Analysis of EphA4 in the lesser spotted catshark identifies a primitive gnathostome expression pattern and reveals co-option during evolution of shark-specific morphology
Analysis of EphA4 in the lesser spotted catshark identifies a primitive gnathostome expression pattern and reveals co-option during evolution of shark-specific morphology
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DOI：
10.1007/s00427-004-0426-0
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发表时间：
2004-09-01
影响因子：
2.4
通讯作者：
Cohn, MJ
中科院分区：
文献类型：
--
作者：
Freitas, R;Cohn, MJ
Eph家族是结构相关的受体酪氨酸激酶（RTK）的最大已知组。每个Eph受体都有一个特定的Ephrin配体，这些配体的功能是在发育过程中定义空间边界。对小鼠、鸡、青蛙和斑马鱼胚胎中的EphA4的分析表明，该基因参与了许多发育过程，包括节段边界的维持、轴突引导、肢体发育、神经嵴迁移和耳的形成。为了确定哪些组成部分的EphA4功能可能是原始的颚口类，我们克隆EphA4从小点猫鲨（Scyliorhinus canicula），并检查其在鲨鱼胚胎发育过程中的表达模式。与报道的硬骨鱼和四足动物的模式一致，我们观察到EphA4在发育中的后脑和后来在鲨鱼胚胎的咽弓中的节段性表达。EphA4在感觉器官发生过程中也被检测到，在发育中的耳、眼、鼻凹和侧线中。EphA4表达的动态模式发生在鲨鱼鳍发育过程中，这表明在生长和图案化的鳍芽和组织分化的后期作用的早期作用。我们还观察到一些新的领域EphA4的表达，尚未在其他脊椎动物，包括外部鳃芽，真皮dendritis，中鳍和clapers报道。虽然这些结构域中的一些可能反映了EphA4表达对鲨鱼特异性特征发育的新位点的共同选择，但其他结构域更可能是在其他脊椎动物谱系中丢失的祖先表达模式。
The Eph family is the largest known group of structurally related receptor tyrosine kinases (RTKs). Each Eph receptor has a specific Ephrin ligand, and these function to define spatial boundaries during development. Analyses of EphA4 in mouse, chick, frog and zebrafish embryos have implicated this gene in a number of developmental processes, including maintenance of segmental boundaries, axon guidance, limb development, neural crest migration and patterning of the ear. In order to determine which components of EphA4 function may be primitive for gnathostomes, we cloned EphA4 from the lesser spotted catshark (Scyliorhinus canicula) and examined its expression pattern during shark embryonic development. Consistent with the patterns reported for bony fish and tetrapods, we observed segmental expression of EphA4 in the developing hindbrain and later in the pharyngeal arches of shark embryos. EphA4 was also detected during sensory organogenesis, in the developing ear, eye, nasal pits and lateral line. A dynamic pattern of EphA4 expression occurs during shark fin development, suggesting an early role in outgrowth and patterning of the fin buds and a later role in tissue differentiation. We also observed several novel domains of EphA4 expression that have not been reported in other vertebrates, including external gill buds, dermal denticles, median fins and claspers. While some of these domains may reflect co-option of EphA4 expression to novel sites for development of shark-specific characters, others are more likely to be ancestral patterns of expression that were lost in other vertebrate lineages.