Precraniate origin of cranial motoneurons
Precraniate origin of cranial motoneurons
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DOI：
10.1073/pnas.0600805103
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发表时间：
2006-06-06
影响因子：
11.1
通讯作者：
Brunet, Jean-Francois
中科院分区：
文献类型：
--
作者：
Dufour, Heloise D.;Chettouh, Zoubida;Brunet, Jean-Francois
颅头由颅感觉神经元和运动神经元支配。颅脑感觉神经元起源于神经性的安慰剂和神经脊，被视为对满足颅脑“新头”的进食和呼吸需求至关重要的进化创新。相比之下，位于后脑并驱动头部的颅运动神经元的系统发育状态尚不清楚。在这里，我们表明，这些运动神经元实际上是同源的固位后变态形式的海鞘运动神经元。成体肠囊的运动神经元位于脑神经节和与巨大的“鳃篮”相关的支配肌肉中，表达转录因子CiPhox2和CiTbx20，它们的脊椎动物同源基因共同定义了鳃内脏类的颅运动神经元。此外，Ciona的变性后运动神经元起源于幼虫时期搁置的后脑，并通过其位置(前额叶感觉囊的尾部)以及CiPhox2和CiHox1的共同表达来定义，它们的同源基因共同标记脊椎动物的后脑。这些数据揭示，变质后的海鞘脑被认为是一种衍生特征，实际上对应于脊椎动物的后脑，并将脑神经的进化起源推后到颅骨起源之前。
The craniate head is innervated by cranial sensory and motor neurons. Cranial sensory neurons stem from the neurogenic placodes and neural crest and are seen as evolutionary innovations crucial in fulfilling the feeding and respiratory needs of the craniate '' new head.'' In contrast, cranial motoneurons that are located in the hindbrain and motorize the head have an unclear phylogenetic status. Here we show that these motoneurons are in fact homologous to the motoneurons of the sessile postmetamorphic form of ascidians. The motoneurons of adult Ciona intestinalis, located in the cerebral ganglion and innervating muscles associated with the huge '' branchial basket,'' express the transcription factors CiPhox2 and CiTbx20, whose vertebrate orthologues collectively define cranial motoneurons of the branchiovisceral class. Moreover, Ciona's postmetamorphic motoneurons arise from a hindbrain set aside during larval life and defined as such by its position (caudal to the prosensephalic sensory vesicle) and coexpression of CiPhox2 and CiHox1, whose orthologues collectively mark the vertebrate hindbrain. These data unveil that the postmetamorphic ascidian brain, assumed to be a derived feature, in fact corresponds to the vertebrate hindbrain and push back the evolutionary origin of cranial nerves to before the origin of craniates.