Brachyury-downstream gene networks in the notochord

描述（由申请人提供）：脊索在所有脊索动物胚胎中起着支持和形成发育身体计划的基本作用。转录因子Brachyury是脊索形成所必需的，并且已知其在脊索动物胚胎中激活许多脊索基因的转录，所述脊索动物胚胎与海葵和人类不同。Brachyury编码区的突变与脊椎畸形和脊柱裂风险增加有关。此外，最近的研究表明，人类Brachyury基因座的重复与家族性脊索瘤（一种恶性脊索源性肿瘤）之间存在直接关联。关于Brachyury下游基因级联的知识，特别是Brachyury下游或与Brachyury协同作用的转录因子的身份仍然是零碎的。我们使用的基础脊索动物玻璃海鞘（海鞘），一个简单而信息丰富的脊椎动物相对，作为一个访问，快速发展的模型系统，用于识别进化保守的转录激活因子，并阐明其层次关系与玻璃海鞘Brachyury（Ci-Bra）。我们的初步数据，从脊索顺式调节模块（CRM）的结构和功能的比较分析，并从特定的搜索脊索转录因子从玻璃海鞘进化保守的脊椎动物收集，使我们假设：1）Ci-Bra间接控制其部分靶点，2）Ci-Bra通过与其他转录因子协同作用来控制其部分靶标。我们建议对我们实验室最近发现的迟发型脊索转录因子进行表征。我们的主要目标是阐明这些因素在脊索发育中所起的作用，并阐明它们在Ci-Bra基因调控网络中的层次位置。我们的具体目标是：1）分析一个新发现的转录因子在脊索发育中的作用和靶点，以及它与Ci-Bra的关系：2）鉴定本实验室鉴定的控制脊索CRMs的激活因子，并研究它们在脊索发育中的功能; 3）通过分析Ci-Bra的一种潜在的转录中间体Ci-XBP-1，来表征Ci-Bra在脊索晚期分化中的作用，及其下游目标。拟议研究的广泛范围是利用玻璃海鞘的实验优势，快速获得对发育和进化过程中控制脊索基因表达的机制的基本见解。从更广泛的角度来看，这项研究旨在阐明Brachyury控制其靶基因的分子机制，这些靶基因在受损时会导致脊索畸形和脊索源性肿瘤发生。鉴于Brachyury在所有分析的脊索动物中脊索形成中的普遍作用，这些发现很可能适用于脊椎动物，包括人类。 公共卫生相关性：Brachyury是脊索形成所需的转录因子，脊索是一种支持和塑造所有脊索动物（包括人类）身体的结构。除了其发育作用外，Brachyury还是脊索瘤（恶性脊索源性肿瘤）的特异性标志物、免疫靶点和病原体。拟议的研究使用玻璃海鞘胚胎快速阐明Brachyury-下游转录因子，它们受Brachyury控制的方式，它们的功能及其靶基因。

DESCRIPTION (provided by applicant): The notochord plays a fundamental role in supporting and patterning the developing body plan in all chordate embryos. The transcription factor Brachyury is required for notochord formation and it is known to activate the transcription of numerous notochord genes in chordate embryos as different as sea squirts and humans. Mutations in the Brachyury coding region have been associated with vertebral malformations and increased risk of spina bifida. In addition, recent studies have indicated a direct association between the duplication of the human Brachyury locus and familial chordoma, a malignant notochord-derived tumor. The knowledge of the Brachyury-downstream gene cascade and, in particular, the identities of the transcription factors that act downstream of or in concert with Brachyury is still fragmentary. We use the basal chordate Ciona intestinalis (sea squirt), a simple yet informative vertebrate relative, as an accessible, fast-developing model system for identifying evolutionarily conserved transcriptional activators and for elucidating their hierarchical relationship with Ciona Brachyury (Ci-Bra). Our preliminary data, gathered from the comparative analysis of the structure and function of notochord cis-regulatory modules (CRMs) and from specific searches for notochord transcription factors evolutionarily conserved from Ciona to vertebrates, lead us to hypothesize that: 1) Ci-Bra controls part of its targets indirectly, via transcriptional intermediaries and 2) Ci-Bra controls part of its targets by acting synergistically with other transcription factors. We propose to characterize late-onset notochord transcription factors recently identified in our lab. Our main goals are to elucidate the role played by these factors in notochord development and to shed light on their hierarchical position within the Ci-Bra gene regulatory network. Our specific aims are: 1) Analyze the developmental role and targets of a newly identified transcription factor, and its relationship with Ci-Bra; 2) Identify the activators controlling the notochord CRMs identified in our lab and study their function in notochord development; 3) Characterize the role of Ci-Bra in late notochord differentiation through the analysis of one of its potential transcriptional intermediaries, Ci-XBP-1, and of its downstream targets. The broad scope of the proposed research is to exploit the experimental advantages of Ciona to rapidly gain basic insights into the mechanisms controlling gene expression in the notochord during development and evolution. In a wider perspective, this research aims to shed light on the molecular mechanisms employed by Brachyury to control its target genes, which, when compromised, are responsible for notochord malformations and notochord-derived tumorigenesis. Given the pervasive role of Brachyury in notochord formation in all chordates analyzed, it is likely that these findings will be applicable to vertebrates, including humans. PUBLIC HEALTH RELEVANCE: Brachyury is a transcription factor required for the formation of the notochord, a structure that supports and patterns the body of all chordates, including humans. In addition to its developmental role, Brachyury is also a specific marker, immunotherapeutic target and causative agent of chordomas, malignant notochord-derived tumors. The proposed studies use the Ciona embryo to rapidly shed light on Brachyury- downstream transcription factors, the way they are controlled by Brachyury, their function, and their target genes.