Project description:Tissue homeostasis requires long-term lineage fidelity of somatic stem cells. Whether and how age-related changes in somatic stem cells impact the faithful execution of lineage decisions remains largely unknown. Here, we address this question using genome-wide chromatin accessibility and transcriptome analysis as well as single cell RNA-seq to explore stem cell intrinsic changes in the aging Drosophila intestine. These studies indicate that in stem cells of old flies, promoters of Polycomb (Pc) target genes become differentially accessible, resulting in the increased expression of enteroendocrine (EE) cell specification genes. Consistently, we find age related changes in the composition of the EE progenitor cell population in aging intestines, as well as a significant increase in the proportion of EE-specified ISCs and progenitors in aging flies. We further confirm that Pc-mediated chromatin regulation is a critical determinant of EE cell specification in the Drosophila intestine. Pc is required to maintain expression of stem cell genes while ensuring repression of differentiation and specification genes. Our results identify Pc group proteins as central regulators of lineage identity in the intestinal epithelium and highlight the impact of age-related decline in chromatin regulation on tissue homeostasis.
Project description:Tissue homeostasis requires long-term lineage fidelity of somatic stem cells. Whether and how age-related changes in somatic stem cells impact the faithful execution of lineage decisions remains largely unknown. Here, we address this question using genome-wide chromatin accessibility and transcriptome analysis as well as single cell RNA-seq to explore stem cell intrinsic changes in the aging Drosophila intestine. These studies indicate that in stem cells of old flies, promoters of Polycomb (Pc) target genes become differentially accessible, resulting in the increased expression of enteroendocrine (EE) cell specification genes. Consistently, we find age related changes in the composition of the EE progenitor cell population in aging intestines, as well as a significant increase in the proportion of EE-specified ISCs and progenitors in aging flies. We further confirm that Pc-mediated chromatin regulation is a critical determinant of EE cell specification in the Drosophila intestine. Pc is required to maintain expression of stem cell genes while ensuring repression of differentiation and specification genes. Our results identify Pc group proteins as central regulators of lineage identity in the intestinal epithelium and highlight the impact of age-related decline in chromatin regulation on tissue homeostasis.
Project description:Tissue homeostasis requires long-term lineage fidelity of somatic stem cells. Whether and how age-related changes in somatic stem cells impact the faithful execution of lineage decisions remains largely unknown. Here, we address this question using genome-wide chromatin accessibility and transcriptome analysis as well as single cell RNA-seq to explore stem cell intrinsic changes in the aging Drosophila intestine. These studies indicate that in stem cells of old flies, promoters of Polycomb (Pc) target genes become differentially accessible, resulting in the increased expression of enteroendocrine (EE) cell specification genes. Consistently, we find age related changes in the composition of the EE progenitor cell population in aging intestines, as well as a significant increase in the proportion of EE-specified ISCs and progenitors in aging flies. We further confirm that Pc-mediated chromatin regulation is a critical determinant of EE cell specification in the Drosophila intestine. Pc is required to maintain expression of stem cell genes while ensuring repression of differentiation and specification genes. Our results identify Pc group proteins as central regulators of lineage identity in the intestinal epithelium and highlight the impact of age-related decline in chromatin regulation on tissue homeostasis.
Project description:Polycomb complexes are essential regulators of stem cell identity, yet very little is known about their molecular mechanisms during cell differentiation. Pcgf proteins (Pcgf1/2/3/4/5/6) are core subunits of the Polycomb repressive complex 1 (PRC1). It has been recently proposed that specific Pcgf proteins are associated to particular PRC1 complexes, yet the molecular and biological functions of different Pcgf proteins remains largely elusive. Using specific differentiation protocols, we have elucidated a role for Pcgf2/Mel18 in specifically regulating mesoderm differentiation. Mechanistically, during early cardiac mesoderm differentiation, Pcgf2/Mel18 functions as a classical Polycomb protein by repressing pluripotency, lineage specification, late cardiac differentiation and negative regulators of the BMP pathway, yet Pcgf2/Mel18 also positively regulates the expression of key mesoderm transcription factors, revealing a novel function of Pcgf2/Mel18 in gene activation during cardiac differentiation. Mel18 depletion results in an unbalance of pathways that positively and negatively regulate cardiac differentiation. We propose that Mel18 is a novel epigenetic factor that controls mesoderm differentiation by opposing molecular mechanisms. List of ChIPseq samples: Mel18 in ESCs and MES, Ring1b, RYBP and Cbx2 in MES, IgG in MESs. List of RNAseq experiments: Mel18 KD, Ring1b KO and CTR in ESCs, Mel18 KD and CTR in MES, Mel18 KD and CTR in CMs.
Project description:To check gene expression signatures for LGR5hi and LGR5lo ISCs in response to gamma-irradiation, we performed whole genome microarray on LGR5hi and LGR5lo ISCs purified from irradiated mice or non-irradiated mice Radiation induced gene expression in LGR5hi and LGR5lo ISCs of LGR5-GFPki mice was measured at 3 hours after exposure to 12Gy γ-irradiation or non-irradiation.
Project description:To examine whether IRF2, a negative regulator of IFN signaling, constitutively represses IFN signaling by binding IFN-inducible gene loci in ISCs, we performed a genome-wide chromatin immunoprecipitation/DNA sequencing (ChIP-Seq) analysis of IRF2 in Lgr5 ISCs. We identified 381 binding peaks in these cells, including well-known IFN-inducible genes. Motif analysis showed significant enrichment of consensus-binding motifs for IRF transcription factors within these peaks. Within IRF2-occupied genes in ISCs, we identified 204 of experimentally validated IFN-inducible genes from Interferome database, and 10.8% of them were overlapped with the genes upregulated by type I IFN stimulation in ISCs. These findings indicated for the first time that IRF2 constitutively bound and repressed the sterile IFN signaling at the level of ISCs.