Working Mechanisms of Ribbon Synapses in Cochlea

耳蜗区内毛细胞(IHCs)与I型初级听神经元(螺旋神经节神经元，SGN)形成突触，为听性脑提供主要信息通路。这种突触的特征是它们的突触前带状结构，因此被称为带状突触。众所周知，突触前隔区的特定结构和分子组成是导致对声音快速而持久的反应的原因。然而，人们对耳蜗区的带状突触如何扮演这样的角色知之甚少。带状突触主要见于视网膜和耳蜗区，但对带状突触的研究远远落后于视网膜。具体地说，许多在常规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。这些蛋白质在耳蜗带突触中的功能特异性仍有待探索。*将实现三个目标：(1)探讨两种功能区蛋白：Otoferlin和Piccolino在IHC突触传递中的功能作用；(2)验证IHC中是否存在突触前功能区的功能性拆解和重组；(3)通过验证噪声损伤后修复的功能区突触的结构和分子变化，探索功能区突触信号编码的分子底物。**Otoferlin和Piccolino将分别下调。为了验证听神经纤维(ANF)在突触传递中的作用和作用机制，我们将研究ANF下调对其形态和编码功能的影响。为了达到第二个目标，将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，还将使用耳铁碱和Picccolino基因敲除来确定这两种蛋白质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突触损伤和修复方面的进展。在这一系列研究中，我们证明了听神经的编码缺陷与突触损伤后的修复有关。这表明修复后的突触在蛋白质/结构组成上可能有所不同。我们将观察噪声损伤和修复造成的差异，重点放在突触的带侧。将利用各种方法来研究这种变化以及结构和功能之间的关系。*这项研究的长期目标是充分了解带状突触在听觉感觉器官中的工作机制，以便在未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.