Project description:Separation of cell lineages during early mammalian development is required to establish the pluripotent founder cell population that will give rise to the embryo proper and a functional trophoblast to support its development. We systemically assessed the role of the homeobox gene Cdx2 in vivo and in vitro development with an RNAi approach. Effective elimination of both maternal and zygotic Cdx2 resulted in typical phenotypes of Cdx2-mutant embryos, such as failure of hatching and implantation. However, the blastulation and expression of TE specific markers in these Cdx2-deficient embryos excluded the possibility of Cdx2 to act as a TE determinant, although compromised structure and functioning of TE was observed and the resulted embryos were not viable. Strikingly, the efficiency of stem cell derivation was significantly higher than control when embryos were put on MEF at the 8-cell stage and the derived stem cells were fully pluripotent as shown by chimera and tetraploid complementation experiments. Comparative genomic hybridization of wild type and Cdx2 mutant at 8-cell and blastocyst mouse embryos were performed. 8-cell biological duplicates and blastocyst stage biological triplicates embryos were used.The hybridization experiments were duplicated in a reciprocal labeling manner to reduce dye integration bias (dye-swaps).
Project description:Separation of cell lineages during early mammalian development is required to establish the pluripotent founder cell population that will give rise to the embryo proper and a functional trophoblast to support its development. We systemically assessed the role of the homeobox gene Cdx2 in vivo and in vitro development with an RNAi approach. Effective elimination of both maternal and zygotic Cdx2 resulted in typical phenotypes of Cdx2-mutant embryos, such as failure of hatching and implantation. However, the blastulation and expression of TE specific markers in these Cdx2-deficient embryos excluded the possibility of Cdx2 to act as a TE determinant, although compromised structure and functioning of TE was observed and the resulted embryos were not viable. Strikingly, the efficiency of stem cell derivation was significantly higher than control when embryos were put on MEF at the 8-cell stage and the derived stem cells were fully pluripotent as shown by chimera and tetraploid complementation experiments. Comparative genomic hybridization of wild type and Cdx2 mutant at 8-cell and blastocyst mouse embryos were performed.
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:Microarray analysis of gene expression in 2-cell embryos obtained from developmentally competent MII oocytes or developmentally incompetent MII (NSN) oocytes. In this study we have compared the expression profile of 2-cell embryos obtained after following in vitro fertilisation of developmentally competent (control) or incompetent (NSN) MII oocytes with the aim of identifying the gene expression networks that operate at this specific stage of development.
Project description:Microarray analysis of gene expression in 2-cell embryos obtained from developmentally competent MII oocytes or developmentally incompetent MII (NSN) oocytes.
Project description:How maternal factors in oocytes initiate zygotic genome activation (ZGA) remains elusive. Recent studies indicate that DPPA2 and DPPA4 are required for establishing a 2-cell embryo-like (2C-like) state in mouse embryonic stem cells (ESCs) in a DUX-dependent manner. These results suggest that DPPA2 and DPPA4 are essential maternal factors that regulate Dux and ZGA in embryos. By analyzing maternal knockout and maternal-zygotic knockout embryos, we unexpectedly found that Dux activation, ZGA, and preimplantation development are normal in embryos without DPPA2 or DPPA4. Thus, unlike in ESCs/2C-like cells, DPPA2 and DPPA4 are dispensable for ZGA and preimplantation development.
Project description:Sirtuin-1 (Sirt1), a NAD+-dependent histone deacetylase, exhibits several properties of a versatile driver of maternal-zygotic transition, due to its epigenetic and non-epigenetic substrates. The study was aimed at the dynamics of Sirt1 in early embryos and the contribution to maternal-zygotic transition. A conditional Sirt1-deficient knock-out mouse model was used. Females were hormonally stimulated and used as oocyte donors. oocytes were parthenogenetically activated and Sirt1-/- two-cell embryos were used for transcriptomic analysis.
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.