Merritt D J, Whitington P M
Department of Zoology, University of New England, Amidale, New South Wales, Australia.
J Neurosci. 1995 Mar;15(3 Pt 1):1755-67. doi: 10.1523/JNEUROSCI.15-03-01755.1995.
The peripheral nervous system (PNS) of the Drosophila embryo is especially suited for investigating the specification of neuronal identity: the PNS consists of a relatively simple but diverse set of individually identified sensory neurons; mutants, including embryonic lethals, can be readily generated and analyzed; and axon growth can potentially be followed from the earliest stages. We have developed a staining method to reveal the central projections of the full set of sensory neurons in the preterminal abdominal segments of the embryo. The sensory neurons exhibit modality-specific axonal projections in the CNS. The axons of external sense (es) organ neurons, primarily tactile in function, are restricted to a particular region within each neuromere and exhibit a somatotopic mapping within the CNS. The axons of stretch-receptive chordotonal (ch) organs project into a discrete longitudinal fascicle. Sensory neurons with multiple-branched dendrites (md neurons) project into a separate fascicle. A small number of md neurons have distinctive dorsal-projecting axonal processes in the CNS. A classification of sensory neurons based on their axon morphology correlates closely with the identity of the proneural gene responsible for their generation, suggesting that proneural genes play a central role in determining neuronal identity in the PNS of the embryo.
果蝇胚胎的外周神经系统（PNS）特别适合用于研究神经元身份的特化：PNS由一组相对简单但多样的、可逐个识别的感觉神经元组成；包括胚胎致死突变体在内的突变体能够很容易地产生并进行分析；而且从最早阶段就有可能追踪轴突生长。我们开发了一种染色方法，以揭示胚胎终末腹部节段中全套感觉神经元的中枢投射。感觉神经元在中枢神经系统中表现出模式特异性的轴突投射。外部感觉（es）器官神经元的轴突主要起触觉作用，局限于每个神经节内的特定区域，并在中枢神经系统内呈现躯体定位图谱。伸展感受性弦音器（ch）器官的轴突投射到一个离散的纵向束中。具有多分支树突的感觉神经元（md神经元）投射到一个单独的束中。少数md神经元在中枢神经系统中有独特的背向投射轴突。基于轴突形态对感觉神经元进行的分类与负责其产生的原神经基因的身份密切相关，这表明原神经基因在决定胚胎PNS中的神经元身份方面起着核心作用。
