Sponge development and antiquity of animal pattern formation
Sponge development and antiquity of animal pattern formation
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DOI：
10.1093/icb/45.2.335
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发表时间：
2005-04-01
影响因子：
2.6
通讯作者：
Larroux, C
中科院分区：
文献类型：
--
作者：
Degnan, BM;Leys, SP;Larroux, C
所有现存动物的最后一个共同祖先拥有最基础的后生动物谱系——多孔动物——和动物界其他物种共有的特征。为了确定古老和保守的发育过程，我们一直在研究蠕形海绵Reniera的胚胎发生和变态。许多真生动物发育的主要特征在雷氏胚胎发生期间显示出来。具体来说，受精后有一段细胞分裂时期，几乎没有细胞生长，导致两种明显的细胞群体，以大小区分为微粒和大粒，以及命运：小细胞分化为纤毛细胞。随后是分化细胞活动的一段时间，产生由两层到三层组成的胚胎，其中至少有11个分化细胞群被分配到不同的层中，并在这些层中形成图案。尽管缺乏神经元和协调系统，这种组织产生的游动幼虫具有感知和响应周围环境的能力。在Reniera胚胎发生过程中，细胞模式最明显的例子是在幼虫未来的后极形成一个色素细胞环。色素细胞模式的形成有两个阶段，这两个阶段都可能需要大量细胞的运动，这显然是对形态梯度的反应。首先，色素细胞，最初覆盖胚胎表面，迁移到未来的后端，形成一个黑点。其次，细胞从斑点向外移动并重新排列成一个环。Reniera胚胎发生过程中表达的转录因子基因种类繁多，大部分属于后生动物特异性家族，包括POU、LIMHD、Pax、Bar、Prox2、NK-2、T-box、MEF-2、Fox、Sox、Ets和核激素受体家族。综上所述，这些观察结果表明，所有现存的后生动物谱系的最后一个共同祖先已经拥有了基本的调控遗传结构，以指导多种细胞类型的规范、模式和分化。这些分化的细胞中的一些可能被排列成局部的功能单位，即。，简单的组织。
The last common ancestor to all extant animals possessed features shared between the most basal metazoan lineage-Porifera-and the rest of the animal kingdom. To identify ancient and conserved developmental processes, we have been investigating embryogenesis and metamorphosis in the demosponge Reniera. Many of the cardinal features of eumetazoan development are displayed during Reniera embryogenesis. Specifically, after fertilization there is a period of cell division with little to no cell growth that results in two obvious cell populations distinguished by size as micromeres and macromeres, and by fate: the small cells differentiate into ciliated cells. This is followed by a period of differential cell activities that produces an embryo consisting of two then three layers, where at least 11 populations of differentiated cells are allocated into the different layers and patterned within these layers. This organization yields a swimming larva with the capacity to sense and respond to the surrounding environment, despite a lack of neurons and a coordinating system. During Reniera embryogenesis, the clearest example of cell patterning is the formation of a ring of pigment cells at the future posterior pole of the larva. Pigment cell pattern formation has two phases, both of which may require the movement of a large number of cells apparently in response to a morphogen gradient. First, pigmented cells, which initially cover the surface of the embryo, migrate to the future posterior end and form a dark spot. Second, the cells move outwards from the spot and rearrange into a ring. Numerous and diverse transcription factor genes are expressed during Reniera embryogenesis, most of which belong to metazoan-specific families and include members of POU, LIMHD, Pax, Bar, Prox2, NK-2, T-box, MEF-2, Fox, Sox, Ets, and nuclear hormone receptor families. In combination, these observations suggest that the last common ancestor to all extant metazoan lineages already possessed the basic regulatory genetic architecture to direct the specification, patterning and differentiation of multiple cell types. Some of these differentiated cells may have been arranged into localised functional units-i.e., simple tissues.