Somite number and vertebrate evolution.
Somite number and vertebrate evolution.
复制标题
体节数量和脊椎动物进化。
作者：
M. Richardson;S. Allen;G. Wright;A. Raynaud;J. Hanken
节数的变化是脊椎动物进化中一个重要但被忽视的特征。一些脊椎动物只有六个躯干椎骨，而另一些则有数百个。我们研究这种现象与最近的进化和发展模式。令人惊讶的是，椎骨数量的差异预示着在尾芽阶段，被认为是一个高度保守的（典型的）阶段不同的体节计数。因此体节数目违反了“发育沙漏”模型。我们认为，这是因为体节发生显示解偶联或解离的动物型基因编码的保守的位置字段。其他几个系统也显示出这种分离，包括四肢和羽毛。Bmp-7的表达模式表明鸡咽弓分离。这使得很难在所有物种中识别咽部发育或“咽部”的共同阶段。在进化过程中，菱形节的数量比体节的数量更稳定，这可能是因为在后脑中的分割和位置规范是相对相互依赖的。虽然发育机制是高度保守的，解离允许至少一些主要的进化变化，在异型阶段产生。
Variation in segment number is an important but neglected feature of vertebrate evolution. Some vertebrates have as few as six trunk vertebrae, while others have hundreds. We examine this phenomenon in relation to recent models of evolution and development. Surprisingly, differences in vertebral number are foreshadowed by different somite counts at the tailbud stage, thought to be a highly conserved (phylotypic) stage. Somite number therefore violates the 'developmental hourglass' model. We argue that this is because somitogenesis shows uncoupling or dissociation from the conserved positional field encoded by genes of the zootype. Several other systems show this kind of dissociation, including limbs and feathers. Bmp-7 expression patterns demonstrate dissociation in the chick pharyngeal arches. This makes it difficult to recognise a common stage of pharyngeal development or 'pharyngula' in all species. Rhombomere number is more stable during evolution than somite number, possibly because segmentation and positional specification in the hindbrain are relatively interdependent. Although developmental mechanisms are strongly conserved, dissociation allows at least some major evolutionary changes to be generated in phylotypic stages.
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影响因子：
2.7
作者：
Chapman, DL;Agulnik, I;Papaioannou, VE
通讯作者：
Papaioannou, VE
影响因子：
4.6
作者：
A. Burke;Craig E. Nelson;B. Morgan
通讯作者：
A. Burke;Craig E. Nelson;B. Morgan
改变小鼠分段突变体 kreisler (kr) 中菱形体特异性基因表达和舌骨分化。
DOI：
10.1242/dev.117.3.925
发表时间：
1993
期刊：
Development (Cambridge, England)
影响因子：
--
作者：
Frohman,MA;Martin,GR;Cordes,SP;Halamek,LP;Barsh,GS
通讯作者：
Barsh,GS
DOI：
10.1242/dev.104.supplement.197
发表时间：
1988
期刊：
Development (Cambridge, England)
影响因子：
--
作者：
Kimmel,CB;Sepich,DS;Trevarrow,B
通讯作者：
Trevarrow,B
影响因子：
2.7
作者：
ROS, MA;LYONS, GE;FALLON, JF
通讯作者：
FALLON, JF