Evolutionary Origin of Vertebrate Neural Crest Gene Networks

描述（由申请人提供）：脊椎动物的进化与神经嵴的出现密切相关，神经嵴是一种迁移的多能细胞群，它产生了脊椎动物的许多特征，包括定义明确的头部和外周神经节。这些多能祖细胞形成于脊椎动物胚胎的神经和非神经外胚层的边缘。据预测，神经嵴形成的调控相互作用涉及诱导信号（如Wnt、BMP、FGF），这些信号通过上调边界指示基因（如Msx1/2、Pax3/7和Zic）来建立神经板边界。这些边缘基因反过来调节神经嵴指示基因，如Slug/Snail， FoxDS和SoxE家族。最后，神经嵴指示因子打开特定的下游目标，使神经嵴迁移和多能性。本研究的目的是探讨传统脊椎动物模型的神经嵴基因调控网络是否保守到脊椎动物的基础。来自非脊椎动物脊索动物的数据表明，这个网络是脊椎动物的新事物，神经嵴的进化涉及到脊椎动物祖先神经板边界的几个转录调节因子的选择。我们将比较传统脊椎动物模型的神经嵴基因调控网络与代表最原始的现存脊椎动物的海七鳃鳗的神经嵴基因调控网络。我们的初步结果表明，七鳃鳗有许多神经嵴衍生物、早期迁徙路线和神经嵴基因网络的一些组成部分是保守的。我们将测试这些分子在神经板边界部署水平上的守恒以及执行类似功能的能力。为了探索导致这种重要细胞类型进化的事件，从而揭示脊椎动物特征的起源，本提案将解决以下具体目标：1)研究作为神经板边界和神经嵴指示物的关键基因在无颌和有颌脊椎动物之间的序列和分布是否保守。2)通过morpholino介导的转录因子的敲除，在网络内建立连接；通过检查网络中其他基因表达的后果及其挽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“指示基因”的调控区。

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."