Evolutionary Origin of Vertebrate Neural Crest Gene Networks

描述(申请人提供)：脊椎动物的进化与神经脊的出现密切相关，神经脊是一种迁徙和多潜能的细胞群，它产生了脊椎动物的许多定义特征，包括明确定义的头部和外周神经节。在脊椎动物胚胎中，这些多能祖细胞形成于神经和非神经外胚层的边界。通过上调Msx1/2、Pax3/7和Zic等边界指定基因，诱导信号(如Wnt、BMP、成纤维细胞生长因子)建立神经板边界，这些相互作用被认为是神经脊形成的基础。这些边界基因反过来调节神经脊区指定者基因，如slug/Snail、FoxDS和SoxE家族。最后，神经脊说明符打开特定的下游靶点，使神经脊具有迁移性和多能性。本研究的目的是解决传统脊椎动物模型的神经脊基因调控网络是否保守于脊椎动物的底部。来自非脊椎动物的数据表明，这个网络是脊椎动物的新奇事物，神经脊的进化涉及到几个转录调节因子共同选择到脊椎动物祖先的神经板边界。我们将比较传统脊椎动物模型的神经脊基因调控网络与代表最原始的现存脊椎动物的海鳗、无颌鱼的神经脊椎基因调控网络。我们的初步结果表明，鳗鱼的许多神经脊衍生物、早期迁徙路线和神经脊基因网络的某些组成部分是保守的。我们将在这些分子在神经板边界部署的水平上测试保守性，以及执行类似功能的能力。为了探索导致这一重要细胞类型的进化从而导致脊椎动物特征起源的事件，这一建议将涉及以下具体目标：1)研究作为神经板边界和神经脊说明符的关键基因在无颌脊椎动物和有颌骨脊椎动物之间的序列和分布是否保守。2)通过吗啉介导的敲除选定的转录因子来建立网络内的连接；通过检查网络中其他基因的表达及其拯救功能丧失表型的能力来建立上位性。3)分离文昌鱼和七鳃鳗“指定子基因”的调控区域。

DESCRIPTION (provided by applicant): Evolution of vertebrates has been intimately linked to the advent of the neural crest, a migratory and multipotent cell population that gives rise to many defining characters of vertebrates, including a well-defined head and peripheral ganglia. These multipotent progenitor cells form at the border of neural and non-neural ectoderm in vertebrate embryos. The regulatory interactions predicted to underlie neural crest formation involve inductive signals (e.g. Wnt, BMP, FGF) that establish the neural plate border, by up-regulation of border specifier genes like Msx1/2, Pax3/7, and Zic. These border genes in turn regulate neural crest specifier genes like Slug/Snail, FoxDS and the SoxE family. Finally, neural crest specifiers turn on specific downstream targets that render the neural crest migratory and multipotent. The goal of the proposed study is to address whether the neural crest gene regulatory network of traditional vertebrate models is conserved to the base of vertebrates. Data from non-vertebrate chordates suggest this network is a vertebrate novelty and that neural crest evolution involved cooption of several transcriptional regulators to the neural plate border of the vertebrate ancestor. We will compare the neural crest gene regulatory network of traditional vertebrate models with that of sea lamprey, jawless fish that represent the most primitive extant vertebrates. Our preliminary results suggest that many neural crest derivatives, early migratory routes and some components of the neural crest gene network are conserved in lamprey. We will test for conservation at the level of deployment of these molecules at the neural plate border as well as ability to carry out similar functions. To explore events that led to the evolution of this important cell type and thus to the origin of vertebrate features, this proposal will address the following specific aims: 1) Examine whether key genes that function as neural plate border and neural crest specifiers are conserved in sequence and distribution between jawless and jawed vertebrates. 2) Establish connections within the network by morpholino-mediated knock-down of selected transcription factors; establish epistasis by examining the consequences on expression of other genes in the network and their ability to rescue the loss-of-function phenotype. 3) Isolate regulatory regions of amphioxus and lamprey "specifier genes."