Working Mechanisms of Ribbon Synapses in Cochlea

耳蜗突触内的内毛细胞（IHCs）与I型初级听觉神经元（螺旋神经节神经元，sgn）连接，为听觉脑提供主要的信息通路。这种突触的特点是它们的突触前带状结构，因此被称为带状突触。我们知道突触前区特定的结构和分子组成决定了对声音的快速和持久的反应。然而，耳蜗中的带状突触是如何发挥这样的作用的，我们所知甚少。***带状突触主要存在于视网膜和耳蜗，但耳蜗带状突触的研究远远落后于视网膜。具体来说，许多在传统突触中对突触传递至关重要的蛋白质在ihc带状突触中缺失。这些蛋白在耳蜗带状突触中的功能特异性仍有待探索。***将达到三个目的：(1)探索otoferlin和piccolino两种带状蛋白在IHC突触传递中的功能作用；(2)验证IHC中是否存在突触前带状的功能性拆解和重组；(3)通过验证修复后的带状突触在噪声损伤后的结构和分子变化来探索带状突触信号编码的分子底物。***Otoferlin和piccolino分别下调。为了验证其在突触传递中的作用和工作机制，我们将研究这种下调对听觉神经纤维形态学和编码功能的影响。***为实现第二个目的，将采用多种形态学方法结合免疫组织学方法、分子生物学方法对带状突触结构进行动态观察。此外，otoferline和picccolino基因敲除将用于确定这两种蛋白在条带组装中的潜在作用。***第三个目标是基于我最近在噪声引起的损伤和修复带状突触周围的进展。在这方面的研究中，我们证明了听觉神经编码缺陷的发展与初始损伤后的突触修复有关。这表明修复后的突触可能在蛋白质/结构组成上有所不同。我们将以突触带侧为重点，观察噪声损伤和修复引起的差异。各种方法将被用于这种变化和结构与功能之间的关联。***本研究的长期目标是充分了解听觉感觉器官带状突触的工作机制，以便将来更好地管理损伤和修复。

Inner hair cells (IHCs) in the cochlea synapse with type I primary auditory neurons (spiral ganglion neurons, SGNs), providing the main information pathway to auditory brain. This synapse are characterized by their pre-synaptic ribbon structure, and therefore called ribbon synapses. It is known that the specific structure and molecular composition in the presynaptic compartment are responsible for the quick and long-lasting responses to sound. However, little detail is known how the ribbon synapses in cochlea play such roles. ***Ribbon synapses are mainly seen in both retina and cochlea, but the research of cochlear ribbon synapse is much behind of that in retina. Specifically, many proteins that are critical for synaptic transmission in conventional synapse are missing in IHCs ribbon synapse. Functional specificities remains to be explored for those proteins in cochlear ribbon synapses. ***Three aims will be achieved: (1) to explore the functional roles of two ribbon proteins: otoferlin and piccolino in the IHC synaptic transmission, (2) to verify whether there is a functional dissembling and reassembling of presynaptic ribbons in IHCs, and (3) to explore the molecular substrate for signal coding at ribbon synapses by verifying the structure and molecular changes in the repaired ribbon synapses after noise damage.***Otoferlin and piccolino will be down-regulated respectively. The impact of the down-regulation on morphology, and the coding function of auditory nerve fibers (ANFs) will be investigated in order to verify their roles and working mechanisms in synaptic transmission. ***To achieve the second aim, dynamic observation of ribbon synaptic structure will be performed using various morphological methods in combination with immunohistological method, molecular biology methods. Moreover, otoferline and picccolino knockout will be used to identify the potential roles of those two proteins in the assembly of ribbons. ***The third aim is based upon my recent progress on noise induced damage and repair around ribbon synapses. In this line of research, we demonstrated that coding deficits of auditory nerve was developed in association with synaptic repair after initial damage. This suggested a possibility that the repaired synapses may be different in their protein/structure composition. We will observe such difference caused by noise damage and repair with focus on ribbon side of the synapse. Various methods will be utilized for such changes and for the correlation between structure and function.***The long term goal of the research is to fully understand the working mechanism of ribbon synapses in the auditory sensorial organ in order to have better management of damage and repair in future.