Genomic control of neural crest identity by signaling systems

项目总结/摘要 神经嵴是一种胚胎干细胞群，可以产生多种衍生物，包括大多数 颅面骨骼神经嵴细胞的形成受基因调控网络（GRN）控制 这赋予了这些祖细胞独特的特征，包括多能性和迁移能力。 这种复杂的分子程序由细胞外信号调节，确保精确的空间控制， 神经嵴规格特别是，无翅（Wnt）信号通路已被证明发挥关键作用， 在建立颅面细胞类型中的作用。尽管这一信号通路的重要性，只有少数 在神经嵴GRN内已经鉴定出直接的Wnt靶。此外，我们还缺乏一种机械的 了解Wnt如何与其他信号系统合作，如骨形态发生蛋白 (BMP)在早期神经嵴发育过程中，为了鉴定经典Wnt信号传导的新靶点，我们 研究了Wnt核效应子Lef 1和β-catenin在新生鸟类神经嵴中的基因组占有率 细胞这项分析揭示了多个神经嵴基因，这些基因通过组织特异性Wnt- 应答增强子。有趣的是，我们发现Lef 1/β-catenin占据的基因组区域也 含有Smads的多个结合基序，BMP信号的核效应器。因此我们 假设典型Wnt与BMPs合作在神经板处启动神经嵴基因GRN 边境我们将通过（a）鉴定神经嵴GRN中的直接Wnt靶基因;（B） 定义Wnt和BMP信号系统的组合输入如何影响神经嵴的输出 增强子;和（c）确定Wnt和BMP的效应子如何相互作用以控制基因表达。的 该提案的首要目标是定义环境线索如何影响基因组中的基因表达- 广泛的方式来调节细胞身份。我们预计，这项建议的结果将提供一个 增强子如何整合来自不同信号系统的输入以激活复合物的综合模型 转录程序。这项工作中揭示的机制不仅会影响组织工程， 还告知与人类健康相关的细胞身份的异常变化，例如癌症， 先天性畸形

PROJECT SUMMARY / ABSTRACT The neural crest is an embryonic stem cell population that gives rise to multiple derivatives, including most of the craniofacial skeleton. The formation of neural crest cells is controlled by a gene regulatory network (GRN) that endows these progenitor cells with their unique features, including multipotency and the ability to migrate. This complex molecular program is modulated by extracellular signals that ensure precise spatial control of neural crest specification. In particular, the Wingless (Wnt) signaling pathway has been shown to play a pivotal role in the establishment of craniofacial cell types. Despite the importance of this signaling pathway, only a few direct Wnt targets have been identified within the neural crest GRN. Furthermore, we also lack a mechanistic understanding of how Wnts cooperate with other signaling systems, such as the Bone Morphogenetic Protein (BMP) pathway, during early neural crest development. To identify novel targets of canonical Wnt signaling, we surveyed the genomic occupancy of Wnt nuclear effectors Lef1 and β-catenin in nascent avian neural crest cells. This analysis uncovered multiple neural crest genes that are controlled via tissue-specific Wnt- responsive enhancers. Intriguingly, we found that the genomic regions occupied by both Lef1/β-catenin also contained multiple binding motifs for Smads, the nuclear effectors of BMP signaling. Accordingly, we hypothesize that canonical Wnts cooperate with BMPs to initiate the neural crest gene GRN at the neural plate border. We will test this hypothesis by (a) identifying the direct Wnt target genes in the neural crest GRN; (b) defining how combinatorial input of Wnt and BMP signaling systems affects the output of the neural crest enhancers; and (c) determining how effectors of Wnts and BMPs interact to control gene expression. The overarching goal of this proposal is to define how environmental cues impact gene expression in a genome- wide manner to modulate cell identity. We anticipate that the findings of this proposal will provide a comprehensive model of how enhancers integrate inputs from distinct signaling systems to activate complex transcriptional programs. The mechanisms uncovered in this work will impact not only tissue engineering but also inform upon abnormal shifts in cell identity that are relevant to human health, such as cancer and congenital malformations.