ROD AND CONE SIGNALING PATHWAYS IN MAMMALIAN RETINA

描述（由申请人提供）：这个新研究项目的总体目标是了解哺乳动物视网膜中杆和锥信号通路的详细突触机制。解剖学研究表明，哺乳动物视网膜中的杆状通道和锥状通道遵循一套特定的电路规则：杆状通道仅在杆状去极化双极细胞（DBCRS）上产生突触，而DBCRS不直接在神经节细胞（GCs）上产生输出突触，而是间接通过AII无突细胞（aiiac）产生输出突触。aiiac通过“搭载”锥形去极化和超极化双极细胞（DBCCS和HBCCS）向ON和OFF GCs发送棒介导的信号，这两种细胞分别与ON和OFF GCs发生突触。在本研究计划中，我们计划以小鼠视网膜为模型系统系统地研究这些哺乳动物特异性突触回路。除了使用全细胞电压钳（染料填充）、解剖学和药理学技术外，我们还将利用四种途径特异性突变小鼠来阐明哺乳动物视杆和视锥细胞信号是如何传递到bc、ac和gc的，并确定哺乳动物特异性电路规则是否完全有效，因为最近的证据和我们的初步结果表明，严格的视杆/视锥细胞输入规则可能并不适用于所有哺乳动物视网膜神经元。我们将对“小鼠DBCRS亚群接受来自锥体的直接突触输入，小鼠DBCCS和HBCCS亚群接受来自杆状细胞的直接突触输入，杆状细胞和锥体介导的信号在发送给gc之前被aiiac进一步混合，并且ac介导的bc和gc的抑制性突触输入携带混合的杆状/锥体信号”的整体假设进行验证。该应用程序有3个特定目标，重点研究杆状体和锥状体对光诱发阳离子和氯离子电流的贡献(？i和？Ic1，分别代表谷氨酸能和gaba能/甘氨酸能突触输入):(1)七种双极细胞（HBCMC/RS、HBCMCS、HBCSCS、DBCC2/MCS、DBCC1/MC/RS、DBCR2S、DBCR1S）；(2)所有的腺分泌细胞；(3)暗适应小鼠视网膜中的三种α神经节细胞（ON、sOFF和tof1gcs）。获得的结果将增加我们对平行通道（如杆/锥信号通路）如何在眼睛和大脑中处理、分离和整合信息的理解。由于许多视觉障碍与视杆和视锥细胞信号通路异常有关，本研究项目将有助于确定与这些眼病发病机制有关的细胞和突触位点。

DESCRIPTION (provided by applicant): The overall objective of this new research project is to understand detailed synaptic mechanisms underlying rod and cone signaling pathways in the mammalian retina. Anatomical studies have suggested that rod and cone channels in the mammalian retina follow a specific set of circuitry rules: rods make synapses only on rod depolarizing bipolar cells (DBCRS), and DBCRS do not make output synapses directly on ganglion cells (GCs), but indirectly through AII amacrine cells (AIIACs). AIIACs send rod-mediated signals to ON and OFF GCs by "piggybacking" on the cone depolarizing and hyperpolarizing bipolar cells (DBCCS and HBCCS), which synapse on ON and OFF GCs, respectively. In this research proposal, we plan to systematically investigate these mammalian-specific synaptic circuits by using the mouse retina as a model system. In addition to using whole-cell voltage clamp (with dye-filling), anatomical and pharmacological techniques, we will take advantage of four strains of pathway-specific mutant mice to elucidate how mammalian rod and cone signals are transmitted to BCs, ACs and GCs, and to determine whether the mammalian-specific circuitry rules are totally valid, as recent evidence and our preliminary results suggest that the strict rod/cone input rules may not hold for all mammalian retinal neurons. We will test the overall hypothesis that "subpopulations of mouse DBCRS receive direct synaptic inputs from cones and subpopulations of mouse DBCCS and HBCCS receive direct synaptic inputs from rods, the rod- and cone-mediated signals are further mixed by AIIACs before sending to GCs, and the AC-mediated inhibitory synaptic inputs to BCs and GCs carry mixed rod/cone signals". This application has 3 specific aims focused on studying rod and cone contributions to light-evoked cation and chloride currents (?Ic and ?Ic1, representing glutamatergic and GABAergic/glycinergic synaptic inputs, respectively) in: (1) seven types of bipolar cells (HBCMC/RS, HBCMCS, HBCSCS, DBCC2/MCS, DBCC1/MC/RS, DBCR2S, DBCR1S); (2) AII amacrine cells; and (3) three types of alpha ganglion cells (ON, sOFF and tOFF 1GCs) in the dark-adapted mouse retina. Results obtained will increase our understanding of how parallel channels, such as the rod/cone signaling pathways, process, segregate and integrate information in the eye and in the brain. Since many visual disorders are associated with abnormalities in the rod and cone signaling pathways, this research project will help to identify cellular and synaptic sites responsible for the pathogenesis of these eye diseases. PUBLIC HEALTH RELEVANCE: The eye is the "window" of the brain and human eyes can register an enormous range of light intensities (from objects under starlit sky to snow under bright sun light) by dividing the labor into two parts: rod photoreceptors encode dim images and cone photoreceptors encode bright and color images. Understanding how rod and cone signals are processed by retinal synaptic pathways is a fundamental and essential step for unraveling mechanisms of visual perception and brain operation. Certain forms of macular degeneration, retinitis pigmentosa, congenital stationary night blindness and glaucoma are associated with dysfunction of the rod and cone signaling pathways, and thus results obtained from this project will provide crucial information on how specific defects in the rod and cone synaptic pathways mediate these eye disorders.