Project description:The pluripotent mammalian epiblast undergoes unusually fast cell proliferation. This rapid growth is expected to generate a high transcriptional demand, but the underlying mechanisms remain unknown. We report that the chromatin remodeler Chd1, which binds the activating histone mark H3K4me3 and is associated with transcription, is required for development of the mouse epiblast. Chd1-/- embryos exhibit proliferation defects and increased apoptosis, are smaller than controls by E5.5, and fail to grow, become patterned or gastrulate. We show that Chd1-/- ES cells have a self-renewal defect and a genome-wide reduction in transcriptional output that is associated with losses in RNA Pol II elongation at growth-promoting genes, including ribosomal proteins. We also report that Chd1 directly regulates ribosomal RNA transcription and that both Chd1-/- epiblast cells in vivo and ES cells in vitro express significantly lower levels of ribosomal RNA. Single cell analyses reveal abnormal nucleolar morphology in mutants in vivo and in vitro. These data indicate that Chd1 promotes a globally elevated transcriptional output required to sustain the distinct rapid growth of the mouse epiblast.
Project description:Lineage specification during development involves reprogramming of chromatin states, but little is known about how this is regulated in vivo. We previously showed that the chromatin remodeler Chd1 regulates transcriptional output and self-renewal of mouse embryonic stem cells, and is essential for epiblast development. These results raise the question of whether Chd1 regulates the development of other progenitor populations. Here we report that endothelial-specific deletion of Chd1 using Tie2-Cre leads to embryonic lethality by E15.5. Development of the vasculature and of primitive hematopoiesis appears to occur normally in the mutants. However, mutant embryos show signs of anemia as early as E11.5, are depleted of definitive hematopoietic stem /progenitor cells, and display a complete failure of fetal liver erythropoiesis. While mutants at E10.5 appear morphologically normal and can develop hemogenic clusters in the dorsal aorta, the E10.5 mutant endothelium fails to activate a transcriptional program associated with hematopoiesis. This transcriptional program may serve as a resource for the identification of novel markers or regulators of definitive hematopoiesis. Finally, hematopoietic-specific Chd1 deletion using Vav-Cre yields no apparent defects during development or adulthood. These results suggest that Chd1 regulates chromatin-remodeling events critical for a specific developmental window during the transition of endothelial cells to definitive blood progenitors. Analysis of CD31+ tdTomato+ cells sorted from E10.5 whole embryos with an endothelial-specific deletion of Chd1, using 4 biological replicates of 2 genotypes (CreHet controls vs mutants).
Project description:Lineage specification during development involves reprogramming of chromatin states, but little is known about how this is regulated in vivo. We previously showed that the chromatin remodeler Chd1 regulates transcriptional output and self-renewal of mouse embryonic stem cells, and is essential for epiblast development. These results raise the question of whether Chd1 regulates the development of other progenitor populations. Here we report that endothelial-specific deletion of Chd1 using Tie2-Cre leads to embryonic lethality by E15.5. Development of the vasculature and of primitive hematopoiesis appears to occur normally in the mutants. However, mutant embryos show signs of anemia as early as E11.5, are depleted of definitive hematopoietic stem /progenitor cells, and display a complete failure of fetal liver erythropoiesis. While mutants at E10.5 appear morphologically normal and can develop hemogenic clusters in the dorsal aorta, the E10.5 mutant endothelium fails to activate a transcriptional program associated with hematopoiesis. This transcriptional program may serve as a resource for the identification of novel markers or regulators of definitive hematopoiesis. Finally, hematopoietic-specific Chd1 deletion using Vav-Cre yields no apparent defects during development or adulthood. These results suggest that Chd1 regulates chromatin-remodeling events critical for a specific developmental window during the transition of endothelial cells to definitive blood progenitors.
Project description:Stem and progenitor cells undergo a global elevation of nascent transcription, or hypertranscription, during key developmental transitions involving rapid cell proliferation. The chromatin remodeler Chd1 binds to RNA Pol I and II genes and is required for hypertranscription in embryonic stem (ES) cells in vitro and the early post-implantation epiblast in vivo. Biochemically, Chd1 has been shown to facilitate transcription at least in part by removing nucleosomal barriers to elongation, but its mechanism of action in stem cells remains poorly understood. Here we report a novel role for Chd1 in the repair of promoter-proximal endogenous double-stranded DNA breaks (DSBs) in ES cells. An unbiased proteomics approach revealed that Chd1 interacts with several DNA repair factors including ATM, Parp1, Kap1 and Topoisomerase 2. We show that wild-type ES cells display high levels of phosphorylated H2AX and Kap1 at chromatin, notably at rDNA in the nucleolus, in a Chd1-dependent manner. Loss of Chd1 leads to an extensive accumulation of DSBs at Chd1 target Pol II genes and rDNA. Genes prone to DNA breaks in Chd1-null ES cells tend to be longer genes with GC-rich promoters, a more labile nucleosomal structure and roles in chromatin organization, transcription and signaling. These results reveal a vulnerability of hypertranscribing stem cells to endogenous DNA breaks, with important implications for developmental and cancer biology.
Project description:Stem and progenitor cells undergo a global elevation of nascent transcription, or hypertranscription, during key developmental transitions involving rapid cell proliferation. The chromatin remodeler Chd1 binds to genes transcribed by RNA Pol I and II and is required for hypertranscription in embryonic stem (ES) cells in vitro and the early post-implantation epiblast in vivo. Biochemically, Chd1 has been shown to facilitate transcription at least in part by removing nucleosomal barriers to elongation, but its mechanism of action in stem cells remains poorly understood. Here we report a novel role for Chd1 in the repair of promoter-proximal endogenous double-stranded DNA breaks (DSBs) in ES cells. An unbiased proteomics approach revealed that Chd1 interacts with several DNA repair factors including ATM, Parp1, Kap1 and Topoisomerase 2β. We show that wild-type ES cells display high levels of phosphorylated H2AX and Kap1 at chromatin, notably at rDNA in the nucleolus, in a Chd1-dependent manner. Loss of Chd1 leads to an extensive accumulation of DSBs at Chd1-bound Pol II-transcribed genes and rDNA. Genes prone to DNA breaks in Chd1-null ES cells tend to be longer genes with GC-rich promoters, a more labile nucleosomal structure and roles in chromatin organization, transcription and signaling. These results reveal a vulnerability of hypertranscribing stem cells to endogenous DNA breaks, with important implications for developmental and cancer biology.
Project description:Gastrulation initiates with the formation of the primitive streak, during which, cells of the epiblast delaminate to form the mesoderm and definitive endoderm. At this stage, the pluripotent cell population of the epiblast undergoes very rapid cellular proliferation and extensive epigenetic programming. Here, we show that Fam208a, a new epigenetic modifier, is essential for early post-implantation development using mouse strains harbouring two different allelic mutations. We show that at E6.5, Fam208a mutants have a decreased number of Oct4-positive epiblast cells due to an increase in p53-driven apoptosis. Complete removal of p53 could rescue the gastrulation block in Fam208a mutants, enabling them to develop until E8.5-9.0. The data demonstrates a new in vivo function of Fam208a in maintaining epiblast fitness thereby, making it an important factor at the onset of gastrulation.
Project description:Deregulation of chromatin architecture is emerging as a critical feature of carcinogenesis, and genomic alterations in nucleosome remodelers are common in human cancer. Recurrent deletion of the chromatin remodeler CHD1 is among the most common alterations in prostate cancer, but its role as a tumor suppressor and the reasons for the tissue-specific nature of CHD1 deletion remain undefined. Here, we show that deletion of CHD1 drives prostate tumorigenesis and fundamentally reprograms the transcriptional program of the androgen receptor (AR), diverting AR towards an oncogenic transcriptional program and away from a growth suppressive transcriptome. Conditional deletion of Chd1 in mouse prostate resulted in prostate neoplasia in vivo, confirming CHD1 as a tumor suppressor in prostate tissue. In prostate cells, the interactome of chromatin-bound CHD1 was enriched for factors that regulate nuclear receptor function, and interrogation of the CHD1 cistrome revealed promoter-independent enrichment of CHD1 at sites specifically occupied by AR and its associated transcriptional regulators. Deletion of CHD1 resulted in a dramatic redistribution of AR across the genome, localizing AR to sites enriched for HOXB13, and depleting AR at AR-halfsite motifs, consistent with the AR cistrome and epigenetic marks in human prostate cancer samples. Furthermore, the CHD1 null AR cistrome was associated with a unique AR transcriptional signature, enriched for pro-oncogenic pathways and depleted for processe consistent with normal prostatic function. Collectively, these data implicate CHD1 as a prostate-specific tumor suppressor which constrains the oncogenic functions of AR though maintenance of a normal AR transcriptional program.
Project description:Deregulation of chromatin architecture is emerging as a critical feature of carcinogenesis, and genomic alterations in nucleosome remodelers are common in human cancer. Recurrent deletion of the chromatin remodeler CHD1 is among the most common alterations in prostate cancer, but its role as a tumor suppressor and the reasons for the tissue-specific nature of CHD1 deletion remain undefined. Here, we show that deletion of CHD1 drives prostate tumorigenesis and fundamentally reprograms the transcriptional program of the androgen receptor (AR), diverting AR towards an oncogenic transcriptional program and away from a growth suppressive transcriptome. Conditional deletion of Chd1 in mouse prostate resulted in prostate neoplasia in vivo, confirming CHD1 as a tumor suppressor in prostate tissue. In prostate cells, the interactome of chromatin-bound CHD1 was enriched for factors that regulate nuclear receptor function, and interrogation of the CHD1 cistrome revealed promoter-independent enrichment of CHD1 at sites specifically occupied by AR and its associated transcriptional regulators. Deletion of CHD1 resulted in a dramatic redistribution of AR across the genome, localizing AR to sites enriched for HOXB13, and depleting AR at AR-halfsite motifs, consistent with the AR cistrome and epigenetic marks in human prostate cancer samples. Furthermore, the CHD1 null AR cistrome was associated with a unique AR transcriptional signature, enriched for pro-oncogenic pathways and depleted for processe consistent with normal prostatic function. Collectively, these data implicate CHD1 as a prostate-specific tumor suppressor which constrains the oncogenic functions of AR though maintenance of a normal AR transcriptional program.
Project description:Deregulation of chromatin architecture is emerging as a critical feature of carcinogenesis, and genomic alterations in nucleosome remodelers are common in human cancer. Recurrent deletion of the chromatin remodeler CHD1 is among the most common alterations in prostate cancer, but its role as a tumor suppressor and the reasons for the tissue-specific nature of CHD1 deletion remain undefined. Here, we show that deletion of CHD1 drives prostate tumorigenesis and fundamentally reprograms the transcriptional program of the androgen receptor (AR), diverting AR towards an oncogenic transcriptional program and away from a growth suppressive transcriptome. Conditional deletion of Chd1 in mouse prostate resulted in prostate neoplasia in vivo, confirming CHD1 as a tumor suppressor in prostate tissue. In prostate cells, the interactome of chromatin-bound CHD1 was enriched for factors that regulate nuclear receptor function, and interrogation of the CHD1 cistrome revealed promoter-independent enrichment of CHD1 at sites specifically occupied by AR and its associated transcriptional regulators. Deletion of CHD1 resulted in a dramatic redistribution of AR across the genome, localizing AR to sites enriched for HOXB13, and depleting AR at AR-halfsite motifs, consistent with the AR cistrome and epigenetic marks in human prostate cancer samples. Furthermore, the CHD1 null AR cistrome was associated with a unique AR transcriptional signature, enriched for pro-oncogenic pathways and depleted for processes consistent with normal prostatic function. Collectively, these data implicate CHD1 as a prostate-specific tumor suppressor which constrains the oncogenic functions of AR though maintenance of a normal AR transcriptional program.