Project description:Maternal mRNAs are essential for protein synthesis during oogenesis and early embryogenesis. To adapt translation to specific needs during development, maternal mRNAs are translationally repressed by shortening the polyA tails. While mRNA deadenylation is associated with decapping and degradation in somatic cells, maternal mRNAs with short polyA tails are stable. Here we report an essential role for the germline-specific paralog of the mRNA cap-binding factor eIF4E, known as eIF4E1b, in the storage and repression of maternal mRNAs with short polyA tails. eIF4E1b binds to the mRNA cap and is targeted to ribonucleoprotein complexes through its direct interaction with eIF4ENIF1/4E-T. In early embryos, eIF4E1b binds to a specific set of translationally repressed mRNAs with short or no polyA tails, such as histone mRNAs, which are translated later on during embryogenesis. Consistent with an important role in maternal mRNA dormancy, mutation of eIF4E1b in zebrafish impairs female germline development. Understanding the mechanism and function of eIF4E1B provides new insights into fundamental post-transcriptional regulatory principles governing early vertebrate development.
Project description:The nephron, functional unit of the vertebrate kidney, is specialized in metabolic wastes excretion and body fluids osmoregulation. Given the high evolutionary conservation of gene expression and segmentation patterning between mammalian and amphibian nephrons, the Xenopus laevis pronephric kidney offers a simplified model for studying nephrogenesis. The Lhx1 transcription factor plays critical roles in kidney development, regulating target gene expression by forming multiprotein complexes with LIM binding protein 1 (Ldb1). However, few Lhx1-Ldb1 cofactors have been identified for this organ formation. By tandem- affinity purification from kidney-induced Xenopus animal caps, we identified single-stranded DNA binding protein 2 (Ssbp2) to interact with the Ldb1-Lhx1 complex. Ssbp2 is expressed in the Xenopus pronephros, and knockdown prevents normal morphogenesis and differentiation of the glomus and the convoluted renal tubules. We demonstrate a role for a member of the Ssbp family in kidney organogenesis and provide evidence of a fundamental function for the Ldb1-Lhx1-Ssbp transcriptional complexes in embryonic development.
Project description:Geminin cooperates with Polycomb to restrain multi-lineage commitment in the early embryo: Transient maintenance of a pluripotent embryonic cell population followed by the onset of multi-lineage commitment is a fundamental aspect of development. However, molecular regulation of this transition is not well characterized in vivo. Here we demonstrate that the nuclear protein Geminin is required to restrain commitment and spatially restrict mesoderm, endoderm, and non-neural ectoderm to their proper locations in the Xenopus embryo. We used microarray analyses to demonstrate that Geminin overexpression represses many genes associated with cell commitment and differentiation, while elevating expression levels of genes that maintain pluripotent early and immature neurectodermal cell states. We characterized Geminin’s relationship to cell signaling and found that Geminin broadly represses Activin-, FGF-, and BMP-mediated cell commitment. Conversely, Geminin knockdown enhances commitment responses to growth factor signaling and causes ectopic mesodermal, endodermal, and epidermal fate commitment in the embryo. We also characterized Geminin’s functional relationship with transcription factors that had similar activities and found that Geminin represses commitment independent of Oct4 ortholog (Oct25/60) activities, but depends upon intact Polycomb repressor function. Consistent with this, chromatin immunoprecipitation assays directed at mesodermal genes demonstrate that Geminin promotes Polycomb binding and Polycomb-mediated repressive histone modifications, while inhibiting modifications associated with gene activation. This work defines Geminin as an essential regulator of the embryonic transition from pluripotency through early multi-lineage commitment, and demonstrates that functional cooperativity between Geminin and Polycomb contributes to this process.
Project description:Zebrafish is an important model system for the study of vertebrate embryonic development and adaptive immunese response. Recent years have seen great advancement in the understanding of the regulatory mechanisms during zebrafish embryogenesis and immune processes, yet large gaps still remain in the functional pathways critical for each developmental stage, especially for the late embryonic development. We sequenced the polyA-extracted mRNA from 9 stages covering 7 major developmental periods of zebrafish. Whole genome gene expression pattern were analyzed to reveal unknown pathways or factors with implicated roles during each stage of vertebrate development. Analysis of total mRNA by highthroughput sequencing in 9 stages covering 7 periods during the embryonic and larval development of zebrafish
Project description:Transcription profiling of X.laevis development. The experiment were perfomed as a part of our Vertebrate Evo-Devo project. The aim of the project is to compare transcription profiles of normal (unmanipulated, wild-type, whole embryo) vertebrate embryos.