The vertebrate phylotypic stage and an early bilaterian-related stage in mouse embryogenesis defined by genomic information.
The vertebrate phylotypic stage and an early bilaterian-related stage in mouse embryogenesis defined by genomic information.
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DOI：
10.1186/1741-7007-5-1
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发表时间：
2007-01-12
期刊：
影响因子：
5.4
通讯作者：
Sehara-Fujisawa A
中科院分区：
文献类型：
--
作者：
Irie N;Sehara-Fujisawa A
分类学上不同的脊椎动物的胚胎被认为经历了一个阶段，在这个阶段中它们在形态上彼此相似。这一“脊椎动物典型阶段”可能代表了脊椎动物共同祖先建立的基本脊椎动物体型。然而，关于什么时候出现的非典型阶段，以及它是否存在，仍然存在很大的争议。为了克服基于形态学比较的研究的局限性，我们探索了一种综合的定量方法，用于使用表达序列标签（EST）数据、基因本体（GO）和各种动物的可用基因组来定义约束阶段。如果在脊椎动物胚胎的异型阶段发生强烈的发育限制，那么在脊椎动物中保守的基因将在这个阶段高度表达。我们建立了一种新的方法来评估小鼠胚胎阶段的祖先的性质，不依赖于比较形态学。数值“祖先指数”显示小鼠在胚胎8.0-8.5天确实具有高度保守的胚胎期，这是咽弓和体节出现的时间。在此期间，小鼠显著表达GO决定的发育基因之间共享的脊椎动物。类似的分析揭示了两侧对称相关时期的存在，在此期间，两侧对称者之间共享的GO决定的发育基因在卵裂至原肠胚形成时期显着表达。通过我们的方法鉴定的与异型阶段相关的基因在胚胎发生中是必不可少的。我们的研究结果表明，中期胚胎阶段的小鼠确实是高度限制，支持的存在的发育型阶段。此外，这一候选阶段之前是一个假定的两侧对称祖先相关的时期。这些结果不仅支持发育沙漏模型，而且强调了von Baer提出的胚胎发生的层次方面。通过这种方法在各种动物中鉴定保守的阶段和组织将是一个强有力的工具，以检验典型阶段假说，并了解哪些类型的发育事件和基因集在进化上受到限制，以及它们如何限制动物基本身体计划的可能变化。
Embryos of taxonomically different vertebrates are thought to pass through a stage in which they resemble one another morphologically. This "vertebrate phylotypic stage" may represent the basic vertebrate body plan that was established in the common ancestor of vertebrates. However, much controversy remains about when the phylotypic stage appears, and whether it even exists. To overcome the limitations of studies based on morphological comparison, we explored a comprehensive quantitative method for defining the constrained stage using expressed sequence tag (EST) data, gene ontologies (GO), and available genomes of various animals. If strong developmental constraints occur during the phylotypic stage of vertebrate embryos, then genes conserved among vertebrates would be highly expressed at this stage. We established a novel method for evaluating the ancestral nature of mouse embryonic stages that does not depend on comparative morphology. The numerical "ancestor index" revealed that the mouse indeed has a highly conserved embryonic period at embryonic day 8.0–8.5, the time of appearance of the pharyngeal arch and somites. During this period, the mouse prominently expresses GO-determined developmental genes shared among vertebrates. Similar analyses revealed the existence of a bilaterian-related period, during which GO-determined developmental genes shared among bilaterians are markedly expressed at the cleavage-to-gastrulation period. The genes associated with the phylotypic stage identified by our method are essential in embryogenesis. Our results demonstrate that the mid-embryonic stage of the mouse is indeed highly constrained, supporting the existence of the phylotypic stage. Furthermore, this candidate stage is preceded by a putative bilaterian ancestor-related period. These results not only support the developmental hourglass model, but also highlight the hierarchical aspect of embryogenesis proposed by von Baer. Identification of conserved stages and tissues by this method in various animals would be a powerful tool to examine the phylotypic stage hypothesis, and to understand which kinds of developmental events and gene sets are evolutionarily constrained and how they limit the possible variations of animal basic body plans.
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DOI：
10.1002/jez.b.21033
发表时间：
2005-03-15
影响因子：
2.2
作者：
Hazkani-Covo, E;Wool, D;Graur, D
通讯作者：
Graur, D
DOI：
10.1002/jez.b.20003
发表时间：
2004-01-15
影响因子：
2.2
作者：
Sander, K;Schmidt-Ott, U
通讯作者：
Schmidt-Ott, U
DOI：
10.1098/rsbl.2003.0124
发表时间：
2004-02-07
影响因子：
4.7
作者：
Hughes, AL;Friedman, R
通讯作者：
Friedman, R
影响因子：
10.7
作者：
Albà, MM;Castresana, J
通讯作者：
Castresana, J
DOI：
10.1098/rspb.2002.2242
发表时间：
2003-02-22
影响因子：
4.7
作者：
Bininda-Emonds, ORP;Jeffery, JE;Richardson, MK
通讯作者：
Richardson, MK