A Mechanistic Model for the Evolution of the Vertebrate Head Skeleton

脊椎动物大约在5亿年前从小型滤食性蠕虫进化而来。自那以后，脊椎动物亚门已经成为分布最广泛的动物群体之一，导致了包括人类在内的各种物种的惊人多样性。脊椎动物成功的关键之一是强壮和高度适应性的脊椎动物头骨。尽管头部骨骼在脊椎动物进化中起着核心作用，但人们对它最初是如何形成的知之甚少。这个项目使用现代分子方法，通过分析三个关键物种骨骼发育的遗传机制，来解决这个长期存在的和以前难以解决的问题。第一种动物是文昌鱼，它是一种无脊椎动物，被视为与脊椎动物的蠕虫祖先高度相似的活化石。虽然以前认为缺乏脊椎动物类型的骨骼组织，但我们发现了令人兴奋的证据，这种组织可能是在其幼虫阶段形成的。第二种，七鳃鳗，是最古老的脊椎动物群体的活着的代表。第三种是非洲爪蛙，是一种很容易接近的脊椎动物模型，其头骨与我们的相似。通过现代分子方法在这些动物的胚胎和幼虫中的新应用，我们正在阐明驱动脊椎动物头部进化的遗传和发育变化。在此过程中，该工作为一名博士后学者、研究生和几名本科生提供培训，并为高中生提供实践研究经验。该项目还为本科生提供了通过高级实验室课程直接参与新颖基础研究的机会。最后，这项工作的结果将被纳入一门大型普通生物学课程的课程中，并通过科罗拉多大学自然历史博物馆的巡回展览向公众广泛传播。

Vertebrates evolved from small filter-feeding worms around a half-billion years ago. The vertebrate subphylum has since become one of the most widespread animal groups, giving rise to a stunning diversity of species, including humans. One of the keys to vertebrate success is the robust and highly adaptable vertebrate head skeleton. Despite the central role of the head skeleton in vertebrate evolution very little is known about how it first formed. This project uses modern molecular methods to address this long-standing and previously intractable question by analyzing the genetic mechanisms underlying skeletal development in three key species. The first animal, amphioxus, is an invertebrate regarded as a 'living fossil' highly similar to the worm-like ancestor of the vertebrates. While previously thought to lack a vertebrate-type skeletal tissue, we have found exciting evidence that such tissue may form during its larval phase. The second, the lamprey, is a living representative of the most ancient vertebrate group, the agnathans. The third, the African clawed frog, is an easily accessible model vertebrate with a head skeleton similar to our own. By the novel application of modern molecular methods to the embryos and larvae of these animals, we are elucidating the genetic and developmental changes driving the evolution of the vertebrate head. In the process, the work provides training for a postdoctoral scholar, graduate, and several undergraduate students, as well as hands-on research experiences for high school students. The project also provides an opportunity for undergraduates to participate directly in novel basic research through an upper division lab course. Finally, the results of the work will be incorporated into the curriculum of a large general biology course and widely disseminated to the public through a traveling exhibit at the University of Colorado Museum of Natural History.