Progressive acquisition of novel neural crest derivatives along the neural axis during vertebrate evolution

神经嵴是脊椎动物特有的一种细胞类型，被认为在 在脊椎动物进化中的作用，通过形成外周神经节和颌骨，从而促进捕食 和大脑的扩张。我们最近发现了一个“颅特异性”神经嵴转录 有颚脊椎动物（有颚动物）中的分支回路，使这一神经嵴群体充满了 独特的能力，缺乏从躯干神经嵴，形成颅面软骨，这是至关重要的下巴 阵在这里，我们建议检查是否同源基因表达在 七鳃鳗，一种无颌的基底脊椎动物（无颌）的头部迁移前神经嵴。我们 初步结果表明，这些基因中有许多是“失踪”的七鳃鳗的 前迁移颅神经嵴，从而挑战了假设， 在脊椎动物中产生了一个“新头”。因此，我们假设 脊椎动物进化过程中神经嵴衍生物的逐渐扩张。这 可能是通过在迁移前神经嵴中添加新的增强子元件而发生的， 赋予了这个细胞群体新的发育潜力。例如，七鳃鳗缺乏 一种迷走神经嵴，在颚口动物中形成肠神经系统。为了验证这一 假设，我们将进行谱系分析，分析转录因子和调控因子， 无颌类和有颌类的选定基因区域。我们会找出 增强子，剖析它们的调控输入，并测试这些区域驱动报告基因的能力。 在七鳃鳗中以及在斑马鱼中的跨物种表达。结果表明， 阐明了在脊椎动物进化过程中，在神经系统的保护伞下， 冠。

The neural crest is a uniquely vertebrate cell type that is thought to have played an important role in vertebrate evolution by forming peripheral ganglia and jaws, thus facilitating predation and expansion of the brain. We recently identified a “cranial-specific” neural crest transcriptional subcircuit in jawed vertebrates (gnathostomes) that imbues this neural crest population with the unique ability, absent from trunk neural crest, to form craniofacial cartilage that is critical for jaw formation. Here, we propose to examine whether homologous genes are expressed in the cranial premigratory neural crest of lamprey, a jawless basal vertebrate (agnathan). Our preliminary results suggest that many of these genes are “missing” from the lamprey's premigratory cranial neural crest, thus challenging the hypothesis that invention of neural crest in vertebrates gave rise to a “New Head”. Accordingly, we hypothesize that there was progressive expansion of neural crest derivatives during the course of vertebrate evolution. This likely occurred by addition of new enhancer elements into the premigratory neural crest that conferred novel developmental potential onto this cell population. As case in point, lamprey lack a vagal neural crest that in gnathostomes forms the enteric nervous system. To test this hypothesis, we will perform lineage analysis, analyze transcription factors and regulatory regions of selected genes across agnathan and gnathostomes. We will identify putative enhancers, dissect their regulatory inputs, and test the ability of these regions to drive reporter expression in lamprey as well as cross-species, in the zebrafish. The results promise to elucidate how new cell types arose during vertebrate evolution under the umbrella of the neural crest.