Evidence for the prepattern/cooption model of vertebrate jaw evolution
Evidence for the prepattern/cooption model of vertebrate jaw evolution
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DOI：
10.1073/pnas.1009304107
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发表时间：
2010-10-05
影响因子：
11.1
通讯作者：
Medeiros, Daniel Meulemans
中科院分区：
文献类型：
--
作者：
Cerny, Robert;Cattell, Maria;Medeiros, Daniel Meulemans
颌骨的出现是脊椎动物进化的一个转折点，因为它使原始脊椎动物能够捕获和处理大型的、能动的猎物。脊椎动物的颌骨由独立的背侧和腹侧骨骼组成，通过关节连接。这种结构是如何从无颚祖先的不相连的鳃杆进化而来的，这是脊椎动物进化中一个尚未解决的问题。为了了解这种进化转变的发展基础，我们研究了现代无颌鱼七鳃鳗中涉及脊椎动物咽部图案的12个基因的表达。我们发现嵌套表达的DLX基因，以及组合表达的Msx，手和GSC基因沿着背腹（DV）轴的七鳃鳗咽，表明gnathostome型咽图案的下巴出现之前演变。此外，我们发现，Bapx和Gdf 5/6/7，关键监管机构的联合形成有颚口类，不表示在七鳃鳗第一弓，而巴克斯，这是缺席的中间第一弓有颚口类，标志着这一领域的七鳃鳗。总之，这些数据支持一个新的情况下，下巴的演变，其中纳入Bapx和Gdf 5/6/7到一个预先存在的DV图案程序驱动下巴的演变，通过改变中间第一弓软骨细胞的身份。我们提出了这个“前模式/合作”模型作为替代目前的模型链接的演变下巴从头出现复杂的咽DV图案。
The appearance of jaws was a turning point in vertebrate evolution because it allowed primitive vertebrates to capture and process large, motile prey. The vertebrate jaw consists of separate dorsal and ventral skeletal elements connected by a joint. How this structure evolved from the unjointed gill bar of a jawless ancestor is an unresolved question in vertebrate evolution. To understand the developmental bases of this evolutionary transition, we examined the expression of 12 genes involved in vertebrate pharyngeal patterning in the modern jawless fish lamprey. We find nested expression of Dlx genes, as well as combinatorial expression of Msx, Hand and Gsc genes along the dorso-ventral (DV) axis of the lamprey pharynx, indicating gnathostome-type pharyngeal patterning evolved before the appearance of the jaw. In addition, we find that Bapx and Gdf5/6/7, key regulators of joint formation in gnathostomes, are not expressed in the lamprey first arch, whereas Barx, which is absent from the intermediate first arch in gnathostomes, marks this domain in lamprey. Taken together, these data support a new scenario for jaw evolution in which incorporation of Bapx and Gdf5/6/7 into a preexisting DV patterning program drove the evolution of the jaw by altering the identity of intermediate first-arch chondrocytes. We present this "Pre-pattern/Cooption" model as an alternative to current models linking the evolution of the jaw to the de novo appearance of sophisticated pharyngeal DV patterning.