A feedback loop between heterochromatin and the nucleopore complex controls germ-cell to oocyte transition during Drosophila oogenesis [mRNA-Seq]
Ontology highlight
ABSTRACT: Germ cells differentiate into oocytes that become totipotent upon fertilization. How the highly specialized oocyte acquires this distinct cell fate is poorly understood. During Drosophila oogenesis, H3K9me3 histone methyltransferase SETDB1 translocates from the cytoplasm to the nucleus of germ cells concurrent with oocyte specification. Here, we discovered that nuclear SETDB1 is required to silence a cohort of differentiation-promoting genes by mediating their heterochromatinization. Intriguingly, SETDB1 is also required for the upregulation of 18 of the ~30 nucleoporins (Nups) that comprise the nucleopore complex (NPC). NPCs in turn anchor SETDB1-dependent heterochromatin at the nuclear periphery to maintain H3K9me3 and gene silencing in the egg chambers. Aberrant gene expression due to loss of SETDB1 or Nups results in loss of oocyte identity, cell death and sterility. Thus, a feedback loop between heterochromatin and NPCs promotes transcriptional reprogramming at the onset of oocyte specification that is critical to establish oocyte identity.
Project description:Germ cells differentiate into oocytes that become totipotent upon fertilization. How the highly specialized oocyte acquires this distinct cell fate is poorly understood. During Drosophila oogenesis, H3K9me3 histone methyltransferase SETDB1 translocates from the cytoplasm to the nucleus of germ cells concurrent with oocyte specification. Here, we discovered that nuclear SETDB1 is required to silence a cohort of differentiation-promoting genes by mediating their heterochromatinization. Intriguingly, SETDB1 is also required for the upregulation of 18 of the ~30 nucleoporins (Nups) that comprise the nucleopore complex (NPC). NPCs in turn anchor SETDB1-dependent heterochromatin at the nuclear periphery to maintain H3K9me3 and gene silencing in the egg chambers. Aberrant gene expression due to loss of SETDB1 or Nups results in loss of oocyte identity, cell death and sterility. Thus, a feedback loop between heterochromatin and NPCs promotes transcriptional reprogramming at the onset of oocyte specification that is critical to establish oocyte identity.
Project description:Genome organization can regulate gene expression and promote cell fate transitions. The differentiation of germline stem cells (GSCs) to oocytes in Drosophila involves changes in Genome organization mediated by heterochromatin and the nuclear pore complex (NPC). Heterochromatin represses germ-cell genes during differentiation and NPCs anchor these silenced genes to the nuclear periphery, maintaining silencing to allow for oocyte development. Surprisingly, we find that genome organization also contributes to NPC formation, mediated by the transcription factor Stonewall (Stwl). As GSCs differentiate, Stwl accumulates at boundaries between silenced and active gene compartments. Stwl at these boundaries plays a pivotal role in transitioning germ-cell genes into a silenced state and activating a group of oocyte genes and Nucleoporins (Nups). The upregulation of these Nups during differentiation is crucial for NPC formation and further genome organization. Thus, crosstalk between genome architecture and NPCs is essential for successful cell fate transitions.
Project description:Genome organization can regulate gene expression and promote cell fate transitions. The differentiation of germline stem cells (GSCs) to oocytes in Drosophila involves changes in genome organization mediated by heterochromatin and the nuclear pore complex (NPC). Heterochromatin represses germ-cell genes during differentiation and NPCs anchor these silenced genes to the nuclear periphery, maintaining silencing to allow for oocyte development. Surprisingly, we find that genome organization also contributes to NPC formation, mediated by the transcription factor Stonewall (Stwl). As GSCs differentiate, Stwl accumulates at boundaries between silenced and active gene compartments. Stwl at these boundaries plays a pivotal role in transitioning germ-cell genes into a silenced state and activating a group of oocyte genes and Nucleoporins (Nups). The upregulation of these Nups during differentiation is crucial for NPC formation and further genome organization. Thus, crosstalk between genome architecture and NPCs is essential for successful cell fate transitions.
Project description:Genome organization can regulate gene expression and promote cell fate transitions. The differentiation of germline stem cells (GSCs) to oocytes in Drosophila involves changes in genome organization mediated by heterochromatin and the nuclear pore complex (NPC). Heterochromatin represses germ-cell genes during differentiation and NPCs anchor these silenced genes to the nuclear periphery, maintaining silencing to allow for oocyte development. Surprisingly, we find that genome organization also contributes to NPC formation, mediated by the transcription factor Stonewall (Stwl). As GSCs differentiate, Stwl accumulates at boundaries between silenced and active gene compartments. Stwl at these boundaries plays a pivotal role in transitioning germ-cell genes into a silenced state and activating a group of oocyte genes and Nucleoporins (Nups). The upregulation of these Nups during differentiation is crucial for NPC formation and further genome organization. Thus, crosstalk between genome architecture and NPCs is essential for successful cell fate transitions.
Project description:H3K9 tri-methylation (H3K9me3) has emerging functions in gene regulation in addition to its accumulation on constitutive heterochromatin at pericentromeres. It remains a mystery why and how H3K9me3 is dynamically regulated in male meiosis. Here, we identify a novel and critical regulator of H3K9 methylation and spermatogenic heterochromatin organization: the germline-specific protein MCAF2 (ATF7IP2). We show that MCAF2 amasses on autosomal and X pericentric heterochromatin in male germ cells. On the sex chromosomes, which undergo meiotic sex chromosome inactivation (MSCI), the DNA damage response pathway recruits MCAF2 to X pericentric heterochromatin, where it facilitates the recruitment of SETDB1, a histone methyltransferase that catalyzes H3K9me3. In the absence of MCAF2, germ cells are arrested in meiotic prophase, and the mutant analyses revealed that MCAF2 is required for the maintenance of MSCI, and for global activation of autosomal genes and retrotransposon-derived loci in meiosis; this reveals a regulatory function for MCAF2 that is counterintuitive to its association with repressive H3K9me3. Taken together, we propose that MCAF2 is a downstream effector of the DDR pathway in meiosis that coordinates the organization of heterochromatin and gene regulation through the spatial regulation of SETDB1-mediated H3K9me3 deposition.
Project description:Nucleoporins (Nups) are a family of proteins best known as the constituent building blocks of nuclear pore complexes (NPCs), the transport channels that mediate nuclear transport. Recent evidence suggest that several Nups have additional roles in controlling the activation and silencing of developmental genes, however, the mechanistic details of these functions remain poorly understood. Here, we show that depletion of Nup153 in mouse embryonic stem cells (mESCs) causes the de-repression of developmental genes and induction of early differentiation. This loss of pluripotency is not associated with defects in global nucleo-cytoplasmic transport activity. Instead, Nup153 binds to the transcriptional start site (TSS) of developmental genes and mediates the recruitment of the polycomb repressive complex 1 (PRC1) to its target loci. Our results reveal a nuclear transport-independent role of Nup153 in maintaining stem cell pluripotency and introduce a role of NPC proteins in mammalian epigenetic gene silencing. RNA-seq, ChIP-Seq, and DamID-Seq for Nup153, Oct4, and key chromatin regulators in mouse ES cells and neural progenitors
Project description:SETDB1 functioning as a histone H3K9 specific methyltransferase, is critically involved in brain development. Here, we used H3K9me3 and H3K27me3 ChIPseq to study H3K9me3 redistribution and defined enhancer function of elements in genomes of NPCs from ganglionic eminences (GE) in brain-specific Setdb1 conditional knockout mice (Setdb1-Nestin-cKO) and controls at E15.5.
Project description:Gene silencing by heterochromatin plays crucial roles in cell identity and development. However, the function of heterochromatin components is not fully understood. Here, we characterize the localization, the biogenesis and the function of an atypical heterochromatin, which is simultaneously enriched in the typical heterochromatin mark H3K9me3 as well as in H3K36me3, histone mark usually associated with gene expression. This dual heterochromatin forms on 3,015 regions in the genome of mouse embryonic stem cells and relies on the histone methyltransferases SET Domain Bifurcated 1 (SETDB1) and Nuclear Set Domain containing proteins (NSD) to generate H3K9me3 and H3K36me3, respectively. Upon SETDB1 removal, dual domains loose both trimethyl marks, gain epigenomic signatures of active enhancers, and come into long range contact with upregulated genes, suggesting that it is a major pathway by which gene expression is controlled by heterochromatin. In differentiated tissues, a large subset of these dual domains is destabilized and become enriched in active enhancer marks, providing a mechanistic insight into the involvement of heterochromatin in development and the maintenance of cell identity.
Project description:Nuclear pore complexes (NPCs) are important for cellular functions beyond nucleocytoplasmic trafficking, including genome organization and gene expression. This multi-faceted nature and the slow turnover of NPC components complicates investigations of how individual nucleoporins act in these diverse processes. To address this question, we used an Auxin-Induced Degron (AID) system to distinguish roles of basket nucleoporins Nup153, Nup50 and Tpr. Here, we provide MS data for the Nuclear Pore-enriched fraction of human DLD-1 cells, expressing CRISPR-engeneered degron, fused with the endogenous locus of corresponding basket NUPs, in the absence or presence of Auxin.
Project description:H3K9 tri-methylation (H3K9me3) plays emerging roles in gene regulation, beyond its accumulation on pericentric constitutive heterochromatin. It remains a mystery why and how H3K9me3 undergoes dynamic regulation in male meiosis. Here, we identify a novel, critical regulator of H3K9 methylation and spermatogenic heterochromatin organization: the germline-specific protein ATF7IP2 (MCAF2). We show that, in male meiosis, ATF7IP2 amasses on autosomal and X pericentric heterochromatin, spreads through the entirety of the sex chromosomes, and accumulates on thousands of autosomal promoters and retrotransposon loci. On the sex chromosomes, which undergo meiotic sex chromosome inactivation (MSCI), the DNA damage response pathway recruits ATF7IP2 to X pericentric heterochromatin, where it facilitates the recruitment of SETDB1, a histone methyltransferase that catalyzes H3K9me3. In the absence of ATF7IP2, male germ cells are arrested in meiotic prophase. Analyses of ATF7IP2-deficient meiosis reveal the protein’s essential roles in the maintenance of MSCI, suppression of retrotransposons, and global activation of autosomal genes. We propose that ATF7IP2 is a downstream effector of the DDR pathway in meiosis that coordinates the organization of heterochromatin and gene regulation through the spatial regulation of SETDB1-mediated H3K9me3 deposition. CUT&RUN of H3K9me3 in Atf7ip2+/+ and Atf7ip2-/- pachytene spermatocytes and CUT&Tag of ATF7IP2 in C57/B6 WT pachytene spermatocytes.