Working Mechanisms of Ribbon Synapses in Cochlea

耳蜗内毛细胞（Inner hair cells，IHC）与Ⅰ型初级听觉神经元（spiral ganglion neurons，SGNs）形成突触，为听觉脑提供主要的信息通路。这种突触的特点是其突触前呈带状结构，因此称为带状突触。众所周知，突触前区室中的特定结构和分子组成是对声音产生快速且持久反应的原因。然而，很少有人知道耳蜗中的带状突触是如何发挥这种作用的。* 带状突触主要见于视网膜和耳蜗，但耳蜗带状突触的研究远落后于视网膜。具体地说，许多蛋白质是关键的突触传递在传统的突触是失踪的IHC带状突触。这些蛋白质在耳蜗带状突触中的功能特异性仍有待研究。* 将实现三个目标：（1）探索两种带状蛋白的功能作用：otoferlin和piccolino在IHC突触传递中的作用;（2）验证IHC中是否存在突触前带的功能性拆解和重组，以及（3）通过验证噪声后修复的带状突触的结构和分子变化，探索带状突触信号编码的分子底物损害。* Otoferlin和piccolino将分别下调。本研究将探讨下调对听觉神经纤维（ANFs）形态学的影响，以及ANFs的编码功能，以验证其在突触传递中的作用和工作机制。* 为实现第二个目的，将采用各种形态学方法，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敲除将用于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带状突触周围噪声诱导的损伤和修复方面的进展。在这一系列的研究中，我们证明了听觉神经的编码缺陷与初始损伤后的突触修复有关。这表明修复的突触可能在其蛋白质/结构组成上不同。我们将观察这种差异所造成的噪音损害和修复的重点是带状一侧的突触。将使用各种方法来进行此类变化以及结构与功能之间的相关性。*本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，以便更好地处理损伤和修复。

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.