Does hair cell differentiation predate the vertebrate appearance?
Does hair cell differentiation predate the vertebrate appearance?
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DOI：
10.1016/j.brainresbull.2007.10.012
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发表时间：
2008-03-18
影响因子：
3.8
通讯作者：
Manni, Lucia
中科院分区：
文献类型：
--
作者：
Burighel, Paolo;Caicci, Federico;Manni, Lucia
一般认为，三个主要的脊索动物类群（被囊动物、头索动物和脊椎动物）起源于一个共同的祖先，具有脊索动物身体平面的基本特征，即神经管和脊索两侧有横纹肌肉系统。现在有越来越多的证据表明，被囊类，而不是头索动物，是脊椎动物的姐妹群。与此相关，被囊类动物的感觉结构类似于脊椎动物的基板或神经嵴。在这种情况下，我们在这里讨论的脊椎动物毛细胞，这是基板的起源，是否存在于祖先脊索动物的前体。海鞘被囊动物具有冠状器官，由一排机械感觉细胞组成，环绕着口管的基部。它的功能是监测进水流量。这些细胞是次级感觉细胞，即它们缺乏轴突并且与其胞体位于脑神经节中的神经元突触。它们伴随着支持细胞，并且在脊椎动物中，在迄今为止检查的物种中具有不同的形态：在一个目（Enterogona）中，它们是多纤毛的;在另一个目（Pleurogona）中，它们可能具有顶端装置，由一个或两个纤毛伴随着立体绒毛组成，其长度分级。因此，冠状细胞在形态、胚胎起源和排列方面与脊椎动物毛细胞非常相似，这表明它们起源于早期的脊索动物。我们正在继续我们的冠状器官在其他海鞘物种的研究，并在这里报告的新数据Botrylloides leachi，这符合模式的Pleurogona，特别是与以前发表的结果对其他botryllid海鞘。(c)2007年爱思唯尔公司All rights reserved.
It is generally accepted that the three main chordate groups (tunicates, cephalochordates and vertebrates) originated from a common ancestor having the basic features of the chordate body plan, i.e. a neural tube and a notochord flanked by striated musculature. There is now increasing evidence that tunicates, rather than cephalochordates, are the vertebrate sister-group. Correlated with this, tunicates have sensory structures similar to those derived from placodes or neural crest in vertebrates. In this context, we discuss here whether the precursors of vertebrate hair cells, which are placodal in origin, were present in ancestral chordates. The ascidian tunicates possess a coronal organ, consisting of a row of mechanosensory cells that runs around the base of the oral siphon. Its function is to monitor the incoming water flow. The cells are secondary sensory cells, i.e. they lack axons and synapse with neurons whose somata lie in the cerebral ganglion. They are accompanied by supporting cells and, as in vertebrates, have varying morphologies in the species so far examined: in one order (Enterogona), they are multiciliate; in the other (Pleurogona), they may possess an apical apparatus, consisting of one or two cilia accompanied by stereovilli, that are graded in length. Coronal cells thus resemble vertebrate hair cells closely in their morphology, embryonic origin and arrangement, which suggests they originated early in ancestral chordates. We are continuing our study of the coronal organ in other ascidian species, and report new data here on Botrylloides leachi, which conforms with the pattern of Pleurogona and, in particular, with previously published results on other botryllid ascidians. (c) 2007 Elsevier Inc. All rights reserved.