Lowe Christopher J, Wu Mike, Salic Adrian, Evans Louise, Lander Eric, Stange-Thomann Nicole, Gruber Christian E, Gerhart John, Kirschner Marc
Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA.
Cell. 2003 Jun 27;113(7):853-65. doi: 10.1016/s0092-8674(03)00469-0.
The chordate central nervous system has been hypothesized to originate from either a dorsal centralized, or a ventral centralized, or a noncentralized nervous system of a deuterostome ancestor. In an effort to resolve these issues, we examined the hemichordate Saccoglossus kowalevskii and studied the expression of orthologs of genes that are involved in patterning the chordate central nervous system. All 22 orthologs studied are expressed in the ectoderm in an anteroposterior arrangement nearly identical to that found in chordates. Domain topography is conserved between hemichordates and chordates despite the fact that hemichordates have a diffuse nerve net, whereas chordates have a centralized system. We propose that the deuterostome ancestor may have had a diffuse nervous system, which was later centralized during the evolution of the chordate lineage.
脊索动物的中枢神经系统被推测起源于后口动物祖先的背侧集中化、腹侧集中化或非集中化的神经系统。为了解决这些问题，我们研究了半索动物科瓦列夫斯基柱头虫，并研究了参与脊索动物中枢神经系统模式形成的基因直系同源物的表达。所研究的所有22个直系同源物都以前后排列的方式在外胚层中表达，与在脊索动物中发现的排列方式几乎相同。尽管半索动物有一个分散的神经网，而脊索动物有一个集中化的系统，但半索动物和脊索动物之间的结构域拓扑结构是保守的。我们提出，后口动物祖先可能有一个分散的神经系统，该系统在脊索动物谱系的进化过程中后来集中化了。
