Regulation and function of H2A.Z during the mid-blastula transition

项目摘要 从卵裂期到原肠胚形成的发育过程发生在囊胚中期 过渡（MBT）。这一转变与几个关键事件相吻合，包括从母亲到 合子转变、合子基因组激活（ZGA）和干细胞形成。合子如何 基因组变得活跃，以及如何调节适当的发育时间是至关重要的 生物学中的未知数最近在斑马鱼和果蝇中的数据表明，这些过程是 对特定组蛋白的水平高度敏感，即组蛋白变体H2A.Z（H2Av在 果蝇）。然而，在很大程度上仍然不清楚为什么改变H2A.Z水平会破坏MBT事件 以及胚胎通常如何确保将正确量的H2A.Z掺入 染色质初步观察表明，在这两个物种的合子基因的子集是 当H2A.Z水平升高时过早激活。基因组学方法的组合 候选基因的表达分析将用于确定 胚胎中的基因激活与上调或下调核H2A.Z水平。它也将受到考验 观察到的变化在多大程度上是由于染色质相关因素（特别是 整个基因组的H2A.Z分布模式）和表观遗传标记。使用两个不同的 模型系统将揭示在何种程度上的潜在机制之间的保守性 脊椎动物和昆虫。在果蝇中，已知细胞核中的H2A.Z水平可以被 由H2A.Z结合蛋白Jabba调节，Jabba将H2A.Z隔离在细胞质中， 在MBT期间，进程处于活动状态。初步的研究得出了一个假设， Z结合蛋白在斑马鱼中起类似的作用。这一假设将是 使用活体成像、胚胎注射和结构功能分析进行测试。成功 该项目的完成将确定H2A.Z在控制基因表达模式中的作用 在细胞编程中，在发育的最关键时期之一，中期， 囊胚转变

PROJECT SUMMARY Developmental progression from cleavage phase to gastrulation occurs during the mid-blastula transition (MBT). This transition coincides with several critical events, including maternal to zygotic transition, zygotic genome activation (ZGA), and stem cell formation. How the zygotic genome becomes activate and how proper developmental timing is regulated are critical unknowns in biology. Recent data in zebrafish and Drosophila indicate that these processes are highly sensitive to the levels a particular histone, the histone variant H2A.Z (H2Av in Drosophila). However, it remains largely unknown why altered H2A.Z levels disrupt MBT events and how the embryo ordinarily assures that the correct amount of H2A.Z is incorporated into chromatin. Preliminary observations indicate that in both species a subset of zygotic genes is prematurely activated when H2A.Z levels are elevated. A combination of genomics approaches and expression analysis of candidate genes will be used to determine the temporal pattern of gene activation in embryos with up- or downregulated nuclear H2A.Z levels. It will also be tested to what extent the observed changes are due to chromatin associated factors (in particular the pattern of H2A.Z distribution across the genome) and epigenetic marks. Use of the two distinct model systems will reveal to what extent the underlying mechanisms are conserved between vertebrates and insects. In Drosophila, it is known that H2A.Z levels in the nucleus can be regulated by the H2A.Z binding protein Jabba that sequesters H2A.Z in the cytoplasm, a process active during the time of the MBT. Preliminary studies have led to the hypothesis that a different H2A.Z-binding protein plays an analogous role in zebrafish. This hypothesis will be tested using live imaging, embryo injections, and structure-function analysis. Successful completion of this project will define the role of H2A.Z in controlling gene expression patterns and in cellular programming during one of the most crucial periods of development, the mid- blastula transition.