Project description:We are performing microarray experiments for expression profiling of zebrafish embryogenesis, both as a baseline for future analysis of mutant and other conditions and to validate our microarray technology. For our purpose we used the Affymetrix zebrafish array which contains approximately 15,000 genes. This represents about 50 % of the estimated number of zebrafish genes. Total RNA was collected from embryos at 16 different stages (zygote, shield stage, 75 % epiboly, 90 % epiboly, bud stage, 5-somite stage, 14-somite stage, prim-5 stage, 32 hpf and long-pec stage, 4d post fertilization (dpf), 5 dpf, 14 dpf, 30 dpf, 90 dpf, adult). Microarray analysis was performed with these stages in single colour experiments. After normalization, differential expressed genes were selected and further analyzed with GeneSpring software. In order to validate the microarray data and to assign biological functions we chose a few genes to do semi-quantitative real-time PCR. Many of the differentially expressed genes are unknown and could be candidates for regulatory genes identified in mutagenesis experiments. We identified several genes known to be involved in zebrafish organogenesis as well as novel genes with unique temporal expression patterns.
Project description:In this study, we interrogated the role of DNA methylation in HSPC generation by taking advantage of dnmt1 knockout/knockdown embryos in zebrafish. First, we generated a comprehensive DNA methylation landscape of EHT, which revealed gradually hypermethylated regions associated with vasculogenesis. Taking advantage of dnmt1-deficient embryos, we showed that the decreased DNA methylation blocked HSPC emergence. Mechanistically, we demonstrated that the decreased DNA methylation increased the expression of arterial genes and Notch signaling, thus contributing to defects in the EHT in dnmt1-deficient embryos. Herein, we identified that DNA methylation, as epigenetic regulator, participates in the negative modulation of Notch signaling through inhibiting transcription during HSPC generation in zebrafish.
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)