Tissot M, Stocker R F
Department of Biology and Program in Neuroscience, University of Fribourg, Fribourg, Switzerland.
Prog Neurobiol. 2000 Sep;62(1):89-111. doi: 10.1016/s0301-0082(99)00069-6.
The nervous system of insects is profoundly reorganised during metamorphosis, affecting the fate of different types of neuron in different ways. Almost all adult motor neurons derive from larval motor neurons that are respecified for adult functions. A subset of larval motor neurons, those which mediate larval- or ecdysis-specific behaviours, die before and immediately after eclosion, respectively. Many adult interneurons develop from larval interneurons, whereas those related to complex adult sense organs originate during larval life from persisting embryonic neuroblasts. Sensory neurons of larvae and adults derive from essentially two distinct sources. Larval sensory neurons are formed in the embryonic integument and - with few exceptions - die during metamorphosis. Their adult counterparts, on the other hand, arise from imaginal discs. Special emphasis is given in this review to the metamorphic remodelling of persisting neurons, both at the input and output levels, and to the associated behavioural changes. Other sections deal with the programmed death of motor neurons and its causes, as well as with the metamorphic interactions between motor neurons and their target muscles. Remodelling and apoptosis of these two elements appear to be under independent ecdysteroid control. This review focusses on the two most thoroughly studied holometabolous species, the fruitfly Drosophila melanogaster and the tobacco hornworm moth Manduca sexta. While Manduca has a long tradition in neurodevelopmental studies due to the identification of many of its neurons, Drosophila has been increasingly used to investigate neural reorganisation thanks to neurogenetic tools and molecular approaches. The wealth of information available emphasises the strength of the insect model system used in developmental studies, rendering it clearly the most important system for studies at the cellular level.
昆虫的神经系统在变态过程中会发生深刻的重组，以不同方式影响不同类型神经元的命运。几乎所有成年运动神经元都源自为成年功能重新指定的幼虫运动神经元。一部分幼虫运动神经元，即那些介导幼虫或蜕皮特异性行为的神经元，分别在羽化前和羽化后立即死亡。许多成年中间神经元由幼虫中间神经元发育而来，而与复杂成年感觉器官相关的中间神经元则在幼虫期由持续存在的胚胎神经母细胞产生。幼虫和成虫的感觉神经元基本上来自两个不同的来源。幼虫感觉神经元在胚胎体表形成，除少数例外，在变态过程中死亡。另一方面，它们的成年对应物则起源于成虫盘。本综述特别强调了持续存在的神经元在输入和输出水平上的变态重塑，以及相关的行为变化。其他部分讨论了运动神经元的程序性死亡及其原因，以及运动神经元与其靶肌肉之间的变态相互作用。这两个元素的重塑和凋亡似乎受蜕皮甾类激素的独立控制。本综述重点关注两种研究最为深入的全变态物种，果蝇黑腹果蝇和烟草天蛾烟草天蛾。由于鉴定出了许多神经元，烟草天蛾在神经发育研究方面有着悠久的传统，而果蝇由于神经遗传学工具和分子方法，越来越多地被用于研究神经重组。现有的大量信息强调了发育研究中使用的昆虫模型系统的优势，使其显然成为细胞水平研究中最重要的系统。
