Project description:Histone H3.3 is a highly conserved histone H3 replacement variant in metazoans, and has been implicated in many important biological processes including cell differentiation and reprogramming. Germline and somatic mutations in H3.3 genomic incorporation pathway components, or in H3.3 encoding genes, have been associated with human congenital diseases and cancers, respectively. However, the role of H3.3 in mammalian development remains unclear. To address this question, we generated H3.3 null mouse models through classical genetic approaches. We found H3.3 plays an essential role in mouse development. Complete depletion of H3.3 leads to developmental retardation and early embryonic lethality. At the cellular level, H3.3 loss triggers cell cycle suppression and cell death. Surprisingly, H3.3 depletion does not dramatically disrupt gene regulation in the developing embryo. Instead, H3.3 depletion causes dysfunction of heterochromatin structures at telomeres, centromeres and pericentromeric regions of chromosomes leading to mitotic defects. The resulting karyotypical abnormalities and DNA damage lead to p53 pathway activation. In summary, our results reveal that an important function of H3.3 is to support chromosomal heterochromatic structures, thus maintaining genome integrity during mammalian development. RNA-seq in embryos at E10.5 comparing 3 samples with the following genotype Trp53-/-; H3f3afl/-; H3f3bfl/-; Sox2-CreTg/0 to three samples with the following genotype Trp53-/-; H3f3afl/+; H3f3bfl/+; Sox2-CreTg/0
Project description:Background. The histone variant H3.3 plays key roles in regulating chromatin states and transcription. However, the role of endogenous H3.3 in mammalian cells and during development has been less thoroughly investigated. To address this gap, we report the production and phenotypic analysis of mice and cells with targeted disruption of the H3.3-encoding gene, H3f3b. Results. H3f3b KO mice exhibit a semi-lethal phenotype traceable at least in part to defective cell division and chromosome segregation. H3f3b KO cells have widespread ectopic CENP-A protein localization suggesting one possible mechanism for defective chromosome segregation. KO cells have abnormal karyotypes and cell cycle profiles as well. The transcriptome and euchromatin-related epigenome were moderately affected by loss of H3f3b in MEFs with ontology most notably pointing to changes in chromatin regulatory and histone coding genes. Reduced numbers of H3f3b KO mice survive to maturity and almost all survivors from both sexes are infertile. Conclusions. Taken together, our studies suggest that endogenous mammalian histone H3.3 has important roles in regulating chromatin and chromosome functions that in turn are important for cell division, genome integrity, and development. Examination of H3K9Ac and H3K4me3 in wild-type and H3.3 null MEFs
Project description:Histone H3.3 is a highly conserved histone H3 replacement variant in metazoans, and has been implicated in many important biological processes including cell differentiation and reprogramming. Germline and somatic mutations in H3.3 genomic incorporation pathway components, or in H3.3 encoding genes, have been associated with human congenital diseases and cancers, respectively. However, the role of H3.3 in mammalian development remains unclear. To address this question, we generated H3.3 null mouse models through classical genetic approaches. We found H3.3 plays an essential role in mouse development. Complete depletion of H3.3 leads to developmental retardation and early embryonic lethality. At the cellular level, H3.3 loss triggers cell cycle suppression and cell death. Surprisingly, H3.3 depletion does not dramatically disrupt gene regulation in the developing embryo. Instead, H3.3 depletion causes dysfunction of heterochromatin structures at telomeres, centromeres and pericentromeric regions of chromosomes leading to mitotic defects. The resulting karyotypical abnormalities and DNA damage lead to p53 pathway activation. In summary, our results reveal that an important function of H3.3 is to support chromosomal heterochromatic structures, thus maintaining genome integrity during mammalian development.
Project description:We found that BAP1 (BRCA1 Associated Protein-1) shows loss of heterozygosity in over 25% of pancreatic cancer patients and functions as tumor suppressor. Conditional deletion of Bap1 in murine pancreas led to genomic instability, accumulation of DNA damage, and an inflammatory response that evolved to pancreatitis with full penetrance. Concomitant expression of oncogenic KrasG12D led to malignant transformation and development of invasive and metastatic pancreatic cancer. At the molecular level, BAP1 maintains the integrity of the exocrine pancreas by regulating genomic stability and its loss confers sensitivity to radio- and platinum-based therapies.
Project description:Background. The histone variant H3.3 plays key roles in regulating chromatin states and transcription. However, the role of endogenous H3.3 in mammalian cells and during development has been less thoroughly investigated. To address this gap, we report the production and phenotypic analysis of mice and cells with targeted disruption of the H3.3-encoding gene, H3f3b. Results. H3f3b KO mice exhibit a semi-lethal phenotype traceable at least in part to defective cell division and chromosome segregation. H3f3b KO cells have widespread ectopic CENP-A protein localization suggesting one possible mechanism for defective chromosome segregation. KO cells have abnormal karyotypes and cell cycle profiles as well. The transcriptome and euchromatin-related epigenome were moderately affected by loss of H3f3b in MEFs with ontology most notably pointing to changes in chromatin regulatory and histone coding genes. Reduced numbers of H3f3b KO mice survive to maturity and almost all survivors from both sexes are infertile. Conclusions. Taken together, our studies suggest that endogenous mammalian histone H3.3 has important roles in regulating chromatin and chromosome functions that in turn are important for cell division, genome integrity, and development.