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Fly Dec 2022The development of all animal embryos is initially directed by the gene products supplied by their mothers. With the progression of embryogenesis, the embryo's genome is... (Review)
Review
The development of all animal embryos is initially directed by the gene products supplied by their mothers. With the progression of embryogenesis, the embryo's genome is activated to command subsequent developments. This transition, which has been studied in many model animals, is referred to as the Maternal-to-Zygotic Transition (MZT). In many organisms, including flies, nematodes, and sea urchins, genes involved in Notch signaling are extensively influenced by the MZT. This signaling pathway is highly conserved across metazoans; moreover, it regulates various developmental processes. Notch signaling defects are commonly associated with various human diseases. The maternal contribution of its factors was first discovered in flies. Subsequently, several genes were identified from mutant embryos with a phenotype similar to mutants only upon the removal of the maternal contributions. Studies on these maternal genes have revealed various novel steps in the cascade of Notch signal transduction. Among these genes, and have been functionally characterized in recent studies. Therefore, in this review, we will focus on the roles of these two maternal genes in Notch signaling and discuss future research directions on its maternal function.
Topics: Humans; Animals; Gene Expression Regulation, Developmental; Zygote; Embryonic Development; Signal Transduction; Genome
PubMed: 36346359
DOI: 10.1080/19336934.2022.2139981 -
Development (Cambridge, England) Jul 2020During development, cells need to make decisions about their fate in order to ensure that the correct numbers and types of cells are established at the correct time and... (Review)
Review
During development, cells need to make decisions about their fate in order to ensure that the correct numbers and types of cells are established at the correct time and place in the embryo. Such cell fate decisions are often classified as deterministic or stochastic. However, although these terms are clearly defined in a mathematical sense, they are sometimes used ambiguously in biological contexts. Here, we provide some suggestions on how to clarify the definitions and usage of the terms stochastic and deterministic in biological experiments. We discuss the frameworks within which such clear definitions make sense and highlight when certain ambiguity prevails. As an example, we examine how these terms are used in studies of neuronal cell fate decisions and point out areas in which definitions and interpretations have changed and matured over time. We hope that this Review will provide some clarification and inspire discussion on the use of terminology in relation to fate decisions.
Topics: Animals; Cell Differentiation; Cell Lineage; Central Nervous System; Models, Biological; Neocortex; Neurons; Stochastic Processes; Zygote
PubMed: 32669276
DOI: 10.1242/dev.181495 -
Trends in Genetics : TIG Feb 2024Pioneer factors are a subclass of transcription factors that can bind and initiate opening of silent chromatin regions. Pioneer factors subsequently regulate... (Review)
Review
Pioneer factors are a subclass of transcription factors that can bind and initiate opening of silent chromatin regions. Pioneer factors subsequently regulate lineage-specific genes and enhancers and, thus, activate the zygotic genome after fertilization, guide cell fate transitions during development, and promote various forms of human cancers. As such, pioneer factors are useful in directed cell reprogramming. In this review, we define the structural and functional characteristics of pioneer factors, how they bind and initiate opening of closed chromatin regions, and the consequences for chromatin dynamics and gene expression during cell differentiation. We also discuss emerging mechanisms that modulate pioneer factors during development.
Topics: Humans; Chromatin; Transcription Factors; Cell Differentiation; Cellular Reprogramming; Zygote
PubMed: 37940484
DOI: 10.1016/j.tig.2023.10.007 -
Current Topics in Developmental Biology 2020Drosophila melanogaster embryos develop initially as a syncytium of totipotent nuclei and subsequently, once cellularized, undergo morphogenetic movements associated... (Review)
Review
Drosophila melanogaster embryos develop initially as a syncytium of totipotent nuclei and subsequently, once cellularized, undergo morphogenetic movements associated with gastrulation to generate the three somatic germ layers of the embryo: mesoderm, ectoderm, and endoderm. In this chapter, we focus on the first phase of gastrulation in Drosophila involving patterning of early embryos when cells differentiate their gene expression programs. This patterning process requires coordination of multiple developmental processes including genome reprogramming at the maternal-to-zygotic transition, combinatorial action of transcription factors to support distinct gene expression, and dynamic feedback between this genetic patterning by transcription factors and changes in cell morphology. We discuss the gene regulatory programs acting during patterning to specify the three germ layers, which involve the regulation of spatiotemporal gene expression coupled to physical tissue morphogenesis.
Topics: Animals; Body Patterning; Drosophila Proteins; Drosophila melanogaster; Embryo, Nonmammalian; Gastrula; Gastrulation; Gene Expression Regulation, Developmental; Signal Transduction; Transcription Factors; Zygote
PubMed: 31959292
DOI: 10.1016/bs.ctdb.2019.11.004 -
Nature Structural & Molecular Biology May 2023Despite the significance of N-methyladenosine (mA) in gene regulation, the requirement for large amounts of RNA has hindered mA profiling in mammalian early embryos....
Despite the significance of N-methyladenosine (mA) in gene regulation, the requirement for large amounts of RNA has hindered mA profiling in mammalian early embryos. Here we apply low-input methyl RNA immunoprecipitation and sequencing to map mA in mouse oocytes and preimplantation embryos. We define the landscape of mA during the maternal-to-zygotic transition, including stage-specifically expressed transcription factors essential for cell fate determination. Both the maternally inherited transcripts to be degraded post fertilization and the zygotically activated genes during zygotic genome activation are widely marked by mA. In contrast to mA-marked zygotic ally-activated genes, mA-marked maternally inherited transcripts have a higher tendency to be targeted by microRNAs. Moreover, RNAs derived from retrotransposons, such as MTA that is maternally expressed and MERVL that is transcriptionally activated at the two-cell stage, are largely marked by mA. Our results provide a foundation for future studies exploring the regulatory roles of mA in mammalian early embryonic development.
Topics: Animals; Mice; Gene Expression Regulation, Developmental; Blastocyst; Oocytes; Embryonic Development; Zygote; MicroRNAs; Mammals
PubMed: 37081317
DOI: 10.1038/s41594-023-00969-x -
Cellular and Molecular Life Sciences :... Jan 2020Zygosis is the generation of new biological individuals by the sexual fusion of gamete cells. Our current understanding of eukaryotic phylogeny indicates that sex is... (Review)
Review
Zygosis is the generation of new biological individuals by the sexual fusion of gamete cells. Our current understanding of eukaryotic phylogeny indicates that sex is ancestral to all extant eukaryotes. Although sexual development is extremely diverse, common molecular elements have been retained. HAP2-GCS1, a protein that promotes the fusion of gamete cell membranes that is related in structure to certain viral fusogens, is conserved in many eukaryotic lineages, even though gametes vary considerably in form and behaviour between species. Similarly, although zygotes have dramatically different forms and fates in different organisms, diverse eukaryotes share a common developmental programme in which homeodomain-containing transcription factors play a central role. These common mechanistic elements suggest possible common evolutionary histories that, if correct, would have profound implications for our understanding of eukaryogenesis.
Topics: Animals; Biological Evolution; Cell Membrane; Eukaryota; Germ Cells; Phylogeny; Transcription Factors; Zygote
PubMed: 31203379
DOI: 10.1007/s00018-019-03187-1 -
Nature Communications Jul 2023Zygotic genome activation (ZGA) is essential for early embryonic development. However, the regulation of ZGA remains elusive in mammals. Here we report that a maternal...
Zygotic genome activation (ZGA) is essential for early embryonic development. However, the regulation of ZGA remains elusive in mammals. Here we report that a maternal factor TDP-43, a nuclear transactive response DNA-binding protein, regulates ZGA through RNA Pol II and is essential for mouse early embryogenesis. Maternal TDP-43 translocates from the cytoplasm into the nucleus at the early two-cell stage when minor to major ZGA transition occurs. Genetic deletion of maternal TDP-43 results in mouse early embryos arrested at the two-cell stage. TDP-43 co-occupies with RNA Pol II as large foci in the nucleus and also at the promoters of ZGA genes at the late two-cell stage. Biochemical evidence indicates that TDP-43 binds Polr2a and Cyclin T1. Depletion of maternal TDP-43 caused the loss of Pol II foci and reduced Pol II binding on chromatin at major ZGA genes, accompanied by defective ZGA. Collectively, our results suggest that maternal TDP-43 is critical for mouse early embryonic development, in part through facilitating the correct RNA Pol II configuration and zygotic genome activation.
Topics: Mice; Animals; RNA Polymerase II; Gene Expression Regulation, Developmental; Zygote; Embryonic Development; DNA-Binding Proteins; Mammals
PubMed: 37460529
DOI: 10.1038/s41467-023-39924-1 -
Development, Growth & Differentiation Dec 2022How the embryonic genome regulates accessibility to transcription factors is one of the major questions in understanding the spatial and temporal dynamics of gene... (Review)
Review
How the embryonic genome regulates accessibility to transcription factors is one of the major questions in understanding the spatial and temporal dynamics of gene expression during embryogenesis. Epigenomic analyses of embryonic chromatin provide molecular insights into cell-specific gene activities and genomic architectures. In recent years, significant advances have been made to elucidate the dynamic changes behind the activation of the zygotic genome in various model organisms. Here we provide an overview of the recent epigenomic studies pertaining to early Xenopus development.
Topics: Animals; Xenopus laevis; Epigenomics; Chromatin; Embryonic Development; Zygote; Gene Expression Regulation, Developmental
PubMed: 36168140
DOI: 10.1111/dgd.12813 -
Biology Open Dec 2021Mouse zygote morphokinetics were measured during interphase, the mitotic period, cytokinesis, and two-cell stage. Sequences of rounder-distorted-rounder shapes were...
Mouse zygote morphokinetics were measured during interphase, the mitotic period, cytokinesis, and two-cell stage. Sequences of rounder-distorted-rounder shapes were revealed, as were changing patterns of cross section area. A calcium chelator and an actin-disrupting agent inhibited the area changes that occurred between pronuclear envelope breakdown and cytokinesis. During cell division, two vortices developed in each nascent cell and they rotated in opposite directions at each end of the cell, a pattern that sometimes persisted for up to 10 h. Exchange with the environment may have been promoted by these shape and area cycles and persisting circulation in the cytoplasm may have a similar function between a cell's interior and periphery. Some of these movements were sporadically also seen in human zygotes with abnormal numbers of pronuclei and the two-cell stages that developed from these compromised human zygotes.
Topics: Animals; Cell Nucleus; Cytoplasm; Humans; Mice; Zygote
PubMed: 34935907
DOI: 10.1242/bio.059013 -
Current Topics in Developmental Biology 2020Mammalian embryogenesis depends on maternal factors accumulated in eggs prior to fertilization and on placental transfers later in gestation. In this review, we focus on... (Review)
Review
Mammalian embryogenesis depends on maternal factors accumulated in eggs prior to fertilization and on placental transfers later in gestation. In this review, we focus on initial events when the organism has insufficient newly synthesized embryonic factors to sustain development. These maternal factors regulate preimplantation embryogenesis both uniquely in pronuclear formation, genome reprogramming and cell fate determination and more universally in regulating cell division, transcription and RNA metabolism. Depletion, disruption or inappropriate persistence of maternal factors can result in developmental defects in early embryos. To better understand the origins of these maternal effects, we include oocyte maturation processes that are responsible for their production. We focus on recent publications and reference comprehensive reviews that include earlier scientific literature of early mouse development.
Topics: Animals; Embryo, Mammalian; Embryonic Development; Female; Gene Expression Regulation, Developmental; Genome; Maternal Inheritance; Mice; Oocytes; Zygote
PubMed: 32591079
DOI: 10.1016/bs.ctdb.2019.10.006