Developmental origin of shark electrosensory organs
Developmental origin of shark electrosensory organs
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DOI：
10.1111/j.1525-142x.2006.05076.x
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发表时间：
2006-01-01
影响因子：
2.9
通讯作者：
Cohn, MJ
中科院分区：
文献类型：
--
作者：
Freitas, R;Zhang, GJ;Cohn, MJ
脊椎动物已经进化出电感受器，可以探测到皮肤表面的电刺激，并通过体位将它们传递到大脑。在软骨鱼中，电感觉系统由一个由壶腹器官组成的头侧网络组成，被称为洛伦兹尼壶腹，它可以在狩猎和导航时探测到极弱的电场。每个壶腹器官都由一个充满凝胶的表皮坑组成，其中包含感觉毛细胞，以及与初级传入神经元在坑底部的突触连接，这些突触连接有助于检测身体大区域的电压梯度。电感受器的发育起源和决定它们在脊椎动物头部空间排列的机制尚不清楚。我们分析了小斑点猫鲨（Scyliorhinus canicula）的电感受器发育，发现神经嵴谱系的两个标记Sox8和HNK1选择性地标记壶腹器官的感觉细胞。这是神经嵴产生电感觉细胞的第一个证据。我们还发现，头侧机械感觉和电感觉轴突的寻路遵循EphA4的表达模式，EphA4是骨鱼体内轴突和神经嵴细胞的一种众所周知的引导线索。编码EphA4配体的EphrinB2的表达标记了壶腹基在表皮中的起始位置，EphA4在周围的间质中表达。这些结果表明，epf - ephrin信号可能为鲨鱼电感觉系统发育过程中神经嵴迁移、轴突引导和胎盘形态形成建立了早期分子图谱。
Vertebrates have evolved electrosensory receptors that detect electrical stimuli on the surface of the skin and transmit them somatotopically to the brain. In chondrichthyans, the electrosensory system is composed of a cephalic network of ampullary organs, known as the ampullae of Lorenzini, that can detect extremely weak electric fields during hunting and navigation. Each ampullary organ consists of a gel-filled epidermal pit containing sensory hair cells, and synaptic connections with primary afferent neurons at the base of the pit that facilitate detection of voltage gradients over large regions of the body. The developmental origin of electroreceptors and the mechanisms that determine their spatial arrangement in the vertebrate head are not well understood. We have analyzed electroreceptor development in the lesser spotted catshark (Scyliorhinus canicula) and show that Sox8 and HNK1, two markers of the neural crest lineage, selectively mark sensory cells in ampullary organs. This represents the first evidence that the neural crest gives rise to electrosensory cells. We also show that pathfinding by cephalic mechanosensory and electrosensory axons follows the expression pattern of EphA4, a well-known guidance cue for axons and neural crest cells in osteichthyans. Expression of EphrinB2, which encodes a ligand for EphA4, marks the positions at which ampullary placodes are initiated in the epidermis, and EphA4 is expressed in surrounding mesenchyme. These results suggest that Eph-Ephrin signaling may establish an early molecular map for neural crest migration, axon guidance and placodal morphogenesis during development of the shark electrosensory system.