HDAC4-mediated Photoreceptor Protection in Retinal Degeneration

描述(申请人提供)：在美国，导致失明的主要原因是视网膜变性，通常涉及感光细胞(视杆和视锥)的死亡。视网膜色素变性是一组主要的遗传性视网膜退行性疾病，通常由视杆细胞特异基因突变引起。这些遗传缺陷导致视杆细胞死亡，随后是正常视锥细胞的逐渐退化。视锥细胞死亡是导致RP患者进行性视力丧失的原因。在美国，有100,000多人感染RP，目前尚无治疗或预防措施。我们的长期目标是了解RP患者光感受器退化的机制，并开发挽救光感受器和恢复RP患者视功能的治疗方法。挽救视杆细胞的一个主要挑战是RP的异质性，因为已经在视杆特异基因中发现了许多突变；因此，每个突变都可能需要一种独特的治疗方法。相比之下，保留视锥可能为RP提供了一种更普遍的保存视力的方法。我们先前的研究表明，HDAC4在促进RP小鼠模型中的视杆存活方面具有新的作用。我们将通过以下目标扩大我们的研究：目的1)我们将研究HDAC4保护视网膜变性小鼠光感受器的分子和细胞机制。利用cre-loxP系统限制HDAC4在特定细胞类型中的表达，我们将测试HDAC4在其他细胞类型中是否通过细胞自主机制与HDAC4的S效应在光感受器中发挥促生存作用。我们将进一步测试HDAC4脱乙酰基酶结构域是否为其在光感受器保护中所必需的。目的2)我们将测试HDAC4在快速型和慢速型视网膜变性模型中是否保存了感光细胞。利用AAV(腺相关病毒)介导的Rd1小鼠(一种快速视网膜变性模型)的基因转移，我们将测试HDAC4是否直接促进视锥细胞存活。我们将测试保存下来的锥体结构和锥体光传导中的关键组件。利用AAV介导的基因转移到VPP和RD10小鼠(较慢的视网膜变性模型)，我们将研究1)光感受器保护是否需要HDAC4的发育表达；2)HDAC4是否可以用作更一般的光感受器保护存活因子。目的3)我们将研究在视网膜变性过程中失活的主要生存信号通路，以及在HDAC4保存的视锥细胞中重新激活的主要生存信号通路。我们将进一步测试HDAC4保存的视锥细胞是否能恢复视觉功能：1)电生理学测试视网膜和视皮层神经回路的完整性；2)行为测试以确定挽救的视网膜功能是否能够指导复杂的行为。总之，我们提出的研究将阐明HDAC4促进光感受器存活的分子和细胞机制和途径，光感受器是视网膜遗传性疾病的主要靶点。我们提出的HDAC4在视杆细胞和视锥细胞中促进生存的研究将推进主要致盲性疾病的治疗范式。 公共卫生相关性：我们建议利用HDAC4(组蛋白脱乙酰酶4)的促生存作用来保护视网膜退行性疾病中的视网膜神经元，这些疾病会导致人类进行性视力丧失。了解HDAD4在视网膜中的作用机制可能会导致对中枢神经系统其他退行性疾病的新的治疗干预措施，如阿尔茨海默病、亨廷顿病和脊髓小脑性共济失调。

DESCRIPTION (provided by applicant): The leading cause of blindness in the United States is retinal degeneration, typically involving the death of photoreceptors (rods and cones). Retinitis pigmentosa (RP) refers to a major group of hereditary retinal degenerative diseases commonly caused by mutations in rod-specific genes. These genetic defects cause rods to die followed by gradual degeneration of normal cones. It is cone death that results in progressive vision loss in RP. RP affects over 100,000 people in the United States with no treatment or prevention currently available. Our long-term goal is to understand the mechanism of photoreceptor degeneration in RP and to develop therapies that save photoreceptors and restore visual function in RP patients. A major challenge to saving rods is the heterogeneous nature of RP, as many mutations have been identified in rod-specific genes; thus, each mutation may require a unique therapy. By contrast, saving cones may provide a more general means to save vision for RP. Our previous study demonstrated a novel role of HDAC4 in promoting rod survival in a mouse model of RP. We will expand our studies through the following Aims: Aim 1) we will investigate the molecular and cellular mechanisms through which HDAC4 protects photoreceptors in retinal degeneration mice. Using a cre-loxp system to restrict HDAC4 expression in specific cell types, we will test whether HDAC4 exerts its pro-survival effect in photoreceptors through a cell-autonomous mechanism versus HDAC4's effect in other cell types. We will further test whether the HDAC4 deacetylase domain is required for its effect in photoreceptor protection. Aim 2) we will test whether HDAC4 saves photoreceptors in both fast and slower retinal degeneration models. Using AAV (adeno-associated virus)-mediated gene transfer in rd1 mice (a fast retinal degeneration model), we will test whether HDAC4 directly promotes cone survival. We will test for preserved cone structure and critical components in cone phototransduction. Using AAV-mediated gene transfer in VPP and rd10 mice (slower retinal degeneration models), we will investigate 1) whether photoreceptor protection requires developmental expression of HDAC4; 2) whether HDAC4 can be used as a more general survival factor for photoreceptor protection. Aim 3) we will investigate major survival signaling pathways that are inactivated during retinal degeneration and reactivated in HDAC4-saved cones. We will further test whether HDAC4-saved cones restore visual function using: 1) electrophysiology to test the integrity of neural circuits in the retina and visual cortex; 2) behavioral tests to determine whether rescued retinal function can guide complex behaviors. In summary, our proposed studies will elucidate the molecular and cellular mechanisms and pathways through which HDAC4 promotes the survival of photoreceptors, the main target of genetic diseases in the retina. Our proposed research on the pro-survival effect of HDAC4 in both rods and cones will advance the therapeutic paradigm for a major group of blinding diseases. PUBLIC HEALTH RELEVANCE: We propose to utilize the pro-survival effect of HDAC4 (histone deacetylase 4) to protect retinal neurons in retinal degenerative diseases that cause progressive vision loss in humans. Understanding the mechanisms by which HDAD4 functions in the retina may lead to new therapeutic interventions for other degenerative diseases in the central nervous system, such as Alzheimer's disease, Huntington's disease, and spinocerebellar ataxia.