Molecular Basis of Photoreceptor Wiring

项目摘要 哺乳动物的视杆细胞和视锥细胞对于视觉是不可缺少的。它们将光转化为电 反应，然后通过视网膜电路传播到大脑。电力传输 由光感受器产生的信号需要它们与下游中间神经元的突触连接， 双极细胞已知光感受器和双极细胞之间突触通讯的缺陷， 导致人类先天性静止性失明，这是一种以光敏感性差为特征的疾病， 与许多其他眼部疾病频繁共病。我们的长期目标是阐明分子和 光感受器建立突触并传递信号的细胞机制， 更好地了解盲态条件并制定治疗策略。 两种类型的光感受器，杆和锥，与不同类型的细胞形成不同的连接。 双极细胞这种突触特异性分离视觉输入，并在建立视觉输入中发挥重要作用。 我们视觉的基本属性，包括广泛的动态范围的光敏感度和对比度 歧视然而，负责选择性连接之间的分子机制， 光感受器及其下游双极神经元是未知的。我们已经发现了一种新的细胞粘附- 就像ELFN 1分子，它特异性地存在于光感受器突触上。我们发现ELFN 1形成了一个 与双极细胞中的主要神经递质受体mGluR 6的跨突触相互作用。破坏 ELFN 1导致视杆突触的选择性丧失。我们假设ELFN 1-mGluR 6相互作用是 在介导视杆光感受器的选择性突触连接和引导光传播中的作用 信号穿过视网膜电路。 这一假设将通过追求三个互补的具体目标来检验，这些目标将：（i）使用 基因敲除小鼠模型和基因拯救实验，以确定ELFN 1功能的细胞机制 在视杆细胞和ON-RBC之间突触的形成中，（ii）研究ELFN 1在 引导传播光信号穿过视网膜电路，以及（iii）检查分子机制， ELFN 1使其突触发生作用。为实现这些目标而提出的战略将需要一项协同增效的 生物化学、分子生物学、电生理学和生理学方法的组合，每个 利用一系列强大的试剂和动物模型。

PROJECT SUMMARY Mammalian rod and cone photoreceptors are indispensible for vision. They convert light into electrical response, which is then propagated across the retina circuit and into the brain. Transmission of the electrical signal generated by the photoreceptors requires their synaptic connectivity with the downstream interneurons, the bipolar cells. Deficits in synaptic communication between photoreceptors and bipolar cells are known to cause congenital stationary blindness in humans, a condition characterized by poor light sensitivity and frequent co-morbidity with many other ocular conditions. Our long-term goal is to elucidate molecular and cellular mechanisms by which photoreceptors establish synapses and transmit their signals with the hope to better understand blinding conditions and devising strategies for their treatment. Two types of the photoreceptors, rods and cones, form distinct connections with different types of the bipolar cells. This synaptic specificity segregates visual inputs and plays an essential role in setting up the fundamental properties of our vision, including a wide dynamic range of light sensitivity and contrast discrimination. However, the molecular mechanisms responsible for selective connectivity between photoreceptors and their downstream bipolar neurons are unknown. We have identified a new cell adhesion- like molecule ELFN1 that specifically present at the photoreceptors synapses. We found that ELFN1 forms a trans-synaptic interaction with the principal neurotransmitter receptor in bipolar cells, mGluR6. Disruption of ELFN1 results in selective loss of rod synapses. We hypothesize that ELFN1-mGluR6 interaction play key roles in mediating selective synaptic connectivity of rod photoreceptors and direct the propagation of light signal across retina circuit. This hypothesis will be tested by pursuing three complementary Specific Aims that will (i) use knockout mouse models, and genetic rescue experiments to determine cellular mechanisms of ELFN1 function in the formation of synapse between rod photoreceptors and ON-RBC, (ii) investigate the role of ELFN1 in directing the propagation light signal across retina circuitry, and (iii) examine molecular mechanisms by which ELFN1 enables its synaptogenic effects. The strategy proposed to address these aims will entail a synergistic combination of biochemical, molecular biological, electrophysiological, and physiological approaches, each exploiting the existence of a powerful array of reagents and animal models.