Delaying Cone Death in Retinitis Pigmentosa

描述（由申请人提供）：人和小鼠的视杆和视锥光感受器之间的神经元间关系使得视杆死亡总是导致视锥死亡;然而，视锥的损失对视杆没有影响。这种现象在遗传性视网膜变性疾病视网膜色素变性中起重要作用，因为鉴定的大多数致病等位基因编码仅在视杆细胞中表达的基因。由于视锥细胞的死亡总是伴随着视杆细胞的死亡，而视锥细胞对人类的视觉是必不可少的，因此正是它们的丧失导致了失明。我们最近提出视锥细胞死亡是由营养摄取减少引起的细胞自主事件，并表明胰岛素/AKT/mTOR通路在视锥细胞死亡期间起着至关重要的作用。全身给予胰岛素对视网膜色素变性小鼠视网膜视锥细胞存活的影响。在这里，我们建议研究如何胰岛素受体存活。为此，我们现在已经通过删除磷酸酶和张力蛋白同源物（PTEN）以及分别通过删除结节性硬化症复合蛋白1（TSC 1）在视锥细胞中遗传激活了该途径。与胰岛素给药相比，PTEN或TSC 1的缺失进一步改善视锥细胞存活，表明PTEN和TSC 1下游基因具有延长视网膜色素变性视力的治疗潜力。由于PTEN或TSC 1的缺失激活雷帕霉素（mTOR）和AKT的激酶机制靶点，因此预测促进视锥细胞存活的基因在这两种激酶的下游。由于mTOR和AKT有数百个靶点，我们将首先描述这两种激酶对视锥细胞存活的贡献， PTEN或TSC 1的缺失。这些实验将在目标1和2中进行。随后，在目标3中，我们将使用微阵列来鉴定促进视锥细胞存活的mTOR和/或AKT的靶基因。最后，我们将使用重组腺相关病毒介导的基因转移来测试这些基因在体内的功效。这些目标的实现将有助于设计合理的治疗方法，以扩大人类视网膜色素变性的视力。

DESCRIPTION (provided by applicant): The inter-neuronal relationship between rod and cone photoreceptors in human and mouse is such that rod death always leads to cone death however; loss of cones has no effect on rods. This phenomenon plays an important role in the inherited retinal degenerative disease retinitis pigmentosa, as most disease-causing alleles identified encode for genes that are exclusively expressed in rods. Since cone death always follows rod death, and cones are essential for human vision, it is their loss that leads to blindness. We have recently proposed that cone death is a cell autonomous event caused by reduced nutrient uptake and showed that the insulin/AKT/mTOR pathway plays a crucial role during the periods of cone death. Systemic administration of insulin to retinitis pigmentosa mice prolongs cone survival. Here we propose to study how insulin prolongs cone survival. To that end we have now genetically activated the pathway in cones, by deletion of the phosphatase and tensin homolog (PTEN) and separately, by deletion of the tuberous sclerosis complex protein 1 (TSC1). Loss of PTEN or TSC1 further improves cone survival when compared to insulin administration, suggesting that genes downstream of PTEN and TSC1 have therapeutic potential to prolong vision in retinitis pigmentosa. Since loss of PTEN or TSC1 activates the kinases mechanistic target of rapamycin (mTOR) and AKT, genes that promote cone survival are predicted to be downstream of these two kinases. Because mTOR and AKT have hundreds of targets we will first delineate the contribution of these two kinases to cone survival seen upon loss of PTEN or TSC1. These experiments will be carried out in aims 1 & 2. Subsequently, in aim 3 we will use microarrays to identify target genes of mTOR and/or AKT that promote cone survival. Finally, we will tests the efficacy of such genes in vivo using recombinant Adeno-associated virus mediated gene transfer. Accomplishment of these aims will help design rational therapeutic approaches to extend vision in humans with retinitis pigmentosa.