A RE-EXPLORATION OF THE ORIGIN OF NEURONS

这项研究的目的是重新探索中枢神经系统细胞神经元的发育起源。普遍持有的观点是，所有神经元都来自外胚层，这是胚胎发生过程中三个主要胚层之一。基于大量的命运图谱和细胞谱系研究，这一结论无疑对大多数神经元是正确的，但对所有神经元都是正确的吗？我最近对果蝇黑腹果蝇中线中胚层细胞（MMCs）的研究提出了一个有趣的假设，即具有神经元功能的细胞不一定总是来自外胚层。这一假设将在拟议的MMCs中得到严格检验，MMCs是苍蝇中的一组20个细胞，它们在起源上明确是中胚层的，但却表现出许多神经元特性。它们有一个突出的细胞体，两个主要突将特定的神经投射到特定的骨骼肌，表达几种神经特异性标记物，具有电压依赖性通道，接受突触样输入，并影响几种目标组织。本研究的两个目的是解决神经元状态的剩余标准，即mmc是否表达和释放神经递质样分子。成功的结果将提供第一个神经元起源于非外胚层谱系的明确例子。

The goal of this research is to re-explore the developmental origin of neurons, the cells of the central nervous system. The universally held view is that all neurons arise from the ectoderm, one of the three primary germ layers during embryogenesis. This conclusion, based on numerous fate mapping and cell lineage studies, is undoubtably true for the majority of neurons, but is it true for all neurons? My recent work on the Midline Mesodermal Cells (MMCs) in fruit fly Drosophila melanogaster raises the interesting hypothesis that cells with a neuronal function need not always be ectodermally derived. This hypothesis will be critically examined in the proposed using the MMCs, a set of 20 cells in flies which are unequivocally mesodermal in origin yet exhibit a number of neuronal properties. They have a prominent cell body, two primary processes projecting out a specific nerve to a specific skeletal muscle, express several neural-specific markers, have voltage dependent channels, receive synaptic-like inputs, and affect several target tissues. The two aims in this study address the remaining criteria for neuronal status, namely whether the MMCs express and release neurotransmitter-like molecules. Successful results will provide the first clear cut example of neurons arising from a non-ectodermal lineage.