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Nature Reviews. Genetics Jun 2024Germ cells are the only cells in the body capable of giving rise to a new organism, and this totipotency hinges on their ability to assemble membraneless germ granules.... (Review)
Review
Germ cells are the only cells in the body capable of giving rise to a new organism, and this totipotency hinges on their ability to assemble membraneless germ granules. These specialized RNA and protein complexes are hallmarks of germ cells throughout their life cycle: as embryonic germ granules in late oocytes and zygotes, Balbiani bodies in immature oocytes, and nuage in maturing gametes. Decades of developmental, genetic and biochemical studies have identified protein and RNA constituents unique to germ granules and have implicated these in germ cell identity, genome integrity and gamete differentiation. Now, emerging research is defining germ granules as biomolecular condensates that achieve high molecular concentrations by phase separation, and it is assigning distinct roles to germ granules during different stages of germline development. This organization of the germ cell cytoplasm into cellular subcompartments seems to be critical not only for the flawless continuity through the germline life cycle within the developing organism but also for the success of the next generation.
PubMed: 38890558
DOI: 10.1038/s41576-024-00744-8 -
Journal of Cellular Physiology Sep 2023Metabolic programming is deeply intertwined with early embryonic development including zygotic genome activation (ZGA), the polarization of zygotic cells, and cell fate...
Metabolic programming is deeply intertwined with early embryonic development including zygotic genome activation (ZGA), the polarization of zygotic cells, and cell fate commitment. It is crucial to establish a noninvasive imaging technology that spatiotemporally illuminates the cellular metabolism pathways in embryos to track developmental metabolism in situ. In this study, we used two high-quality genetically encoded fluorescent biosensors, SoNar for NADH/NAD and iNap1 for NADPH, to characterize the dynamic regulation of energy metabolism and redox homeostasis during early zygotic cleavage. Our imaging results showed that NADH/NAD levels decreased from the early to the late two-cell stage, whereas the levels of the reducing equivalent NADPH increased. Mechanistically, transcriptome profiling suggested that during the two-cell stage, zygotic cells downregulated the expression of genes involved in glucose uptake and glycolysis, and upregulated the expression of genes for pyruvate metabolism in mitochondria and oxidative phosphorylation, with a decline in the expression of two peroxiredoxin genes, Prdx1 and Prdx2. Collectively, with the establishment of in situ metabolic monitoring technology, our study revealed the programming of redox metabolism during ZGA.
Topics: Embryonic Development; Gene Expression Regulation, Developmental; NAD; NADP; Oxidation-Reduction; Zygote; Animals; Mice
PubMed: 37334430
DOI: 10.1002/jcp.31054 -
Research Square Dec 2023DUX4 is a germline transcription factor and a master regulator of zygotic genome activation. During early embryogenesis, DUX4 is crucial for maternal to zygotic...
DUX4 is a germline transcription factor and a master regulator of zygotic genome activation. During early embryogenesis, DUX4 is crucial for maternal to zygotic transition at the 2-8-cell stage in order to overcome silencing of genes and enable transcription from the zygotic genome. In adult somatic cells, DUX4 expression is silenced and its activation in adult muscle cells causes the genetic disorder Facioscapulohumeral Muscular Dystrophy (FSHD). Here we show that herpesviruses from alpha-, beta- and gamma-herpesvirus subfamilies as well as papillomaviruses actively induce DUX4 expression to promote viral transcription and replication. We demonstrate that HSV-1 immediate early proteins directly induce expression of DUX4 and its target genes including endogenous retroelements, which mimics zygotic genome activation. We further show that DUX4 directly binds to the viral genome and promotes viral transcription. DUX4 is functionally required for herpesvirus infection, since genetic depletion of DUX4 by CRISPR/Cas9 abrogates viral replication. Our results show that herpesviruses induce DUX4 expression and its downstream germline-specific genes and retroelements, thus mimicking an early embryonic-like transcriptional program that prevents epigenetic silencing of the viral genome and facilitates herpesviral gene expression.
PubMed: 38168299
DOI: 10.21203/rs.3.rs-3125635/v1 -
Advanced Science (Weinheim,... May 2024Epigenetic modifiers that accumulate in oocytes, play a crucial role in steering the developmental program of cleavage embryos and initiating life. However, the...
Epigenetic modifiers that accumulate in oocytes, play a crucial role in steering the developmental program of cleavage embryos and initiating life. However, the identification of key maternal epigenetic regulators remains elusive. In the findings, the essential role of maternal Ep400, a chaperone for H3.3, in oocyte quality and early embryo development in mice is highlighted. Depletion of Ep400 in oocytes resulted in a decline in oocyte quality and abnormalities in fertilization. Preimplantation embryos lacking maternal Ep400 exhibited reduced major zygotic genome activation (ZGA) and experienced developmental arrest at the 2-to-4-cell stage. The study shows that EP400 forms protein complex with NFYA, occupies promoters of major ZGA genes, modulates H3.3 distribution between euchromatin and heterochromatin, promotes transcription elongation, activates the expression of genes regulating mitochondrial functions, and facilitates the expression of rate-limiting enzymes of the TCA cycle. This intricate process driven by Ep400 ensures the proper execution of the developmental program, emphasizing its critical role in maternal-to-embryonic transition.
Topics: Animals; Mice; Oocytes; Zygote; Female; Embryonic Development; Chromatin; Gene Expression Regulation, Developmental; Molecular Chaperones; Epigenesis, Genetic; E1A-Associated p300 Protein
PubMed: 38493496
DOI: 10.1002/advs.202308018 -
Nature Genetics Nov 2023Somatic mosaicism is a known cause of neurological disorders, including developmental brain malformations and epilepsy. Brain mosaicism is traditionally attributed to...
Somatic mosaicism is a known cause of neurological disorders, including developmental brain malformations and epilepsy. Brain mosaicism is traditionally attributed to post-zygotic genetic alterations arising in fetal development. Here we describe post-zygotic rescue of meiotic errors as an alternate origin of brain mosaicism in patients with focal epilepsy who have mosaic chromosome 1q copy number gains. Genomic analysis showed evidence of an extra parentally derived chromosome 1q allele in the resected brain tissue from five of six patients. This copy number gain is observed only in patient brain tissue, but not in blood or buccal cells, and is strongly enriched in astrocytes. Astrocytes carrying chromosome 1q gains exhibit distinct gene expression signatures and hyaline inclusions, supporting a novel genetic association for astrocytic inclusions in epilepsy. Further, these data demonstrate an alternate mechanism of brain chromosomal mosaicism, with parentally derived copy number gain isolated to brain, reflecting rescue in other tissues during development.
Topics: Humans; Mosaicism; Mouth Mucosa; Mutation; Brain; Epilepsies, Partial
PubMed: 37872450
DOI: 10.1038/s41588-023-01547-z -
Neurobiology of Disease Oct 2023De novo somatic (post-zygotic) gene mutations affecting neuroglial progenitor cell types in embryonic cerebral cortex are increasingly identified in patients with drug... (Review)
Review
De novo somatic (post-zygotic) gene mutations affecting neuroglial progenitor cell types in embryonic cerebral cortex are increasingly identified in patients with drug resistant epilepsy (DRE) associated with malformations of cortical development, in particular, focal cortical dysplasias (FCD). Somatic variants in at least 16 genes have been linked to FCD type II, all encoding components of the mechanistic target of rapamycin (mTOR) pathway. FCD type II is characterized histopathologically by cytomegalic dysmorphic neurons and balloon cells. In contrast, the molecular pathogenesis of FCD I subtypes is less well understood, and histological features are characterized by alterations in columnar or laminar organization without cytomegalic dysmorphic neurons or balloon cells. In 2018, we reported somatic mutations in Solute Carrier Family 35 member A2 (SLC35A2) linked to DRE underlying FCD type I and subsequently to a new histopathological phenotype: excess oligodendrocytes and heterotopic neurons in subcortical white matter known as MOGHE (mild malformation of cortical development with oligodendroglial hyperplasia). These discoveries opened the door to studies linking somatic mutations to FCD. In this review, we discuss the biology of SLC35A2 somatic mutations in epilepsy in FCD and MOGHE, and insights into SLC35A2 epilepsy pathogenesis, describing progress to date and critical areas for investigation.
Topics: Humans; Drug Resistant Epilepsy; Focal Cortical Dysplasia; Epilepsy; Malformations of Cortical Development, Group I; Malformations of Cortical Development
PubMed: 37739137
DOI: 10.1016/j.nbd.2023.106299 -
Zygote (Cambridge, England) Oct 2023Mammalian oocytes not fertilized immediately after ovulation can undergo ageing and a rapid decline in quality. The addition of antioxidants can be an efficient approach...
Mammalian oocytes not fertilized immediately after ovulation can undergo ageing and a rapid decline in quality. The addition of antioxidants can be an efficient approach to delaying the oocyte ageing process. Onion peel extract (OPE) contains quercetin and other flavonoids with natural antioxidant activities. In this study, we investigated the effect of OPE on mouse oocyte ageing and its mechanism of action. The oocytes were aged in M16 medium for 16 h after adding OPE at different concentrations (0, 50, 100, 200, and 500 μg/ml). The addition of 100 μg/ml OPE reduced the oocyte fragmentation rate, decreased the reactive oxygen species (ROS) level, increased the glutathione (GSH) level, and improved the mitochondrial membrane potential compared with the control group. The addition of OPE also increased the expression of , , and genes, and the caspase-3 activity in OPE-treated aged oocytes was significantly lower than that in untreated aged oocytes and similar to that in fresh oocytes. These results indicated that OPE delayed mouse oocyte ageing by reducing oxidative stress and apoptosis and enhancing mitochondrial function.
Topics: Female; Mice; Animals; Onions; Antioxidants; Oocytes; Quercetin; Oxidative Stress; Glutathione; Reactive Oxygen Species; Mammals
PubMed: 37337719
DOI: 10.1017/S0967199423000199 -
A cooperative network at the nuclear envelope counteracts LINC-mediated forces during oogenesis in .Science Advances Jul 2023Oogenesis involves transduction of mechanical forces from the cytoskeleton to the nuclear envelope (NE). In , oocyte nuclei lacking the single lamin protein LMN-1 are...
Oogenesis involves transduction of mechanical forces from the cytoskeleton to the nuclear envelope (NE). In , oocyte nuclei lacking the single lamin protein LMN-1 are vulnerable to collapse under forces mediated through LINC (linker of nucleoskeleton and cytoskeleton) complexes. Here, we use cytological analysis and in vivo imaging to investigate the balance of forces that drive this collapse and protect oocyte nuclei. We also use a mechano-node-pore sensing device to directly measure the effect of genetic mutations on oocyte nuclear stiffness. We find that nuclear collapse is not a consequence of apoptosis. It is promoted by dynein, which induces polarization of a LINC complex composed of Sad1 and UNC-84 homology 1 (SUN-1) and ZYGote defective 12 (ZYG-12). Lamins contribute to oocyte nuclear stiffness and cooperate with other inner nuclear membrane proteins to distribute LINC complexes and protect nuclei from collapse. We speculate that a similar network may protect oocyte integrity during extended oocyte arrest in mammals.
Topics: Animals; Nuclear Envelope; Caenorhabditis elegans; Oogenesis; Oocytes; Cell Nucleus; Mammals; Laminin; Caenorhabditis elegans Proteins
PubMed: 37436986
DOI: 10.1126/sciadv.abn5709 -
International Journal of Molecular... Jan 2024Mammalian fertilization initiates the reprogramming of oocytes and sperm, forming a totipotent zygote. During this intricate process, the zygotic genome undergoes a... (Review)
Review
Mammalian fertilization initiates the reprogramming of oocytes and sperm, forming a totipotent zygote. During this intricate process, the zygotic genome undergoes a maternal-to-zygotic transition (MZT) and subsequent zygotic genome activation (ZGA), marking the initiation of transcriptional control and gene expression post-fertilization. Histone modifications are pivotal in shaping cellular identity and gene expression in many mammals. Recent advances in chromatin analysis have enabled detailed explorations of histone modifications during ZGA. This review delves into conserved and unique regulatory strategies, providing essential insights into the dynamic changes in histone modifications and their variants during ZGA in mammals. The objective is to explore recent advancements in leading mechanisms related to histone modifications governing this embryonic development phase in depth. These considerations will be useful for informing future therapeutic approaches that target epigenetic regulation in diverse biological contexts. It will also contribute to the extensive areas of evolutionary and developmental biology and possibly lay the foundation for future research and discussion on this seminal topic.
Topics: Animals; Pregnancy; Female; Male; Zygote; Histone Code; Epigenesis, Genetic; Gene Expression Regulation, Developmental; Semen; Embryonic Development; Mammals
PubMed: 38338738
DOI: 10.3390/ijms25031459 -
IScience Oct 2023Double homeobox (DUX) genes are unique to eutherian mammals, expressed transiently during zygotic genome activation (ZGA) and involved in facioscapulohumeral muscular...
Double homeobox (DUX) genes are unique to eutherian mammals, expressed transiently during zygotic genome activation (ZGA) and involved in facioscapulohumeral muscular dystrophy (FSHD) and cancer when misexpressed. We evaluate the 3 human DUX genes and the ancestral single homeobox gene sDUX from the non-eutherian mammal, platypus, and find that DUX4 cytotoxicity is not shared with DUXA or DUXB, but surprisingly is shared with platypus sDUX, which binds DNA as a homodimer and activates numerous ZGA genes and long terminal repeat (LTR) elements. DUXA, although transcriptionally inactive, has DNA binding overlap with DUX4, and DUXA-VP64 activates DUX4 targets and is cytotoxic. DUXA competition antagonizes the activity of DUX4 on its target genes, including in FSHD patient cells. Since DUXA is a DUX4 target gene, this competition potentiates feedback inhibition, constraining the window of DUX4 activity. The DUX gene family therefore comprises antagonistic members of opposing function, with implications for their roles in ZGA, FSHD, and cancer.
PubMed: 37744032
DOI: 10.1016/j.isci.2023.107823