Visualizing cold spots: TRPM8-expressing sensory neurons and their projections
Visualizing cold spots: TRPM8-expressing sensory neurons and their projections
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DOI：
10.1523/jneurosci.3976-07.2008
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发表时间：
2008-01-16
影响因子：
5.3
通讯作者：
Patapoutian, Ardem
中科院分区：
文献类型：
--
作者：
Dhaka, Ajay;Earley, Taryn J.;Patapoutian, Ardem
背根神经节（DRG）神经元可以感知环境刺激，如温度和压力。DRG神经元是异质的，但主要缺乏识别独特功能亚群的分子标记。ThermoTRP是离子通道的瞬时受体电位家族的成员，并通过温度变化进行门控。TRPM8被冷却激活，TRPM8缺陷小鼠在冷的温度感觉上有严重的缺陷。表达TRPM 8的纤维的解剖和功能特性尚未得到全面研究。我们使用小鼠工程表达法尼基化增强型绿色荧光蛋白（EGFPf）从TRPM 8基因座（TRPM 8（EGFPf））来探讨这个问题。几乎所有来自半合子小鼠（TRPM8（EGFPf/+））的EGFPf阳性培养的DRG神经元对冷和薄荷醇有反应。相比之下，来自纯合子小鼠的EGFPf阳性DRG（TRPM8（EGFPf/EGFPf））具有显著降低的冷反应并且没有薄荷醇反应。在体内，EGFPf阳性神经元标志着DRG神经元的独特群体，其中大多数不共表达伤害性标记物。在炎症条件下，表达EGFPf的DRG神经元的比例没有改变，尽管观察到TRPV1共表达神经元的增加。TRPM8（EGFPf）神经元投射到脊髓的浅层I，当与肽能投射相比时，产生不同的接触。在外周，TRPM8（EGFPf）的预测标志着独特的结束在最表层的表皮，包括布什/簇结束的mysterectomy垫。我们表明，TRPM8的表达功能与冷敏感性在培养的背根神经节，并提供了第一次瞥见的独特的解剖结构的冷纤维在体内。
Environmental stimuli such as temperature and pressure are sensed by dorsal root ganglion (DRG) neurons. DRG neurons are heterogeneous, but molecular markers that identify unique functional subpopulations are mainly lacking. ThermoTRPs are members of the transient receptor potential family of ion channels and are gated by shifts in temperature. TRPM8 is activated by cooling, and TRPM8-deficient mice have severe deficits in cool thermosensation. The anatomical and functional properties of TRPM8-expressing fibers have not been not comprehensively investigated. We use mice engineered to express the farnesylated enhanced green fluorescent protein (EGFPf) from the TRPM8 locus (TRPM8(EGFPf)) to explore this issue. Virtually all EGFPf-positive cultured DRG neurons from hemizygous mice (TRPM8(EGFPf/+)) responded to cold and menthol. In contrast, EGFPf-positive DRGs from homozygous mice (TRPM8(EGFPf/EGFPf)) had drastically reduced cold responses and no menthol responses. In vivo, EGFPf-positive neurons marked a unique population of DRG neurons, a majority of which do not coexpress nociceptive markers. The fraction of DRG neurons expressing EGFPf was not altered under an inflammatory condition, although an increase in TRPV1-coexpressing neurons was observed. TRPM8(EGFPf) neurons project to the superficial layer I of the spinal cord, making distinct contacts when compared with peptidergic projections. At the periphery, TRPM8(EGFPf) projections mark unique endings in the most superficial layers of epidermis, including bush/ cluster endings of the mystacial pads. We show that TRPM8 expression functionally associates with cold sensitivity in cultured DRGs, and provide the first glimpses of the unique anatomical architecture of cold fibers in vivo.