmentally regulated change in expression. Vesicular traffic genes affected by AS during normal development where Celf1 is down-regulated, showed a reversion to neonatal AS patterns when Celf1 was over-expressed in adults. RNA-seq was performed in RNA samples of ventricles, cardiomyocytes or cardiac fibroblast at different developmental stages; embryonic day 17, postnatal day (PN) 1, 10, 28 and 90 for ventricles, PN1-3, PN28 and PN60 for cardiac fibroblasts, and PN1-2, PN30, and PN67 for cardiomyocytes
Project description:During development the fetal heart undergoes a rapid and dramatic transition to adult function through transcriptional and post-transcriptional mechanisms, including alternative splicing (AS). We performed deep RNA-sequencing for high-resolution analysis of transcriptome changes during postnatal mouse heart development using RNA from ventricles and freshly isolated cardiomyocytes (CM) and cardiac fibroblasts (CF). Extensive changes in gene expression and AS occur primarily between postnatal days 1 and 28. CM and CF showed reciprocal regulation of gene expression during postnatal development reflecting differences in proliferative capacity, cell adhesion functions, and mitochondrial metabolism. We found that AS plays a novel role in vesicular trafficking and membrane organization during postnatal CM development. Interestingly, these AS transitions are enriched among targets of two RNA-binding proteins, Celf1 and Mbnl1, which undergo developmentally regulated change in expression. Vesicular traffic genes affected by AS during normal development where Celf1 is down-regulated, showed a reversion to neonatal AS patterns when Celf1 was over-expressed in adults.
Project description:During the first weeks after birth, cardiomyocytes within the mouse heart progressively exit the cell cycle, binucleate, and lose regenerative capacity. We have determined that combined pharmacological inhibition of thyroid hormone and adrenergic signaling during postnatal development robustly enhances cardiomyocyte proliferation, retention of diploid cardiomyocytes, and functional cardiac regeneration at postnatal day 14. In this study, we perform transcriptome-wide analyses to understand the genetic pathways regulated by thyroid hormone, alpha-adreneric, and beta-adrenergic signaling - individually and in combination - that promote cardiomyocyte cell-cycle arrest and loss of cardiac regenerative potential.
Project description:Cardiac maturation lays the foundation for postnatal heart development and disease, yet little is known about the contributions of the microenvironment to cardiomyocyte maturation. By integrating single-cell RNA-sequencing data of mouse hearts at multiple postnatal stages, we construct cellular interactomes and regulatory signaling networks. Here we report switching of fibroblast subtypes from a neonatal to adult state and this drives cardiomyocyte maturation. Molecular and functional maturation of neonatal mouse cardiomyocytes and human embryonic stem cell-derived cardiomyocytes are considerably enhanced upon coculture with corresponding adult cardiac fibroblasts. Further, single-cell analysis of in vivo and in vitro cardiomyocyte maturation trajectories identify highly conserved signaling pathways, pharmacological targeting of which substantially delays cardiomyocyte maturation in postnatal hearts, and markedly enhances cardiomyocyte proliferation and improves cardiac function in infarcted hearts. Together, we identify cardiac fibroblasts as a key constituent in the microenvironment promoting cardiomyocyte maturation, providing insights into how the manipulation of cardiomyocyte maturity may impact on disease development and regeneration.
Project description:Growth and expansion of ventricular chambers is essential during cardiogenesis and is achieved by proliferation of cardiac progenitors that are not fully differentiated. Disruption of this process can lead to prenatal lethality. In contrast, adult cardiomyocytes achieve growth through hypertrophy rather than hyperplasia. Although epicardial-derived signals may contribute to the proliferative process in myocytes, the factors and cell types responsible for development of the ventricular myocardial thickness are unclear. Moreover, the function of embryonic cardiac fibroblasts, derived from epicardium, and their secreted factors are largely unknown. Using a novel co-culture system, we found that embryonic cardiac fibroblasts induced proliferation of cardiomyocytes, in contrast to adult cardiac fibroblasts that promoted myocyte hypertrophy. We identified fibronectin, collagen and heparin-binding EGF-like growth factor as embryonic cardiac fibroblast-specific signals that collaboratively promoted cardiomyocyte proliferation in a paracrine fashion. b1 integrin was required for this proliferative response, and ventricular cardiomyocyte-specific deletion of b1 integrin in mice resulted in reduced myocardial proliferation and impaired ventricular compaction. These findings reveal a previously unrecognized paracrine function of embryonic cardiac fibroblasts in regulating cardiomyocyte proliferation. To identify candidate fibroblast-derived factors that promote myocyte proliferation, we isolated RNA from Nkx-YFP+ cardiomyocytes, embryonic cardiac fibroblasts, and adult cardiac fibroblasts and profiled mRNA expressions by microarray analyses. Arrays were performed using Affymetrix mouse Gene 1.0 ST arrays. Analysis was performed on three biological replicates of mouse embyonic cardiomyocytes, fibroblasts and adult cardiac fibroblasts.
Project description:Growth and expansion of ventricular chambers is essential during cardiogenesis and is achieved by proliferation of cardiac progenitors that are not fully differentiated. Disruption of this process can lead to prenatal lethality. In contrast, adult cardiomyocytes achieve growth through hypertrophy rather than hyperplasia. Although epicardial-derived signals may contribute to the proliferative process in myocytes, the factors and cell types responsible for development of the ventricular myocardial thickness are unclear. Moreover, the function of embryonic cardiac fibroblasts, derived from epicardium, and their secreted factors are largely unknown. Using a novel co-culture system, we found that embryonic cardiac fibroblasts induced proliferation of cardiomyocytes, in contrast to adult cardiac fibroblasts that promoted myocyte hypertrophy. We identified fibronectin, collagen and heparin-binding EGF-like growth factor as embryonic cardiac fibroblast-specific signals that collaboratively promoted cardiomyocyte proliferation in a paracrine fashion. b1 integrin was required for this proliferative response, and ventricular cardiomyocyte-specific deletion of b1 integrin in mice resulted in reduced myocardial proliferation and impaired ventricular compaction. These findings reveal a previously unrecognized paracrine function of embryonic cardiac fibroblasts in regulating cardiomyocyte proliferation. This SuperSeries is composed of the following subset Series: GSE14411: Gene expression in b1-integrin wild-type and knockout mouse heart GSE14412: Gene expression in mouse embyonic cardiomyocytes, fibroblasts and adult cardiac fibroblasts Refer to individual Series
Project description:The significance of cardiac stem cell (CSC) populations for cardiac regeneration remains disputed. Here, we apply the most direct definition of stem cell function (the ability to replace lost tissue through cell division) to interrogate the existence of CSCs. By single-cell mRNA sequencing and genetic lineage tracing using two Ki67 knockin mouse models, we map all proliferating cells and their progeny in homoeostatic and regenerating murine hearts. Cycling cardiomyocytes were only robustly observed in the early postnatal growth phase, while cycling cells in homoeostatic and damaged adult myocardium represented various noncardiomyocyte cell types. Proliferative postdamage fibroblasts expressing follistatin-like protein 1 (FSTL1) closely resemble neonatal cardiac fibroblasts and form the fibrotic scar. Genetic deletion of Fstl1 in cardiac fibroblasts results in postdamage cardiac rupture. We find no evidence for the existence of a quiescent CSC population, for transdifferentiation of other cell types toward cardiomyocytes, or for proliferation of significant numbers of cardiomyocytes in response to cardiac injury.
Project description:The adult mammalian heart has little regenerative capacity after myocardial infarction (MI) while neonatal mouse heart regenerates without scarring or dysfunction. However, the underlying pathways are poorly defined. We sought to derive insights into the pathways regulating neonatal development of the mouse heart and cardiac regeneration post-MI. Total RNA-seq of mouse heart through the first 10 days of postnatal life (referred to as P3, P5, P10) revealed a previously unobserved transition in microRNA expression between P3 and P5 associated specifically with altered expression of protein-coding genes on the focal adhesion pathway and cessation of cardiomyocyte cell division. We found profound changes in the coding and non-coding transcriptome after neonatal MI, with evidence of essentially complete healing by P10. Over two thirds of each of the mRNAs, lncRNAs and microRNAs that were differentially expressed in the post-MI heart were differentially expressed during normal postnatal development, suggesting a common regulatory pathway for normal cardiac development and post-MI cardiac regeneration. We selected exemplars of miRNAs implicated in our data set as regulators of cardiomyocyte proliferation. Several of these showed evidence of a functional influence on mouse cardiomyocyte cell division. In addition, a subset of these microRNAs, miR-144-3p, miR-195a-5p, miR-451a and miR-6240 showed evidence of functional conservation in human cardiomyocytes. The sets of mRNAs, miRNAs and lncRNAs that we report here merit further investigation as gatekeepers of cell division in the postnatal heart and as targets for extension of the period of cardiac regeneration beyond the neonatal period.