An Oct4‐Sall4‐Nanog network controls developmental progression in the pre‐implantation mouse embryo. Issue 1 (8th January 2013) - Tan, Meng How
Abstract : Landmark events occur in a coordinated manner during pre‐implantation development of the mammalian embryo, yet the regulatory network that orchestrates these events remains largely unknown. Here, we present the first systematic investigation of the network in pre‐implantation mouse embryos using morpholino‐mediated gene knockdowns of key embryonic stem cell (ESC) factors followed by detailed transcriptome analysis of pooled embryos, single embryos, and individual blastomeres. We delineated the regulons of Oct4, Sall4, and Nanog and identified a set of metabolism‐ and transport‐related genes that were controlled by these transcription factors in embryos but not in ESCs. Strikingly, the knockdown embryos arrested at a range of developmental stages. We provided evidence that the DNA methyltransferase Dnmt3b has a role in determining the extent to which a knockdown embryo can develop. We further showed that the feed‐forward loop comprising Dnmt3b, the pluripotency factors, and the miR‐290‐295 cluster exemplifies a network motif that buffers embryos against gene expression noise. Our findings indicate that Oct4, Sall4, and Nanog form a robust and integrated network to govern mammalian pre‐implantation development. Abstract : Coordination of many biological processes is necessary for mammalian pre‐implantation embryo development. The underlying regulatory network was mapped through mathematical modeling, gene‐specific knockdowns, and profiling of pooled embryos, single embryos, and single cells. Synopsis: Coordination of many biological processes is necessary for mammalian pre‐implantation embryo development. The underlying regulatory network was mapped through mathematical modeling, gene‐specific knockdowns, and profiling of pooled embryos, single embryos, and single cells. An integrated Oct4‐Sall4‐Nanog regulatory network of protein‐coding genes and microRNAs governs developmental progression in pre‐implantation mouse embryos. While many target genes are common between embryos and embryonic stem cells (ESCs), pluripotency factors regulate the expression of many metabolism‐ and transport‐related genes only in embryos but not in stem cells. The expression of some genes, including the DNA methyltransferase Dnmt3b, correlates strongly with the extent to which an embryo depleted of Oct4, Sall4, or Nanog can develop. In wild‐type embryos and ESCs, a coherent feed‐forward loop buffers the expression of Dnmt3b against intrinsic fluctuations in the levels of the pluripotency factors.