Delaying Cone Death in Retinitis Pigmentosa

描述(申请人提供)：视杆细胞和视锥感受器之间的神经元间关系在人类和小鼠中是这样的，视杆细胞死亡总是导致视锥细胞死亡；视锥细胞的丧失对视杆细胞没有影响。这一现象在遗传性视网膜退行性疾病视网膜色素变性中发挥着重要作用，因为大多数已发现的致病等位基因编码的基因仅在视杆中表达。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。我们最近提出锥体死亡是一种由营养摄取减少引起的细胞自主事件，并表明胰岛素/AKT/mTOR通路在锥体死亡过程中起着至关重要的作用。对视网膜色素变性小鼠全身注射胰岛素可延长视锥细胞存活时间。在这里，我们打算研究胰岛素是如何延长锥体存活的。为此，我们现在已经通过删除磷酸酶和紧张素同源物(PTEN)和分别通过删除结节性硬化症复杂蛋白1(TSC1)来从基因上激活锥体内的这一途径。与胰岛素注射相比，PTEN或TSC1的缺失进一步改善了视锥细胞的存活，表明PTEN和TSC1下游的基因具有延长视网膜色素变性患者视力的治疗潜力。由于PTEN或TSC1的缺失激活了雷帕霉素(MTOR)和AKT的激酶机制靶点，因此促进锥体存活的基因被预测位于这两个激酶的下游。由于mTOR和AKT有数百个靶点，我们将首先描绘这两个激酶对锥体存活的贡献 PTEN或TSC1缺失。这些实验将在目标1和目标2中进行。随后，在目标3中，我们将使用微阵列来识别促进锥体存活的mTOR和/或AKT的靶基因。最后，我们将利用重组腺相关病毒介导的基因转移在体内测试这些基因的效果。这些目标的实现将有助于设计合理的治疗方法来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.