Functional redundancy of variant and canonical histone H3K9 modification in Drosophila
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ABSTRACT:
ORGANISM(S): Drosophila melanogaster
PROVIDER: GSE106192 | GEO | 2017/12/25
SECONDARY ACCESSION(S): PRJNA415844
REPOSITORIES: GEO
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Project description:The chromatin of animal cells contains two types of histones: canonical histones that are expressed during S phase of the cell cycle to package the newly replicated genome, and variant histones with specialized functions that are expressed throughout the cell cycle and in non-proliferating cells. Determining whether and how canonical and variant histones cooperate to regulate genome function is integral to understanding how chromatin-based processes affect normal and pathological development. Here, we demonstrate that variant histone H3.3 is essential for Drosophila development only when canonical histone gene copy number is reduced, suggesting that coordination between canonical H3.2 and variant H3.3 expression is necessary to provide sufficient H3 protein for normal genome function. To identify genes that depend upon, or are involved in, this coordinate regulation we screened for hemizygous chromosome 3 deficiencies that impair development of flies bearing reduced H3.2 and H3.3 gene copy number. We identified two regions of chromosome 3 that conferred this phenotype, one of which contains the Polycomb gene, which is necessary for establishing domains of facultative chromatin that repress master regulator genes during development. We further found that reduction in Polycomb dosage decreases viability of animals with no H3.3 gene copies. Moreover, heterozygous Polycomb mutations result in de-repression of the Polycomb target gene Ubx and cause ectopic sex combs when either canonical or variant H3 gene copy number is also reduced. We conclude that Polycomb-mediated facultative heterochromatin function is compromised when canonical and variant H3 gene copy number falls below a critical threshold. To investigate whether H3.3A and/or H3.3B mRNA levels change in 12xHWT animals, we looked at differential gene expression profiles of 12xHWT and yw (200xWT) third instar larval brain cells.
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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
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Project description:Endogenous retroviruses (ERVs) have provided an evolutionary advantage in the diversification of transcript regulation and are thought to be involved in the establishment of extraembryonic tissues during development. However, silencing of these elements remains critical for the maintenance of genome stability. Here, we define a new chromatin state that is uniquely characterized by the combination of the histone variant H3.3 and H3K9me3, two chromatin ‘marks’ that have previously been considered to belong to fundamentally opposing chromatin states. H3.3/H3K9me3 heterochromatin is fundamentally distinct from ‘canonical’ H3K9me3 heterochromatin that has been under study for decades and this unique functional interplay of a histone variant and a repressive histone mark is crucial for silencing ERVs in ESCs. Our study solidifies the emerging notion that H3.3 is not a histone variant associated exclusively with “active” chromatin and further suggests that its incorporation at unique heterochromatic regions may be central to its function during development and the maintenance of genome stability.
2015-05-05 | GSE59188 | GEO
Project description:Endogenous retroviruses (ERVs) have provided an evolutionary advantage in the diversification of transcript regulation and are thought to be involved in the establishment of extraembryonic tissues during development. However, silencing of these elements remains critical for the maintenance of genome stability. Here, we define a new chromatin state that is uniquely characterized by the combination of the histone variant H3.3 and H3K9me3, two chromatin ‘marks’ that have previously been considered to belong to fundamentally opposing chromatin states. H3.3/H3K9me3 heterochromatin is fundamentally distinct from ‘canonical’ H3K9me3 heterochromatin that has been under study for decades and this unique functional interplay of a histone variant and a repressive histone mark is crucial for silencing ERVs in ESCs. Our study solidifies the emerging notion that H3.3 is not a histone variant associated exclusively with “active” chromatin and further suggests that its incorporation at unique heterochromatic regions may be central to its function during development and the maintenance of genome stability.
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Project description:Functional redundancy of variant and canonical histone H3K9 modification in Drosophila
| PRJNA415844 | ENA
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.
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Project description:Histone variant H3.3 is a critical regulator of cell differentiation and development. Likewise, methylation on lysine 27 of the canonical histone H3 (H3K27me3) has been previously characterized in development. However, the effect of methylation on lysine 27 on the variant histone H3.3 remains unclear. By applying proteomics and genomics techniques, we investigate the role of lysine 27 tri-methylation specifically on the histone variant H3.3 (H3.3K27me3) in the context of mouse embryonic stem cell pluripotency and differentiation as a model system for development. Using a custom-made antibody, we identify through ChIP-seq experiments and corresponding RNA-seq experiments that H3.3K27me3 does not show the same strong negative correlation with gene expression as is observed for canonical H3K27me3, nor the same strong positive correlation with gene expression as observed for H3.3. However, a unique enrichment was detected of H3.3K27me3 at lineage-specific genes, such as olfactory receptor genes, and at binding motifs for the transcription factors FOXJ2/3. REST, a predicted FOXJ2/3 target that acts as a transcriptional repressor of terminal neuronal genes, was identified with H3.3K27me3 at its promoter region. H3.3K27A mutant cells confirmed an upregulation of FOXJ2/3 targets upon the loss of methylation at H3.3K27 both at the transcriptomic and proteomic level. Thus, while canonical H3K27me3 has been characterized to regulate the expression of transcription factors that play a general role in differentiation, our work suggests H3.3K27me3 is essential for regulating distinct terminal differentiation genes.
2022-01-18 | GSE169745 | GEO