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

神经脊是一种独特的脊椎动物细胞类型，被认为在 在脊椎动物进化中的作用，形成外周神经节和颌骨，从而促进捕食 以及大脑的扩张。我们最近发现了一种“颅脑特有的”神经脊转录。 有颌脊椎动物(脊椎动物)中的亚回路，它向这种神经脊种群注入 独特的能力，没有躯干神经脊，形成对颌骨至关重要的头面部软骨 队形。在这里，我们建议检查同源基因是否在 七鳃鳗，一种无颌基脊椎动物(七鳃鳗属)的颅前游走神经脊。我们的 初步结果表明，这些基因中的许多都是七鳃鳗“缺失”的 迁徙前的脑神经脊，从而挑战了神经脊发明的假说 在脊椎动物中产生了一个“新头”。因此，我们假设有 脊椎动物进化过程中神经脊衍生物的渐进性扩展。这 可能是由于向迁移前的神经脊中添加了新的增强子元件而发生的 赋予了这个细胞群体新的发展潜力。举个例子，七鳃鳗缺乏 脊椎动物的一种迷走神经隆起，形成肠道神经系统。为了测试这一点 假设，我们将进行谱系分析，分析转录因子和调节 所选基因的区域横跨无齿口目和节口目。我们将确定推定的 增强者，剖析他们的监管投入，并测试这些地区推动记者的能力 在七鳃鳗和跨物种斑马鱼中的表达。这一结果有望 阐明新的细胞类型是如何在神经保护伞下的脊椎动物进化过程中产生的 克雷斯特。

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.