Gene therapy to support cone metabolism in retinitis pigmentosa

描述(申请人提供)：失明通常是由直接影响光感受器的遗传损伤引起的。在人类中有200种致盲基因(retnet：www.sph.uth.tmc.edu/retnet)。通过转导一种特定于该疾病的基因来解决每一种遗传缺陷将是一项庞大而昂贵的任务。作为另一种选择，基因疗法可以用来解决多种遗传性失明常见的问题。其中一种方法是保留视网膜色素变性(RP)的视锥功能。患有RP的人最初夜视能力较差，因为视杆功能障碍。然后杆丢失，紧随其后的是锥体功能的丧失，然后是锥体本身。由于球果在大多数情况下不表达疾病基因，因此肯定存在导致球果死亡的非自主原因。如果这一病因能够被识别并与之抗争，就可以开发出一种更通用的治疗形式。使用4个RP小鼠模型和无偏倚微阵列方法，我们发现许多参与代谢调节的基因在锥体死亡开始时发生了改变。我们进一步证明，代谢的关键调节因子mTOR在RP锥体中不被磷酸化。这是目前已知的RP中最早的锥体应力征象。随着疾病的发展，我们发现锥体进行伴侣介导的自噬。在RP小鼠体内注射胰岛素，可导致mTOR活性增强，提高视锥细胞存活率。我们已经提出了一个模型，在这个模型中，锥体功能失调，然后由于代谢失调而死亡。由于视杆细胞是ONL中的主要细胞类型，视锥细胞在视杆细胞死亡后经历了极大的环境变化。视锥操作系统崩溃，它们失去了与RPE的密切联系，它们暴露在高氧环境中。它们表现出更大的核酸、蛋白质和脂肪的氧化。抵抗氧化可能会导致球果需要更多的NADPH，NADPH是由葡萄糖通过磷酸戊糖途径(PPP)产生的。它也是由两种胞浆酶，苹果酸酶和异柠檬酸脱氢酶产生的。如果葡萄糖被运送到PPP，糖酵解途径将减慢，这可能会导致几种代谢结果，包括减少锥体的表面积，以及减少光转导和潜在的ATP水平。我们希望开发AAV介导的基因治疗来对抗RP视锥细胞中的代谢应激。由于视锥细胞介导的视力对人类最重要，因此视锥细胞功能的保存对RP患者的生活质量至关重要。如果这种疗法能够被开发出来，那么这些疗法也有可能推广到其他视锥细胞受损的疾病，比如老年性黄斑变性(AMD)。

DESCRIPTION (provided by applicant): Blindness is often caused by genetic lesions that directly affect photoreceptors. There are >200 disease genes in humans that lead to blindness (retnet:www.sph.uth.tmc.edu/Retnet). Addressing each genetic deficit by transduction of a gene specific to that disease would be a large and expensive undertaking. As an alternative, gene therapy can be used to attack a problem common to multiple genetic forms of blindness. One such approach is to preserve cone function in retinitis pigmentosa (RP). People with RP initially have poor night vision, as rods are dysfunctional. Rods are then lost, which is followed by loss of cone function, and then cones themselves. As cones do not express the disease gene in most cases, there must be a non-autonomous cause of cone death. If this cause can be identified, and combated, a more generic form of therapy can be developed. Using 4 mouse models of RP, and an unbiased microarray approach, we discovered that many genes involved in the regulation of metabolism were altered at the onset of cone death. We further showed that mTOR, a key regulator of metabolism, was not phosphorylated in RP cones. This is now the earliest sign of cone stress in RP that is known. As the disease progressed, we discovered that cones carried out chaperone- mediated autophagy. Injection of insulin into RP mice, which can lead to increased activity of mTOR, increased survival of cones. We have suggested a model wherein cones are dysfunctional and then die due to dysregulated metabolism. As rods are the major cell type in the ONL, cones experience a greatly altered environment following rod death. The cone OS collapse, they lose their intimate association with the RPE, and they are exposed to a hyperoxic environment. They show greater oxidation of their nucleic acids, proteins, and lipids. Fighting oxidation may cause cones to require more NADPH, which is generated from glucose via the pentose phosphate pathway (PPP). It is also produced by two cytosolic enzymes, malic enzyme and isocitrate dehydrogenase. If glucose is shuttled to the PPP, the glycolytic pathway would slow, which could lead to several metabolic outcomes, including reducing the surface area of cones, as well as reducing phototransduction and potentially the ATP levels. We wish to develop AAV-mediated gene therapy to combat metabolic stress in the cones in RP. As cone-mediated vision is of greatest importance to humans, preservation of cone function is critical to the quality of life among RP patients. If such therapies can be developed, it is also possible that these therapies can be extended to other diseases where cones are compromised, such as age-related macular degeneration (AMD).