Department of Zoology, Graduate School of Science, Kyoto University, Kyoto, Japan.
Dev Growth Differ. 2020 Jun;62(5):301-310. doi: 10.1111/dgd.12660. Epub 2020 Mar 18.
The ascidian belongs to the sister group of vertebrates and shares many features with them. The gene regulatory network (GRN) controlling gene expression in ascidian embryonic development leading to the tadpole larva has revealed evolutionarily conserved gene circuits between ascidians and vertebrates. These conserved mechanisms are indeed useful to infer the original developmental programs of the ancestral chordates. Simultaneously, these studies have revealed which gene circuits are missing in the ascidian GRN; these gene circuits may have been acquired in the vertebrate lineage. In particular, the GRN responsible for gene expression in ectodermal cells of ascidian embryos has revealed the genetic programs that regulate the regionalization of the brain, formation of palps derived from placode-like cells, and differentiation of sensory neurons derived from neural crest-like cells. We here discuss how these studies have given insights into the evolution of these traits.
海鞘属于脊椎动物的姊妹群，与脊椎动物有许多共同特征。控制海鞘胚胎发育形成幼体的基因调控网络 (GRN) 揭示了海鞘和脊椎动物之间进化上保守的基因回路。这些保守的机制确实有助于推断原始脊索动物的发育程序。同时，这些研究还揭示了海鞘 GRN 中缺失的基因回路；这些基因回路可能是在脊椎动物谱系中获得的。特别是，负责调控海鞘胚胎外胚层细胞基因表达的 GRN 揭示了调控大脑区域化、由类基板细胞衍生的触须形成以及由类神经嵴细胞衍生的感觉神经元分化的遗传程序。在这里，我们讨论了这些研究如何深入了解这些特征的进化。
