Project description:In this study, we identified a number of genes whose expression are regulated by the Hippo tumor suppressor pathway. To disrupt Hippo signaling in the mouse heart, we inactivated the single mammalian Salv ortholog using a Salv conditional null allele and the Nkx2.5 cre allele that directs cardiac cre activity. Total RNA from embryonic hearts were used for expression profiling of 17,455 unique genes. Genes transcriptionally regulated by the Hippo pathway during cardiogenesis were identifed through expression profiling of 17,455 unique genes in Salvador mutant (Salv CKO) embryonic hearts. Total RNA from E9.5-stage hearts were pooled into biological replicate samples (2 control and 2 Salv CKO) and were used to generate expression profiles.
Project description:In this study, we identified a number of genes whose expression are regulated by the Hippo tumor suppressor pathway. To disrupt Hippo signaling in the mouse heart, we inactivated the single mammalian Salv ortholog using a Salv conditional null allele and the Nkx2.5 cre allele that directs cardiac cre activity. Total RNA from P8-stage hearts were used for expression profiling. Genes transcriptionally regulated by the Hippo pathway during cardiogenesis were identifed through expression profiling in Salvador mutant (Salv CKO) neontate hearts. Total RNA from postnatal day 8 (P8)-stage hearts was purified to generate biological replicate samples (2 control and 2 Salv CKO) and generate expression profiles. 3 technical replicates were used for each sample.
Project description:YAP, the key protein effector of the Hippo pathway, is a transcriptional co-activator that controls the expression of cell cycle genes, promotes cell growth and proliferation and regulates organ size. YAP modulates gene transcription by binding to distal enhancers, but the mechanisms of gene regulation by YAP-bound enhancers remain poorly understood. Here we show that constitutive active YAP5SA leads to widespread changes in chromatin accessibility in untransformed MCF10A cells. Newly accessible regions include YAP-bound enhancers that mediate activation of cycle genes regulated by the Myb-MuvB (MMB) complex. By CRISPR-interference we identify a role for YAP-bound enhancers in phosphorylation of Pol II at Ser5 at MMB-regulated promoters, extending previously published studies that suggested YAP primarily regulates the pause-release step and transcriptional elongation. YAP5SA also leads to less accessible 'closed' chromatin regions, which are not directly YAP-bound but which contain binding motifs for the p53 family of transcription factors. Diminished accessibility at these regions is, at least in part, a consequence of reduced expression and chromatin-binding of the p53 family member ΔNp63 resulting in downregulation of ΔNp63-target genes and promoting YAP-mediated cell migration. In summary, our studies uncover changes in chromatin accessibility and activity that contribute to the oncogenic activities of YAP.
Project description:Background - The inability of the adult mammalian heart to regenerate following injury represents a major barrier in cardiovascular medicine. In contrast, the neonatal mammalian heart retains a transient capacity for regeneration, which is lost shortly after birth. Defining the molecular mechanisms that govern regenerative capacity in the neonatal period remains a central goal in cardiac biology. Here, we construct a transcriptional atlas of multiple cardiac cell populations, which enables comparative analyses of the regenerative (neonatal) versus non-regenerative (adult) state for the first time. Methods - Cardiomyocytes, fibroblasts, leukocytes and endothelial cells from infarcted and non-infarcted neonatal (P1) and adult (P56) hearts were isolated by enzymatic dissociation and FACS. RNA sequencing (RNA-seq) was performed on these cell populations to generate a transcriptomic atlas of the major cardiac cell populations during cardiac development, repair and regeneration. In addition, we surveyed the epigenetic landscape of cardiomyocytes during post-natal maturation by performing deep sequencing of accessible chromatin regions using the Assay for Transposase-Accessible Chromatin (ATAC-seq) from purified cardiomyocyte nuclei (P1, P14 and P56). Results - Profiling of cardiomyocyte and non-myocyte transcriptional programs uncovered several injury responsive genes across regenerative and non-regenerative time points. However, the majority of transcriptional changes in all cardiac cell types resulted from developmental maturation from neonatal stages to adulthood rather than activation of a distinct regeneration-specific gene program. Furthermore, adult leukocytes and fibroblasts reverted to a neonatal state and re-activated a neonatal proliferative network following infarction. In contrast, cardiomyocytes failed to re-activate the neonatal proliferative network following infarction, which was associated with loss of chromatin accessibility around cell cycle genes during post-natal maturation. Conclusions – This work provides a comprehensive transcriptional resource of multiple cardiac cell populations during cardiac development, repair and regeneration. Our findings define a transcriptional program underpinning the neonatal regenerative state and identifies an epigenetic barrier to re-induction of the regenerative program in adult cardiomyocytes.
Project description:Background - The inability of the adult mammalian heart to regenerate following injury represents a major barrier in cardiovascular medicine. In contrast, the neonatal mammalian heart retains a transient capacity for regeneration, which is lost shortly after birth. Defining the molecular mechanisms that govern regenerative capacity in the neonatal period remains a central goal in cardiac biology. Here, we construct a transcriptional atlas of multiple cardiac cell populations, which enables comparative analyses of the regenerative (neonatal) versus non-regenerative (adult) state for the first time. Methods - Cardiomyocytes, fibroblasts, leukocytes and endothelial cells from infarcted and non-infarcted neonatal (P1) and adult (P56) hearts were isolated by enzymatic dissociation and FACS. RNA sequencing (RNA-seq) was performed on these cell populations to generate a transcriptomic atlas of the major cardiac cell populations during cardiac development, repair and regeneration. In addition, we surveyed the epigenetic landscape of cardiomyocytes during post-natal maturation by performing deep sequencing of accessible chromatin regions using the Assay for Transposase-Accessible Chromatin (ATAC-seq) from purified cardiomyocyte nuclei (P1, P14 and P56). Results - Profiling of cardiomyocyte and non-myocyte transcriptional programs uncovered several injury responsive genes across regenerative and non-regenerative time points. However, the majority of transcriptional changes in all cardiac cell types resulted from developmental maturation from neonatal stages to adulthood rather than activation of a distinct regeneration-specific gene program. Furthermore, adult leukocytes and fibroblasts reverted to a neonatal state and re-activated a neonatal proliferative network following infarction. In contrast, cardiomyocytes failed to re-activate the neonatal proliferative network following infarction, which was associated with loss of chromatin accessibility around cell cycle genes during post-natal maturation. Conclusions – This work provides a comprehensive transcriptional resource of multiple cardiac cell populations during cardiac development, repair and regeneration. Our findings define a transcriptional program underpinning the neonatal regenerative state and identifies an epigenetic barrier to re-induction of the regenerative program in adult cardiomyocytes.