Project description:For animals, epigenetic modifications can be globally or partially inherited from gametes after fertilization, but the mechanism underlying how the inherited epigenetic signatures affect transcriptional regulation during zygotic genome activation (ZGA) remains poorly understood. Here, we performed genome-wide profiling of chromatin accessibility during zebrafish ZGA, which is closely related to zygotic transcriptional regulation. The locations of the accessible chromatin at promoters were precisely primed by the enrichment of unmethylated CpGs that were fully inherited from gametes. On the other hand, distal regions with high methylation levels that were inherited from the sperm facilitated the binding of DNA methylation-preferred transcription factors, such as pou5f3 and nanog, which contributed to the establishment of accessible chromatin at these loci. Our results demonstrate a model whereby inherited DNA methylation signatures from gametes prime the establishment of accessible chromatin during zebrafish ZGA through two distinct mechanisms.
Project description:Purpose: Construction of 3D zebrafish spatial transcriptomics data for studying the establishment of AP axis. Methods: We performed serial bulk RNA-seq data of zebrafish embryo at three development points. Using the published spatial transcriptomics data as references, we implemented Palette to infer spatial gene expression from bulk RNA-seq data and constructed 3D embryonic spatial transcriptomics. The constructed 3D transcriptomics data was then projected on zebrafish embryo images with 3D coordinates, establishing a spatial gene expression atlas named Danio rerio Asymmetrical Maps (DreAM). Results: DreAM provides a powerful platform for visualizing gene expression patterns on zebrafish morphology and investigating spatial cell-cell interactions. Conclusions: Our work used DreAM to explore the establishment of anteroposterior (AP) axis, and identified multiple morphogen gradients that played essential roles in determining cell AP positions. Finally, we difined a hox score, and comprehensively demonstrated the spatial collinearity of Hox genes at single-cell resolution during development.
Project description:[PROJECT] After fertilization the embryonic genome is inactive until transcription is initiated during the maternal-zygotic transition (MZT). This universal process coincides with the formation of pluripotent cells, which in mammals can be used to generate embryonic stem (ES) cells. To study the changes in chromatin structure that accompany zygotic genome activation and pluripotency, we mapped the genomic locations of histone H3 modifications before and after MZT in zebrafish embryos. Repressive H3 lysine 27 trimethylation (H3K27me3) and activating H3 lysine 4 trimethylation (H3K4me3) are only detected after MZT. H3K4me3 marks more than 80% of genes, including many developmental regulatory genes that are also occupied by H3K27me3. Sequential chromatin immunoprecipitation demonstrates that both methylation marks occupy the same promoter regions, revealing that the bivalent chromatin domains found in cultured ES cells also exist in embryos. In addition, we find a large group of genes that are monovalently marked by H3K4me3 but not H3K27me3. These H3K4me3 monovalent genes are neither expressed nor stably bound by RNA polymerase II. Closer inspection of in vitro data sets reveals similar monovalent H3K4me3 domains in ES cells. The analysis of an inducible transgene indicates that H3K4me3 domains can form in the absence of sequence-specific transcriptional activators or stable association with RNA pol II. These results suggest that bivalent and monovalent domains might poise embryonic genes for activation and that the chromatin profile associated with pluripotency is established during MZT. [SAMPLES] ChIPchip analysis of histone modifications (H3K4me3, H3K27me3, H3K36me3) and RNA polymerase II in pre MZT (256-cell) and post MZT (4hpf; dome/30% epiboly) wt zebrafish embryos. H3K4me3, H3K27me3, H3K36me3 and PolII ChIP-chip at 256 cell stage (one replicate) and 4hpf (dome/30% epiboly) (two replicates)
Project description:[PROJECT] After fertilization the embryonic genome is inactive until transcription is initiated during the maternal-zygotic transition (MZT). This universal process coincides with the formation of pluripotent cells, which in mammals can be used to generate embryonic stem (ES) cells. To study the changes in chromatin structure that accompany zygotic genome activation and pluripotency, we mapped the genomic locations of histone H3 modifications before and after MZT in zebrafish embryos. Repressive H3 lysine 27 trimethylation (H3K27me3) and activating H3 lysine 4 trimethylation (H3K4me3) are only detected after MZT. H3K4me3 marks more than 80% of genes, including many developmental regulatory genes that are also occupied by H3K27me3. Sequential chromatin immunoprecipitation demonstrates that both methylation marks occupy the same promoter regions, revealing that the bivalent chromatin domains found in cultured ES cells also exist in embryos. In addition, we find a large group of genes that are monovalently marked by H3K4me3 but not H3K27me3. These H3K4me3 monovalent genes are neither expressed nor stably bound by RNA polymerase II. Closer inspection of in vitro data sets reveals similar monovalent H3K4me3 domains in ES cells. The analysis of an inducible transgene indicates that H3K4me3 domains can form in the absence of sequence-specific transcriptional activators or stable association with RNA pol II. These results suggest that bivalent and monovalent domains might poise embryonic genes for activation and that the chromatin profile associated with pluripotency is established during MZT. [SAMPLES] ChIPchip analysis of histone modifications (H3K4me3, H3K27me3, H3K36me3) and RNA polymerase II in pre MZT (256-cell) and post MZT (4hpf; dome/30% epiboly) wt zebrafish embryos.