Project description:To study the function of zebrafish nuclear pores during early embryogenesis, we generated maternal zygotic double mutant of nup85;nup133 (MZnup85;nup133) using CRISPR/Cas9 and report the transcriptome-wide changes in comparison to wild-type (WT) embryos. Our analysis reveals a dramatic delay of maternal mRNA degradation and zygotic genome activation in MZnup85;nup133 embryos during maternal-to-zygotic transition.
Project description:To investigate the function of nuclear pore complex (NPC) in the regulation of zygotic genome activation (ZGA), we established mutants of nucleoporins, including maternal and zygotic mutant of nup133 (MZnup133) and maternal mutant of elys (Melys), for maternal depletion by CRISPR/Cas9, and transgenic embryos of nup133 (Tgnup133) for maternal overexpression through Tol2 mediated method. We then performed gene expression profiling analysis using data obtained from RNA-seq of wildtype, MZnup133, Melys and Tgnup133 at three time points.
Project description:Upon fertilization, the embryonic genome remains transcriptionally inactive until the mid-blastula transition. Zygotic genome activation (ZGA) of vertebrate embryos has been extensively studied using nucleic acid-based strategies, but proteomics data are still scarce, impeding the full mechanistic understanding of how ZGA is executed during the maternal-to-zygotic transition (MZT). Here, we performed quantitative proteomics to decipher the proteome landscape of zebrafish embryos during the MZT, quantifying nearly 5,000 proteins across four embryonic stages. The stage-specific clustering based on protein expression pattern revealed that helicases (i.e., eif4a2 and ruvbl1) facilitate pluripotency factors (i.e., nanog, pou5f3, ctcf, and hmga1) triggering ZGA in zebrafish, accompanied by the maternal product decay with P-bodies and ubiquitin dependent proteolytic pathway. Dozens of transcription factors show wave-like expression patterns during MZT, implying their diverse functions in triggering the ZGA and modulating differentiation for organ development. The combination of morpholino knockdown and quantitative proteomics demonstrated that maternal Nanog is required for proper embryogenesis by regulating 1) interactions with other pluripotency factors, 2) F-actin band formation, 3) cell cycle checkpoints and 4) maternal product degradation. This study represents the most systematic proteomics survey of developmentally regulated proteins and their expression profiles accompanying MZT in zebrafish, which is a valuable proteome resource for understanding ZGA.
Project description:Maternal-to-zygotic transition (MZT) is a conserved and fundamental process during which the maternal environment of oocyte transits to the zygotic genome driven expression program, and terminally differentiated oocyte and sperm are reprogrammed to totipotency. It is initiated by maternal mRNAs and proteins during the period of zygotic genome quiescence after fertilization, followed by a gradual switch to zygotic genome activation and accompanied by clearance of maternal RNAs and proteins. A key question for embryonic development is how MZT process is regulated. Here we used a low-input proteomic analysis to measure the proteomic dynamics during early development of mouse maternal-to-zygotic transition.
Project description:During early embryogenesis, embryos undergo a massive degradation of maternally inherited mRNAs and produce new zygotic transcripts. This maternal-to-zygotic transition requires a tight interplay of mRNA transcription and degradation, but distinguishing their unique contributions remains a challenge. Here, we dissect gene regulation during the zebrafish maternal-to-zygotic transition by combining single-cell RNA-sequencing with RNA metabolic labeling and nucleotide conversion within zebrafish embryos. We decompose single-cell transcriptomes into their new (zygotic) and old (maternal) mRNA components, and elicit critical information on gene regulation as it unfolds over both time and space. We show that most cell-type restricted expression arises by zygotic transcription, but distinguish a specific role for maternal transcripts in defining germ-cell and enveloping-layer identity, two earliest specified cell identities. We recover the underlying replacement between maternal and zygotic copies of embryonic genes with a relatively constant overall mRNA level, and associate a fast replacement with genes that has a restricted zygotic expression in either cell-type or time. Our study provides a valuable resource to investigate maternal and zygotic transcriptomes and reveals post-transcriptional events that control gene regulation during early embryogenesis.
Project description:During early embryogenesis, embryos undergo a massive degradation of maternally inherited mRNAs and produce new zygotic transcripts. This maternal-to-zygotic transition requires a tight interplay of mRNA transcription and degradation, but distinguishing their unique contributions remains a challenge. Here, we dissect gene regulation during the zebrafish maternal-to-zygotic transition by combining single-cell RNA-sequencing with RNA metabolic labeling and nucleotide conversion within zebrafish embryos. We decompose single-cell transcriptomes into their new (zygotic) and old (maternal) mRNA components, and elicit critical information on gene regulation as it unfolds over both time and space. We show that most cell-type restricted expression arises by zygotic transcription, but distinguish a specific role for maternal transcripts in defining germ-cell and enveloping-layer identity, two earliest specified cell identities. We recover the underlying replacement between maternal and zygotic copies of embryonic genes with a relatively constant overall mRNA level, and associate a fast replacement with genes that has a restricted zygotic expression in either cell-type or time. Our study provides a valuable resource to investigate maternal and zygotic transcriptomes and reveals post-transcriptional events that control gene regulation during early embryogenesis.
Project description:During the maternal-to-zygotic transition (MZT), transcriptionally silent embryos rely on post-transcriptional regulation of maternal mRNAs until zygotic genome activation (ZGA). RNA-binding proteins (RBPs) are important regulators of post-transcriptional RNA processing events, yet their identities and functions during developmental transitions in vertebrates remain largely unexplored. Using mRNA interactome capture, we identified 227 RBPs in zebrafish embryos before and during ZGA, hereby named the zebrafish MZT mRNAbound proteome. This protein constellation consists of many conserved RBPs, with additional embryo- and stage-specific mRNA interactors that likely reflect the dynamics of RNA-protein interactions during MZT. The enrichment of numerous splicing factors like hnRNP proteins before ZGA was surprising, because maternal mRNAs were found to be fully spliced. To address potentially unique roles of RBPs in embryogenesis, we focused on hnRNP A1. iCLIP and subsequent mRNA reporter assays revealed a function for hnRNP A1 in the regulation of poly(A) tail length and translation of maternal mRNAs through sequence-specific association with 3’UTRs before ZGA. Comparison of iCLIP data from two developmental stages revealed that hnRNP A1 dissociates from maternal mRNAs at ZGA and instead regulates the nuclear processing of pri-miR-430 transcripts, which we validated experimentally. The shift from cytoplasmic to nuclear RNA targets was accompanied by a dramatic translocation of hnRNP A1 and other pre-mRNA splicing factors to the nucleus in a transcription-dependent manner. Thus, our study identifies global changes in RNA-protein interactions during vertebrate MZT and shows that hnRNP A1 RNA-binding activities are spatially and temporally coordinated to regulate RNA metabolism during early development.
Project description:During early stages of embryonic development the genome is transcriptionally inactive and cells are under the control of maternally provided mRNA and proteins. At a key point in development, known as the maternal to zygotic transition (MZT), the genome becomes activated and the maternally provided mRNAs begin to degrade. In the early zebrafish embryo, when under maternal control, cells divide rapidly and synchronously with cell cycles that lack gap phases. At cell cycle ten the introduction of gap phases lengthens the cell cycle and synchronised division is lost. During the MZT, zygotic activation of microRNAs leads to the targeted degradation of a number of maternally provided mRNAs, thus linking genome activation to maternal mRNA degredation.While the MZT has been studied in several different organisms the molecular mechanisms that coordinate genome activity and mRNA degradation remain largely unknown. For example, while the bulk of zygotic transcription occurs at cell cycle ten we do not understand why there is a minor wave of transcription before this time point. Similarly maternal mRNAs degrade at different rates, with only a percentage undergoing microRNA-mediated degredation. The aparant different rates of maternal mRNA degredation may be obscured by zygotic transcription.In order to gain an understanding of the MZT I intend to establish a precise understanding of transcription in the early embryo by using solexa sequencing to perform transcript counting at five different developmental stages that span the MZT. Specifically I intend to use crosses from two different zebrafish strains SAT (Sequenced AB and Tbingen, Zv9) and WIK. This project will allow one to understand the overall transcription profiles of genes in the early embryo, but importantly, the SNPs between the two different strains will determine if transcripts are maternal or zygotic (paternal). As a proof of principle we will first use one lane of sequencing to identify transcripts from a cross of an SAT and a WIK fish. This will allow us to observe SNPs between the two different strains. This will be run over one solexa lane. We will then sequence from five different time points on four different crosses SAT male and WIK female, WIK male and SAT female, WIK male and WIK female and SAT male with SAT female. We will prepare the libraries, which will be sequenced paired-end 54 bp over a total of seven lanes of solexa.. This data is part of a pre-publication release. For information on the proper use of pre-publication data shared by the Wellcome Trust Sanger Institute (including details of any publication moratoria), please see http://www.sanger.ac.uk/datasharing/
Project description:Goal of the experiment was to assess the differences in gene expression between maternal zygotic ezh2 mutant zebrafish embryos and wildtype embryos at 0 and 3.3 hpf.
Project description:Upon fertilization, maternal factors direct development in a transcriptionally silent embryo. At the maternal-to-zygotic transition (MZT), a universal step in animal development, unknown maternal factors trigger zygotic genome activation (ZGA). In zebrafish, ZGA is required for gastrulation and clearance of maternal mRNAs, which is achieved in part by the conserved microRNA miR-430. However, the precise factors that activate the zygotic program remain largely unknown. Here we show that Nanog, Pou5f1 and SoxB1 are required for genome activation in zebrafish. We identified several hundred genes directly activated by maternal factors, thus constituting the first wave of zygotic transcription in zebrafish. Ribosome profiling in the pre-MZT embryo revealed that nanog, sox19b and pou5f1 are the most highly translated transcription factor mRNAs. Combined loss of function for Nanog, SoxB1 and Pou5f1 resulted in developmental arrest prior to gastrulation, and a failure to activate >75% of zygotic genes. Furthermore, we found that Nanog binds the miR-430 locus and together with Pou5f1 and SoxB1 initiate miR-430 expression and activity. Our results demonstrate that maternal Nanog, Pou5f1 and SoxB1 are required to initiate the zygotic developmental program and in turn trigger the clearance of the maternal program by activating miR-430 expression. Wild type and loss-of-function total mRNA sequencing of embryonic transcriptomes pre- and post-MZT; ribosome profiling pre-MZT