Pathfinding of Ganglion Cell Axons and Ocular Albinism

神经节细胞轴突与眼白化病的探路

• 批准号: 6525356
• 负责人: DEBORA B FARBER
• 金额: $ 15.25万
• 依托单位: UNIVERSITY OF CALIFORNIA LOS ANGELES
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-08-01 至 2003-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6525356
• 关键词: albinism; axon; cell differentiation; diphtheria toxin; ganglion cell; gene mutation; genetically modified animals; intercellular connection; laboratory mouse; melanins; monophenol monooxygenase; neuronal guidance; optic tract; retinal pigment epithelium; synaptogenesis; vision disorders

DESCRIPTION: (Applicant's Abstract) Individuals with ocular albinism (OA) lack stereoscopic vision due to a reduction of the ipsilateral component of the optic tract and have deficient melanin levels in the retinal pigment epithelium (RPE). The gene that causes the X-linked form of this disease, 0A1, has been identified and characterized. It encodes a G-protein coupled-receptor of unknown function that is localized on the membrane of melanosomes. Melanogenesis occurs in these organelles and tyrosinase is the key enzyme involved in this process. Melanosornes are present in the melanocytes, of the skin and in the RPE. The goal of this proposal is to investigate the molecular mechanisms of axon guidance that lead to the formation of abnormal synaptic connections in the brain of individuals affected with OA. The mouse albino mutant, that carries a point mutation in tyrosinase leading to decreased numbers of uncrossed retinal axons, offers a genetic model to address why the deficiency in melanin results in the abnormality at the optic chiasm seen in OA. We propose to use a genetic approach to identify the cues provided by tyrosinase, RPE cells and Oal that direct retinal axon divergence at the chiasm, and the mechanisms underlying specification of retinal ganglion cells to respond to these cues. Initially, we will genetically engineer mice having Cre-recombinase. These animals will allow us to control the timing of expression of specific genes. The Cre-mice will be crossed with transgenic albino mice expressing tyrosinase or diphteria toxin, and with transgenic mice carrying a conditional allele of 0al. The inducible restoration of melanine by tyrosinase will allow us to determine whether pigmentation has a role in axonal pathfinding. The inducible expression of diphteria toxin to ablate the RPE will indicate whether these cells influence both the differentiation of ganglion cells and their axonal pathfinding. The introduction of an "on/off" switch to flip Oal coding sequences will allow us to determine whether the stages of axonal crossing can be reversed by the re-expression of the wild type gene. The information obtained with these studies will. increase our understanding of the pathology of ocular albinism and will help us . to unravel molecular mechanisms of pathfinding in the optic chiasm, a "choice point" where growth cones navigate to the same or opposite side of the brain. Finding how pigmentation defects in the RPE cause abnormalities in axonal guidance and in retinal development may provide insights applicable to future therapy.

描述：（申请人摘要）眼部白化病 (OA) 患者缺乏 由于同侧分量减少而产生立体视觉 视束，视网膜色素上皮中黑色素水平不足 （RPE）。导致这种疾病的 X 连锁形式的基因 0A1 已被 识别和表征。它编码 ​​G 蛋白偶联受体 位于黑素体膜上的未知功能。 黑色素生成发生在这些细胞器中，酪氨酸酶是关键酶 参与这个过程。黑素细胞存在于黑素细胞中， 皮肤和 RPE 中。 该提案的目标是研究轴突的分子机制 导致异常突触连接形成的指导 OA 患者的大脑。小鼠白化突变体，携带 酪氨酸酶点突变导致未交叉视网膜数量减少 轴突，提供了一个遗传模型来解决黑色素缺乏的原因 OA 中出现的视交叉异常。我们建议使用基因 方法来识别酪氨酸酶、RPE 细胞和​​ Oal 提供的线索 交叉处的直接视网膜轴突分歧及其潜在机制 视网膜神经节细胞对这些线索做出反应的规范。最初，我们 将对具有 Cre 重组酶的小鼠进行基因工程改造。这些动物将允许 我们可以控制特定基因的表达时间。克里米老鼠将是 与表达酪氨酸酶或白喉毒素的转基因白化小鼠杂交， 以及携带条件等位基因 0al 的转基因小鼠。诱导型 通过酪氨酸酶恢复黑色素将使我们能够确定是否 色素沉着在轴突寻路中发挥作用。的诱导表达 白喉毒素消融 RPE 将表明这些细胞是否影响 神经节细胞的分化及其轴突寻路。这 引入“开/关”开关来翻转 Oal 编码序列将使我们能够 以确定轴突交叉的阶段是否可以通过 野生型基因的重新表达。通过这些获得的信息 研究会。增加我们对眼白化病病理学的了解 并将帮助我们。揭示光学寻路的分子机制 交叉，生长锥导航到相同或相反的“选择点” 大脑的一侧。找出 RPE 色素沉着缺陷的原因 轴突导向和视网膜发育异常可能会导致 适用于未来治疗的见解。