Mechanisms of feedback from retinal horizontal to cone cells

视网膜水平到视锥细胞的反馈机制

• 批准号: 8126524
• 负责人: Tzu-Ming Wang
• 金额: $ 5.3万
• 依托单位: UNIVERSITY OF CALIFORNIA BERKELEY
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-05-17 至 2014-05-16
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8126524
• 关键词: AMPA Receptors; Acidity; Address; Agonist; Attenuated; Calcium; Calcium Channel; Detection; Feedback; Fishes; Fluorescence; Glutamate Receptor; Intervention; Light; Lighting; Mediating; Membrane; Monitor; PHluorin; Pattern; Photoreceptors; Physiological; Play; Prosthesis; Retina; Retinal; Retinal Cone; Role; Scientist; Signal Transduction; Surface; Synapses; Synaptic Cleft; TRPV1 gene; Testing; Transgenic Organisms; Variant; Vision; Visual; Zebrafish; computerized data processing; design; gene therapy; horizontal cell; neurotransmitter release; overexpression; receptive field; response; retinal neuron; voltage

DESCRIPTION (provided by applicant): Photoreceptors not only receive light as an input, they also get feedback signals from horizontal cells (HCs). Negative feedback from HCs is believed to be the fundamental mechanism underlying the center-surround organization of the receptive field of retinal neurons. The mechanism responsible for HC feedback is controversial, but one major hypothesis is that the calcium current at the cone terminal is regulated by the acidity (i.e. pH) of the synaptic cleft. Although the pH hypothesis is currently very popular, it is still unknown if the pH value of the synaptic cleft really changes under physiological conditions, and if this change is significant enough to mediate the feedback. To address these questions, transgenic zebrafish expressing a pH-sensitive GFP variant either on HC or cone surfaces have been created in order to monitor the pH within the synaptic invagination. Patterned illumination will be transmitted onto the retina while membrane fluorescence is monitored. A pH change within the cone synaptic cleft will be reflected by a corresponding change in fluorescence intensity, and the direction and magnitude of the fluorescence drift will be compared to the expected pH change required for mediating feedback responses. Recently, an unexpected positive feedback mechanism from HCs to cones was discovered, which presumably boosts the gain of photoreceptors. This positive feedback is likely initiated by calcium influx into HCs, which subsequently accelerates neurotransmitter release from cones through an unknown mechanism. To examine the importance of HC calcium influx in initiating this feedback, transgenic zebrafish expressing GluR2 in HCs have been created. Because GluR2-containing glutamate receptors are calcium-impermeable, positive feedback is expected to be attenuated. To test if calcium alone is sufficient to elicit positive feedback, transgenic zebrafish expressing TRPV1 channels in HCs will be created. TRPV1 channels are calcium- permeable, therefore, if calcium itself is sufficient to initiate positive feedback, a TRPV1 agonist should trigger the positive feedback as well. This proposal addresses long standing debates in negative feedback and provides clues for understanding the newly discovered positive feedback in visual signal processing. Understanding how feedback signals are given to cone cells will help vision scientists design better interventions, such as gene therapy or prosthetic devices, to aid in restoring vision. PUBLIC HEALTH RELEVANCE: Relevance Understanding how visual signals are processed in the retina will help vision scientists to design better interventions like gene therapy or prosthetic devices for restoring vision.

描述（由申请人提供）：光感受器不仅接收光作为输入，它们还从水平细胞（HC）获得反馈信号。 HC 的负反馈被认为是视网膜神经元感受野中心-环绕组织的基本机制。 HC 反馈的机制存在争议，但一个主要假设是锥体末端的钙电流受突触间隙的酸度（即 pH）调节。尽管pH假说目前非常流行，但目前尚不清楚突触间隙的pH值在生理条件下是否真的发生变化，以及这种变化是否足够显着以介导反馈。为了解决这些问题，我们创建了在 HC 或锥体表面表达 pH 敏感 GFP 变体的转基因斑马鱼，以监测突触内陷内的 pH 值。图案化的照明将传输到视网膜上，同时监测膜荧光。锥体突触间隙内的 pH 变化将通过荧光强度的相应变化反映出来，并且荧光漂移的方向和幅度将与介导反馈响应所需的预期 pH 变化进行比较。最近，发现了从 HC 到视锥细胞的一种意想不到的正反馈机制，这可能会提高感光细胞的增益。这种正反馈可能是由钙流入 HC 引发的，随后通过未知的机制加速神经递质从视锥细胞的释放。为了检查 HC 钙流入在启动这种反馈中的重要性，已经创建了在 HC 中表达 GluR2 的转基因斑马鱼。由于含有 GluR2 的谷氨酸受体是钙不可渗透的，因此正反馈预计会减弱。为了测试单独的钙是否足以引起正反馈，将创建在 HC 中表达 TRPV1 通道的转基因斑马鱼。 TRPV1 通道是钙渗透性的，因此，如果钙本身足以启动正反馈，TRPV1 激动剂也应该触发正反馈。该提案解决了长期以来关于负反馈的争论，并为理解视觉信号处理中新发现的正反馈提供了线索。了解反馈信号如何传递给视锥细胞将有助于视觉科学家设计更好的干预措施，例如基因疗法或假肢装置，以帮助恢复视力。 公共卫生相关性：相关性了解视觉信号在视网膜中的处理方式将有助于视觉科学家设计更好的干预措施，例如用于恢复视力的基因疗法或假肢装置。