Production of sporadic ALS model mice by targeting the ADAR2 gene in motor neurons

我们最近证明，Q/R位点的GluR 2，AMPA受体的亚基，RNA编辑显着减少，在运动神经元的散发性，但不是家族性，ALS患者在疾病特异性和神经元类选择性的方式。GluR2 Q/R。位点编辑由作用于RNA 2型（ADAR 2）的腺苷脱氨酶特异性催化，并且由于该位点处RNA编辑的显著减少，全身性ADAR 2缺失小鼠死于癫痫持续状态。这种酶活性的降低可能是导致GluR 2 Q/R位点欠编辑和在散发性ALS运动神经元中观察到的神经元死亡的原因。为了研究ADAR 2缺陷是否是在散发性ALS中观察到的运动神经元缓慢死亡的原因，我们开发了遗传修饰小鼠，其中使用Cre-loxP系统在运动神经元中选择性敲除ADAR 2基因。我们研究了这些小鼠中ADAR 2缺陷神经元的运动功能、存活长度、神经元丢失的变化，这些突变小鼠的平均存活时间明显短于对照小鼠，并且表现出Cre表达依赖性的进行性运动选择性行为缺陷。缺乏ADAR 2的运动神经元经历缓慢的进行性死亡，而表达ADAR 2的运动神经元在小鼠生命期间保持完整。在死亡的ADAR 2缺陷型运动神经元中，GluR 2 Q/R位点的RNA编辑完全丢失。在这里，我们证明了ADAR 2基因敲除小鼠中，ADAR 2的缺失诱导了GluR 2 Q/R位点的未编辑，导致运动神经元缓慢进行性死亡。目前的结果可能表明，ADAR 2活性不足可能是散发性ALS中神经元死亡的原因。这种突变小鼠模型将有助于研究散发性ALS。

We recently demonstrated that Q/R site-RNA editing of GluR2, a subunit of AMPA receptors, is markedly decreased in motor neurons of sporadic, but not familial, ALS patients in a disease-specific and neuronal class-selective manner. GluR2 Q/R. site-editing is specifically catalyzed by adenosine deaminase acting on RNA type 2 (ADAR2) and systemic ADAR2-null mice die young from status epilepticus due to a marked reduction in RNA editing at this site. Reduction of this enzyme activity is likely the cause of GluR2 Q/R site-underediting and neuronal death observed in sporadic ALS motor neurons.To investigate whether deficient ADAR2 is a cause of slow death of motor neurons as seen in sporadic ALS, we developed genetically modified mice in that the ADAR2 gene is selectively knocked out in motor neurons using Cre-loxP system. We investigated the changes in motor function, survival length, neuronal loss of ADAR2-deficient neurons in these mice as compared to control mice.These mutant mice displayed significantly shorter mean survival than control mice and progressive motor-selective behavioral deficit in a Cre expression-dependent manner. Motor neurons deficient for ADAR2 underwent slowly progressive death, whereas ADAR2-expressing motor neurons remains intact during the mouse life. RNA editing at the GluR2 Q/R site was completely lost in dying, ADAR2-deficient motor neurons.Here we demonstrated that loss of ADAR2 induces GluR2 Q/R site-underediting with resultant slowly progressive death of motor neurons in the ADAR2 knockout mice. Present results likely indicate that ADAR2 under-activity may be a cause of neuronal death in sporadic ALS. This mutant mouse model would be useful in research into sporadic ALS.