The Transcriptomic and Biophysical Basis of Mechanosensory Submodality: A Drosophila Model Organ Study

机械感觉器官将刺激的机械能直接耦合到机械感觉细胞膜上离子通道的开放状态。这一过程被称为机械转导，是所有机械感觉的核心。从概念上讲，很明显，这种耦合的具体性质将区分和定义各种机械感觉子通道(如声音、触摸、平衡、风、疼痛、重力或本体感觉)。但这个概念在其清晰度上具有误导性。它掩盖了这样一个事实，即尚不清楚这种耦合在蜘蛛腿上的本体感觉和触觉毛发、前庭毛细胞或脊椎动物耳蜗中的听觉毛细胞之间应该有什么不同。给近视增加了黑暗，对于上面给出的所有例子，实际换能器通道的分子身份仍然未知。但是，即使我们确实知道所有各自的要求，我们仍然不知道这些是如何在分子上实现的，以实现亚通道特异性的机械转导。果蝇约翰斯顿器官(JO)是最具适应性的机械感觉模型器官之一，位于第二触角节段，含有与风/重力和声音亚型相关的离散的机械感觉神经元群体。然而，所有神经元都附着在相同的接收器结构上，即第三个触角部分。因此，必须在接收器的下游在相应的细胞和分子组件的水平上实现大部分特定于次模态的适应。我们打算对JO中的通道特异性机械转导进行全面的分子和功能剖析。我们首先将描述不同类型的神经元和非神经元细胞的特定mRNA转录本(即产生的一整套mRNAs)。这种特定细胞类型的转录分析将揭示JO的分子(和细胞)劳动分工，并有助于确定单个基因在亚群特定的机械转导和机械感觉行为中的不同作用。我们的行为分析将使用我们专门为这个项目设计的新工具。结合分子和生物物理分析(激光测振法、细胞外和细胞内记录)和预测性计算工具，该项目将特别强调识别高阶调控基因的特定形态差异，如特定的转录因子。识别特定形式的转录因子有望识别不同的感觉转导模块，这些模块作为不同模式的机械感觉细胞中的功能单元。有强有力的证据表明，不同物种的感觉器官，如苍蝇的耳朵和人类的耳朵，在功能和分子上具有许多相似之处。同样，同一物种内的不同感官，如苍蝇的耳朵和眼睛，也显示出惊人的分子和机械重叠。了解潜在的转录途径在整个动物界中是如何被保守的，在进化过程中如何重组，以创建各种模式和亚模式的感觉系统，对于更好地理解无数的人类疾病综合征，如Usher综合征IIA+IIIA或Bardet-Biedl综合征，将是非常有价值的，它们同时影响多个感觉系统。最终，这项对感觉通道的分子和机制基础的研究将引领我们走向新的治疗途径。

Mechanosensory organs directly couple the mechanical energy of a stimulus to the open-state of an ion channel in the membrane of a mechanosensory cell. This process, known as mechanotransduction, lies at the heart of all mechanosensation. Conceptually, it is clear that the specific nature of this coupling will distinguish, and define, the various mechanosensory submodalities (such as sound, touch, balance, wind, pain, gravity or proprioception). But the concept is misleading in its clarity. It hides the fact that it is unclear how that coupling should differ between, say, a proprioceptive and tactile hair on a spider leg, a vestibular hair cell, or an auditory hair cell in the vertebrate cochlea. Adding darkness to short sight, the molecular identities of the actual transducer channels are still unknown for all of the above given examples. But even if we did know all the respective requirements, we would still not know how these are implemented molecularly for submodality-specific mechanotransduction, to occur. One of the most amenable mechanosensory model organs, the Drosophila Johnston Organ (JO), sits in the 2nd antennal segment and harbours discrete populations of mechanosensory neurons which have been linked to the submodalities of wind/gravity and sound. However, all neurons attach to the same receiver structure, the third antennal segment. Large parts of the submodality-specific adaptations thus have to be implemented downstream of the receiver on the level of the respective cellular and molecular components. We intend to carry out a comprehensive molecular, and functional, dissection of modality-specific mechanotransduction in JO.We will first profile the specific mRNA transcriptomes, (i.e. the complete sets of produced mRNAs) for different types of neuronal and non-neuronal cells. Such cell-type-specific transcriptomic analyses will unveil the molecular (and cellular) divisions of labour in JO and help identify the distinct roles of individual genes for subset-specific mechanotransduction and mechanosensory behaviours. Our behavioural analyses will use novel tools that we have specifically devised for this project. Combining molecular and biophysical analyses (laser vibrometry, extracellular and intracellular recordings) with predictive computational tools, this project will put particular emphasis on the identification of modality-specific differences in higher order regulatory genes, such as specific transcription factors. The identification of modality-specific transcription factors is expected to enable the identification of distinct modules of sensory transduction, which act as functional units within mechanosensory cells of different modalities.There is robust evidence that the sensory organs of different species, e.g. the ears of flies and the ears of humans, share multiple functional and molecular similarities. Likewise, different sensory organs within the same species, e.g. the ears and the eyes of flies display striking molecular and mechanistic overlap. Understanding how the underlying transcriptional pathways, which can be expected to be conserved across the animal kingdom, are being recombined during the process of evolution to create sensory systems of various modalities and submodalities will be of great value for better understanding of the myriad of human disease syndromes such as Usher syndrome Type IIA + IIIA or Bardet-Biedl syndrome, which simultaneously affect multiple sensory systems. Eventually, this research into the molecular and mechanistic fundaments of sensory modality will lead the way towards new therapeutic avenues.