Project description:Purpose: The goals of this study are to establish a dynamic roadmap of imprinted X chromosome inactivation and the role of Xist by elucidation of the transcriptome of Xist KO embryos during mouse preimplantation development. Methods: mRNA profiles of the preimplantation embryos WT and KO for Xist were elucidated by RNA-seq at various stages. Trophoblasts isolated from blastocyst outgrowths were also included. The sequence reads for samples where gender could be determined and that passed quality filters were analyzed at the level of autosomes, X chromosome as well as single genes. Results: Female embryos fail to silence the X chromosome at late preimplantation development. General autosomal gene expression is not affected in embryos lacking Xist. Conclusions: Xist is crucial for iXCI. In preimplantation embryos, the main in vivo function of Xist is to regulate iXCI in females.
Project description:Purpose: The goals of this study are to define transcriptome (RNA-seq) of mouse preimplantation embryos at different stages of development under a range of different environmental conditions. Methods: Mouse preimplantation embro transcriptional profiles were generated using embryos at several different developmental stages using Smart-seq2. Results: RNA-seq analysis finds that there is a highly dynamic pattern of gene expression during the preimplantation period. The sensitiivty to nutrient conditions varies markedly at different stages of development, with 2C embryos more sensitive to pyruvate omission than later stage embryos. Conclusions: Our study represents a comprehensive analysis of the mouse preimplantation development transcriptome, and how pyruvate provision impacts different developmental stages.
Project description:Purpose: The goals of this study are to establish a roadmap of XCI and compare the transcriptomes of WT and Rlim KO embryos during X chromosome inactivation. Methods: mRNA profiles of 175 preimplantation embryos WT and KO for Rlim were elucidated by RNA-seq at various stages. Trophoblasts isolated from blastocyst outgrowths were also included. The sequence reads that samples where gender could be determined and that passed quality filters were analyzed at the level of autosomes, X xhromosomes as well as single genes. Results: Using single cell RNA-seq technology on 175 whole preimplantation embryos, we obtained about 2.95 million sequence reads per sample. Reads were normalized to autosomal gene expression. Gender of each embryo was determined by expression of Y-linked genes and Xist. Data analysis showed normal expression profiles of marker genes for epiblast and trophoblast cell types during preimplantation development. Comparing Xist expression profiles in embryos WT and KO shows that Rlim is not required for initiation of Xist transcription but for upregulation of Xist expression. Moreover, our results identify two waves of XCI during preimplantation development: One that occurs at Morula stages that is Rlim-independent and one at blastocyst stages that in dependent on Rlim. Conclusions: Our study represents the first detailed mouse preimplantation transcriptome. Our results show that Rlim is required for a second wave of imprinted XCI that occurs in female embryos at blastocyst stages.
Project description:Purpose: The goals of this study are to establish a dynamic roadmap of imprinted X chromosome inactivation and the role of Xist by elucidation of the transcriptome of Xist KO embryos during mouse preimplantation development Methods: mRNA profiles of the preimplantation embryos WT and KO for Xist were elucidated by RNA-seq at various stages. Trophoblasts isolated from blastocyst outgrowths were also included. The sequence reads that samples where gender could be determined and that passed quality filters were analyzed at the level of autosomes, X chromosome as well as single genes. Effects of genetic background on the kinetics of iXCI was evaluated by RNA-seq on E3.5 embryos with a hybrid C57BL/6 x Cast background. Results: Female embryos fail to silence the X chromosome at late preimplantation development. General autosomal gene expression is not affected in embryos lacking Xist. Conclusions: Xist is crucial for iXCI. In preimplantation embryos the main in vivo function of Xist is to regulate iXCI in females. Genetic background does not significantly influence kinetics of iXCI.
Project description:The transformation of a fertilized oocyte into a multicellular embryo comprised of differentiated cells depends on the processing of genetic orders, first in the form of transcripts and then of proteins. Our current understanding of mouse development has greatly benefited from the analysis of transcripts as proxy for the proteins. However, the hexagonal-shaped free ribosomes that translate mRNAs into proteins are scarce during cleavage and do not become abundant until the morula-blastocyst stage. How accurate, then, is an understanding of mouse and more in general mammalian development that uses the analysis of transcripts as proxy for the proteins? This led us in this study to measure the proteome of seven preimplantation mouse stages (B6C3F1 x CD1), from oocyte to blastocyst, using 'spike-in' SILAC technology combined with high accuracy mass spectrometry (LTQ Orbitrap and Q-Exactive). The relative abundances of embryonic proteins were compared and contrasted with those of transcripts measured by RNA sequencing. A total of 6976 proteins were detected in at least the spike (precondition for determining the heavy/light peptide ratios in oocytes or embryos). Among these 6976 proteins, 4991 proteins were present in all developmental stages, and 1893 proteins were present in all replicates. Our tandem approach uncovered: 1) the different abundance profiles of proteome and transcriptome during the time of preimplantation development; 2) the different reciprocal associations of developmental stages (dendrograms) on the protein level as compared to the mRNA level; and 3) the different gene ontology terms overrepresented among the proteins that increase or decrease across adjacent stages, compared to mRNAs. In essence, the elaborate phasing of embryonic gene expression that has been known for mRNAs leaves an unsuspected footprint on the protein products of those mRNAs. This information facilitates the analysis of mammalian development in two important ways. First, it provides new insight into the regulation of the transition from the differentiated oocyte into the embryo, by identifying the subsets of proteins that accompany the passage from one embryonic stage to the next, which are likely composed of important regulators of the morphogenetic transitions. Second, our analysis provides a reference to determine the degree of ‘embryoness’ of entities produced via assisted reproductive technologies, cloning by somatic cell nuclear transfer, and even artificial gametes.