Molecular Genetics of Age-Dependent Retinal Degeneration

描述（由申请人提供）：我们的长期目标是了解与人类视网膜疾病和衰老相关的视网膜缺陷的分子机制。最近的研究表明，类似的突触异常和逐渐的光感受器细胞丢失在衰老和一些视网膜退行性疾病中普遍存在。在衰老和年龄依赖性视网膜退行性疾病中观察到的视网膜异常的相似性表明，这些疾病的分子机制之间存在联系。因此，阐明导致常见的年龄依赖性视网膜异常的分子机制，应该增强我们对年龄依赖性视网膜疾病和视网膜衰老的理解。我们发现了一种enu诱导的突变小鼠菌株FUN025，在视网膜中显示出年龄依赖性异常的早期发作。这些小鼠的表型模仿在正常老化视网膜中观察到的异常，但它们出现在更早的时间点。此外，我们发现FUN025小鼠的视网膜更容易受到氧化应激的影响，这表明FUN025基因参与保护光感受器细胞免受氧化应激的影响。根据FUN025突变的遗传定位，我们在跨膜蛋白135 （Tmem135）基因中发现了一个剪接位点突变，该突变位于FUN025最小区域。我们进一步确定TMEM135蛋白定位于光感受器细胞的线粒体和突触囊泡，其表达在正常老化的视网膜中减少。线粒体被认为是细胞氧化损伤的来源和目标，也是细胞凋亡的中介，是FUN025突变可能影响的细胞器。这些发现使我们得出了我们的假设，即FUN025在线粒体中起着保护光感受器细胞免受氧化应激的主要作用。在这个应用程序中，我们的主要重点是识别涉及年龄依赖性视网膜异常的基因，并表征这些分子。更具体地说，在Aim 1中，我们将测试Tmem135作为FUN025的强候选基因，并最终确定负责FUN025表型的基因。在Aim 2中，我们将研究FUN025在线粒体功能和细胞对氧化应激反应中的作用。此外，我们将测试FUN025基因的过表达是否能更好地保护感光细胞免受氧化应激的影响。在Aim 3中，我们将对另一个小鼠突变的相关基因进行定位克隆，该突变表现为年龄依赖性光感受器变性和突触异常，与FUN025小鼠观察到的相同。上述研究的完成将为年龄依赖性视网膜变性的分子机制提供多个切入点，并可能为预防与衰老和年龄依赖性视网膜疾病相关的视网膜疾病提供治疗策略。

DESCRIPTION (provided by applicant): Our long-term goal is to understand the molecular mechanisms causing retinal defects associated with human retinal diseases and aging. Recent studies have shown that similar synaptic abnormality and gradual photoreceptor cell loss are commonly observed in aging and a number of retinal degenerative diseases. The similarity of retinal abnormalities observed in aging and age-dependent retinal degenerative diseases suggests the link between molecular mechanisms underlying these conditions. Elucidating the molecular mechanisms causing the common age-dependent retinal abnormalities, therefore, should enhance our understanding of age-dependent retinal diseases and aging of the retina. We identified an ENU-induced mutant mouse strain, FUN025, showing early onset of age-dependent abnormalities in the retina. The phenotypes of these mice mimic abnormalities that are observed in normal aging retina, but they appear at the earlier time point. Furthermore, we found that the retina of FUN025 mice is more susceptible to oxidative stress, suggesting that the FUN025 gene is involved in protection of photoreceptor cells from oxidative stress. Following genetic mapping of the FUN025 mutation, we found a splice-site mutation in the transmembrane protein 135 (Tmem135) gene that is in the minimal FUN025 region. We further determined that the TMEM135 protein is localized to mitochondria as well as synaptic vesicles of photoreceptor cells, and its expression is reduced in the normal aging retina. Mitochondria are known as both the source and the target of oxidative damage in cells, as well as the mediator of apoptotic cell death, and are the likely organelle affected by the FUN025 mutation. These findings have led us to our hypothesis that FUN025 has a major role in the mitochondria to protect photoreceptor cells from oxidative stress. In this application, our major focus is to identify genes involved in age-dependent retinal abnormalities, and characterize those molecules. More specifically, in Aim 1, we will test Tmem135 as a strong candidate gene for FUN025, and definitively identify the gene responsible for FUN025 phenotypes. In Aim 2, we will study the role of FUN025 in the mitochondrial functions and cellular responses to oxdative stress. In addition, we will test whether overexpression of the FUN025 gene provides greater protection of photoreceptor cells from oxidative stress. In Aim 3, we will conduct positional cloning of the responsible gene for another mouse mutant showing age-dependent photoreceptor degeneration and synaptic abnormalities, that are identical to those observed in FUN025 mice. Completion of the proposed studies should provide multiple entry points into the molecular mechanisms underlying age-dependent retinal degeneration, and may offer therapeutic strategies for prevention of retinal conditions associated with aging and age-dependent retinal disorders.