A gene expression fingerprint of C. elegans embryonic motor neurons.

Background: Differential gene expression specifies the highly diverse cell types that constitute the nervous system. With its sequenced genome and simple, well-defined neuroanatomy, the nematode C. elegans is a useful model system in which to correlate gene expression with neuron identity. The UNC-4 transcription factor is expressed in thirteen embryonic motor neurons where it specifies axonal morphology and synaptic function. These cells can be marked with an unc-4::GFP reporter transgene. Here we describe a powerful strategy, Micro-Array Profiling of C. elegans cells (MAPCeL), and confirm that this approach provides a comprehensive gene expression profile of unc-4::GFP motor neurons in vivo. Results: Fluorescence Activated Cell Sorting (FACS) was used to isolate unc-4::GFP neurons from primary cultures of C. elegans embryonic cells. Microarray experiments detected 6,217 unique transcripts of which ~1,000 are enriched in unc-4::GFP neurons relative to the average nematode embryonic cell. The reliability of these data was validated by the detection of known cell-specific transcripts and by expression in UNC-4 motor neurons of GFP reporters derived from the enriched data set. In addition to genes involved in neurotransmitter packaging and release, the microarray data include transcripts for receptors to a remarkably wide variety of signaling molecules. The added presence of a robust array of G-protein pathway components is indicative of complex and highly integrated mechanisms for modulating motor neuron activity. Over half of the enriched genes (537) have human homologs, a finding that could reflect substantial overlap with the gene expression repertoire of mammalian motor neurons. Conclusion: We have described a microarray-based method, MAPCeL, for profiling gene expression in specific C. elegans motor neurons and provide evidence that this approach can reveal candidate genes for key roles in the differentiation and function of these cells. These methods can now be applied to generate a gene expression map of the C. elegans nervous system. Keywords: expression profile背景：基因差异表达造就了构成神经系统的高度多样化细胞类型。秀丽隐杆线虫（C. elegans）基因组已完成测序，且其神经解剖结构简洁明确，是用于关联基因表达与神经元身份的理想模式系统。转录因子UNC-4在13种胚胎运动神经元中表达，负责调控轴突形态与突触功能。可通过unc-4::GFP报告转基因对这些细胞进行标记。本文介绍了一种高效策略——秀丽隐杆线虫细胞芯片表达谱分析（Micro-Array Profiling of C. elegans cells, MAPCeL），并证实该方法可在活体状态下全面获取unc-4::GFP标记运动神经元的基因表达谱。 结果：本研究借助荧光激活细胞分选术（Fluorescence Activated Cell Sorting, FACS）从秀丽隐杆线虫胚胎细胞原代培养物中分离出unc-4::GFP标记的神经元。芯片实验共检测到6217种独特转录本，其中约1000种在unc-4::GFP神经元中的表达量相较于普通线虫胚胎细胞显著富集。通过检测已知的细胞特异性转录本，以及验证富集数据集中的GFP报告基因在UNC-4运动神经元中的表达情况，证实了本数据的可靠性。除参与神经递质包装与释放的基因外，芯片数据还涵盖了针对大量信号分子的受体编码转录本。此外，芯片数据中包含大量G蛋白通路相关组分的转录本，这表明运动神经元的活性调控存在复杂且高度整合的机制。超过半数的富集基因（537个）存在人类同源基因，这一发现提示哺乳动物运动神经元的基因表达谱与秀丽隐杆线虫UNC-4运动神经元可能存在大量重叠。 结论：本研究介绍了一种基于芯片的方法MAPCeL，用于分析特定秀丽隐杆线虫运动神经元的基因表达谱，并证实该方法可筛选出在这些细胞的分化与功能中发挥关键作用的候选基因。该方法后续可用于构建秀丽隐杆线虫神经系统的基因表达图谱。 关键词：表达谱