Kenny Nathan J, Namigai Erica K O, Dearden Peter K, Hui Jerome H L, Grande Cristina, Shimeld Sebastian M
Evolution and Development Research Group, Department of Zoology, University of Oxford, UK.
Int J Dev Biol. 2014;58(6-8):533-49. doi: 10.1387/ijdb.140080nk.
TGF-β signalling plays a key role in the patterning of metazoan body plans and growth. It is widely regarded as a 'module' capable of co-option into novel functions. The TGF-β pathway arose in the Metazoan lineage, and while it is generally regarded as well conserved across evolutionary time, its components have been largely studied in the Ecdysozoa and Deuterostomia. The recent discovery of the Nodal molecule in molluscs has underlined the necessity of untangling this signalling network in lophotrochozoans in order to truly comprehend the evolution, conservation and diversification of this key pathway. Three novel genome resources, the mollusc Patella vulgata, annelid Pomatoceros lamarcki and rotifer Brachionus plicatilis, along with other publicly available data, were searched for the presence of TGF-β pathway genes. Bayesian and Maximum Likelihood analyses, along with some consideration of conserved domain structure, was used to confirm gene identity. Analysis revealed conservation of key components within the canonical pathway, allied with extensive diversification of TGF-β ligands and partial loss of genes encoding pathway inhibitors in some lophotrochozoan lineages. We fully describe the TGF-β signalling cassette of a range of lophotrochozoans, allowing firm inference to be drawn as to the ancestral state of this pathway in this Superphylum. The TGF-β signalling cascade's reputation as being highly conserved across the Metazoa is reinforced. Diversification within the activin-like complement, as well as potential wide loss of regulatory steps in some Phyla, hint at specific evolutionary implications for aspects of this cascade's functionality in this Superphylum.
转化生长因子-β（TGF-β）信号传导在后生动物身体结构的形成和生长过程中发挥着关键作用。它被广泛认为是一个能够被用于新功能的“模块”。TGF-β信号通路出现在后生动物谱系中，虽然一般认为它在进化过程中得到了很好的保守，但它的组成部分主要是在蜕皮动物和后口动物中进行研究的。最近在软体动物中发现了Nodal分子，这凸显了梳理冠轮动物中这个信号网络的必要性，以便真正理解这个关键信号通路的进化、保守性和多样性。我们搜索了三种新的基因组资源，即软体动物笠贝、环节动物拉氏缨鳃虫和轮虫褶皱臂尾轮虫，以及其他公开可用的数据，以查找TGF-β信号通路基因的存在情况。使用贝叶斯分析和最大似然分析，并结合对保守结构域结构的一些考量，来确认基因身份。分析揭示了经典信号通路中关键成分的保守性，同时伴有TGF-β配体的广泛多样化以及一些冠轮动物谱系中编码信号通路抑制剂的基因部分丢失。我们全面描述了一系列冠轮动物的TGF-β信号盒，从而能够就这个超门中该信号通路的祖先状态得出可靠的推断。TGF-β信号级联在整个后生动物中高度保守的声誉得到了加强。激活素样补体中的多样化，以及某些门类中调控步骤可能的广泛缺失，暗示了该信号级联在这个超门中的功能方面具有特定的进化意义。
