Hong C S, Ganetzky B
Laboratory of Genetics, University of Wisconsin, Madison 53706.
J Neurosci. 1994 Sep;14(9):5160-9. doi: 10.1523/JNEUROSCI.14-09-05160.1994.
Genetic and molecular studies have identified two different sodium channel genes in Drosophila, para and DSC1. The functional contributions of the para-encoded channel have been inferred from analysis of mutant phenotypes. However, no mutations of DSC1 have been identified, so the in vivo functions of the channel it encodes are not yet known. To learn more about the possible functions of DSC1 in the Drosophila nervous system compared with those of para, we have characterized the expression patterns of these two sodium channel genes at embryonic, larval, pupal, and adult stages by tissue in situ hybridization, para encodes the predominant type of sodium channel and is ubiquitously transcribed throughout the CNS and PNS at all developmental stages. The expression pattern of DSC1 is very different from para during embryonic and larval stages during which there are very few DSC1-expressing cells in either the CNS or PNS. Double-labeling studies suggest that some of these cells are non-neuronal. However, in pupal and adult stages, para and DSC1 have completely overlapping patterns of expression in the CNS and retina. In the pupal and adult, PNS expression of these genes is still distinct because only para transcripts are detected in wing sensory neurons. The strong and widespread expression of DSC1 in the CNS of pupae and adults suggests that the DSC1 channels are likely to provide an important function in neurons during these stages. Since most, if not all, neurons in the pupal and adult CNS express both para and DSC1, these two sodium channel genes probably subserve distinct functions within these cells. Our results provide the background for elucidating the respective in vivo contributions of para and DSC1 to neuronal excitability and for dissecting the regulatory mechanisms that underlie their different patterns of expression.
遗传学和分子学研究已在果蝇中鉴定出两种不同的钠通道基因，即para和DSC1。para编码通道的功能贡献已通过对突变体表型的分析推断得出。然而，尚未鉴定出DSC1的突变，因此其编码通道的体内功能尚不清楚。为了更深入了解与para相比，DSC1在果蝇神经系统中的可能功能，我们通过组织原位杂交对这两种钠通道基因在胚胎、幼虫、蛹和成虫阶段的表达模式进行了表征。para编码主要类型的钠通道，在所有发育阶段均在中枢神经系统和外周神经系统中普遍转录。在胚胎和幼虫阶段，DSC1的表达模式与para非常不同，在此期间，中枢神经系统或外周神经系统中表达DSC1的细胞很少。双标记研究表明，其中一些细胞是非神经元细胞。然而，在蛹和成虫阶段，para和DSC1在中枢神经系统和视网膜中的表达模式完全重叠。在蛹和成虫阶段，这些基因在外周神经系统中的表达仍然不同，因为仅在翅感觉神经元中检测到para转录本。DSC1在蛹和成虫中枢神经系统中的强烈且广泛表达表明，DSC1通道可能在这些阶段的神经元中发挥重要作用。由于蛹和成虫中枢神经系统中的大多数（如果不是全部）神经元都同时表达para和DSC1，这两个钠通道基因可能在这些细胞中发挥不同的功能。我们的研究结果为阐明para和DSC1对神经元兴奋性的各自体内贡献以及剖析其不同表达模式背后的调控机制提供了背景。
