Developmental expression of transcription factor genes in a demosponge:: insights into the origin of metazoan multicellularity
Developmental expression of transcription factor genes in a demosponge:: insights into the origin of metazoan multicellularity
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DOI：
10.1111/j.1525-142x.2006.00086.x
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发表时间：
2006-03-01
影响因子：
2.9
通讯作者：
Degnan, BM
中科院分区：
文献类型：
--
作者：
Larroux, C;Fahey, B;Degnan, BM
海绵海绵被认为是动物王国中最基本的进化谱系的一部分。尽管海绵体的设计与其他后生动物有根本的不同，但它们的发育包括两侧对称动物和真后生动物胚胎发生的许多特征，即受精后经过一段时间的细胞分裂，产生不同的细胞群，通过类似原肠胚形成的过程分配到不同的细胞层并在这些层内形成图案。这些观察结果表明，所有活体动物的最后共同祖先（LCA）在发育上比人们广泛认为的更为复杂，并使用不对称细胞分裂和形态发生素梯度来建立胚胎内特定细胞的局部群体。在这里，我们证明了一系列转录因子基因类别的成员，其中许多似乎是后生动物特异性的，在演示海绵体Reniera的发育过程中表达，包括ANTP、Pax、POU、LIM-HD、Sox、核受体、Fox（叉头）、T-box、Mef2和Ets基因。对这些基因的系统发育分析表明，一些主要发育后生动物转录因子类别的起源和多样化都发生在海绵与后生动物其他部分分化之前。它们在海绵体发育过程中的表达表明，就像在当今复杂的后生动物中一样，这些基因可能在后生动物 LCA 的调控网络中发挥作用，以控制胚胎发生过程中的细胞规格和区域化基因表达。
Demosponges are considered part of the most basal evolutionary lineage in the animal kingdom. Although the sponge body plan fundamentally differs from that of other metazoans, their development includes many of the hallmarks of bilaterian and eumetazoan embryogenesis, namely fertilization followed by a period of cell division yielding distinct cell populations, which through a gastrulation-like process become allocated into different cell layers and patterned within these layers. These observations suggest that the last common ancestor (LCA) to all living animals was developmentally more sophisticated than is widely appreciated and used asymmetric cell division and morphogen gradients to establish localized populations of specified cells within the embryo. Here we demonstrate that members of a range of transcription factor gene classes, many of which appear to be metazoan-specific, are expressed during the development of the demosponge Reniera, including ANTP, Pax, POU, LIM-HD, Sox, nuclear receptor, Fox (forkhead), T-box, Mef2, and Ets genes. Phylogenetic analysis of these genes suggests that not only the origin but the diversification of some of the major developmental metazoan transcription factor classes took place before sponges diverged from the rest of the Metazoa. Their expression during demosponge development suggests that, as in today's sophisticated metazoans, these genes may have functioned in the regulatory network of the metazoan LCA to control cell specification and regionalized gene expression during embryogenesis.