Lundell M J, Hirsh J
Department of Biology, University of Virginia, Charlottesville 22903.
Dev Biol. 1994 Oct;165(2):385-96. doi: 10.1006/dbio.1994.1261.
We present a high-resolution profile of the temporal and spatial immunoreactivity for dopamine and serotonin in the Drosophila embryonic CNS and the expression pattern of two enzymes important in their biosynthesis, DOPA decarboxylase (DDC) and tyrosine hydroxylase (TH). DDC performs the final catalytic step in the synthesis of both biogenic amines and TH is the rate-limiting enzymatic step in the synthesis of dopamine. We show that the DDC-expressing neurons synthesize either serotonin or dopamine, but not both, and that the two neuronal subtypes follow similar axonal pathways. In addition, we describe two DDC-expressing cell types that do not synthesize detectable levels of serotonin or dopamine. We also describe a novel set of TH-expressing neurons that are detected only during embryogenesis. The initial appearance of both enzymes and their metabolites during embryogenesis shows unexpected diversity. The onset of Ddc expression is heterogeneous, such that certain classes of cells express high levels of DDC several hours before others. High levels of TH immunoreactivity are observed at a time when DDC immunoreactivity is barely detectable. Despite low levels of DDC, both dopamine and serotonin are first detected at the earliest stages of DDC expression. We discuss the implications of these observations in the differentiation of dopamine and serotonin neurons.
我们展示了果蝇胚胎中枢神经系统中多巴胺和血清素的时空免疫反应性的高分辨率图谱，以及两种在其生物合成中起重要作用的酶——多巴脱羧酶（DDC）和酪氨酸羟化酶（TH）的表达模式。DDC在两种生物胺的合成中执行最后的催化步骤，而TH是多巴胺合成中的限速酶促步骤。我们发现，表达DDC的神经元要么合成血清素，要么合成多巴胺，但不会同时合成两者，并且这两种神经元亚型遵循相似的轴突路径。此外，我们描述了两种表达DDC的细胞类型，它们不会合成可检测水平的血清素或多巴胺。我们还描述了一组仅在胚胎发生期间被检测到的新型表达TH的神经元。胚胎发生过程中这两种酶及其代谢产物的最初出现显示出意想不到的多样性。Ddc表达的起始是异质性的，以至于某些细胞类别在其他细胞之前数小时就表达高水平的DDC。在DDC免疫反应性几乎无法检测到时，观察到高水平的TH免疫反应性。尽管DDC水平较低，但多巴胺和血清素在DDC表达的最早阶段就首次被检测到。我们讨论了这些观察结果对多巴胺和血清素神经元分化的影响。
