Brachyury-downstream gene networks in the notochord

描述（由申请人提供）：转录因子Brachyury （Bra）在脊索形成中的作用在整个脊索动物门中得到了很好的记录和进化保守。然而，关于Bra直接或间接控制的转录因子，以及与Bra协同作用的因子在脊索发育和进化中的作用，目前还知之甚少。特别是，关于指导脊索表达的顺式调节模块（增强子）的结构、共同特征和调节方式的知识是不完整和贫乏的。我们利用海鞘（Ciona ninteinalis）提供的实验优势作为模型系统，从已经被描述为Bra靶点的基因和与Bra关系未知的基因中分离和表征一系列脊索增强子。我们从对脊索增强因子的比较分析中收集的初步数据使我们假设，Ciona脊索的形成依赖于其他的、大多未表征的脊索转录因子，这些转录因子分为两类：Bra-下游因子，由Bra直接或间接控制并作为其转录中介和与Bra协同作用的因子。我们将通过以下具体目标来检验这些假设：(1)分离脊索表达所需的最小调控序列；(2)确定控制最小增强子序列的激活因子，并研究其在脊索发育中的作用；(3)依次识别控制选定脊索激活因子的增强子。

DESCRIPTION (provided by applicant): The role of the transcription factor Brachyury (Bra) in notochord formation is well documented and evolutionarily conserved throughout the chordate phylum. However, still little is known about the transcription factors controlled directly or indirectly by Bra and about the function of factors acting in concert with Bra in notochord development and evolution. In particular, the knowledge of structure, common features and modalities of regulation of cis-regulatory modules (enhancers) directing expression in the notochord is fragmentary and poor. We have exploited the experimental advantages offered by the ascidian Ciona intestinalis as a model system to isolate and characterize a collection of notochord enhancers from genes that have already been described as Bra targets and from genes whose relationship with Bra is unknown. Our preliminary data, gathered from the comparative analysis of the notochord enhancers, lead us to hypothesize that notochord formation in Ciona relies upon additional, mostly uncharacterized notochord transcription factors that fall into two categories: Bra-downstream factors, controlled directly or indirectly by Bra and acting as its transcriptional intermediaries and factors acting in concert with Bra. We will test these hypotheses through the following specific aims: (1) Isolate minimal regulatory sequences necessary for notochord expression; (2) Identify the activators controlling the minimal enhancer sequences and study their role in notochord development; (3) Identify the enhancers controlling, in turn, selected notochord activators. The broad scope of the proposed research is to rapidly untangle the gene networks underlying the different steps of notochord development and differentiation and to gain valuable insights into the molecular mechanisms controlling gene expression in the notochord during its formation and evolution.