Specification and Patterning of the Animal-Vegetal Axis

早期海胆胚胎中细胞核β -连环蛋白的缺失会影响动物-植物（A/V）轴上多个细胞系的命运。众所周知，形成中胚层早期信号中心的微粒需要核β -连环蛋白才能胜任其诱导功能。在veg2谱系中，β -连环蛋白信号也需要这些细胞对微信号作出反应并被指定为中胚层。鉴定β -连环蛋白的转录靶点并阐明其功能将是确定中胚层特异性分子基础的关键一步。本研究将重点关注SUWnt8，这是一种核β -连环蛋白敏感的Wnt基因，当β -连环蛋白进入这些细胞的细胞核时，该基因在微微环境中被激活，在β -连环蛋白进入这些细胞的细胞核后不久，在蔬菜层被激活。提出的四个具体目标将确定suwnt8在这些细胞系中的功能，并将进一步了解海胆胚胎中的中胚层规范。这些目标是：(1)确定细胞相互作用在调节中胚层区域早期suwnt8表达中的作用。这将提供洞察细胞自主和非细胞自主机制在早期中胚层规范的相关作用。(2)通过使用morpholino反义寡核苷酸介导的翻译抑制来阻断SUWnt8的活性，阐明其在微粒和蔬菜层中的作用，从而确定SUWnt8如何参与早期中胚层的形成。此外，还将确定SUWnt8在维持植物细胞内细胞核β -连环蛋白水平和抑制植物细胞中动物化转录因子活性方面的可能作用。(3)虽然核β -连环蛋白是正常中胚层形成所必需的，但有证据表明，在没有可检测到的核β -连环蛋白的情况下，微粒可以在动物半囊胚中诱导中胚层。将确定SUWnt8是否可以通过平面细胞极性途径通过disheveled蛋白信号参与与β -连环蛋白途径平行的中胚层规范。(4) suwnt8独特的表达模式使其成为研究中胚层特异性转录基础的有力试剂。在微粒和蔬菜层中介导suwnt8表达的反式作用因子将被确定。总之，这些研究将进一步加深我们对下颌A/V轴是如何被指定和模式化的理解，并可能为双边动物A/V轴的进化提供见解。

0110532WikramanayakeDepletion of nuclear beta-catenin in early sea urchin embryos affects thefates of multiple cell lineages along the animal-vegetal (A/V) axis. It isknown that the micromeres, which form the early signaling center thatspecifies mesendoderm, require nuclear beta-catenin to become competent tocarry out their inductive functions. Beta-catenin signaling is alsorequired in the veg2 lineage for these cells to respond to micromeresignals and to become specified as mesendoderm. Identifyingtranscriptional targets of beta-catenin and elucidating their functionswould be a critical step in defining the molecular basis of mesendodermspecification. This proposal will focus on SUWnt8, a nuclearbeta-catenin-sensitive Wnt gene that is activated in the micromerescoincident with the entry of beta-catenin into the nuclei of these cellsand in the veg2 tier shortly after transit of beta-catenin into the nucleiof this cell tier. Four proposed specific aims will define the function ofSUWnt8 in these cell lineages and will further the understanding ofmesendoderm specification in the sea urchin embryo. These aims are: (1) Todetermine the role of cell interactions in regulating early SUWnt8expression in the mesendoderm domain. This will provide insight into therelative roles of cell autonomous and non cell-autonomous mechanisms inearly mesendoderm specification. (2) To determine how SUWnt8 participatesin early mesendoderm specification by elucidating its role in themicromeres and the veg2 tier by blocking its activity using morpholinoantisense oligonucleotide-mediated translational inhibition. Additionally,a possible role for SUWnt8 in maintaining nuclear beta-catenin levels invegetal cells and in suppressing the activity of animalizing transcriptionfactors in vegetal cells will be determined. (3) While nuclearbeta-catenin is required for normal mesendoderm specification, there isevidence that micromeres can induce mesendoderm in animal half blastomeresin the absence of detectable nuclear beta-catenin. It will be determinedif SUWnt8 can signal through the planar cell polarity pathway via theDisheveled protein to participate in mesendoderm specification in parallelwith the beta-catenin pathway. (4) The unique expression pattern of SUWnt8makes it a powerful reagent for studying the transcriptional basis ofmesendoderm specification. The trans-acting factors that mediate SUWnt8expression in the micromeres and the veg2 tier will be identified.Together, these studies will further our understanding of how the seaurchin A/V axis is specified and patterned and may provide insight intothe evolution of the A/V axis in bilaterians.