Modrell Melinda S, Tidswell Olivia R A, Baker Clare V H
Department of Physiology, Development and Neuroscience, University of Cambridge, Anatomy Building, Downing Street, Cambridge CB2 3DY, UK.
Department of Physiology, Development and Neuroscience, University of Cambridge, Anatomy Building, Downing Street, Cambridge CB2 3DY, UK.
Dev Biol. 2017 Nov 1;431(1):48-58. doi: 10.1016/j.ydbio.2017.08.017. Epub 2017 Aug 15.
The lateral line system is a useful model for studying the embryonic and evolutionary diversification of different organs and cell types. In jawed vertebrates, this ancestrally comprises lines of mechanosensory neuromasts over the head and trunk, flanked on the head by fields of electrosensory ampullary organs, all innervated by lateral line neurons in cranial lateral line ganglia. Both types of sense organs, and their afferent neurons, develop from cranial lateral line placodes. Current research primarily focuses on the posterior lateral line primordium in zebrafish, which migrates as a cell collective along the trunk; epithelial rosettes form in the trailing zone and are deposited as a line of neuromasts, within which hair cells and supporting cells differentiate. However, in at least some other teleosts (e.g. catfishes) and all non-teleosts, lines of cranial neuromasts are formed by placodes that elongate to form a sensory ridge, which subsequently fragments, with neuromasts differentiating in a line along the crest of the ridge. Furthermore, in many non-teleost species, electrosensory ampullary organs develop from the flanks of the sensory ridge. It is unknown to what extent the molecular mechanisms underlying neuromast formation from the zebrafish migrating posterior lateral line primordium are conserved with the as-yet unexplored molecular mechanisms underlying neuromast and ampullary organ formation from elongating lateral line placodes. Here, we report experiments in an electroreceptive non-teleost ray-finned fish, the Mississippi paddlefish Polyodon spathula, that suggest a conserved role for Notch signaling in regulating lateral line organ receptor cell number, but potentially divergent roles for the fibroblast growth factor signaling pathway, both between neuromasts and ampullary organs, and between paddlefish and zebrafish.
侧线系统是研究不同器官和细胞类型的胚胎发育及进化多样性的有用模型。在有颌脊椎动物中，其祖先形式包括头部和躯干上的机械感觉神经丘线，头部两侧有电感觉壶腹器官区域，所有这些都由颅侧线神经节中的侧线神经元支配。这两种类型的感觉器官及其传入神经元均由颅侧线基板发育而来。目前的研究主要集中在斑马鱼的后侧线原基，它作为一个细胞群体沿躯干迁移；上皮玫瑰花结在尾区形成，并作为一排神经丘沉积下来，其中毛细胞和支持细胞在神经丘内分化。然而，在至少一些其他硬骨鱼（如鲶鱼）和所有非硬骨鱼中，颅神经丘线是由伸长形成感觉嵴的基板形成的，随后感觉嵴分裂，神经丘沿嵴顶呈线状分化。此外，在许多非硬骨鱼物种中，电感觉壶腹器官从感觉嵴的侧面发育而来。目前尚不清楚斑马鱼迁移的后侧线原基形成神经丘的分子机制与尚未探索的由伸长的侧线基板形成神经丘和壶腹器官的分子机制在多大程度上是保守的。在此，我们报告了对一种具有电感受能力的非硬骨辐鳍鱼——密西西比匙吻鲟（Polyodon spathula）的实验，该实验表明Notch信号在调节侧线器官受体细胞数量方面具有保守作用，但成纤维细胞生长因子信号通路在神经丘和壶腹器官之间以及匙吻鲟和斑马鱼之间可能具有不同作用。
