Genomic control of neural crest identity by signaling systems

项目摘要/摘要 神经脊是一个胚胎干细胞群体，它能产生多种衍生品，包括大多数 头面部骨骼。神经脊细胞的形成受基因调控网络(GRN)的控制 这赋予了这些祖细胞独特的功能，包括多能性和迁移能力。 这一复杂的分子程序受细胞外信号的调制，确保了对 神经脊规格。特别是，无翼(Wnt)信号通路已被证明发挥着关键作用 在建立颅面细胞类型中的作用。尽管这条信号通路很重要，但只有少数 直接的Wnt靶点已经在神经脊GRN内被识别出来。此外，我们还缺乏一种机械的 了解WNTS如何与其他信号系统合作，如骨形态发生蛋白 (BMP)途径，在神经脊发育的早期。为了识别规范的Wnt信号的新靶点，我们 Wnt核效应因子Lef1和β-catenin在新生禽类神经棘中的基因组占有率 细胞。这项分析发现了多个神经脊基因，这些基因是通过组织特异性Wnt- 反应性增强剂。有趣的是，我们发现Lef1/β-catenin占据的基因组区域也 包含BMP信号的核效应因子Smads的多个结合基序。因此，我们 假设规范的WNTs与BMPs合作在神经板启动神经脊基因GRN 边界。我们将通过(A)确定神经脊GRN中的直接Wnt靶基因来验证这一假设；(B) 确定WNT和BMP信号系统的组合输入如何影响神经脊的输出 以及(C)确定WNTS和BMP的效应器如何相互作用以控制基因表达。这个 这项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的身份。我们预计这项提案的结果将提供一个 增强器如何集成来自不同信号系统的输入以激活复杂信号的全面模型 转录程序。这项工作中发现的机制不仅将影响组织工程学，而且 还可以通知与人类健康相关的细胞标识的异常变化，如癌症和 先天畸形。

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.