Silencing mutant SOD1 in vivo for treatment of ALS

描述(由申请人提供)： 许多人类疾病是由显性的功能获得基因突变引起的。其中包括一些神经退行性疾病。一个公认的例子是肌萎缩侧索硬化症(ALS)，这是一种以中老年起病的致命神经退行性疾病。肌萎缩侧索硬化症是一种进行性疾病--发病后，患者的肌肉会逐渐变弱，最终变得瘫痪。瘫痪是由脊髓和运动皮质中运动神经元死亡的无情进展引起的。50%的患者在确诊后3年内死亡，90%的患者在5年内死亡。目前，还没有治愈的方法。90%的肌萎缩侧索硬化症病例是散发性的；10%是家族性的。大约25%的家族性ALS是由铜锌超氧化物歧化酶(SOD1)基因突变引起的。已发现100多种不同的突变导致肌萎缩侧索硬化症(www.alsod.org)。通过在不同的系统中表达致病突变体SOD1，大量的体外和体内模型已经压倒性地证明了突变体SOD1通过获得毒性性质而导致运动神经元变性。这些发现解释了为什么携带一个突变型和一个野生型SOD1副本的杂合子仍然会发展成ALS。对于由功能获得SOD1突变引起的ALS，理想的治疗方法是消除突变蛋白，同时保留SOD1野生型拷贝的表达。这可能是通过RNAi实现的，它能够指导RNA的序列特异性破坏。通过引入序列与SOD1mRNA同源的短发夹状RNA(ShRNA)，可以诱导针对突变型SOD1RNA的RNAi。我们建议测试一种RNAi治疗策略，即通过重组腺病毒将shRNA传递给表达突变SOD1的转基因小鼠的运动神经元。由于这些小鼠的ALS与人类相似，我们将观察这种治疗策略是否可以降低运动神经元中突变的SOD1水平，推迟疾病的发病，并延长这些小鼠的生存时间。如果成功，这些实验将为这一治疗策略的进一步人体试验提供动力。

DESCRIPTION (provided by applicant): Many human diseases are caused by dominant, gain-of-function gene mutations. Among these are some neurodegenerative diseases. A well established example is amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease with middle to old age onset. ALS is progressive disease-after onset, patients' muscles progressively weaken and eventually become paralyzed. Paralysis is caused by a relentless progression of motor neuron death in the spinal cord and motor cortex. Fifty percent of patients die in 3 years after diagnosis and 90% in 5 years. At present, there is no cure. Ninety percent of ALS cases are sporadic; ten percent are familial. Mutations in the Cu, Zn superoxide dismutase (SOD1) gene cause approximately 25% of familial ALS. More than 100 different mutations have been identified that cause ALS (www.alsod.org). By expressing the disease-causing mutant SOD1 in different systems, numerous in vitro and in vivo models have overwhelmingly demonstrated that mutant SOD1 causes motoneuron degeneration by a gain of toxic property. These findings explain why heterozygotes bearing one mutant and one wild-type copy of SOD1 nevertheless develop ALS. The ideal therapy for ALS caused by a gain-of-function SOD1 mutation would be to eliminate the mutant protein while retaining expression of the wild-type copy of SOD1. This may be achieved by RNAi, which is capable of directing sequence-specific destruction of RNA. RNAi against mutant SOD1 can be induced by introducing short hairpin RNA (shRNA) with sequences homologous to SOD1 mRNA. We propose to test an RNAi therapy strategy, in which the shRNA is delivered to motor neurons in transgenic mice that express mutant SOD1 by recombinant adenovirus. Because these mice develop ALS similar to humans, we will observe whether this therapeutic strategy can lower mutant SOD1 levels in motor neurons, delay disease onset and prolong the survival of these mice. If successful, these experiments will provide impetus for further human trials of this therapeutic strategy.