Bourane Steeve, Méchaly Ilana, Venteo Stéphanie, Garces Alain, Fichard Agnes, Valmier Jean, Carroll Patrick
INSERM U,583, 34091 Montpellier, France.
BMC Neurosci. 2007 Nov 19;8:97. doi: 10.1186/1471-2202-8-97.
The different sensory modalities temperature, pain, touch and muscle proprioception are carried by somatosensory neurons of the dorsal root ganglia. Study of this system is hampered by the lack of molecular markers for many of these neuronal sub-types. In order to detect genes expressed in sub-populations of somatosensory neurons, gene profiling was carried out on wild-type and TrkA mutant neonatal dorsal root ganglia (DRG) using SAGE (serial analysis of gene expression) methodology. Thermo-nociceptors constitute up to 80 % of the neurons in the DRG. In TrkA mutant DRGs, the nociceptor sub-class of sensory neurons is lost due to absence of nerve growth factor survival signaling through its receptor TrkA. Thus, comparison of wild-type and TrkA mutants allows the identification of transcripts preferentially expressed in the nociceptor or mechano-proprioceptor subclasses, respectively.
Our comparison revealed 240 genes differentially expressed between the two tissues (P < 0.01). Some of these genes, CGRP, Scn10a are known markers of sensory neuron sub-types. Several potential markers of sub-populations, Dok4, Crip2 and Grik1/GluR5 were further analyzed by quantitative RT-PCR and double labeling with TrkA,-B,-C, c-ret, parvalbumin and isolectin B4, known markers of DRG neuron sub-types. Expression of Grik1/GluR5 was restricted to the isolectin B4+ nociceptive population, while Dok4 and Crip2 had broader expression profiles. Crip2 expression was however excluded from the proprioceptor sub-population.
We have identified and characterized the detailed expression patterns of three genes in the developing DRG, placing them in the context of the known major neuronal sub-types defined by molecular markers. Further analysis of differentially expressed genes in this tissue promises to extend our knowledge of the molecular diversity of different cell types and forms the basis for understanding their particular functional specificities.
不同的感觉模态，如温度、疼痛、触觉和肌肉本体感觉，由背根神经节的躯体感觉神经元传导。由于许多这些神经元亚型缺乏分子标记，该系统的研究受到阻碍。为了检测在躯体感觉神经元亚群中表达的基因，使用基因表达序列分析（SAGE）方法对野生型和TrkA突变型新生背根神经节（DRG）进行了基因谱分析。热痛觉感受器占DRG中神经元的比例高达80%。在TrkA突变型DRG中，由于缺乏通过其受体TrkA的神经生长因子存活信号，感觉神经元的伤害感受器亚类缺失。因此，比较野生型和TrkA突变体可以分别鉴定在伤害感受器或机械本体感受器亚类中优先表达的转录本。
我们的比较揭示了两种组织之间有240个基因差异表达（P < 0.01）。其中一些基因，降钙素基因相关肽（CGRP）、钠通道蛋白10a（Scn10a）是感觉神经元亚型的已知标记。通过定量逆转录聚合酶链反应（RT-PCR）以及与TrkA、-B、-C、c-ret、小白蛋白和异凝集素B4（DRG神经元亚型的已知标记）进行双重标记，进一步分析了几个亚群的潜在标记，即对接蛋白4（Dok4）、富含半胱氨酸的分泌蛋白2（Crip2）和谷氨酸受体离子型红藻氨酸1/谷氨酸受体5（Grik1/GluR5）。Grik1/GluR5的表达仅限于异凝集素B4+伤害感受群体，而Dok4和Crip2具有更广泛的表达谱。然而，Crip2的表达被排除在本体感受器亚群之外。
我们已经鉴定并表征了发育中的DRG中三个基因的详细表达模式，并将它们置于由分子标记定义的已知主要神经元亚型的背景中。对该组织中差异表达基因的进一步分析有望扩展我们对不同细胞类型分子多样性的认识，并为理解它们特定的功能特异性奠定基础。
